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Sample records for 2 wet catalytic

  1. Catalytic wet peroxide oxidation of phenol solutions over CuO/CeO2 systems.

    PubMed

    Massa, Paola; Ivorra, Fernando; Haure, Patricia; Fenoglio, Rosa

    2011-06-15

    Three 5% CuO/CeO(2) catalysts were synthesized by sol-gel, precipitation and combustion methods, followed by incipient wetness impregnation with copper nitrate. The samples were characterized by XRD, TPR, BET and tested for the catalytic wet peroxide oxidation of a phenol solution (5 g/L). The reaction took place in a batch reactor at atmospheric pressure, in a temperature range of 60-80°C, during 4h. Phenol conversion, H(2)O(2) consumption, pH and chemical oxygen demand were determined. The reaction temperature and the catalyst loading did improve the phenol and the H(2)O(2) conversions. The effect on the selectivity towards complete mineralization was less marked, with levels among 60-70%. Stepwise addition of H(2)O(2) was also tested.

  2. Catalytic wet air oxidation of 2-chlorophenol over sewage sludge-derived carbon-based catalysts.

    PubMed

    Tu, Yuting; Xiong, Ya; Tian, Shuanghong; Kong, Lingjun; Descorme, Claude

    2014-07-15

    A sewage sludge derived carbon-supported iron oxide catalyst (FeSC) was prepared and used in the Catalytic Wet Air Oxidation (CWAO) of 2-chlorophenol (2-CP). The catalysts were characterized in terms of elemental composition, surface area, pHPZC, XRD and SEM. The performances of the FeSC catalyst in the CWAO of 2-CP was assessed in a batch reactor operated at 120°C under 0.9MPa oxygen partial pressure. Complete decomposition of 2-CP was achieved within 5h and 90% Total Organic Carbon (TOC) was removed after 24h of reaction. Quite a straight correlation was observed between the 2-CP conversion, the amount of iron leached in solution and the pH of the reaction mixture at a given reaction time, indicating a strong predominance of the homogeneous catalysis contribution. The iron leaching could be efficiently prevented when the pH of the solution was maintained at values higher than 4.5, while the catalytic activity was only slightly reduced. Upon four successive batch CWAO experiments, using the same FeSC catalyst recovered by filtration after pH adjustment, only a very minor catalyst deactivation was observed. Finally, based on all the identified intermediates, a simplified reaction pathway was proposed for the CWAO of 2-CP over the FeSC catalyst.

  3. [Research on synergy of combining electrochemical oxidation and catalytic wet oxidation].

    PubMed

    Wang, Hua; Li, Guang-Ming; Zhang, Fang; Huang, Ju-Wen

    2009-07-15

    A new catalytic wet oxidation fixed-bed reactor combined with three-dimensional electric-field was developed to investigate catalytic wet oxidation, electrochemical oxidation and electroassisted catalytic wet oxidation of the solution containing phenol in the presence of a catalyst Mn-Sn-Sb-3/gamma-Al2O3. Good electroassisted catalytic wet oxidation efficiency was obtained in the setup for the combination system even at mild conditions (T = 130 degrees C, po2 = 1.0 MPa) that the phenol conversion and TOC reduction were up to 94.0% and 88.4% after 27 min treatment, respectively. The result also shows that the rate constants of electroassisted catalytic wet oxidation are much higher than that of not only both catalytic wet oxidation and electrochemical oxidation process alone but also additive efficiencies of catalytic wet oxidation and electrochemical oxidation processes, which indicates an apparent synergetic effect between CWO and ECO processes.

  4. Al 2O 3 supported Ru catalysts prepared by thermolysis of Ru 3(CO) 12 for catalytic wet air oxidation

    NASA Astrophysics Data System (ADS)

    Yu, Chaoying; Zhao, Peiqing; Chen, Gexin; Hu, Bin

    2011-06-01

    Low loading catalysts Ru/γ-Al 2O 3 and Ru-Ce/γ-Al 2O 3 were prepared by thermolysis of Ru 3(CO) 12 on γ-Al 2O 3. The catalysts were characterized by XPS, XRD and SEM. Two new Ru species (Ru A and Ru B) were detected during the Ru 3(CO) 12 decomposition process due to chemical interaction with the active OH groups on the surface of Al 2O 3 support, and the reduction of them can lead to more dispersed metallic phases. The sample was completely decomposed at 673 K in H 2, and RuO 2 was formed with minor amounts of Ru 0. When the temperature was increased to 773 K to heat the sample, the ratio of Ru 0 to RuO 2 increased. However, after the addition of CeO 2, only RuO 2 was detected on surface. The catalysts exhibited high activities in Catalytic Wet Air Oxidation (CWAO) of different organic compounds at high concentration such as isopropyl alcohol, phenol, acetic acids and N,N-dimethylformamide, which is attributed to the better dispersion of Ru particles and the addition of CeO 2 further enhanced number of effectively active sites on the cluster-derived catalyst surface.

  5. Effect of CeO2 doping on catalytic activity of Fe2O3/gamma-Al2O(3) catalyst for catalytic wet peroxide oxidation of azo dyes.

    PubMed

    Liu, Yan; Sun, Dezhi

    2007-05-08

    In order to find a catalyst with high activity and stability for catalytic wet peroxide oxidation (CWPO) process under normal condition, with Fe(2)O(3)/gamma-Al(2)O(3) and Fe(2)O(3)-CeO(2)/gamma-Al(2)O(3) catalysts prepared by impregnation method, the effect of CeO(2) doping on the structure and catalytic activity of Fe(2)O(3)/gamma-Al(2)O(3) for catalytic wet peroxide oxidation of azo dyes at 25 degrees C and atmospheric pressure is evaluated using BET, SEM, XRF, XRD, XPS and chemical analysis techniques, and test results show that, better dispersion and smaller size of Fe(2)O(3) crystal can be achieved by adding CeO(2), and the content of chemisorbed oxygen can also be increased on the surface of catalyst. CWPO experimental results indicate that azo dyes in simulated wastewater can be efficiently mineralized and the catalytic activity of Fe(2)O(3)-CeO(2)/gamma-Al(2)O(3) can be increased by about 10% compared with that of Fe(2)O(3)/gamma-Al(2)O(3) because of the promotion of the structural and redox properties of the ferric oxide by ceria doped. Leaching tests indicate that Fe(2)O(3)/gamma-Al(2)O(3) and Fe(2)O(3)-CeO(2)/gamma-Al(2)O(3) are stable with a negligible amount of irons found in the aqueous solution after reaction for 2h. It can therefore be concluded from results and discussion that in comparison with Fe(2)O(3)/gamma-Al(2)O(3), Fe(2)O(3)-CeO(2)/gamma-Al(2)O(3) is a suitable catalyst, which can effectively degrade contaminants at normal temperature and atmospheric pressure.

  6. Treatment of aniline by catalytic wet air oxidation: comparative study over CuO/CeO2 and NiO/Al2O3.

    PubMed

    Ersöz, Gülin; Atalay, Süheyda

    2012-12-30

    The treatment of aniline by catalytic wet air oxidation (CWAO) was studied in a bubble reactor. The experiments were performed to investigate the effects of catalyst loading, temperature, reaction time, air flow rate, and pressure on aniline removal. The catalytic effects of the prepared nanostructured catalysts, CuO/CeO(2) (10% wt) and NiO/Al(2)O(3) (10% wt), on the CWAO treatment efficiency were also examined and compared. The prepared catalysts seem to be active having an aniline removal of 45.7% with CuO/CeO(2) and 41.9% with NiO/Al(2)O(3). The amount of N(2) formed was approximately the same for both of the catalysts.

  7. Characteristics of CuO-MoO3-P2O5 catalyst and its catalytic wet oxidation (CWO) of dye wastewater under extremely mild conditions.

    PubMed

    Ma, Hongzhu; Zhuo, Qiongfang; Wang, Bo

    2007-11-01

    In order to develop a catalyst with high activity for catalytic wet oxidation (CWO) processing at lower temperatures (35 degrees C) and atmospheric pressure, a new CuO-MoO3-P2O5 catalystwas synthesized by a solid-state reaction method and was characterized by X-ray diffraction (XRD), Fourier transformation infrared spectrometer (FTIR), X-ray photoelectron spectroscopy (XPS), selected area electronic diffraction (SAED), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDXS) for elemental mapping. Methylene blue (MB) was adopted to investigate the catalytic activity of CuO-MoO3-P2O5 in CWO processing. The results show that this new catalyst has a high catalytic activity to decolorize MB under mild condition. The color removal of MB (the initial concentration was 0.3 g L(-1) and initial pH was 5) can reach to 99.26% within 10 min at 35 degrees C and atmospheric pressure. Catalyst lifespan and selectivity were also tested, and the results show that after the catalyst was used three times, catalyst activity still remains. Selectivity testing shows that CuO-MoO3-P2O5 has high catalytic activity on degradation of MB, whereas this catalyst has less impact on methyl orange (the color removal was 99.65% for MB and 55% for methyl orange under the same conditions). According to the experimental results, a possible mechanism of catalytic degradation of MB was proposed.

  8. [Catalytic wet air oxidation of phenol with Ru/ZrO2-CeO2 catalyst].

    PubMed

    Wang, Jian-bing; Zhu, Wan-peng; Wang, Wei; Yang, Shao-xia

    2007-07-01

    Wet air oxidation of phenol with Ru/ZrO2-CeO2 was systematically investigated and results showed that Ru/ZrO2-CeO2 could significantly increase the removal of COD and phenol. At the reaction temperature of 170 degrees C and pressure of 3MPa, about 99% COD and 100% phenol was removed respectively after 120 min. The optimal conditions were: reaction temperature, 170 degrees C; reaction pressure, 3 MPa; catalyst dosage, 5 g/L; agitator speed, 500 r/min. By analyzing intermediates, a simplified scheme of phenol oxidation was brought out. It includes two main steps. The first step is the production of organic acids, which is fast. The second step is the oxidation of organic acid, in which the oxidation of acetic acid is slow. Complete oxidation of acetic acid needs high temperature at which the radicals assault the C-H bond of a carbon and acetic acid is oxidized into carbon dioxide and water through formic acid.

  9. Removal of ammonia solutions used in catalytic wet oxidation processes.

    PubMed

    Hung, Chang Mao; Lou, Jie Chung; Lin, Chia Hua

    2003-08-01

    Ammonia (NH(3)) is an important product used in the chemical industry, and is common place in industrial wastewater. Industrial wastewater containing ammonia is generally either toxic or has concentrations or temperatures such that direct biological treatment is unfeasible. This investigation used aqueous solutions containing more of ammonia for catalytic liquid-phase oxidation in a trickle-bed reactor (TBR) based on Cu/La/Ce composite catalysts, prepared by co-precipitation of Cu(NO(3))(2), La(NO(3))(2), and Ce(NO(3))(3) at 7:2:1 molar concentrations. The experimental results indicated that the ammonia conversion of the wet oxidation in the presence of the Cu/La/Ce composite catalysts was determined by the Cu/La/Ce catalyst. Minimal ammonia was removed from the solution by the wet oxidation in the absence of any catalyst, while approximately 91% ammonia removal was achieved by wet oxidation over the Cu/La/Ce catalyst at 230 degrees C with oxygen partial pressure of 2.0 MPa. Furthermore, the effluent streams were conducted at a liquid hourly space velocity of under 9 h(-1) in the wet catalytic processes, and a reaction pathway was found linking the oxidizing ammonia to nitric oxide, nitrogen and water. The solution contained by-products, including nitrates and nitrites. Nitrite selectivity was minimized and ammonia removal maximized when the feed ammonia solution had a pH of around 12.0.

  10. Catalytic wet oxidation of 2,4-dichlorophenol solutions: activity of the manganese-cerium composite catalyst and biodegradability of the effluent stream.

    PubMed

    Lee, Bing-Nan; Lou, Jie-Chung; Yen, Po-Chung

    2002-01-01

    Aqueous solutions containing 100 to 1000 mg/L of 2,4-dichlorophenol (2,4-DCP) were oxidized in an upflowing fixed-bed reactor in this study of manganese-cerium composite catalysts, which were prepared by the coprecipitation of both manganese nitrate and ceric nitrate at various molar concentrations. Results showed that 2,4-DCP conversion by wet oxidation in the presence of the manganese-cerium composite catalysts was a function of the molar ratio of the manganese-cerium catalyst. The kinetic behavior of 2,4-DCP oxidation with catalysis could be explained by using a zero-order rate expression. Total organic carbon (TOC) removal by wet oxidation in the absence of any catalyst was nil, while approximately 68% TOC reduction was achieved during wet oxidation over a manganese-cerium (7:3 mol/mol) catalyst at 160 degrees C and an oxygen partial pressure of 1.0 MPa. Moreover, the 5-day biochemical oxygen demand/chemical oxygen demand ratios of all the effluent streams were determined to be greater than 0.45 as the wet catalytic processes were carried out at a liquid hourly space velocity less than 24 h (-1), indicating that they could be made more amenable to further biological treatment.

  11. Catalytic properties of carbon materials for wet oxidation of aniline.

    PubMed

    Gomes, Helder T; Machado, Bruno F; Ribeiro, Andreia; Moreira, Ivo; Rosário, Márcio; Silva, Adrián M T; Figueiredo, José L; Faria, Joaquim L

    2008-11-30

    A mesoporous carbon xerogel with a significant amount of oxygen functional groups and a commercial activated carbon, were tested in the catalytic wet air oxidation of aniline at 200 degrees C and 6.9 bar of oxygen partial pressure. Both carbon materials showed high activity in aniline and total organic carbon removal, a clear increase in the removal efficiency relatively to non-catalytic wet air oxidation being observed. The best results in terms of aniline removal were obtained with carbon xerogel, an almost complete aniline conversion after 1h oxidation with high selectivity to non-organic compounds being achieved. The materials were characterized by thermogravimetric analysis, temperature programmed desorption, N(2) adsorption and scanning electron microscopy, in order to relate their performances to the chemical and textural characteristics. It was concluded that the removal efficiency, attributed to both adsorption and catalytic activity, is related to the mesoporous character of the materials and to the presence of specific oxygen containing functional groups at their surface. The effect of catalytic activity was found to be more important in the removal of aniline than the effect of adsorption at the materials surface. The results obtained indicate that mesoporous carbon xerogels are promising catalysts for CWAO processes.

  12. Catalytic wet air oxidation of phenol over CeO2-TiO2 catalyst in the batch reactor and the packed-bed reactor.

    PubMed

    Yang, Shaoxia; Zhu, Wanpeng; Wang, Jianbing; Chen, Zhengxiong

    2008-05-30

    CeO2-TiO2 catalysts are prepared by coprecipitation method, and the activity and stability in the catalytic wet air oxidation (CWAO) of phenol are investigated in a batch reactor and packed-bed reactor. CeO2-TiO2 mixed oxides show the higher activity than pure CeO2 and TiO2, and CeO2-TiO2 1/1 catalyst displays the highest activity in the CWAO of phenol. In a batch reactor, COD and TOC removals are about 100% and 77% after 120 min in the CWAO of phenol over CeO2-TiO2 1/1 catalyst at reaction temperature of 150 degrees C, the total pressure of 3 MPa, phenol concentration of 1000 mg/L, and catalyst dosage of 4 g/L. In a packed-bed reactor using CeO2-TiO2 1/1 particle catalyst, over 91% COD and 80% TOC removals are obtained at the reaction temperature of 140 degrees C, the air total pressure of 3.5 MPa, the phenol concentration of 1000 mg/L for 100 h continue reaction. Leaching of metal ions of CeO2-TiO2 1/1 particle catalyst is very low during the continuous reaction. CeO2-TiO2 1/1 catalyst exhibits the excellent activity and stability in the CWAO of phenol.

  13. Optimizing chemical oxygen demand removal from synthesized wastewater containing lignin by catalytic wet-air oxidation over CuO/Al2O3 catalysts.

    PubMed

    Sriprom, Pongsert; Neramittagapong, Sutasinee; Lin, Chitsan; Wantala, Kitirote; Neramittagapong, Arthit; Grisdanurak, Nurak

    2015-07-01

    In this study, 10% CuO/Al2O3 catalyst was used in a catalytic wet-air oxidation process to remove chemical oxygen demand (COD) and color from experimentally designed wastewater containing lignin. The catalyst was prepared using an impregnation method and was characterized by X-ray diffraction (XRD), atomic absorption spectroscopy (AAS), and Brunauer-Emmett-Teller method (BET) for surface area before use. A series of Box-Behnken design (BBD) experiments were used to identify the conditions (temperature, pressure, reaction time, and catalysts) necessary for the COD removal process. The predicted model had R2 and R2adj correlation coefficients of 0.98 and 0.97, respectively. Pressure only and the interaction effect between temperature and pressure were found to have a significant effect on COD removal (both confidence interval [CI] 95%). Finally, response surface methodology (RSM)-optimized results suggested that 92% of COD could be removed in 1 L of experimental wastewater with a lignin concentration 350 g/L in 120 min under the following conditions: a reaction temperature of 185 °C, a pressure of 10 bars, and catalyst loading of 1 mg/L. The experiment, performed in triplicate, yielded a COD removal of 90±2%. The results are believed to be of importance to pulp and paper industrial wastewater treatment and other similar applications. Catalytic wet-air oxidation (CWAO) has been used as an alternative to overcome problems related to the high temperatures and pressures required by the traditional wet-air oxidation. CWAO has been widely applied to treat various industrial wastewaters. To reduce the overall operational cost, it is necessary to identify the optimal condition required when designing wastewater treatment plant processes. In this work, the authors had successfully demonstrated the application of response surface methodology (RSM) with the Box-Behnken design (BBD) as a means of elucidating the complicated interaction effects between parameters.

  14. Catalytic wet hydrogen peroxide oxidation of a petrochemical wastewater.

    PubMed

    Pariente, M I; Melero, J A; Martínez, F; Botas, J A; Gallego, A I

    2010-01-01

    Continuous Catalytic Wet Hydrogen Peroxide Oxidation (CWHPO) for the treatment of a petrochemical industry wastewater has been studied on a pilot plant scale process. The installation, based on a catalytic fixed bed reactor (FBR) coupled with a stirred tank reactor (STR), shows an interesting alternative for the intensification of a continuous CWHPO treatment. Agglomerated SBA-15 silica-supported iron oxide (Fe(2)O(3)/SBA-15) was used as Fenton-like catalyst. Several variables such as the temperature and hydrogen peroxide concentration, as well as the capacity of the pilot plant for the treatment of inlet polluted streams with different dilution degrees were studied. Remarkable results in terms of TOC reduction and increased biodegradability were achieved using 160 degrees C and moderate hydrogen peroxide initial concentration. Additionally, a good stability of the catalyst was evidenced for 8 hours of treatment with low iron leaching (less than 1 mg/L) under the best operating conditions.

  15. Post-treatment of biologically treated wastewater containing organic contaminants using a sequence of H2O2 based advanced oxidation processes: photolysis and catalytic wet oxidation.

    PubMed

    Rueda-Márquez, J J; Sillanpää, M; Pocostales, P; Acevedo, A; Manzano, M A

    2015-03-15

    In this paper the feasibility of a multi-barrier treatment (MBT) for the regeneration of synthetic industrial wastewater (SIWW) was evaluated. Industrial pollutants (orange II, phenol, 4-chlorophenol and phenanthrene) were added to the effluent of municipal wastewater treatment plant. The proposed MBT begins with a microfiltration membrane pretreatment (MF), followed by hydrogen peroxide photolysis (H2O2/UVC) and finishing, as a polishing step, with catalytic wet peroxide oxidation (CWPO) using granular activated carbon (GAC) at ambient conditions. During the microfiltration step (0.7 μm) the decrease of suspended solids concentration, turbidity and Escherichia coli in treated water were 88, 94 and 99%, respectively. Also, the effluent's transmittance (254 nm) was increased by 14.7%. Removal of more than 99.9% of all added pollutants, mineralization of 63% of organic compounds and complete disinfection of total coliforms were reached during the H2O2/UVC treatment step (H2O2:TOC w/w ratio = 5 and an UVC average dose accumulated by wastewater 8.80 WUVC s cm(-2)). The power and efficiency of the lamp, the water transmittance and photoreactor geometry are taken into account and a new equation to estimate the accumulated dose in water is suggested. Remaining organic pollutants with a higher oxidation state of carbon atoms (+0.47) and toxic concentration of residual H2O2 were present in the effluent of the H2O2/UVC process. After 2.3 min of contact time with GAC at CWPO step, 90 and 100% of total organic carbon and residual H2O2 were removed, respectively. Also, the wastewater toxicity was studied using Vibrio fischeri and Sparus aurata larvae. The MBT operational and maintenance costs (O&M) was estimated to be 0.59 € m(-3).

  16. Degradation process analysis of the azo dyes by catalytic wet air oxidation with catalyst CuO/γ-Al2O3.

    PubMed

    Hua, Li; Ma, Hongrui; Zhang, Lei

    2013-01-01

    Three azo dyes (Methyl Orange, Direct Brown and Direct Green) were treated by catalytic wet air oxidation (CWAO) with the catalysts CuO/γ-Al(2)O(3) prepared by consecutive impregnation. The relationship of decolorization extent, chemical oxygen demand (COD) removal extent and total organic carbon (TOC) in dye solution were investigated. The results indicated that the CuO/γ-Al(2)O(3) catalyst had excellent catalytic activity in treating azo dyes. Almost 99% of color and 70% of TOC were removed in 2h. The high removal extent of color and TOC indicated that the CWAO obtained perfect decomposition for pollutants. The degradation pathway of azo dyes was analyzed by UV-Vis, FTIR and MS. According to the examined results, the hydroxyl ((·)OH) radicals induced strong oxidizing effects in the target solution and destroyed the chromophoric groups of azo-benzene conjugated of the molecular structure. Considering characteristics of the dye structure, the azo bond (-N=N-) would first be attacked by the hydroxyl radical and other free radicals. With the continuous oxidization and the long reaction time at high temperature, these intermediates could be oxidized to the final oxidation products, such as water and carbon dioxide.

  17. Abatement of phenolic mixtures by catalytic wet oxidation enhanced by Fenton's pretreatment: effect of H2O2 dosage and temperature.

    PubMed

    Santos, A; Yustos, P; Rodriguez, S; Simon, E; Garcia-Ochoa, F

    2007-07-31

    Catalytic wet oxidation (CWO) of a phenolic mixture containing phenol, o-cresol and p-cresol (500mg/L on each pollutant) has been carried out using a commercial activated carbon (AC) as catalyst, placed in a continuous three-phase reactor. Total pressure was 16 bar and temperature was 127 degrees C. Pollutant conversion, mineralization, intermediate distribution, and toxicity were measured at the reactor outlet. Under these conditions no detoxification of the inlet effluent was found even at the highest catalyst weight (W) to liquid flow rate (Q(L)) ratio used. On the other hand, some Fenton Runs (FR) have been carried out in a batch way using the same phenolic aqueous mixture previously cited. The concentration of Fe(2+) was set to 10mg/L. The influence of the H(2)O(2) amount (between 10 and 100% of the stoichiometric dose) and temperature (30, 50, and 70 degrees C) on phenols conversion, mineralization, and detoxification have been analyzed. Phenols conversion was near unity at low hydrogen peroxide dosage but mineralization and detoxification achieved an asymptotic value at each temperature conditions. The integration of Fenton reagent as pretreatment of the CWO process remarkably improves the efficiency of the CWO reactor and allows to obtain detoxified effluents at mild temperature conditions and relatively low W/Q(L) values. For a given phenolic mixture a temperature range of 30-50 degrees C in the Fenton pretreatment with a H(2)O(2) dosage between 20 and 40% of the stoichiometric amount required can be proposed.

  18. Catalytic wet air oxidation of chlorophenols over supported ruthenium catalysts.

    PubMed

    Li, Ning; Descorme, Claude; Besson, Michèle

    2007-07-31

    A series of noble metal (Pt, Pd, Ru) loaded zirconia catalysts were evaluated in the catalytic wet air oxidation (CWAO) of mono-chlorophenols (2-CP, 3-CP, 4-CP) under relatively mild reaction conditions. Among the investigated noble metals, Ru appeared to be the best to promote the CWAO of CPs as far as incipient-wetness impregnation was used to prepare all the catalysts. The position of the chlorine substitution on the aromatic ring was also shown to have a significant effect on the CP reactivity in the CWAO over 3wt.% Ru/ZrO(2). 2-CP was relatively easier to degradate compared to 3-CP and 4-CP. One reason could be the higher adsorption of 2-CP on the catalyst surface. Further investigations suggested that 3wt.% Ru/ZrO(2) is a very efficient catalyst in the CWAO of 2-CP as far as high 2-CP conversion and TOC abatement could still be reached at even lower temperature (393K) and lower total pressure (3MPa). Additionally, the conversion of 2-CP was demonstrated to increase with the initial pH of the 2-CP solution. The dechlorination reaction is promoted at higher pH. In all cases, the adsorption of the reactants and the reaction intermediates was shown to play a major role. All parameters that would control the molecule speciation in solution or the catalyst surface properties would have a key effect.

  19. Wet peroxide oxidation and catalytic wet oxidation of stripped sour water produced during oil shale refining.

    PubMed

    Prasad, Jaidev; Tardio, James; Jani, Harit; Bhargava, Suresh K; Akolekar, Deepak B; Grocott, Stephen C

    2007-07-31

    Catalytic wet oxidation (CWO) and wet peroxide oxidation (WPO) of stripped sour water (SSW) from an oil shale refinery was investigated. Greater than 70% total organic carbon (TOC) removal from SSW was achieved using Cu(NO(3))(2) catalysed WO under the following conditions using a glass lined reaction vessel: 200 degrees C, pO(2)=0.5MPa, 3h, [Cu(NO(3))(2)]=67mmol/L. Significant TOC removal ( approximately 31%) also occurred in the system without added oxygen. It is proposed that this is predominantly due to copper catalysed oxidative decarboxylation of organics in SSW based on observed changes in copper oxidation state. Greater than 80% TOC removal was achieved using WPO under the following conditions: 150 degrees C, t=1.5h, [H(2)O(2)]=64g/L. Significantly more TOC could be removed from SSW by adding H(2)O(2) in small doses as opposed to adding the same total amount in one single dose. It was concluded that WPO was a far more effective process for removing odorous compounds from SSW.

  20. Catalytic and non-catalytic wet air oxidation of sodium dodecylbenzene sulfonate: kinetics and biodegradability enhancement.

    PubMed

    Suárez-Ojeda, María Eugenia; Kim, Jungkwon; Carrera, Julián; Metcalfe, Ian S; Font, Josep

    2007-06-18

    Wet air oxidation (WAO) and catalytic wet air oxidation (CWAO) were investigated as suitable precursors for the biological treatment of industrial wastewater containing sodium dodecylbenzene sulfonate (DBS). Two hours WAO semi-batch experiments were conducted at 15 bar of oxygen partial pressure (P(O2)) and at 180, 200 and 220 degrees C. It was found that the highest temperature provides appreciable total organic carbon (TOC) and chemical oxygen demand (COD) abatement of about 42 and 47%, correspondingly. Based on the main identified intermediates (acetic acid and sulfobenzoic acid) a reaction pathway for DBS and a kinetic model in WAO were proposed. In the case of CWAO experiments, seventy-two hours tests were done in a fixed bed reactor in continuous trickle flow regime, using a commercial activated carbon (AC) as catalyst. The temperature and P(O2) were 140-160 degrees C and 2-9 bar, respectively. The influence of the operating conditions on the DBS oxidation, the occurrence of oxidative coupling reactions over the AC, and the catalytic activity (in terms of substrate removal) were established. The results show that the AC without any supported active metal behaves bi-functional as adsorbent and catalyst, giving TOC conversions up to 52% at 160 degrees C and 2 bar of P(O2), which were comparable to those obtained in WAO experiments. Respirometric tests were completed before and after CWAO and to the main intermediates identified through the WAO and CWAO oxidation route. Then, the readily biodegradable COD (COD(RB)) of the CWAO and WAO effluents were found. Taking into account these results it was possible to compare whether or not the CWAO or WAO effluents were suitable for a conventional activated sludge plant inoculated with non adapted culture.

  1. Wet air oxidation and catalytic wet air oxidation for dyes degradation.

    PubMed

    Ovejero, Gabriel; Sotelo, José Luis; Rodríguez, Araceli; Vallet, Ana; García, Juan

    2011-11-01

    Textile industry produces wastewater which contributes to water pollution since it utilizes a lot of chemicals. Preliminary studies show that the wastewater from textile industries contains grease, wax, surfactant, and dyes. The objective of this study was to determine the treatment efficiency of the nickel catalysts supported on hydrotalcites in three-dye model compounds and two types of wastewater. Hydrotalcites were employed to prepare supported nickel catalysts by wetness impregnation technique. Metal loadings from 1 to 10 wt% were tested. Catalysts were characterized by several techniques. They were tested in a catalytic wet air oxidation of three dyes and two wastewaters with different origins. It could be observed that the higher the metal content, the lower the BET area, possibly due to sintering of Ni and the consequent blocking of the pores by the metal. In addition, metallic dispersion was also higher when the metal content was lower. Dye conversion was more than 95% for every catalyst showing no differences with the nickel content. A high degree of dye conversion was achieved. Wet air oxidation (WAO) and catalytic wet air oxidation (CWAO) processes have been proved to be extremely efficient in TOC removal for wastewaters. The CWAO process can be used to remove dyes from wastewater. Three different dyes were tested showing satisfactory results in all of them. TOC degradation and dye removal in the presence of the catalyst were effective. Also, the HTNi catalyst is very active for organic matter and toxicity removal in wastewaters.

  2. [Degradation of beta-naphthol by catalytic wet air oxidation].

    PubMed

    Liu, Jie; Yu, Chao-Ying; Zhao, Pei-Qing; Chen, Ge-Xin

    2012-11-01

    A series of MnO(x)/nano-TiO2 catalysts were prepared and their application in degradation of beta-naphthol by catalytic wet air oxidation (CWAO) was investigated. The catalysts preparation conditions, reaction conditions and its stability were tested. The catalysts had been characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction (TPR) measurements. The results showed that the decrease of the COD removal for the degradation of beta-naphthol at high Mn loading was due to the aggregation of the highly dispersed Mn species and the formation of the correlated crystals. The decline of the COD removal at high calcination temperature was probably attributed to the weak electron transfer between Mn2O3 and MnO2 and the formation of the inactive Mn2O3. The COD removal had been falling slightly when the catalyst was used 6 times, and this was likely related to the decrease of the diffraction peaks. The catalyst had a high activity when the Mn loading (mass fraction) was 4% and the calcination temperature was 450 degrees C. The COD removal was up to 96.4% at 110 degrees C and 0.5 MPa with this catalyst. The COD removal of 92.4% could be obtained with the MnO(x)/nano-TiO2 catalyst was recycled 6 times. The Mn leaching at 50, 80, 110 and 150 degrees C were all less than 9.3 mg x L(-1) by means of Atomic Absorption Spectroscopy (AAS). The probable degradation pathway was proposed according to some publications.

  3. Catalytic wet air oxidation of high concentration pharmaceutical wastewater.

    PubMed

    Zhan, Wei; Wang, Xiaocong; Li, Daosheng; Ren, Yongzheng; Liu, Dongqi; Kang, Jianxiong

    2013-01-01

    In this study, we investigated the pretreatment of a high concentration pharmaceutical wastewater by catalytic wet air oxidation (CWAO) process. Different experiments were conducted to investigate the effects of the catalyst type, operating temperature, initial system pH, and oxygen partial pressure on the oxidation of the wastewater. Results show that the catalysts prepared by the co-precipitation method have better catalytic activity compared to others. Chemical oxygen demand (COD) conversion increased with the increase in temperature from 160 to 220 °C and decreased with the increase in pH. Moreover, the effect of the oxygen partial pressure on the COD conversion was significant only during the first 20 min of the reaction. Furthermore, the biodegradability of the wastewater improved greatly after CWAO, the ratio of BOD5/COD increased less than 0.1-0.75 when treated at 220 °C (BOD: biochemical oxygen demand).

  4. Process of forming catalytic surfaces for wet oxidation reactions

    NASA Technical Reports Server (NTRS)

    Jagow, R. B. (Inventor)

    1977-01-01

    A wet oxidation process was developed for oxidizing waste materials, comprising dissolved ruthenium salt in a reactant feed stream containing the waste materials. The feed stream is introduced into a reactor, and the reactor contents are then raised to an elevated temperature to effect deposition of a catalytic surface of ruthenium black on the interior walls of the reactor. The feed stream is then maintained in the reactor for a period of time sufficient to effect at least partial oxidation of the waste materials.

  5. CuO impregnated activated carbon for catalytic wet peroxide oxidation of phenol.

    PubMed

    Liou, Rey-May; Chen, Shih-Hsiung

    2009-12-15

    This paper presents an original approach to the removal of phenol in synthetic wastewater by catalytic wet peroxide oxidation with copper binding activated carbon (CuAC) catalysts. The characteristics and oxidation performance of CuAC in the wet hydrogen peroxide catalytic oxidation of phenol were studied in a batch reactor at 80 degrees C. Complete conversion of the oxidant, hydrogen peroxide, was observed with CuAC catalyst in 20 min oxidation, and a highly efficient phenol removal and chemical oxygen demand (COD) abatement were achieved in the first 30 min. The good oxidation performance of CuAC catalyst was contributed to the activity enhancement of copper oxide, which was binding in the carbon matrix. It can be concluded that the efficiency of oxidation dominated by the residual H2O2 in this study. An over 90% COD removal was achieved by using the multiple-step addition in this catalytic oxidation.

  6. Evolution of toxicity upon wet catalytic oxidation of phenol.

    PubMed

    Santos, A; Yustos, P; Quintanilla, A; García-Ochoa, F; Casas, J A; Rodríguez, J J

    2004-01-01

    This work reports on the evolution of the toxicity of phenol-containing simulated wastewater upon catalytic wet oxidation with a commercial copper-based catalyst (Engelhard Cu-0203T). The results of the study show that this catalyst enhances detoxification, in addition to its effect on the oxidation rate. The EC50 values of the intermediates identified throughout the oxidation route of phenol have been determined and used to predict the evolution of toxicity upon oxidation. The predicted values have been compared with the ones measured directly from the aqueous solution during the oxidation process. To learn about the evolution of toxicity through out the routes of phenol oxidation, experiments have been performed with simulated wastewaters containing separately phenol, catechol, and hydroquinone as original pollutants. The significant increase of toxicity observed during the early stages of phenol oxidation is not directly related to the development of the brown color that derives mainly from catechol oxidation. This increase of toxicity is caused by the formation of hydroquinone and p-benzoquinone as intermediates, the former showing the highest toxicity. Furthermore, synergistic effects, giving rise to a significant increase of toxicity, have been observed. These effects derive from the interactions among copper leached from the catalyst and catechol, hydroquinone, and p-benzoquinone and demand that close attention be paid to this potential problem in catalytic wet oxidation.

  7. Catalytic gasification of wet biomass in supercritical water

    SciTech Connect

    Antal, M.J. Jr.; Matsumura, Yukihiko; Xu, Xiaodong

    1995-12-31

    Wet biomass (water hyacinth, banana trees, cattails, green algae, kelp, etc.) grows rapidly and abundantly around the world. As a biomass crop, aquatic species are particularly attractive because their cultivation does not compete with land-based agricultural activities designed to produce food for consumption or export. However, wet biomass is not regarded as a promising feed for conventional thermochemical conversion processes because the cost associated with drying it is too high. This research seeks to address this problem by employing water as the gasification medium. Prior work has shown that low concentrations of glucose (a model compound for whole biomass) can be completely gasified in supercritical water at 600{degrees}C and 34.5 Wa after a 30 s reaction time. Higher concentrations of glucose (up to 22% by weight in water) resulted in incomplete conversion under these conditions. The gas contained hydrogen, carbon dioxide, carbon monoxide, methane, ethane, propane, and traces of other hydrocarbons. The carbon monoxide and hydrocarbons are easily converted to hydrogen by commercial technology available in most refineries. This prior work utilized capillary tube reactors with no catalyst. A larger reactor system was fabricated and the heterogeneous catalytic gasification of glucose and wet biomass slurry of higher concentration was studied to attain higher conversions.

  8. Degradation of paracetamol by catalytic wet air oxidation and sequential adsorption - Catalytic wet air oxidation on activated carbons.

    PubMed

    Quesada-Peñate, I; Julcour-Lebigue, C; Jáuregui-Haza, U J; Wilhelm, A M; Delmas, H

    2012-06-30

    The concern about the fate of pharmaceutical products has raised owing to the increasing contamination of rivers, lakes and groundwater. The aim of this paper is to evaluate two different processes for paracetamol removal. The catalytic wet air oxidation (CWAO) of paracetamol on activated carbon was investigated both as a water treatment technique using an autoclave reactor and as a regenerative treatment of the carbon after adsorption in a sequential fixed bed process. Three activated carbons (ACs) from different source materials were used as catalysts: two microporous basic ACs (S23 and C1) and a meso- and micro-porous acidic one (L27). During the first CWAO experiment the adsorption capacity and catalytic performance of fresh S23 and C1 were higher than those of fresh L27 despite its higher surface area. This situation changed after AC reuse, as finally L27 gave the best results after five CWAO cycles. Respirometry tests with activated sludge revealed that in the studied conditions the use of CWAO enhanced the aerobic biodegradability of the effluent. In the ADOX process L27 also showed better oxidation performances and regeneration efficiency. This different ageing was examined through AC physico-chemical properties.

  9. Oxidation and mineralisation of substituted phenols by Fenton's reagent and catalytic wet oxidation.

    PubMed

    Santos, A; Rodriguez, S; Garcia-Ochoa, F; Yustos, P

    2007-01-01

    Catalytic abatement of solutions of 1,000 mg/L in phenol, ortho and para nitrophenol and ortho and para cresols was acomplished by using two catalytic systems. Fenton's reagent was used at 50 degrees C by adding 10 mg/L of ferrous cation and different dosages of H2O2. The mixture was reacting isothermically in a batch way during 3 hours. Catalytic wet oxidation (CWO) was carried out by using a commercial Activated Carbon, Industrial React FE01606A, CWO runs were carried out in a fixed bed reactor (FBR) with concurrent upflow. Temperature and oxygen pressure of the reactor were set to 160 degrees C and 16 bar, respectively. While phenols are quicky oxidised by the Fenton reagent higher mineralisation was obtained in the CWO process.

  10. Catalytic wet-oxidation of a mixed liquid waste: COD and AOX abatement.

    PubMed

    Goi, D; de Leitenburg, C; Trovarelli, A; Dolcetti, G

    2004-12-01

    A series of catalytic wet oxidation (CWO) reactions, at temperatures of 430-500 K and in a batch bench-top pressure vessel were carried out utilizing a strong wastewater composed of landfill leachate and heavily organic halogen polluted industrial wastewater. A CeO2-SiO2 mixed oxide catalyst with large surface area to assure optimal oxidation performance was prepared. The catalytic process was examined during batch reactions controlling Chemical Oxygen Demand (COD) and Adsorbable Organic Halogen (AOX) parameters, resulting AOX abatement to achieve better effect. Color and pH were also controlled during batch tests. A simple first order-two stage reaction behavior was supposed and verified with the considered parameters. Finally an OUR test was carried out to evaluate biodegradability changes of wastewater as a result of the catalytic reaction.

  11. Development of a catalytic system for gasification of wet biomass

    SciTech Connect

    Elliott, D.C.; Sealock, L.J.; Phelps, M.R.; Neuenschwander, G.G.; Hart, T.R.

    1993-12-31

    A gasification system is under development at Pacific Northwest Laboratory that can be used with high-moisture biomass feedstocks. The system operates at 350{degrees}C and 205 atm using a liquid water phase as the processing medium. Since a pressurized system is used, the wet biomass can be fed as a slurry to the reactor without drying. Through the development of catalysts, a useful processing system has been produced. This paper includes assessment of processing test results of different catalysts. Reactor system results including batch, bench-scale continuous, and engineering-scale processing results are presented to demonstrate the applicability of this catalytic gasification system to biomass. The system has utility both for direct conversion of biomass to fuel gas or as a wastewater cleanup system for treatment of unconverted biomass from bioconversion processes. By the use of this system high conversions of biomass to fuel gas can be achieved. Medium-Btu is the primary product. Potential exists for recovery/recycle of some of the unreacted inorganic components from the biomass in the aqueous byproduct stream.

  12. Development of a catalytic system for gasification of wet biomass

    SciTech Connect

    Elliott, D.C.; Sealock, L.J.; Phelps, M.R.; Neuenschwander, G.G.; Hart, T.R.

    1993-08-01

    A gasification system is under development at Pacific Northwest Laboratory that can be used with high-moisture biomass feedstocks. The system operates at 350 C and 205 atm using a liquid water phase as the processing medium. Since a pressurized system is used, the wet biomass can be fed as a slurry to the reactor without drying. Through the development of catalysts, a useful processing system has been produced. This paper includes assessment of processing test results of different catalysts. Reactor system results including batch, bench-scale continuous, and engineering-scale processing results are presented to demonstrate the applicability of this catalytic gasification system to biomass. The system has utility both for direct conversion of biomass to fuel gas or as a wastewater cleanup system for treatment of unconverted biomass from bioconversion processes. By the use of this system high conversion of biomass to fuel gas can be achieved. Medium-Btu is the primary product. Potential exists for recovery/recycle of some of the unreacted inorganic components from the biomass in the aqueous byproduct stream.

  13. The applicability of the catalytic wet-oxidation to CELSS

    NASA Technical Reports Server (NTRS)

    Takahashi, Y.; Nitta, K.; Ohya, H.; Oguchi, M.

    1987-01-01

    The wet oxidation catalysis of Au, Pd, Pt, Rh or Ru on a ceramic honeycomb carrier was traced in detail by 16 to 20 repetitive batch tests each. As a result, Pt or Pd on a honeycomb carrier was shown to catalyze complete nitrogen gasification as N2. Though the catalysts which realize both complete nitrogen gasification and complete oxidation could not be found, the Ru+Rh catalyst was found to be most promising. Ru honeycomb catalyzed both nitrification and nitrogen gasification.

  14. Catalytic gasification of wet biomass in supercritical water

    SciTech Connect

    Antal, M.J. Jr.; Matsumura, Yukihiko; Xu, Xiaodong

    1995-12-01

    A pressurized catalytic gasification process, operated at 600{degrees}C, 34.5 MPa, efficiently produces a hydrogen rich synthesis gas from high-moisture content biomass. Glucose was selected as a model compound for catalytic biomass gasification. A proprietary heterogeneous catalyst X was extremely effective for the gasification of both the model compound and whole biomass feeds. The effect of temperature, pressure, reactant concentration on the gasification of glucose with catalyst X were investigated. Complete conversion of glucose (22% by weight in water) to gas was obtained at a weight hourly space velocity of 22.2 (g/h)/g in supercritical water at 600{degrees}C, 34.5 MPa. Complete conversion of whole biomass feeds including water hyacinth, depithed bagasse liquid extract, sewage sludge, and paper sludge was also achieved at the same temperature and pressure. The propriety catalyst X is inexpensive and extremely effective.

  15. Catalytic wet oxidation: mathematical modeling of multicompound destruction.

    PubMed

    Yang, J; Hand, D W; Hokanson, D R; Crittenden, J C; Oman, E J

    2003-01-01

    A mathematical model of a three-phase catalytic reactor, CatReac, was developed for analysis and optimization of a catalytic oxidation reactor that is used in the International Space Station potable water processor. The packed-bed catalytic reactor, known as the volatile reactor assembly (VRA), is operated as a three-phase reactor and contains a proprietary catalyst, a pure-oxygen gas phase, and the contaminated water. The contaminated water being fed to the VRA primarily consists of acetic acid, acetone, ethanol, 1-propanol, 2-propanol, and propionic acid ranging in concentration from 1 to 10 mg/L. The Langmuir-Hinshelwood Hougen-Watson (L-H) (Hougen, 1943) expression was used to describe the surface reaction rate for these compounds. Single and multicompound short-column experiments were used to determine the L-H rate parameters and calibrate the model. The model was able to predict steady-state multicomponent effluent profiles for short and full-scale reactor experiments.

  16. Wet air and catalytic wet air oxidation of several azodyes from wastewaters: the beneficial role of catalysis.

    PubMed

    Rodríguez, A; García, J; Ovejero, G; Mestanza, M

    2009-01-01

    Degradation of several azo dyes, Acid Orange 7 (AO7), Acid Orange 74 (AO74), Direct Blue 71 (DB71), Reactive Black 5 (RB5) and Eriochrome Blue Black B (EBBB), well-known non-biodegradable mono, di and tri azo dyes has been studied using, wet-air oxidation (WAO) and catalytic wet air oxidation (CWAO). The efficiency of substrate decolorization and mineralization in each process has been comparatively discussed by evolution concentration, chemical oxygen demand, total organic carbon content and toxicity of dyes solutions. The most efficient method on decolorization and mineralization (TOC) was observed to be CWAO process. Mineralization efficiency with wet air and catalytic wet air oxidation essays was observed in the order of mono-azo > di-azo > tri-azo dye. Final solutions of CWAO applications after 180 min treatment can be disposed safely to environment.

  17. Catalytic wet oxidation of o-chlorophenol at mild temperatures under alkaline conditions.

    PubMed

    Kojima, Yoshihiro; Fukuta, Tadashi; Yamada, Takehisa; Onyango, Maurice S; Bernardo, Eileen C; Matsuda, Hitoki; Yagishita, Kohichi

    2005-01-01

    Wet oxidation of a 100 ppm aqueous solution of o-chlorophenol (o-CP) was performed in a lab-scale batch reactor using 3% Ru/TiO(2) catalyst at 373 and 413 K, and a partial oxygen pressure of 0.1 MPa. The experiments were conducted by varying the initial pH values of o-CP solution from pH 6.3 to 9.8 and 11.8. From the results, it was revealed that the catalytic decomposition of o-CP occurred most effectively at 413 K and at the initial pH of 9.8. Complete decomposition and dechlorination of o-CP were almost achieved within 1h, and about 85% of TOC was removed in 3.0 h. On the other hand, the catalytic wet oxidation of o-CP at a higher pH value of 11.8 was not effective in the removal of TOC. The incomplete removal of TOC at the initial pH of 11.8 is likely attributed to a low pK(a) of carboxylic acids formed during the wet oxidation of o-CP.

  18. Catalytic Wet Gasification of Municipal and Animal Wastes

    SciTech Connect

    Ro, Kyoung S.; Cantrell, Keri; Elliott, Douglas C.; Hunt, Patrick G.

    2007-02-21

    Applicability of wet gasification technology for various animal and municipal wastes was examined. Wet gasification of swine manure and raw sewage sludge generated high number of net energies. Furthermore, the moisture content of these wastes is ideal for current wet gasification technology. Significant quantities of water must be added to dry feedstock wastes such as poultry litter, feedlot manures and MSW to make the feedstock pumpable. Because of their high ash contents, MSW and unpaved feedlot manure would not generate positive energy return from wet gasification. The costs of a conceptual wet gasification manure management system for a model swine farm were significantly higher than that of the anaerobic lagoon system. However, many environmental advantages of the wet gasification system were identified, which might reduce the costs significantly. Due to high sulfur content of the wastes, pretreatment to prevent the poisoning of catalysts is critically needed.

  19. Degradation of phenol via wet-air oxidation over CuO/CeO2-ZrO2 nanocatalyst synthesized employing ultrasound energy: physicochemical characterization and catalytic performance.

    PubMed

    Parvas, Mohsen; Haghighi, Mohammad; Allahyari, Somaiyeh

    2014-01-01

    Catalytic wet air oxidation (CWAO) of phenol was carried out under atmospheric pressure of oxygen at 160 degrees C in a stirred batch reactor over copper catalysts supported by CeO2-ZrO2. The copper with different loadings were impregnated over the composite support by a sonication process. The catalysts were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDX), Brunauer-Emmett-Teller (BET) specific surface area and Fourier-transformed infrared analyses. Characteristic peaks attributed to copper were not found in XRD patterns even at high loadings, but based on EDX results, the existence of copper particles was confirmed. It means that sonochemical synthesis method even at high loadings produced small copper particles with low crystallinity and excellent dispersion over the CeO2-ZrO2 composite. FESEM micrographs indicated just slight enhancement in particle size at high loadings of Cu. Blank CWAO experiments illustrated low conversion of phenol using bare CeO2-ZrO2 support. Although some agglomeration of particles was found at high loadings of copper but owning to the fact that almost all ZrO2 particles incorporated into the CeO2 lattice at high contents of Cu, catalyst activity not only did not decrease but also the phenol conversion reached to the higher values. The optimal catalyst loading for phenol degradation was found to be 9 g/l. Complete conversion of phenol was achieved using CuO/CeO2-ZrO2 in 9 g/l catalyst loading with initial phenol concentration of 1000 ppm after 3 h of reaction.

  20. Catalytic wet oxidation of aqueous methylamine: comparative study on the catalytic performance of platinum-ruthenium, platinum, and ruthenium catalysts supported on titania.

    PubMed

    Song, Aiying; Lu, Gongxuan

    2015-01-01

    Promotion of the dispersion of Ru species supported on TiO2 was achieved by introduction of Pt component and the role of Pt in enhancing the catalytic performances of Pt-Ru was investigated with catalytic wet air oxidation of methylamine used as a probing reaction. It was found that Pt-Ru/TiO2 displayed a much better catalytic performance compared with Pt/TiO2 and Ru/TiO2 catalysts due to having the highest dispersion of active species. Both high total organic carbon conversion and nitrogen selectivity (∼100%) over Pt-Ru/TiO2 catalyst were achieved at low temperature (200 °C). X-ray photoelectron spectroscopy characterization indicated that there were strong interactions between metal particles and the support, which may increase the catalytic performance of catalysts.

  1. Catalytic wet oxidation of thiocyanate with homogeneous copper(II) sulphate catalyst.

    PubMed

    Collado, Sergio; Laca, Adriana; Díaz, Mario

    2010-05-15

    The wet oxidation of thiocyanate has been investigated in a semi-batch reactor at temperatures between 423 and 473 K and pressures between 6.1 x 10(3) and 1.0 x 10(4)kPa in the presence of copper(II) sulphate as catalyst. The effects of copper concentration, initial thiocyanate concentration, pressure and temperature on the reaction rate were analyzed and the main products of reaction were identified. A kinetic model for the Cu-catalyzed reaction is here proposed, including temperature, oxygen concentration, and the reduction of Cu(2+) to Cu(+) that gives an accurate prediction of the oxidation process under the assayed conditions. A mechanistic model based on the formation of a transition complex between a copper cation and two thiocyanate anions has been proposed for the catalytic wet oxidation.

  2. Degradation of phenylamine by catalytic wet air oxidation using metal catalysts with modified supports.

    PubMed

    Torrellas, Silvia A; Escudero, Gabriel O; Rodriguez, Araceli R; Rodriguez, Juan G

    2015-01-01

    The effect of acid treatments with HCl and HNO3 on the surface area and surface chemistry of three granular activated carbons was studied. These supports were characterized and the hydrochloric acid treatment leads to the best activated carbon support (AC2-C). The catalytic behavior of Pt, Ru and Fe (1 wt.%) supported on granular activated carbon treated with HCl was tested in the phenylamine continuous catalytic wet air oxidation in a three-phase, high-pressure catalytic reactor over a range of reaction temperatures 130-170ºC and total pressure of 1.0-3.0 MPa at LHSV = 0.4-1 h(-1), whereas the phenylamine concentration range and the catalyst loading were 5-16 mol.m(-3) and 0.5-1.5 g, respectively. Activity as well as conversion varied as a function of the metal, the catalyst preparation method and operation conditions. Higher activities were obtained with Pt incorporated on hydrochloric acid -treated activated carbon by the ion exchange method. In steady state, approximately 98% phenylamine conversion, 77% of TOC and 94% of COD removal, was recorded at 150ºC, 11 mol m(-3) of phenylamine concentration and 1.5 g of catalyst, and the selectivity to non-organic compounds was 78%. Several reaction intermediaries were detected. A Langmuir-Hinshelwood model gave an excellent fit of the kinetic data of phenylamine continuous catalytic wet air oxidation over the catalysts of this work.

  3. Conversion of the refractory ammonia and acetic acid in catalytic wet air oxidation of animal byproducts.

    PubMed

    Fontanier, Virginie; Zalouk, Sofiane; Barbati, Stéphane

    2011-01-01

    Wet air oxidation (WAO) and catalytic wet air oxidation (CWAO) of slaughtered animal byproducts (ABPs) were investigated. Two step experiment was carried out consisting of a non-catalysed WAO run followed by a CWAO run at 170-275 degrees C, 20 MPa, and reaction time 180 min. The WAO (1st step) of sample (5 g/L total organic carbon (TOC)) yielded (82.0 +/- 4)% TOC removal and (78.4 +/- 13.2)% conversion of the initial organic-N into NH4(+)-N. Four metal catalysts (Pd, Pt, Rh, Ru) supported over alumina have been tested in catalytic WAO (2nd step) at elevated pH to enhance ammonia conversion and organic matter removal, particularly acetic acid. It was found that the catalysts Ru, Pt, and Rh had significant effects on the TOC removal (95.1%, 99.5% and 96.7%, respectively) and on the abatement of ammonia (93.4%, 96.7% and 96.3%, respectively) with high nitrogen selectivity. The catalyst Pd was found to have the less activity while Pt had the best performance. The X-Ray diffraction analysis showed that the support of catalyst was not stable under the experimental conditions since it reacted with phosphate present in solution. Nitrite and nitrate ions were monitored during the oxidation reaction and it was concluded that CWAO of ammonia in real waste treatment framework was in good agreement with the results obtained from the literature for ideal solutions of ammonia.

  4. Low-temperature catalytic gasification of wet industrial wastes

    SciTech Connect

    Elliott, D C; Neuenschwander, G G; Baker, E G; Sealock, Jr, L J; Butner, R S

    1991-04-01

    Bench-scale reactor tests are in progress at Pacific Northwest Laboratory to develop a low-temperature, catalytic gasification system. The system, licensed under the trade name Thermochemical Environmental Energy System (TEES{reg sign}), is designed for treating a wide variety of feedstocks ranging from dilute organics in water to waste sludges from food processing. This report describes a test program which used a continuous-feed tubular reactor. This test program is an intermediate stage in the process development. The reactor is a laboratory-scale version of the commercial concept as currently envisioned by the process developers. An energy benefit and economic analysis was also completed on the process. Four conceptual commercial installations of the TEES process were evaluated for three food processing applications and one organic chemical manufacturing application. Net energy production (medium-Btu gas) was achieved in all four cases. The organic chemical application was found to be economically attractive in the present situation. Based on sensitivity studies included in the analysis, the three food processing cases will likely become attractive in the near future as waste disposal regulations tighten and disposal costs increase. 21 refs., 2 figs., 9 tabs.

  5. Catalytic wet air oxidation of phenol with functionalized carbon materials as catalysts: reaction mechanism and pathway.

    PubMed

    Wang, Jianbing; Fu, Wantao; He, Xuwen; Yang, Shaoxia; Zhu, Wanpeng

    2014-08-01

    The development of highly active carbon material catalysts in catalytic wet air oxidation (CWAO) has attracted a great deal of attention. In this study different carbon material catalysts (multi-walled carbon nanotubes, carbon fibers and graphite) were developed to enhance the CWAO of phenol in aqueous solution. The functionalized carbon materials exhibited excellent catalytic activity in the CWAO of phenol. After 60 min reaction, the removal of phenol was nearly 100% over the functionalized multi-walled carbon, while it was only 14% over the purified multi-walled carbon under the same reaction conditions. Carboxylic acid groups introduced on the surface of the functionalized carbon materials play an important role in the catalytic activity in CWAO. They can promote the production of free radicals, which act as strong oxidants in CWAO. Based on the analysis of the intermediates produced in the CWAO reactions, a new reaction pathway for the CWAO of phenol was proposed in this study. There are some differences between the proposed reaction pathway and that reported in the literature. First, maleic acid is transformed directly into malonic acid. Second, acetic acid is oxidized into an unknown intermediate, which is then oxidized into CO2 and H2O. Finally, formic acid and oxalic acid can mutually interconvert when conditions are favorable.

  6. Catalytic wet oxidation of phenol: the role of promoter and ceramic support.

    PubMed

    Hussain, S Tajammul; Jamil, Sadaf; Mazhar, Muhammad

    2009-04-14

    Complete mineralization of phenol has been achieved over a cerium-manganese catalyst, doped with potassium, supported on a modified zeolite with a high surface area, under very mild conditions (110 degrees C, P(O2) = 0.5 MPa). This newly developed supported catalyst restricts the formation of bulk polymeric species on the surface, thus increasing the lifetime of the catalyst. It demonstrates superior textural, structural and surface oxygen properties compared with the reference cerium-manganese oxide catalyst. The supported catalyst maintains not only the high surface area but also the nanoparticle size during the catalytic run, thereby providing the full availability of the surface for reacting molecules. The geometry of the catalyst is modified electronically by the addition of potassium, and the zeolite addition restricts the conversion of Ce, Mn and K to higher oxidation states, thereby maintaining the geometry of catalytic active sites. The performance measured with this novel catalyst indicates a major improvement in the efficient application of the catalytic wet oxidation process for complete purification ofa complex waste stream.

  7. Post-treatment of refinery wastewater effluent using a combination of AOPs (H2O2 photolysis and catalytic wet peroxide oxidation) for possible water reuse. Comparison of low and medium pressure lamp performance.

    PubMed

    Rueda-Márquez, J J; Levchuk, I; Salcedo, I; Acevedo-Merino, A; Manzano, M A

    2016-03-15

    The main aim of this work was to study the feasibility of multi-barrier treatment (MBT) consisting of filtration, hydrogen peroxide photolysis (H2O2/UVC) and catalytic wet peroxide oxidation (CWPO) for post-treatment of petroleum refinery effluent. Also the possibility of water reuse or safe discharge was considered. The performance of MBT using medium (MP) and low (LP) pressure lamps was compared as well as operation and maintenance (O&M) cost. Decomposition of organic compounds was followed by means of gas chromatography-mass spectrometry (GC-MS), total organic carbon (TOC) and chemical oxygen demand (COD) analysis. After filtration step (25 μm) turbidity and concentration of suspended solids decreased by 92% and 80%, respectively. During H2O2/UVC process with LP lamp at optimal conditions (H2O2:TOC ratio 8 and UVC dose received by water 5.28 WUVC s cm(-2)) removal of phenolic compounds, TOC and COD was 100%, 52.3% and 84.3%, respectively. Complete elimination of phenolic compounds, 47.6% of TOC and 91% of COD was achieved during H2O2/UVC process with MP lamp at optimal conditions (H2O2:TOC ratio 5, UVC dose received by water 6.57 WUVC s cm(-2)). In order to compare performance of H2O2/UVC treatment with different experimental set up, the UVC dose required for removal of mg L(-1) of COD was suggested as a parameter and successfully applied. The hydrophilicity of H2O2/UVC effluent significantly increased which in turn enhanced the oxidation of organic compounds during CWPO step. After H2O2/UVC treatment with LP and MP lamps residual H2O2 concentration was 160 mg L(-1) and 96.5 mg L(-1), respectively. Remaining H2O2 was fully consumed during subsequent CWPO step (6 and 3.5 min of contact time for LP and MP, respectively). Total TOC and COD removal after MBT was 94.7% and 92.2% (using LP lamp) and 89.6% and 95%, (using MP lamp), respectively. The O&M cost for MBT with LP lamp was estimated to be 0.44 € m(-3) while with MP lamp it was nearly five

  8. P-chlorophenol wastewater treatment by microwave-enhanced catalytic wet peroxide oxidation.

    PubMed

    Zhao, Guohua; Lv, Baoying; Jin, Yan; Li, Dongming

    2010-02-01

    A microwave-enhanced catalytic wet peroxide oxidation (MW-CWPO) technology was investigated to treat a high concentration of p-chlorophenol wastewater under a mild condition. The MW-CWPO experiments were carried out in a microwave autoclave using copper(II) oxide (CuO)-loaded active carbon as a catalyst. The p-chlorophenol was directly ring-opened within 5 minutes at 343 K and 0.3 MPa and then mineralized to carbon dioxide and water. More than 90% of the total organic carbon was removed within 15 minutes. The reaction activation energy (Ea) of hydrogen peroxide (H2O2) decomposition was decreased from 47.7 to 43.1 kJ/mol under microwave irradiation. The H2O2 catalytic decomposition was fitted to a second-order reaction under microwave irradiation, while it followed a first-order reaction without microwave irradiation. The experimental results indicate that the MW-CWPO method has significant potential applications for a high concentration of p-chlorophenol wastewater.

  9. Integrated catalytic wet air oxidation and biological treatment of wastewater from Vitamin B 6 production

    NASA Astrophysics Data System (ADS)

    Kang, Jianxiong; Zhan, Wei; Li, Daosheng; Wang, Xiaocong; Song, Jing; Liu, Dongqi

    This study investigated the feasibility of coupling a catalytic wet air oxidation (CWAO), with CuO/Al 2O 3 as catalyst, and an anaerobic/aerobic biological process to treat wastewater from Vitamin B 6 production. Results showed that the CWAO enhanced the biodegradability (BOD 5/COD) from 0.10 to 0.80. The oxidized effluents with COD of 10,000 mg l -1 was subjected to subsequent continuous anaerobic/aerobic oxidation, and 99.3% of total COD removal was achieved. The quality of the effluent obtained met the discharge standards of water pollutants for pharmaceutical industry Chemical Synthesis Products Category (GB21904-2008), and thereby it implies that the integrated CWAO and anaerobic/aerobic biological treatment may offer a promising process to treat wastewater from Vitamin B 6 production.

  10. Low-Temperature Catalytic Gasification of Wet Biomass

    SciTech Connect

    Elliott, Douglas C.; Neuenschwander, Gary G.; Hart, Todd R.; Zacher, Alan H.; Butner, R SCOTT.

    2003-11-16

    Through the use of a metal catalyst, gasification of wet biomass can be accomplished with high levels of carbon conversion to gas at relatively low temperature (350 degrees Celsius). In the pressurized-water environment (3000 psig) near-total conversion of the organic structure of biomass to gases has been accomplished in the presence of a ruthenium metal catalyst. The process is essentially steam reforming as there is no added oxidizer or reagent other than water. In addition, the gas produced is a medium-heating value gas due to the synthesis of high-levels of methane, as dictated by thermodynamic equilibrium. Processing systems and results are described for both bench-scale and scaled-up reactor systems.

  11. Thermal and sonochemical synthesis of porous (Ce,Zr)O2 mixed oxides from metal β-diketonate precursors and their catalytic activity in wet air oxidation process of formic acid.

    PubMed

    Cau, Camille; Guari, Yannick; Chave, Tony; Larionova, Joulia; Nikitenko, Sergey I

    2014-07-01

    Porous (Ce0.5Zr0.5)O2 solid solutions were prepared by thermolysis (T=285 °C) or sonolysis (20 kHz, I=32 W cm(-2), Pac=0.46 W mL(-1), T=200 °C) of Ce(III) and Zr(IV) acetylacetonates in oleylamine or hexadecylamine under argon followed by heat treatment of the precipitates obtained in air at 450 °C. Transmission Electron Microscopy images of the samples show nanoparticles of ca. 4-6 nm for the two synthetic approaches. The powder X-ray diffraction, scanning electron microscopy, energy dispersive X-ray and μ-Raman spectroscopy of solids obtained after heat treatment indicate the formation of (Ce0.5Zr0.5)O2 solid solutions with a metastable tetragonal crystal structure for the two synthetic routes. The specific surface area of the samples varies between 78 and 149 m(2) g(-1) depending on synthesis conditions. The use of Barrett-Joyner-Halenda and t-plot methods reveal the formation of mixed oxides with a hybrid morphology that combines mesoporosity and microporosity regardless of the method of preparation. Platinum nanoparticles were deposited on the surface of the mixed oxides by sonochemical reduction of Pt(IV). It was found that the materials prepared by sonochemistry exhibit better resistance to dissolution during the deposition process of platinum. X-ray photoelectron spectroscopy analysis shows the presence of Pt(0) and Pt(II) on the surface of mixed oxides. Porous (Ce0.5Zr0.5)O2 mixed oxides loaded with 1.5%wt. platinum exhibit high activity in catalytic wet air oxidation of formic acid at 40 °C. Copyright © 2014 Elsevier B.V. All rights reserved.

  12. Catalytic wet peroxide oxidation of p-nitrophenol by Fe (III) supported on resin.

    PubMed

    Liou, Rey-May; Chen, Shih-Hsiung; Huang, Cheng-Hsien; Lai, Cheng-Lee; Shih, C Y; Chang, Jing-Song; Hung, Mu-Ya

    2010-01-01

    Fe(III) supported on resin (Fe(III)-resin) as an effective catalyst for peroxide oxidation was prepared and applied for the degradation of p-nitrophenol (PNP). Catalytic wet peroxide oxidation (CWPO) experiments with hydrogen peroxide as oxidant were performed in a batch rector with p-nitrophenol as the model pollutant. Under given conditions (PNP concentration 500 mg/L, H(2)O(2) 0.1 M, 80°C, resin dosage 0.6% g/mL), p-nitrophenol was almost completely removed, corresponding to an 84% of COD removal. It was found that the reaction temperature, oxidant concentration. and initial pH of solution significantly affected both p-nitrophenol conversion and COD removal by oxidation. It can be inferred from the experiments that Fe(III) supported on resin was an effective catalyst in the mineralization of p-nitrophenol. In an acidic environment of oxidation, the leaching test showed that there was only a slight leaching effect on the activity of catalytic oxidation. It was also confirmed by the aging test of catalysts in the oxidation.

  13. Comparative kinetic analysis of silent and ultrasound-assisted catalytic wet peroxide oxidation of phenol.

    PubMed

    Rokhina, Ekaterina V; Repo, Eveliina; Virkutyte, Jurate

    2010-03-01

    The kinetic study of silent and ultrasound-assisted catalytic wet peroxide oxidation of phenol in water was performed to qualitatively assess the effect of ultrasound on the process kinetics. Various kinetic parameters such as the apparent kinetic rate constants, the surface utilization coefficient and activation energy of phenol oxidation over RuI(3) catalyst were investigated. Comparative analysis revealed that the use of ultrasound irradiation reduced the energy barrier of the reaction but had no impact on the reaction pathway. The activation energy for the oxidation of phenol over RuI(3) catalyst in the presence of ultrasound was found to be 13kJmol(-1), which was four times smaller in comparison to the silent oxidation process (57kJmol(-1)). Finally, 'figures-of-merit' was utilized to assess different experimental strategies such as sonolysis alone, H(2)O(2)-enhanced sonolysis and sono-catalytic oxidation of phenol in order to estimate the electric energy consumption based on the kinetic rate constants of the oxidation process.

  14. Low-Temperature Catalytic Gasification of Wet Biomass Residues

    SciTech Connect

    Elliott, Douglas C.; Neuenschwander, Gary G.; Hart, Todd R.; Butner, R. Scott

    2004-10-27

    Low-temperature hydrothermal gasification can be applied to biorefinery residues as an efficient energy recovery process. Through the use of a metal catalyst, gasification of wet biomass can be accomplished with high levels of carbon conversion to medium heating value gas at relatively low temperature (350 degrees Celsius). In the pressurized-water environment (21 MPa) near-total conversion of the organic structure of biomass to gases has been accomplished in the presence of a ruthenium metal catalyst. The process is essentially steam reforming as there is no added oxidizer or reagent other than water. In addition, the gas is produced with high-levels of methane, as dictated by thermodynamic equilibrium. Processing systems and results will be described for both bench-scale and scaled-up reactor systems. The bench-scale systems include both short-term 1-liter batch reactor tests and longer-term continuous flow reactor tests using a 1-liter fixed bed of catalyst in a tubular reactor. The scaled-up reactor is a 4.4 liter version of the continuous flow system, which also includes a high-pressure heat exchanger to demonstrate process efficiency.

  15. Catalytic oxidation with Al-Ce-Fe-PILC as a post-treatment system for coffee wet processing wastewater.

    PubMed

    Sanabria, Nancy R; Peralta, Yury M; Montañez, Mardelly K; Rodríguez-Valencia, Nelson; Molina, Rafael; Moreno, Sonia

    2012-01-01

    The effluent from the anaerobic biological treatment of coffee wet processing wastewater (CWPW) contains a non-biodegradable compound that must be treated before it is discharged into a water source. In this paper, the wet hydrogen peroxide catalytic oxidation (WHPCO) process using Al-Ce-Fe-PILC catalysts was researched as a post-treatment system for CWPW and tested in a semi-batch reactor at atmospheric pressure and 25 °C. The Al-Ce-Fe-PILC achieved a high conversion rate of total phenolic compounds (70%) and mineralization to CO(2) (50%) after 5 h reaction time. The chemical oxygen demand (COD) of coffee processing wastewater after wet hydrogen peroxide catalytic oxidation was reduced in 66%. The combination of the two treatment methods, biological (developed by Cenicafé) and catalytic oxidation with Al-Ce-Fe-PILC, achieved a 97% reduction of COD in CWPW. Therefore, the WHPCO using Al-Ce-Fe-PILC catalysts is a viable alternative for the post-treatment of coffee processing wastewater.

  16. A compact process for the treatment of olive mill wastewater by combining wet hydrogen peroxide catalytic oxidation and biological techniques.

    PubMed

    Azabou, Samia; Najjar, Wahiba; Bouaziz, Mohamed; Ghorbel, Abdelhamid; Sayadi, Sami

    2010-11-15

    A system based on combined actions of catalytic wet oxidation and microbial technologies for the treatment of highly polluted OMW containing polyphenols was studied. The wet hydrogen peroxide catalytic oxidation (WHPCO) process has been investigated in the semi-batch mode at atmospheric pressure, using aluminium-iron-pillared inter layer clay ((Al-Fe)PILC), under two different catalytic processes: ((Al-Fe)PILC/H(2)O(2)/ultraviolet radiations) at 25°C and ((Al-Fe)PILC/H(2)O(2)) at 50°C. The results show that raw OMW was resistant to the photocatalytic process. However ((Al-Fe)PILC/H(2)O(2)), system operating at 50°C reduced considerably the COD, colour and total phenolic contents, and thus decreased the inhibition of the marine photobacteria Vibrio fischeri luminescence by 70%. This study also examined the feasibility of coupling WHPCO and anaerobic digestion treatment. Biomethanisation experiments performed with raw OMW or pre-treated OMW proved that pre-treatments with ((Al-Fe)PILC/H(2)O(2)) system, for more than 2 h, resulted in higher methane production. Both untreated OMW as well as 2-h pre-treated OMW revealed as toxic to anaerobic bacteria.

  17. Ultrasound assisted catalytic wet peroxide oxidation of phenol: kinetics and intraparticle diffusion effects.

    PubMed

    Nikolopoulos, Apostolos N; Igglessi-Markopoulou, Olga; Papayannakos, Nikolaos

    2006-01-01

    The combination of ultrasound irradiation and catalytic wet peroxide oxidation was used as a means to degrade phenol. Direct and indirect irradiation were employed, while experiments in the absence of ultrasound were used as reference. A mixed (Al-Fe) pillared clay named FAZA, was used as a catalyst in the form of powder, extrudates and crushed extrudates. Ultrasound was found to clearly enhance the extrudates performance, increasing the conversion at 4h by more than 6 times under direct and almost 11 times under indirect irradiation. This observation is attributed to the reduction of diffusion resistance within the catalyst pores. The overall sonication-catalytic wet peroxide oxidation process appears very promising for environmental purposes.

  18. The degradation of Isophorone by catalytic wet air oxidation on Ru/TiZrO4.

    PubMed

    Wei, Huangzhao; Yan, Xiaomiao; Li, Xianru; He, Songbo; Sun, Chenglin

    2013-01-15

    The catalyst Ru/TiZrO(4) was applied in the degradation of Isophorone by catalytic wet air oxidation. Mathematical models for the effects of reaction conditions on the Isophorone degradation by catalytic wet air oxidation were developed using a response surface methodology. A model was obtained for each response with multiple regression analysis and then was refined. Analysis of variance revealed that the models developed were adequate. The validity of the models was also verified by experimental data. Analysis of response surface showed that total organic carbon removal and Isophorone conversion were significantly affected (P≤0.01) by reaction time, temperature and their interactions, and affected (P≤0.05) by the square of reaction time. The point of zero charge of Ru/TiZrO(4) catalyst was about 1.72. The total organic carbon removal and Isophorone conversion had a great association with the zeta potential of Ru/TiZrO(4) catalyst. Finally, the degradation pathway of Isophorone in catalytic wet air oxidation was proposed. Within 410 h, the total organic carbon removal remained above 95%, indicating that the Ru/TiZrO(4) catalyst had a good stability.

  19. Ruthenium catalysts supported on high-surface-area zirconia for the catalytic wet oxidation of N,N-dimethyl formamide.

    PubMed

    Sun, Guanglu; Xu, Aihua; He, Yu; Yang, Min; Du, Hongzhang; Sun, Chenglin

    2008-08-15

    Three weight percent ruthenium catalysts were prepared by incipient-wet impregnation of two different zirconium oxides, and characterized by BET, XRD and TPR. Their activity was evaluated in the catalytic wet oxidation (CWO) of N,N-dimethyl formamide (DMF) in an autoclave reactor. Due to a better dispersion, Ru catalyst supported on a high-surface-area zirconia (Ru/ZrO(2)-A) possessed higher catalytic properties. Due to over-oxidation of Ru particles, the catalytic activity of the both catalysts decreased during successive tests. The effect of oxygen partial pressure and reaction temperature on the DMF reactivity in the CWO on Ru/ZrO(2)-A was also investigated. 98.6% of DMF conversion was obtained through hydrothermal decomposition within 300 min at conditions of 200 degrees C and 2.0 MPa of nitrogen pressure. At 240 degrees C and 2.0 MPa of oxygen pressure 98.3% of DMF conversion was obtained within 150 min.

  20. SPONTANEOUS CATALYTIC WET AIR OXIDATION DURING PRE-TREATMENT OF HIGH-LEVEL RADIOACTIVE WASTE SLUDGE

    SciTech Connect

    Koopman, D.; Herman, C.; Pareizs, J.; Bannochie, C.; Best, D.; Bibler, N.; Fellinger, T.

    2009-10-01

    Savannah River Remediation, LLC (SRR) operates the Defense Waste Processing Facility for the U.S. Department of Energy at the Savannah River Site. This facility immobilizes high-level radioactive waste through vitrification following chemical pretreatment. Catalytic destruction of formate and oxalate ions to carbon dioxide has been observed during qualification testing of non-radioactive analog systems. Carbon dioxide production greatly exceeded hydrogen production, indicating the occurrence of a process other than the catalytic decomposition of formic acid. Statistical modeling was used to relate the new reaction chemistry to partial catalytic wet air oxidation of both formate and oxalate ions driven by the low concentrations of palladium, rhodium, and/or ruthenium in the waste. Variations in process conditions led to increases or decreases in the total oxidative destruction, as well as partially shifting the preferred species undergoing destruction from oxalate ion to formate ion.

  1. Catalytic wet peroxide oxidation of azo dye (Congo red) using modified Y zeolite as catalyst.

    PubMed

    Kondru, Arun Kumar; Kumar, Pradeep; Chand, Shri

    2009-07-15

    The present study explores the degradation of azo dye (Congo red) by catalytic wet peroxide oxidation using Fe exchanged commercial Y zeolite as a catalyst. The effects of various operating parameters like temperature, initial pH, hydrogen peroxide concentration and catalyst loading on the removal of dye, color and COD from an aqueous solution were studied at atmospheric pressure. The percent removals of dye, color and COD at optimum pH(0) 7, 90 degrees C using 0.6 ml H(2)O(2)/350 ml solution and 1g/l catalyst was 97% (in 4h), 100% (in 45 min) and 58% (in 4h), respectively. The % dye removal has been found to be less in comparison to % color removal at all conditions, e.g. dye removal in 45 min and at above conditions was 82%, whereas the color removal was 100%. The results indicate that the Fe exchanged Y zeolite is a promising catalyst for dye removal. Fe exchanged catalyst is characterized using XRD, SEM/EDAX, surface area analyzer and FTIR. Though the dye, color and COD removals were maximum at pH(0) 2 but as the leaching of Fe from the catalyst was more in acidic pH range, pH(0) 7 was taken as operating pH due to almost comparable removals as of pH(0) 2 and no leaching of Fe ions.

  2. Chloride ions promoted the catalytic wet peroxide oxidation of phenol over clay-based catalysts.

    PubMed

    Zhou, Shiwei; Zhang, Changbo; Xu, Rui; Gu, Chuantao; Song, Zhengguo; Xu, Minggang

    2016-01-01

    Catalytic wet peroxide oxidation (CWPO) of phenol over clay-based catalysts in the presence and absence of NaCl was investigated. Changes in the H2O2, Cl(-), and dissolved metal ion concentration, as well as solution pH during phenol oxidation, were also studied. Additionally, the intermediates formed during phenol oxidation were detected by liquid chromatography-mass spectroscopy and the chemical bonding information of the catalyst surfaces was analyzed by X-ray photoelectron spectroscopy (XPS). The results showed that the presence of Cl(-) increased the oxidation rate of phenol to 155%, and this phenomenon was ubiquitous during the oxidation of phenolic compounds by H2O2 over clay-based catalysts. Cl(-)-assisted oxidation of phenol was evidenced by several analytical techniques such as mass spectroscopy (MS) and XPS, and it was hypothesized that the rate-limiting step was accelerated in the presence of Cl(-). Based on the results of this study, the CWPO technology appears to be promising for applications in actual saline phenolic wastewater treatment.

  3. Activity and leaching features of zinc-aluminum ferrites in catalytic wet oxidation of phenol.

    PubMed

    Xu, Aihua; Yang, Min; Qiao, Ruiping; Du, Hongzhang; Sun, Chenglin

    2007-08-17

    A series of ZnFe(2-x)Al(x)O(4) spinel type catalysts prepared by sol-gel method have been characterized and tested for catalytic wet oxidation (CWO) of phenol with pure oxygen. The iron species existed in these materials as aggregated iron oxide clusters and Fe3+ species in octahedral sites. With a decrease in iron content the concentration of the first iron species decreased and the latter increased. Complete phenol conversions and high chemical oxygen demand (COD) removals were obtained for all catalysts during phenol degradation at mild reaction conditions (160 degrees C and 1.0 MPa of oxygen pressure). Increasing with the concentration of Fe3+ species in octahedral sites, induction period became significantly shortened. After phenol was completely degraded, the concomitant recycling of the leaching Fe3+ ions back to the catalyst surface was observed, and in this case it is possible to perform successful CWO reactions with some cycles. It is also suggested that during the reaction the Fe3+ cations coordinated in octahedral sites in the ZnFe(2-x)Al(x)O(4) catalysts are resistant to acid leaching, but the reduced Fe2+ cations become much more labile, leading to increased Fe leaching.

  4. Catalytic wet peroxidation of pyridine bearing wastewater by cerium supported SBA-15.

    PubMed

    Subbaramaiah, V; Srivastava, Vimal Chandra; Mall, Indra Deo

    2013-03-15

    Cerium supported SBA-15 (Ce/SBA-15) was synthesized by two-step synthesis method in acidic medium. It was further characterized by various characterization techniques such as X-ray diffraction, field-emission scanning electron microscopy, Fourier transform infrared spectroscopy and N2 adsorption-desorption pore size distribution analysis. The Ce/SBA-15 showed highly ordered meso-structure with pore diameter≈70-100Ǻ and pore volume≈0.025cm(3)/g. Ce/SBA-15 was further evaluated as a catalyst for the oxidation of highly toxic and non-biodegradable material, pyridine, by catalytic wet-peroxidation method. The effects of various operating parameters such as catalyst dose (0.5-6g/l), stoichiometric ratio of H2O2/pyridine (1-6), initial pyridine concentration (50-800mg/l) and temperature (313-358K) have been evaluated and optimized. Ce/SBA-15 showed stable performance during reuse for six cycles with negligible cerium leaching. Kinetic and thermodynamic parameters and operation cost have also been determined.

  5. Catalytic wet oxidation of the pretreated synthetic pulp and paper mill effluent under moderate conditions.

    PubMed

    Garg, Anurag; Mishra, I M; Chand, Shri

    2007-01-01

    In the present study, catalytic wet oxidation (CWO) was investigated for the destruction of organic pollutants in the thermally pretreated effluent from a pulp and paper mill under moderate temperature and pressure conditions. The thermal pretreatment studies were conducted at atmospheric pressure and 368K using copper sulfate as a catalyst. The thermal pretreatment reduced COD by about 61%. The filtrate of the thermal pretreatment step was used at pH 8.0 for CWO at 383-443K temperature and a total pressure of 0.85MPa for 4h. Catalysts used for the reaction include copper sulfate, 5% CuO/95% activated carbon, 60% CuO/40% MnO(2), and 60% CuO/40% CeO(2). Maximum COD reduction was found to be 89% during CWO step using 5% CuO/95% activated carbon with a catalyst loading of 8gl(-1) at 443K and 0.85MPa total pressure. Overall COD reduction for the pretreatment and the CWO was found to be 96%. Besides this, 60% CuO/40% CeO(2) catalyst also exhibited the similar activity as that of obtained with 5% CuO/95% activated carbon catalyst at 423K temperature and 0.85MPa total pressure. The pH of the solution during the experimental runs decreases initially due to the formation of carboxylic acid and then increases due to the decomposition of acids.

  6. Catalytic wet air oxidation of aniline with nanocasted Mn-Ce-oxide catalyst.

    PubMed

    Levi, R; Milman, M; Landau, M V; Brenner, A; Herskowitz, M

    2008-07-15

    The catalytic wet air oxidation of aqueous solution containing 1000 ppm aniline was conducted in a trickle-bed reactor packed with a novel nanocasted Mn-Ce-oxide catalyst (surface area of 300 m2/g) prepared using SBA-15 silica as a hard template. A range of liquid hourly space velocities (5-20 h(-1)) and temperatures (110-140 degrees C) at 10 bar of oxygen were tested. The experiments were conducted to provide the intrinsic performance of the catalysts. Complete aniline conversion, 90% TOC conversion, and 80% nitrogen mineralization were achieved at 140 degrees C and 5 h(-1). Blank experiments yielded relatively low homogeneous aniline (<35%) and negligible TOC conversions. Fast deactivation of the catalysts was experienced due to leaching caused by complexation with aniline. Acidification of the solution with HCI (molar HCI to aniline ratio of 1.2) was necessary to avoid colloidization and leaching of the nanoparticulate catalyst components. The catalyst displayed stable performance for over 200 h on stream.

  7. Supported noble metal catalysts in the catalytic wet air oxidation of industrial wastewaters and sewage sludges.

    PubMed

    Besson, M; Descorme, C; Bernardi, M; Gallezot, P; di Gregorio, F; Grosjean, N; Minh, D Pham; Pintar, A

    2010-12-01

    This paper reviews some catalytic wet air oxidation (CWAO) investigations of industrial wastewaters over platinum and ruthenium catalysts supported on TiO2 and ZrO2 formulated to be active and resistant to leaching, with particular focus on the stability of the catalyst. Catalyst recycling experiments were performed in batch reactors and long-term stability tests were conducted in trickle-bed reactors. The catalyst did not leach upon treatment of Kraft bleaching plant and olive oil mill effluents, and could be either recycled or used for long periods of time in continuous reactors. Conversely, these catalysts were rapidly leached when used to treat effluents from the production of polymeric membranes containing N,N-dimethylformamide. The intermediate formation of amines, such as dimethylamine and methylamine with a high complexing capacity for the metal, was shown to be responsible for the metal leaching. These heterogeneous catalysts also deactivated upon CWAO of sewage sludges due to the adsorption of the solid organic matter. Pre-sonication of the sludge to disintegrate the flocs and improve solubility was inefficient.

  8. [Copper leaching in catalytic wet oxidation of phenol with Cu-containing spinel].

    PubMed

    Xu, Ai-hua; He, Song-bo; Yang, Min; Du, Hong-zhang; Sun, Cheng-lin

    2008-09-01

    The Cu0.10, Zn0.90 Al1.90 Fe0.10 O4 spinel type catalyst prepared by sol-gel method was tested for catalytic wet air oxidation of phenol. The performances of Cu0.10 Zn0.90 Al1.90 Fe0.10 O4 catalyst in TPR experiment, the influence of phenol as reducer, reaction temperature and phenol-to-catalyst mass ratio on copper leaching were checked respectively. According to the experimental results, it is suggested that the reduced active species can not be easily re-oxidized under low reaction temperature and high phenol-to-catalyst mass ratio are the main reasons for copper leaching. Under high enough reaction temperature and low phenol-to-catalyst mass ratio, the copper leaching reduces remarkably. At 190 degrees C in the presence of 100 mL aqueous solution of 4.29 g x L(-1) of phenol and 2.5 g catalyst, the copper leaching was only 0.96 mg x L(-1) after 2 h of reaction.

  9. Catalytic wet-air oxidation of a chemical plant wastewater over platinum-based catalysts.

    PubMed

    Cybulski, Andrzej; Trawczyński, Janusz

    2006-01-01

    Catalytic wet-air oxidation (CWAO) of wastewater (chemical oxygen demand [COD] = 1800 mg O2/dm3) from a fine chemicals plant was investigated in a fixed-bed reactor at T = 393-473 K under total pressure of 5.0 or 8.0 MPa. Catalysts containing 0.3% wt. of platinum deposited on two supports, mixed silica-titania (SM1) and carbon black composites (CBC) were used. The CBC-supported catalyst appeared to be more active than the SM1-supported one. A slow decrease of activity of the platinum on SM1 (Pt-SM1) during the long-term operation is attributed to recrystallization of titania and leaching of a support component, while the Pt-CBC catalyst is deteriorated, owing to combustion of the support component. The power-law-kinetic equations were used to describe the rate of COD removal at CWAO over the catalysts. The kinetic parameters of COD reduction for the wastewater were determined and compared with the kinetic parameters describing phenol oxidation over the same catalysts. Rates of COD removal for the wastewater were found higher than those for phenol oxidation over the same catalysts and under identical operating conditions.

  10. Heterogeneous catalytic wet air oxidation of refractory organic pollutants in industrial wastewaters: a review.

    PubMed

    Kim, Kyoung-Hun; Ihm, Son-Ki

    2011-02-15

    Catalytic wet air oxidation (CWAO) is one of the most economical and environmental-friendly advanced oxidation process. It makes a promising technology for the treatment of refractory organic pollutants in industrial wastewaters. Various heterogeneous catalysts including noble metals and metal oxides have been extensively studied to enhance the efficiency of CWAO. The present review is concerned about the literatures published in this regard. Phenolics, carboxylic acids, and nitrogen-containing compounds were taken as model pollutants in most cases, and noble metals such as Ru, Rh, Pd, Ir, and Pt as well as oxides of Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, and Ce were applied as heterogeneous catalysts. Reports on their characterization and catalytic performances for the CWAO of aqueous pollutants are reviewed. Discussions are also made on the reaction mechanisms and kinetics proposed for heterogeneous CWAO and also on the typical catalyst deactivations in heterogeneous CWAO, i.e. carbonaceous deposits and metal leaching.

  11. Heterogeneous catalytic wet peroxide oxidation systems for the treatment of an industrial pharmaceutical wastewater.

    PubMed

    Melero, J A; Martínez, F; Botas, J A; Molina, R; Pariente, M I

    2009-09-01

    The aim of this work was to assess the treatment of wastewater coming from a pharmaceutical plant through a continuous heterogeneous catalytic wet peroxide oxidation (CWPO) process using an Fe(2)O(3)/SBA-15 nanocomposite catalyst. This catalyst was preliminary tested in a batch stirred tank reactor (STR), to elucidate the influence of significant parameters on the oxidation system, such as temperature, initial oxidant concentration and initial pH of the reaction medium. In that case, a temperature of 80 degrees C using an initial oxidant concentration corresponding to twice the theoretical stoichiometric amount for complete carbon depletion and initial pH of ca. 3 allow TOC degradation of around 50% after 200 min of contact time. Thereafter, the powder catalyst was extruded with bentonite to prepare pellets that could be used in a fixed bed reactor (FBR). Results in the up-flow FBR indicate that the catalyst shows high activity in terms of TOC mineralization (ca. 60% under steady-state conditions), with an excellent use of the oxidant and high stability of the supported iron species. The activity of the catalyst is kept constant, at least, for 55h of reaction. Furthermore, the BOD(5)/COD ratio is increased from 0.20 to 0.30, whereas the average oxidation stage (AOS) changed from 0.70 to 2.35. These two parameters show a high oxidation degree of organic compounds in the outlet effluent, which enhances its biodegradability, and favours the possibility of a subsequent coupling with a conventional biological treatment.

  12. Tough and catalytically active hybrid biofibers wet-spun from nanochitin hydrogels.

    PubMed

    Das, Paramita; Heuser, Thomas; Wolf, Andrea; Zhu, Baolei; Demco, Dan Eugen; Ifuku, Shinsuke; Walther, Andreas

    2012-12-10

    Sustainable alternatives for high-performance and functional materials based on renewable resources are intensely needed as future alternatives for present-day, fossil-based materials. Nanochitin represents an emerging class of highly crystalline bionanoparticles with high intrinsic mechanical properties and the ability for conjugation into functional materials owing to reactive amine and hydroxyl groups. Herein we demonstrate that hydrogels containing surface-deacetylated chitin nanofibrils of micrometer length and average diameters of 9 nm, as imaged by cryogenic transmission electron microscopy, can be wet-spun into macrofibers via extrusion in a coagulation bath, a simple low energy and large-scale processing route. The resulting biofibers display attractive mechanical properties with a large plastic region of about 12% in strain, in which frictional sliding of nanofibrils allows dissipation of fracture energy and enables a high work-of-fracture of near 10 MJ/m3. We further show how to add functionality to these macrofibers by exploiting the amine functions of the surface chitosan groups to host catalytically active noble metal nanoparticles, furnishing biobased, renewable catalytic hybrids. These inorganic/organic macrofibers can be used repeatedly for fast catalytic reductions of model compounds without loss of activity, rendering the concept of hybridized chitin materials interesting as novel bioderived supports for nanoparticle catalysts.

  13. Catalytic wet oxidation of ammonia solution: activity of the nanoscale platinum-palladium-rhodium composite oxide catalyst.

    PubMed

    Hung, Chang-Mao

    2009-04-15

    Aqueous solutions of 400-1000 mg/L of ammonia were oxidized in a trickle-bed reactor (TBR) in this study of nanoscale platinum-palladium-rhodium composite oxide catalysts, which were prepared by the co-precipitation of H(2)PtCl(6), Pd(NO(3))(3) and Rh(NO(3))(3). Hardly any of the dissolved ammonia was removed by wet oxidation in the absence of any catalyst, whereas about 99% of the ammonia was reduced during wet oxidation over nanoscale platinum-palladium-rhodium composite oxide catalysts at 503 K in an oxygen partial pressure of 2.0 MPa. A synergistic effect exists in the nanoscale platinum-palladium-rhodium composite structure, which is the material with the highest ammonia reduction activity. The nanometer-sized particles were characterized by TEM, XRD and FTIR. The effect of the initial concentration and reaction temperature on the removal of ammonia from the effluent streams was also studied at a liquid hourly space velocity of under 9 h(-1) in the wet catalytic processes.

  14. Homogeneous catalytic wet-air oxidation for the treatment of textile wastewater

    SciTech Connect

    Lei, L. Chen, G.; Hu, X.; Yue, P.L.

    2000-04-01

    An extensive series of experiments was performed to identify suitable catalysts to increase the reaction rate of wet-air oxidation of textile wastewater t relatively mild temperatures an pressures. Wastewater types treated included natural-fiber desizing wastewater, synthetic-fiber desizing wastewater, and printing and dyeing wastewater. Experimental results indicated that all catalysts tested in this investigation significantly increased the chemical oxygen demand (COD) and total organic carbon (TOC) removal rates and total COD and TOC removals. Of all catalysts tested, copper salts were the most effective. Anions in the slat solutions played a role in the catalytic process. Nitrate ions were more effective than sulfate ions. Similarly, copper nitrates were more effective than copper sulfates. A mixture of salts containing different metals performed better than any single salt.

  15. Catalytic wet air oxidation with Ni- and Fe-doped mixed oxides derived from hydrotalcites.

    PubMed

    Ovejero, G; Rodríguez, A; Vallet, A; Gómez, P; García, J

    2011-01-01

    Catalytic wet air oxidation of Basic Yellow 11 (BY11), a basic dye, was studied in a batch reactor. Layered double hydroxides with the hydrotalcite-like structure containing nickel or iron cations have been prepared by coprecipitation and subsequently calcined leading to Ni- and Fe-doped mixed oxides, respectively. Compared with the results in the wet air oxidation of BY11, these catalysts showed high activity for total organic carbon (TOC), toxicity and dye removal at 120 degrees C and 50 bars after 120 min. It has been demonstrated that the activity depended strongly on the presence of catalyst. The results show that catalysts containing nickel provide a higher extent of oxidation of the dye whereas the reaction carried out with the iron catalyst is faster. The Ni and Fe dispersion determined from the TPR results was higher for the catalysts with a lower Ni or Fe content and decreased for higher Ni or Fe contents. On the basis of activity and selectivity, the Ni containing catalyst with the medium (3%) Ni content was found to be the best catalyst. Finally, a relationship between metal content of the catalyst and reaction rate has been established.

  16. Combination of coagulation and catalytic wet oxidation for the treatment of pulp and paper mill effluents.

    PubMed

    Verenich; Laari, A; Nissen, M; Kallas, J

    2001-01-01

    Wet oxidation (WO) is a well established process for purification of concentrated municipal and industrial wastewaters. Many attempts have been made to modify the WO process or to create a suitable combination of processes. This work was undertaken to investigate wet oxidation integrated with coagulation, i.e. to treat the sludge remaining after coagulation with a WO process. The possibility of regeneration of the used coagulant was also considered. Two waters from paper mills were used: TMP (thermomechanical pulp) circulation water and membrane concentrate. About 50% of the COD in the original water can be removed by coagulation using Fe2(SO4)3. The results from the wet oxidation experiments show the positive effect of iron in the chemical sludge as a catalyst. The efficiency of the WO process was enhanced almost by 100%. The remaining dissolved organic matter can be easily removed biologically.

  17. Wet hydrogen peroxide catalytic oxidation of phenol with FeAC (iron-embedded activated carbon) catalysts.

    PubMed

    Liou, Rey-May; Chen, Shih-Hsiung; Huang, Cheng-Hsien; Hung, Mu-Ya; Chang, Jing-Song; Lai, Cheng-Lee

    2010-01-01

    This investigation aims at exploring the catalytic oxidation activity of iron-embedded activated carbon (FeAC) and the application for the degradation of phenol in the wet hydrogen peroxide catalytic oxidation (WHPCO). FeAC catalysts were prepared by pre-impregnating iron in coconut shell with various iron loadings in the range of 27.5 to 46.5% before they were activated. The FeAC catalysts were characterised by measuring their surface area, pore distribution, functional groups on the surface, and X-ray diffraction patterns. The effects of iron loading strongly inhibited the pore development of the catalyst but benefited the oxidation activity in WHPCO. It was found that the complete conversion of phenol was observed with all FeAC catalysts in oxidation. High level of chemical oxygen demand (COD) abatement can be achieved within the first 30 minutes of oxidation. The iron embedded in the activated carbon showed good performance in the degradation and mineralisation of phenol during the oxidation due to the active sites as iron oxides formed on the surface of the activated carbon. It was found that the embedding irons were presented in gamma-Fe(2)O(3), alpha-Fe(2)O(3), and alpha-FeCOOH forms on the activated carbon. The aging tests on FeAC catalysts showed less activity loss, and less iron leaching was found after four oxidation runs.

  18. Active carbon-ceramic sphere as support of ruthenium catalysts for catalytic wet air oxidation (CWAO) of resin effluent.

    PubMed

    Liu, Wei-Min; Hu, Yi-Qiang; Tu, Shan-Tung

    2010-07-15

    Active carbon-ceramic sphere as support of ruthenium catalysts were evaluated through the catalytic wet air oxidation (CWAO) of resin effluent in a packed-bed reactor. Active carbon-ceramic sphere and ruthenium catalysts were characterized by N(2) adsorption and chemisorption measurements. BET surface area and total pore volume of active carbon (AC) in the active carbon-ceramic sphere increase with increasing KOH-to-carbon ratio, and AC in the sample KC-120 possesses values as high as 1100 m(2) g(-1) and 0.69 cm(3) g(-1) (carbon percentage: 4.73 wt.%), especially. Active carbon-ceramic sphere supported ruthenium catalysts were prepared using the RuCl(3) solution impregnation onto these supports, the ruthenium loading was fixed at 1-5 wt.% of AC in the support. The catalytic activity varies according to the following order: Ru/KC-120>Ru/KC-80>Ru/KC-60>KC-120>without catalysts. It is found that the 3 wt.% Ru/KC-120 catalyst displays highest stability in the CWAO of resin effluent during 30 days. Chemical oxygen demand (COD) and phenol removal were about 92% and 96%, respectively at the reaction temperature of 200 degrees C, oxygen pressure of 1.5 MPa, the water flow rate of 0.75 L h(-1) and the oxygen flow rate of 13.5 L h(-1).

  19. Treatment of municipal landfill leachate by catalytic wet air oxidation: Assessment of the role of operating parameters by factorial design

    SciTech Connect

    Anglada, Angela; Urtiaga, Ane; Ortiz, Inmaculada; Diamadopoulos, Evan

    2011-08-15

    Highlights: > Landfill leachates can be treated effectively by catalytic wet oxidation. > Addition of H{sub 2}O{sub 2} in the presence of transition metals promotes degradation. > Factorial design evaluates the statistically significant operating conditions. > H{sub 2}O{sub 2}, reaction time and temperature are critical in determining performance. - Abstract: The wet air oxidation (WAO) of municipal landfill leachate catalyzed by cupric ions and promoted by hydrogen peroxide was investigated. The effect of operating conditions such as WAO treatment time (15-30 min), temperature (160-200 deg. C), Cu{sup 2+} concentration (250-750 mg L{sup -1}) and H{sub 2}O{sub 2} concentration (0-1500 mg L{sup -1}) on chemical oxygen demand (COD) removal was investigated by factorial design considering a two-stage, sequential process comprising the heating-up of the reactor and the actual WAO. The leachate, at an initial COD of 4920 mg L{sup -1}, was acidified to pH 3 leading to 31% COD decrease presumably due to the coagulation/precipitation of colloidal and other organic matter. During the 45 min long heating-up period of the WAO reactor under an inert atmosphere, COD removal values up to 35% (based on the initial COD value) were recorded as a result of the catalytic decomposition of H{sub 2}O{sub 2} to reactive hydroxyl radicals. WAO at 2.5 MPa oxygen partial pressure advanced treatment further; for example, 22 min of oxidation at 200 deg. C, 250 mg L{sup -1} Cu{sup 2+} and 0-1500 mg L{sup -1} H{sub 2}O{sub 2} resulted in an overall (i.e. including acidification and heating-up) COD reduction of 78%. Amongst the operating variables in question, temperature had the strongest influence on both the heating-up and WAO stages, while H{sub 2}O{sub 2} concentration strongly affected the former and reaction time the latter. Nonetheless, the effects of temperature and H{sub 2}O{sub 2} concentration were found to depend on the concentration levels of catalyst as suggested by the

  20. Low-temperature catalytic gasification of wet industrial wastes. FY 1991--1992 interim report

    SciTech Connect

    Elliott, D.C.; Neuenschwander, G.G.; Hart, T.R.; Phelps, M.R.; Sealock, L.J. Jr.

    1993-07-01

    A catalytic gasification system operating in a pressurized water environment has been developed and refined at Pacific Northwest Laboratory (PNL) for over 12 years. Initial experiments were aimed at developing kinetics information for steam gasification of biomass in the presence of catalysts. The combined use of alkali and metal catalysts was reported for gasification of biomass and its components at low temperatures (350{degrees}C to 450{degrees}C). From the fundamental research evolved the concept of a pressurized, catalytic gasification system for converting wet biomass feedstocks to fuel gas. Extensive batch reactor testing and limited continuous reactor system (CRS) testing were undertaken in the development of this system under sponsorship of the US Department of Energy. A wide range of biomass feedstocks were tested, and the importance of the nickel metal catalyst was identified. Specific use of this process for treating food processing wastes was also studied. The concept application was further expanded to encompass cleanup of hazardous wastewater streams, and results were reported for batch reactor tests and continuous reactor tests. Ongoing work at PNL focuses on refining the catalyst and scaling the system to long-term industrial needs. The process is licensed as the Thermochemical Environmental Energy System (TEES{reg_sign}) to Onsite*Ofsite, Inc., of Duarte, California. This report is a follow-on to the 1989--90 interim report [Elliott et al. 1991], which reviewed the results of the studies conducted with a fixed-bed, continuous-feed, tubular reactor. The discussion here provides an overview of experiments on the wide range of potential feedstock materials conducted in a batch reactor; development of new catalyst materials; and tests performed in continuous-flow reactors at three scales. The appendices contain the history and background of the process development, as well as more detailed descriptions and results of the recent studies.

  1. Low-pressure catalytic wet-air oxidation of a high-strength industrial wastewater using Fenton's reagent.

    PubMed

    Biçaksiz, Zeliha; Aytimur, Gülin; Atalay, Süheyda

    2008-06-01

    Wastewater from the Afyon Alkaloids Factory (Afyon, Turkey) was subjected to low-pressure catalytic wet-air oxidation (CWAO) using Fenton's reagent, and the optimal reaction conditions were investigated. The CWAO using Fenton's reagent was applied to the factory effluent, diluted factory effluent, and aerobically pretreated wastewater. To find the optimum quantities of reagents, ferrous iron (Fe(+2))-to-substrate ratios of 1:10, 1:25, and 1:50 and hydrogen peroxide (H2O2)-to-Fe(+2) ratios of 1, 5, and 10 were investigated, and the treatment was carried out at different temperatures. High chemical oxygen demand (COD) removals were obtained at 50 degrees C, with the Fe(+2)-to-substrate ratio range between 1:10 and 1:25. The change in H2O2-to-Fe(+2) ratios did not cause any considerable effect. Also, the percentages of COD removals were nearly the same, so the ratio H2O2:Fe(+2):1 is recommended. Aerobic pretreatment seems to be effective. On the other hand, no enhancement was observed in the case of the diluted wastewater.

  2. Conversion and Estrogenicity of 17β-estradiol During Photolytic/Photocatalytic Oxidation and Catalytic Wet-air Oxidation.

    PubMed

    Bistan, Mirjana; Tišler, Tatjana; Pintar, Albin

    2012-06-01

    Estrogen 17β-estradiol (E2), produced by human body and excreted into municipal wastewaters, belongs to the group of endocrine disrupting compounds that are resistant to biological degradation. The aim of this study was to assess the efficiency of E2 removal from aqueous solutions by means of catalytic wet-air oxidation (CWAO) and photolytic/photocatalytic oxidation. CWAO experiments were conducted in a trickle-bed reactor at temperatures up to 230 °C and oxygen partial pressure of 10 bar over TiO2 and Ru/TiO2 solids. Photolytic/photocatalytic oxidation was carried out in a batch slurry reactor employing a TiO2 P-25 (Degussa) catalyst under visible or UV light. HPLC analysis and yeast estrogen screen assay were used to evaluate the removal of E2 and estrogenicity of treated samples. The latter was completely removed during photolytic/photocatalytic oxidation under UV (365 nm) light and photocatalytic oxidation under visible light. In CWAO experiments, complete removal of both E2 and estrogenicity from the feed solution were noticed in the presence of TiO2 and Ru/TiO2 catalysts.

  3. Treatment of printing and dyeing wastewater by catalytic wet hydrogen peroxide oxidation of honeycomb cinder as carrier catalyst

    NASA Astrophysics Data System (ADS)

    Zhang, D. H.; Yang, H. M.; Ou, Y. J.; Xu, C.; Gu, J. C.

    2017-06-01

    Under the condition of 35 °C, honeycomb cinder was used as the carrier, nickel as the active ingredient, impregnated for 2h, and calcined at 300 °C for 2h. The catalyst was used to Catalytic Wet Peroxide Oxidation of methylene blue simulated printing and dyeing wastewater. The effect of the amount of catalyst, the amount of catalyst, the reaction temperature and the reaction time on the treatment efficiency and the effect of the self-made catalyst on the simulated wastewater with different concentration gradient were studied in the experiment. The results showed that when the reaction conditions were H2O2 8ml/L, catalyst 12g/L and reaction time 1h, the degradation rate of methylene blue reached more than 77% for the wastewater with concentration ranging from 40 mg/L to 200 mg/L. In addition, at a temperature of 30 DEG C, the wastewater, the concentration was 80mg/L, degradation rate was up to 85.70%.

  4. Reactive wetting properties of TiO2 nanoparticles predicted by ab initio molecular dynamics simulations.

    PubMed

    Brandt, Erik G; Agosta, Lorenzo; Lyubartsev, Alexander P

    2016-07-21

    Small-sized wet TiO2 nanoparticles have been investigated by ab initio molecular dynamics simulations. Chemical and physical adsorption of water on the TiO2-water interface was studied as a function of water content, ranging from dry nanoparticles to wet nanoparticles with monolayer coverage of water. The surface reactivity was shown to be a concave function of water content and driven by surface defects. The local coordination number at the defect was identified as the key factor to decide whether water adsorption proceeds through dissociation or physisorption on the surface. A consistent picture of TiO2 nanoparticle wetting at the microscopic level emerges, which corroborates existing experimental data and gives further insight into the molecular mechanisms behind nanoparticle wetting. These calculations will facilitate the engineering of metal oxide nanoparticles with a controlled catalytic water activity.

  5. Synthesis and catalytic properties of silver nanoparticles supported on porous cellulose acetate sheets and wet-spun fibers.

    PubMed

    Kamal, Tahseen; Ahmad, Ikram; Khan, Sher Bahadar; Asiri, Abdullah M

    2017-02-10

    Cellulose acetate fibers (CAfiber), and sheets (CAsheet) were prepared by wet-spinning, and doctor blade methods, respectively. For CAfiber, the CA-acetone solution was pushed through narrow orifice of the medical syringe into a coagulating bath containing water. The same polymer solution was used for the fabrication of CAsheet. The prepared CAfiber and CAsheet were dipped in a 0.1M aqueous AgNO3 solution followed by treatment with 0.1M NaBH4 aqueous solution to synthesize the Ag nanoparticles over stated substrates. The virgin CAfiber and CAsheet as well as Ag nanoparticles containing samples (Ag/CAfiber and Ag/CAsheet) were characterized by FE-SEM, XRD, FTIR, and TGA. These materials were tested as catalysts in hydrogenation of the 2,6-dinitrophenol (2,6-DNP) by NaBH4. The Ag/CAfiber played better catalytic role in the hydrogenation of 2,6-DNP as compared to the Ag/CAsheet. Moreover, the catalyst amount effect on the reaction rate constant, ease of separation and reusability of the prepared materials were discussed.

  6. Treatment of municipal landfill leachate by catalytic wet air oxidation: Assessment of the role of operating parameters by factorial design.

    PubMed

    Anglada, Angela; Urtiaga, Ane; Ortiz, Inmaculada; Mantzavinos, Dionissios; Diamadopoulos, Evan

    2011-08-01

    The wet air oxidation (WAO) of municipal landfill leachate catalyzed by cupric ions and promoted by hydrogen peroxide was investigated. The effect of operating conditions such as WAO treatment time (15-30min), temperature (160-200°C), Cu(2+) concentration (250-750mgL(-1)) and H(2)O(2) concentration (0-1500mgL(-1)) on chemical oxygen demand (COD) removal was investigated by factorial design considering a two-stage, sequential process comprising the heating-up of the reactor and the actual WAO. The leachate, at an initial COD of 4920mgL(-1), was acidified to pH 3 leading to 31% COD decrease presumably due to the coagulation/precipitation of colloidal and other organic matter. During the 45min long heating-up period of the WAO reactor under an inert atmosphere, COD removal values up to 35% (based on the initial COD value) were recorded as a result of the catalytic decomposition of H(2)O(2) to reactive hydroxyl radicals. WAO at 2.5MPa oxygen partial pressure advanced treatment further; for example, 22min of oxidation at 200°C, 250mgL(-1) Cu(2+) and 0-1500mgL(-1) H(2)O(2) resulted in an overall (i.e. including acidification and heating-up) COD reduction of 78%. Amongst the operating variables in question, temperature had the strongest influence on both the heating-up and WAO stages, while H(2)O(2) concentration strongly affected the former and reaction time the latter. Nonetheless, the effects of temperature and H(2)O(2) concentration were found to depend on the concentration levels of catalyst as suggested by the significance of their 3rd order interaction term.

  7. Enhanced wet hydrogen peroxide catalytic oxidation performances based on CuS nanocrystals/reduced graphene oxide composites

    NASA Astrophysics Data System (ADS)

    Qian, Jing; Wang, Kun; Guan, Qingmeng; Li, Henan; Xu, Hui; Liu, Qian; Liu, Wei; Qiu, Baijing

    2014-01-01

    CuS nanocrystals/reduced graphene oxide (CuS NCs/rGO) composites were prepared by a facile one-pot solvothermal reaction. In this solvothermal system, thioacetamide was found to perform the dual roles of sulphide source and reducing agent, resulting in the formation of CuS NCs and simultaneous reduction of graphene oxide (GO) sheets to rGO sheets. In addition, CuS NCs/rGO composites were further used as heterogeneous catalysts in the wet hydrogen peroxide catalytic oxidation process, with methylene blue as a model organic dye. The introduction of rGO to CuS NCs could effectively enhance the catalytic activity of CuS NCs, and the resultant CuS NCs/rGO composites with a starting GO amount of 5 wt% showed the highest catalytic activity. Furthermore, the CuS NCs/rGO composites showed high catalytic activity over a broad pH operation range from 3.0 to 11.0 under ambient conditions, and still retained 90% of the original catalytic activity after reuse in five cycles.

  8. Gene targeting of CK2 catalytic subunits

    PubMed Central

    Lou, David Y.; Toselli, Paul; Landesman-Bollag, Esther; Dominguez, Isabel

    2013-01-01

    Protein kinase CK2 is a highly conserved and ubiquitous serine–threonine kinase. It is a tetrameric enzyme that is made up of two regulatory CK2β subunits and two catalytic subunits, either CK2α/CK2α, CK2α/ CK2α′, or CK2α′/CK2α′. Although the two catalytic subunits diverge in their C termini, their enzymatic activities are similar. To identify the specific function of the two catalytic subunits in development, we have deleted them individually from the mouse genome by homologous recombination. We have previously reported that CK2α′is essential for male germ cell development, and we now demonstrate that CK2α has an essential role in embryogenesis, as mice lacking CK2α die in mid-embryogenesis, with cardiac and neural tube defects. PMID:18594950

  9. Unprecedented Catalytic Wet Oxidation of Glucose to Succinic Acid Induced by the Addition of n-Butylamine to a Ru(III) Catalyst.

    PubMed

    Podolean, Iunia; Rizescu, Cristina; Bala, Camelia; Rotariu, Lucian; Parvulescu, Vasile I; Coman, Simona M; Garcia, Hermenegildo

    2016-09-08

    A new pathway for the catalytic wet oxidation (CWO) of glucose is described. Employing a cationic Ru@MNP catalyst, succinic acid is obtained in unprecedently high yield (87.5 %) for a >99.9 % conversion of glucose, most probably through a free radical mechanism combined with catalytic didehydroxylation of vicinal diols and hydrogenation of the resulted unsaturated intermediate.

  10. Catalytic wet peroxide oxidation of aniline in wastewater using copper modified SBA-15 as catalyst.

    PubMed

    Kong, Liming; Zhou, Xiang; Yao, Yuan; Jian, Panming; Diao, Guowang

    2016-01-01

    SBA-15 mesoporous molecular sieves modified with copper (Cu-SBA-15) were prepared by pH-adjusting hydrothermal method and characterized by X-ray diffraction, BET, transmission electron microscopy, UV-Vis and (29)Si MAS NMR. The pH of the synthesis gel has a significant effect on the amount and the dispersion of copper on SBA-15. The Cu-SBA-15(4.5) (where 4.5 denotes the pH value of the synthesis gel) modified with highly dispersed copper was used as catalyst for the oxidation of aniline by H2O2. The Cu-SBA-15(4.5) shows a higher catalytic activity compared to CuO on the surface of SBA-15. The influences of reaction conditions, such as initial pH of the aqueous solutions, temperature, as well as the dosages of H2O2 and catalyst were investigated. Under weakly alkaline aqueous solution conditions, the aniline conversion, the H2O2 decomposition and the total organic carbon (TOC) removal could be increased significantly compared to the acid conditions. The percentage of leaching Cu(2+) could be decreased from 45.0% to 3.66% when the initial pH of solution was increased from 5 to 10. The TOC removal could be enhanced with the increases of temperature, H2O2 and catalyst dosage, but the aniline conversion and H2O2 decomposition change slightly with further increasing dosage of catalyst and H2O2. At 343 K and pH 8.0, 100% aniline conversion and 66.9% TOC removal can be achieved under the conditions of 1.0 g/L catalyst and 0.05 mol/L H2O2 after 180 min. Although copper might be slightly leached from catalyst, the homogeneous Cu(2+) contribution to the whole catalytic activity is unimportant, and the highly dispersed copper on SBA-15 plays a dominant role.

  11. Reuse of a dyehouse effluent after being treated with the combined catalytic wet peroxide oxidation process and the aerated constructed wetland.

    PubMed

    Lee, D K; Kim, S C; Yoon, J H

    2007-01-01

    A catalytic wet peroxide oxidation process was combined with the aerated constructed wetland in order to treat the raw dyehouse wastewater to in acceptable level for reuse as washing process water. More than 90% of BOD and CODs could be removed with the wet peroxide oxidation reactor and the remaining pollutants in the treated water were transformed into biodegradable ones which could have been successfully treated at the following aerated constructed wetland. The highest values of BOD5, CODMn, CODCr, SS and T-N in the treated water were 1.6, 1.8, 2.1, 0.5 and 12.8 mg/L, respectively. These values were low enough for the treated water to be reused at the washing process.

  12. Inhibition and deactivation effects in catalytic wet oxidation of high-strength alcohol-distillery liquors

    SciTech Connect

    Belkacemi, K.; Larachi, F.; Hamoudi, S.; Turcotte, G.; Sayari, A.

    1999-06-01

    The removal efficiency of total organic carbon (TOC) from raw high-strength alcohol-distillery waste liquors was evaluated using three different treatments: thermolysis (T), noncatalytic wet oxidation (WO), and solid-catalyzed wet oxidation (CWO). The distillery liquors (TOC = 22,500 mg/l, sugars = 18,000 mg/l, and proteins = 13,500 mg/l) were produced by alcoholic fermentation of enzymatic hydrolyzates from steam-exploded timothy grass. TOC-abatement studies were conducted batchwise in a stirred autoclave to evaluate the influence of the catalyst (7:3, MnO{sub 2}/CeO{sub 2} mixed oxide), oxygen partial pressure (0.5--2.5 MPa), and temperature (453--523 K) on T, WO, and CWO processes. Although CWO outperformed T and WO, TOC conversions did not exceed {approximately}60% at the highest temperature used. Experiments provided prima facie evidence for a gradual fouling of the catalyst and a developing inhibition in the liquors which impaired deep TOC removals. Occurrence of catalyst deactivation by carbonaceous deposits was proven experimentally through quantitative and qualitative experiments such as elemental analysis and X-ray photoelectron spectroscopy. Inhibition toward further degradation of the liquors was ascribed to the occurrence of highly stable antioxidant intermediates via the Maillard reactions between dissolved sugars and proteins. A lumping kinetic model involving both reaction inhibition by dissolved intermediates and catalyst deactivation by carbonaceous deposits was proposed to account for the distribution of carbon in the liquid, solid, and the vapor phases.

  13. Relative influence of process variables during non-catalytic wet oxidation of municipal sludge.

    PubMed

    Baroutian, Saeid; Smit, Anne-Marie; Gapes, Daniel James

    2013-11-01

    Individual and interactive effects of process variables on the degradation of fermented municipal sludge were examined during wet oxidation. The process was carried out at 220-240°C using 1:1-2:1 oxygen to biomass ratio and 300-500 rpm stirring speed. Response surface methodology coupled with a faced-centred central composite design was used to evaluate the effect of these variables on total suspended solids, volatile suspended solids and total chemical oxygen demand. Multivariate analysis was conducted for the initial and near completion stages of reaction: 5 and 60 min treatments, respectively. Temperature had the most significant effect on degradation rate throughout. During the initial stage the effect of mixing intensity was less significant than that of oxygen ratio. Mixing intensity did not influence degradation rate at the later stage in the process. During the near completion stage, the interaction of temperature and oxygen ratio had significant effect on sludge degradation.

  14. Toxicity to Daphnia magna and Vibrio fischeri of Kraft bleach plant effluents treated by catalytic wet-air oxidation.

    PubMed

    Pintar, Albin; Besson, Michèle; Gallezot, Pierre; Gibert, Janine; Martin, Dominique

    2004-01-01

    Two Kraft-pulp bleaching effluents from a sequence of treatments which include chlorine dioxide and caustic soda were treated by catalytic wet-air oxidation (CWAO) at T=463 K in trickle-bed and batch-recycle reactors packed with either TiO2 extrudates or Ru(3 wt%)/TiO2 catalyst. Chemical analyses (TOC removal, color, HPLC) and bioassays (48-h and 30-min acute toxicity tests using Daphnia magna and Vibrio fischeri, respectively) were used to get information about the toxicity impact of the starting effluents and of the treated solutions. Under the operating conditions, complex organic compounds are mostly oxidized into carbon dioxide and water, along with short-chain carboxylic acids. Bioassays were found as a complement to chemical analyses for ensuring the toxicological impact on the ecosystem. In spite of a large decrease of TOC, the solutions of end products were all more toxic to Daphnia magna than the starting effluents by factors ranging from 2 to 33. This observation is attributed to the synergistic effects of acetic acid and salts present in the solutions. On the other hand, toxicity reduction with respect to Vibrio fischeri was achieved: detoxification factors greater than unity were measured for end-product solutions treated in the presence of the Ru(3 wt%)/TiO2 catalyst, suggesting the absence of cumulative effect for this bacteria, or a lower sensitivity to the organic acids and salts. Bleach plant effluents treated by the CWAO process over the Ru/TiO2 catalyst were completely biodegradable.

  15. Photo-catalytic activity of Zn1-xMnxS nanocrystals synthesized by wet chemical technique

    PubMed Central

    2011-01-01

    Polyvinyl pyrrolidone capped Zn1-xMnxS (0 ≤ x ≤ 0.1) nanocrystals have been synthesized using wet chemical co-precipitation method. Crystallographic and morphological characterization of the synthesized materials have been done using X-ray diffraction and transmission electron microscope. Crystallographic studies show the zinc blende crystals having average crystallite size approx. 3 nm, which is almost similar to the average particle size calculated from electron micrographs. Atomic absorption spectrometer has been used for qualitative and quantitative analysis of synthesized nanomaterials. Photo-catalytic activity has been studied using methylene blue dye as a test contaminant. Energy resolved luminescence spectra have been recorded for the detailed description of radiative and non-radiative recombination mechanisms. Photo-catalytic activity dependence on dopant concentration and luminescence quantum yield has been studied in detail. PMID:21711502

  16. Bench-scale reactor tests of low-temperature, catalytic gasification of wet, industrial wastes

    SciTech Connect

    Elliott, D.C.; Neuenschwander, G.G.; Baker, E.G.; Butner, R.S.; Sealock, L.J.

    1990-04-01

    Bench-scale reactor tests are under way at Pacific Northwest Laboratory to develop a low-temperature, catalytic gasification system. The system, licensed under the trade name Thermochemical Environmental Energy System (TEES{reg sign}), is designed for to a wide variety of feedstocks ranging from dilute organics in water to waste sludges from food processing. The current research program is focused on the use of a continuous-feed, tubular reactor. The catalyst is nickel metal on an inert support. Typical results show that feedstocks such as solutions of 2% para-cresol or 5% and 10% lactose in water or cheese whey can be processed to >99% reduction of chemical oxygen demand (COD) at a rate of up to 2 L/hr. The estimated residence time is less than 5 min at 360{degree}C and 3000 psig, not including 1 to 2 min required in the preheating zone of the reactor. The liquid hourly space velocity has been varied from 1.8 to 2.9 L feedstock/L catalyst/hr depending on the feedstock. The product fuel gas contains 40% to 55% methane, 35% to 50% carbon dioxide, and 5% to 10% hydrogen with as much as 2% ethane, but less than 0.1% ethylene or carbon monoxide, and small amounts of higher hydrocarbons. The byproduct water stream carries residual organics amounting to less than 500 mg/L COD. 9 refs., 1 fig., 4 tabs.

  17. A kinetic model of municipal sludge degradation during non-catalytic wet oxidation.

    PubMed

    Prince-Pike, Arrian; Wilson, David I; Baroutian, Saeid; Andrews, John; Gapes, Daniel J

    2015-12-15

    Wet oxidation is a successful process for the treatment of municipal sludge. In addition, the resulting effluent from wet oxidation is a useful carbon source for subsequent biological nutrient removal processes in wastewater treatment. Owing to limitations with current kinetic models, this study produced a kinetic model which predicts the concentrations of key intermediate components during wet oxidation. The model was regressed from lab-scale experiments and then subsequently validated using data from a wet oxidation pilot plant. The model was shown to be accurate in predicting the concentrations of each component, and produced good results when applied to a plant 500 times larger in size. A statistical study was undertaken to investigate the validity of the regressed model parameters. Finally the usefulness of the model was demonstrated by suggesting optimum operating conditions such that volatile fatty acids were maximised.

  18. Chemical and toxicological evaluation of an emerging pollutant (enrofloxacin) by catalytic wet air oxidation and ozonation in aqueous solution.

    PubMed

    Li, Yan; Zhang, Feifang; Liang, Xinmiao; Yediler, Ayfer

    2013-01-01

    This study evaluates the degradation efficiency of enrofloxacin (ENR) by catalytic wet air oxidation (CWAO) and ozonation. Results obtained by CWAO experiments show that 99.5% degradation, 37.0% chemical oxidation demand (COD) removal and 51.0% total organic carbon (TOC) conversion were obtained when 100 mol% FeCl(3) and 25 mol% NaNO(2) at 150 °C under 0.5 MPa oxygen pressure after 120 min are used. The degradation products are identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS), gas chromatography-mass spectrometry (GC-MS) and ion chromatography (IC). The oxidation end products, F(-), NO(3)(-) and NH(4)(+) were determined by IC. The BOD(5)/COD ratio as a measure of the biodegradability of the parent compound increased from 0.01 to 0.12 after 120 min of reaction time, indicating an improved biodegradability of the parent compound. The inhibition of bioluminescence of the marine bacteria V. fischeri decreased from 43% to 12% demonstrating a loss in toxicity of ENR during CWAO. Ozonation of 0.2 mM ENR was carried out with an ozone concentration of 7.3 g m(-3) at pH 7. ENR decomposition with a degradation rate of 87% was obtained corresponding to the reaction time. Moderate changes in COD (18%) and TOC (17%) removal has been observed. The bioluminescence inhibition increased from 8% to 50%, due to the generation of toxic degradation products during ozonation. In comparison to the widely use of well developed method of ozonation CWAO exhibits better performance in terms of COD, TOC removals and generates less toxic products. Copyright © 2012 Elsevier Ltd. All rights reserved.

  19. Catalytic wet air oxidation of coke-plant wastewater on ruthenium-based eggshell catalysts in a bubbling bed reactor.

    PubMed

    Yang, M; Sun, Y; Xu, A H; Lu, X Y; Du, H Z; Sun, C L; Li, C

    2007-07-01

    Catalytic wet air of coke-plant wastewater was studied in a bubbling bed reactor. Two types of supported Ru-based catalysts, eggshell and uniform catalysts, were employed. Compared with the results in the wet air oxidation of coke-plant wastewater, supported Ru uniform catalysts showed high activity for chemical oxygen demand (COD) and ammonia/ammonium compounds (NH3-N) removal at temperature of 250 degrees C and pressure of 4.8 MPa, and it has been demonstrated that the catalytic activity of uniform catalyst depended strongly on the distribution of active sites of Ru on catalyst. Compared to the corresponding uniform catalysts with the same Ru loading (0.25 wt.% and 0.1 wt.%, respectively), the eggshell catalysts showed higher activities for CODcr removal and much higher activities for NH3-N degradation. The high activity of eggshell catalyst for treatment of coke-plant wastewater can be attributed to the higher density of active Ru sites in the shell layer than that of the corresponding uniform catalyst with the same Ru loading. It has been also evidenced that the active Ru sites in the internal core of uniform catalyst have very little or no contribution to CODcr and NH3-N removal in the total oxidation of coke-plant wastewater.

  20. Development of the Monolith Froth Reactor for Catalytic Wet Oxidation of CELSS Model Wastes

    NASA Technical Reports Server (NTRS)

    Fisher, John W.; Abraham, Martin

    1993-01-01

    The aqueous phase oxidation of acetic acid, used as a model compound for the treatment of CELSS (Controlled Ecological Life Support System) waste, was carried out in the monolith froth reactor which utilizes two-phase flow in the monolith channels. The catalytic oxidation of acetic acid was carried out over a Pt/Al2O3 catalyst at temperatures and pressures below the critical point of water. The effect of externally controllable parameters (temperature, liquid flow rate, distributor plate orifice size, pitch, and catalyst distance from the distributor plate) on the rate of acetic acid oxidation was investigated. Results indicate reaction rate increased with increasing temperature and exhibited a maximum with respect to liquid flow rate. The apparent activation energy calculated from reaction rate data was 99.7 kJ/mol. This value is similar to values reported for the oxidation of acetic acid in other systems and is comparable to intrinsic values calculated for oxidation reactions. The kinetic data were modeled using simple power law kinetics. The effect of "froth" feed system characteristics was also investigated. Results indicate that the reaction rate exhibits a maximum with respect to distributor plate orifice size, pitch, and catalyst distance from the distributor plate. Fundamental results obtained were used to extrapolate where the complete removal of acetic acid would be obtained and for the design and operation of a full scale CELSS treatment system.

  1. Development of the Monolith Froth Reactor for Catalytic Wet Oxidation of CELSS Model Wastes

    NASA Technical Reports Server (NTRS)

    Abraham, Martin; Fisher, John W.

    1995-01-01

    The aqueous phase oxidation of acetic acid, used as a model compound for the treatment of CELSS (Controlled Ecological Life Support System) waste, was carried out in the monolith froth reactor which utilizes two-phase flow in the monolith channels. The catalytic oxidation of acetic acid was carried out over a Pt/Al2O3 catalyst, prepared at The University of Tulsa, at temperatures and pressures below the critical point of water. The effect of externally controllable parameters (temperature, liquid flow rate, distributor plate orifice size, pitch, and catalyst distance from the distributor plate) on the rate of acetic acid oxidation was investigated. Results indicate reaction rate increased with increasing temperature and exhibited a maximum with respect to liquid flow rate. The apparent activation energy calculated from reaction rate data was 99.7 kJ/mol. This value is similar to values reported for the oxidation of acetic acid in other systems and is comparable to intrinsic values calculated for oxidation reactions. The kinetic data were modeled using simple power law kinetics. The effect of "froth" feed system characteristics was also investigated. Results indicate that the reaction rate exhibits a maximum with respect to distributor plate orifice size, pitch, and catalyst distance from the distributor plate. Fundamental results obtained were used to extrapolate where the complete removal of acetic acid would be obtained and for the design and operation of a full scale CELSS treatment system.

  2. Low-temperature catalytic gasification of wet industrial wastes. FY 1993--1994 interim report

    SciTech Connect

    Elliott, D.C.; Hart, T.R.; Neuenschwander, G.G.; Deverman, G.S.; Werpy, T.A.; Phelps, M.R.; Baker, E.G.; Sealock, L.J. Jr.

    1995-03-01

    Process development research is continuing on a low-temperature, catalytic gasification system that has been demonstrated to convert organics in water (dilute or concentrated) to useful and environmentally safe gases. The system, licensed under the trade name Thermochemical Environmental Energy System (TEESO), treats a wide variety of feedstocks ranging from hazardous organics in water to waste sludges from food processing. The current research program is focused on the use of continuous-feed, tubular reactors systems for testing catalysts and feedstocks in the process. A range of catalysts have been tested, including nickel and other base metals, as well as ruthenium and other precious metals. Results of extensive testing show that feedstocks, ranging from 2% para-cresol in water to potato waste and spent grain, can be processed to > 99% reduction of chemical oxygen demand (COD). The product fuel gas contains from 40% up to 75% methane, depending on the feedstock. The balance of the gas is mostly carbon dioxide with < 5% hydrogen and usually < 1% ethane and higher hydrocarbons. The byproduct water stream carries residual organics from 10 to 1,000 mg/l COD, depending on the feedstock. The level of development of TEES has progressed to the initial phases of industrial process demonstration. Testing of industrial waste streams is under way at both the bench scale and engineering scale of development.

  3. Project WET Curriculum and Activity Guide 2.0

    ERIC Educational Resources Information Center

    Project WET Foundation, 2011

    2011-01-01

    The "Project WET Curriculum and Activity Guide 2.0" continues Project WET's dedication to 21st-century, cutting-edge water education. Now in full color, Guide 2.0 offers new activities on topics such as National Parks and storm water, fully revised and updated activities from the original Guide and the very best activities gathered from all of…

  4. Project WET Curriculum and Activity Guide 2.0

    ERIC Educational Resources Information Center

    Project WET Foundation, 2011

    2011-01-01

    The "Project WET Curriculum and Activity Guide 2.0" continues Project WET's dedication to 21st-century, cutting-edge water education. Now in full color, Guide 2.0 offers new activities on topics such as National Parks and storm water, fully revised and updated activities from the original Guide and the very best activities gathered from all of…

  5. Development of a Catalytic Wet Air Oxidation Method to Produce Feedstock Gases from Waste Polymers

    NASA Technical Reports Server (NTRS)

    Kulis, Michael J.; Guerrero-Medina, Karen J.; Hepp, Aloysius F.

    2012-01-01

    Given the high cost of space launch, the repurposing of biological and plastic wastes to reduce the need for logistical support during long distance and long duration space missions has long been recognized as a high priority. Described in this paper are the preliminary efforts to develop a wet air oxidation system in order to produce fuels from waste polymers. Preliminary results of partial oxidation in near supercritical water conditions are presented. Inherent corrosion and salt precipitation are discussed as system design issues for a thorough assessment of a second generation wet air oxidation system. This work is currently being supported by the In-Situ Resource Utilization Project.

  6. Reactive wetting properties of TiO2 nanoparticles predicted by ab initio molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Brandt, Erik G.; Agosta, Lorenzo; Lyubartsev, Alexander P.

    2016-07-01

    Small-sized wet TiO2 nanoparticles have been investigated by ab initio molecular dynamics simulations. Chemical and physical adsorption of water on the TiO2-water interface was studied as a function of water content, ranging from dry nanoparticles to wet nanoparticles with monolayer coverage of water. The surface reactivity was shown to be a concave function of water content and driven by surface defects. The local coordination number at the defect was identified as the key factor to decide whether water adsorption proceeds through dissociation or physisorption on the surface. A consistent picture of TiO2 nanoparticle wetting at the microscopic level emerges, which corroborates existing experimental data and gives further insight into the molecular mechanisms behind nanoparticle wetting. These calculations will facilitate the engineering of metal oxide nanoparticles with a controlled catalytic water activity.Small-sized wet TiO2 nanoparticles have been investigated by ab initio molecular dynamics simulations. Chemical and physical adsorption of water on the TiO2-water interface was studied as a function of water content, ranging from dry nanoparticles to wet nanoparticles with monolayer coverage of water. The surface reactivity was shown to be a concave function of water content and driven by surface defects. The local coordination number at the defect was identified as the key factor to decide whether water adsorption proceeds through dissociation or physisorption on the surface. A consistent picture of TiO2 nanoparticle wetting at the microscopic level emerges, which corroborates existing experimental data and gives further insight into the molecular mechanisms behind nanoparticle wetting. These calculations will facilitate the engineering of metal oxide nanoparticles with a controlled catalytic water activity. Electronic supplementary information (ESI) available: Simulation data on equilibration of energies and structures (root-mean-square-deviations and

  7. Thermodynamic and kinetic study of phenol degradation by a non-catalytic wet air oxidation process.

    PubMed

    Lefèvre, Sébastien; Boutin, Olivier; Ferrasse, Jean-Henry; Malleret, Laure; Faucherand, Rémy; Viand, Alain

    2011-08-01

    This work is dedicated to an accurate evaluation of thermodynamic and kinetics aspects of phenol degradation using wet air oxidation process. Phenol is a well known polluting molecule and therefore it is important having data of its behaviour during this process. A view cell is used for the experimental study, with an internal volume of 150 mL, able to reach pressures up to 30 MPa and temperatures up to 350°C. Concerning the thermodynamic phase equilibria, experimental and modelling results are obtained for different binary systems (water/nitrogen, water/air) and ternary system (water/nitrogen/phenol). The best model is the Predictive Soave Redlich Kwong one. This information is necessary to predict the composition of the gas phase during the process. It is also important for an implementation in a process simulation. The second part is dedicated to kinetics evaluation of the degradation of phenol. Different compounds have been detected using GC coupled with a MS. A kinetic scheme is deduced, taking into account the evolution of phenol, hydroquinones, catechol, resorcinol and acetic acid. The kinetic parameters are calculated for this scheme. These data are important to evaluate the evolution of the concentration of the different polluting molecules during the process. A simplified kinetic scheme, which can be easily implemented in a process simulation, is also determined for the direct degradation of phenol into H(2)O and CO(2). The Arrhenius law data obtained for the phenol disappearance are the following: k=1.8×10(6)±3.9×10(5)M(-1)s(-1) (pre-exponential factor) and E(a)=77±8 kJ mol(-1) (activation energy).

  8. Catalytic wet air oxidation of phenol over Co-doped Fe3O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Song, Xu Chun; Zheng, Yi Fan; Yin, Hao Yong

    2013-08-01

    The Fe3O4 nanoparticles doped with cobalt ions have been successfully synthesized by the co-precipitation process. The X-ray diffraction, inductively coupled plasma, scanning electron microscopy, and transmission electron microscopy were used to characterize the as-prepared nanoparticles. The results show that the phase structure of the nanoparticles is spinel structure of pure Fe3O4 with the particle size ranging from 40 to 50 nm. The Co-doping concentration can be controlled by changing the atomic ratio of the stock materials. The catalytic activity of the Co-doped Fe3O4 was further investigated by decomposing the phenol in liquid phase. The results show that cobalt ions doping can improve the catalytic efficiency of Fe3O4 nanoparticles in phenol degradation with catalytic reaction fitting the first-order kinetics. According to the estimated reaction rate of Co-doped Fe3O4 nanoparticles at different temperatures, the activation energy was calculated to be 45.63 kJ/mol.

  9. WetLab-2: Wet Lab RNA SmartCycler Providing PCR Capability on ISS

    NASA Technical Reports Server (NTRS)

    Parra, Macarena; Schonfeld, Julie

    2015-01-01

    The WetLab-2 system will provide sample preparation and qRT-PCR analysis on-board the ISS, a capability to enable using the ISS as a real laboratory. The system will be validated on SpX-7, and is planned for its first PI use on SpX-9.

  10. Influence of the different oxidation treatment on the performance of multi-walled carbon nanotubes in the catalytic wet air oxidation of phenol.

    PubMed

    Yang, Shaoxia; Wang, Xingang; Yang, Hongwei; Sun, Yu; Liu, Yunxia

    2012-09-30

    Multi-walled carbon nanotubes (MWCNTs) functionalized by different oxidants (HNO(3)/H(2)SO(4), H(2)O(2), O(3) and air) have been used as catalysts for the wet air oxidation of phenol. To investigate the effect of the oxidation conditions on the structure of the functionalized MWCNTs, various characterization techniques, e.g., scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, Fourier-transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) have been used. The MWCNTs treated with O(3) and H(2)O(2) show higher amounts of oxygen-containing functional groups and carboxylic acid groups, and a weaker acidic nature, in comparison with those treated with other oxidizing agents. All the functionalized MWCNTs exhibit good activity in the catalytic wet air oxidation (CWAO) of phenol. However, the MWCNTs treated with O(3) show the highest activity with desirable stability in comparison with other functionalized MWCNTs, indicating that the functionalization of carbon nanotubes with O(3) is a very promising strategy in synthesizing efficient catalysts for CWAO.

  11. Degradation of cationic red GTL by catalytic wet air oxidation over Mo-Zn-Al-O catalyst under room temperature and atmospheric pressure.

    PubMed

    Xu, Yin; Li, Xiaoyi; Cheng, Xiang; Sun, Dezhi; Wang, Xueye

    2012-03-06

    To overcome the drawback of catalytic wet air oxidation (CWAO) with high temperature and high pressure, the catalytic activity of Mo-Zn-Al-O catalyst for degradation of cationic red GTL under room temperature and atmospheric pressure was investigated. Mo-Zn-Al-O catalyst was prepared by coprecipitation and impregnation. XRD, TG-DTG, and XPS were used to characterize the resulting sample. Central composition design using response surface methodology was employed to optimize correlation of factors on the decolorization of cationic red GTL. The results show that the optimal conditions of pH value, initial concentration of dye and catalyst dosage were found to be 4.0, 85 mg/L and 2.72 g/L, respectively, for maximum decolorization of 80.1% and TOC removal of 50.9%. Furthermore, the reaction on the Mo-Zn-Al-O catalyst and degradation mechanism of cationic red GTL was studied by Electron spin resonance (ESR) and GC-MS technique. The possible reaction mechanism was that the Mo-Zn-Al-O catalyst can efficiently react with adsorbed oxygen/H(2)O to produce ·OH and (1)O(2) and finally induce the degradation of cationic red GTL. GC-MS analysis of the degradation products indicates that cationic red GTL was initiated by the cleavage of -N ═ N- and the intermediates were further oxidized by ·OH or (1)O(2).

  12. Sewage-sludge-derived carbonaceous materials for catalytic wet hydrogen peroxide oxidation of m-cresol in batch and continuous reactors.

    PubMed

    Yu, Yang; Wei, Huangzhao; Yu, Li; Wang, Wei; Zhao, Ying; Gu, Bin; Sun, Chenglin

    2016-01-01

    In this study, four sewage-sludge-derived carbonaceous materials (SWs) were evaluated for their catalytic wet hydrogen peroxide oxidation (CWPO) performance of m-cresol in batch reactor and continuous reactor, respectively. The SWs were produced by carbonization (SW); carbonization with the addition of CaO (CaO-SW); HNO3 pretreatment (HNO3-SW) and steam activation (Activated-SW). The properties of SW catalysts were assessed by thermogravimetric analysis, Brunauer-Emmett-Teller, Fourier Transform Infrared Spectroscopy, X-ray Fluorescence, Scanning electron microscopy, energy dispersive X-ray analysis and zeta potential. The results showed that SW treated by HNO3 (HNO3-SW) had a high conversion of m-cresol in batch reactor and continuous reactor, respectively. Under the conditions of batch reaction (Cm-cresol = 100 mg L(-1), CH2O2 = 15.7 mmol L(-1), initial pH=7.0, 0.5 g L(-1) catalyst, 80°C, 180 min adsorption and 210 min oxidation), the conversion of m-cresol reached 100% and total organic carbon removal was 67.1%. It had a high catalytic activity and stability on the treatment of m-cresol in CWPO for more than 1100 h. Furthermore, a possible reaction mechanism for the oxidation of m-cresol to 2-methyl-p-benzoquinone by CWPO was proposed.

  13. Ni/MgAlO regeneration for catalytic wet air oxidation of an azo-dye in trickle-bed reaction.

    PubMed

    Vallet, Ana; Ovejero, Gabriel; Rodríguez, Araceli; Peres, José A; García, Juan

    2013-01-15

    Active nickel catalysts (7 wt%) supported over Mg-Al mixed oxides have been recently developed and it has also been demonstrated that they are also highly selective in Catalytic Wet air Oxidation (CWAO) of dyes. CWAO of Chromotrope 2R (C2R) has been studied using a trickle bed reactor employing temperatures from 100 to 180 °C, liquid flow rates from 0.1 to 0.7 mL min(-1) and initial dye concentration from 10 to 50 ppm. Total pressure and air flow were 25 bar and 300 mL min(-1), respectively. The catalyst showed a very stable activity up to 24 h on stream with an average TOC conversion of 82% at 150 °C and T(r)=0.098 g(Ni) min mL(-1). After the reaction, a 1.1 wt% C of carbonaceous deposit is formed onto the catalyst and a diminution of 30% of the surface area with respect of the fresh catalyst was observed. An increase in the space time gave higher TOC conversions up to T(r)=0.098 g(Ni) min mL(-1), attaining values of 80% at 180 °C. The performance of TOC and dye removal does not decrease after two regeneration cycles. In total, a 57 h effective reaction has been carried out with no loss of catalytic activity. Copyright © 2012 Elsevier B.V. All rights reserved.

  14. Treatment of ammonia by catalytic wet oxidation process over platinum-rhodium bimetallic catalyst in a trickle-bed reactor: effect of pH.

    PubMed

    Hung, Chang-Mao; Lin, Wei-Bang; Ho, Ching-Lin; Shen, Yun-Hwei; Hsia, Shao-Yi

    2010-08-01

    This work adopted aqueous solutions of ammonia for use in catalytic liquid-phase reduction in a trickle-bed reactor with a platinum-rhodium bimetallic catalyst, prepared by the co-precipitation of chloroplatinic acid (H2PtCl6) and rhodium nitrate [Rh(NO3)3]. The experimental results demonstrated that a minimal amount of ammonia was removed from the solution by wet oxidation in the absence of any catalyst, while approximately 97.0% of the ammonia was removed by wet oxidation over the platinum-rhodium bimetallic catalyst at 230 degrees C with an oxygen partial pressure of 2.0 MPa. The oxidation of ammonia has been studied as a function of pH, and the main reaction products were determined. A synergistic effect is manifest in the platinum-rhodium bimetallic structure, in which the material has the greatest capacity to reduce ammonia. The reaction pathway linked the oxidizing ammonia to nitric oxide, nitrogen, and water.

  15. Carbon and nitrogen removal from glucose-glycine melanoidins solution as a model of distillery wastewater by catalytic wet air oxidation.

    PubMed

    Phuong Thu, Le; Michèle, Besson

    2016-06-05

    Sugarcane molasses distillery wastewater contains melanoidins, which are dark brown recalcitrant nitrogenous polymer compounds. Studies were carried out in batch mode to evaluate Pt and Ru supported catalysts in the Catalytic Wet Air Oxidation (CWAO) process of a synthetic melanoidins solution, prepared by stoichiometric reaction of glucose with glycine. The addition of a catalyst slightly improved TOC removal compared with the non-catalytic reaction, and especially promoted the conversion of ammonium produced from organically-bound nitrogen in melanoidins to molecular nitrogen and nitrate. The selectivity to N2 attained 89% in the presence of the Pt catalysts in the reaction conditions used (TOC=2200mgL(-1), TN=280mgL(-1), 0.5g catalyst loaded with 3% metal, 210°C, 70bar total air pressure). To avoid leaching of the active metal by organically-bound nitrogen, the reaction was very efficiently performed in a two-step reaction consisting in WAO to convert nitrogen into ammonium, before the introduction of a catalyst.

  16. Application of sludge-based carbonaceous materials in a hybrid water treatment process based on adsorption and catalytic wet air oxidation.

    PubMed

    Julcour Lebigue, Carine; Andriantsiferana, Caroline; N'Guessan Krou; Ayral, Catherine; Mohamed, Elham; Wilhelm, Anne-Marie; Delmas, Henri; Le Coq, Laurence; Gerente, Claire; Smith, Karl M; Pullket, Suangusa; Fowler, Geoffrey D; Graham, Nigel J D

    2010-12-01

    This paper describes a preliminary evaluation of the performance of carbonaceous materials prepared from sewage sludges (SBCMs) in a hybrid water treatment process based on adsorption and catalytic wet air oxidation; phenol was used as the model pollutant. Three different sewage sludges were treated by either carbonisation or steam activation, and the physico-chemical properties of the resultant carbonaceous materials (e.g. hardness, BET surface area, ash and elemental content, surface chemistry) were evaluated and compared with a commercial reference activated carbon (PICA F22). The adsorption capacity for phenol of the SBCMs was greater than suggested by their BET surface area, but less than F22; a steam activated, dewatered raw sludge (SA_DRAW) had the greatest adsorption capacity of the SBCMs in the investigated range of concentrations (<0.05 mol L(-1)). In batch oxidation tests, the SBCMs demonstrated catalytic behaviour arising from their substrate adsorptivity and metal content. Recycling of SA_DRAW in successive oxidations led to significant structural attrition and a hardened SA_DRAW was evaluated, but found to be unsatisfactory during the oxidation step. In a combined adsorption-oxidation sequence, both the PICA carbon and a selected SBCM showed deterioration in phenol adsorption after oxidative regeneration, but a steady state performance was reached after 2 or 3 cycles.

  17. Catalytic wet peroxide oxidation of azo dye (Direct Blue 15) using solvothermally synthesized copper hydroxide nitrate as catalyst.

    PubMed

    Zhan, Yuzhong; Zhou, Xiang; Fu, Bei; Chen, Yiliang

    2011-03-15

    Copper hydroxide nitrate (Cu(2)(OH)(3)NO(3)) was synthesized solvothermally in anhydrous ethanol and characterized by XRD, FTIR, TG-DTA and SEM. The peroxide degradation of an azo dye (Direct Blue 15) on this material was evaluated by examining catalyst loading, initial pH, hydrogen peroxide dosage, initial dye concentration and temperature. The leaching of Cu from the copper hydroxide nitrate during the reaction was also measured. The copper hydroxide nitrate synthesized solvothermally, which was of a novel spherical morphology with complex secondary structures and contained high-dispersed Cu(2)O impurity, showed good performance for oxidation degradation of the azo dye, especially high catalytic activity, high utilization of hydrogen peroxide and a wide pH range, whereas the copper hydroxide nitrate synthesized by the direct reaction of copper nitrate and sodium hydroxide showed low catalytic activity.

  18. Mineralization of gaseous acetaldehyde by electrochemically generated Co(III) in H2SO4 with wet scrubber combinatorial system.

    PubMed

    Govindan, Muthuraman; Chung, Sang-Joon; Moon, Il-Shik

    2012-06-11

    Electrochemically generated Co(III) mediated catalytic room temperature incineration of acetaldehyde, which is one of volatile organic compounds (VOCs), combined with wet scrubbing system was developed and investigated. Depending on the electrolyte's type, absorption come removal efficiency is varied. In presence of electrogenerated Co(III) in sulfuric acid, acetaldehyde was mineralized to CO2 and not like only absorption in pure sulfuric acid. The Co(III) mediated catalytic incineration led to oxidative absorption and elimination to CO2, which was evidenced with titration, CO2, and cyclic voltammetric analyses. Experimental conditions, such as current density, concentration of mediator, and gas molar flow rate were optimized. By the optimization of the experimental conditions, the complete mineralization of acetaldehyde was realized at a room temperature using electrochemically generated Co(III) with wet scrubber combinatorial system.

  19. Drumhead model of 2D wetting, filling and wedge covariance

    NASA Astrophysics Data System (ADS)

    Abraham, D. B.; Parry, A. O.; Wood, A. J.

    2002-10-01

    Recent work has demonstrated novel fluid interfacial behaviour occurring at filling or wedge-wetting transitions in two- and three-dimensional systems. In particular, in two dimensions (2D) studies of filling in shallow wedges, for both pure and impure systems, reveal simple covariance relations which relate criticality at filling to strong-fluctuation regime wetting and restrict the allowed critical singularities. Here we introduce a drumhead interfacial model of filling in acute wedges which can be adapted to include an orientation-dependent surface tension. We calculate the excess wedge free energy and scaling form of the mid-point height probability distribution function (PDF) and demonstrate that the covariance relations are the same as found in the shallow wedge approximation. Connections with exact Ising model results and a bubble model interpretation of the interfacial height PDF at wetting are made.

  20. [Catalytic wet air oxidation of phenol and aniline over multi-walled carbon nanotubes].

    PubMed

    Li, Xiang; Yang, Shao-xi; Zhu, Wan-peng; Wang, Jian-bing; Wang, Li

    2008-09-01

    Multi-walled carbon nanotubes (MWNTs) without any metal ions were used as the catalyst, and investigated in the CWAO of phenol and aniline in a batch reactor. The structures of the MWNTs were characterized by means of SEM and TEM. It showed that the MWNTs, treated with the mixed acid (HNO3-H2SO4), displayed excellent activity and stability in the CWAO. Under the reaction temperature of 160 degrees C, the total pressure of 2.5 MPa, the initial concentration of 1000 mg/L and loading the catalyst of 1.6 g/L, 100% phenol and 86% COD were removed after 120 min reaction in CWAO of phenol. At the same operating conditions, 83% aniline and 68% COD removals were obtained in the CWAO of aniline solution when the initial concentration of aniline was 2 000 mg/L. The surface functional groups played the important role for the high activity of the MWNTs in CWAO of organic compounds.

  1. [Catalytic stability in wet air oxidation of carboxylic acids over ZnFe0.25Al1.75 O4 catalyst].

    PubMed

    Xu, Ai-hua; Yang, Min; Du, Hong-zhang; Peng, Fu-yong; Sun, Cheng-lin

    2007-07-01

    Oxalic, formic and acetic acid are main intermediate products in catalytic wet air oxidation process (CWAO). The catalytic activity and stability in CWAO of the three short-chain organic acids over ZnFe0.25Al1.75O4 catalyst were studied. Oxalic acid is the only oxidizable intermediate and the largest amount of Fe leaching is 9.5 mg L(-1) at 160 degrees C during CWAO process. Formic and acetic acid have little influence on Fe leaching. Due to the strong reducible ability of oxalic acid, the amount of Fe leaching is larger in nitrogen atmosphere than that in oxygen atmosphere. Salicylic acid can be also degraded by ZnFe0.25Al1.75O4 catalyst with a high catalytic activity and stability.

  2. Fabrication development of Li 2O pebbles by wet process

    NASA Astrophysics Data System (ADS)

    Tsuchiya, Kunihiko; Fuchinoue, Katsuhiro; Saito, Shigeru; Watarumi, Kazutoshi; Furuya, Takemi; Kawamura, Hiroshi

    1998-03-01

    Lithium oxide (Li 2O) is one of the best tritium breeding materials. A small sphere of Li 2O is proposed in some designs of fusion blankets. Recently, reprocessing technology on irradiated ceramic tritium breeders was developed from the viewpoint of effective use of resources and reduction of radioactive wastes. The wet process is advantageous for fabricating small Li 2O pebbles from the reprocessed lithium-bearing solutions. Preliminary fabrication tests of Li 2O pebbles by the wet process were carried out. However, the density of the pebbles obtained was only 55%. Therefore, process improvement tests were performed in order to increase the density of Li 2O pebbles fabricated by this method. The improved process yielded Li 2O pebbles in the target range of 80-85% T.D.

  3. Comparative study of supported CuOx and MnOx catalysts for the catalytic wet air oxidation of β-naphthol

    NASA Astrophysics Data System (ADS)

    Liu, Jie; Yu, Chaoying; Zhao, Peiqing; Chen, Gexin

    2012-09-01

    MnOx/nano-TiO2, MnOx/Al2O3-TiO2 (Al-Ti), CuOx/nano-TiO2 and CuOx/Al-Ti were prepared and their application in catalytic wet air oxidation (CWAO) of β-naphthol were investigated. The catalysts had been characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction (TPR) measurements. Phases of CuO, Cu2O, CuAl2O4, MnO2 and Mn2O3 could be found on the surface of the aforementioned catalysts. Significant differences in activities were observed among the prepared catalysts. Compared to CuOx/nano-TiO2, the combined action of highly dispersed CuO as well as CuAl2O4 of CuOx/Al-Ti helped to achieve higher activity for the CWAO of β-naphthol, while the Cu2O component lead to lower efficiency of CuOx/nano-TiO2. On the surface of MnOx/nano-TiO2, both the larger amount of highly dispersed MnO2 and the stronger electron transfer between MnO2 and Mn2O3 were helpful to promote the activity for the degradation of β-naphthol. However, the higher amount of bulk MnO2 and the weaker electron transfer for MnOx/Al-Ti were unfavorable to increase its efficiency. Among the four catalysts as-prepared, MnOx/nano-TiO2 was identified the highest activity with 93.7% COD removal.

  4. Factors influencing catalytic wet peroxide oxidation of maleic acid in aqueous phase over copper/micelle templated silica-3-aminopropyltrimethoxysilane catalyst.

    PubMed

    Daniel, Lilian; Katima, Jamidu H Y

    2009-01-01

    Catalytic wet peroxide oxidation (CWPO) of initial maleic acid feed concentration (0.005 to 0.03 M) was carried out in a temperature range of 20-50 degrees Celsius, on micelle templated silica-3-aminopropyltrimethoxysilane (MTS-AMP) supported copper catalyst. The influence of various operating parameters such as initial feed concentration of maleic acid, temperature, catalyst loading and the stability of the catalyst were investigated. CWPO reactions were performed in a stirred batch reactor at an atmospheric pressure in the presence of H(2)O(2) as an oxidant. Total conversion of maleic acid into acetic acid was obtained under mild conditions (i.e. atmospheric pressure and 40 degrees Celsius). Blank experiments showed no measurable maleic acid conversion (i.e. only approximately 0.5% conversion of initial maleic acid), indicating that a significant oxidation reaction of maleic acid is enhanced by the presence of a catalyst. Copper on micelle templated silica-3-aminopropyltrimethoxysilane catalyst therefore was found to be suitable for aqueous phase oxidation of maleic acid with 100% of maleic acid conversion.

  5. Investigation of the catalytic wet peroxide oxidation of phenol over different types of Cu/ZSM-5 catalyst.

    PubMed

    Valkaj, K Maduna; Katovic, A; Zrncević, S

    2007-06-18

    In this work oxidation of phenol with hydrogen peroxide on Cu/ZSM-5 catalysts was studied. The catalysts samples were prepared by two different methods: by ionic exchange from the protonic form of commercial ZSM-5 zeolite, and by direct hydrothermal synthesis. Characterization of the catalysts extends to X-ray diffraction (XRD), while the adsorption techniques were used for the measurement of the specific surface area. The catalytic tests were carried out in a stainless steel Parr reactor in batch operation mode at the atmospheric pressure and the temperature range from 50 to 80 degrees C. The mass ratio of the active metal component on the zeolite was in the range of 1.62-3.24 wt.%. for catalyst prepared by direct hydrothermal synthesis and 2.23-3.52 wt.% for catalyst prepared by ion exchange method. The initial concentration of phenol and hydrogen peroxide was 0.01 and 0.1 mol dm(-3), respectively. The influence of different methods of Cu/ZSM-5 preparation on their catalytic performance was monitored in terms of phenol conversion and degree of metal leached into aqueous solution.

  6. Microwave assisted catalytic wet air oxidation of H-acid in aqueous solution under the atmospheric pressure using activated carbon as catalyst.

    PubMed

    Zhang, Yaobin; Quan, Xie; Chen, Shuo; Zhao, Yazhi; Yang, Fenglin

    2006-09-01

    Catalytic wet air oxidation (CWAO) is a promising method for the treatment of heavily contaminated wastewater. However, its application is restricted due to severe operation conditions (high pressure and high temperature). A microwave (MW) assisted oxidation method was investigated aiming to treat heavily contaminated wastewater under milder conditions. H-acid (1-amino-8-naphthol-3, 6-disulfonic acid) was selected as target compound to evaluate the performance of this novel process. The removal of H-acid and TOC (total organic carbon) for H-acid solution of 3000 mg/L reached as high as 92.6% in 20 min and 84.2% in 60 min, respectively under optimal conditions. The existence of activated carbon and oxygen proved to be critical for effective treatment. The activated carbon acted not only as a catalyst for H-acid decomposition, but also as a special material for the absorption of MW energy. Air was supplied to the reactor as an oxygen source at constant flows. The amino group in H-acid was converted ultimately into nitrate, and sulfonic group into sulfate. This observation gave an evidence of H-acid mineralization although other organic intermediates were unable to be determined. The value of BOD(5)/COD (ratio of 5d biochemical oxygen demand to chemical oxygen demand) increased from 0.008 to 0.467 indicating a significant improvement of biodegradability for the solution, which is beneficial for the further biological treatment of the wastewater.

  7. The optimization, kinetics and mechanism of m-cresol degradation via catalytic wet peroxide oxidation with sludge-derived carbon catalyst.

    PubMed

    Wang, Yamin; Wei, Huangzhao; Zhao, Ying; Sun, Wenjing; Sun, Chenglin

    2017-03-15

    The sludge-derived carbon catalyst modified with 0°C HNO3 solution was tested in catalytic wet peroxide oxidation of m-cresol (100mgL(-1)) with systematical mathematical models and theoretical calculation for the first time. The reaction conditions were optimized by response surface methodology (RSM) as T=60°C, initial pH=3.0, C0,H2O2(30%)=1.20gL(-1) (lower than the stoichiometric amount of 1.80gL(-1)) and Ccat=0.80gL(-1), with 96% of m-cresol and 47% of TOC converted after 16min and 120min of reaction, respectively, and ξ (mg TOC/g H2O2 fed)=83.6mg/g. The end time of the first kinetic period in m-cresol model was disclosed to be correlated with the fixed residue m-cresol concentration of about 33%. Furthermore, the kinetic constants in models of TOC and H2O2 exactly provide convincing proof of three-dimensional response surfaces analysis by RSM, which showed the influence of the interaction between organics and H2O2 on effective H2O2 utilization. The reaction intermediates over time were identified by gas chromatography-mass spectrometer based on kinetics analysis. Four degradation pathways for m-cresol were proposed, of which the possibility and feasibility were well proven by frontier molecule orbital theory and atomic charge distribution via density functional theory method.

  8. WO3/CeO2/TiO2 Catalysts for Selective Catalytic Reduction of NO(x) by NH3: Effect of the Synthesis Method.

    PubMed

    Michalow-Mauke, Katarzyna A; Lu, Ye; Ferri, Davide; Graule, Thomas; Kowalski, Kazimierz; Elsener, Martin; Kröcher, Oliver

    2015-01-01

    WO3/CeO2/TiO2, CeO2/TiO2 and WO3/TiO2 catalysts were prepared by wet impregnation. CeO2/TiO2 and WO3/TiO2 showed activity towards the selective catalytic reduction (SCR) of NO(x) by NH3, which was significantly improved by subsequent impregnation of CeO/TiO2 with WO3. Catalytic performance, NH3 oxidation and NH3 temperature programmed desorption of wet-impregnated WO3/CeO2/TiO2 were compared to those of a flame-made counterpart. The flame-made catalyst exhibits a peculiar arrangement of W-Ce-Ti-oxides that makes it very active for NH3-SCR. Catalysts prepared by wet impregnation with the aim to mimic the structure of the flame-made catalyst were not able to fully reproduce its activity. The differences in the catalytic performance between the investigated catalysts were related to their structural properties and the different interaction of the catalyst components.

  9. Catalytic wet air oxidation of bisphenol A solution in a batch-recycle trickle-bed reactor over titanate nanotube-based catalysts.

    PubMed

    Kaplan, Renata; Erjavec, Boštjan; Senila, Marin; Pintar, Albin

    2014-10-01

    Catalytic wet air oxidation (CWAO) is classified as an advanced oxidation process, which proved to be highly efficient for the removal of emerging organic pollutant bisphenol A (BPA) from water. In this study, BPA was successfully removed in a batch-recycle trickle-bed reactor over bare titanate nanotube-based catalysts at very short space time of 0.6 min gCAT g(-1). The as-prepared titanate nanotubes, which underwent heat treatment at 600 °C, showed high activity for the removal of aqueous BPA. Liquid-phase recycling (5- or 10-fold recycle) enabled complete BPA conversion already at 200 °C, together with high conversion of total organic carbon (TOC), i.e., 73 and 98 %, respectively. The catalyst was chemically stable in the given range of operating conditions for 189 h on stream.

  10. Electrochemical, H2O2-Boosted Catalytic Oxidation System

    NASA Technical Reports Server (NTRS)

    Akse, James R.; Thompson, John O.; Schussel, Leonard J.

    2004-01-01

    An improved water-sterilizing aqueous-phase catalytic oxidation system (APCOS) is based partly on the electrochemical generation of hydrogen peroxide (H2O2). This H2O2-boosted system offers significant improvements over prior dissolved-oxygen water-sterilizing systems in the way in which it increases oxidation capabilities, supplies H2O2 when needed, reduces the total organic carbon (TOC) content of treated water to a low level, consumes less energy than prior systems do, reduces the risk of contamination, and costs less to operate. This system was developed as a variant of part of an improved waste-management subsystem of the life-support system of a spacecraft. Going beyond its original intended purpose, it offers the advantage of being able to produce H2O2 on demand for surface sterilization and/or decontamination: this is a major advantage inasmuch as the benign byproducts of this H2O2 system, unlike those of systems that utilize other chemical sterilants, place no additional burden of containment control on other spacecraft air- or water-reclamation systems.

  11. Degradation of remazol golden yellow dye wastewater in microwave enhanced ClO2 catalytic oxidation process.

    PubMed

    Bi, Xiaoyi; Wang, Peng; Jiao, Chunyan; Cao, Hailei

    2009-09-15

    Experiments were conducted to investigate the removal of remazol golden yellow dye in order to assess the effectiveness and feasibility of microwave enhanced chlorine dioxide (ClO(2)) catalytic oxidation process. The catalyst used in this process was CuO(n)-La(2)O(3)/gamma-Al(2)O(3). The operating parameters such as the ClO(2) dosage, catalyst dosage, and pH were evaluated. The results showed that microwave enhanced catalytic oxidation process could effectively degrade remazol golden yellow dye with low oxidant dosage in a short reaction time and extensive pH range compared to the conventional wet catalytic oxidation. Under the optimal condition (ClO(2) concentration 80 mg/L, microwave power 400 W, contacting time 1.5 min, catalyst dosage 70 g/L, and pH 7), color removal efficiency approached 94.03%, corresponding to 67.92% of total organic carbon removal efficiency. It was found that the fluorescence intensity in microwave enhanced ClO(2) catalytic oxidation system was about 500a.u. which was verified that there was much hydroxyl radical produced. Compared with different processes, microwave enhanced ClO(2) catalytic oxidation system could significantly enhance the degradation efficiency. It provides an effective technology for dye wastewater treatment.

  12. Catalytic behaviour and copper leaching of Cu0.10Zn0.90Al1.90Fe0.10O4 spinel for catalytic wet air oxidation of phenol.

    PubMed

    Xu, Aihua; Sun, Chenglin

    2012-06-01

    A Cu0.10Zn0.90Al1.90Fe0.10O4 spinel catalyst prepared by the sol-gel method was tested for catalytic wet air oxidation (CWAO) of phenol. The catalyst showed high activity for phenol degradation. During successive test at 170 degrees C, 100% phenol conversion and 95% chemical oxygen demand (COD) removal were observed. Results from scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) indicated that the catalyst structure remained unchanged during reaction. From the analysis of temperature programmed reduction (TPR), diffuse reflectance UV-Vis spectra (DR UV-Vis) and activity assay at basic solution pH, it can be suggested that the highly dispersed copper ions on the catalyst surface were almost completely dissolved into the reaction solution, whereas the tetra-coordinated copper ions were not only stable against leaching but also active towards phenol degradation.

  13. Forsterite Carbonation in Wet Supercritical CO2 and Sodium Citrate

    NASA Astrophysics Data System (ADS)

    Qiu, L.; Schaef, T.; Wang, Z.; Miller, Q.; McGrail, P.

    2013-12-01

    Lin Qiu1*, Herbert T. Schaef2, Zhengrong Wang1, Quin R.S. Miller3, BP McGrail2 1. Yale University, New Haven, CT, USA 2. Pacific Northwest National Laboratory, Richland, WA, USA 3. University of Wyoming, Laramie, WY, USA Geologic reservoirs for managing carbon emissions (mostly CO2) have expanded over the last 5 years to include unconventional formations including basalts and fractured shales. Recently, ~1000 metric tons of CO2 was injected into the Columbia River Basalt (CRB) in Eastern Washington as part of the Wallula Pilot Project, Big Sky Regional Carbon Partnership. Based on reservoir conditions, the injected CO2 is present as a supercritical fluid that dissolves into the formation water over time, and reacts with basalt components to form carbonate minerals. In this paper, we discuss mineral transformation reactions occurring when the forsterite (Mg2SiO4) is exposed to wet scCO2 in equilibrium with pure water and sodium citrate solutions. Forsterite was selected as it is an important olivine group mineral present in igneous and mafic rocks. Citrate was selected as it has been shown to enhance mineral dissolution and organic ligands are possible degradation products of the microbial communities present in the formational waters of the CRB. For the supercritical phase, transformation reactions were examined by in situ high pressure x-ray diffraction (HXRD) in the presence of supercritical carbon dioxide (scCO2) in contact with water and sodium citrate solutions at conditions relevant to carbon sequestration. Experimental results show close-to-complete dissolution of forsterite in contact with scCO2 equilibrated with pure water for 90 hours (90 bar and 50°C). Under these conditions, thin films of water coated the mineral surface, providing a mechanism for silicate dissolution and transport of cations necessary for carbonate formation. The primary crystalline component initially detected with in situ HXRD was the hydrated magnesium carbonate, nesquehonite [Mg

  14. Contribution of the Global Soil Wetness Project 2 for PUB

    NASA Astrophysics Data System (ADS)

    Oki, T.; Dirmeyer, P. A.

    2003-04-01

    The Second Global Soil Wetness Project (GSWP-2) is the principal element of the large-scale uncoupled land surface modeling action in the Global Land-Atmosphere System Study (GLASS; Polcher et al. 2000) and a major element of the International Satellite Land-Surface Climatology Project (ISLSCP), both contributing projects of GEWEX. The overarching goal of GSWP is to produce as a community effort the best model estimates of the global land-surface water and energy cycles. This will entail an evaluation of the uncertainties linked to the land surface schemes (LSSs), their parameters, the forcing variables which drive them, and the spatial and temporal scales to run the numerical simulations. The original pilot phase of GSWP covered the two-year period of the ISLSCP initiative I data set (1987-1988), and proved the utility of model comparison and sensitivity studies of the land surface at the global scale (Dirmeyer et al. 1999). GSWP-2 will take advantage of the 10-year (1986-1995) ISLSCP Initiative II data set (http://islscp2.sesda.com/) and LSS simulations will be conducted at a spatial resolution of 1o, sans Antarctica. LSSs calculate runoff and it can be compared with river discharge with applying runoff routing models. Therefore GSWP can be considered as PUB on global scales. Regional scales should be more focused in PUB as hydrological science, nevertheless studies on global scale is also relevant since there are many places in the world where global datasets of precipitation, landuse, soil types, etc., are the only sources available for simulation and prediction of river runoff. Numerical experiments under GSWP2 is well designed to examine the uncertainties associated with the global offline simulations, and the outcomes should contribute for PUB studies very much. GSWP2 in PUB is also expected to identify to what extent of temporal and spatial resolution predicting river runoff can be estimated from global approach.

  15. Development studies for a novel wet oxidation process. Phase 2

    SciTech Connect

    1994-07-01

    DETOX{sup SM} is a catalyzed wet oxidation process which destroys organic materials in an acidic water solution of iron at 373 to 473 K. The solution can be used repeatedly to destroy great amounts of organic materials. Since the process is conducted in a contained vessel, air emissions from the process can be well controlled. The solution is also capable of dissolving and concentrating many heavy and radioactive metals for eventual stabilization and disposal. The Phase 2 effort for this project is site selection and engineering design for a DETOX demonstration unit. Site selection was made using a set of site selection criteria and evaluation factors. A survey of mixed wastes at DOE sites was conducted using the Interim Mixed Waste Inventory Report. Sites with likely suitable waste types were identified. Potential demonstration sites were ranked based on waste types, interest, regulatory needs, scheduling, ability to provide support, and available facilities. Engineering design for the demonstration unit is in progress and is being performed by Jacobs Applied Technology. The engineering design proceeded through preliminary process flow diagrams (PFDs), calculation of mass and energy balances for representative waste types, process and instrumentation diagrams (P and IDs), preparation of component specifications, and a firm cost estimate for fabrication of the demonstration unit.

  16. [Fe-ZSM-5 catalysts with different silica-alumina ratios for N2O, catalytic decomposition].

    PubMed

    Lu, Ren-Jie; Zhang, Xin-Yan; Hao, Zheng-Ping

    2014-01-01

    The Fe-ZSM-5 catalysts were prepared with H-ZSM-5 of different Si/Al ratios by wet ion exchange and chemical vapor deposition. Then the catalysts were investigated by XRD, BET, TEM, UV-vis and NH3-TPD technologies to analyze the iron states in Fe-ZSM-5 zeolites. The results showed that after H-ZSM-5 zeolites were prepared by chemical vapor deposition and heating wet ion exchange, the nano Fe2 O3 particles were uniformly dispersed with the sizes of 8 nm in the Fe-ZSM-5-25 (Si/A1-25). Moreover, there were more oligonuclear Fe3+ Oy clusters in the Fe-ZSM-5-25 catalysts than in Fe-ZSM-5-300 (Si/Al-300). The results of catalytic performance on N2O decomposition showed that Fe-ZSM-5-25 catalysts had higher catalytic activities than Fe-ZSM-5-300 catalysts. The Fe-ZSM-5 catalysts prepared by chemical vapor deposition achieved the best catalytic activity in N2O decomposition among the catalysts prepared by the three methods. Moreover, the presence of O2 only slightly reduced N2O conversion, while NO promoted the N2O decomposition. Finally, after reaction for more than 100 h, Fe-ZSM-5 catalyst showed no obvious deactivation under simulated emission conditions.

  17. Evaporation-coupled wetting of ZrO2 by molten Mg in Ar atmosphere

    NASA Astrophysics Data System (ADS)

    Zhang, Dan; Shi, Laixin; Shen, Ping; Lin, Qiaoli; Jiang, Qichuan

    2010-03-01

    The wetting behaviors of molten Mg drops on polycrystalline ZrO2 substrate surfaces were studied in a controlled Ar atmosphere at 948-1173 K using an improved sessile drop method. The ZrO2 substrate is virtually not wetted by molten Mg at temperatures below 1173 K. The wetting and evaporation stages according to different variation behaviors of contact angle, contact diameter and drop height were identified. Six representative modes were proposed to describe the evaporation-coupled wetting behaviors during different stages. The competitions between surface oxidation, chemical reaction and drop evaporation were discussed to account for the mechanisms for various wetting behaviors at different temperatures. The chemical reaction leads to the formation of more wettable MgO phase at the interface; however, it yields only an inconspicuous improvement in the wetting due to enhanced Mg evaporation.

  18. Synthesis, characterization, and catalytic activity of type 2 crystalline titanates prepared with supercritical drying

    NASA Astrophysics Data System (ADS)

    Al-Adwani, Hamad A. H.

    Supercritically dried silico-alumino-titanate (Si-Al-Ti) mixed oxides (T2CT) were successfully synthesized by a sol-gel method with hydrothermal synthesis temperatures less than 200°C and autogenic pressure. High-surface-area T2CT aerogels with meso- to macroporosity were obtained. All solid products, after calcination at 450°C, are semicrystalline. In addition, successful scale-up of T2CT synthesis in a one-gallon reactor yielding 500 g was achieved. Surface areas, pore volumes, and average pore diameters are greatly influenced by the drying method. Supercritical drying had no effect on the crystalline or molecular structure of the materials. The synthesized materials were characterized by means of nitrogen physisorption, X-ray diffraction (XRD), thermal analysis, and diffuse reflectance FTIR spectroscopy. The addition of different amounts of phosphorous and antimony affected neither the textural nor the structural aspects of T2CT. However, a decrease in surface area occurred. The catalytic activity of these materials was evaluated after being loaded with nickel and molybdenum by the incipient wetness method. Cyclohexene hydrogenation and thiophene hydrodesulfurization reactions are used in the catalytic activity study. The activities of some of the catalyst prepared in this study are in the same range as the commercial catalyst, Shell 324, but with lower metal loadings than the commercial catalysts. Thus, more efficient use of Mo and Ni was observed.

  19. ENHANCED CONTROL OF MERCURY BY WET FLUE GAS DESULFURIZATION SYSTEMS--SITE 2 RESULTS

    SciTech Connect

    G. Blythe; S. Miller; C. Richardson; K. Searcy

    2000-02-01

    The U.S. Department of Energy and EPRI are co-funding this project to improve the control of mercury emissions from coal-fired power plants equipped with wet flue gas desulfurization (FGD) systems. The project is investigating catalytic oxidation of vapor-phase elemental mercury to a form that is more effectively captured in wet FGD systems. If successfully developed, the process could be applicable to over 90,000 MW of utility generating capacity with existing FGD systems, and to future FGD installations. Field tests are being conducted to determine whether candidate catalyst materials remain active towards mercury oxidation after extended flue gas exposure. Catalyst life will have a large impact on the cost effectiveness of this potential process. A mobile catalyst test unit is being used to test the activity of four different catalysts for a period of up to six months at each of three utility sites. Catalyst testing at the first site, which fires Texas lignite, was completed in December 1998. Testing at the second test site, which fires a Powder River Basin subbituminous coal, was completed in the fall of 1999, and testing at the third site, which fires a high-sulfur bituminous coal, will begin in early 2000. This technical note reports results from Site 2; results from Site 1 were reported in a previous technical note. At Site 2, catalysts were tested in several forms, including powders dispersed in sand bed reactors and in more commercially viable forms such as extruded beads and coated honeycomb structures. This technical note presents results from Site 2 for both the sand bed reactors and commercial catalyst forms. Site 3 results are not yet available, but should be available late in the year 2000. Field testing is being supported by laboratory tests to screen catalysts for activity at specific flue gas compositions, to investigate catalyst deactivation mechanisms and to investigate methods for regenerating spent catalysts. Laboratory results related to the

  20. ENHANCED CONTROL OF MERCURY BY WET FLUE GAS DESULFURIZATION SYSTEMS--SITE 2 RESULTS

    SciTech Connect

    G. Blythe; S. Miller; C. Richardson; K. Searcy

    2000-06-01

    The U.S. Department of Energy and EPRI are co-funding this project to improve the control of mercury emissions from coal-fired power plants equipped with wet flue gas desulfurization (FGD) systems. The project is investigating catalytic oxidation of vapor-phase elemental mercury to a form that is more effectively captured in wet FGD systems. If successfully developed, the process could be applicable to over 90,000 MW of utility generating capacity with existing FGD systems, and to future FGD installations. Field tests are being conducted to determine whether candidate catalyst materials remain active towards mercury oxidation after extended flue gas exposure. Catalyst life will have a large impact on the cost effectiveness of this potential process. A mobile catalyst test unit is being used to test the activity of four different catalysts for a period of up to six months at each of three utility sites. Catalyst testing at the first site, which fires Texas lignite, was completed in December 1998. Testing at the second test site, which fires a Powder River Basin subbituminous coal, was completed in the fall of 1999, and testing at the third site, which fires a high-sulfur bituminous coal, will begin in 2000. This technical note reports results from Site 2; results from Site 1 were reported in a previous technical note. At Site 2, catalysts were tested in several forms, including powders dispersed in sand bed reactors and in commercial forms such as extruded beads and coated honeycomb structures. This technical note presents results from Site 2 for both the sand bed reactors and commercial catalyst forms. Field testing is being supported by laboratory tests to screen catalysts for activity at specific flue gas compositions, to investigate catalyst deactivation mechanisms and to investigate methods for regenerating spent catalysts. Laboratory results related to the Site 2 field effort are also included and discussed in this technical note. Preliminary economics, based

  1. Characterization and monitoring of cracking of steel equipment in wet H{sub 2}S service

    SciTech Connect

    Cayard, M.S.; Kane, R.D.

    1995-11-01

    The results of large-scale wet H{sub 2}S exposure tests which utilized a steel pressure vessel containing various welded test plates are presented. Effect of variables including steel base plate composition, metallurgical processing, welding, applied stress and orientation were examined. Particular attention was given to (1) large-scale behavior versus that determined for small-scale laboratory test specimens under an applied tensile stress, (2) performance of conventional carbon steels versus advanced carbon steels designed for enhanced resistance to hydrogen-induced cracking (MC), and (3) the interrelationship of stress, welding and plate orientation on the susceptibility to wet H{sub 2}S cracking. Several non-destructive evaluation (NDE) techniques were also evaluated for their ability to detect and monitor wet H{sub 2}S cracking. NDE techniques evaluated included wet fluorescent magnetic particle testing (WFMPT), manual ultrasonic testing (MUT), automated ultrasonic testing (AUT) and on-line acoustic emission testing (AET). The results of this program have (1) provided valuable insight on the role of steel quality and microstructure on the susceptibility to wet H{sub 2}S cracking, (2) demonstrated the effectiveness of various NDE techniques in detecting and monitoring cracking of carbon steel equipment exposed to wet H{sub 2}S environments and (3) provided valuable data on the residual strengths and toughnesses of steels containing extensive wet H{sub 2}S damage.

  2. Removal of salicylic acid on perovskite-type oxide LaFeO3 catalyst in catalytic wet air oxidation process.

    PubMed

    Yang, Min; Xu, Aihua; Du, Hongzhang; Sun, Chenglin; Li, Can

    2007-01-02

    It has been found that salicylic acid can be removal effectively at the lower temperature of 140 degrees C on perovskite-type oxide LaFeO3 catalyst in the catalytic wet air oxidation (CWAO) process. Under the same condition, the activities for the CWAO of phenol, benzoic acid and sulfonic salicylic acid have been also investigated. The results indicated that, with compared to the very poor activities for phenol and benzoic acid, the activities for salicylic acid and sulfonic salicylic acid were very high, which are attributed to their same intramolecular H-bonding structures. With the role of hard acidity of intramolecular H-bonding, salicylic acid and sulfonic salicylic acid can be adsorbed effectively on the basic center of LaFeO3 catalyst and are easy to take place the total oxidation reaction. However, at temperatures higher than 140 degrees C, the intramolecular H-bonding structure of salicylic acid was destroyed and the activities at 160 and 180 degrees C decreased greatly, which confirms further the key role of intramolecular H-bonding in the CWAO. Moreover, the LaFeO3 catalyst also indicated a superior stability of activity and structure in CWAO of salicylic acid.

  3. Catalytic Reduction of CO2 by Renewable Organohydrides.

    PubMed

    Lim, Chern-Hooi; Holder, Aaron M; Hynes, James T; Musgrave, Charles B

    2015-12-17

    Dihydropyridines are renewable organohydride reducing agents for the catalytic reduction of CO2 to MeOH. Here we discuss various aspects of this important reduction. A centerpiece, which illustrates various general principles, is our theoretical catalytic mechanism for CO2 reduction by successive hydride transfers (HTs) and proton transfers (PTs) from the dihydropyridine PyH2 obtained by 1H(+)/1e(-)/1H(+)/1e(-) reductions of pyridine. The Py/PyH2 redox couple is analogous to NADP(+)/NADPH in that both are driven to effect HTs by rearomatization. High-energy radical intermediates and their associated high barriers/overpotentials are avoided because HT involves a 2e(-) reduction. A HT-PT sequence dictates that the reduced intermediates be protonated prior to further reduction for ultimate MeOH formation; these protonations are aided by biased cathodes that significantly lower the local pH. In contrast, cathodes that efficiently reduce H(+) such as Pt and Pd produce H2 and create a high interfacial pH, both obstructing dihydropyridine production and formate protonation and thus ultimately CO2 reduction by HTPTs. The role of water molecule proton relays is discussed. Finally, we suggest future CO2 reduction strategies by organic (photo)catalysts.

  4. Selectivity of hydrogen peroxide decomposition towards hydroxyl radicals in catalytic wet peroxide oxidation (CWPO) over Fe/AC catalysts.

    PubMed

    Rey, A; Bahamonde, A; Casas, J A; Rodríguez, J J

    2010-01-01

    Two Fe/AC catalysts prepared with different iron precursors (iron nitrate and iron pentacarbonyl) and the same AC support have been tested in H(2)O(2) decomposition in presence and absence of methanol, a known strong scavenger of hydroxyl radicals, to investigate the selectivity towards .OH formation in this reaction and their behavior in the CWPO of phenol. The catalyst prepared with iron nitrate, with the most oxidized surface and the highest Fe surface content, seems to favor a higher selectivity towards .OH formation in CWPO allowing for complete phenol conversion and a significant TOC removal, with the highest mineralization degree at 50 degrees C and atmospheric pressure. Fe/AC catalysts were more efficient in the CWPO of phenol than in methanol presence due to a better use of the oxidant since adsorbed phenol on catalyst surface minimizes inefficient H(2)O(2) decomposition to H(2)O and O(2)(g). The influence of the initial H(2)O(2) concentration on phenol oxidation with this catalyst was also studied. A theoretical stoichiometric amount of H(2)O(2) for complete oxidation of phenol was chosen as the best starting concentration since auto-scavenging reactions can be minimized and it is sufficient for oxidizing phenol and the aromatic intermediates.

  5. Soil CO2 Fluxes Following Wetting Events: Field Observations and Modeling

    NASA Astrophysics Data System (ADS)

    O'Donnell, F. C.; Caylor, K. K.

    2009-12-01

    Carbon exchange data from eddy flux towers in drylands suggest that the Birch Effect, a pulse of soil CO2 efflux triggered by the first rain following a dry period, may contribute significantly to the annual carbon budget of these ecosystems. Laboratory experiments on dryland soils have shown that microbes adapted to live in arid ecosystems may be able to remain dormant in dry soil for much longer than expected and an osmotic shock response to sudden increases in soil water potential may play a role in the Birch Effect. However, little has been done to understand how a dry soil profile responds to a rainfall event. We measured soil CO2 production during experimental wetting events in treatment plots at a site on the Botswana portion of the Kalahari Transect (KT). We buried small, solid-state sensors that continuously measure CO2 concentration in the soil air space at four depths and the soil surface and applied wetting treatments intended to simulate typical rainfall for the region to the plots, including single 10 mm wettings (the mean storm depth for the KT), single 20 mm wettings, and repeated 10 mm wettings. We solved a finite difference approximation of the governing equation for CO2 in the soil airspace to determine the source rate of CO2 during and after the wetting treatments, using Richard’s equation to approximate the change in air-filled porosity due to infiltrating water. The wetting treatments induced a rapid spike in the source rate of CO2 in the soil, the timing and magnitude of which were consistent with laboratory experiments that observed a microbial osmotic shock response. The source rate averaged over the first three hours after wetting showed that a 20 mm wetting produced a larger response than the 10 mm wettings. It also showed that a second wetting event produced a smaller response than the first and though it was not significant, an upward trend in response was apparent through the two month period. These results suggest that there may be

  6. Effect of chromium oxide as active site over TiO2-PILC for selective catalytic oxidation of NO.

    PubMed

    Zhang, Jingxin; Zhang, Shule; Cai, Wei; Zhong, Qin

    2013-12-01

    This study introduced TiO2-pillared clays (TiO2-PILC) as a support for the catalytic oxidation of NO and analyzed the performance of chromium oxides as the active site of the oxidation process. Cr-based catalysts were prepared by a wet impregnation method. It was found that the 10 wt.% chromium doping on the support achieved the best catalytic activity. At 350 degrees C, the NO conversion was 61% under conditions of GHSV = 23600 hr(-1). The BET data showed that the support particles had a mesoporous structure. H2-TPR showed that Cr(10)TiP (10 wt.% Cr doping on TiO2-PILC) clearly exhibited a smooth single peak. EPR and XPS were used to elucidate the oxidation process. During the NO + O2 adsorption, the intensity of evolution of superoxide ions (O2(-)) increased. The content of Cr3+ on the surface of the used catalyst was 40.37%, but when the used catalyst continued adsorbing NO, the Cr3+ increased to 50.28%. Additionally, O(alpha)/O(beta) increased markedly through the oxidation process. The NO conversion decreased when SO2 was added into the system, but when the SO2 was removed, the catalytic activity recovered almost up to the initial level. FT-IR spectra did not show a distinct characteristic peak of SO4(2-).

  7. Integrated catalytic wet air oxidation and aerobic biological treatment in a municipal WWTP of a high-strength o-cresol wastewater.

    PubMed

    Suarez-Ojeda, María Eugenia; Guisasola, Albert; Baeza, Juan A; Fabregat, Azael; Stüber, Frank; Fortuny, Agustí; Font, Josep; Carrera, Julián

    2007-02-01

    This study examines the feasibility of coupling a Catalytic Wet Air Oxidation (CWAO), with activated carbon (AC) as catalyst, and an aerobic biological treatment to treat a high-strength o-cresol wastewater. Two goals are pursued: (a) To determine the effect of the main AC/CWAO intermediates on the activated sludge of a municipal WasteWater Treatment Plant (WWTP) and (b) To demonstrate the feasibility of coupling the AC/CWAO effluent as a part of the influent of a municipal WWTP. In a previous study, a high-strength o-cresol wastewater was treated by AC/CWAO aiming to establish the distribution of intermediates and the biodegradability enhancement. In this work, the biodegradability, toxicity and inhibition of the most relevant intermediates detected in the AC/CWAO effluent were determined by respirometry. Also, the results of a pilot scale municipal WWTP study for an integrated AC/CWAO-aerobic biological treatment of this effluent are presented. The biodegradation parameters (i.e. maximum oxygen uptake rate and oxygen consumption) of main AC/CWAO intermediates allowed the classification of the intermediates into readily biodegradable, inert or toxic/inhibitory compounds. This detailed study, allowed to understand the biodegradability enhancement exhibited by an AC/CWAO effluent and to achieve a successful strategy for coupling the AC/CWAO step with an aerobic biological treatment for a high-strength o-cresol wastewater. Using 30%, as COD, of AC/CWAO effluent in the inlet to the pilot scale WWTP, the integrated AC/CWAO-biological treatment achieved a 98% of total COD removal and, particularly, a 91% of AC/CWAO effluent COD removal without any undesirable effect on the biomass.

  8. Tunable Wetting Property in Growth Mode-Controlled WS2 Thin Films

    NASA Astrophysics Data System (ADS)

    Choi, Byoung Ki; Lee, In Hak; Kim, Jiho; Chang, Young Jun

    2017-04-01

    We report on a thickness-dependent wetting property of WS2/Al2O3 and WS2/SiO2/Si structures. We prepared WS2 films with gradient thickness by annealing thickness-controlled WO3 films at 800 °C in sulfur atmosphere. Raman spectroscopy measurements showed step-like variation in the thickness of WS2 over substrates several centimeters in dimension. On fresh surfaces, we observed a significant change in the water contact angle depending on film thickness and substrate. Transmission electron microscopy analysis showed that differences in the surface roughness of WS2 films can account for the contrasting wetting properties between WS2/Al2O3 and WS2/SiO2/Si. The thickness dependence of water contact angle persisted for longer than 2 weeks, which demonstrates the stability of these wetting properties when exposed to air contamination.

  9. Tunable Wetting Property in Growth Mode-Controlled WS2 Thin Films.

    PubMed

    Choi, Byoung Ki; Lee, In Hak; Kim, Jiho; Chang, Young Jun

    2017-12-01

    We report on a thickness-dependent wetting property of WS2/Al2O3 and WS2/SiO2/Si structures. We prepared WS2 films with gradient thickness by annealing thickness-controlled WO3 films at 800 °C in sulfur atmosphere. Raman spectroscopy measurements showed step-like variation in the thickness of WS2 over substrates several centimeters in dimension. On fresh surfaces, we observed a significant change in the water contact angle depending on film thickness and substrate. Transmission electron microscopy analysis showed that differences in the surface roughness of WS2 films can account for the contrasting wetting properties between WS2/Al2O3 and WS2/SiO2/Si. The thickness dependence of water contact angle persisted for longer than 2 weeks, which demonstrates the stability of these wetting properties when exposed to air contamination.

  10. Argonaute2 is the catalytic engine of mammalian RNAi.

    PubMed

    Liu, Jidong; Carmell, Michelle A; Rivas, Fabiola V; Marsden, Carolyn G; Thomson, J Michael; Song, Ji-Joon; Hammond, Scott M; Joshua-Tor, Leemor; Hannon, Gregory J

    2004-09-03

    Gene silencing through RNA interference (RNAi) is carried out by RISC, the RNA-induced silencing complex. RISC contains two signature components, small interfering RNAs (siRNAs) and Argonaute family proteins. Here, we show that the multiple Argonaute proteins present in mammals are both biologically and biochemically distinct, with a single mammalian family member, Argonaute2, being responsible for messenger RNA cleavage activity. This protein is essential for mouse development, and cells lacking Argonaute2 are unable to mount an experimental response to siRNAs. Mutations within a cryptic ribonuclease H domain within Argonaute2, as identified by comparison with the structure of an archeal Argonaute protein, inactivate RISC. Thus, our evidence supports a model in which Argonaute contributes "Slicer" activity to RISC, providing the catalytic engine for RNAi.

  11. The physical origins of rapid soil CO2 release following wetting

    NASA Astrophysics Data System (ADS)

    Schymanski, Stanislaus; Grahm, Lina; Or, Dani

    2017-04-01

    A rainfall event after an extended dry period is known to produce large spikes in CO2 release from soil, a phenomenon referred to as the "Birch effect". The Birch effect is commonly attributed to biological factors, such as the rapid activation of dormant microbial populations and stimulation of soil organic carbon turnover. Evidence suggests that CO2 emissions set in at time scales too short for microbial activation and growth (seconds to minutes after onset of wetting). We conducted controlled wetting experiments on sterilized soil in the lab showing CO2 efflux dynamics that are consistent in magnitude with those reported in field studies (up to 4 mmol m-2 s-1 per mm of precipitation). The explanation proposed is purely physical, involving desorption of CO2 from soil surfaces as it is replaced by the more polar water during wetting. We present experimental results and a CO2 adsorption and desorption model that lend credence to the notion that a large fraction of the early soil CO2 emission during wetting (minutes to an hour) is associated with physical processes independent of microbial activity. This suggests that a significant amount of atmospheric CO2 becomes bound to soil surfaces during dry seasons and is rapidly released at the onset of wet seasons world-wide, irrespective of the soil organic carbon cycle.

  12. Wetting properties of phospholipid dispersion on tunable hydrophobic SiO2-glass plates.

    PubMed

    Alexandrova, Lidia; Karakashev, Stoyan I; Grigorov, L; Phan, Chi M; Smoukov, Stoyan K

    2015-06-01

    We study the wetting properties of very small droplets of salty aqueous suspensions of unilamellar liposomes of DMPC (dimyristoylphosphatidylcholine), situated on SiO2-glass surfaces with different levels of hydrophobicity. We evaluated two different measures of hydrophobicity of solid surfaces - receding contact angles and the thickness of wetting films trapped between an air bubble and the solid surface at different levels of hydrophobicity. We established a good correlation between methods which differ significantly in measurement difficulty and experimental setup. We also reveal details of the mechanism of wetting of different surfaces by the DMPC liposome suspension. Hydrophilic surfaces with water contact angles in the range of 0° to 35° are readily hydrophobized by the liposomes and only showed corresponding contact angles in the range 27°-43°. For same range of surface hydrophobicities, there was a clear reduction of the thickness of the wetting films between the surface and a bubble, reaching a minimum in the 35°-40° range. At higher levels of hydrophobicity both pure water and the liposome suspension show similar contact angles, and the thickness of wetting films between a bubble and those surfaces increases in parallel. Our analysis showed that the only force able to stabilize the film under these experimental conditions is steric repulsion. The latter suggests that nanobubbles adsorbed on hydrophobic parts of the surface, and coated with a DMPC layer, may be the cause of the 40-70 nm thickness of wetting films we observe.

  13. 40 CFR Table 2 to Subpart Uuu of... - Operating Limits for Metal HAP Emissions From Catalytic Cracking Units

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Emissions From Catalytic Cracking Units 2 Table 2 to Subpart UUU of Part 63 Protection of Environment... Petroleum Refineries: Catalytic Cracking Units, Catalytic Reforming Units, and Sulfur Recovery Units Pt. 63... Catalytic Cracking Units As stated in § 63.1564(a)(2), you shall meet each operating limit in the...

  14. Residual trapping of supercritical CO2 in oil-wet sandstone.

    PubMed

    Rahman, Taufiq; Lebedev, Maxim; Barifcani, Ahmed; Iglauer, Stefan

    2016-05-01

    Residual trapping, a key CO2 geo-storage mechanism during the first decades of a sequestration project, immobilizes micrometre sized CO2 bubbles in the pore network of the rock. This mechanism has been proven to work in clean sandstones and carbonates; however, this mechanism has not been proven for the economically most important storage sites into which CO2 will be initially injected at industrial scale, namely oil reservoirs. The key difference is that oil reservoirs are typically oil-wet or intermediate-wet, and it is clear that associated pore-scale capillary forces are different. And this difference in capillary forces clearly reduces the capillary trapping capacity (residual trapping) as we demonstrate here. For an oil-wet rock (water contact angle θ=130°) residual CO2 saturation SCO2,r (≈8%) was approximately halved when compared to a strongly water-wet rock (θ=0°; SCO2,r≈15%). Consequently, residual trapping is less efficient in oil-wet reservoirs. Copyright © 2016 Elsevier Inc. All rights reserved.

  15. 40 CFR Table 2 to Subpart Eeee of... - Operating Limits for Incinerators and Wet Scrubbers

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 6 2010-07-01 2010-07-01 false Operating Limits for Incinerators and Wet Scrubbers 2 Table 2 to Subpart EEEE of Part 60 Protection of Environment ENVIRONMENTAL PROTECTION..., Subpt. EEEE, Table 2 Table 2 to Subpart EEEE of Part 60—Operating Limits for Incinerators and...

  16. 40 CFR Table 2 to Subpart Eeee of... - Operating Limits for Incinerators and Wet Scrubbers

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 7 2013-07-01 2013-07-01 false Operating Limits for Incinerators and Wet Scrubbers 2 Table 2 to Subpart EEEE of Part 60 Protection of Environment ENVIRONMENTAL PROTECTION..., Subpt. EEEE, Table 2 Table 2 to Subpart EEEE of Part 60—Operating Limits for Incinerators and...

  17. 40 CFR Table 2 to Subpart Eeee of... - Operating Limits for Incinerators and Wet Scrubbers

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 7 2014-07-01 2014-07-01 false Operating Limits for Incinerators and Wet Scrubbers 2 Table 2 to Subpart EEEE of Part 60 Protection of Environment ENVIRONMENTAL PROTECTION..., Subpt. EEEE, Table 2 Table 2 to Subpart EEEE of Part 60—Operating Limits for Incinerators and...

  18. Catalytic activity of CuOn-La2O3/gamma-Al2O3 for microwave assisted ClO2 catalytic oxidation of phenol wastewater.

    PubMed

    Bi, Xiaoyi; Wang, Peng; Jiang, Hong

    2008-06-15

    In order to develop a catalyst with high activity and stability for microwave assisted ClO2 catalytic oxidation, we prepared CuOn-La2O3/gamma-Al2O3 by impregnation-deposition method, and determined its properties using BET, XRF, XPS and chemical analysis techniques. The test results show that, better thermal ability of gamma-Al2O3 and high loading of Cu in the catalyst can be achieved by adding La2O3. The microwave assisted ClO2 catalytic oxidation process with CuOn-La2O3/gamma-Al2O3 used as catalyst was also investigated, and the results show that the catalyst has an excellent catalytic activity in treating synthetic wastewater containing 100 mg/L phenol, and 91.66% of phenol and 50.35% of total organic carbon (TOC) can be removed under the optimum process conditions. Compared with no catalyst process, CuOn-La2O3/gamma-Al2O3 can effectively degrade contaminants in short reaction time and with low oxidant dosage, extensive pH range. The comparison of phenol removal efficiency in the different process indicates that microwave irradiation and catalyst work together to oxidize phenol effectively. It can therefore be concluded from results and discussion that CuOn-La2O3/gamma-Al2O3 is a suitable catalyst in microwave assisted ClO2 catalytic oxidation process.

  19. Wetting of microstructured alumina fabricated by epitaxial growth of Al4B2O9 whiskers

    NASA Astrophysics Data System (ADS)

    Wang, Yifeng; Feng, Jicai; Chen, Zhe; Song, Xiaoguo; Cao, Jian

    2015-12-01

    Topographical microstructures were fabricated on alumina by epitaxial growth of Al4B2O9 whiskers in air. The products were characterized via scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The whiskers were found to grow along the [0 0 1] crystallographic direction, and the lattice mismatch between Al2O3 and Al4B2O9 was determined to be 0.03%. The wetting of the Al4B2O9-whisker-coated surfaces by Ag-36.7Cu-8.0Ti at.% alloy was studied. The time needed to reach the equilibrium stage reduced as the temperature increased, and the final contact angle for liquid alloy on the rough surface was 27° at 880 °C. The wetting dynamics of the whiskers coated surfaces was investigated. After wetting, a whisker-interconnected region was formed between alumina and the alloy.

  20. Conducting On-orbit Gene Expression Analysis on ISS: WetLab-2

    NASA Technical Reports Server (NTRS)

    Parra, Macarena; Almeida, Eduardo; Boone, Travis; Jung, Jimmy; Lera, Matthew P.; Ricco, Antonio; Souza, Kenneth; Wu, Diana; Richey, C. Scott

    2013-01-01

    WetLab-2 will enable expanded genomic research on orbit by developing tools that support in situ sample collection, processing, and analysis on ISS. This capability will reduce the time-to-results for investigators and define new pathways for discovery on the ISS National Lab. The primary objective is to develop a research platform on ISS that will facilitate real-time quantitative gene expression analysis of biological samples collected on orbit. WetLab-2 will be capable of processing multiple sample types ranging from microbial cultures to animal tissues dissected on orbit. WetLab-2 will significantly expand the analytical capabilities onboard ISS and enhance science return from ISS.

  1. Wet foams hydrophobized by amphiphiles to give Al2O3 porous ceramics

    NASA Astrophysics Data System (ADS)

    Pokhrel, Ashish; Park, Jung Gyu; Kim, Ik Jin

    2012-05-01

    Wet chemical method to prepare ceramic foams with antecedent stability using inorganic particles (Al2O3,SiO2 etc.) which are in situ hydrophobized upon adsorption of short-chain amphiphilic molecules in the wet state and heightened mechanical property in the sintered state was developed. These wet foams are stable over several days and show no bubble coarsening nor drainage or creaming. This long-term stability is achieved through the irreversible adsorption of partially hydrophobized colloidal particles to the air-water interface using short-chain amphiphiles to in situ modify the wetting behavior of the particle surface based on the observations of Pickering emulsions. As a result, the suspension is foamed homogeneously throughout its entire volume and porous bulk materials can be produced upon drying and sintering. Wet foams featuring average bubble sizes between 30 and 300μm and sintered foams with porosity from 50 to 85% were obtained by adjusting the amphiphile - particle concentration, and additives in the initial suspension. Cells were mostly closed with an average size of approximately 150 μm. Single cells were separated by walls with minimum thicknesses of 1-3 μm.

  2. Highly efficient and stable DSSCs of wet-chemically synthesized MoS2 counter electrode.

    PubMed

    Patil, Supriya A; Kalode, Pranav Y; Mane, Rajaram S; Shinde, Dipak V; Doyoung, Ahn; Keumnam, Cho; Sung, M M; Ambade, Swapnil B; Han, Sung-Hwan

    2014-04-14

    A competitive power conversion efficiency of 7.01% is achieved for TiO2-based dye-sensitized solar cells (DSSCs) using a chemically stable and mechanically robust molybdenum di-sulfide (MoS2) counter electrode, synthesized using a simple, scalable and low-temperature wet-chemical process, owing to its good redox reaction stability.

  3. Al-doped TiO2 mesoporous material supported Pd with enhanced catalytic activity for complete oxidation of ethanol

    NASA Astrophysics Data System (ADS)

    Zhu, Jing; Mu, Wentao; Su, Liqing; Li, Xingying; Guo, Yuyu; Zhang, Shen; Li, Zhe

    2017-04-01

    Pd catalysts supported on Al-doped TiO2 mesoporous materials were evaluated in complete oxidation of ethanol. The catalysts synthesized by wet impregnation based on evaporation-induced self-assembly were characterized by X-ray diffraction, measurement of pore structure, XPS, FT-IR, temperature programmed reduction and TEM. Characteristic results showed that the aluminium was doped into the lattice of mesoporous anatase TiO2 to form Al-O-Ti defect structure. Catalytic results revealed that Al-doped catalysts were much more active than the pristine one, especially at low temperature (≤200 °C). This should be ascribed to the introduction of aluminium ions that suppressed the strong metal-support interaction and increased the active sites of Pd oxides, enhanced the stabilized anatase TiO2, improved well dispersed high valence palladium species with high reducibility and enriched chemisorption oxygen.

  4. Pilot Plant Testing of Elemental Mercury Reemission from a Wet Scrubber (2)

    EPA Science Inventory

    This paper discusses the recent observations of elemental mercury (HgO) reemissions from a pilot-scale limestone wet scrubber. Simulated flue gas was generated by burning natural gas in a down-fired furnace and doped with 2000 ppm of sulfur dioxide (S02). Mercuric chloride (HgCl2...

  5. Pilot Plant Testing of Elemental Mercury Reemission from a Wet Scrubber (2)

    EPA Science Inventory

    This paper discusses the recent observations of elemental mercury (HgO) reemissions from a pilot-scale limestone wet scrubber. Simulated flue gas was generated by burning natural gas in a down-fired furnace and doped with 2000 ppm of sulfur dioxide (S02). Mercuric chloride (HgCl2...

  6. Effect of core-shell structure and chitosan addition on catalytic activities of copper-containing silica-aluminosilicate composites in deNO(x) reaction by H2.

    PubMed

    Chamnankid, Busaya; Samanpratan, Rattanaporn; Kongkachuichay, Paisan

    2012-12-01

    Mesoporous silica-aluminosilicate composites were used as supports for selective catalytic reduction of NO by H2 using copper catalyst. Effect of loading techniques and structures of the supports on the catalytic performance were investigated. The nature, the oxidation state of copper, the structural properties and the morphology of the catalysts were characterized by means of UV-vis spectra, Fourier Transform Infrared Spectroscopy (FTIR), nitrogen sorption, and transmission electron microscopy, respectively. By using substitution technique, the copper(II) species were introduced into the silica-aluminosilicate framework by replacing aluminum atoms that located in the tetrahedral coordination. On the other hand, by using incipient wetness impregnation method, the copper species were deposited on the surface of composite materials. Upon testing their performances in deNO(x) reaction, the catalysts prepared by incipient wetness impregnation method showed higher catalytic activity than those prepared by substitution technique in any copper content. The core-shell structure was able to enhance the catalytic performance. It was found that, among the tested catalysts, the 1.5% Cu loaded core-shell mesoporous silica aluminosilicate composites prepared by an incipient wetness impregnation yielded the highest NO conversion of approximately 59%. However, the addition of chitosan creating macroporosity and controlling the uniform small clusters did not improve the catalytic performance.

  7. The atmospheric sulfur cycle over the Amazon Basin. 2. Wet season

    SciTech Connect

    Andreae, M.O.; Berresheim, H.; Lewis, B.L.; Li, S. ); Jacob, D.J. ); Talbot, R.W. ); Bingemer, H.

    1990-09-20

    The authors determined the fluxes and concentrations of atmospheric sulfur species at ground level and from aircraft over the Amazon Basin during the 1987 wet season, providing a comprehensive description of the sulfur cycle over a remote tropical region. The vertical profile of dimethylsulfide (DMS) during the wet season was found to be very similar to that measured during the dry season. The concentrations of hydrogen sulfide (H{sub 2}S) were almost an order of magnitude higher than those of DMS, which makes H{sub 2}S the most important biogenic source species in the atmospheric sulfur cycle over the Amazon Basin. Using the gradient-flux approach, estimated the flux of DMS at the top of the tree canopy. The canopy was a source of DMS during the day, and a weak sink during the night. Measurements of sulfur gas emissions from soils, using the chamber method, showed very small fluxes, consistent with the hypothesis that the forest canopy is the major source of sulfur gases. The observed soil and canopy emission fluxes are similar to those measured in temperate regions. The concentrations of SO{sub 2} and sulfate aerosol in the wet season atmosphere were similar to dry season values. The sulfate concentration in rainwater, on the other hand, was lower by about a factor of 5 during the wet season. Due to the higher precipitation rate, however, the wet deposition flux of sulfate was not significantly different between the seasons. The measured fluxes and concentrations of DMS, H{sub 2}S, and SO{sub 2} were consistent with a model describing transport and chemistry of these sulfur species in the boundary layer. The concentrations of aerosol and the sulfate deposition rate, on the other hand, could only be explained by import of significant amounts of marine and anthropogenic sulfate aerosol into the Amazon Basin.

  8. Catalytic thermal cracking of post-consumer waste plastics to fuels. 2. Pilot study

    USDA-ARS?s Scientific Manuscript database

    Alternative gasoline and diesel fuels were prepared via catalytic and non-catalytic pyrolysis and distillation of waste polyethylene and polypropylene plastics. Reaction conditions were optimized using a bench-scale (2 L) batch reactor and then applied to pilot-scale production of crude plastic oil....

  9. Human alpha-L-iduronidase. 2. Catalytic properties.

    PubMed

    Clements, P R; Muller, V; Hopwood, J J

    1985-10-01

    The kinetic parameters of human liver alpha-L-iduronidase were determined with three disaccharide substrates: alpha-L-iduronosyl(1----4)2,5-anhydro-D-[1-3H]mannitol 6-sulphate, alpha-L-iduronosyl(1----4)2,5-anhydro-D-[1-3H]mannitol and alpha-L-iduronosyl(1----3)2,5-anhydro-D-[1-3H]talitol 4-sulphate, derived from the natural substrates heparin and dermatan sulphate and one synthetic, fluorogenic substrate, 4-methylumbelliferyl alpha-L-iduronide. The enzyme activity with all four substrates was optimal at about pH 4.5. The Km values derived using the disaccharide substrates were elevated up to 10-fold with up to a 6.5-fold increase in ionic strength whereas that for the synthetic substrate was only increased by 1.7-fold. The V values for all substrates were unaffected. The inhibitory effect of NaCl, Na2SO4, NaH2PO4 or CuCl2 on enzyme activity was more pronounced with the disaccharide substrates than with the synthetic substrate. The moiety which is most important in binding is the idopyranosyl residue. While the aglycone residue adds to the net affinity for the enzyme, it is the substituent groups of both residues which appear to control catalysis. Specifically the carboxyl moiety of the alpha-L-iduronic acid residue is essential for catalysis while the presence of sulphate on the C4 or C6 position of the aglycone residue has a major influence on catalysis rather than binding. alpha-L-Idosyl(1----4)2,5-anhydro-D-[1-3H]mannitol 6-sulphate did not undergo catalysis and was a potent inhibitor of enzyme activity, whereas beta-glucuronosyl(1----4)2,5-anhydro-D-[1-3H]mannitol 6-sulphate, alpha-L-iduronosyl-2-sulphate(1----4)2,5-anhydro-D-[1-3H]-mannitol 6-sulphate and 4-methylumbelliferyl alpha-L-idoside did not undergo catalysis and were not inhibitory. A model of the catalytic requirements of alpha-L-iduronidase is proposed.

  10. Synthesis and catalytic performance of SiO2@Ni and hollow Ni microspheres

    NASA Astrophysics Data System (ADS)

    Liu, Xin; Liu, Yanhua; Shi, Xueting; Yu, Zhengyang; Feng, Libang

    2016-11-01

    Nickel (Ni) catalyst has been widely used in catalytic reducing reactions such as catalytic hydrogenation of organic compounds and catalytic reduction of organic dyes. However, the catalytic efficiency of pure Ni is low. In order to improve the catalytic performance, Ni nanoparticle-loaded microspheres can be developed. In this study, we have prepared Ni nanoparticle-loaded microspheres (SiO2@Ni) and hollow Ni microspheres using two-step method. SiO2@Ni microspheres with raspberry-like morphology and core-shell structure are synthesized successfully using SiO2 microsphere as a template and Ni2+ ions are adsorbed onto SiO2 surfaces via electrostatic interaction and then reduced and deposited on surfaces of SiO2 microspheres. Next, the SiO2 cores are removed by NaOH etching and the hollow Ni microspheres are prepared. The NaOH etching time does no have much influence on the crystal structure, shape, and surface morphology of SiO2@Ni; however, it can change the phase composition evidently. The hollow Ni microspheres are obtained when the NaOH etching time reaches 10 h and above. The as-synthesized SiO2@Ni microspheres exhibit much higher catalytic performance than the hollow Ni microspheres and pure Ni nanoparticles in the catalytic reduction of methylene blue. Meanwhile, the SiO2@Ni catalyst has high stability and hence it can be recycled for reuse.

  11. Exploring the catalytic center of TaqI endonuclease: rescuing catalytic activity by double mutations and Mn2+.

    PubMed

    Cao, W; Lu, J

    2001-03-09

    TaqI is a metal-dependent endonuclease that recognizes T(downward arrow)CGA, with the arrow indicating the cleavage site. Mutations at K158 render the enzyme inactive and mutations at K157 significantly reduce DNA cleavage activity (W. Cao and F. Barany (1998) J. Biol. Chem. 273, 33002-33010). Aspartate, glutamate, and histidine substitutions were made at K158 in the wild-type and K157S mutant TaqI endonuclease to understand the functional organization of the active site. None of the mutants was active with Mg(2+), but the DNA cleavage activities were partly rescued by Mn2+ for K157S-K158E and K157S-K158H mutants. The rescuing effects were observed with Mn2+ but not with other divalent cations. K157S-K158E required higher Mn2+ concentrations than the wild-type enzyme for DNA cleavage activity, suggesting that a Mn2+ ion is weakly bound at the 158 position. The need to neutralize K157 to recover the catalytic activity of K158E and K158H indicates that K158 and K157 may interact functionally. In analogy with EcoRV, Ca2+ stimulated Mn2+-mediated cleavage for the wild-type TaqI, suggesting the existence of at least two metal ions at the catalytic center. A catalytic mechanism involving two metal ions and the K157-K158 pair is proposed for TaqI endonuclease.

  12. Study of catalytic decomposition of formaldehyde on Pt/TiO2 alumite catalyst at ambient temperature.

    PubMed

    Wang, Lifeng; Sakurai, Makoto; Kameyama, Hideo

    2009-08-15

    Formaldehyde (HCHO) emitted from buildings, furnishing materials and consumer products is one of the most dominant volatile organic compounds (VOCs) in an indoor environment. In this work, a Pt/TiO(2)/Al(2)O(3) catalyst was prepared on an anodic alumite plate and was employed in the catalytic decomposition of formaldehyde at ambient temperature. Firstly, TiO(2) was deposited on the anodic alumite plate with electro-deposition technology. Then, platinum was supported on the anodic alumite plate with wet impregnation method. The developed catalyst exhibits good activity towards the decomposition of HCHO at ambient temperature. TPR (temperature programmed reduction) and TPD (temperature programmed desorption) analysis results indicate that oxygen adsorbed on the Pt/TiO(2)/Al(2)O(3) catalyst can be activated and generated to O:Pt(surface) species quickly at ambient temperature. Hence, the developed catalyst experiences the high activity towards the catalytic decomposition of formaldehyde at ambient temperature. Moreover, in accordance with the process requirements, the developed catalyst can be formed into various shapes such as a mesh, plate, fin, serrate etc., because aluminum can be formed into any shapes. The serrate type catalyst was prepared in this work and it also exhibits fine activity towards the decomposition of HCHO.

  13. Wetting of the (0001) α-Al2O3 Sapphire Surface by Molten Aluminum: Effect of Surface Roughness

    NASA Astrophysics Data System (ADS)

    Aguilar-Santillan, Joaquin

    2010-03-01

    The wetting of molten aluminum on the “ c”-plane (0001) of single-crystal α-Al2O3 (sapphire) was studied by the sessile drop technique from 800 °C (1073 K) to 1200 °C (1473 K). Systematically increasing the (0001) surface roughness by SiC abrasion increased the wetting contact angle, resulting in reduced wetting. The surface roughness factor R originally defined by Wenzel, was determined as a function of the abrasion, temperature, and time. The wetting decreases as the surface roughness increases. Rough surfaces also create time and temperature effects on wetting, changing those for a smoothly polished surface. The existence of a high-temperature surface structural transition for (0001) of α-Al2O3, which has been previously suggested, was confirmed. Increased roughness R accents the effect of the surface structural transition, increasing the wetting contact angle changes during the transition.

  14. Reaction kinetics of waste sulfuric acid using H2O2 catalytic oxidation.

    PubMed

    Wang, Jiade; Hong, Binxun; Tong, Xinyang; Qiu, Shufeng

    2016-12-01

    The process of recovering waste sulfuric acids using H2O2 catalytic oxidation is studied in this paper. Activated carbon was used as catalyst. Main operating parameters, such as temperature, feed rate of H2O2, and catalyst dosage, have effects on the removal of impurities from waste sulfuric acids. The reaction kinetics of H2O2 catalytic oxidation on impurities are discussed. At a temperature of 90°C, H2O2 feeding rate of 50 g (kg waste acid)(-1) per hour, and catalyst dosage of 0.2 wt% (waste acid weight), the removal efficiencies of COD and chrominance were both more than 99%, the recovery ratio of sulfuric acid was more than 95%, and the utilization ratio of H2O2 was 88.57%. Waste sulfuric acid is a big environmental problem in China. The amount of waste sulfuric acid is huge every year. Many small and medium-sized businesses produced lots of waste acids, but they don't have an appropriate method to treat and recover them. H2O2 catalytic oxidation has been used to treat and recover waste sulfuric acid and activated carbon is the catalyst here. Main parameters, such as temperature, feed rate of H2O2, and catalyst dosage, have been investigated. The reaction kinetics are discussed. This method can be economical and feasible for most small and medium-sized businesses.

  15. In situ infrared spectroscopic study of forsterite carbonation in wet supercritical CO2.

    PubMed

    Loring, John S; Thompson, Christopher J; Wang, Zheming; Joly, Alan G; Sklarew, Deborah S; Schaef, H Todd; Ilton, Eugene S; Rosso, Kevin M; Felmy, Andrew R

    2011-07-15

    Carbonation reactions are central to the prospect of CO(2) trapping by mineralization in geologic reservoirs. In contrast to the relevant aqueous-mediated reactions, little is known about the propensity for carbonation in the key partner fluid: supercritical carbon dioxide containing dissolved water ("wet" scCO(2)). We employed in situ mid-infrared spectroscopy to follow the reaction of a model silicate mineral (forsterite, Mg(2)SiO(4)) for 24 h with wet scCO(2) at 50 °C and 180 atm. The results show a dramatic dependence of reactivity on water concentration and the presence of liquid water on the forsterite particles. Exposure to neat scCO(2) showed no detectable carbonation reaction. At 47% and 81% water saturation, an Ångstrom-thick liquid-like water film was detected on the forsterite particles and less than 1% of the forsterite transformed. Most of the reaction occurred within the first 3 h of exposure to the fluid. In experiments at 95% saturation and with an excess of water (36% above water saturation), a nanometer-thick water film was detected, and the carbonation reaction proceeded continuously with approximately 2% and 10% conversion, respectively. Our collective results suggest constitutive links between water concentration, water film formation, reaction rate and extent, and reaction products in wet scCO(2).

  16. Insight into the Mechanism of Intramolecular Inhibition of the Catalytic Activity of Sirtuin 2 (SIRT2).

    PubMed

    Li, Jinyu; Flick, Franziska; Verheugd, Patricia; Carloni, Paolo; Lüscher, Bernhard; Rossetti, Giulia

    2015-01-01

    Sirtuin 2 (SIRT2) is a NAD+-dependent deacetylase that has been associated with neurodegeneration and cancer. SIRT2 is composed of a central catalytic domain, the structure of which has been solved, and N- and C-terminal extensions that are thought to control SIRT2 function. However structural information of these N- and C-terminal regions is missing. Here, we provide the first full-length molecular models of SIRT2 in the absence and presence of NAD+. We also predict the structural alterations associated with phosphorylation of SIRT2 at S331, a modification that inhibits catalytic activity. Bioinformatics tools and molecular dynamics simulations, complemented by in vitro deacetylation assays, provide a consistent picture based on which the C-terminal region of SIRT2 is suggested to function as an autoinhibitory region. This has the capacity to partially occlude the NAD+ binding pocket or stabilize the NAD+ in a non-productive state. Furthermore, our simulations suggest that the phosphorylation at S331 causes large conformational changes in the C-terminal region that enhance the autoinhibitory activity, consistent with our previous findings that phosphorylation of S331 by cyclin-dependent kinases inhibits SIRT2 catalytic activity. The molecular insight into the role of the C-terminal region in controlling SIRT2 function described in this study may be useful for future design of selective inhibitors targeting SIRT2 for therapeutic applications.

  17. Synthesis and visible-light-induced catalytic activity of Ag2S-coupled TiO2 nanoparticles and nanowires

    NASA Astrophysics Data System (ADS)

    Xie, Yi; Heo, Sung Hwan; Kim, Yong Nam; Yoo, Seung Hwa; Cho, Sung Oh

    2010-01-01

    We present the synthesis and visible-light-induced catalytic activity of Ag2S-coupled TiO2 nanoparticles (NPs) and TiO2 nanowires (NWs). Through a simple wet chemical process from a mixture of peroxo titanic acid (PTA) solution, thiourea and AgAc, a composite of Ag2S NPs and TiO2 NPs with sizes of less than 7 nm was formed. When the NP composite was further treated with NaOH solution followed by annealing at ambient conditions, a new nanocomposite material comprising Ag2S NPs on TiO2 NWs was created. Due to the coupling with such a low bandgap material as Ag2S, the TiO2 nanocomposites could have a visible-light absorption capability much higher than that of pure TiO2. As a result, the synthesized Ag2S/TiO2 nanocomposites exhibited much higher catalytic efficiency for the decomposition of methyl orange than commercial TiO2 (Degussa P25, Germany) under visible light.

  18. Designing Catalytic Monoliths For Closed-Cycle CO2 Lasers

    NASA Technical Reports Server (NTRS)

    Guinn, Keith; Herz, Richard K.; Goldblum, Seth; Noskowski, ED

    1992-01-01

    LASCAT (Design of Catalytic Monoliths for Closed-Cycle Carbon Dioxide Lasers) computer program aids in design of catalyst in monolith by simulating effects of design decisions on performance of laser. Provides opportunity for designer to explore tradeoffs among activity and dimensions of catalyst, dimensions of monolith, pressure drop caused by flow of gas through monolith, conversion of oxygen, and other variables. Written in FORTRAN 77.

  19. Enhanced NO{sub x} removal in wet scrubbers using metal chelates. Final report, Volume 2

    SciTech Connect

    1992-12-01

    Successful pilot plant tests of simultaneous removal of SO{sub 2} and NO{sub x} in a wet lime flue gas desulfurization system were concluded in December. The test, at up to 1.5 MW(e) capacity, were conducted by the Cincinnati Gas and Electric Company and Dravo Lime Company for the US Department of Energy at a pilot plant facility at the Miami Fort station of CG&E near Cincinnati, Ohio. The pilot plant scrubbed a slipstream of flue gas from Unit 7 a 530 MW coal-fired electric generating unit. Tests were conducted in three phases between April and December. The technology tested was wet scrubbing with Thiosorbic{reg_sign} magnesium-enhanced lime for SO{sub 2} removal and simultaneous NO scrubbing with ferrous EDTA, a metal chelate. Magnesium-enhanced lime-based wet scrubbing is used at 20 full-scale high-sulfur coal-fired electric generating units with a combined capacity of 8500 MW. Ferrous EDTA reacts with nitric oxide, NO, which comprises about 96% of NO{sub x} from coal-fired boilers. In this report, although not precise, NO and NO{sub x} are used interchangeably. A major objective of the tests was to combine NO{sub x} removal using ferrous EDTA, a developing technology, with SO{sub 2} removal using wet lime FGD, already in wide commercial use. If successful, this could allow wide application of this NO{sub x} removal technology. Volume 2 covers: description and results of NO{sub x} removal tests; and description and results of waste characterization studies.

  20. [Catalytic hydrodechlorination of 2,4-dichlorophenol over Pd/TiO2].

    PubMed

    Zhang, Yin; Shao, Yun; Chen, Huan; Wan, Hai-Qin; Wan, Yu-Qiu; Zheng, Shou-Rong

    2012-01-01

    Pd/TiO2 catalysts were prepared by the deposition-precipitation and impregnation methods, and were further characterized by TEM, XRD and ICP-AES. The liquid catalytic hydrodechlorination of 2,4-dichlorophenol over the catalysts was investigated. It is demonstrated that despite catalyst prepared by deposition-precipitation method exhibits higher activity than that synthesized from impregnation method, both catalysts show good performance in hydrodechlorination process. When initial concentration of the reactant was 3.11 mmol x L(-1), pH was 12 and amount of catalyst used was 50 mg, hydrodechlorination of 2,4-dichlorophenol was completed within 45 min. Acidic condition facilitates hydrodechlorination process. The initial activity was not significantly influenced when the amount of catalyst used varied between 15-80 mg, which proves that mass transport limitation exerts little impact on hydrodechlorination reaction. Finally, the initial activity sharply enhanced with the increase of initial concentration of 2,4-dichlorophenol when the concentration was in the range of 0.62-3.11 mmo x L(-1) while it almost remained constant with further increasing the initial concentration. Therefore, the catalytic hydrodechlorination of 2,4-dichlorophenol over Pd/TiO2-DP follows the Langumuir-Hinshelwood model, indicating that the catalytic hydrodechlorination is controlled by 2,4-dichlorophenol adsorption.

  1. Wetting transitions at the argon-solid-CO2 interface: Molecular-dynamics studies

    NASA Astrophysics Data System (ADS)

    Sokołowski, Stefan; Fischer, Johann

    1990-06-01

    The wetting behavior of argon at the solid CO2 surface has been studied with a constant-temperature molecular-dynamics technique. In order to obtain results as accurately as possible, except from the minimum image convention, no additional cutoff of the intermolecular potential was used in the calculations that were all performed with vectorized codes on the Cyber 205 supercomputer. First, the orthobaric densities are determined consistently by simulating the free-liquid surface at three temperatures. Then the density profiles of the adsorbed gas are presented for bulk-gas densities approaching the dew density. With some caution, the results seem to confirm the existence of the thin-film to thick-film transition found by recent density-functional theories. The wetting temperature of that specific system is located to be between 0.95 and 1.00 in units of the reduced temperature.

  2. Enhancement of ribozyme catalytic activity by a contiguous oligodeoxynucleotide (facilitator) and by 2'-O-methylation.

    PubMed Central

    Goodchild, J

    1992-01-01

    RNA catalysts (ribozymes) designed to cleave sequences unique to viral RNA's might be developed as therapeutics. For this purpose, they would require high catalytic efficiency and resistance to nucleases. Reported here are two approaches that can be used in combination to improve these properties. First, catalytic efficiency can be improved by oligonucleotides (facilitators) that bind to the substrate contiguously with the 3'-end of the ribozyme. Second, 2'-O-methylation of flanking sequences of the ribozyme increases catalytic activity as well as resistance to nucleases. In combination with a facilitator oligodeoxynucleotide, the cleavage rate was increased 20 fold over that of the unmodified ribozyme. Images PMID:1383929

  3. Dynamics of Catalytic Resolution of 2-Lithio-N-Boc-piperidine by Ligand Exchange

    PubMed Central

    Beng, Timothy K.; Tyree, William S.; Parker, Trent; Su, Chicheung; Williard, Paul G.

    2012-01-01

    The dynamics of the racemization, catalytic and stoichiometric dynamic resolution of 2-lithio-N-Boc-piperidine, 7, have been investigated. The kinetic order in TMEDA, for both racemization and resolution of the title compound, and the kinetic order in resolving ligands, have been determined. The catalytic dynamic resolution is 0.5-order in chiral ligand 8, 0.265 order in chiral ligand 10, and second order in TMEDA. The X-ray crystal structure of ligand 10 shows it to be an octamer. Dynamic NMR studies of the resolution process were obtained. Some of the requirements for a successful catalytic dynamic resolution by ligand exchange have been identified. PMID:22967289

  4. Catalytic performance of carbon nanotubes in H2O2 decomposition: experimental and quantum chemical study.

    PubMed

    Voitko, Katerina; Tóth, Ajna; Demianenko, Evgenij; Dobos, Gábor; Berke, Barbara; Bakalinska, Olga; Grebenyuk, Anatolij; Tombácz, Etelka; Kuts, Volodymyr; Tarasenko, Yurij; Kartel, Mykola; László, Krisztina

    2015-01-01

    The catalytic performance of multi-walled carbon nanotubes (MWCNTs) with different surface chemistry was studied in the decomposition reaction of H2O2 at various values of pH and temperature. A comparative analysis of experimental and quantum chemical calculation results is given. It has been shown that both the lowest calculated activation energy (∼18.9 kJ/mol) and the highest rate constant correspond to the N-containing CNT. The calculated chemisorption energy values correlate with the operation stability of MWCNTs. Based on the proposed quantum chemical model it was found that the catalytic activity of carbon materials in electron transfer reactions is controlled by their electron donor capability.

  5. All the catalytic active sites of MoS2 for hydrogen evolution

    DOE PAGES

    Li, Guoqing; Zhang, Du; Qiao, Qiao; ...

    2016-11-29

    MoS2 presents a promising low-cost catalyst for the hydrogen evolution reaction (HER), but the understanding about its active sites has remained limited. Here we present an unambiguous study of the catalytic activities of all possible reaction sites of MoS2, including edge sites, sulfur vacancies, and grain boundaries. We demonstrate that, in addition to the well-known catalytically active edge sites, sulfur vacancies provide another major active site for the HER, while the catalytic activity of grain boundaries is much weaker. Here, the intrinsic turnover frequencies (Tafel slopes) of the edge sites, sulfur vacancies, and grain boundaries are estimated to be 7.5more » s–1 (65–75 mV/dec), 3.2 s–1 (65–85 mV/dec), and 0.1 s–1 (120–160 mV/dec), respectively. We also demonstrate that the catalytic activity of sulfur vacancies strongly depends on the density of the vacancies and the local crystalline structure in proximity to the vacancies. Unlike edge sites, whose catalytic activity linearly depends on the length, sulfur vacancies show optimal catalytic activities when the vacancy density is in the range of 7–10%, and the number of sulfur vacancies in high crystalline quality MoS2 is higher than that in low crystalline quality MoS2, which may be related with the proximity of different local crystalline structures to the vacancies.« less

  6. Pore Scale Observations of Trapped CO2 in Mixed-Wet Carbonate Rock: Applications to Storage in Oil Fields.

    PubMed

    Al-Menhali, Ali S; Menke, Hannah P; Blunt, Martin J; Krevor, Samuel C

    2016-09-20

    Geologic CO2 storage has been identified as a key to avoiding dangerous climate change. Storage in oil reservoirs dominates the portfolio of existing projects due to favorable economics. However, in an earlier related work ( Al-Menhali and Krevor Environ. Sci. Technol. 2016 , 50 , 2727 - 2734 ) , it was identified that an important trapping mechanism, residual trapping, is weakened in rocks with a mixed wetting state typical of oil reservoirs. We investigated the physical basis of this weakened trapping using pore scale observations of supercritical CO2 in mixed-wet carbonates. The wetting alteration induced by oil provided CO2-wet surfaces that served as conduits to flow. In situ measurements of contact angles showed that CO2 varied from nonwetting to wetting throughout the pore space, with contact angles ranging 25° < θ < 127°; in contrast, an inert gas, N2, was nonwetting with a smaller range of contact angle 24° < θ < 68°. Observations of trapped ganglia morphology showed that this wettability allowed CO2 to create large, connected, ganglia by inhabiting small pores in mixed-wet rocks. The connected ganglia persisted after three pore volumes of brine injection, facilitating the desaturation that leads to decreased trapping relative to water-wet systems.

  7. Catalytic nanoreactors in continuous flow: hydrogenation inside single-walled carbon nanotubes using supercritical CO2.

    PubMed

    Chamberlain, Thomas W; Earley, James H; Anderson, Daniel P; Khlobystov, Andrei N; Bourne, Richard A

    2014-05-25

    One nanometre wide carbon nanoreactors are utilised as the reaction vessel for catalytic chemical reactions on a preparative scale. Sub-nanometre ruthenium catalytic particles which are encapsulated solely within single-walled carbon nanotubes offering a unique reaction environment are shown to be active when embedded in a supercritical CO2 continuous flow reactor. A range of hydrogenation reactions were tested and the catalyst displayed excellent stability over extended reaction times.

  8. An improved wet tropospheric correction for CryoSat-2 over open and coastal ocean

    NASA Astrophysics Data System (ADS)

    Joana Fernandes, M.; Lázaro, Clara; Nunes, Alexandra L.; Pires, Nelson; Dinardo, Salvatore; Benveniste, Jérôme

    2014-05-01

    In the scope of the CryoSat Plus for Oceans (CP4O) project, encouraged by the European Space Agency, a data combination (DComb) algorithm has been developed for the computation of the wet tropospheric correction (WTC) for CryoSat-2, which does not possess an onboard microwave radiometer (MWR), thus relying on a model-based WTC provided by the European Centre for Medium-Range Weather Forecasts (ECMWF). This WTC is based on the objective analysis of all available wet path delay data sources (e.g. from scanning imaging MWR (SI MWR) on board remote sensing satellites, those derived from Global Navigation Satellite Systems (GNSS) measurements at coastal stations and from an atmospheric model such as the ECMWF ReAnalysis (ERA) Interim. This presentation gives a brief description of the DComb algorithm and its application to CryoSat-2. The algorithm was first applied to Jason-2 and compared with the correction from the Jason-2 advanced microwave radiometer (AMR) present on the version D of the Geophysical Data Records (GDR-D), known to be a well calibrated and accurate correction, with improved performance in coastal regions. These results show that for epochs and locations for which SI-MWR measurements are available, the DComb WTC is very similar to that of AMR, evidencing that the SI-MWR water vapour products, previously calibrated with respect to AMR, are an extremely valuable data set for the estimation of the WTC for any altimeter mission, including those which possess an onboard MWR. For both Jason-2 and CryoSat-2 the new correction was validated through analysis of sea level anomaly variance at crossovers, function of distance from the coast and latitude. The influence of the GNSS-derived wet path delays in the coastal regions, of major importance for the full exploitation of CryoSat-2 data, in particular those acquired in the Synthetic Aperture Radar (SAR) mode, is also shown.

  9. Hg2+ reduction and re-emission from simulated wet flue gas desulfurization liquors.

    PubMed

    Wo, Jingjing; Zhang, Meng; Cheng, Xiaoya; Zhong, Xiaohang; Xu, Jiang; Xu, Xinhua

    2009-12-30

    In this study, considering that Hg(2+) in wet flue gas desulfurization (FGD) systems can easily be reduced and then released into atmosphere, causing secondary pollution, the researches about Hg(2+) reduction and Hg(0) re-emission mechanism were carried out. The effects of several experimental parameters on the reduction were studied, including initial pH, temperature, and concentrations of Cl(-) and S(IV). Our experimental results indicated that Cl(-) had a restraining effect on the Hg(2+) reduction and Hg(0) re-emission, after 24h reaction, only 20.5% of Hg(2+) was reduced with 100mM Cl(-) in simulated desulfurization solution. Cl(-) can slow Hg(2+) reduction and Hg(0) re-emissions dramatically through changing reaction mechanism, with formation of new intermediate: ClHgSO(3)(-), which can decompose to Hg(0), but much more slowly than Hg(SO(3))(2)(2-) or HgSO(3). Simulating the conditions of the practical application (initial pH 5, T=50 degrees C, S(IV)=5 mM, Cl(-)=100 mM), we also found that Ca(2+), NO(3)(-), F(-), etc. all had obvious effects on reduction rates. Based on the material balance and characteristic of the reactants, the reduction emission mechanism of Hg(2+) has been established, providing theoretical basis for industrial application of mercury control in wet FGD systems.

  10. Promotion of catalytic performance by adding W into Pt/ZrO2 catalyst for selective catalytic oxidation of ammonia

    NASA Astrophysics Data System (ADS)

    Sun, Mengmeng; Wang, Suning; Li, Yuanshan; Xu, Haidi; Chen, Yaoqiang

    2017-04-01

    Pt-WO3/ZrO2 catalyst was prepared by co-impregnation method to improve the ammonia oxidation performance of Pt/ZrO2. Differences in textural, structural, surface chemical states, redox properties and acid properties, together with the catalytic performance of Pt/ZrO2 and Pt-WO3/ZrO2 catalysts were investigated systematically. The results of H2-TPR revealed that higher reduction ability was possessed by Pt-WO3/ZrO2 than that of Pt/ZrO2 due to the influence of tungsten on platinum. The XPS results showed that electron transfer from tungsten to platinum species made higher electron density around platinum. The TEM results revealed that the active lattice plane Pt[111] was obtained by modification of W species. Consequently, Pt-WO3/ZrO2 exhibited obviously better ammonia oxidation performance compared with Pt/ZrO2, the light-off temperature of NH3 shifted from 284 °C to 249 °C, the activation energy decreased from 113.4 kJ mol-1 to 96.2 kJ mol-1.

  11. Wet chemical synthesis and characterization of AgGaSe{sub 2} nanoparticles

    SciTech Connect

    Sugan, S.; Dhanasekaran, R.

    2013-06-03

    AgGaSe{sub 2} compound semiconductor nanoparticles were synthesized by wet chemical method using mercaptoacetic acid as a capping agent at room temperature. The synthesized powders belong to chalcopyrite structure confirmed by powder XRD. The surface morphology and crystalline size were observed by high resolution scanning electron microscope (HR-SEM). The stoichiometric composition of AgGaSe{sub 2} nanoparticles was confirmed by Energy dispersive X-ray (EDX) analysis. Different functional group vibrations of mercaptoacetic acid capped nanoparticles were studied using FT-IR spectrum. The absorbance and optical bandgap of the nanoparticles were determined using diffuse reflectance spectroscopy (DRS).

  12. In Situ Infrared Spectroscopic Study of Forsterite Carbonation in Wet Supercritical CO2

    SciTech Connect

    Loring, John S.; Thompson, Christopher J.; Wang, Zheming; Joly, Alan G.; Sklarew, Deborah S.; Schaef, Herbert T.; Ilton, Eugene S.; Rosso, Kevin M.; Felmy, Andrew R.

    2011-07-19

    Carbonation reactions are central to the prospect of CO2 trapping by mineralization in geologic reservoirs. In contrast to the relevant aqueous-mediated reactions, little is known about the propensity for carbonation in the long-term partner fluid: water-containing supercritical carbon dioxide (‘wet’ scCO2). We employed in situ mid-infrared spectroscopy to follow the reaction of a model silicate mineral (forsterite, Mg2SiO4) for 24 hr with wet scCO2 at 50°C and 180 atm, using water concentrations corresponding to 0%, 55%, 95%, and 136% saturation. Results show a dramatic dependence of reactivity on water concentration and the presence of liquid water on the forsterite particles. Exposure to neat scCO2 showed no detectable carbonation reaction. At 55% and 95% water saturation, a liquid-like thin water film was detected on the forsterite particles; less than 1% of the forsterite transformed, mostly within the first 3 hours of exposure to the fluid. At 136% saturation, where an (excess) liquid water film approximately several nanometers thick was intentionally condensed on the forsterite, the carbonation reaction proceeded continuously for 24 hr with 10% to 15% transformation. Our collective results suggest constitutive links between water concentration, water film formation, reaction rate and extent, and reaction products in wet scCO2.

  13. Selection of active phase of MnO2 for catalytic ozonation of 4-nitrophenol.

    PubMed

    Nawaz, Faheem; Cao, Hongbin; Xie, Yongbing; Xiao, Jiadong; Chen, Yue; Ghazi, Zahid Ali

    2017-02-01

    Catalytic ozonation is a highly effective method in wastewater treatment, and MnO2 materials are widely recognized as active heterogeneous catalysts in this process. Many works reported the progress in active MnO2 synthesis, but the active phase is rarely systematically studied. In this paper, all six phases of MnO2 (α-, β-, δ-, γ-, λ- and ε-) were synthesized by facile methods. Their catalytic activities in ozonation of 4-nitrophenol (4-NP) were evaluated and correlated with the physicochemical properties obtained from X-ray Diffraction (XRD), transmission electron microscopy (TEM), physical adsorption and cyclic voltammetry (CV) analysis. α- MnO2 was found to be the most active catalyst in 4-NP degradation at neutral pH. MnO2 with low average oxidation state (AOS) showed stronger oxidation/reduction peaks in CV characterization, which benefited catalytic decomposition of ozone to generate active species. Superoxide radical was confirmed as the main oxidizing species, along with singlet oxygen and ozone molecule oxidation in bulk solution and little contribution of oxidation on the MnO2 surface. Mn(2+) leaching happened during catalytic ozonation, but its catalytic role is negligible. This result may give rise to the preparation of new active MnO2 catalysts.

  14. A Mg2+-induced conformational switch rendering a competent DNA polymerase catalytic complex.

    PubMed

    Mendieta, Jesús; Cases-González, Clara E; Matamoros, Tania; Ramírez, Galo; Menéndez-Arias, Luis

    2008-05-01

    The structural and dynamical changes occurring before nucleotide addition were studied using molecular dynamics (MD) simulations of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) complexes containing one or two Mg2+ ions in the presence of dNTP. Our models revealed that the formation of a catalytically competent DNA polymerase complex required subtle rearrangements at the catalytic site A, which occurred only when an Mg2+ ion was bound. This model has been validated using pre-steady-state kinetics to show that free Mg2+ is necessary to obtain a catalytically competent polymerase. Kinetic studies carried out with Be2+ as a cofactor permitted the functional discrimination between metal sites A and B. At low concentrations, Be2+ increased the catalytic efficiency of the polymerase, while at higher concentrations, it competed with Mg2+ for binding to site A, and inhibited DNA polymerization. In agreement with experimental data, MD simulations revealed that the catalytic attack distance between the 3-OH of the primer and the phosphorus in complexes containing Be2+ instead of Mg2+ at site A was above 4.5 A. Our findings provide a detailed description of the mechanism of DNA polymerization and should be helpful to understand the molecular basis of DNA replication fidelity.

  15. Catalytic reduction of CN−, CO and CO2 by nitrogenase cofactors in lanthanide-driven reactions**

    PubMed Central

    Lee, Chi Chung

    2014-01-01

    Nitrogenase cofactors can be extracted into an organic solvent and added in an adenosine triphosphate (ATP)-free, organic solvent-based reaction medium to catalyze the reduction of cyanide (CN−), carbon monoxide (CO) and carbon dioxide (CO2) when samarium (II) iodide (SmI2) and 2,6-lutidinium triflate (Lut-H) are supplied as a reductant and a proton source, respectively. Driven by SmI2, the cofactors not only catalytically reduce CN− or CO to C1-C4 hydrocarbons, but also catalytically reduce CO2 to CO and C1-C3 hydrocarbons. The observation of C-C coupling from CO2 reveals a unique, Fischer-Tropsch-like reaction with an atypical carbonaceous substrate; whereas the achievement of catalytic turnover of CN−, CO and CO2 by isolated cofactors suggests the possibility to develop nitrogenase-based electrocatalysts for hydrocarbon production from these carbon-containing compounds. PMID:25420957

  16. The catalytic role of the M2 metal ion in PP2Cα.

    PubMed

    Pan, Chang; Tang, Jun-yi; Xu, Yun-fei; Xiao, Peng; Liu, Hong-da; Wang, Hao-an; Wang, Wen-bo; Meng, Fan-guo; Yu, Xiao; Sun, Jin-peng

    2015-02-24

    PP2C family phosphatases (the type 2C family of protein phosphatases; or metal-dependent phosphatase, PPM) constitute an important class of signaling enzymes that regulate many fundamental life activities. All PP2C family members have a conserved binuclear metal ion active center that is essential for their catalysis. However, the catalytic role of each metal ion during catalysis remains elusive. In this study, we discovered that mutations in the structurally buried D38 residue of PP2Cα (PPM1A) redefined the water-mediated hydrogen network in the active site and selectively disrupted M2 metal ion binding. Using the D38A and D38K mutations of PP2Cα as specific tools in combination with enzymology analysis, our results demonstrated that the M2 metal ion determines the rate-limiting step of substrate hydrolysis, participates in dianion substrate binding and stabilizes the leaving group after P-O bond cleavage. The newly characterized catalytic role of the M2 metal ion in this family not only provides insight into how the binuclear metal centers of the PP2C phosphatases are organized for efficient catalysis but also helps increase our understanding of the function and substrate specificity of PP2C family members.

  17. The catalytic role of the M2 metal ion in PP2

    NASA Astrophysics Data System (ADS)

    Pan, Chang; Tang, Jun-Yi; Xu, Yun-Fei; Xiao, Peng; Liu, Hong-Da; Wang, Hao-An; Wang, Wen-Bo; Meng, Fan-Guo; Yu, Xiao; Sun, Jin-Peng

    2015-02-01

    PP2C family phosphatases (the type 2C family of protein phosphatases; or metal-dependent phosphatase, PPM) constitute an important class of signaling enzymes that regulate many fundamental life activities. All PP2C family members have a conserved binuclear metal ion active center that is essential for their catalysis. However, the catalytic role of each metal ion during catalysis remains elusive. In this study, we discovered that mutations in the structurally buried D38 residue of PP2Cα (PPM1A) redefined the water-mediated hydrogen network in the active site and selectively disrupted M2 metal ion binding. Using the D38A and D38K mutations of PP2Cα as specific tools in combination with enzymology analysis, our results demonstrated that the M2 metal ion determines the rate-limiting step of substrate hydrolysis, participates in dianion substrate binding and stabilizes the leaving group after P-O bond cleavage. The newly characterized catalytic role of the M2 metal ion in this family not only provides insight into how the binuclear metal centers of the PP2C phosphatases are organized for efficient catalysis but also helps increase our understanding of the function and substrate specificity of PP2C family members.

  18. The catalytic role of the M2 metal ion in PP2

    PubMed Central

    Pan, Chang; Tang, Jun-yi; Xu, Yun-fei; Xiao, Peng; Liu, Hong-da; Wang, Hao-an; Wang, Wen-bo; Meng, Fan-guo; Yu, Xiao; Sun, Jin-peng

    2015-01-01

    PP2C family phosphatases (the type 2C family of protein phosphatases; or metal-dependent phosphatase, PPM) constitute an important class of signaling enzymes that regulate many fundamental life activities. All PP2C family members have a conserved binuclear metal ion active center that is essential for their catalysis. However, the catalytic role of each metal ion during catalysis remains elusive. In this study, we discovered that mutations in the structurally buried D38 residue of PP2Cα (PPM1A) redefined the water-mediated hydrogen network in the active site and selectively disrupted M2 metal ion binding. Using the D38A and D38K mutations of PP2Cα as specific tools in combination with enzymology analysis, our results demonstrated that the M2 metal ion determines the rate-limiting step of substrate hydrolysis, participates in dianion substrate binding and stabilizes the leaving group after P-O bond cleavage. The newly characterized catalytic role of the M2 metal ion in this family not only provides insight into how the binuclear metal centers of the PP2C phosphatases are organized for efficient catalysis but also helps increase our understanding of the function and substrate specificity of PP2C family members. PMID:25708299

  19. Impact of repeated dry-wet cycles on soil CO2 efflux in a beech forest

    NASA Astrophysics Data System (ADS)

    Leitner, Sonja; Saronjic, Nermina; Kobler, Johannes; Holtermann, Christian; Zechmeister-Boltenstern, Sophie; Zimmermann, Michael

    2015-04-01

    Climate change research predicts that both frequency and intensity of weather extremes such as severe droughts and heavy rainfall events will increase in mid Europe over the next decades. Because soil moisture is one of the major factors controlling microbially-driven soil processes, a changed moisture regime will impact soil organic matter (SOM) decomposition and nutrient cycling. This in turn can lead to feedback effects between altered precipitation and changed soil CO2 fluxes which can intensify climate change. Soil microorganisms can go into a state of dormancy or form inactive cysts to protect themselves from osmotic stress during soil drying. However, severe droughts increase microbial mortality which slows down SOM decomposition and decreases soil CO2 efflux. The rewetting of dry soil, on the other hand, causes large CO2 emissions, which is also known as the "Birch effect". Until today it is not clear whether these CO2 peaks outweigh the drought-induced decrease of total CO2 efflux. To investigate the impact of repeated dry-wet cycles on soil CO2 efflux we are conducting a precipitation manipulation experiment in a temperate Austrian beech forest. Roofs exclude rainfall and simulate drought periods, and heavy rainfall events are simulated with a sprinkler system. We apply repeated dry-wet cycles in two intensities: one treatment receives 6 cycles of 1 month drought followed by 75mm irrigation, and a parallel treatment receives 3 cycles of 2 months drought followed by 150mm irrigation. Soil CO2 efflux is constantly monitored with an automated flux chamber system, and environmental parameters are recorded via dataloggers. Our results show that droughts significantly reduce soil CO2 effluxes, and that the reductions depend on the length of the drought periods, with longer droughts leading to stronger reductions of CO2 effluxes. In the first 24 to 48h after rewetting, CO2 emissions strongly increased, and then slowly decreased again. Soil CO2 efflux was

  20. ABB wet flue gas desulfurization

    SciTech Connect

    Niijhawan, P.

    1994-12-31

    The wet limestone process for flue gas desulfurization (FGD) is outlined. The following topics are discussed: wet flue gas desulfurization, wet FGD characteristics, wet scrubbers, ABB wet FGD experience, wet FGD forced oxidation, advanced limestone FGD systems, key design elements, open spray tower design, spray tower vs. packed tower, important performance parameters, SO{sub 2} removal efficiency, influence by L/G, limestone utilization, wet FGD commercial database, particulate removal efficiencies, materials of construction, nozzle layout, spray nozzles, recycle pumps, mist elimination, horizontal flow demister, mist eliminator washing, reagent preparation system, spray tower FGDS power consumption, flue gas reheat options, byproduct conditioning system, and wet limestone system.

  1. Role of the carboxyl terminus on the catalytic activity of protein kinase CK2alpha subunit.

    PubMed

    Tapia, Julio; Jacob, Germaine; Allende, Catherine C; Allende, Jorge E

    2002-11-06

    Protein kinase CK2 (also known as casein kinase 2) has catalytic (alpha, alpha') and regulatory (beta) subunits. The role of carboxyl amino acids in positions from 324 to 328 was studied for Xenopus laevis CK2alpha. Deletions and mutations of these residues were produced in recombinant CK2alpha, which was assayed for kinase activity. Activity dropped 7000-fold upon deletion of amino acids 324-328. The key residues are isoleucine 327 and phenylalanine 324. A three dimensional model of CK2alpha indicates that these hydrophobic residues of helix alphaN may interact with hydrophobic residues in helix alphaE which is linked to the catalytic center.

  2. Thickness dependent wetting properties and surface free energy of HfO2 thin films

    NASA Astrophysics Data System (ADS)

    Zenkin, Sergei; Belosludtsev, Alexandr; Kos, Šimon; Čerstvý, Radomír; Haviar, Stanislav; Netrvalová, Marie

    2016-06-01

    We show here that intrinsic hydrophobicity of HfO2 thin films can be easily tuned by the variation of film thickness. We used the reactive high-power impulse magnetron sputtering for preparation of high-quality HfO2 films with smooth topography and well-controlled thickness. Results show a strong dependence of wetting properties on the thickness of the film in the range of 50-250 nm due to the dominance of the electrostatic Lifshitz-van der Waals component of the surface free energy. We have found the water droplet contact angle ranging from ≈120° for the thickness of 50 nm to ≈100° for the thickness of 2300 nm. At the same time the surface free energy grows from ≈25 mJ/m2 for the thickness of 50 nm to ≈33 mJ/m2 for the thickness of 2300 nm. We propose two explanations for the observed thickness dependence of the wetting properties: influence of the non-dominant texture and/or non-monotonic size dependence of the particle surface energy.

  3. The effect of Ce ion substituted OMS-2 nanostructure in catalytic activity for benzene oxidation

    NASA Astrophysics Data System (ADS)

    Hou, Jingtao; Li, Yuanzhi; Mao, Mingyang; Zhao, Xiujian; Yue, Yuanzheng

    2014-11-01

    The nanostructure of Ce doped OMS-2 plays a very important role in its catalytic property. We demonstrate by density functional theory (DFT) calculations that the unique nanostructure of the Ce ion substituted OMS-2 with Mn vacancy in the framework is beneficial for the improvement of catalytic activity, while the nanostructure of the Ce ion substituted OMS-2 without defects are detrimental to the catalytic activity. We establish a novel and facile strategy of synthesizing these unique Ce ion substituted OMS-2 nanostructure with Mn vacancies in the framework by hydrothermal redox reaction between Ce(NO3)3 and KMnO4 with KMnO4/Ce(NO3)3 at a molar ratio of 3 : 1 at 120 °C. Compared to pure OMS-2, the produced catalyst of Ce ion substituted OMS-2 ultrathin nanorods exhibits an enormous enhancement in the catalytic activity for benzene oxidation, which is evidenced by a significant decrease (ΔT50 = 100 °C, ΔT90 = 129 °C) in the reaction temperature of T50 and T90 (corresponding to the benzene conversion = 50% and 90%), which is considerably more efficient than the expensive supported noble metal catalyst (Pt/Al2O3). We combine both theoretical and experimental evidence to provide a new physical insight into the significant effect due to the defects induced by the Ce ion substitution on the catalytic activity of OMS-2. The formation of unique Ce ion substituted OMS-2 nanostructure with Mn vacancies in the framework leads to a significant enhancement of the lattice oxygen activity, thus tremendously increasing the catalytic activity.The nanostructure of Ce doped OMS-2 plays a very important role in its catalytic property. We demonstrate by density functional theory (DFT) calculations that the unique nanostructure of the Ce ion substituted OMS-2 with Mn vacancy in the framework is beneficial for the improvement of catalytic activity, while the nanostructure of the Ce ion substituted OMS-2 without defects are detrimental to the catalytic activity. We establish a novel

  4. Wet meadows

    Treesearch

    Jonathan W. Long; Karen Pope

    2014-01-01

    Wet meadows help to sustain favorable water flows, biological diversity, and other values; consequently, restoration of degraded wet meadows is an important part of a strategy for promoting socioecological resilience. This chapter focuses on high-elevation wet meadows that are associated with streams; thus restoration of such meadows may be considered a subset of...

  5. 10-23 DNAzyme modified with (2'R)- and (2'S)-2'-deoxy-2'-C-methyluridine in the catalytic core.

    PubMed

    Robaldo, Laura; Montserrat, Javier M; Iribarren, Adolfo M

    2010-08-01

    The catalytic core of a 10-23 DNAzyme was modified using (2'R), (2'S)-2'-deoxy-2'-C-methyluridine and LNA-T. Catalytic activities under pseudo first order conditions were compared at different Mg(2+) concentrations, indicating that certain 2'-C-methyl modified DNAzymes have significant activities. Resistance against MCF-7 cell lysate and endonuclease RQ1 was also measured, showing that the introduction of 2'-C-methyl-2'-deoxynucleosides increased the stability.

  6. Catalytic effect of magnetic nanoparticles over the H2O2 decomposition reaction.

    PubMed

    Andrade, A L; Souza, D M; Pereira, M C; Fabris, J D; Domingues, R Z

    2009-06-01

    This paper compares the rate of decomposition of hydrogen peroxide when controlled nano-sized magnetite powders are used as catalysts. Two different nano-sized powders and a Fe0/Fe3O4 composite have been used. The nanoparticle samples were synthesized by: (i) a chemical reduction-precipitation method and, (ii) by reduction under H2 atmosphere at 250 degrees C, of a hematite sample previously prepared. The composite, Fe0/Fe3O4, was prepared by thermal controlled reduction of nanoparticles of Fe2O3 obtained from hematite under H2 at 300 degrees C. The samples were characterized by Fourier-transform infrared, X-ray diffraction, and Mössbauer spectroscopy at room temperature, and surface area. The catalytic effect was studied in the decomposition reaction of H2O2 by measuring the formation of gaseous O2. The results showed the presence of pure Fe3O4 for nano magnetite samples and Fe0 and Fe3O4 for the composite sample. The average particle sizes of the magnetite, calculated from reflection 311 by using Scherrer equation were about 33 and 10 nm for the samples obtained by hematite reduction and reduction-precipitation, respectively. Kinetic studies of the decomposition of peroxide showed a higher decomposition rate for the hydrogen peroxide reaction when nanoparticles prepared by reduction-precipitation method were used as catalysts. The high catalytic activity associated to nanoparticles is discussed in terms of the high surface area of these samples.

  7. Catalytic hydrolysis of phosphate diesters by lanthanide(III) cryptate (2.2.1) complexes

    SciTech Connect

    Oh, Soon Jin; Song, Hwa Song; Wang, Dongmok

    1996-06-19

    Lanthanide(III) Cryptate (2.2.1) chlorides (Ln(2.2.1)Cl{sub 3}; Ln = La (1a), Ce(1b), and Eu(1c); (2.2.1) = 4,7,13,16,21-pentaoxa-1,10-diazabicyclo[8.8.5]tricosane) are effective for the catalytic hydrolysis of bis(4-nitrophenyl) phophate. Kinetic studies reveal that the europium(III) complex (1c) catalyzes the hydrolysis to produce 6 equiv of 4-nitrophenol with a significant rate (k{sub 1} = 1.5 x 10{sup {minus}4} s{sup {minus}1} at 0.40 mM) at pH 8.5 and 50 {degrees}C. The catalytic activity of the complexes is increased with decreasing the ionic size, i.e. La < Ce < Eu. While the use of hydrogen peroxide further increases the activity of 1b (k{sub 1} = 1.6 x 10{sup {minus}3},at 0.40 mM), the presence of molecular oxygen does not affect the activity at all.

  8. The effect of Ce ion substituted OMS-2 nanostructure in catalytic activity for benzene oxidation.

    PubMed

    Hou, Jingtao; Li, Yuanzhi; Mao, Mingyang; Zhao, Xiujian; Yue, Yuanzheng

    2014-12-21

    The nanostructure of Ce doped OMS-2 plays a very important role in its catalytic property. We demonstrate by density functional theory (DFT) calculations that the unique nanostructure of the Ce ion substituted OMS-2 with Mn vacancy in the framework is beneficial for the improvement of catalytic activity, while the nanostructure of the Ce ion substituted OMS-2 without defects are detrimental to the catalytic activity. We establish a novel and facile strategy of synthesizing these unique Ce ion substituted OMS-2 nanostructure with Mn vacancies in the framework by hydrothermal redox reaction between Ce(NO3)3 and KMnO4 with KMnO4/Ce(NO3)3 at a molar ratio of 3 : 1 at 120 °C. Compared to pure OMS-2, the produced catalyst of Ce ion substituted OMS-2 ultrathin nanorods exhibits an enormous enhancement in the catalytic activity for benzene oxidation, which is evidenced by a significant decrease (ΔT(50) = 100 °C, ΔT(90) = 129 °C) in the reaction temperature of T50 and T90 (corresponding to the benzene conversion = 50% and 90%), which is considerably more efficient than the expensive supported noble metal catalyst (Pt/Al2O3). We combine both theoretical and experimental evidence to provide a new physical insight into the significant effect due to the defects induced by the Ce ion substitution on the catalytic activity of OMS-2. The formation of unique Ce ion substituted OMS-2 nanostructure with Mn vacancies in the framework leads to a significant enhancement of the lattice oxygen activity, thus tremendously increasing the catalytic activity.

  9. Inter-calibration of wet path delay datasets for the computation of the wet tropospheric correction for CryoSat-2 over ocean

    NASA Astrophysics Data System (ADS)

    Fernandes, Joana; Nunes, Alexandra; Lázaro, Clara; Dinardo, Salvatore; Benveniste, Jérôme; Pires, Nelson

    2013-04-01

    The use of CryoSat-2 (CS-2) data for applications beyond the primary objectives of the mission, including studies over oceans, gained importance after the loss of Envisat in April 2012. Since CS-2 does not carry an onboard microwave radiometer (MWR), the wet tropospheric correction (WTC) is a model-based one, provided by the European Centre for Medium-Range Weather Forecasts (ECMWF). Due to its high spatial and temporal variability, the WTC is still one of the major error sources in satellite altimetry, thus driving a need to develop an improved wet path delay correction for CS-2, of particular importance for ocean applications. In the scope of the CryoSat Plus for Oceans (CP4O) project, encouraged by the European Space Agency, a data combination (DComb) algorithm is being developed, based on the objective analysis of all available data sources (e.g. from MWR on board remote sensing (RS) satellites, Global Navigation Satellite Systems (GNSS) and the ECMWF ReAnalysis (ERA) Interim model). The scope of this study is the analysis and inter-calibration of all available datasets for the computation of the wet path delay of altimeter measurements over ocean, in preparation for their use in the DComb algorithm. The following two main data types are analysed: wet path delays derived from water vapour products of scanning microwave radiometers of various sensors (e.g. AMSU-A, SSMI/S, AMSR-E, TMI and WindSat) aboard over ten different remote sensing missions and GNSS-derived path delays from coastal and island stations. Except for TMI, all MWR imaging sensors are on board near-polar sun-synchronous satellites possessing different local times of the ascending node (LTAN), thus allowing an almost uniform data coverage throughout the day. Since CS-2 orbit is not sun-synchronous, the number of MWR images available for the WTC computation (within pre-defined time and space domains centred at each CS-2 measurement) will vary throughout the satellite repeat cycle (369-days); it

  10. Ag-Fe2O3 nanocomposites with enhanced catalytic activity for reduction of 4-nitrophenol

    NASA Astrophysics Data System (ADS)

    Liu, Shiben; Chen, Yingjie; Dong, Lifeng

    2016-07-01

    Hybrid nanostructures can be multifunctional and even possess enhanced properties. Ag-Fe2O3 nanocomposites and Ag nanoparticles (NPs) were fabricated and applied to catalyze the reduction of 4-nitrophenol. Compared with Ag NPs, Ag-Fe2O3 nanocomposites demonstrated enhanced catalytic activities. Furthermore, due to their magnetic properties, Ag-Fe2O3 nanocomposites could be easily separated from the reaction mixture and recycled through an external magnetic field. These findings will help us design hybrid nanostructures with catalytic activity and explore other potential applications of magnetic nanocomposites.

  11. Mechanistic insights into hydride transfer for catalytic hydrogenation of CO(2) with cobalt complexes.

    PubMed

    Kumar, N; Camaioni, D M; Dupuis, M; Raugei, S; Appel, A M

    2014-08-21

    The catalytic hydrogenation of CO2 to formate by Co(dmpe)2H can proceed via direct hydride transfer or via CO2 coordination to Co followed by reductive elimination of formate. The different nature of the rate-determining step in the two mechanisms may provide new insights into designing catalysts with improved performance.

  12. Inverse algorithms for 2D shallow water equations in presence of wet dry fronts: Application to flood plain dynamics

    NASA Astrophysics Data System (ADS)

    Monnier, J.; Couderc, F.; Dartus, D.; Larnier, K.; Madec, R.; Vila, J.-P.

    2016-11-01

    The 2D shallow water equations adequately model some geophysical flows with wet-dry fronts (e.g. flood plain or tidal flows); nevertheless deriving accurate, robust and conservative numerical schemes for dynamic wet-dry fronts over complex topographies remains a challenge. Furthermore for these flows, data are generally complex, multi-scale and uncertain. Robust variational inverse algorithms, providing sensitivity maps and data assimilation processes may contribute to breakthrough shallow wet-dry front dynamics modelling. The present study aims at deriving an accurate, positive and stable finite volume scheme in presence of dynamic wet-dry fronts, and some corresponding inverse computational algorithms (variational approach). The schemes and algorithms are assessed on classical and original benchmarks plus a real flood plain test case (Lèze river, France). Original sensitivity maps with respect to the (friction, topography) pair are performed and discussed. The identification of inflow discharges (time series) or friction coefficients (spatially distributed parameters) demonstrate the algorithms efficiency.

  13. Copper Wetting of x-Al(2)O(3)(0001): Theory and Experiment

    SciTech Connect

    Bogicevic, A.; Jennison, D.R.; Kelber, J.A.; Niu, Chengyu; Shepherd, K.

    1999-08-10

    XPS studies have been carried out on sputter deposited copper on a substantially hydroxylated {alpha}-Al{sub 2}O{sub 3}(0001) (sapphire) surface under ultra-high vacuum (UHV) conditions. XPS-derived Cu uptake curves show a sharp change in slope at a coverage of 0.35 monolayer (on a Cu/O atomic basis), indicative of initial layer-by-layer growth. CU(LMM) lineshape data indicate that, prior to the first break in the curve, Cu is oxidized to Cu(I). At higher coverages, metallic CU(0) is. observed. These data agree with first principles theoretical calculations, indicating that the presence of ad-hydroxyl groups greatly enhances the binding of Cu to bulk sapphire surfaces, stabilizing Cu(I) adatoms over two-dimensional metallic islands. In the absence of hydroxylation, calculations indicate significantly weaker Cu binding to the bulk sapphire substrate and non-wetting. Calculations also predict that at Cu coverages above 1/3 monolayer (ML), Cu-Cu interactions predominate, leading to Cu(0) formation. These results are in excellent agreement with experiment. The ability of surface hydroxyl groups to enhance binding to alumina substrates suggests a reason for contradictory experimental results reported in the literature for Cu wetting of alumina.

  14. Advanced wet flue gas desulfurization and denitrification process, Miami Fort station. Volume 2: Final report

    SciTech Connect

    Not Available

    1991-11-01

    Two hundred and sixty-one coal-fired electric utility generating units in the United States are affected by Phase 1 the 1990 Clean Air Act revisions. The total MW of generating capacity affected is 87,261. Dravo Lime projects that 24,400 MW will be retrofitted with wet FGD for Phase 1; in Phase 2, another 6,600 MW will be retrofitted. Forty-one of the affected units, with a total capacity of 14,343 MW, are located Ohio. Figure A1 shows the location and approximate size of these units. Table Al lists the units and itemizes the allowable emissions. It is likely that several of the larger units in Ohio and elsewhere will be retrofitted by 1995--1997 with magnesium-enhanced lime based wet FGD, and the improvements found in the testing program could be included as part of these installations. Smaller diameter absorbers built for higher flue gas velocities would be easier to fabricate off-site and to ship by barge on the Ohio River to the plant site, as was done for the absorbers installed at the Zimmer station. Much smaller thickeners would be easier to fit onto cramped sites in retrofits.

  15. Effect of the Addition of CeO2 to Iron Phosphate Glass for Catalytic Applications.

    PubMed

    Chung, Jae-Yeop; Kim, Jong-Hwan; Choi, Su-Yeon; Ryu, Bong-Ki

    2015-10-01

    We investigated the effect of CeO2 content on the catalytic behavior and chemical properties of the (100 - x)(80P2O5-20Fe2O3)-xCeO2 (x = 0, 4, 8, 12, 16, 20 and 24 wt%) glass system. Using thermogravimetric analysis, we confirmed that the catalytic activity increased until a CeO2 content of 16 wt%, beyond which, it decreased. The reasons for the change in the catalytic properties of the glass samples were determined using Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and density analyses. It was confirmed using the FT-IR and XPS-01s spectra that CeO2 acts as a network modifier in iron phosphate glass. When the CeO2 content is above 16 wt%, the number of non-bridging oxygen atoms decreases with increasing CeO2 content. For these reasons, the catalytic properties decrease when the CeO2 content is more than 16 wt%. From the dissolution rate measurements, it can be observed that cerium-iron phosphate has a high water resistance. Also, as we expected, it can be confirmed that the chemical durability is improved with increasing CeO2 content.

  16. All the catalytic active sites of MoS2 for hydrogen evolution

    SciTech Connect

    Li, Guoqing; Zhang, Du; Qiao, Qiao; Yu, Yifei; Peterson, David; Zafar, Abdullah; Kumar, Raj; Curtarolo, Stefano; Hunte, Frank; Shannon, Steve; Zhu, Yimei; Yang, Weitao; Cao, Linyou

    2016-11-29

    MoS2 presents a promising low-cost catalyst for the hydrogen evolution reaction (HER), but the understanding about its active sites has remained limited. Here we present an unambiguous study of the catalytic activities of all possible reaction sites of MoS2, including edge sites, sulfur vacancies, and grain boundaries. We demonstrate that, in addition to the well-known catalytically active edge sites, sulfur vacancies provide another major active site for the HER, while the catalytic activity of grain boundaries is much weaker. Here, the intrinsic turnover frequencies (Tafel slopes) of the edge sites, sulfur vacancies, and grain boundaries are estimated to be 7.5 s–1 (65–75 mV/dec), 3.2 s–1 (65–85 mV/dec), and 0.1 s–1 (120–160 mV/dec), respectively. We also demonstrate that the catalytic activity of sulfur vacancies strongly depends on the density of the vacancies and the local crystalline structure in proximity to the vacancies. Unlike edge sites, whose catalytic activity linearly depends on the length, sulfur vacancies show optimal catalytic activities when the vacancy density is in the range of 7–10%, and the number of sulfur vacancies in high crystalline quality MoS2 is higher than that in low crystalline quality MoS2, which may be related with the proximity of different local crystalline structures to the vacancies.

  17. Exfoliation of graphene sheets via high energy wet milling of graphite in 2-ethylhexanol and kerosene.

    PubMed

    Al-Sherbini, Al-Sayed; Bakr, Mona; Ghoneim, Iman; Saad, Mohamed

    2017-05-01

    Graphene sheets have been exfoliated from bulk graphite using high energy wet milling in two different solvents that were 2-ethylhexanol and kerosene. The milling process was performed for 60 h using a planetary ball mill. Morphological characteristics were investigated using scanning electron microscope (SEM) and transmission electron microscope (TEM). On the other hand, the structural characterization was performed using X-ray diffraction technique (XRD) and Raman spectrometry. The exfoliated graphene sheets have represented good morphological and structural characteristics with a valuable amount of defects and a good graphitic structure. The graphene sheets exfoliated in the presence of 2-ethylhexanol have represented many layers, large crystal size and low level of defects, while the graphene sheets exfoliated in the presence of kerosene have represented fewer number of layers, smaller crystal size and higher level of defects.

  18. Nanostructured, mesoporous Au/TiO(2) model catalysts - structure, stability and catalytic properties.

    PubMed

    Roos, Matthias; Böcking, Dominique; Gyimah, Kwabena Offeh; Kucerova, Gabriela; Bansmann, Joachim; Biskupek, Johannes; Kaiser, Ute; Hüsing, Nicola; Behm, R Jürgen

    2011-01-01

    Aiming at model systems with close-to-realistic transport properties, we have prepared and studied planar Au/TiO(2) thin-film model catalysts consisting of a thin mesoporous TiO(2) film of 200-400 nm thickness with Au nanoparticles, with a mean particle size of ~2 nm diameter, homogeneously distributed therein. The systems were prepared by spin-coating of a mesoporous TiO(2) film from solutions of ethanolic titanium tetraisopropoxide and Pluronic P123 on planar Si(100) substrates, calcination at 350 °C and subsequent Au loading by a deposition-precipitation procedure, followed by a final calcination step for catalyst activation. The structural and chemical properties of these model systems were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N(2) adsorption, inductively coupled plasma ionization spectroscopy (ICP-OES) and X-ray photoelectron spectroscopy (XPS). The catalytic properties were evaluated through the oxidation of CO as a test reaction, and reactivities were measured directly above the film with a scanning mass spectrometer. We can demonstrate that the thin-film model catalysts closely resemble dispersed Au/TiO(2) supported catalysts in their characteristic structural and catalytic properties, and hence can be considered as suitable for catalytic model studies. The linear increase of the catalytic activity with film thickness indicates that transport limitations inside the Au/TiO(2) film catalyst are negligible, i.e., below the detection limit.

  19. Dynamics of catalytic resolution of 2-lithio-N-Boc-piperidine by ligand exchange.

    PubMed

    Beng, Timothy K; Tyree, William S; Parker, Trent; Su, Chicheung; Williard, Paul G; Gawley, Robert E

    2012-10-10

    The dynamics of the racemization and catalytic and stoichiometric dynamic resolution of 2-lithio-N-Boc-piperidine (7) have been investigated. The kinetic order in tetramethylethylenediamine (TMEDA) for both racemization and resolution of the title compound and the kinetic orders in two resolving ligands have been determined. The catalytic dynamic resolution is second order in TMEDA and 0.5 and 0.265 order in chiral ligands 8 and 10, respectively. The X-ray crystal structure of ligand 10 shows it to be an octamer. Dynamic NMR studies of the resolution process were carried out. Some of the requirements for a successful catalytic dynamic resolution by ligand exchange have been identified.

  20. Catalytic decomposition of hydrogen peroxide and 2-chlorophenol with iron oxides.

    PubMed

    Huang, H H; Lu, M C; Chen, J N

    2001-06-01

    The aim of this study was to examine the catalyzed decomposition of hydrogen peroxide and 2-chlorophenol (2-CP) in the presence of iron oxides. Granular ferrihydrite, goethite, and hematite were selected as catalysts in this study. 2-CP was used as the model compound because it is a typical toxic compound and has not been investigated in the catalytic decomposition by iron oxides. The catalytic activity for hydrogen peroxide decomposition followed the sequence: granular ferrihydrite > goethite > hematite. However, hematite exhibited the highest activity in catalyzing 2-CP oxidation. The oxidation efficiency of 2-CP corresponded with the inverse sequence of specific area and pHpzc of the iron oxides. The catalytic activity of granular ferrihydrite was affected significantly by the mixing speed and particle size for its large value of Thiele modulus (phi) and Damkohler number (Da). The strong diffusion resistance for granular ferrihydrite was attributed either to its microporous structure or to the formation of oxygen in the pores of the iron oxide leading to the unexpected catalytic activity of granular ferrihydrite to hydrogen peroxide and 2-CP.

  1. Wet chemical techniques for passivation of YBa2Cu3O7(7-x)

    NASA Astrophysics Data System (ADS)

    Vasquez, R. P.; Foote, M. C.; Hunt, B. D.

    1989-10-01

    Wet chemical techniques are described for treatment of YBa2Cu3O(7-x) surfaces, resulting in the formation of native compounds with little or no reactivity to water. Promising native compounds include CuI, BaSO4, CuS, Cu2S, and the oxalates, all of which are either insoluble or have very low solubility in water. Treatment with dilute HI results in the formation of a native iodide film which is 80-90 percent CuI with small amounts of YI3 and BaI2. Treatment with dilute H2SO4 results in the formation of a film which is 95 percent BaSO4 and 5 percent Y2(SO4)3. Cu2S is formed on the surface with a dilute Na2S solution. An oxalate film with equal amounts of Y2(C2O4)3 and BaC2O4 results from treatment with dilute oxalic acid. X-ray photoelectron spectra show no significant changes when the sulfide, sulfate, or oxalate films are dipped in water, while the iodide film shows evidence of Cu(OH)2 formation.

  2. Wet chemical techniques for passivation of YBa2Cu3O7(7-x)

    NASA Technical Reports Server (NTRS)

    Vasquez, R. P.; Foote, M. C.; Hunt, B. D.

    1989-01-01

    Wet chemical techniques are described for treatment of YBa2Cu3O(7-x) surfaces, resulting in the formation of native compounds with little or no reactivity to water. Promising native compounds include CuI, BaSO4, CuS, Cu2S, and the oxalates, all of which are either insoluble or have very low solubility in water. Treatment with dilute HI results in the formation of a native iodide film which is 80-90 percent CuI with small amounts of YI3 and BaI2. Treatment with dilute H2SO4 results in the formation of a film which is 95 percent BaSO4 and 5 percent Y2(SO4)3. Cu2S is formed on the surface with a dilute Na2S solution. An oxalate film with equal amounts of Y2(C2O4)3 and BaC2O4 results from treatment with dilute oxalic acid. X-ray photoelectron spectra show no significant changes when the sulfide, sulfate, or oxalate films are dipped in water, while the iodide film shows evidence of Cu(OH)2 formation.

  3. Wet chemical techniques for passivation of YBa2Cu3O7(7-x)

    NASA Technical Reports Server (NTRS)

    Vasquez, R. P.; Foote, M. C.; Hunt, B. D.

    1989-01-01

    Wet chemical techniques are described for treatment of YBa2Cu3O(7-x) surfaces, resulting in the formation of native compounds with little or no reactivity to water. Promising native compounds include CuI, BaSO4, CuS, Cu2S, and the oxalates, all of which are either insoluble or have very low solubility in water. Treatment with dilute HI results in the formation of a native iodide film which is 80-90 percent CuI with small amounts of YI3 and BaI2. Treatment with dilute H2SO4 results in the formation of a film which is 95 percent BaSO4 and 5 percent Y2(SO4)3. Cu2S is formed on the surface with a dilute Na2S solution. An oxalate film with equal amounts of Y2(C2O4)3 and BaC2O4 results from treatment with dilute oxalic acid. X-ray photoelectron spectra show no significant changes when the sulfide, sulfate, or oxalate films are dipped in water, while the iodide film shows evidence of Cu(OH)2 formation.

  4. Enantioselective phase-transfer catalytic α-alkylation of 2-methylbenzyl tert-butyl malonates.

    PubMed

    Ha, Min Woo; Hong, Suckchang; Park, Cheonhyoung; Park, Yohan; Lee, Jihye; Kim, Mi-hyun; Lee, Jihoon; Park, Hyeung-geun

    2013-06-28

    A new asymmetric synthetic method to prepare α,α-dialkylmalonates for the construction of a quaternary carbon center via phase-transfer catalytic (PTC) alkylation has been developed. Enantioselective α-alkylation of 2-methylbenzyl tert-butyl α-methylmalonates under phase-transfer catalytic conditions in the presence of (S,S)-3,4,5-trifluorophenyl-NAS bromide () afforded the corresponding α,α-dialkylmalonates in high chemical (up to 99%) and optical yields (up to 91% ee), which were selectively hydrolyzed to malonic monoacids under alkali basic conditions for conversion to versatile chiral intermediates.

  5. Core-shell nanospheres Pt@SiO2 for catalytic hydrogen production

    NASA Astrophysics Data System (ADS)

    Hu, Yujuan; Wang, Yuqing; Lu, Zhang-Hui; Chen, Xiangshu; Xiong, Lihua

    2015-06-01

    Ultrafine platinum nanoparticles (NPs) embedded in silica nanospheres (Pt@SiO2) have been synthesized in a NP-5/cyclohexane reversed-micelle system followed by NaBH4 reduction. The as-synthesized core-shell nanocatalysts Pt@SiO2 were characterized by scanning electron microscopy, transmission electron microscopes, X-ray powder diffraction analysis, energy dispersive X-ray spectrometer and nitrogen adsorption-desorption investigations. Interestingly, the as-synthesized core-shell nanocatalysts Pt@SiO2 showed an excellent catalytic performance in hydrogen generation from the hydrolysis of ammonia borane (BH3NH3, AB) at room temperature. Especially, the catalytic performance of the Pt@SiO2 remained almost unchanged after the five recycles and even after the heat treatment (673 K), because the silica shells inhibit aggregation or deformation of the metal cores. Besides, the kinetic studies showed that the catalytic hydrolysis of AB was first order with respect to the catalyst concentration and zero order with respect to the substrate concentration, respectively. The excellent catalytic activity and stability of Pt@SiO2 can make it have a bright future in the practical application.

  6. Tunable Molecular MoS2 Edge-Site Mimics for Catalytic Hydrogen Production.

    PubMed

    Garrett, Benjamin R; Polen, Shane M; Click, Kevin A; He, Mingfu; Huang, Zhongjie; Hadad, Christopher M; Wu, Yiying

    2016-04-18

    Molybdenum sulfides represent state-of-the-art, non-platinum electrocatalysts for the hydrogen evolution reaction (HER). According to the Sabatier principle, the hydrogen binding strength to the edge active sites should be neither too strong nor too weak. Therefore, it is of interest to develop a molecular motif that mimics the catalytic sites structurally and possesses tunable electronic properties that influence the hydrogen binding strength. Furthermore, molecular mimics will be important for providing mechanistic insight toward the HER with molybdenum sulfide catalysts. In this work, a modular method to tune the catalytic properties of the S-S bond in MoO(S2)2L2 complexes is described. We studied the homogeneous electrocatalytic hydrogen production performance metrics of three catalysts with different bipyridine substitutions. By varying the electron-donating abilities, we present the first demonstration of using the ligand to tune the catalytic properties of the S-S bond in molecular MoS2 edge-site mimics. This work can shed light on the relationship between the structure and electrocatalytic activity of molecular MoS2 catalysts and thus is of broad importance from catalytic hydrogen production to biological enzyme functions.

  7. Preparation and catalytic behavior of CeO2 nanoparticles on Al2O3 crystal

    NASA Astrophysics Data System (ADS)

    Hattori, Takashi; Kobayashi, Katsutoshi; Ozawa, Masakuni

    2017-01-01

    In this work, we examined the preparation, morphology, and catalytic behavior of CeO2 nanoparticles (NPs) on Al2O3(0001) crystal substrates. A CeO2 NP layer was prepared by the dipping method using a CeO2 nanocrystal colloid solution. Even after heat treatment at 1000 °C, the CeO2 NP layer maintained the granular morphology of CeO2 with a grain diameter of less than 40 nm. CeO2 NPs on an Al2O3 crystal showed higher oxidation activity for gaseous hydrogen at moderate temperatures and enhanced oxygen release properties of CeO2, compared with CeO2 powder. This was due to the highly dispersed CeO2 NPs and the interaction between CeO2 NPs and Al2O3; this clarified the importance of the Al2O3 support for the CeO2 catalyst.

  8. Forsterite Carbonation in Wet-scCO2: Dependence on Adsorbed Water Concentration

    NASA Astrophysics Data System (ADS)

    Loring, J.; Benezeth, P.; Qafoku, O.; Thompson, C.; Schaef, T.; Bonneville, A.; McGrail, P.; Felmy, A.; Rosso, K.

    2013-12-01

    Capturing and storing CO2 in basaltic formations is one of the most promising options for mitigating atmospheric CO2 emissions resulting from the burning of fossil fuels. These geologic reservoirs have high reactive potential for CO2-mineral trapping due to an abundance of divalent-cation containing silicates, such as forsterite (Mg2SiO4). Recent studies have shown that carbonation of these silicates under wet scCO2 conditions, e. g. encountered near a CO2 injection well, proceeds along a different pathway and is more effective than in CO2-saturated aqueous fluids. The presence of an adsorbed water film on the forsterite surface seems to be key to reactivity towards carbonation. In this study, we employed in situ high pressure IR spectroscopy to investigate the dependence of adsorbed water film thickness on forsterite carbonation chemistry. Post reaction ex situ SEM, TEM, TGA, XRD, and NMR measurements will also be discussed. Several IR titrations were performed of forsterite with water at 50 °C and 90 bar scCO2. Aliquots of water were titrated at 4-hour reaction-time increments. Once a desired total water concentration was reached, data were collected for about another 30 hours. One titration involved 10 additions, which corresponds to 6.8 monolayers of adsorbed water. Clearly, a carbonate was precipitating, and its spectral signature matched magnesite. Another titration involved 8 aliquots, or up to 4.4 monolayers of water. The integrated absorbance under the CO stretching bands of carbonate as a function of time after reaching 4.4 monolayers showed an increase and then a plateau. We are currently unsure of the identity of the carbonate that precipitated, but it could be an amorphous anhydrous phase or magnesite crystals with dimensions of only several nanometers. A third titration only involved 3 additions, or up to 1.6 monolayers of water. The integrated absorbance under the CO stretching bands of carbonate as a function of time after reaching 1.6 monolayers

  9. Catalytic effects of functionalized carbon nanotubes on dehydrochlorination of 1,1,2,2-tetrachloroethane.

    PubMed

    Chen, Weifeng; Zhu, Dongqiang; Zheng, Shourong; Chen, Wei

    2014-04-01

    The environmental implications of carbon nanomaterials have received much attention. Nonetheless, little is known about how carbon nanomaterials might affect the abiotic transformation of organic contaminants in aquatic environments. In this study, we observed that three functionalized multiwalled carbon nanotubes (MWCNTs)-including a hydroxylated MWCNT (OH-MWCNT), a carboxylated MWCNT (COOH-MWCNT), and an aminated MWCNT (NH2-MWCNT)-all had strong catalytic effects on the dehydrochlorination of 1,1,2,2-tetrachloroethane (TeCA) at three different pH (7, 8, and 9); notably, the most significant effects (up to 130% increase in reaction rate) were observed at pH 7, at which reaction kinetics was very slow in the absence of MWCNT. The primary mechanism was that the -NH2 group and the deprotonated -COOH and -OH groups serve as bases to catalyze the reaction. Modeling results indicate that at any given pH the transformation kinetic constants of MWCNT-adsorbed TeCA were up to 2 orders of magnitude greater than the respective kinetic constant of dissolved TeCA. The overall catalytic effects of the MWCNTs depended both on the basicity of the surface functionalities of MWCNT and on the adsorption affinities of MWCNT for TeCA. Interestingly, Suwannee River humic acid-selected as a model dissolved organic matter-had negligible effects on the dehydrochlorination kinetics, even though it is rich in surface O-functionalities. An important environmental implication is that carbon nanotubes released into the environment might significantly affect the fate of chlorinated solvents.

  10. Structure of the catalytic domain of glucuronoyl esterase Cip2 from Hypocrea jecorina

    USDA-ARS?s Scientific Manuscript database

    The structure of the catalytic domain of glucuronoyl esterase Cip2 from the fungus Hypocrea jecorina was determined at a resolution of 1.9 Angstroms. This is the first structure of the newly established carbohydrate esterase family 15. The structure has revealed the residues Ser278–His411–Glu301 pre...

  11. Fundamentals and Catalytic Applications of CeO2-Based Materials.

    PubMed

    Montini, Tiziano; Melchionna, Michele; Monai, Matteo; Fornasiero, Paolo

    2016-05-25

    Cerium dioxide (CeO2, ceria) is becoming an ubiquitous constituent in catalytic systems for a variety of applications. 2016 sees the 40(th) anniversary since ceria was first employed by Ford Motor Company as an oxygen storage component in car converters, to become in the years since its inception an irreplaceable component in three-way catalysts (TWCs). Apart from this well-established use, ceria is looming as a catalyst component for a wide range of catalytic applications. For some of these, such as fuel cells, CeO2-based materials have almost reached the market stage, while for some other catalytic reactions, such as reforming processes, photocatalysis, water-gas shift reaction, thermochemical water splitting, and organic reactions, ceria is emerging as a unique material, holding great promise for future market breakthroughs. While much knowledge about the fundamental characteristics of CeO2-based materials has already been acquired, new characterization techniques and powerful theoretical methods are deepening our understanding of these materials, helping us to predict their behavior and application potential. This review has a wide view on all those aspects related to ceria which promise to produce an important impact on our life, encompassing fundamental knowledge of CeO2 and its properties, characterization toolbox, emerging features, theoretical studies, and all the catalytic applications, organized by their degree of establishment on the market.

  12. Modulation of the Cs2CO3-promoted catalytic amination by a crown ether.

    PubMed

    Torisawa, Y; Nishi, T; Minamikawa, J

    2000-11-06

    The catalytic addition of 18-Crown-6 in some Cs2CO3-promoted amination of triflates and bromides was beneficial to improve sluggish reaction with suppression of the unwanted side products. The protocol was useful for the preparation of chlorinated aryl piperazines from phenol derivatives.

  13. Modelling ignition characteristics of rich H2/O2 mixture in a monolithic catalytic reactor

    NASA Technical Reports Server (NTRS)

    Tien, Ta-Ching; T'Ien, James S.

    1988-01-01

    Ignition of rich hydrogen-oxygen mixture in a monolithic catalytic reactor is studied using a transient combustion model. The model assumes a quasi-steady gas phase and a thermally-thin substrate. The ignition time lag is due to the thermal inertia of the substrate. One-step global chemical reaction is assumed both on the surface and in the gas phase. An effectiveness factor is introduced to account for the transition from a kinetically-limited catalytic surface reaction to a diffusion-limit one during ignition. Results presented include a catalytic ignition boundary, ignition delay time and the transient response in the catalytic bed.

  14. Catalytic reaction of 3-phenyl-2-propyn-1-ol with alcohols

    SciTech Connect

    Grigoryan, S.G.; Avetisyan, K.G.; Matnishyan, A.A.

    1987-01-10

    The cyclic ketal 2,5-dimethyl-2,5-bis(3-phenyl-2-propynyloxy)-1,4-dioxane was obtained by the reaction of 3-phenyl-2-propyn-1=ol with propargyl alcohol in the presence of the HgO-BF/sub 3/ O(C/sub 2/H/sub 5/)/sub 2/ catalytic system. The transformation of 3-phenyl-2-propyn-1-ol and its ethers in methanol and ethanol by the action of the above-mentioned catalytic system leads to 1-phenyl-3-alkoxy-1-propanone, 1-phenyl-1,1,3-trialkoxypropane, and 1-phenyl-2-propen-1-one. The intermediate organomercury compound, which is the product from regioselective addition of mercuric oxide and the saturated alcohol at the triple bond, was isolated. Its protodemercuration led to the above-mentioned linear products. The formation of the cyclic ketal is presumably due to the preferred formation of mercury bis-hydroxypropargylide.

  15. Wet chemical passivation of YBa2Cu3O(7-x)

    NASA Technical Reports Server (NTRS)

    Vasquez, R. P.; Hunt, B. D.; Foote, M. C.

    1990-01-01

    Wet chemical techniques are described for treatment of YBa2Cu3O(7-x) surfaces, which result in the formation of native compounds known to have little or no reactivity to water. Suitable native compounds include CuI, BaSO4, CuS, Cu2S, YF3, and the oxalates. Formation of surface layers in which these nonreactive native compounds are major constituents is verified with X-ray photoelectron spectroscopy (XPS) measurements on YBa2Cu3O(7-x) films treated with dilute solutions of HI, H2SO4, Na2S, HF, or H2C2O4. No significant changes are observed in the XPS spectra when the sulfide, sulfate, or oxalate films are dipped in water, while the iodide and fluoride films show evidence of reaction with water. X-ray diffraction measurements show that the superconducting phase is absent in the sulfide film, but is unaffected by the oxalate and sulfate treatments.

  16. WetSpa model application in the Distributed Model Intercomparison Project (DMIP2)

    NASA Astrophysics Data System (ADS)

    Safari, Alireza; De Smedt, F.; Moreda, Fekadu

    2012-02-01

    SummaryThis paper describes the application of a spatially distributed hydrologic model (WetSpa) Water and Energy Transfer between Soil, Plants and Atmosphere, for the second phase of the Distributed Model Intercomparison Project (DMIP2) study. The model implementation is based on 30-m spatial resolution and 1 h time-step for all basins and interior watersheds involved in the DMIP study. Rainfall inputs are derived from Next Generation Radar (NEXRAD). The distributed model parameters are based on an extensive database of watershed characteristics available for the region, including digital maps of topography, soil type, and landuse. The model is calibrated and validated on part of the river flow records for each basin and applied to the smaller interior watersheds not used in calibration to assess the model performance in ungaged basins. The statistics improve significantly with calibration of the global model parameters but even for uncalibrated simulations, the WetSpa model reproduces flow rates of acceptable accuracy for most cases. To evaluate the model performance during calibration and validation periods, an Aggregated Measure ( AM) is introduced that measures different aspects of the simulated hydrograph such as shape, size and volume. The statistics for the five calibration basins show that the model produces very good to excellent results for the calibration period. With the exception of Blue River basin, the overall model performance for the validation period remains good to very good, indicating that the model is able to simulate the relevant hydrologic processes in the basins accurately. The performance of the uncalibrated model for the subcatchments is more variable, but the hourly flow rates generally reproduced with reasonable accuracy indicating an encouraging performance of the model.

  17. Catalytic characterization of human microsomal glutathione S-transferase 2: identification of rate-limiting steps.

    PubMed

    Ahmad, Shabbir; Niegowski, Damian; Wetterholm, Anders; Haeggström, Jesper Z; Morgenstern, Ralf; Rinaldo-Matthis, Agnes

    2013-03-12

    Microsomal glutathione S-transferase 2 (MGST2) is a 17 kDa trimeric integral membrane protein homologous to leukotriene C4 synthase (LTC4S). MGST2 has been suggested to catalyze the biosynthesis of the pro-inflammatory mediator leukotriene C4 (LTC4) in cells devoid of LTC4S. A detailed biochemical study of MGST2 is critical for the understanding of its cellular function and potential role as an LTC4-producing enzyme. Here we have characterized the substrate specificity and catalytic properties of purified MGST2 by steady-state and pre-steady-state kinetic experiments. In comparison with LTC4S, which has a catalytic efficiency of 8.7 × 10(5) M(-1) s(-1), MGST2, with a catalytic efficiency of 1.8 × 10(4) M(-1) s(-1), is considerably less efficient in producing LTC4. However, the two enzymes display a similar KM(LTA4) of 30-40 μM. While LTC4S has one activated glutathione (GSH) (forming a thiolate) per enzyme monomer, the MGST2 trimer seems to display only third-of-the-sites reactivity for thiolate activation, which in part would explain its lower catalytic efficiency. Furthermore, MGST2 displays GSH-dependent peroxidase activity of ∼0.2 μmol min(-1) mg(-1) toward several lipid hydroperoxides. MGST2, but not LTC4S, is efficient in catalyzing conjugation of the electrophilic substrate 1-chloro-2,4-dinitrobenzene (CDNB) and the lipid peroxidation product 4-hydroxy-2-nonenal with GSH. Using stopped-flow pre-steady-state kinetics, we have characterized the full catalytic reaction of MGST2 with CDNB and GSH as substrates, showing an initial rapid equilibrium binding of GSH followed by thiolate formation. Burst kinetics for the CDNB-GSH conjugation step was observed only at low GSH concentrations (thiolate anion formation becoming rate-limiting under these conditions). Product release is rapid and does not limit the overall reaction. Therefore, in general, the chemical conjugation step is rate-limiting for MGST2 at physiological GSH concentrations. MGST2 and LTC4S

  18. Anacardic Acid Inhibits the Catalytic Activity of Matrix Metalloproteinase-2 and Matrix Metalloproteinase-9

    PubMed Central

    Omanakuttan, Athira; Nambiar, Jyotsna; Harris, Rodney M.; Bose, Chinchu; Pandurangan, Nanjan; Varghese, Rebu K.; Kumar, Geetha B.; Tainer, John A.; Banerji, Asoke; Perry, J. Jefferson P.

    2012-01-01

    Cashew nut shell liquid (CNSL) has been used in traditional medicine for the treatment of a wide variety of pathophysiological conditions. To further define the mechanism of CNSL action, we investigated the effect of cashew nut shell extract (CNSE) on two matrix metalloproteinases, MMP-2/gelatinase A and MMP-9/gelatinase B, which are known to have critical roles in several disease states. We observed that the major constituent of CNSE, anacardic acid, markedly inhibited the gelatinase activity of 3T3-L1 cells. Our gelatin zymography studies on these two secreted gelatinases, present in the conditioned media from 3T3-L1 cells, established that anacardic acid directly inhibited the catalytic activities of both MMP-2 and MMP-9. Our docking studies suggested that anacardic acid binds into the MMP-2/9 active site, with the carboxylate group of anacardic acid chelating the catalytic zinc ion and forming a hydrogen bond to a key catalytic glutamate side chain and the C15 aliphatic group being accommodated within the relatively large S1′ pocket of these gelatinases. In agreement with the docking results, our fluorescence-based studies on the recombinant MMP-2 catalytic core domain demonstrated that anacardic acid directly inhibits substrate peptide cleavage in a dose-dependent manner, with an IC50 of 11.11 μM. In addition, our gelatinase zymography and fluorescence data confirmed that the cardol-cardanol mixture, salicylic acid, and aspirin, all of which lack key functional groups present in anacardic acid, are much weaker MMP-2/MMP-9 inhibitors. Our results provide the first evidence for inhibition of gelatinase catalytic activity by anacardic acid, providing a novel template for drug discovery and a molecular mechanism potentially involved in CNSL therapeutic action. PMID:22745359

  19. Wetting and freezing of hexadecane on an aqueous surfactant solution: triple point in a 2-D film.

    PubMed

    Matsubara, H; Ohtomi, E; Aratono, M; Bain, Colin D

    2008-09-18

    Wetting of water by hexadecane has been investigated by ellipsometry as a function of the concentration of the cationic surfactant dodecyltrimethylammonium bromide (DTAB) in the aqueous phase and temperature. Three phases are identified: a 2-D gas of hexadecane molecules and DTAB molecules, a 2-D liquid comprising a mixed monolayer of hexadecane and DTAB, and a 2-D 'solid' phase. Evidence is presented to support the hypothesis that the liquid-solid phase transition is actually a wetting transition in which a surface-frozen layer of pure hexadecane wets the liquid-like mixed monolayer of hexadecane and DTAB. The triple point, at which the three phases coexist, is located at a temperature of 17.3 degrees C and DTAB concentration of 0.75 mmol kg (-1). The slopes of the three phase boundaries are analyzed thermodynamically.

  20. The kinetics of catalytic incineration of C2H5SH and (CH3)2S2 over a Pt/Al2O3 catalyst.

    PubMed

    Chu, H; Lee, W T; Chiou, Y Y; Tseng, T K

    2001-05-01

    Catalytic incineration is one of the cost-effective technologies to solve the troublesome VOCs. However, some sulfur containing VOCs, such as ethyl mercaptan and dimethyl disulfide, may deactivate the Pt catalyst that is commonly used in the catalytic incineration process. The catalytic incineration of these compounds over a Pt/Al2O3 catalyst was carried out in a bench scale catalytic incinerator. Three kinetic models, such as power-rate law, Mars and Van Krevelen model, and Langmuir-Hinshelwood model were used to analyze the results. A differential reactor design was used for best fit of kinetic models in this study. The results show that the Langmuir-Hinshelwood model is feasible to describe the catalytic incineration of both C2H5SH and (CH3)2S2. This suggests that the chemical adsorption of O2 molecule is important in the process of catalytic incineration of C2H5SH and (CH3)2S2.

  1. Core formation, wet early mantle, and H2O degassing on early Mars

    NASA Technical Reports Server (NTRS)

    Kuramoto, K.; Matsui, T.

    1993-01-01

    Geophysical and geochemical observations strongly suggest a 'hot origin of Mars,' i.e., the early formation of both the core and the crust-mantle system either during or just after planetary accretion. To consider the behavior of H2O in the planetary interior it is specifically important to determine by what mechanism the planet is heated enough to cause melting. For Mars, the main heat source is probably accretional heating. Because Mars is small, the accretion energy needs to be effectively retained in its interior. Therefore, the three candidates of heat retention mechanism are discussed first: (1) the blanketing effect of the primordial H2-He atmosphere; (2) the blanketing effect of the impact-induced H2O-CO2 atmosphere; and (3) the higher deposition efficiency of impact energy due to larger impacts. It was concluded that (3) the is the most plausible mechanism for Mars. Then, its possible consequence on how wet the early martian mantle was is discussed.

  2. Carbon-coated SnO2 nanobelts and nanoparticles by single catalytic step

    NASA Astrophysics Data System (ADS)

    Carreño, Neftali L. V.; Nunes, Michael R.; Garcia, Irene T. S.; Orlandi, Marcelo O.; Fajardo, Humberto V.; Longo, Elson

    2009-05-01

    Several types of carbon nanostructures (amorphous and graphitic), for the coating of SnO2 nanobelts and nanoparticles were obtained by a single catalytic process, during methane, natural gas, and methanol decomposition using the reactivity of surface-modified SnO2 nanostructure as a nanotemplate. The nanostructured catalyst templates were based on transition metal nanoparticles supported on SnO2 nanobelts previously prepared by a carbothermal reduction process. Carbon-coated SnO2 nanopowders were also successfully synthesized for the fabrication of carbon spheres. The carbon coating process and yield, along with the nature of the nanostructured carbon, are strongly influenced by the chemically modified surface of the SnO2 nanostructure template and the chemical reaction gas composition. The preliminary catalytic activity and gas-sensing properties of these novel materials based on metal nanoparticles and carbon-coated SnO2 were determined.

  3. Catalytic gasification of biomass (Miscanthus) enhanced by CO2 sorption.

    PubMed

    Zamboni, I; Debal, M; Matt, M; Girods, P; Kiennemann, A; Rogaume, Y; Courson, C

    2016-11-01

    The main objective of this work concerns the coupling of biomass gasification reaction and CO2 sorption. The study shows the feasibility to promote biomass steam gasification in a dense fluidized bed reactor with CO2 sorption to enhance tar removal and hydrogen production. It also proves the efficiency of CaO-Ca12Al14O33/olivine bi-functional materials to reduce heavy tar production. Experiments have been carried out in a fluidized bed gasifier using steam as the fluidizing medium to improve hydrogen production. Bed materials consisting of CaO-based oxide for CO2 sorption (CaO-Ca12Al14O33) deposited on olivine for tar reduction were synthesized, their structural and textural properties were characterized by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), and temperature-programmed reduction (TPR) methods, and the determination of their sorption capacity and stability analyzed by thermogravimetric analysis (TGA). It appears that this CaO-Ca12Al14O33/olivine sorbent/catalyst presents a good CO2 sorption stability (for seven cycles of carbonation/decarbonation). Compared to olivine and Fe/olivine in a fixed bed reactor for steam reforming of toluene chosen as tar model compound, it shows a better hydrogen production rate and a lower CO2 selectivity due to its sorption on the CaO phase. In the biomass steam gasification, the use of CaO-Ca12Al14O33/olivine as bed material at 700 °C leads to a higher H2 production than olivine at 800 °C thanks to CO2 sorption. Similar tar concentration and lighter tar production (analyzed by HPLC/UV) are observed. At 700 °C, sorbent addition allows to halve tar content and to eliminate the heaviest tars.

  4. Heterogeneous catalytic conversion of CO2: a comprehensive theoretical review

    NASA Astrophysics Data System (ADS)

    Li, Yawei; Chan, Siew Hwa; Sun, Qiang

    2015-05-01

    The conversion of CO2 into fuels and useful chemicals has been intensively pursued for renewable, sustainable and green energy. However, due to the negative adiabatic electron affinity (EA) and large ionization potential (IP), the CO2 molecule is chemically inert, thus making the conversion difficult under normal conditions. Novel catalysts, which have high stability, superior efficiency and low cost, are urgently needed to facilitate the conversion. As the first step to design such catalysts, understanding the mechanisms involved in CO2 conversion is absolutely indispensable. In this review, we have summarized the recent theoretical progress in mechanistic studies based on density functional theory, kinetic Monte Carlo simulation, and microkinetics modeling. We focus on reaction channels, intermediate products, the key factors determining the conversion of CO2 in solid-gas interface thermocatalytic reduction and solid-liquid interface electrocatalytic reduction. Furthermore, we have proposed some possible strategies for improving CO2 electrocatalysis and also discussed the challenges in theory, model construction, and future research directions.

  5. Catalytic combustion of toluene on Pd/CeO2-TiO2 catalysts.

    PubMed

    Chen, Yu-Wen; Lee, Der-Shing

    2013-03-01

    Pd/TiO2 and Pd/CeO2 were reported to be very active to destruct toluene. Combination of TiO2 and CeO2 is an interesting candidate to achieve a catalyst with higher activity. In this study, a series of Pd/CeO2-TiO2 catalysts with various Pd loadings were prepared. CeO2-TiO2 was prepared by impregnation of aqueous solution of cerium nitrate into TiO2 support. It was then calcined at 400 degrees C. Pd was loaded by incipient-wetness impregnation method. The Pd loadings in all samples were fixed at 0.5 wt.%. The catalysts were characterized by powder X-ray diffraction, transmission electron microscopy, high resolution transmission electron microscopy, temperature-programmed reduction of hydrogen, and X-ray photoelectron spectroscopy. The catalysts were tested for total oxidation of toluene. The feed concentration of toluene was 8.564 g/m3 (2085 ppm), with GHSV = 10,000 h(-1). Pd particle sizes were 3-5 nm and well-dispersed on the support. CeO2 on TiO2 was easier to reduce than the bulk CeO2, therefore it could enhance the activity of VOC destruction. Pd/CeO2-TiO2 was more active than Pd/CeO2 and Pd/TiO2. Pd/CeO2-TiO2 with Ce/Ti ratio of 2/8 was very active for toluene destruction, due to its lower oxygen reduction temperature of ceria and higher concentration of Pd(0).

  6. Relating wetting and reduction processes in the Si-liquid/SiO2-solid interface

    NASA Astrophysics Data System (ADS)

    Alphei, L. D.; Grotjahn, R.; Dobbe, C.; Douvidzon, M.; Janhsen, R.; Gebensleben, T.; Alznauer, T.; Becker, V.; Becker, J. A.

    2015-06-01

    A reactive wetting model is presented which includes a gradual reduction of a silicon dioxide substrate lowering the interface tensions and promotes spreading. The gradual reduction is described in terms of a reaction diffusion layer that extends over multiple atomic layers. The formation of silicon-suboxides generated by the reduction leads to time dependent values for the surface tensions, which in turn change the apparent contact angle Θ (t). This model describes the reactive wetting process and its instabilities, provides simple expressions for the oxygen flow, and explains anisotropic wetting patterns observed on crystalline quartz substrates. The latter is achieved by a simple coupling of wetting and an ongoing solid state reaction in the substrate that reflects the symmetry of the crystal.

  7. Effect of Calcination Temperature on Surface Oxygen Vacancies and Catalytic Performance Towards CO Oxidation of Co3O4 Nanoparticles Supported on SiO2

    NASA Astrophysics Data System (ADS)

    Li, Jin-bing; Jiang, Zhi-quan; Qian, Kun; Huang, Wei-xin

    2012-02-01

    Co3O4/SiO2 catalysts for CO oxidation were prepared by conventional incipient wetness impregnation followed by calcination at various temperatures. Their structures were characterized with X-ray diffraction (XRD), laser Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR) and X-ray absorption fine structure (XAFS) spectroscopy. Both XRD and Raman spectroscopy only detect the existence of Co3O4 crystallites in all catalysts. However, XPS results indicate that excess Co2+ ions are present on the surface of Co3O4 in Co3O4(200)/SiO2 as compared with bulk Co3O4. Meanwhile, TPR results suggest the presence of surface oxygen vacancies on Co3O4 in Co3O4(200)/SiO2, and XAFS results demonstrate that Co3O4 in Co3O4(200)/SiO2 contains excess Co2+. Increasing calcination temperature results in oxidation of excess Co2+ and the decrease of the concentration of surface oxygen vacancies, consequently the formation of stoichiometric Co3O4 on supported catalysts. Among all Co3O4/SiO2 catalysts, Co3O4(200)/SiO2 exhibits the best catalytic performance towards CO oxidation, demonstrating that excess Co2+ and surface oxygen vacancies can enhance the catalytic activity of Co3O4 towards CO oxidation. These results nicely demonstrate the effect of calcination temperature on the structure and catalytic performance towards CO oxidation of silica-supported Co3O4 catalysts and highlight the important role of surface oxygen vacancies on Co3O4.

  8. Wire diameter dependence in the catalytic decomposition of H2

    NASA Astrophysics Data System (ADS)

    Umemoto, Hironobu

    2014-01-01

    Jansen et al. have demonstrated that the dissociaiton rate of H2 molecules on hot wire surfaces, normalized per unit surface area, depends on the wire diameter based on the electrical power consumption measurements [J. Appl. Phys. 66, 5749 (1989)]. Mathematical modeling calculations have also been presented to support their experimental results. In the present paper, it is shown that such a wire diameter dependence cannot be observed and that the H-atom density normalized by the wire surface area depends little on the wire diameter. Modeling calculations also show that the wire diameter dependence of the dissociation rate cannot be expected under typical decomposition conditions.

  9. Superhydrophobic TiO2 coatings formed through a non-fluorinated wet chemistry route

    NASA Astrophysics Data System (ADS)

    Holtzinger, C.; Niparte, B.; Wächter, S.; Berthomé, G.; Riassetto, D.; Langlet, M.

    2013-11-01

    We present a facile and low cost non-fluorinated wet chemistry route yielding rough and highly hydrophobic surfaces. This procedure is based on a nanosphere lithography (NSL) method using polystyrene (PS) spheres. Multilayer PS coatings were impregnated with a sol-gel TiO2 polymeric sol and then heat-treated at 500 °C. Derived NSL-structured TiO2 coatings were then grafted with hexadecyl trimethoxysilane (C16). The morphology of structured coatings was analyzed by optical, scanning electron, and atomic force microscopy, and the water wettability of TiO2 coating grafted with the C16 precursor was studied with respect to NSL features. It is shown that the synergy between the hydrophobicity imparted by the C16 precursor and roughness effects arising from NSL structuration leads to superhydrophobic coatings. In optimized conditions, the static contact angle of 11.6 μL water droplets deposited on the surface is around 160° with a corresponding tilt angle as low as 1°.

  10. Wet chemical methods for producing mixing crystalline phase ZrO2 thin film

    NASA Astrophysics Data System (ADS)

    Pakma, Osman; Özdemir, Cengiz; Kariper, İ. Afşin; Özaydın, Cihat; Güllü, Ömer

    2016-07-01

    The aim of the study is to develop a more economical and easier method for obtaining ZrO2 thin films at lower temperature, unlike the ones mentioned in the literature. For this purpose, wet chemical synthesis methods have been tested and XRD, UV-VIS and SEM analysis of ZrO2 thin films have been performed. At the end of the analysis, we identified the best method and it has been found that the features of the films produced with this method were better than the films produced by using different reagents, as well as the films reported in the literature. Especially it has been observed that the transmittance of the film produced with this method were higher and better than the films in the literature and the others. In addition, refractive index of the film produced with this method was observed to be lower. Moreover, by using the same method Al/ZrO2/p-Si structure has been obtained and it has been compared with Al/p-Si reference structure in terms of electrical parameters.

  11. Catalytic Thr or Ser Residue Modulates Structural Switches in 2-Cys Peroxiredoxin by Distinct Mechanisms

    PubMed Central

    Tairum, Carlos A.; Santos, Melina Cardoso; Breyer, Carlos A.; Geyer, R. Ryan; Nieves, Cecilia J.; Portillo-Ledesma, Stephanie; Ferrer-Sueta, Gerardo; Toledo, José Carlos; Toyama, Marcos H.; Augusto, Ohara; Netto, Luis E. S.; de Oliveira, Marcos A.

    2016-01-01

    Typical 2-Cys Peroxiredoxins (2-Cys Prxs) reduce hydroperoxides with extraordinary rates due to an active site composed of a catalytic triad, containing a peroxidatic cysteine (CP), an Arg, and a Thr (or Ser). 2-Cys Prx are involved in processes such as cancer; neurodegeneration and host-pathogen interactions. During catalysis, 2-Cys Prxs switch between decamers and dimers. Analysis of 2-Cys Prx structures in the fully folded (but not locally unfolded) form revealed a highly conserved, non-conventional hydrogen bond (CH-π) between the catalytic triad Thr of a dimer with an aromatic residue of an adjacent dimer. In contrast, structures of 2-Cys Prxs with a Ser in place of the Thr do not display this CH-π bond. Chromatographic and structural data indicate that the Thr (but not Ser) destabilizes the decamer structure in the oxidized state probably through steric hindrance. As a general trend, mutations in a yeast 2-Cys Prx (Tsa1) favoring the dimeric state also displayed a decreased catalytic activity. Remarkably, yeast naturally contains Thr-Ser variants (Tsa1 and Tsa2, respectively) with distinct oligomeric stabilities in their disulfide states. PMID:27629822

  12. Catalytical Photocyclization of Arylamines with a-Olefins in the Synthesis of 2-Alkylquinoline

    ERIC Educational Resources Information Center

    Makhmutov, Aynur; Usmanov, Salavat; Mustafin, Ahat

    2016-01-01

    The article deals with the results of investigation of the process of catalytical photocyclization of aniline and aniline hydrochloride with a-olefins (hexene-1, heptene-1 and octene-1). The following compounds of d- and f-metals are tested as probable catalysts: CuSO4•5H2O, EuCl3•6H2O, PrCl3•6H2O, TbCl3•6H2O, La2O3, MnO2, NiSO4•6H2O, NiCl2•6H2O,…

  13. Ruthenium nanoparticles supported on CeO2 for catalytic permanganate oxidation of butylparaben.

    PubMed

    Zhang, Jing; Sun, Bo; Guan, Xiaohong; Wang, Hui; Bao, Hongliang; Huang, Yuying; Qiao, Junlian; Zhou, Gongming

    2013-11-19

    This study developed a heterogeneous catalytic permanganate oxidation system with ceria supported ruthenium, Ru/CeO2 (0.8‰ as Ru), as catalyst for the first time. The catalytic performance of Ru/CeO2 toward butylparaben (BP) oxidation by permanganate was strongly dependent on its dosage, pH, permanganate concentration and temperature. The presence of 1.0 g L(-1) Ru/CeO2 increased the oxidation rate of BP by permanganate at pH 4.0-8.0 by 3-96 times. The increase in Ru/CeO2 dosage led to a progressive enhancement in the oxidation rate of BP by permanganate at neutral pH. The XANES analysis revealed that (1) Ru was deposited on the surface of CeO2 as Ru(III); (2) Ru(III) was oxidized by permanganate to its higher oxidation state Ru(VI) and Ru(VII), which acted as the co-oxidants in BP oxidation; (3) Ru(VI) and Ru(VII) were reduced by BP to its initial state of Ru(III). Therefore, Ru/CeO2 acted as an electron shuttle in catalytic permanganate oxidation process. LC-MS/MS analysis implied that BP was initially attacked by permanganate or Ru(VI) and Ru(VII) at the aromatic ring, leading to the formation of various hydroxyl-substituted and ring-opening products. Ru/CeO2 could maintain its catalytic activity during the six successive runs. In conclusion, catalyzing permanganate oxidation with Ru/CeO2 is a promising technology for degrading phenolic pollutants in water treatment.

  14. Synthesis of chitosan supported palladium nanoparticles and its catalytic activity towards 2-nitrophenol reduction

    NASA Astrophysics Data System (ADS)

    Dhanavel, S.; Nivethaa, E. A. K.; Esther, G.; Narayanan, V.; Stephen, A.

    2016-05-01

    Chitosan supported Palladium nanoparticles were synthesized by a simple cost effective chemical reduction method using NaBH4. The prepared nanocomposite was characterized by X-Ray diffraction analysis, FESEM and Energy dispersive spectroscopy analysis of X-rays (EDAX). The catalytic performance of the nanocomposite was evaluated on the reduction of 2-Nitrophenol to the 2-Amino phenol with rate constant 1.08 × 10-3 S-1 by NaBH4 using Spectrophotometer.

  15. Mesoporous SnO2-coated metal nanoparticles with enhanced catalytic efficiency.

    PubMed

    Zhou, Na; Polavarapu, Lakshminarayana; Wang, Qing; Xu, Qing-Hua

    2015-03-04

    Aggregation of plasmonic nanoparticles under harsh conditions has been one of the major obstacles to their potential applications. Here we present the preparation of uniform mesoporous SnO2 shell coated Au nanospheres, Au nanorods and Au/Ag core-shell nanorods and their applications in molecular sensing and catalysis. In these nanostructures, the mesoporous SnO2 shell stabilizes the metal nanoparticle and allows the metal core to be exposed to the surrounding environment for various applications at the same time. These nanostructures display high refractive index sensitivity, which makes them promising materials for LSPR based molecular sensing. Applications of these materials as catalysts for reduction of 4-nitrophenol by NaBH4 have also been demonstrated. Both uncoated and SnO2-coated anisotropic Au and Au/Ag nanorods were found to display significantly better catalytic efficiency compared to the corresponding spherical Au nanoparticles. Catalytic activities of different metal nanoparticles were significantly enhanced by 4-6 times upon coating with the mesoporous SnO2 shell. The enhanced catalytic activity of metal nanoparticles upon SnO2 coating was attributed to charge-redistribution between noble metal and SnO2 that disperses the electrons to a large area and prolonged electron lifetime in SnO2-coated metal nanoparticles. The charge transfer mechanism of enhanced catalytic efficiency for SnO2-coated metal nanoparticles has been further demonstrated by photochemical reduction of silver ions on the outer surface of these NPs. These metal/semiconductor core-shell nanomaterials are potentially useful for various applications such as molecular sensing and catalysis.

  16. Catalyst performance and mechanism of catalytic combustion of dichloromethane (CH2Cl2) over Ce doped TiO2.

    PubMed

    Cao, Shuang; Wang, Haiqiang; Yu, Feixiang; Shi, Mengpa; Chen, Shuang; Weng, Xiaole; Liu, Yue; Wu, Zhongbiao

    2016-02-01

    TiO2 and Ce/TiO2 were synthesized and subsequently used for the catalytic combustion of DCM. TiO2 had abundant Lewis acid sites and was responsible for the adsorption and the rupture of C-Cl bonds. However, TiO2 tended to be inactivated because of chloride poisoning due to the adsorption and accumulation of Cl species over the surface. While, Ce/TiO2 obtained total oxidation of CH2Cl2 at 335°C and exhibited stable DCM removal activity on 100h long-time stability tests at 330°C without any catalyst deactivation. The doped cerium generated Ce(3+) chemical states and surface active oxygen, and therefore played important roles from two aspects as follows. First of all, the poisoning of Cl for Ce/TiO2 was inhibited to some extent by CeO2 due to the rapid removal of Cl on the surface of CeO2, which has been verified by NH3-IR characterization. In the other hand, CeO2 enhanced the further deep oxidation of C-H from byproducts and retained the certain oxidation of CO to CO2. Based on the DRIFT characterization and the catalysts activity tests, a two-step reaction pathway for the catalytic combustion of DCM on Ce/TiO2 catalyst was proposed.

  17. Catalytic asymmetric Povarov reaction of isatin-derived 2-azadienes with 3-vinylindoles.

    PubMed

    Zhang, Hong-Hao; Sun, Xiao-Xue; Liang, Jing; Wang, Yue-Ming; Zhao, Chang-Chun; Shi, Feng

    2014-12-21

    The first catalytic asymmetric Povarov reaction of isatin-derived 2-azadienes with 3-vinylindoles was established in the presence of chiral phosphoric acid, which tolerates a wide range of substrates with generally excellent diastereoselectivity and good enantioselectivity (up to >95 : 5 dr, 89 : 11 er). This approach will greatly enrich the chemistry of the catalytic asymmetric Povarov reaction, in particular ketone-involved transformations. Furthermore, this protocol represents the first diastereo- and enantio-selective construction of a spiro[indolin-3,2'-quinoline] framework bearing an indole moiety. This novel type of spiro-compound not only contains two chiral centers, including one quaternary stereogenic center, but also integrates two biologically important structures of spiro[indolin-3,2'-quinoline] and indole, which may find medicinal applications after bioassay.

  18. Water Vapor and Wet Tropospheric Path Delay estimation from HY-2A Calibration Microwave Radiometer

    NASA Astrophysics Data System (ADS)

    Yang, J.; Zheng, G.; Ren, L.

    2016-12-01

    The data of Jason-1 microwave radiometer (JMR) and Jason-2 advanced microwave radiometer (AMR) are used as reference for the development and validation of retrieval models of water vapor (WV) and wet tropospheric path delay (PD) for the calibration microwave radiometer (CMR) on board the first ocean dynamic environment satellite of China—Haiyang-2A (HY-2A). The crossover points of the HY-2A and Jason-1/2 satellite tracks are extracted, and the data pairs at these points are divided into fitting and validation datasets. The retrieval models of WV and PD are built for the CMR using the fitting dataset and genetic algorithm, and validated using the validation dataset. The validation shows that the results of the retrieval models are consistent with the JMR and AMR data, and the root-mean-square differences of WV and PD are 1.86 kgm-2 and 11.4mm, respectively. Finally, the retrieved results from the CMR brightness temperature along-track data using the retrieval models and the AMR along-track data are gridded by the inverse distance weighted method. Their monthly-mean spatial distributions are compared in order to investigate the applicability of the retrieval models globally, namely, beyond locations of the data pairs in the validation dataset. The comparison shows that the retrieval models are applicable in most open ocean areas, and that the latitude and temporal inhomogeneity of the crossover point distribution in the fitting dataset does not lead to obvious latitude and temporal inhomogeneity in the gridded data.

  19. Superiority of wet-milled over dry-milled superfine powdered activated carbon for adsorptive 2-methylisoborneol removal.

    PubMed

    Pan, Long; Matsui, Yoshihiko; Matsushita, Taku; Shirasaki, Nobutaka

    2016-10-01

    Superfine powdered activated carbon (SPAC), which is produced from conventionally sized powdered activated carbon (PAC) by wet milling in a bead mill, has attracted attention for its high adsorptive removal ability in both research and practice. In this study, the performance of dry-milled SPAC was investigated. 2-Methylisoborneol (MIB), an earthy-musty compound commonly targeted by water treatment systems, was used as the target adsorbate. Dry-milled SPAC exhibited lower adsorptive removal of MIB than wet-milled SPAC, even when both SPACs were produced from the same PAC and were composed of particles of the same size. One reason for the lower removal of MIB by the dry-milled SPAC was a higher degree of aggregation in the dry-milled SPAC after production; as a result the apparent particle size of dry-milled SPAC was larger than that of wet-milled SPAC. The dry-milled SPAC was also more negatively charged than the wet-milled SPAC, and, owing to its higher repulsion, it was more amenable to dispersion by ultrasonication. However, even after the dry-milled SPAC was ultrasonicated so that its apparent particle size was similar to or less than that of the wet-milled SPAC, the dry-milled SPAC was still inferior in adsorptive removal to the wet-milled SPAC. Therefore, another reason for the lower adsorptive removal of dry-milled SPAC was its lower equilibrium adsorption capacity due to the oxidation during the milling. The adsorption kinetics by SPACs with different degrees of particle aggregation were successfully simulated by a pore diffusion model and a fractal aggregation model.

  20. Covalent organic frameworks comprising cobalt porphyrins for catalytic CO2 reduction in water

    SciTech Connect

    Lin, S.; Diercks, C. S.; Zhang, Y. -B.; Kornienko, N.; Nichols, E. M.; Zhao, Y.; Paris, A. R.; Kim, D.; Yang, P.; Yaghi, O. M.; Chang, C. J.

    2015-08-20

    Conversion of carbon dioxide (CO2) to carbon monoxide (CO) and other value-added carbon products is an important challenge for clean energy research. Here we report modular optimization of covalent organic frameworks (COFs), in which the building units are cobalt porphyrin catalysts linked by organic struts through imine bonds, to prepare a catalytic material for aqueous electrochemical reduction of CO2 to CO. The catalysts exhibit high Faradaic efficiency (90%) and turnover numbers (up to 290,000, with initial turnover frequency of 9400 hour-1) at pH 7 with an overpotential of –0.55 volts, equivalent to a 26-fold improvement in activity compared with the molecular cobalt complex, with no degradation over 24 hours. X-ray absorption data reveal the influence of the COF environment on the electronic structure of the catalytic cobalt centers.

  1. [Impacts of AOC by O3/TiO2 catalytic oxidation in drinking water].

    PubMed

    Liang, Tao; Ma, Jun; Wang, Sheng-jun; Yang, Yi-xin; Zhang, Jing

    2007-09-01

    This paper presents catalytic oxidation with titanium dioxide nano-particles loaded on several selected carriers, which are ceramic, silica gel and zeolite, to remove nitrobenzene from drinking water in ozonation. In this study assimilable organic carbon (AOC) is our interest and assumed as a parameter responsible for low molecule organic carbon such as ketone, aldehyde, alcohols and carboxyl acids in drinking water. Catalytic oxidation is more effective than ozonation alone in the degradation of larger fractions of organics to lower fractions. AOC was increased from 300 microg/L to 674.1 microg x L(-1), 847.2 microg x L(-1) and 882.1 microg x L(-1) by the catalysis ozonation of cerami/TiO2, silica gel/TiO2, cerami/TiO2 respectively, and the proportion of AOC in TOC can be increased from 4.68% to 30.5%, 33.21% and 46.04%, respectively. The catalytic oxidation enhanced the biologradability of organics in the water greatly. With the ozone dosage increase, AOC began to reduce slightly because the low molecular size organic carbon was mineralized. In the processes, AOC-NOX consisting of carboxyl acid mostly increased rapidly, resulting in increase of the proportion of AOC-NOX in AOC over 90% and the majority of AOC turned from AOC-P17 to AOC-NOX.

  2. Isolated metal active site concentration and stability control catalytic CO2 reduction selectivity.

    PubMed

    Matsubu, John C; Yang, Vanessa N; Christopher, Phillip

    2015-03-04

    CO2 reduction by H2 on heterogeneous catalysts is an important class of reactions that has been studied for decades. However, atomic scale details of structure-function relationships are still poorly understood. Particularly, it has been suggested that metal particle size plays a unique role in controlling the stability of CO2 hydrogenation catalysts and the distribution of active sites, which dictates reactivity and selectivity. These studies often have not considered the possible role of isolated metal active sites in the observed dependences. Here, we utilize probe molecule diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) with known site-specific extinction coefficients to quantify the fraction of Rh sites residing as atomically dispersed isolated sites (Rhiso), as well as Rh sites on the surface of Rh nanoparticles (RhNP) for a series of TiO2 supported Rh catalysts. Strong correlations were observed between the catalytic reverse water gas shift turn over frequency (TOF) and the fraction of Rhiso sites and between catalytic methanation TOF and the fraction of RhNP sites. Furthermore, it was observed that reaction condition-induced disintegration of Rh nanoparticles, forming Rhiso active sites, controls the changing reactivity with time on stream. This work demonstrates that isolated atoms and nanoparticles of the same metal on the same support can exhibit uniquely different catalytic selectivity in competing parallel reaction pathways and that disintegration of nanoparticles under reaction conditions can play a significant role in controlling stability.

  3. The StreamCat Dataset: Accumulated Attributes for NHDPlusV2 Catchments (Version 2.1) for the Conterminous United States: Wetness Index

    EPA Pesticide Factsheets

    This dataset represents the wetness index within individual local NHDPlusV2 catchments and upstream, contributing watersheds based on the Composite Topographic Index (See Supplementary Info for Glossary of Terms). The Composite Topographic Index (CTI) is based on contributing area, slope, and overland flow and has been developed internally at the EPA for the EnviroAtls (http://edg.epa.gov/data/Public/ORD/EnviroAtlas/National/). As defined for use in EnviroAtlas datasets and as used here, ??wet areas are typically created by runoff from natural land cover when rain falls on saturated soil. Surface and rill (or small channel) runoff carries excess water to lowland depressions or wet areas. Runoff collects in wet areas until they fill and overflow downstream. In this way, stream networks can be extended into new areas that would not be hydrologically connected during drier times. Wet area expansion and watershed hydrological connectivity differ between humid temperate and semi-arid and arid climates (where drought and soil crusts limit infiltration and produce flashier runoff)?? (from https://enviroatlas.epa.gov/enviroatlas/datafactsheets/pdf/ESN/PercentForestonWetAreas.pdf). The Mean Composite Topographic Index (CTI)[Wetness Index] were summarized to produce local catchment-level and watershed-level metrics as a continuous data type (see Data Structure and Attribute Information for a description).

  4. The remarkable effect of oxygen on the N2 selectivity of water catalytic denitrification by hydrogen.

    PubMed

    Constantinou, Costas L; Costa, Costas N; Efstathiou, Angelos M

    2007-02-01

    The selective catalytic reduction of nitrates (NO3-) in pure water toward N2 formation by the use of gaseous H2 and in the presence of O2 (air) at 1 atm total pressure and 25 degrees C has been investigated over Pd-Cu supported on various mixed metal oxides, x wt % MO(x(/gamma-Al2O3 (MO(x) = CeO2, SrO, Mn2O3, Cr2O3, Y2O3, and TiO2). It is demonstrated for the firsttime that a remarkable improvement in N2 reaction selectivity (by 80 percentage units) can be achieved when oxygen is present in the reducing feed gas stream. In particular, significantly lower reaction selectivities toward NH4+ and NO2- can be obtained, whereas the rate of NO3- conversion is not significantly affected. Moreover, it was shown thatthe same effect is obtained over the Pd-Cu-supported catalysts irrespective to the chemical composition of support and the initial concentration of nitrates in water used. The Pd-Cu clusters supported on 4.8 wt%TiO2/gamma-Al2O3 resulted in a solid with the best catalytic behavior compared with the rest of supports examined, both in the presence and in the absence of oxygen in the reducing feed gas stream. DRIFTS studies performed following catalytic reduction by H2 of NO3- in water revealed that the presence of TiO2 in the Pd-Cu/TiO2-Al2O3 system enhanced the reactivity of adsorbed bidentate nitrate species toward H2. Nitrosyl species adsorbed on the alumina and titania support surfaces are considered as active intermediate species of the selective catalytic reduction of NO3- by H2 in water. Pd-Cu/TiO2-Al2O3 appears to be the most selective catalyst ever reported in the literature for the reduction of nitrates present in pure water into N2 by a reducing gas mixture of H2/air.

  5. Catalytic Enzyme-Based Methods for Water Treatment and Water Distribution System Decontamination. 2. Experimental Results

    DTIC Science & Technology

    2006-06-01

    with paraoxon in the bench studies. This change was prompted by purity problems associated with the p- nitrophenyl Soman synthesis needed for the 2... nitrophenyl Soman synthesis by a local chemist precluded its use for the bench studies. As such, paraoxon was used as the substrate for OPAA as well. Based...Paraoxon was used as an OPH substrate, as p- nitrophenyl Soman hydrolytic activity is a very poor substrate for OPH. Although OPAA has better catalytic

  6. Numerical evidence of hyperscaling violation in wetting transitions of the random-bond Ising model in d =2 dimensions

    NASA Astrophysics Data System (ADS)

    Albano, Ezequiel V.; Luque, Luciana; Trobo, Marta L.; Binder, Kurt

    2017-02-01

    We performed extensive simulations of the random-bond Ising model confined between walls where competitive surface fields act. By properly taking the thermodynamic limit we unambiguously determined wetting transition points of the system, as extrapolation of localization-delocalization transitions of the interface between domains of different orientation driven by the respective fields. The finite-size scaling theory for wetting with short-range fields [E. V. Albano and K. Binder, Phys. Rev. Lett. 109, 036101 (2012), 10.1103/PhysRevLett.109.036101] establishes that the average magnetization of the sample, with critical exponent β , is the proper order parameter for the study of wetting. While the hyperscaling relationship given by γ +2 β =ν∥+ν⊥ requires β =1 /2 (γ =4 , ν∥=3 , and ν⊥=2 ), the thermodynamic scaling establishes that Δs=γ +β , which in contrast requires β =0 (Δs=4 ), where γ , ν∥, ν⊥, and Δs are the critical exponents of the susceptibility, the correlation lengths parallel and perpendicular to the interface, and the gap exponent, respectively. So, we formulate a finite-size scaling theory for wetting without hyperscaling and perform numerical simulations that provide strong evidence of hyperscaling violation (i.e., β =0 ) and a direct measurement of the susceptibility critical exponent γ /ν⊥=2.0 ±0.2 , in agreement with theoretical results for the strong fluctuation regime of wetting transitions with quenched noise.

  7. Numerical evidence of hyperscaling violation in wetting transitions of the random-bond Ising model in d=2 dimensions.

    PubMed

    Albano, Ezequiel V; Luque, Luciana; Trobo, Marta L; Binder, Kurt

    2017-02-01

    We performed extensive simulations of the random-bond Ising model confined between walls where competitive surface fields act. By properly taking the thermodynamic limit we unambiguously determined wetting transition points of the system, as extrapolation of localization-delocalization transitions of the interface between domains of different orientation driven by the respective fields. The finite-size scaling theory for wetting with short-range fields [E. V. Albano and K. Binder, Phys. Rev. Lett. 109, 036101 (2012)PRLTAO0031-900710.1103/PhysRevLett.109.036101] establishes that the average magnetization of the sample, with critical exponent β, is the proper order parameter for the study of wetting. While the hyperscaling relationship given by γ+2β=ν_{∥}+ν_{⊥} requires β=1/2 (γ=4, ν_{∥}=3, and ν_{⊥}=2), the thermodynamic scaling establishes that Δ_{s}=γ+β, which in contrast requires β=0 (Δ_{s}=4), where γ, ν_{∥}, ν_{⊥}, and Δ_{s} are the critical exponents of the susceptibility, the correlation lengths parallel and perpendicular to the interface, and the gap exponent, respectively. So, we formulate a finite-size scaling theory for wetting without hyperscaling and perform numerical simulations that provide strong evidence of hyperscaling violation (i.e., β=0) and a direct measurement of the susceptibility critical exponent γ/ν_{⊥}=2.0±0.2, in agreement with theoretical results for the strong fluctuation regime of wetting transitions with quenched noise.

  8. Supercritical CO{sub 2} mediated synthesis and catalytic activity of graphene/Pd nanocomposites

    SciTech Connect

    Tang, Lulu; Nguyen, Van Hoa; Shim, Jae-Jin

    2015-11-15

    Highlights: • RGO/Pd composite was efficiently prepared via a facile method in supercritical CO{sub 2}. • Graphene sheets were coated uniformly with Pd nanoparticles with a size of ∼8 nm. • Composites exhibited excellent catalytic activity in the Suzuki reaction even after 10 cycles. - Abstract: Graphene sheets were decorated with palladium nanoparticles using a facile and efficient method in supercritical CO{sub 2}. The nanoparticles were formed on the graphene sheets by the simple hydrogen reduction of palladium(II) hexafluoroacetylacetonate precursor in supercritical CO{sub 2}. The product was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. Highly dispersed nanoparticles with various sizes and shapes adhered well to the graphene sheets. The composites showed high catalytic activities for the Suzuki reaction under aqueous and aerobic conditions within 5 min. The effects of the different Pd precursor loadings on the catalytic activities of the composites were also examined.

  9. Study of the dynamics of the MoO2-Mo2C system for catalytic partial oxidation reactions

    NASA Astrophysics Data System (ADS)

    Cuba Torres, Christian Martin

    On a global scale, the energy demand is largely supplied by the combustion of non-renewable fossil fuels. However, their rapid depletion coupled with environmental and sustainability concerns are the main drivers to seek for alternative energetic strategies. To this end, the sustainable generation of hydrogen from renewable resources such as biodiesel would represent an attractive alternative solution to fossil fuels. Furthermore, hydrogen's lower environmental impact and greater independence from foreign control make it a strong contender for solving this global problem. Among a wide variety of methods for hydrogen production, the catalytic partial oxidation offers numerous advantages for compact and mobile fuel processing systems. For this reaction, the present work explores the versatility of the Mo--O--C catalytic system under different synthesis methods and reforming conditions using methyl oleate as a surrogate biodiesel. MoO2 exhibits good catalytic activity and exhibits high coke-resistance even under reforming conditions where long-chain oxygenated compounds are prone to form coke. Moreover, the lattice oxygen present in MoO2 promotes the Mars-Van Krevelen mechanism. Also, it is introduced a novel beta-Mo2C synthesis by the in-situ formation method that does not utilize external H2 inputs. Herein, the MoO 2/Mo2C system maintains high catalytic activity for partial oxidation while the lattice oxygen serves as a carbon buffer for preventing coke formation. This unique feature allows for longer operation reforming times despite slightly lower catalytic activity compared to the catalysts prepared by the traditional temperature-programmed reaction method. Moreover, it is demonstrated by a pulse reaction technique that during the phase transformation of MoO2 to beta-Mo2C, the formation of Mo metal as an intermediate is not responsible for the sintering of the material wrongly assumed by the temperature-programmed method.

  10. Highly enantioselective synthesis of 5-phenyl-2-alkylprolines using phase-transfer catalytic alkylation.

    PubMed

    Lee, Myungmo; Lee, Young-Ju; Park, Eunyoung; Park, Yohan; Ha, Min Woo; Hong, Suckchang; Lee, Yeon-Ju; Kim, Taek-Soo; Kim, Mi-hyun; Park, Hyeung-geun

    2013-03-28

    An efficient enantioselective synthetic method for the synthesis of (2R)-5-phenyl-2-alkylproline tert-butyl esters was reported. The phase-transfer catalytic alkylation of tert-butyl-5-phenyl-3,4-dihydro-2H-pyrrole-2-carboxylate in the presence of chiral quaternary ammonium catalysts gave the corresponding alkylated products (up to 97% ee). The following diastereoselective reductions afforded chiral 5-phenyl-2-alkylprolines which can be applied to asymmetric synthesis as organocatalysts or synthesis of biologically active proline based compounds, such as chiral α-alkylated analogues of (+)-RP66803, as potential CCK antagonists.

  11. TiO2 nanoparticles doped SiO2 films with ordered mesopore channels: a catalytic nanoreactor.

    PubMed

    Saha, Jony; Mitra, Anuradha; Dandapat, Anirban; De, Goutam

    2014-04-07

    Titanium dioxide (TiO2) incorporated ordered 2D hexagonal mesoporous silica (SiO2) films on a glass substrate were fabricated for use as a catalytic nanoreactor. Films were prepared using a tetraethyl orthosilicate (TEOS) derived SiO2 sol and a commercially available dispersion of TiO2 nanoparticles (NPs) in the presence of pluronic P123 as the structure directing agent. The effect of TiO2 doping (4-10 mol% with respect to the equivalent SiO2) into the ordered mesoporous SiO2 matrix was thoroughly investigated. The undoped SiO2 film showed a mesostructural transformation after heat-treatment at 350 °C whereas incorporation of TiO2 restricted such a transformation. Among all the TiO2 incorporated films, TEM showed that the 7 equivalent mol% TiO2 doped SiO2 film (ST-7) had an optimal composition which could retain the more organized 2D hexagonal (space group p6mm)-like mesostructures after heat-treatment. The catalytic activities of the TiO2 doped (4-10 mol%) films were investigated for the reduction of toxic KMnO4 in an aqueous medium. ST-7 film showed the maximum catalytic activity, as well as reusability. A TEM study on the resultant solution after KMnO4 reduction revealed the formation of MnO2 nanowires. It was understood that the embedded TiO2 NPs bonded SiO2 matrix increased the surface hydroxyl groups of the composite films resulting in the generation of acidic sites. The catalytic process can be explained by this enhanced surface acidity. The mesoporous channel of the ST-7 films with TiO2 doping can be used as a nanoreactor to form extremely thin MnO2 nanowires.

  12. Catalytic hydrogenation of CO2 over Pt- and Ni-doped graphene: A comparative DFT study.

    PubMed

    Esrafili, Mehdi D; Sharifi, Fahimeh; Dinparast, Leila

    2017-08-28

    Today, the global greenhouse effect of carbon dioxide (CO2) is a serious environmental problem. Therefore, developing efficient methods for CO2 capturing and conversion to valuable chemicals is a great challenge. The aim of the present study is to investigate the catalytic activity of Pt- or Ni-doped graphene for the hydrogenation of CO2 by a hydrogen molecule. To gain a deeper insight into the catalytic mechanism of this reaction, the reliable density functional theory calculations are performed. The adsorption energies, geometric parameters, reaction barriers, and thermodynamic properties are calculated using the M06-2X density functional. Two reaction mechanisms are proposed for the hydrogenation of CO2. In the bimolecular mechanism, the reaction proceeds in two steps, initiating by the co-adsorption of CO2 and H2 molecules over the surface, followed by the formation of a OCOH intermediate by the transfer of H atom of H2 toward O atom of CO2. In the next step, formic acid is produced as a favorable product with the formation of CH bond. In our proposed termolecular mechanism, however, H2 molecule is directly activated by the two pre-adsorbed CO2 molecules. The predicted activation energy for the formation of the OCOH intermediate in the bimolecular mechanism is 20.8 and 47.9kcalmol(-1) over Pt- and Ni-doped graphene, respectively. On the contrary, the formation of the first formic acid in the termolecular mechanism is found as the rate-determining step over these surfaces, with an activation energy of 28.8 and 45.5kcal/mol. Our findings demonstrate that compared to the Ni-doped graphene, the Pt-doped surface has a relatively higher catalytic activity towards the CO2 reduction. These theoretical results could be useful in practical applications for removal and transformation of CO2 to value-added chemical products. Copyright © 2017 Elsevier Inc. All rights reserved.

  13. Evaluation of wet tantalum capacitors after exposure to extended periods of ripple current, volume 2

    NASA Technical Reports Server (NTRS)

    Ward, C. M.

    1975-01-01

    The application of tantalum capacitors in the Viking Lander includes dc voltage and ripple current electrical stress, high temperature during nonoperating times (sterilization), and high vibration and shock loads. The capacitors must survive these severe environments without any degradation if reliable performance is to be achieved. A test program was established to evaluate both wet-slug tantalum and wet-foil capacitors under conditions accurately duplicating actual Viking applications. Test results of the electrical performance characteristics during extended periods of ripple current, the characteristics of the internal silver migration as a function of extended periods of ripple current, and the existence of any memory characteristics are presented.

  14. Investigation of Potassium Feldspar Reactivity in Wet Supercritical CO2 by In Situ Infrared Spectroscopy

    NASA Astrophysics Data System (ADS)

    Thompson, C.; Widener, C.; Schaef, T.; Loring, J.; McGrail, B. P.

    2014-12-01

    Capture and subsequent storage of CO2 in deep geologic reservoirs is progressively being considered as a viable approach to reduce anthropogenic greenhouse gas emissions. In the long term, injected CO2 may become permanently entrapped as silicate minerals react with CO2 enriched fluids to form stable carbonate minerals. Potassium feldspars are highly abundant in the earth's crust and are present in the caprocks and storage formations of many target reservoirs. While the dissolution kinetics and carbonation reactions of feldspars have been well studied in the aqueous phase, comparatively little work has focused on K-feldspar reactivity in the CO2-rich fluid. In this study, we used in situ infrared spectroscopy to investigate the carbonation reactions of natural microcline samples. Experiments were carried out at 50 °C and 91 bar by circulating dry or wet supercritical CO2 (scCO2) past a thin film of powdered sample. Water concentrations ranged from 0% to 125% relative to saturation, and transmission-mode absorbance spectra were recorded as a function of time for 48 hours. No discernible reaction was detected when the samples were exposed to anhydrous scCO2. However, in fully water-saturated scCO2, a thin film of liquid-like water was observed on the samples' surfaces, and up to 0.6% of the microcline was converted to a carbonate phase. Potassium carbonate is the most likely reaction product, but minor amounts of sodium carbonate and siderite may also have formed from minor sample impurities. The extent of reaction appears to be related to the thickness of the water film and is likely a consequence of the film's ability to solvate and transport ions in the vicinity of the mineral surface. Other features observed in the spectra correspond to microcline dissolution and precipitation of amorphous silica. Implications about the role of water in these reactions and the relative effectiveness of alkali feldspars for mineral trapping of CO2 will be discussed.

  15. Wet air oxidation of pretreatment of pharmaceutical wastewater by Cu2+ and [PxWmOy]q- co-catalyst system.

    PubMed

    Wang, Guowen; Wang, Dong; Xu, Xiaochen; Liu, Lifen; Yang, Fenglin

    2012-05-30

    This study concentrates on the pretreatment of real wastewater using catalytic wet air oxidation (CWAO). WO(3-) and PO(4)(3-) contained in fosfomycin pharmaceutical wastewater (FPW) and Cu(2+) contained in berberine pharmaceutical wastewater (BPW) were studied as CWAO influent. Mixture of this two streams were reused to form Cu(2+) and [P(x)W(m)O(y)](q-), namely polyoxometalates (POMs) as co-catalyst system to treat themselves. Experiments were conducted to investigate the effects of the initial oxygen pressure and temperature on the COD (chemical oxygen demand), TOC (total organic carbon) removal and biodegradable enhancement, it was discovered that over 40% of COD and TOC removal can be easily realized in an hour of WAO oxidation at 523 K, 1.4 MPa. The BOD(5)/COD (BOD(5), biochemical oxygen demand in 5 days) of this two pharmaceutical mixture ascended from nonexistent to maximum 0.41 depends on the optimal FPW:BPW volume ratio 4:1, to compose POM co-catalyst system. Organic pollutants were incompletely oxidized to propionic acid and other intermediates. Some properties (e.g., TGA, IR, XRF) of POM catalyst separated from effluent, were obtained to provide additional information.

  16. Preparation and catalytic performance of ZrO2 - nanographene platelets composites

    NASA Astrophysics Data System (ADS)

    Kristianto, Y.; Taufik, A.; Saleh, R.

    2016-11-01

    The ZrO2/Nanographene platelets (NGP) composites with different NGP weight percents were successfully synthesized using two-step methods (sol-gel followed by coprecipitation methods). The structural properties of the composites were analyzed using X-Ray Diffraction (XRD), Energy Dispersive X-Ray (EDX), Transmission Electron Microscope (TEM), and Thermalgravimetric Analysis (TGA). The presence of NGP in the composites confirms by the graphitic-like structure in the XRD and layer-like structure in the TEM. Thermal stability of the composites tends to reduce with the incorporation of NGP. The catalytic performances of the composites were evaluated by three catalytic processes. The degradation of methylene blue as a model pollutant by the composites are monitored using UV-Vis Spectroscopy. The result shows that ZrO2 with 10 wt% of NGP exhibits the highest performance for all of three processes. The scavenger experiment shows that hole acts as an active species that play a role in the catalytic process of the composites.

  17. Effects of FGFR2 kinase activation loop dynamics on catalytic activity

    PubMed Central

    2017-01-01

    The structural mechanisms by which receptor tyrosine kinases (RTKs) regulate catalytic activity are diverse and often based on subtle changes in conformational dynamics. The regulatory mechanism of one such RTK, fibroblast growth factor receptor 2 (FGFR2) kinase, is still unknown, as the numerous crystal structures of the unphosphorylated and phosphorylated forms of the kinase domains show no apparent structural change that could explain how phosphorylation could enable catalytic activity. In this study, we use several enhanced sampling molecular dynamics (MD) methods to elucidate the structural changes to the kinase’s activation loop that occur upon phosphorylation. We show that phosphorylation favors inward motion of Arg664, while simultaneously favoring outward motion of Leu665 and Pro666. The latter structural change enables the substrate to bind leading to its resultant phosphorylation. Inward motion of Arg664 allows it to interact with the γ-phosphate of ATP as well as the substrate tyrosine. We show that this stabilizes the tyrosine and primes it for the catalytic phosphotransfer, and it may lower the activation barrier of the phosphotransfer reaction. Our work demonstrates the value of including dynamic information gleaned from computer simulation in deciphering RTK regulatory function. PMID:28151998

  18. Effects of FGFR2 kinase activation loop dynamics on catalytic activity.

    PubMed

    Karp, Jerome M; Sparks, Samuel; Cowburn, David

    2017-02-01

    The structural mechanisms by which receptor tyrosine kinases (RTKs) regulate catalytic activity are diverse and often based on subtle changes in conformational dynamics. The regulatory mechanism of one such RTK, fibroblast growth factor receptor 2 (FGFR2) kinase, is still unknown, as the numerous crystal structures of the unphosphorylated and phosphorylated forms of the kinase domains show no apparent structural change that could explain how phosphorylation could enable catalytic activity. In this study, we use several enhanced sampling molecular dynamics (MD) methods to elucidate the structural changes to the kinase's activation loop that occur upon phosphorylation. We show that phosphorylation favors inward motion of Arg664, while simultaneously favoring outward motion of Leu665 and Pro666. The latter structural change enables the substrate to bind leading to its resultant phosphorylation. Inward motion of Arg664 allows it to interact with the γ-phosphate of ATP as well as the substrate tyrosine. We show that this stabilizes the tyrosine and primes it for the catalytic phosphotransfer, and it may lower the activation barrier of the phosphotransfer reaction. Our work demonstrates the value of including dynamic information gleaned from computer simulation in deciphering RTK regulatory function.

  19. PREFACE: Dynamics of wetting Dynamics of wetting

    NASA Astrophysics Data System (ADS)

    Grest, Gary S.; Oshanin, Gleb; Webb, Edmund B., III

    2009-11-01

    Capillary phenomena associated with fluids wetting other condensed matter phases have drawn great scientific interest for hundreds of years; consider the recent bicentennial celebration of Thomas Young's paper on equilibrium contact angles, describing the geometric shape assumed near a three phase contact line in terms of the relevant surface energies of the constituent phases [1]. Indeed, nearly a century has passed since the seminal papers of Lucas and Washburn, describing dynamics of capillary imbibition [2, 3]. While it is generally appreciated that dynamics of fluid wetting processes are determined by the degree to which a system is out of capillary equilibrium, myriad complications exist that challenge the fundamental understanding of dynamic capillary phenomena. The topic has gathered much interest from recent Nobel laureate Pierre-Gilles de Gennes, who provided a seminal review of relevant dissipation mechanisms for fluid droplets spreading on solid surfaces [4] Although much about the dynamics of wetting has been revealed, much remains to be learned and intrinsic technological and fundamental interest in the topic drives continuing high levels of research activity. This is enabled partly by improved experimental capabilities for resolving wetting processes at increasingly finer temporal, spatial, and chemical resolution. Additionally, dynamic wetting research advances via higher fidelity computational modeling capabilities, which drive more highly refined theory development. The significance of this topic both fundamentally and technologically has resulted in a number of reviews of research activity in wetting dynamics. One recent example addresses the evaluation of existing wetting dynamics theories from an experimentalist's perspective [5]. A Current Opinion issue was recently dedicated to high temperature capillarity, including dynamics of high temperature spreading [6]. New educational tools have recently emerged for providing instruction in wetting

  20. Catalytic Hydrothermal Gasification of Wet Biomass Feedstock

    SciTech Connect

    2006-04-01

    Industries and municipalities generate substantial amounts of biomass as high-moisture waste streams, such as animal manure, food processing sludge, stillage from ethanol production, and municipal wastewater sludge.

  1. HIPK2 catalytic activity and subcellular localization are regulated by activation-loop Y354 autophosphorylation

    PubMed Central

    Siepi, Francesca; Gatti, Veronica; Camerini, Serena; Crescenzi, Marco; Soddu, Silvia

    2013-01-01

    HIPK2 (homeodomain-interacting protein kinase-2) binds to and phosphorylates, at Ser and Thr residues, a large number of targets involved in cell division and cell fate decision in response to different physiological or stress stimuli. Inactivation of HIPK2 has been observed in human and mouse cancers supporting its role as a tumor suppressor. Despite the biological relevance of this kinase, very little is known on how HIPK2 becomes catalytically active. Based on sequence homologies, HIPK2 has been taxonomically classified as a subfamily member of the dual-specificity tyrosine-regulated kinases (DYRKs) and the activation-loop Y354 of HIPK2 has been found phosphorylated in different cells; however, the relevance of this Y phosphorylation is presently unknown. Here, we show that HIPK2, which is extensively phosphorylated at S/T sites throughout its functional domains, becomes catalytically active by autophosphorylation at the activation-loop Y354. In particular, we found that, in analogy to DYRKs, HIPK2-Y354 phosphorylation is an autocatalytic event and its prevention, through Y354 substitution with non-phosphorylatable amino acids or by using the kinase inhibitor purvalanol A, induces a strong reduction of the HIPK2 S/T-kinase activity on different substrates. Interestingly, at variance from DYRKs, inhibition of HIPK2-Y354 phosphorylation induces a strong out-of-target Y-kinase activity in cis and a strong cytoplasmic relocalization of the kinase. Together, these results demonstrate that the catalytic activity, substrate specificity, and subcellular localization of HIPK2 are regulated by autophosphorylation of its activation-loop Y354. PMID:23485397

  2. Wetting-induced pulses produced unexpectedly high emissions of N2O and NOx in a desert ecosystem

    NASA Astrophysics Data System (ADS)

    Eberwein, J. R.; Carey, C.; Aronson, E. L.; Jenerette, D.

    2015-12-01

    Approximately one third of Earth's land surface is subjected to arid conditions, and aridland soils have the potential for significant feedbacks to global climate change drivers, such as anthropogenic nitrogen deposition. This study examined wetting-induced pulses of N2O and NOx along a nitrogen deposition gradient in the Colorado Desert of southern California. Measurements were made before and following water (to simulate a 2 cm rain event) and nitrogen plus water additions (30 kg NH4NO3 ha-1) at 15 minutes, 12 hours and 24 hours post-wetting. We found nitrogenous fluxes that were substantially higher than expected. N2O fluxes, in particular were remarkably high reaching up to 200 ng N2O-N m-2 s-1, similar to agriculture levels and in the range of peat bog emissions. There was a clear transition between N2O emissions, which peaked 15 minutes after wetting, and NOx emissions, which peaked at the 12 hour timepoint. NOx emissions were also considerable, reaching as high as 350 ng NOx-N m-2 s-1. Both N2O and NOx fluxes responded strongly to water additions, demonstrating a clear wetting-induced pulse response. While N2O was not affected by nitrogen additions, NOx fluxes demonstrated a significant increase with nitrogen plus water over water alone (p=0.016). These results suggest that gaseous nitrogen export, particularly N2O emissions, is a greater form of nitrogen loss in arid systems than is currently assumed. This potential for high nitrogen emissions and the capacity for anthropogenic nitrogen deposition to increase these emissions present serious implications for local air quality and significant soil feedbacks to climate change.

  3. Sodium-promoted Pd/TiO2 for catalytic oxidation of formaldehyde at ambient temperature.

    PubMed

    Zhang, Changbin; Li, Yaobin; Wang, Yafei; He, Hong

    2014-05-20

    Catalytic oxidation of formaldehyde (HCHO) to CO2 at ambient conditions is of great interest for indoor HCHO purification. Here, we report that sodium-doped Pd/TiO2 is a highly effective catalyst for the catalytic oxidation of HCHO at room temperature. It was observed that Na doping has a dramatic promotion effect on the Pd/TiO2 catalyst and that nearly 100% HCHO conversion could be achieved over the 2Na-Pd/TiO2 catalyst at a GHSV of 95000 h(-1) and HCHO inlet concentration of 140 ppm at 25 °C. The mechanism of the Na-promotion effect was investigated by using Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), CO chemisorption, Temperature-programmed reduction by H2 (H2-TPR), X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption of O2 (O2-TPD) methods. The results showed that Na species addition can induce and further stabilize a negatively charged and well-dispersed Pd species, which then facilitates the activation of H2O and chemisorbed oxygen, therefore resulting in the high performance of the 2Na-Pd/TiO2 catalyst for the ambient HCHO destruction.

  4. Synthesis and photo-catalytic property of TiO2 nanotube arrays/ZnS

    NASA Astrophysics Data System (ADS)

    Kong, Junhan; Liu, Zhe; Xiong, Yehan; Liu, Zhanhong; Wang, Yongqian

    2017-04-01

    TiO2 nanotube arrays/ZnS (TNAs/ZnS) nanocomposites were synthesized successfully via anodic oxidation method and hydrothermal method as well. In this study, field emission scanning electron microscopy equipped with energy-dispersive spectroscopy (EDS) was used to monitor the morphological features and elemental composition of the samples. UV-Vis absorption spectra showed the absorption performance in both UV and visible light regions. In addition, the photo-catalytic activity of the samples was measured by the photo-degradation rate of methylene blue. From the result, we could notice that the morphology of the samples would change gradually when the amounts of zinc source and sulfur source changed, and the hydrothermal temperature was one of the significant factors which influenced the morphology. EDS spectra showed the existence of zinc and sulfur elements. Photo-catalytic activity test indicated that the photo-degradation rate of MB rises up to 91.6% after 240 min. Furthermore, there existed an expected relationship between the photo-degradation rate and the amounts of zinc source and sulfur source. UV-Vis absorption spectra of the samples also verified the result of photo-catalytic activity test.

  5. Asphaltene cracking in catalytic hydrotreating of heavy oils. 2. study of changes in asphaltene structure during catalytic hydroprocessing

    SciTech Connect

    Sachio, A.; Chisato, T.; Shinichi, N.; Yoshimi, S.

    1983-04-01

    Characteristics in catalytic conversion of asphaltenes in petroleum heavy residues were studied in the hydrotreating process. A Boscan crude, an Athabasca bitumen, and a Khafji vacuum residue were tested as typical feedstocks. Various analyses were made to obtain the properties of asphaltenes before and after the reaction, e.g., changes of heteroatoms such as sulfur and metals, and decreases of molecular weight. The characteristic changes of asphaltene molecules were also investigated by electron spin resonance (ESR) and X-ray analyses. The association and coordination of vanadyl in asphaltenes were studied by the temperature dependence on the ESR spectra, and the sizes of the stacked crystallites and the aggregated asphaltene micelles were measured with X-ray diffraction and small-angle scattering. In the asphaltene cracking mechanism, it was clarified that the main reactions were the destruction of asphaltene micelles caused by vanadium removal and the depolymerization of asphaltene molecules by removal of heteroatoms such as sulfur.

  6. Suppressed N2O formation during NH3 selective catalytic reduction using vanadium on zeolitic microporous TiO2

    PubMed Central

    Lee, Seung Gwan; Lee, Hyun Jeong; Song, Inhak; Youn, Seunghee; Kim, Do Heui; Cho, Sung June

    2015-01-01

    Emission of N2O from mobile and off-road engine is now being currently regulated because of its high impact compared to that of CO2, thereby implying that N2O formation from the exhaust gas after-treatment system should be suppressed. Selective catalytic reduction using vanadium supported TiO2 catalyst in mobile and off-road engine has been considered to be major source for N2O emission in the system. Here we have demonstrated that vanadium catalyst supported on zeolitic microporous TiO2 obtained from the hydrothermal reaction of bulk TiO2 at 400 K in the presence of LiOH suppresses significantly the N2O emission compared to conventional VOx/TiO2 catalyst, while maintaining the excellent NOx reduction, which was ascribed to the location of VOx domain in the micropore of TiO2, resulting in the strong metal support interaction. The use of zeolitic microporous TiO2 provides a new way of preparing SCR catalyst with a high thermal stability and superior catalytic performance. It can be also extended further to the other catalytic system employing TiO2-based substrate. PMID:26235671

  7. Suppressed N2O formation during NH3 selective catalytic reduction using vanadium on zeolitic microporous TiO2.

    PubMed

    Lee, Seung Gwan; Lee, Hyun Jeong; Song, Inhak; Youn, Seunghee; Kim, Do Heui; Cho, Sung June

    2015-08-03

    Emission of N2O from mobile and off-road engine is now being currently regulated because of its high impact compared to that of CO2, thereby implying that N2O formation from the exhaust gas after-treatment system should be suppressed. Selective catalytic reduction using vanadium supported TiO2 catalyst in mobile and off-road engine has been considered to be major source for N2O emission in the system. Here we have demonstrated that vanadium catalyst supported on zeolitic microporous TiO2 obtained from the hydrothermal reaction of bulk TiO2 at 400 K in the presence of LiOH suppresses significantly the N2O emission compared to conventional VOx/TiO2 catalyst, while maintaining the excellent NOx reduction, which was ascribed to the location of VOx domain in the micropore of TiO2, resulting in the strong metal support interaction. The use of zeolitic microporous TiO2 provides a new way of preparing SCR catalyst with a high thermal stability and superior catalytic performance. It can be also extended further to the other catalytic system employing TiO2-based substrate.

  8. Suppressed N2O formation during NH3 selective catalytic reduction using vanadium on zeolitic microporous TiO2

    NASA Astrophysics Data System (ADS)

    Lee, Seung Gwan; Lee, Hyun Jeong; Song, Inhak; Youn, Seunghee; Kim, Do Heui; Cho, Sung June

    2015-08-01

    Emission of N2O from mobile and off-road engine is now being currently regulated because of its high impact compared to that of CO2, thereby implying that N2O formation from the exhaust gas after-treatment system should be suppressed. Selective catalytic reduction using vanadium supported TiO2 catalyst in mobile and off-road engine has been considered to be major source for N2O emission in the system. Here we have demonstrated that vanadium catalyst supported on zeolitic microporous TiO2 obtained from the hydrothermal reaction of bulk TiO2 at 400 K in the presence of LiOH suppresses significantly the N2O emission compared to conventional VOx/TiO2 catalyst, while maintaining the excellent NOx reduction, which was ascribed to the location of VOx domain in the micropore of TiO2, resulting in the strong metal support interaction. The use of zeolitic microporous TiO2 provides a new way of preparing SCR catalyst with a high thermal stability and superior catalytic performance. It can be also extended further to the other catalytic system employing TiO2-based substrate.

  9. Removing dye rhodamine B from aqueous medium via wet peroxidation with V-MCM-41 and H2O2.

    PubMed

    Wu, Deyong; Long, Mingce; Chen, Chao; Wu, Yahui; Cai, Weimin; Zhou, Jiangya; Ding, Dawei

    2009-01-01

    A new heterogeneous Fenton-like system, consisting of V-MCM-41 catalyst and hydrogen peroxide, was proved to be effective in removing recalcitrant dye Rhodamine B (RhB) in aqueous solutions. V-MCM-41 was prepared following a direct hydrothermal procedure with tetraethyl silicate and ammonium metavanadate as precursor. The mesoporous structure has been characterized by XRD, and the specific surface area was determined as x m(2) g(-1) according to BET method. The catalytic reaction can proceed in a relatively wide pH range from acidic to alkaline. And the visible light irradiation cannot promote the reaction process. In addition, the mechanism implication for V-MCM-41 as a Fenton-like catalyst has been discussed.

  10. Switchable catalytic DNA catenanes.

    PubMed

    Hu, Lianzhe; Lu, Chun-Hua; Willner, Itamar

    2015-03-11

    Two-ring interlocked DNA catenanes are synthesized and characterized. The supramolecular catenanes show switchable cyclic catalytic properties. In one system, the catenane structure is switched between a hemin/G-quadruplex catalytic structure and a catalytically inactive state. In the second catenane structure the catenane is switched between a catalytically active Mg(2+)-dependent DNAzyme-containing catenane and an inactive catenane state. In the third system, the interlocked catenane structure is switched between two distinct catalytic structures that include the Mg(2+)- and the Zn(2+)-dependent DNAzymes.

  11. Oscillatory behaviour of catalytic properties, structure and temperature during the catalytic partial oxidation of methane on Pd/Al(2)O(3).

    PubMed

    Kimmerle, Bertram; Baiker, Alfons; Grunwaldt, Jan-Dierk

    2010-03-14

    Pd/Al(2)O(3) catalysts showed an oscillatory behaviour during the catalytic partial oxidation (CPO) of methane, which was investigated simultaneously by IR-thermography, X-ray absorption spectroscopy, and online mass-spectrometry to correlate the temperature, state of the catalyst and catalytic performance. The following stages were observed: (i) build-up of a temperature maximum in the first half of the catalyst bed, (ii) reduction of palladium in the end zone of the catalyst bed with a front moving toward the entrance zone, (iii) strong hot spot formation accompanied by reduction of palladium due to self-reduction leading to extinction of the process. The latter was the key driver for the oscillations and thus gave additional insight into the mechanism of partial methane oxidation.

  12. Heterogeneous catalytic degradation of phenolic substrates: catalysts activity.

    PubMed

    Liotta, L F; Gruttadauria, M; Di Carlo, G; Perrini, G; Librando, V

    2009-03-15

    This review article explored the catalytic degradation of phenol and some phenols derivates by means of advanced oxidation processes (AOPs). Among them, only the heterogeneous catalyzed processes based on catalytic wet peroxide oxidation, catalytic ozonation and catalytic wet oxidation were reviewed. Also selected recent examples about heterogeneous photocatalytic AOPs will be presented. In details, the present review contains: (i) data concerning catalytic wet peroxide oxidation of phenolic compounds over metal-exchanged zeolites, hydrotalcites, metal-exchanged clays and resins. (ii) Use of cobalt-based catalysts, hydrotalcite-like compounds, active carbons in the catalytic ozonation process. (iii) Activity of transition metal oxides, active carbons and supported noble metals catalysts in the catalytic wet oxidation of phenol and acetic acid. The most relevant results in terms of catalytic activity for each class of catalysts were reported.

  13. In situ transesterification of highly wet microalgae using hydrochloric acid.

    PubMed

    Kim, Bora; Im, Hanjin; Lee, Jae W

    2015-06-01

    This study addresses in situ transesterification of highly wet microalgae with hydrochloric acid (HCl) as a catalyst. In situ transesterification was performed by heating the mixture of wet algal cells, HCl, methanol, and solvent in one pot, resulting in the fatty acid methyl ester (FAME) yield over 90% at 95°C. The effects of reaction variables of temperature, amounts of catalyst, reactant, and solvent, and type of solvents on the yield were investigated. Compared with the catalytic effect of H2SO4, in situ transesterification using HCl has benefits of being less affected by moisture levels that are as high as or above 80%, and requiring less amounts of catalyst and solvent. For an equimolar amount of catalyst, HCl showed 15wt.% higher FAME yield than H2SO4. This in situ transesterification using HCl as a catalyst would help to realize a feasible way to produce biodiesel from wet microalgae. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. Catalytic Transfer Hydrogenation of Furfural to 2-Methylfuran and 2-Methyltetrahydrofuran over Bimetallic Copper-Palladium Catalysts.

    PubMed

    Chang, Xin; Liu, An-Feng; Cai, Bo; Luo, Jin-Yue; Pan, Hui; Huang, Yao-Bing

    2016-12-08

    The catalytic transfer hydrogenation of furfural to the fuel additives 2-methylfuran (2-MF) and 2-methyltetrahydrofuran (2-MTHF) was investigated over various bimetallic catalysts in the presence of the hydrogen donor 2-propanol. Of all the as-prepared catalysts, bimetallic Cu-Pd catalysts showed the highest catalytic activities towards the formation of 2-MF and 2-MTHF with a total yield of up to 83.9 % yield at 220 °C in 4 h. By modifying the Pd ratios in the Cu-Pd catalyst, 2-MF or 2-MTHF could be obtained selectively as the prevailing product. The other reaction conditions also had a great influence on the product distribution. Mechanistic studies by reaction monitoring and intermediate conversion revealed that the reaction proceeded mainly through the hydrogenation of furfural to furfuryl alcohol, which was followed by deoxygenation to 2-MF in parallel to deoxygenation/ring hydrogenation to 2-MTHF. Finally, the catalyst showed a high reactivity and stability in five catalyst recycling runs, which represents a significant step forward toward the catalytic transfer hydrogenation of furfural.

  15. Fluorine- and Nitrogen-Codoped MoS2 with a Catalytically Active Basal Plane.

    PubMed

    Wang, Yuanzhe; Liu, Shanshan; Hao, Xianfeng; Zhou, Junshuang; Song, Dandan; Wang, Dong; Hou, Li; Gao, Faming

    2017-08-23

    Two-dimensional molybdenum disulfide (2D MoS2) has drawn persistent interests as one of the most promising alternatives to Pt catalysts for the hydrogen evolution reaction (HER). It is generally accepted that the edge sites of 2D MoS2 are catalytically active but the basal planes are inert. Activating the MoS2 basal plane is an obvious strategy to enhance the HER activity of this material. However, few approaches have sought to activate the basal plane. Here, for the first time, we demonstrate that the inert basal planes can be activated via the synergistic effects of nitrogen and fluorine codoping. Our first-principles calculations reveal that nitrogen in the basal plane of the fluorine- and nitrogen-codoped MoS2 (NF-MoS2) can act as a new active and further tuneable catalytic site. The as-prepared NF-MoS2 catalyst exhibited an enormously enhanced HER activity compared to that of pure MoS2 and N-doped MoS2 due to the chemical codoping effect. This work will pave a novel pathway for enhancing the HER activity using the synergistic effects of chemical codoping.

  16. Fabrication of Ag/TiO2 nanotube array with enhanced photo-catalytic degradation of aqueous organic pollutant

    NASA Astrophysics Data System (ADS)

    Ma, Jie; Yang, Mingxuan; Sun, Yiran; Li, Chenlu; Li, Qiang; Gao, Fangfang; Yu, Fei; Chen, Junhong

    2014-04-01

    In this paper, the fabrication of Ag/TiO2 nanotube arrays and their photo-catalytic activity have been studied. The SEM, TEM and XRD were performed to characterize the morphology and crystalline phase of the TiO2 nanotube array and Ag/TiO2 nanotube array. Ag nanoparticles with different loadings, which are aimed to suppress the electron-hole recombination so as to enhance the photo-catalytic oxidation efficiency, were systematically coated onto TiO2 nanotubes. The photo-catalytic activity of these nano-materials was evaluated by the degradation of two different pollutants: methyl orange and glyphosate. The effects of various parameters, such as the amount of the photo-catalyst, the illumination time, and pH value on the photo-catalytic oxidation activity, were studied.

  17. Identification of the Catalytic Mg2+ Ion in the HDV Ribozyme

    PubMed Central

    Chen, Ji; Ganguly, Abir; Miswan, Zulaika; Hammes-Schiffer, Sharon; Bevilacqua, Philip C.; Golden, Barbara L.

    2013-01-01

    The hepatitis delta virus ribozyme catalyzes an RNA cleavage reaction using a catalytic nucleobase and a divalent metal ion. The catalytic base, C75, serves as a general acid and has a pKa shifted towards neutrality. Less is known about the role of metal ions in the mechanism. A recent crystal structure of the pre-cleavage ribozyme identified a Mg2+ ion that interacts through its partial hydration sphere with the G25•U20 reverse wobble. In addition, this Mg2+ ion is in position to directly coordinate the nucleophile, the 2’-hydroxyl of U(-1), suggesting it can serve as a Lewis acid to facilitate deprotonation of the 2’-hydroxyl. To test the role of the active site Mg2+ ion, we replaced the G25•U20 reverse wobble with an isosteric A25•C20 reverse wobble. This change was found to significantly reduce the negative potential at the active site, as supported by electrostatics calculations, suggesting that active site Mg2+ binding could be adversely affected by the mutation. Kinetic analysis and molecular dynamics of the A25•C20 double mutant suggest that this variant stably folds into an active structure. However, pH-rate profiles of the double mutant are inverted relative to the profiles for wild-type ribozyme, suggesting that the A25•C20 double mutant has lost the active site metal ion. Overall, these studies support a model wherein the partially hydrated Mg2+ positioned at the G25•U20 reverse wobble is catalytic and could serve as a Lewis acid, a Brønsted base, or both to facilitate deprotonation of the nucleophile. PMID:23311293

  18. Cwc2 and its human homologue RBM22 promote an active conformation of the spliceosome catalytic centre

    PubMed Central

    Rasche, Nicolas; Dybkov, Olexandr; Schmitzová, Jana; Akyildiz, Berktan; Fabrizio, Patrizia; Lührmann, Reinhard

    2012-01-01

    RNA-structural elements play key roles in pre-mRNA splicing catalysis; yet, the formation of catalytically competent RNA structures requires the assistance of spliceosomal proteins. We show that the S. cerevisiae Cwc2 protein functions prior to step 1 of splicing, and it is not required for the Prp2-mediated spliceosome remodelling that generates the catalytically active B* complex, suggesting that Cwc2 plays a more sophisticated role in the generation of a functional catalytic centre. In active spliceosomes, Cwc2 contacts catalytically important RNA elements, including the U6 internal stem-loop (ISL), and regions of U6 and the pre-mRNA intron near the 5′ splice site, placing Cwc2 at/near the spliceosome's catalytic centre. These interactions are evolutionarily conserved, as shown by studies with Cwc2's human counterpart RBM22, indicating that Cwc2/RBM22–RNA contacts are functionally important. We propose that Cwc2 induces an active conformation of the spliceosome's catalytic RNA elements. Thus, the function of RNA–RNA tertiary interactions within group II introns, namely to induce an active conformation of domain V, may be fulfilled by proteins that contact the functionally analogous U6-ISL, within the spliceosome. PMID:22246180

  19. The Synthesis and Characterization of Multifunctional Titania-based Materials for the Photo/Thermal Catalytic Reduction of CO2

    NASA Astrophysics Data System (ADS)

    Schwartzenberg, Kevin

    The work presented in this dissertation is aimed at improving our understanding of the fundamental processes required for the photocatalytic reduction of CO2. A QCM reactor system for measuring CO2 adsorption under a range of conditions was designed, constructed, and characterized. Measurements on catalyst films revealed sufficient sensitivity to detect CO2 adsorption on the order of 0.1 molecules/nm2. Adsorption experiments were repeatable across multiple measurements for the same film. However, variation across multiple films prepared using the same mass of catalyst highlights the large contribution of surface roughness to frequency response and the importance of uniform, reproducible film preparation. The design of a multifunctional photo/thermal catalyst was explored through the concept of MnOx-TiO2 composites with thermally generated oxygen vacancies as the active sites for CO2 activation. MnOx-TiO 2 were prepared by incipient wetness impregnation of titania supports with one of two Mn precursors, and were characterized and screened for catalytic activity. The results were compared with predictions from theoretical modeling studies. Through TPR, UV-vis spectroscopy, and XANES, it was observed that a Mn(NO 3)2•4H2O precursor led to bulk-like domains of MnOx whereas a Mn(CH3COO)2•4H2O precursor led to a dispersed surface oxide. This precursor effect was less pronounced on rutile than on anatase support. As predicted by theory, the MnOx-TiO 2 exhibited the reversible generation of oxygen vacancies at mild temperatures (< 300°C) and a red shift in the band gap for anatase-supported composites. A similar red shift was not observed for rutile-supported materials. In screening reactions, however, neither CO nor other products were detected by GC. In-situ FTIR experiments also failed to show evidence of nonvolatile CO2 reduction products. However, several carbonate, bicarbonate, and carboxylate species were observed, confirming the interaction of CO 2 with oxygen

  20. Site-directed mutagenesis of potential catalytic residues in 1H-3-hydroxy-4-oxoquinoline 2,4-dioxygenase, and hypothesis on the catalytic mechanism of 2,4-dioxygenolytic ring cleavage.

    PubMed

    Fischer, F; Fetzner, S

    2000-09-01

    1H-3-Hydroxy-4-oxoquinoline 2,4-dioxygenase (Qdo) is a cofactor-free dioxygenase proposed to belong to the alpha/beta hydrolase fold superfamily of enzymes. Alpha/beta Hydrolases contain a highly conserved catalytic triad (nucleophile-acidic residue-histidine). We previously identified a corresponding catalytically essential histidine residue in Qdo. However, as shown by amino acid replacements through site-directed mutagenesis, nucleophilic and acidic residues of Qdo considered as possible triad residues were not absolutely required for activity. This suggests that Qdo does not contain the canonical catalytic triad of the alpha/beta hydrolase fold enzymes. Some radical trapping agents affected the Qdo-catalyzed reaction. A hypothetical mechanism of Qdo-catalyzed dioxygenation of 1H-3-hydroxy-4-oxoquinoline is compared with the dioxygenation of FMNH2 catalyzed by bacterial luciferase, which also uses a histidine residue as catalytic base.

  1. Catalytic ozonation for degradation of 2, 4, 6-trichloroanisole in drinking water in the presence of gamma-AlOOH.

    PubMed

    Qi, Fei; Xu, Bingbing; Chen, Zhonglin; Ma, Jun

    2009-06-01

    Results show that catalytic ozonation with gamma-AlOOH can substantially enhance the removal effectiveness of 2, 4, 6-trichloroanisole (TCA) in drinking water. Scavenging of radicals tests reveals that the improved 2, 4, 6-trichloroanisole degradation is due to the enhanced generation of hydroxyl radicals. The uncharged surface hydroxyl groups on gamma-AlOOH in water can induce aqueous ozone decomposition to generate hydroxyl radicals. The catalytic activity of gamma-AlOOH decreased as thermal treatment temperature increased.

  2. Swelled plastics in supercritical CO2 as media for stabilization of metal nanoparticles and for catalytic hydrogenation.

    PubMed

    Ohde, Hiroyuki; Ohde, Mariko; Wai, Chien M

    2004-04-21

    Swelled plastics in supercritical carbon dioxide provide unique environments for stabilizing palladium and rhodium nanoparticles and for catalytic hydrogenation. Complete hydrogenation of benzene to cyclohexane can be achieved in 10 minutes using the plastic stabilized Rh nanoparticles at 50 degrees C in supercritical CO(2). High efficiency, reusability, and rapid separation of products are some advantages of the plastic stabilized metal nanoparticles for catalytic hydrogenation in supercritical CO(2).

  3. Wet chemically prepared rutile TiO2(110) and TiO2(011): Substrate preparation for surface studies under non-UHV conditions

    NASA Astrophysics Data System (ADS)

    Ahmed, M. H. M.; Lydiatt, F. P.; Chekulaev, D.; Wincott, P. L.; Vaughan, D. J.; Jang, J. H.; Baldelli, S.; Thomas, A. G.; Walters, W. S.; Lindsay, R.

    2014-12-01

    A procedure for wet chemical preparation of TiO2 single crystal surfaces is detailed. The potential of this procedure is demonstrated through application to rutile-TiO2(110) and rutile-TiO2(011) substrates. Characterisation with atomic force microscopy, low energy electron diffraction, auger electron spectroscopy, and vibrational sum frequency spectroscopy indicates that flat, well-ordered, carbon-free surfaces can be generated. Notably, in contrast to the (2 × 1) low energy electron diffraction pattern observed for TiO2(011) prepared in ultra-high vacuum, wet chemical preparation results in a (4 × 1) unit cell; wet chemically prepared TiO2(110) displays an unreconstructed (1 × 1) surface.

  4. The AMP-activated protein kinase alpha2 catalytic subunit controls whole-body insulin sensitivity.

    PubMed

    Viollet, Benoit; Andreelli, Fabrizio; Jørgensen, Sebastian B; Perrin, Christophe; Geloen, Alain; Flamez, Daisy; Mu, James; Lenzner, Claudia; Baud, Olivier; Bennoun, Myriam; Gomas, Emmanuel; Nicolas, Gaël; Wojtaszewski, Jørgen F P; Kahn, Axel; Carling, David; Schuit, Frans C; Birnbaum, Morris J; Richter, Erik A; Burcelin, Rémy; Vaulont, Sophie

    2003-01-01

    AMP-activated protein kinase (AMPK) is viewed as a fuel sensor for glucose and lipid metabolism. To better understand the physiological role of AMPK, we generated a knockout mouse model in which the AMPKalpha2 catalytic subunit gene was inactivated. AMPKalpha2(-/-) mice presented high glucose levels in the fed period and during an oral glucose challenge associated with low insulin plasma levels. However, in isolated AMPKalpha2(-/-) pancreatic islets, glucose- and L-arginine-stimulated insulin secretion were not affected. AMPKalpha2(-/-) mice have reduced insulin-stimulated whole-body glucose utilization and muscle glycogen synthesis rates assessed in vivo by the hyperinsulinemic euglycemic clamp technique. Surprisingly, both parameters were not altered in mice expressing a dominant-negative mutant of AMPK in skeletal muscle. Furthermore, glucose transport was normal in incubated isolated AMPKalpha2(-/-) muscles. These data indicate that AMPKalpha2 in tissues other than skeletal muscles regulates insulin action. Concordantly, we found an increased daily urinary catecholamine excretion in AMPKalpha2(-/-) mice, suggesting altered function of the autonomic nervous system that could explain both the impaired insulin secretion and insulin sensitivity observed in vivo. Therefore, extramuscular AMPKalpha2 catalytic subunit is important for whole-body insulin action in vivo, probably through modulation of sympathetic nervous activity.

  5. The AMP-activated protein kinase α2 catalytic subunit controls whole-body insulin sensitivity

    PubMed Central

    Viollet, Benoit; Andreelli, Fabrizio; Jørgensen, Sebastian B.; Perrin, Christophe; Geloen, Alain; Flamez, Daisy; Mu, James; Lenzner, Claudia; Baud, Olivier; Bennoun, Myriam; Gomas, Emmanuel; Nicolas, Gaël; Wojtaszewski, Jørgen F.P.; Kahn, Axel; Carling, David; Schuit, Frans C.; Birnbaum, Morris J.; Richter, Erik A.; Burcelin, Rémy; Vaulont, Sophie

    2003-01-01

    AMP-activated protein kinase (AMPK) is viewed as a fuel sensor for glucose and lipid metabolism. To better understand the physiological role of AMPK, we generated a knockout mouse model in which the AMPKα2 catalytic subunit gene was inactivated. AMPKα2–/– mice presented high glucose levels in the fed period and during an oral glucose challenge associated with low insulin plasma levels. However, in isolated AMPKα2–/– pancreatic islets, glucose- and L-arginine–stimulated insulin secretion were not affected. AMPKα2–/– mice have reduced insulin-stimulated whole-body glucose utilization and muscle glycogen synthesis rates assessed in vivo by the hyperinsulinemic euglycemic clamp technique. Surprisingly, both parameters were not altered in mice expressing a dominant-negative mutant of AMPK in skeletal muscle. Furthermore, glucose transport was normal in incubated isolated AMPKα2–/– muscles. These data indicate that AMPKα2 in tissues other than skeletal muscles regulates insulin action. Concordantly, we found an increased daily urinary catecholamine excretion in AMPKα2–/– mice, suggesting altered function of the autonomic nervous system that could explain both the impaired insulin secretion and insulin sensitivity observed in vivo. Therefore, extramuscular AMPKα2 catalytic subunit is important for whole-body insulin action in vivo, probably through modulation of sympathetic nervous activity. PMID:12511592

  6. Synthesis of chitosan supported palladium nanoparticles and its catalytic activity towards 2-nitrophenol reduction

    SciTech Connect

    Dhanavel, S.; Nivethaa, E. A. K.; Esther, G.; Stephen, A.; Narayanan, V.

    2016-05-23

    Chitosan supported Palladium nanoparticles were synthesized by a simple cost effective chemical reduction method using NaBH{sub 4}. The prepared nanocomposite was characterized by X-Ray diffraction analysis, FESEM and Energy dispersive spectroscopy analysis of X-rays (EDAX). The catalytic performance of the nanocomposite was evaluated on the reduction of 2-Nitrophenol to the 2-Amino phenol with rate constant 1.08 × 10{sup −3} S{sup −1} by NaBH{sub 4} using Spectrophotometer.

  7. High Resolution Crystal Structure of the Catalytic Domain of ADAMTS-5 (Aggrecanase-2)

    SciTech Connect

    Shieh, Huey-Sheng; Mathis, Karl J.; Williams, Jennifer M.; Hills, Robert L.; Wiese, Joe F.; Benson, Timothy E.; Kiefer, James R.; Marino, Margaret H.; Carroll, Jeffery N.; Leone, Joseph W.; Malfait, Anne-Marie; Arner, Elizabeth C.; Tortorella, Micky D.; Tomasselli, Alfredo

    2008-06-30

    Aggrecanase-2 (a disintegrin and metalloproteinase with thrombospondin motifs-5 (ADAMTS-5)), a member of the ADAMTS protein family, is critically involved in arthritic diseases because of its direct role in cleaving the cartilage component aggrecan. The catalytic domain of aggrecanase-2 has been refolded, purified, and crystallized, and its three-dimensional structure determined to 1.4{angstrom} resolution in the presence of an inhibitor. A high resolution structure of an ADAMTS/aggrecanase protein provides an opportunity for the development of therapeutics to treat osteoarthritis.

  8. Catalytic role of carbons in methane decomposition for CO- and CO2-free hydrogen generation

    NASA Astrophysics Data System (ADS)

    Huang, Liping; Santiso, Erik E.; Nardelli, Marco Buongiorno; Gubbins, Keith E.

    2008-06-01

    Decomposition of methane is an environmentally attractive approach to CO- and CO2-free hydrogen production. Using first principles calculations at the density functional theory level, our studies demonstrate that the defective carbons can be used as catalysts for methane decomposition, without the need for other catalysts, such as transition metals or oxides, and the catalytic sites can be regenerated by the deposition of carbon decomposed from methane, to make the hydrogen production a continuous process. Additionally, since no other gases are produced in the process, the cost of CO2 sequestration and hydrogen purification from CO contamination will be dramatically reduced.

  9. Catalytic mechanism and kinase interactions of ABA-signaling PP2C phosphatases.

    PubMed

    Zhou, X Edward; Soon, Fen-Fen; Ng, Ley-Moy; Kovach, Amanda; Suino-Powell, Kelly M; Li, Jun; Yong, Eu-Leong; Zhu, Jian-Kang; Xu, H Eric; Melcher, Karsten

    2012-05-01

    Abscisic acid (ABA) is an essential hormone that controls plant growth, development and responses to abiotic stresses. ABA signaling is mediated by type 2C protein phosphatases (PP2Cs), including HAB1 and ABI2, which inhibit stress-activated SnRK2 kinases and whose activity is regulated by ABA and ABA receptors. Based on biochemical data and our previously determined crystal structures of ABI2 and the SnRK2.6-HAB1 complex, we present the catalytic mechanism of PP2C and provide new insight into PP2C-SnRK2 interactions and possible roles of other SnRK2 kinases in ABA signaling.

  10. Relationship between Surface Chemistry and Catalytic Performance of Mesoporous γ-Al2O3 Supported VOX Catalyst in Catalytic Dehydrogenation of Propane.

    PubMed

    Bai, Peng; Ma, Zhipeng; Li, Tingting; Tian, Yupeng; Zhang, Zhanquan; Zhong, Ziyi; Xing, Wei; Wu, Pingping; Liu, Xinmei; Yan, Zifeng

    2016-10-05

    Mesoporous γ-Al2O3 was synthesized via a cation-anion double hydrolysis approach (CADH). The synthesized mesoporous alumina displayed a relatively high surface area, a large pore volume and a narrow pore size distribution. By applying the mesoporous alumina as a support, supported vanadium catalysts were prepared and evaluated in the dehydrogenation of propane, exhibiting a superior catalytic performance over that supported on a commercial alumina. Materials were characterized with a variety of techniques such as X-ray diffraction, X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy, (51)V magnetic angle spinning nuclear magnetic resonance, Raman spectroscopy, Fourier transformed infrared spectroscopy of pyridine adsorption and thermogravimetric-differential thermal analysis. The correlated structure-performance relationship of catalysts reveals that a higher crystallization temperature endows mesoporous alumina materials with more surface acid sites, favoring the formation of polymerized VOX species, which are more active than isolated ones in the propane dehydrogenation, resulting in a better catalytic performance. The established relationship between surface chemistry and catalytic performance of supported VOX catalysts suggests that a superior vanadium catalyst for propane dehydrogenation could be achieved by rationally enriching the concentration of polymeric VOX species on the catalyst, which can be realized by tuning the surface acidity of alumina support.

  11. Synthesis, structural properties and catalytic activity of MgO-SnO2 nanocatalysts

    NASA Astrophysics Data System (ADS)

    Perveen, Hina; Farrukh, Muhammad Akhyar; Khaleeq-ur-Rahman, Muhammad; Munir, Badar; Tahir, Muhammad Ashraf

    2015-01-01

    Surfactant controlled synthesis of magnesium oxide-tin oxide (MgO-SnO2) nanocatalysts was carried out via the hydrothermal method. Concentration of sodium dodecyl sulfate (SDS) was varied while all other reaction conditions were kept constant same for this purpose. Furthermore, MgO-SnO2 nanocatalysts were also prepared by changing the precursor's concentration. These precursors are magnesium nitrate Mg(NO3)2 · 6H2O and tin chloride (SnCl4 · 5H2O). The influence of these reaction parameters on the sizes and morphology of the nanocatalysts were studied by using Fourier transform infrared (FTIR) spectroscopy, Scanning electron microscopy-Energy dispersive X-ray (SEM-EDX), Powder X-ray diffraction (XRD), Transmission electron microscopy and Thermo gravimetric analysis (TGA). The catalytic efficiency of MgO-SnO2 was checked against 2,4-dinitrophenylhydrazine (DNPH), which is an explosive compound. The nanocatalysts were found as a good catalyst to degrade the DNPH. Catalytic activity of nanocatalysts was observed up to 19.13% for the degradation DNPH by using UV-spectrophotometer.

  12. Catalytic combustion of dimethyl ether over α-MnO2 nanostructures with different morphologies

    NASA Astrophysics Data System (ADS)

    Cheng, Gao; Yu, Lin; He, Binbin; Sun, Ming; Zhang, Bentian; Ye, Wenjin; Lan, Bang

    2017-07-01

    Herein, α-MnO2 catalysts with three well-defined morphologies (nanorod, ultra-long nanowire and microsphere) were rational designed and prepared by the hydrothermal route, and their catalytic activities were evaluated for the dimethyl ether (DME) combustion. These nanostructured α-MnO2 catalysts were characterized in detail by various analytical techniques: XRD, FESEM, TEM, BET, XPS and H2-TPR. As a result, the α-MnO2 nanorod exhibited the higher catalytic activity (T10 = 170 °C and T90 = 238 °C at WHSV = 30,000 mL g-1 h-1) than the other two α-MnO2 samples due to its larger specific surface area, higher average oxidation state of Mn, more abundant surface lattice oxygen (Olatt) species and higher reducibility, and there was no obvious decrease after the α-MnO2 nanorod was run for 50 h. Moreover, the transient response technique revealed that the Olatt species of the α-MnO2 nanorod should be the crucial role in the deep oxidation of DME.

  13. Ambipolar behavior in MoS2 field effect transistors by using catalytic oxidation

    NASA Astrophysics Data System (ADS)

    Choi, J. H.; Jang, H.-K.; Jin, J. E.; Shin, J. M.; Kim, D.-H.; Kim, G.-T.

    2016-10-01

    Modulation of electrical properties in MoS2 flakes is an attractive issue from the point of view of device applications. In this work, we demonstrate that an ambipolar behavior in MoS2 field effect transistors (FETs) can be easily obtained by heating MoS2 flakes under air atmosphere in the presence of cobalt oxide catalyst (MoS2 + O2 → MoOx + SOx). The catalytic oxidation of MoS2 flakes between source-drain electrodes resulted in lots of MoOx nanoparticles (NPs) on MoS2 flakes with thickness reduction from 64 nm to 17 nm. Consequently, N-type behavior of MoS2 FETs was converted into ambipolar transport characteristics by MoOx NPs which inject hole carriers to MoS2 flakes.

  14. Titanocene(III) complexes with 2-phosphinoaryloxide ligands for the catalytic dehydrogenation of dimethylamine borane.

    PubMed

    Klahn, Marcus; Hollmann, Dirk; Spannenberg, Anke; Brückner, Angelika; Beweries, Torsten

    2015-07-21

    A study of the dehydrogenation of dimethylamine borane using different titanocene(III) complexes with 2-phosphinoaryloxide ligands is presented. Complexes Cp2Ti(κ(2)-O, P-O-C6H4-PR2) (3a: R = i-Pr, 3b: R = Ph) (Cp = η(5)-cyclopentadienyl) and Cp*2Ti(κ(1)-O-O-C6H4-PR2) (5a: R = i-Pr, 5b: R = Ph) (Cp* = η(5)-pentamethylcyclopentadienyl) were prepared by reactions of the 2-phosphinophenol ligand with different titanocene sources and fully characterised. Their catalytic activity depends on the steric influence of the cyclopentadienyl ligand, the coordination mode of the 2-phosphinoaryloxide ligand and on the used solvent. Complex 3a showed a turnover number of 43.2 in the neat substrate after 24 hours. EPR investigations were used to elucidate the fate of the Ti(III) catalyst.

  15. Catalytic conversion of 1,2-dichlorobenzene using V2O5/TiO2 catalysts by a thermal decomposition process.

    PubMed

    Chin, Sungmin; Jurng, Jongsoo; Lee, Jae-Heon; Moon, Seung-Jae

    2009-05-01

    This study examined the catalytic oxidation of 1,2-dichlorobenzene on V(2)O(5)/TiO(2) nanoparticles. The V(2)O(5)/TiO(2) nanoparticles were synthesized by the thermal decomposition of vanadium oxytripropoxide and titanium tetraisopropoxide. The effects of the synthesis conditions, such as the synthesis temperature and precursor heating temperature, were investigated. The specific surface areas of V(2)O(5)/TiO(2) nanoparticles increased with increasing synthesis temperature and decreasing precursor heating temperature. The catalytic oxidation rate of the V(2)O(5)/TiO(2) catalyst formed by thermal decomposition process at a catalytic reaction temperature of 150 and 200 degrees C was 46% and 95%, respectively. As a result, it was concluded that the V(2)O(5)/TiO(2) catalysts synthesized by a thermal decomposition process showed good performance for 1,2-DCB decomposition at a lower temperature.

  16. Removal of Mn2+ from water by "aged" biofilter media: the role of catalytic oxides layers.

    PubMed

    Sahabi, Danladi Mahuta; Takeda, Minoru; Suzuki, Ichiro; Koizumi, Jun-ichi

    2009-02-01

    The present work was aimed at evaluating the surface coatings characteristics and autocatalytic manganese oxidation potentials of two groups of "aged" biofilter media. This refers to the anthracite filter media of a biological water treatment plant on which metal oxides and a biofilm have deposited on the surface of the filter media over long time of filtration. Duplicate samples of anthracite filter media were collected from each of the six filter wells in the plant and classified into two groups, based on their duration of operation, as 3-years filter media and 15-years filter media. Batch experiments showed that the 15-years filter media exhibited very high manganese sorption capacity and were less dependent on the microbial activity than the 3-years filter media. Results of the surface coatings analyses indicated that the biofilter materials is predominantly composed of variable layers of manganese and iron oxides, with microbial biomass contributing only about 3.5 and 1.4% of the dry weight of the surface coatings on the 3- and 15-years filter media respectively. Investigations onto the Mn2+ sorption by the lyophilized biofilter media showed that, the sorption kinetics on the catalytic oxides layers followed the pseudo-second-order kinetics model, thus suggesting chemisorption as the dominant mechanism of Mn2+ removal. This implied that manganese removal by these biofilters is mainly by adsorption of Mn2+ onto the iron and manganese (catalytic) oxides layers and autocatalytic oxidation. The present study has clearly linked Mn2+ oxidation to the catalytic oxides layers on the aged biofilter media.

  17. 3D Flower-like β-MnO2/Reduced Graphene Oxide Nanocomposites for Catalytic Ozonation of Dichloroacetic Acid

    NASA Astrophysics Data System (ADS)

    Li, Gang; Li, Kezheng; Liu, Aijuan; Yang, Ping; Du, Yukou; Zhu, Mingshan

    2017-03-01

    Considering the potential use of manganese oxide based nanocomposite in catalytic ozonation of water contaminant, we report unique three-dimensional (3D) nanoarchitectures composed of β-MnO2 and reduced graphene oxide (RGO) for catalytic ozonation of dichloroacetic acid (DCAA) from drinking water. The catalytic results show that the 3D β-MnO2/RGO nanocomposites (FMOG) can be used as efficient and stable ozonation catalysts to eliminate DCAA from water. The probable mechanism of catalytic ozonation was also proposed by detecting intermediates using gas chromatography-mass spectrometry. This result likely paves a facile avenue and initiates new opportunities for the exploration of heterogeneous catalysts for the removal of disinfection by-products from drinking water.

  18. 3D Flower-like β-MnO2/Reduced Graphene Oxide Nanocomposites for Catalytic Ozonation of Dichloroacetic Acid

    PubMed Central

    Li, Gang; Li, Kezheng; Liu, Aijuan; Yang, Ping; Du, Yukou; Zhu, Mingshan

    2017-01-01

    Considering the potential use of manganese oxide based nanocomposite in catalytic ozonation of water contaminant, we report unique three-dimensional (3D) nanoarchitectures composed of β-MnO2 and reduced graphene oxide (RGO) for catalytic ozonation of dichloroacetic acid (DCAA) from drinking water. The catalytic results show that the 3D β-MnO2/RGO nanocomposites (FMOG) can be used as efficient and stable ozonation catalysts to eliminate DCAA from water. The probable mechanism of catalytic ozonation was also proposed by detecting intermediates using gas chromatography-mass spectrometry. This result likely paves a facile avenue and initiates new opportunities for the exploration of heterogeneous catalysts for the removal of disinfection by-products from drinking water.

  19. Structure of the catalytic domain of the hepatitis C virus NS2-3 protease

    SciTech Connect

    Lorenz,I.; Marcotrigiano, J.; Dentzer, T.; Rice, C.

    2006-01-01

    Hepatitis C virus is a major global health problem affecting an estimated 170 million people worldwide. Chronic infection is common and can lead to cirrhosis and liver cancer. There is no vaccine available and current therapies have met with limited success. The viral RNA genome encodes a polyprotein that includes two proteases essential for virus replication. The NS2-3 protease mediates a single cleavage at the NS2/NS3 junction, whereas the NS3-4A protease cleaves at four downstream sites in the polyprotein. NS3-4A is characterized as a serine protease with a chymotrypsin-like fold, but the enzymatic mechanism of the NS2-3 protease remains unresolved. Here we report the crystal structure of the catalytic domain of the NS2-3 protease at 2.3 Angstroms resolution. The structure reveals a dimeric cysteine protease with two composite active sites. For each active site, the catalytic histidine and glutamate residues are contributed by one monomer, and the nucleophilic cysteine by the other. The carboxy-terminal residues remain coordinated in the two active sites, predicting an inactive post-cleavage form. Proteolysis through formation of a composite active site occurs in the context of the viral polyprotein expressed in mammalian cells. These features offer unexpected insights into polyprotein processing by hepatitis C virus and new opportunities for antiviral drug design.

  20. Catalytic Metallodrugs Based on the LaR2C Peptide Target HCV SLIV IRES RNA

    PubMed Central

    Ross, Martin James; Bradford, Seth S.; Cowan, J. A.

    2015-01-01

    Prior work has demonstrated the potential effectiveness of a new class of metallopeptides as catalytic metallodrugs that target HCV IRES SLIIb RNA (Cu-GGHYrFK, 1). Herein new catalytic metallodrugs (GGHKYKETDLLILFKDDYFAKKNEERK, 2; and GGHKYKETDL, 3) are described based on the LaR2C peptide that has been shown to bind to the SLIV HCV IRES domain. In vitro fluorescence assays yielded KD values ~10 μM for both peptides and reaction of the copper derivatives with SLIV RNA demonstrated initial rates comparable across different assays as well as displaying pseudo-Michaelis-Menten behavior. The sites of reaction and cleavage mechanisms were determined by MALDI-TOF mass spectrometry. The primary site of copper-promoted SLIV cleavage is shown to occur in the vicinity of the 5’-G17C18A19C20-3’ sequence that corresponds to a known binding site of the RM2 motif of the human La protein and has previously been reported to be important for viral translation. This domain also flanks the internal start codon (AUG). Both copper complexes also showed efficacy in an HCV replicon assay (IC50 = 0.75 μM for 2-Cu, and 2.17 μM for 3-Cu) and show potential for treatment of hepatitis C, complementing other marketed drugs by acting on a distinct therapeutic target by a novel mechanism of action. PMID:26583601

  1. Distribution and prediction of catalytic domains in 2-oxoglutarate dependent dioxygenases

    PubMed Central

    2012-01-01

    Background The 2-oxoglutarate dependent superfamily is a diverse group of non-haem dioxygenases, and is present in prokaryotes, eukaryotes, and archaea. The enzymes differ in substrate preference and reaction chemistry, a factor that precludes their classification by homology studies and electronic annotation schemes alone. In this work, I propose and explore the rationale of using substrates to classify structurally similar alpha-ketoglutarate dependent enzymes. Findings Differential catalysis in phylogenetic clades of 2-OG dependent enzymes, is determined by the interactions of a subset of active-site amino acids. Identifying these with existing computational methods is challenging and not feasible for all proteins. A clustering protocol based on validated mechanisms of catalysis of known molecules, in tandem with group specific hidden markov model profiles is able to differentiate and sequester these enzymes. Access to this repository is by a web server that compares user defined unknown sequences to these pre-defined profiles and outputs a list of predicted catalytic domains. The server is free and is accessible at the following URL ( http://comp-biol.theacms.in/H2OGpred.html). Conclusions The proposed stratification is a novel attempt at classifying and predicting 2-oxoglutarate dependent function. In addition, the server will provide researchers with a tool to compare their data to a comprehensive list of HMM profiles of catalytic domains. This work, will aid efforts by investigators to screen and characterize putative 2-OG dependent sequences. The profile database will be updated at regular intervals. PMID:22862831

  2. Effect of ZrO{sub 2}-doping of nanosized Fe{sub 2}O{sub 3}/MgO system on its structural, surface and catalytic properties

    SciTech Connect

    Hassan, Neveen A.; El-Molla, Sahar A.; Mohamed, Ghada M.; Fagal, Gehan A.

    2012-09-15

    Highlights: ► Preparation and characterization nano-sized ZrO{sub 2}-doped Fe{sub 2}O{sub 3}/MgO system. ► Pure and doped solids calcined at 500 and 700 °C are mesoporous adsorbents. ► ZrO{sub 2}-doping increased the lattice constant “a” of MgO lattice to an extent proportional to the amount of ZrO{sub 2} added. ► The catalytic activity in H{sub 2}O{sub 2} decomposition was found to increase as a function of dopant concentration. -- Abstract: Fe{sub 2}O{sub 3}/MgO system was prepared by wet impregnation method followed by treatment with different amounts of Zr-dopant salt then heating at 500 and 700 °C. The dopant concentrations were 0.48, 0.95 and 1.4 mol% ZrO{sub 2}. Pure and variously doped solids were characterized using XRD, N{sub 2}-adsorption isotherms carried out at −196 °C and catalytic decomposition of H{sub 2}O{sub 2} in aqueous solution at 25–35 °C. The results revealed that the nanosized MgO phase was only detected in the diffractograms of pure and doped solids calcined at 500 °C. Heating pure and doped solids at 700 °C produced nanosized MgFe{sub 2}O{sub 4} phase together with MgO phase. Pure and ZrO{sub 2}-doped solids calcined at 500 and 700 °C are mesoporous adsorbents. The doping process brought about a measurable decrease in the S{sub BET} of Fe{sub 2}O{sub 3}/MgO system with subsequent increase in its catalytic activity. The catalytic activity of the investigated system toward H{sub 2}O{sub 2} decomposition, expressed as reaction rate constant per unit surface area was found to increase as a function of dopant concentration. The maximum increase in the reaction rate constant per unit surface area measured for the reaction carried out at 30 °C attained 125% for the heavily doped samples. This significant increase was based on the catalytic activity of pure catalyst sample measured under the same conditions.

  3. Me2Zn-Mediated Catalytic Enantio- and Diastereoselective Addition of TosMIC to Ketones.

    PubMed

    Keeri, Abdul Raheem; Gualandi, Andrea; Mazzanti, Andrea; Lewinski, Janusz; Cozzi, Pier Giorgio

    2015-12-21

    The first catalytic asymmetric addition of TosMIC to unactivated ketones is presented. A combination of Me2Zn and aminoalcohol catalyst promoted the aldol addition/cyclization reaction to render oxazolines possessing a fully substituted stereocenter with excellent yields (up to 92%), high enantioselectivities (up to 96%), and complete diastereoselectivity. The chiral oxazolines were then used to give, after a straightforward acid hydrolysis, enantioenriched building blocks bearing tertiary alcohol motifs such as hydroxylaldehydes, hydroxylacids, and hydroxylesters without racemization. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Influence of He/O 2 atmospheric pressure plasma jet treatment on subsequent wet desizing of polyacrylate on PET fabrics

    NASA Astrophysics Data System (ADS)

    Li, Xuming; Lin, Jun; Qiu, Yiping

    2012-01-01

    The influence of He/O2 atmospheric pressure plasma jet (APPJ) treatment on subsequent wet desizing of polyacrylate on PET fabrics was studied in the present paper. Weight loss results indicated that the weight loss increased with an increase of plasma treatment time. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) showed an increased surface roughness after the plasma treatment. SEM also showed that the fiber surfaces were as clean as unsized fibers after 35 s treatment followed by NaHCO3 desizing. X-ray photoelectron spectroscopy (XPS) analysis indicated that oxygen-based functional groups increased for the plasma treated polyacrylate sized fabrics. The percent desizing ratio (PDR) results showed that more than 99% PDR was achieved after 65 s plasma treatment followed by a 5 min NaHCO3 desizing. Compared to conventional wet desizing, indicating that plasma treatment could significantly reduce desizing time.

  5. Transitions in Wetting Behavior Between Liquid Ag-CuO Alloys and Al2O3Substrates

    SciTech Connect

    Friant, Jared R.; Meier, Alan; Darsell, Jens T.; Weil, K. Scott; Rohrer, G.

    2012-02-24

    Reactive air brazing (RAB) is a method for joining ceramics with applications in high temperature technologies such as gas separation and solid oxide fuel cell (SOFC) components. An understanding of wetting behavior is critical for optimization of the brazing process. In the current study, the wetting behavior of Ag-CuO on Al2O3 was evaluated. Based on in-situ contact angle measurements, three regions of wetting behavior were identified in the composition range of 0 to 40 mol% CuO. The first transition, a 20° decrease between 2 mol% CuO and 4 mol% CuO, was attributed to the liquid composition miscibility gap, and the second, a 10° decrease between 10 mol% CuO and 20 mol% CuO, was hypothesized to be dominated by the formation of a reaction product. Small, discontinuous reaction regions were identified via electron probe microanalysis (EPMA) but could not be verified with X-ray photoelectron spectroscopy analysis (XPS).

  6. Enhanced catalytic performance for methane combustion of 3DOM CoFe2O4 by co-loading MnOx and Pd-Pt alloy nanoparticles

    NASA Astrophysics Data System (ADS)

    Li, Xiangyu; Liu, Yuxi; Deng, Jiguang; Xie, Shaohua; Zhao, Xingtian; Zhang, Yang; Zhang, Kunfeng; Arandiyan, Hamidreza; Guo, Guangsheng; Dai, Hongxing

    2017-05-01

    Three-dimensionally ordered macroporous (3DOM) CoFe2O4, zMnOx/3DOM CoFe2O4 (z = 4.99-12.30 wt%), and yPd-Pt/6.70 wt% MnOx/3DOM CoFe2O4 (y = 0.44-1.81 wt%; Pd/Pt molar ratio = 2.1-2.2) have been prepared using the polymethyl methacrylate microspheres-templating, incipient wetness impregnation, and bubble-assisted polyvinyl alcohol-protected reduction strategies, respectively. All of the samples were characterized by means of various techniques. Catalytic performance of the samples was measured for methane combustion. It is shown that the as-prepared samples exhibited a high-quality 3DOM structure (103 ± 20 nm in pore size) and a surface area of 19-28 m2/g, and the noble metal or alloy nanoparticles (NPs) with a size of 2.2-3.0 nm were uniformly dispersed on the macropore wall surface of 3DOM CoFe2O4. The loading of MnOx on CoFe2O4 gave rise to a slight increase in activity, however, the dispersion of Pd-Pt NPs on 6.70MnOx/3DOM CoFe2O4 significantly enhanced the catalytic performance, with the 1.81Pd2.1Pt/6.70MnOx/3DOM CoFe2O4 sample showing the highest activity (T10% = 255 °C, T50% = 301 °C, and T90% = 372 °C at a space velocity of 20,000 mL/(g h)). We believe that the excellent catalytic activity of 1.81Pd2.1Pt/6.70MnOx/3DOM CoFe2O4 was related to its well-dispersed Pd-Pt alloy NPs, high adsorbed oxygen species concentration, good low-temperature reducibility, and strong interaction between MnOx or Pd-Pt NPs and 3DOM CoFe2O4.

  7. One-pot, one-step, catalytic synthesis of 2,5-diformylfuran from fructose

    NASA Astrophysics Data System (ADS)

    Tao, Furong; Cui, Yuezhi; Yang, Pengfei; Gong, Yinghua

    2014-07-01

    MIL-101, a chromium-based metal-organic framework, is known for its very large pore size, large surface area and good stability. However, application of this material in catalysis is still limited. In this paper, a simple and practical catalytic method for the preparation 2,5-diformylfuran (DFF) directly from fructose was investigated. 5% Pd-V(3: 2)@MIL-101 was evaluated as a potential and effective catalyst for the direct oxidation of fructose. The amount of the catalyst, reaction time and temperature had a large effect on the reaction. At the optimized reaction conditions, when the reaction was conducted at 140°C for 600 min, 1 atm oxygen pressure, the yield of DFF reached 34%, fructose conversion was up to 100%. In our system, the main side products were 5-formyl-2-furancarboxylic acid (FFCA) and 2,5-furandicarboxylic acid (FDCA), which are the products of deep oxidation of DFF. This simple and effective catalytic system may be valuable to facilitate energy-efficient conversion of fructose into biofuels and platform chemicals.

  8. Kinetics of the catalytic reaction of 2,2-di-(chloromethyl)-1,3-propanediol with thionyl chloride

    SciTech Connect

    Bolotov, A.A.; V'yunov, K.A.

    1989-01-10

    The aim of this work was to determine the partial rate constants for the catalytic formation of 4,4-di(chloromethyl)trimethylene sulfite and to establish the controlling stage of the complex process. The choice of DMFA as catalyst during investigation of the quantitative relationships governing the substitution of the hydroxyl group by the chlorine atom was based on the fact that the reaction with triethylamine and pyridine takes place in a more complicated manner; the initially formed triethylamine and pyridine hydrochlorides accelerate substitution, i.e., autocatalysts by the reaction products is observed. The slowest stage of the complex catalytic process in the reaction of 2,2-di(chloromethyl)-1,3-propanediol with thionyl chloride in the presence of dimethylformamide is the reaction of the alcohol-catalyst donor-acceptor complex with the thionyl chloride.

  9. The DExD/H-box ATPase Prp2p destabilizes and proofreads the catalytic RNA core of the spliceosome

    PubMed Central

    Wlodaver, Alissa M.; Staley, Jonathan P.

    2014-01-01

    After undergoing massive RNA and protein rearrangements during assembly, the spliceosome undergoes a final, more subtle, ATP-dependent rearrangement that is essential for catalysis. This rearrangement requires the DEAH-box protein Prp2p, an RNA-dependent ATPase. Prp2p has been implicated in destabilizing interactions between the spliceosome and the protein complexes SF3 and RES, but a role for Prp2p in destabilizing RNA–RNA interactions has not been explored. Using directed molecular genetics in budding yeast, we have found that a cold-sensitive prp2 mutation is suppressed not only by mutations in SF3 and RES components but also by a range of mutations that disrupt the spliceosomal catalytic core element U2/U6 helix I, which is implicated in juxtaposing the 5′ splice site and branch site and in positioning metal ions for catalysis within the context of a putative catalytic triplex; indeed, mutations in this putative catalytic triplex also suppressed a prp2 mutation. Remarkably, we also found that prp2 mutations rescue lethal mutations in U2/U6 helix I. These data provide evidence that RNA elements that comprise the catalytic core are already formed at the Prp2p stage and that Prp2p destabilizes these elements, directly or indirectly, both to proofread spliceosome activation and to promote reconfiguration of the spliceosome to a fully competent, catalytic conformation. PMID:24442613

  10. Crystal-plane-controlled surface chemistry and catalytic performance of surfactant-free Cu2 O nanocrystals.

    PubMed

    Hua, Qing; Cao, Tian; Bao, Huizhi; Jiang, Zhiquan; Huang, Weixin

    2013-10-01

    Surfactant-free Cu2 O nanocrystals, including cubes exposing {100} crystal planes, octahedra exposing {111} crystal planes, and rhombic dodecahedra exposing {110} crystal planes, were used as model catalysts to study the effect of the crystal plane on the surface chemistry and catalytic performance for CO oxidation of Cu2 O nanocrystals. The catalytic performance follows the order of octahedra rhombic dodecahedra>cubes; this suggests that Cu2 O(111) is most active in catalyzing CO oxidation among Cu2 O (111), (110), and (100) surfaces. CO temperature-programmed reduction results demonstrate that Cu2 O octahedra are the most easily reduced of the Cu2 O cubes, octahedra, and rhombic dodecahedra. Diffuse reflectance FTIR spectra show that CO chemisorption on Cu2 O nanocrystals depends on their shape and the chemisorption temperature. CO chemisorption is strongest on rhombic dodecahedra at 30°C, but at 150°C on octahedra. Both the reducibility and chemisorption ability of various Cu2 O nanocrystals toward CO are consistent with their catalytic performance in CO oxidation. The observed surface chemistry and catalytic performance in CO oxidation of various Cu2 O nanocrystals can be well correlated with their exposed crystal plane and surface composition/structure. Cu2 O octahedra expose the {111} crystal plane with coordinated, unsaturated Cu(I) sites, and thus, are most active in chemisorbing CO and catalyzing CO oxidation. These results nicely demonstrate the crystal-plane-controlled surface chemistry and catalytic performance of oxide catalysts.

  11. Catalytic decomposition of H2O2 over Fe-based catalysts for simultaneous removal of NOX and SO2

    NASA Astrophysics Data System (ADS)

    Huang, Xianming; Ding, Jie; Zhong, Qin

    2015-01-01

    Simultaneous flue gas desulfurization and denitrification were achieved with rad OH radicals from the decomposition of H2O2 over hematite (Fe) as well as hematite supported on alumina (Fe-Al) and anatase (Fe-Ti). Under all conditions, SO2 achieved 100% removal, whereas NOX removal varies with the catalysts. The supporting of Fe over aluminum enhances the catalytic removal of NOX, whereas that of anatase presents negative effect. The NOX removal is determined by the decomposition rate of H2O2 into rad OH radicals over sbnd OH bonded with Fe (Fe-OH). The supporting of Fe over alumina enhances the content of Fe-OH and the points of zero charge (PZC) values, which are beneficial for the production of rad OH radicals. The supporting of Fe over anatase results in the formation of FeOTi, which cannot decompose H2O2 into rad OH radicals. Furthermore, H2O2 tends more to be reacted with TiOH to produce O2 over Fe-Ti. Finally, the enhancement mechanism of H2O2 decomposition over Fe-based catalysts is speculated. It has a contribution to the correct choice for supports and active ingredients of the catalyst in the future industrial applications.

  12. Catalytic mechanism of α-class carbonic anhydrases: CO2 hydration and proton transfer.

    PubMed

    Boone, Christopher D; Pinard, Melissa; McKenna, Rob; Silverman, David

    2014-01-01

    The carbonic anhydrases (CAs; EC 4.2.1.1) are a family of metalloenzymes that catalyze the reversible hydration of carbon dioxide (CO2) and dehydration of bicarbonate (HCO3 (-)) in a two-step ping-pong mechanism: [Formula: see text] CAs are ubiquitous enzymes and are categorized into five distinct classes (α, β, γ, δ and ζ). The α-class is found primarily in vertebrates (and the only class of CA in mammals), β is observed in higher plants and some prokaryotes, γ is present only in archaebacteria whereas the δ and ζ classes have only been observed in diatoms.The focus of this chapter is on α-CAs as the structure-function relationship is best understood for this class, in particular for humans. The reader is referred to other reviews for an overview of the structure and catalytic mechanism of the other CA classes. The overall catalytic site structure and geometry of α-CAs are described in the first section of this chapter followed by the kinetic studies, binding of CO2, and the proton shuttle network.

  13. Catalytic performance of activated carbon supported cobalt catalyst for CO2 reforming of CH4.

    PubMed

    Zhang, Guojie; Su, Aiting; Du, Yannian; Qu, Jiangwen; Xu, Ying

    2014-11-01

    Syngas production by CO2 reforming of CH4 in a fixed bed reactor was investigated over a series of activated carbon (AC) supported Co catalysts as a function of Co loading (between 15 and 30wt.%) and calcination temperature (Tc=300, 400 or 500°C). The catalytic performance was assessed through CH4 and CO2 conversions and long-term stability. XRD and SEM were used to characterize the catalysts. It was found that the stability of Co/AC catalysts was strongly dependent on the Co loading and calcination temperature. For the loadings (25wt.% for Tc=300°C), stable activities have been achieved. The loading of excess Co (>wt.% 25) causes negative effects not only on the performance of the catalysts but also on the support surface properties. In addition, the experiment showed that ultrasound can enhance and promote dispersion of the active metal on the carrier, thus improving the catalytic performance of the catalyst. The catalyst activity can be long-term stably maintained, and no obvious deactivation has been observed in the first 2700min. After analyzing the characteristics, a reaction mechanism for CO2 reforming of CH4 over Co/AC catalyst was proposed. Copyright © 2014 Elsevier Inc. All rights reserved.

  14. Atmospheric trace elements at Enewetak Atoll: 2. Transport to the ocean by wet and dry deposition

    NASA Astrophysics Data System (ADS)

    Arimoto, R.; Duce, R. A.; Ray, B. J.; Unni, C. K.

    1985-02-01

    The concentrations of trace elements in precipitation and dry deposition are presented for samples collected at Enewetak Atoll (11°N, 162° E) during SEAREX experiments in 1979. The concentrations of Al, Sc, Mn, Fe, Co, and Th in rain are dominated by crustal material, and for these elements, wet deposition evidently exceeds dry deposition. For most of these elements the present rates of atmospheric deposition at Enewetak are similar to their mean rate of accumulation in sediments over the past 5-10,000 years, suggesting that the air-to-sea exchange of particles is closely tied to the sedimentary cycle of the mid-Pacific. Noncrustal sources govern the concentrations of Pb, Zn, Cu, Se, and Cd in wet and dry deposition samples. Analyses of dry deposition collected from a flat plastic plate indicate that the amount of material recycled from the sea surface varies markedly between samples, and even though these estimates do not necessarily reflect the dry deposition to the ocean surface, the results suggest that recycled sea spray often amounts to more than 50% of the total dry deposition of the enriched elements. Recycled sea spray also makes up a significant fraction of the total wet deposition of the enriched elements. The net deposition rates of elements such as Cu and Zn are greater than or equal to their inputs from vertical mixing, but the net deposition of Pb clearly exceeds the input from upwelling. The current net deposition rates of the enriched elements are also similar to their rates of removal to sediments. These results indicate that air-sea exchange processes may significantly affect the chemistry of trace metals in the open ocean.

  15. Wetting of sodium on β''-Al2O3/YSZ composites for low temperature planar sodium-metal halide batteries

    SciTech Connect

    Reed, David; Coffey, Greg; Mast, Eric; Canfield, Nathan; Mansurov, Jirgal; Lu, Xiaochuan; Sprenkle, Vince

    2013-04-01

    Wetting of Na on B”-Al2O3/YSZ composites was investigated using the sessile drop technique. The effects of moisture and surface preparation were studied at low temperatures. Electrical conductivity of Na/B”-Al2O3-YSZ/Na cells was also investigated at low temperatures and correlated to the wetting behavior. The use of planar B”-Al2O3 substrates at low temperature with low cost polymeric seals is realized due to improved wetting at low temperature and conductivity values consistent with the literature.

  16. Numerical solution of 2D wet steam flow with non-equilibrium condensation and real thermodynamics

    SciTech Connect

    Hric, V.; Halama, J.

    2015-03-10

    An approach to modeling of wet steam flow with non-equilibrium condensation phenomenon is presented. The first part of our flow model is homogeneous Euler system of transport equations for mass, momentum and total energy of wet steam (mixture). The additional second part describes liquid phase via non-homogeneous system of transport equations for moments of droplets number distribution function and relies on corrected classical nucleation theory. Moment equations are closed by linearization of droplet growth rate model. All necessary relations for thermodynamic properties of steam are provided by IAPWS set of equations. However, properties of condensate are simply modeled by liquid saturation data. Two real equations of state are implemented. Recently developed CFD formulation for entropy (does not require iteration process) and so-called IAPWS special gas equation for Helmholtz energy (one iteration loop is necessary). Flow model is validated on converging-diverging supersonic nozzle with Barschdorff geometry. Simulations were performed by in-house CFD code based on finite volume method and stiff character of equations was solved by symmetrical time operator splitting. Achieved results satisfactorily agreed with experimental data.

  17. A Catalytic Sensor for Measurement of Radical Density in CO2 Plasmas

    PubMed Central

    Vesel, Alenka; Zaplotnik, Rok; Iacono, Jonathan; Balat-Pichelin, Marianne; Mozetic, Miran

    2012-01-01

    A catalytic sensor for the measurement of radical density in weakly ionized CO2 plasmas, created in a low-pressure electrodeless discharge, is presented. The CO2 plasma was created in a 4 cm wide borosilicate glass tube inside a copper coil connected to a radio frequency generator operating at 27.12 MHz with a nominal power of 250 W. The dissociation fraction of the CO2 molecules was measured in the early afterglow at pressures ranging from 10 Pa to 100 Pa, and at distances of up to 35 cm along the gas stream from the glowing plasma. The radical density peaked (2 × 1020 m−3) at 80 Pa. The density quickly decreased with increasing distance from the glowing plasma despite a rather large drift velocity. The dissociation fraction showed similar behavior, except that the maximum was obtained at somewhat lower pressure. The results were explained by rather intense surface recombination of radicals. PMID:23443372

  18. Heterogeneous catalytic ozonation of 2-chlorophenol aqueous solution with alumina as a catalyst.

    PubMed

    Ni, C H; Chen, J N

    2001-01-01

    Heterogenous catalytic ozonation of 2-chlorophenol (2-CP) in the presence of gamma-alumina as a solid catalyst has been investigated in this research. It showed that the rate for degradation of TOC could increase from 21% to 43%. The pseudo-first reaction constants of 2-CP could increase from 0.8688 min-1 to 0.1270, increasing by approximately 40%. At the same time, the consumption of ozone was only half that of ozone alone. This research also explored the effects of the catalyst dosage, pH values and removal kinetics of 2-CP. In addition, three consecutive running with the same catalyst revealed insignificant reduction of the activity. Furthermore, the elimination of toxicity was evaluated by Microtox analysis. The detoxification was more stable and with good results.

  19. MnO2/CeO2 for catalytic ultrasonic decolorization of methyl orange: Process parameters and mechanisms.

    PubMed

    Zhao, He; Zhang, Guangming; Chong, Shan; Zhang, Nan; Liu, Yucai

    2015-11-01

    MnO2/CeO2 catalyst was prepared and characterized by means of Brunauer-Emmet-Teller (BET) method, X-ray diffraction (XRD) and scanning electron microscope (SEM). The characterization showed that MnO2/CeO2 had big specific surface area and MnO2 was dispersed homogeneously on the surface of CeO2. Excellent degradation efficiency of methyl orange was achieved by MnO2/CeO2 catalytic ultrasonic process. Operating parameters were studied and optimized. The optimal conditions were 10 min of ultrasonic irradiation, 1.0 g/L of catalyst dose, 2.6 of pH value and 1.3 W/ml of ultrasonic density. Under the optimal conditions, nearly 90% of methyl orange was removed. The mechanism of methyl orange degradation was further studied. The decolorization mechanism in the ultrasound-MnO2/CeO2 system was quite different with that in the ultrasound-MnO2 system. Effects of manganese and cerium in catalytic ultrasonic process were clarified. Manganese ions in solution contributed to generating hydroxyl free radical. MnO2/CeO2 catalyst strengthened the oxidation ability of ultrasound and realized complete decolorization of methyl orange.

  20. In situ IR studies of Co and Ce doped Mn/TiO2 catalyst for low-temperature selective catalytic reduction of NO with NH3

    NASA Astrophysics Data System (ADS)

    Qiu, Lu; Pang, Dandan; Zhang, Changliang; Meng, Jiaojiao; Zhu, Rongshu; Ouyang, Feng

    2015-12-01

    The Mn-Co-Ce/TiO2 catalyst was prepared by wet co-impregnation method for selective catalytic reduction of NO by NH3 in the presence of oxygen. The adsorption and co-adsorption of NH3, NO and O2 on catalysts were investigated by in situ FTIR spectroscopy. The results suggested that addition of cobalt and cerium oxides increased the numbers of acid and redox sites. Especially, the cobalt oxide produced lots of Brønsted acid sites, which favor to the adsorption of coordinated NH3 through NH3 migration. Ce addition improved amide ions formation to reach best NO reduction selectivity. A mechanistic pathway over Mn-Co-Ce/TiO2 was proposed. At low-temperature SCR reaction, coordinated NH3 reacted with NO2-, and amide reacted with NO (ad) or NO (g) to form N2. NO2 was related to the formation of nitrite on Co-contained catalysts and the generation of sbnd NH2- on Ce-contained catalysts. At high temperature, the other branch reaction also occurred between the coordinated NH3 and nitrate species, resulting in N2O yield increase.

  1. Preparation and catalytic activities for H{sub 2}O{sub 2} decomposition of Rh/Au bimetallic nanoparticles

    SciTech Connect

    Zhang, Haijun; Deng, Xiangong; Jiao, Chengpeng; Lu, Lilin; Zhang, Shaowei

    2016-07-15

    Graphical abstract: PVP-protected Rh/Au bimetallic nanoparticles (BNPs) were prepared by using hydrogen sacrificial reduction method, the activity of Rh80Au20 BNPs were about 3.6 times higher than that of Rh NPs. - Highlights: • Rh/Au bimetallic nanoparticles (BNPs) of 3∼5 nm in diameter were prepared. • Activity for H{sub 2}O{sub 2} decomposition of BNPs is 3.6 times higher than that of Rh NPs. • The high activity of BNPs was caused by the existence of charged Rh atoms. • The apparent activation energy for H{sub 2}O{sub 2} decomposition over the BNPs was calculated. - Abstract: PVP-protected Rh/Au bimetallic nanoparticles (BNPs) were prepared by using hydrogen sacrificial reduction method and characterized by UV–vis, XRD, FT-IR, XPS, TEM, HR-TEM and DF-STEM, the effects of composition on their particle sizes and catalytic activities for H{sub 2}O{sub 2} decomposition were also studied. The as-prepared Rh/Au BNPs possessed a high catalytic activity for the H{sub 2}O{sub 2} decomposition, and the activity of the Rh{sub 80}Au{sub 20} BNPs with average size of 2.7 nm were about 3.6 times higher than that of Rh monometallic nanoparticles (MNPs) even the Rh MNPs possess a smaller particle size of 1.7 nm. In contrast, Au MNPs with size of 2.7 nm show no any activity. Density functional theory (DFT) calculation as well as XPS results showed that charged Rh and Au atoms formed via electronic charge transfer effects could be responsible for the high catalytic activity of the BNPs.

  2. Improved Wetting Characteristics in TiO2–Modified Ag-CuO Air Braze Filler Metals

    SciTech Connect

    Weil, K. Scott; Kim, Jin Yong Y.; Hardy, John S.; Darsell, Jens T.

    2006-01-01

    In this paper we report on the results of a series of sessile drop experiments designed to examine the effect of TiO2 on the wetting behavior of Ag-CuO air braze filler metals. It was found that TiO2 concentrations as small as 0.5 mol% can significantly decrease the contact angle of Ag-CuO on alumina over a compositional range of 1 – 34mol% CuO. The effect appears to maximize at a copper oxide concentration of ~4 mol% CuO regardless of the titania content.

  3. (Catalytic mechanism of hydrogenase from aerobic N2-fixing microorganisms). [Azotobacter vinelandii:a1

    SciTech Connect

    Not Available

    1991-01-01

    The results of this DOE-sponsored project have contributed to our understanding of the catalytic mechanism of A. vinelandii hydrogenase. A group of inhibitors have been characterized. These provide information about the different types of redox clusters involved in catalysis and the roles of each. One group has already used acetylene in a study of three desulfovibrian hydrogenases and shown that onbly the NiFe hydrogenases are inhibited. The inhibitor studies are also being extended to other enzymes. We have characterized a number of special properties of A. vinelandii hydrogenase. While the NiFe dimeric hydrogenases are now recognized as a large group of similar enzymes, there are differences in the spectral and catalytic properties which are not explained by their similar redox inventories, identical subunit structures, immunological cross reactivity and conserved sequences. Surprisingly, we only see a significant EPR signal attributable to Ni after the enzyme has been inactivated with O{sub 2} and then re-reduced (though not reactivated). Acetylene, which does not substantially perterb the EPR signal of active hydrogenase, does result in a new absorption envelope in the UV-Vis spectrum. Overall, the results of this project have revealed the complex interactions of the redox clusters in catalysis through studies of inhibitor mechanisms and spectral properties. 14 refs., 9 figs.

  4. Catalytic Enantioselective [2,3]-Rearrangements of Allylic Ammonium Ylides: A Mechanistic and Computational Study

    PubMed Central

    2017-01-01

    A mechanistic study of the isothiourea-catalyzed enantioselective [2,3]-rearrangement of allylic ammonium ylides is described. Reaction kinetic analyses using 19F NMR and density functional theory computations have elucidated a reaction profile and allowed identification of the catalyst resting state and turnover-rate limiting step. A catalytically relevant catalyst–substrate adduct has been observed, and its constitution elucidated unambiguously by 13C and 15N isotopic labeling. Isotopic entrainment has shown the observed catalyst–substrate adduct to be a genuine intermediate on the productive cycle toward catalysis. The influence of HOBt as an additive upon the reaction, catalyst resting state, and turnover-rate limiting step has been examined. Crossover experiments have probed the reversibility of each of the proposed steps of the catalytic cycle. Computations were also used to elucidate the origins of stereocontrol, with a 1,5-S···O interaction and the catalyst stereodirecting group providing transition structure rigidification and enantioselectivity, while preference for cation−π interactions over C–H···π is responsible for diastereoselectivity. PMID:28230365

  5. Effects of Detergents on Catalytic Activity of Human Endometase/Matrilysin-2, a Putative Cancer Biomarker†

    PubMed Central

    Park, Hyun I.; Lee, Seakwoo; Ullah, Asad; Cao, Qiang; Sang, Qing-Xiang Amy

    2009-01-01

    Matrix metalloproteinases (MMPs) are a family of hydrolytic enzymes that play significant roles in development, morphogenesis, inflammation, and cancer invasion. Endometase (matrilysin 2 or MMP-26) is a putative early biomarker for human carcinomas. The effects of the ionic and nonionic detergents on catalytic activity of endometase were investigated. The hydrolytic activity of endometase was detergent concentration-dependent exhibiting a bell-shaped curve with its maximum activity near the critical micelle concentration (CMC) of nonionic detergents tested. The effect of Brij-35 on human gelatinase B (MMP-9), matirilysin (MMP-7), and membrane-type 1 MMP (MT1-MMP) was further explored. Their maximum catalysis was observed near the CMC of Brij-35 (~90 μM). Their IC50 values were above the CMC. The inhibition mechanism of MMP-7, MMP-9, and MT1-MMP by Brij-35 was mixed-type as determined by Dixon’s plot, however, that of endometase was non-competitive with a Ki value of 240 μM. The catalytic activities of MMPs are influenced by detergents. Monomer of detergents may activate and stabilize MMPs to enhance catalysis, but micelle of detergents may sequester enzyme and block substrate binding site to impede catalysis. Under physiological conditions lipid or membrane microenvironment may regulate enzymatic activity. PMID:19818727

  6. Effects of detergents on catalytic activity of human endometase/matrilysin 2, a putative cancer biomarker.

    PubMed

    Park, Hyun I; Lee, Seakwoo; Ullah, Asad; Cao, Qiang; Sang, Qing-Xiang Amy

    2010-01-15

    Matrix metalloproteinases (MMPs) are a family of hydrolytic enzymes that play significant roles in development, morphogenesis, inflammation, and cancer invasion. Endometase (matrilysin 2 or MMP-26) is a putative early biomarker for human carcinomas. The effects of the ionic and nonionic detergents on catalytic activity of endometase were investigated. The hydrolytic activity of endometase was detergent concentration dependent, exhibiting a bell-shaped curve with its maximum activity near the critical micelle concentration (CMC) of nonionic detergents tested. The effect of Brij-35 on human gelatinase B (MMP-9), matrilysin (MMP-7), and membrane-type 1 MMP (MT1-MMP) was further explored. Their maximum catalysis was observed near the CMC of Brij-35 ( approximately 90muM). Their IC(50) values were above the CMC. The inhibition mechanism of MMP-7, MMP-9, and MT1-MMP by Brij-35 was a mixed type as determined by Dixon's plot; however, the inhibition mechanism of endometase was noncompetitive with a K(i) value of 240muM. The catalytic activities of MMPs are influenced by detergents. Monomer of detergents may activate and stabilize MMPs to enhance catalysis, but micelle of detergents may sequester enzyme and block the substrate binding site to impede catalysis. Under physiological conditions, a lipid or membrane microenvironment may regulate enzymatic activity.

  7. (Catalytic mechanism of hydrogenase from aerobic N sub 2 -fixing microorganisms)

    SciTech Connect

    Arp, D.J.

    1990-01-01

    Hydrogenases are enzymes which catalyze reactions involving dihydrogen. They serve integral roles in a number of microbial metabolic pathways. Our research is focussed on investigations of the catalytic mechanism of the hydrogenases found in aerobic, N{sub 2}-fixing microorganisms such as Azotobacter vinelandii and the agronomically important Bradyrhizobium japonicum as well as microorganisms with similar hydrogenases. The hydrogenases isolated from these microorganisms are Ni- and Fe-containing heterodimers. Our work has focussed on three areas during the last grant period. In all cases, a central theme has been the role of inhibitors in the characteristics under investigation. In addition, a number of collaborative efforts have yielded interesting results. In metalloenzymes such as hydrogenase, inhibitors often influence the activity of the enzyme through ligand interactions with redox centers, often metals, within the enzyme. Therefore, investigations of the ability of various compounds to inhibit an enzyme's activity, as well as the mechanism of inhibition, can provide insight into the catalytic mechanism of the enzyme as well as the role of various redox centers in catalysis. We have investigated in detail four inhibitors of A. vinelandii and the results are summarized here. The influence of these inhibitors on the spectral properties of the enzyme are summarized. Electron paramagnetic resonance and ultraviolet spectra investigations are discussed. 9 figs.

  8. Catalytic Enantioselective [2,3]-Rearrangements of Allylic Ammonium Ylides: A Mechanistic and Computational Study.

    PubMed

    West, Thomas H; Walden, Daniel M; Taylor, James E; Brueckner, Alexander C; Johnston, Ryne C; Cheong, Paul Ha-Yeon; Lloyd-Jones, Guy C; Smith, Andrew D

    2017-03-10

    A mechanistic study of the isothiourea-catalyzed enantioselective [2,3]-rearrangement of allylic ammonium ylides is described. Reaction kinetic analyses using (19)F NMR and density functional theory computations have elucidated a reaction profile and allowed identification of the catalyst resting state and turnover-rate limiting step. A catalytically relevant catalyst-substrate adduct has been observed, and its constitution elucidated unambiguously by (13)C and (15)N isotopic labeling. Isotopic entrainment has shown the observed catalyst-substrate adduct to be a genuine intermediate on the productive cycle toward catalysis. The influence of HOBt as an additive upon the reaction, catalyst resting state, and turnover-rate limiting step has been examined. Crossover experiments have probed the reversibility of each of the proposed steps of the catalytic cycle. Computations were also used to elucidate the origins of stereocontrol, with a 1,5-S···O interaction and the catalyst stereodirecting group providing transition structure rigidification and enantioselectivity, while preference for cation-π interactions over C-H···π is responsible for diastereoselectivity.

  9. Effect of MnO2 morphology on the catalytic oxidation of toluene over Ag/MnO2 catalysts

    NASA Astrophysics Data System (ADS)

    Li, Jiamin; Qu, Zhenping; Qin, Yuan; Wang, Hui

    2016-11-01

    The Ag/MnO2 catalysts with different morphologies (wire-like, rod-like and tube-like) are used as toluene oxidation catalysts in an attempt to investigate how the structures of support affect the interaction of Ag and MnO2, and thus the toluene catalytic activity. Analysis by TEM, H2-TPR and XPS measurements reveals that the structures of MnO2 influence the particle size and dispersion of silver particles and the combination of silver particles with MnO2. Meanwhile, the addition of Ag regulates the performance of MnO2. The small particle size and hemispherically shaped Ag particles are easily to form and homogeneously dispersed on the surface of wire-like MnO2. And this specific form of Ag shows the strongest interaction with MnO2, which promotes the low-temperature reducibility of support and generated more lattice oxygen in metal oxides. The Ag/MnO2 nanowires sample exhibits the highest reactivity for toluene oxidation with a complete conversion at 220 °C. Therefore, the excellent catalytic performance of Ag/MnO2 nanowires catalyst for toluene oxidation is clearly connected with the interaction between the Ag and MnO2, which is determined by the morphology of MnO2 support.

  10. Control of a selective catalytic reduction system based on NARMA-L2 model

    NASA Astrophysics Data System (ADS)

    Han, W. M.; Wang, Y. J.; Zheng, T. X.; Zhou, T. L.; Zhang, Y.; Tan, R.

    2017-03-01

    The plant of the selective catalytic reduction (SCR) system is characterized by significant nonlinearity, time delay and temperature sensitivity. In order to control the urea injection accurately, the (nonlinear auto regressive moving average) NARMA-L2 model based control is applied to the SCR system. In this paper, a data-based technique is taken and a model of the plant is identified on the basis of input-output data. Then the identified model is used to the design of a NARMA-L2 controller. Simulation of the NARMA-L2 model based control for the SCR system is presented to demonstrate the effectiveness and superiority. The comparison results show better performance over the traditional PID control.

  11. Mechanistic Insights into Hydride Transfer for Catalytic Hydrogenation of CO2 with Cobalt Complexes

    SciTech Connect

    Kumar, Neeraj; Camaioni, Donald M.; Dupuis, Michel; Raugei, Simone; Appel, Aaron M.

    2014-08-21

    The catalytic hydrogenation of CO2 to formate by Co(dmpe)2H can proceeds via direct hydride transfer or via CO2 coordination to Co followed by reductive elimination of formate. Both pathways have activation barriers consistent with experiment (~17.5 kcal/mol). Controlling the basicity of Co by ligand design is key to improve catalysis. The research by N.K., D.M.C. and A.M.A. was supported by the US Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. The research by S.R. and M.D. was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for the DOE by Battelle.

  12. 40 CFR Table 2 to Subpart Uuu of... - Operating Limits for Metal HAP Emissions From Catalytic Cracking Units

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 13 2013-07-01 2012-07-01 true Operating Limits for Metal HAP Emissions From Catalytic Cracking Units 2 Table 2 to Subpart UUU of Part 63 Protection of Environment... Units Pt. 63, Subpt. UUU, Table 2 Table 2 to Subpart UUU of Part 63—Operating Limits for Metal...

  13. Degradation of the ammonia wastewater in aqueous medium with ozone in combination with mesoporous TiO2 catalytic

    NASA Astrophysics Data System (ADS)

    Liu, Zhiwu; Qiu, Jianping; Zheng, Chaocan; Li, Liqing

    2017-03-01

    TiO2 mesoporous nanomaterials are now widely used in catalytic ozone technology. In this paper, the market P25 as precursor hydrothermal method to prepare TiO2 mesoporous materials, ozone catalyst material characterization by transmission electron microscopy, surface area analyzers, and X-ray diffraction technique and found that nanotubes, nanosheets, nanorods through characterization results, nano-particles of different morphology and anatase and rutile proportion of the ozone catalytic material can be controlled by the calcination temperature and the temperature of hot water to give, and with the hot water temperature and calcination temperature, the catalyst becomes small aperture size larger catalyst crystalline phase from anatase to rutile gradually shift. Catalytic materials have been prepared by the Joint ozone degradation of ammonia wastewater to evaluate mesoporous TiO2 nanomaterials ozone catalytic performance, the results showed that: ammonia wastewater removal efficiency of various catalytic materials relatively separate ozone and markets P25 effects are significantly improved, and TiO2 nanotubes cooperate with ozone degradation ammonia wastewater highest efficiency, in addition, rutile TiO2 catalysts, the more the better the performance of their ozone catalysis.

  14. Removal of formaldehyde over Mn(x)Ce(1)-(x)O(2) catalysts: thermal catalytic oxidation versus ozone catalytic oxidation.

    PubMed

    Li, Jia Wei; Pan, Kuan Lun; Yu, Sheng Jen; Yan, Shaw Yi; Chang, Moo Been

    2014-12-01

    Mn(x)Ce(1)-(x)O(2) (x: 0.3-0.9) prepared by Pechini method was used as a catalyst for the thermal catalytic oxidation of formaldehyde (HCHO). At x=0.3 and 0.5, most of the manganese was incorporated in the fluorite structure of CeO(2) to form a solid solution. The catalytic activity was best at x=0.5, at which the temperature of 100% removal rate is the lowest (270°C). The temperature for 100% removal of HCHO oxidation is reduced by approximately 40°C by loading 5wt.% CuO(x) into Mn(0.5)Ce(0.5)O(2). With ozone catalytic oxidation, HCHO (61 ppm) in gas stream was completely oxidized by adding 506 ppm O₃over Mn(0.5)Ce(0.5)O(2) catalyst with a GHSV (gas hourly space velocity) of 10,000 hr⁻¹ at 25°C. The effect of the molar ratio of O(3) to HCHO was also investigated. As O(3)/HCHO ratio was increased from 3 to 8, the removal efficiency of HCHO was increased from 83.3% to 100%. With O(3)/HCHO ratio of 8, the mineralization efficiency of HCHO to CO(2) was 86.1%. At 25°C, the p-type oxide semiconductor (Mn(0.5)Ce(0.5)O(2)) exhibited an excellent ozone decomposition efficiency of 99.2%, which significantly exceeded that of n-type oxide semiconductors such as TiO(2), which had a low ozone decomposition efficiency (9.81%). At a GHSV of 10,000 hr⁻¹, [O(3)]/[HCHO]=3 and temperature of 25°C, a high HCHO removal efficiency (≥ 81.2%) was maintained throughout the durability test of 80 hr, indicating the long-term stability of the catalyst for HCHO removal. Copyright © 2014. Published by Elsevier B.V.

  15. Theoretical Studies of the HO/HO2 Catalytic Cycle for Ozone Destruction

    NASA Technical Reports Server (NTRS)

    Walch, Stephen P.; Langhoff, Steve R. (Technical Monitor)

    1996-01-01

    Recently it has been determined that the HO/HO2 catalytic cycle accounts for nearly one-half of the total ozone depletion in the lower stratosphere. The catalytic cycle is: (1) HO + O3 yields HO2 + O2; (2) HO2 + O3 yields HO + O2 + O2. The net reaction is 2O3 yields 3O2. The rate limiting step in this process is the reaction of HO2 with ozone. There is a problem extending the experimental measurement of the rate of this reaction over the range 233-400 K down to stratospheric temperatures of 210-220 K. Therefore we have undertaken a project to determine the temperature dependence of the rate constant for this reaction in the low temperature region. The first step in this project, which is described in this poster, is the determination of the relevant potential energy surfaces. The calculations use CASSCF/derivative methods to define the pathways followed by CASSCF/ACPF to determine the energetics. The HO + O3 reaction is found to proceed through an HO4 complex, which is unstable with respect to HO2 + O2. The HO2 +O3 reaction is more complex. One pathway, which has been characterized, is the formation of an HO5 complex which decomposes to HO3 + O2 and subsequently to HO + O2 + O2. Another pathway, which is believed to also play a role, is hydrogen abstraction to give O2 + HO3 and subsequent decomposition of HO3 to HO + O2. Isotopic labeling experiments indicate that the later pathway is dominant. However, so far attempts to locate the saddle point for this pathway have not been successful. We have also characterized the potential energy surfaces for a number of species involved in these reactions, including HO3 and triplet O4. The triplet O4 species is probably involved in the reaction of vibrationally excited O2 with ground state O2 leading to O3 + O. The latter reaction is believed to be important as an additional source of stratospheric ozone.

  16. Theoretical Studies of the HO/HO2 Catalytic Cycle for Ozone Destruction

    NASA Technical Reports Server (NTRS)

    Walch, Stephen P.; Langhoff, Steve R. (Technical Monitor)

    1996-01-01

    Recently it has been determined that the HO/HO2 catalytic cycle accounts for nearly one-half of the total ozone depletion in the lower stratosphere. The catalytic cycle is: (1) HO + O3 yields HO2 + O2; (2) HO2 + O3 yields HO + O2 + O2. The net reaction is 2O3 yields 3O2. The rate limiting step in this process is the reaction of HO2 with ozone. There is a problem extending the experimental measurement of the rate of this reaction over the range 233-400 K down to stratospheric temperatures of 210-220 K. Therefore we have undertaken a project to determine the temperature dependence of the rate constant for this reaction in the low temperature region. The first step in this project, which is described in this poster, is the determination of the relevant potential energy surfaces. The calculations use CASSCF/derivative methods to define the pathways followed by CASSCF/ACPF to determine the energetics. The HO + O3 reaction is found to proceed through an HO4 complex, which is unstable with respect to HO2 + O2. The HO2 +O3 reaction is more complex. One pathway, which has been characterized, is the formation of an HO5 complex which decomposes to HO3 + O2 and subsequently to HO + O2 + O2. Another pathway, which is believed to also play a role, is hydrogen abstraction to give O2 + HO3 and subsequent decomposition of HO3 to HO + O2. Isotopic labeling experiments indicate that the later pathway is dominant. However, so far attempts to locate the saddle point for this pathway have not been successful. We have also characterized the potential energy surfaces for a number of species involved in these reactions, including HO3 and triplet O4. The triplet O4 species is probably involved in the reaction of vibrationally excited O2 with ground state O2 leading to O3 + O. The latter reaction is believed to be important as an additional source of stratospheric ozone.

  17. Predicting CYP2C19 catalytic parameters for enantioselective oxidations using artificial neural networks and a chirality code.

    PubMed

    Hartman, Jessica H; Cothren, Steven D; Park, Sun-Ha; Yun, Chul-Ho; Darsey, Jerry A; Miller, Grover P

    2013-07-01

    Cytochromes P450 (CYP for isoforms) play a central role in biological processes especially metabolism of chiral molecules; thus, development of computational methods to predict parameters for chiral reactions is important for advancing this field. In this study, we identified the most optimal artificial neural networks using conformation-independent chirality codes to predict CYP2C19 catalytic parameters for enantioselective reactions. Optimization of the neural networks required identifying the most suitable representation of structure among a diverse array of training substrates, normalizing distribution of the corresponding catalytic parameters (k(cat), K(m), and k(cat)/K(m)), and determining the best topology for networks to make predictions. Among different structural descriptors, the use of partial atomic charges according to the CHelpG scheme and inclusion of hydrogens yielded the most optimal artificial neural networks. Their training also required resolution of poorly distributed output catalytic parameters using a Box-Cox transformation. End point leave-one-out cross correlations of the best neural networks revealed that predictions for individual catalytic parameters (k(cat) and K(m)) were more consistent with experimental values than those for catalytic efficiency (k(cat)/K(m)). Lastly, neural networks predicted correctly enantioselectivity and comparable catalytic parameters measured in this study for previously uncharacterized CYP2C19 substrates, R- and S-propranolol. Taken together, these seminal computational studies for CYP2C19 are the first to predict all catalytic parameters for enantioselective reactions using artificial neural networks and thus provide a foundation for expanding the prediction of cytochrome P450 reactions to chiral drugs, pollutants, and other biologically active compounds. Copyright © 2013 Elsevier Ltd. All rights reserved.

  18. The effect of CNTs on structures and catalytic properties of AuPd clusters for H2O2 synthesis.

    PubMed

    Yang, Hua-feng; Xie, Peng-yang; Yu, Hui-you; Li, Xiao-nian; Wang, Jian-guo

    2012-12-28

    The structures and catalytic properties of AuPd clusters supported on carbon nanotubes (CNTs) for H(2)O(2) synthesis have been investigated by means of density functional theory calculations. Firstly, the structures of AuPd clusters are strongly influenced by CNTs, in which the bottom layers are mainly composed of Pd and the top layers are a mix of Au and Pd due to the stronger binding of Pd than Au on CNTs. Especially, it is found that O(2) adsorption on the Pd/CNTs interfacial sites is much weaker than that on the only Pd sites, which is in contrast to transition metal oxide (for example TiO(2), Al(2)O(3), CeO(2)) supported metal clusters. Furthermore, Pd ensembles on the interfacial sites have far superior catalytic properties for H(2)O(2) formation than those away from CNT supports due to the changes in electronic structures caused by the CNTs. Therefore, our study provides a physical insight into the enhanced role of carbon supports in H(2)O(2) synthesis over supported AuPd catalysts.

  19. Catalytic reduction of CO2 by H2 for synthesis of CO, methanol and hydrocarbons: challenges and opportunities

    DOE PAGES

    Porosoff, Marc D.; Yan, Binhang; Chen, Jingguang G.

    2015-10-22

    Ocean acidification and climate change are expected to be two of the most difficult scientific challenges of the 21st century. Converting CO2 into valuable chemicals and fuels is one of the most practical routes for reducing CO2 emissions while fossil fuels continue to dominate the energy sector. Reducing CO2 by H2 using heterogeneous catalysis has been studied extensively, but there are still significant challenges in developing active, selective and stable catalysts suitable for large-scale commercialization. We study the catalytic reduction of CO2 by H2 can lead to the formation of three types of products: CO through the reverse water–gas shiftmore » (RWGS) reaction, methanol via selective hydrogenation, and hydrocarbons through combination of CO2 reduction with Fischer–Tropsch (FT) reactions. In addition, investigations into these routes reveal that the stabilization of key reaction intermediates is critically important for controlling catalytic selectivity. Furthermore, viability of these processes is contingent on the development of a CO2-free H2 source on a large enough scale to significantly reduce CO2 emissions.« less

  20. Effect of phase interaction on catalytic CO oxidation over the SnO2/Al2O3 model catalyst

    NASA Astrophysics Data System (ADS)

    Chai, Shujing; Bai, Xueqin; Li, Jing; Liu, Cheng; Ding, Tong; Tian, Ye; Liu, Chang; Xian, Hui; Mi, Wenbo; Li, Xingang

    2017-04-01

    We investigated the catalytic CO oxidation over the SnO2/Al2O3 model catalysts. Our results show that interaction between the Al2O3 and SnO2 phases results in the significantly improved catalytic activity because of the formation of the oxygen vacancies. The oxygen storage capacity of the SnO2/Al2O3 catalyst prepared by the physically mixed method is nearly two times higher than that of the SnO2, which probably results from the change of electron concentration on the interface of the SnO2 and Al2O3 phases. Introducing water vapor to the feeding gas would a little decrease the activity of the catalysts, but the reaction rate could completely recover after removal of water vapor. The kinetics results suggest that the surface Sn4+ cations are effective CO adsorptive sites, and the surface adsorbed oxygen plays an important role upon CO oxidation. The reaction pathways upon the SnO2-based catalysts for CO oxidation follow the Langmuir-Hinshelwood model.

  1. Workshop on early Mars: How warm and how wet, part 2?

    NASA Technical Reports Server (NTRS)

    Squyres, S. (Editor); Kasting, J. (Editor)

    1993-01-01

    In 1992 the MSATT program conducted a workshop on modeling of the Martian climate. At that workshop it became clear that a serious problem had arisen concerning the early climate of Mars. Based on the evidence for smallscale fluvial activity, the view had been widely held that early in its history Mars had a climate that was much warmer and wetter than today's. However, most plausible recent climate models have fallen far short of the warm temperatures often inferred from the geologic evidence. Moreover, recent geophysical work has suggested that early geothermal warming may also have played a significant role in allowing fluvial activity. In order to address the issue of just how warm and how wet early Mars was, a workshop was convened in July of 1993, in Breckenridge, Colorado. The results of the workshop are reported here.

  2. Site-directed mutagenesis of possible catalytic residues of cellobiose 2-epimerase from Ruminococcus albus.

    PubMed

    Ito, Shigeaki; Hamada, Shigeki; Ito, Hiroyuki; Matsui, Hirokazu; Ozawa, Tadahiro; Taguchi, Hidenori; Ito, Susumu

    2009-07-01

    The cellobiose 2-epimerase from Ruminococcus albus (RaCE) catalyzes the epimerization of cellobiose and lactose to 4-O-beta-D-glucopyranosyl-D-mannose and 4-O-beta-D-galactopyranosyl-D-mannose (epilactose). Based on the sequence alignment with N-acetyl-D-glucosamine 2-epimerases of known structure and on a homology-modeled structure of RaCE, we performed site-directed mutagenesis of possible catalytic residues in the enzyme, and the mutants were expressed in Escherichia coli cells. We found that R52, H243, E246, W249, W304, E308, and H374 were absolutely required for the activity of RaCE. F114 and W303 also contributed to catalysis. These residues protruded into the active-site cleft in the model (alpha/alpha)(6) core barrel structure.

  3. Catalytic sterilization of Escherichia coli K 12 on Ag/Al2O3 surface.

    PubMed

    Chen, Meixue; Yan, Lizhu; He, Hong; Chang, Qingyun; Yu, Yunbo; Qu, Jiuhui

    2007-05-01

    Bactericidal action of Al(2)O(3), Ag/Al(2)O(3) and AgCl/Al(2)O(3) on pure culture of Escherichia coli K 12 was studied. Ag/Al(2)O(3) and AgCl/Al(2)O(3) demonstrated a stronger bactericidal activity than Al(2)O(3). The colony-forming ability of E. coli was completely lost in 0.5 min on both of Ag/Al(2)O(3) and AgCl/Al(2)O(3) at room temperature in air. The configuration of the bacteria on the catalyst surface was observed using scanning electron microscopy (SEM). Reactive oxygen species (ROS) play an important role in the expression of the bactericidal activity on the surface of catalysts by assay with O(2)/N(2) bubbling and scavenger for ROS. Furthermore, the formation of CO(2) as an oxidation product could be detected by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and be deduced by total carbon analysis. These results strongly support that the bactericidal process on the surface of Ag/Al(2)O(3) and AgCl/Al(2)O(3) was caused by the catalytic oxidation.

  4. The Alpha Catalytic Subunit of Protein Kinase CK2 Is Required for Mouse Embryonic Development▿

    PubMed Central

    Lou, David Y.; Dominguez, Isabel; Toselli, Paul; Landesman-Bollag, Esther; O'Brien, Conor; Seldin, David C.

    2008-01-01

    Protein kinase CK2 (formerly casein kinase II) is a highly conserved and ubiquitous serine/threonine kinase that is composed of two catalytic subunits (CK2α and/or CK2α′) and two CK2β regulatory subunits. CK2 has many substrates in cells, and key roles in yeast cell physiology have been uncovered by introducing subunit mutations. Gene-targeting experiments have demonstrated that in mice, the CK2β gene is required for early embryonic development, while the CK2α′ subunit appears to be essential only for normal spermatogenesis. We have used homologous recombination to disrupt the CK2α gene in the mouse germ line. Embryos lacking CK2α have a marked reduction in CK2 activity in spite of the presence of the CK2α′ subunit. CK2α−/− embryos die in mid-gestation, with abnormalities including open neural tubes and reductions in the branchial arches. Defects in the formation of the heart lead to hydrops fetalis and are likely the cause of embryonic lethality. Thus, CK2α appears to play an essential and uncompensated role in mammalian development. PMID:17954558

  5. Studies on Escherichia coli RNase P RNA with Zn2+ as the catalytic cofactor

    PubMed Central

    Cuzic, Simona; Hartmann, Roland K.

    2005-01-01

    We demonstrate, for the first time, catalysis by Escherichia coli ribonuclease P (RNase P) RNA with Zn2+ as the sole divalent metal ion cofactor in the presence of ammonium, but not sodium or potassium salts. Hill analysis suggests a role for two or more Zn2+ ions in catalysis. Whereas Zn2+ destabilizes substrate ground state binding to an extent that precludes reliable Kd determination, Co(NH3)63+ and Sr2+ in particular, both unable to support catalysis by themselves, promote high-substrate affinity. Zn2+ and Co(NH3)63+ substantially reduce the fraction of precursor tRNA molecules capable of binding to RNase P RNA. Stimulating and inhibitory effects of Sr2+ on the ribozyme reaction with Zn2+ as cofactor could be rationalized by a model involving two Sr2+ ions (or two classes of Sr2+ ions). Both ions improve substrate affinity in a cooperative manner, but one of the two inhibits substrate conversion in a non-competitive mode with respect to the substrate and the Zn2+. A single 2′-fluoro modification at nt −1 of the substrate substantially weakened the inhibitory effect of Sr2+. Our results demonstrate that the studies on RNase P RNA with metal cofactors other than Mg2+ entail complex effects on structural equilibria of ribozyme and substrate RNAs as well as E·S formation apart from the catalytic performance. PMID:15867194

  6. Efficient photothermal catalytic hydrogen production over nonplasmonic Pt metal supported on TiO2

    NASA Astrophysics Data System (ADS)

    Song, Rui; Luo, Bing; Jing, Dengwei

    2016-10-01

    Most of the traditional photocatalytic hydrogen productions were conducted under room temperature. In this work, we selected nonplasmonic Pt metal anchored on TiO2 nanoparticles with photothermal activity to explore more efficient hydrogen production technology over the whole solar spectrum. Photothermal experiments were carried out in a carefully designed top irradiated photocatalytic reactor that can withstand high temperature and relatively higher pressure. Four typical organic materials, i.e., methyl alcohol (MeOH), trielthanolamne (TEOA), formic acid (HCOOH) and glucose, were investigated. Formic acid, a typical hydrogen carrier, was found to show the best activity. In addition, the effects of different basic parameters such as sacrificial agent concentration and the temperature on the activity of hydrogen generation were systematically investigated for understanding the qualitative and quantitative effects of the photothermal catalytic reaction process. The hydrogen yields at 90 °C of the photothermal catalytic reaction with Pt/TiO2 are around 8.1 and 4.2 times higher than those of reactions carried out under photo or thermal conditions alone. We can see that the photothermal hydrogen yield is not the simple sum of the photo and thermal effects. This result indicated that the Pt/TiO2 nanoparticles can efficiently couple photo and thermal energy to more effectively drive hydrogen production. As a result, the excellent ability makes it superior to other conventional semiconductor photocatalysts and thermal catalysts. Future works could concentrate on exploring photothermal catalysis as well as the potential synergism between photo and thermal effects to find more efficient hydrogen production technology using the whole solar spectrum.

  7. Bovine kidney alkaline phosphatase. Catalytic properties, subunit interactions in the catalytic process, and mechanism of Mg2+ stimulation.

    PubMed

    Cathala, G; Brunel, C

    1975-08-10

    Kidney alkaline phosphatase is an enzyme which requires two types of metals for maximal activity: zinc, which is essential, and magnesium, which is stimulatory. The main features of the Mg2+ stimulation have been analyzed. The stimulation is pH-dependent and is observed mainly between pH 7.5 and 10.5. Mg2+ binding to native alkaline phosphatase is characterized by a dissociation constant of 50 muM at pH 8.5,25 degrees. Binding of Zn2+ is an athermic process. Both the rate constants of association, ka, and of dissociation, kd, have low values. Typical values are 7 M(-1) at pH 8.0, 25 degrees, for ka and 4.10(-4) S(-1) at pH 8.0, 25 degrees, for kd. The on and off processes have high activation energies of 29 kcal mol (-1). Mg2+ can be replaced at its specific site by Mn2+, Co2+, Ni2+, and Zn2+. Zinc binding to the Mg2+ site inhibits the native alkaline phosphatase. Mn2+, Co2+, and Ni2+ also bind to the Mg2+ site with a stimulatory effect which is nearly identic-al with that of Mg2+, Mn2+ is the stimulatory cation which binds most tightly to the Mg2+ site; the dissociation constant of the Mn2+ kidney phosphatase complex is 2 muM at pH 8.5. The stoichiometry of Mn2+ binding has been found to be 1 eq of Mn2+ per mol of dimeric kidney phosphatase. The native enzyme displays absolute half-site reactivity for Mn2+ binding. Mg2+ binding site and the substrate binding sites are distinct sites. The Mg2+ stimulation corresponds to an allosteric effect. Mg2+ binding to its specific sites does not affect substrate recognition, it selectively affects Vmax values. Quenching of the phosphoenzyme formed under steady state conditions with [32P]AMP as a substrate as well as stopped flow analysis of the catalyzed hydrolysis of 2,4-dinitrophenyl phosphate or p-nitrophenyl phosphate have shown that the two active sites of the native and of the Mg2+-stimulated enzyme are not equivalent. Stopped flow analysis indicated that one of the two active sites was phosphorylated very rapidly

  8. Catalytic liquid-phase oxidation of acetaldehyde to acetic acid over a Pt/CeO2-ZrO2-SnO2/γ-alumina catalyst.

    PubMed

    Choi, Pil-Gyu; Ohno, Takanobu; Masui, Toshiyuki; Imanaka, Nobuhito

    2015-10-01

    Pt/CeO2-ZrO2-SnO2/γ-Al2O3 catalysts were prepared by co-precipitation and wet impregnation methods for catalytic oxidation of acetaldehyde to acetic acid in water. In the present catalysts, Pt and CeO2-ZrO2-SnO2 were successfully dispersed on the γ-Al2O3 support. Dependences of platinum content and reaction time on the selective oxidation of acetaldehyde to acetic acid were investigated to optimize the reaction conditions for obtaining both high acetaldehyde conversion and highest selectivity to acetic acid. Among the catalysts, a Pt(6.4wt.%)/Ce0.68Zr0.17Sn0.15O2.0(16wt.%)/γ-Al2O3 catalyst showed the highest acetaldehyde oxidation activity. On this catalyst, acetaldehyde was completely oxidized after the reaction at 0°C for 8hr, and the selectivity to acetic acid reached to 95% and higher after the reaction for 4hr and longer.

  9. Catalytic performance of PdCl2/Cu-HMS: Influence of hydrophobicity and structure of molecular sieves

    NASA Astrophysics Data System (ADS)

    Zhang, Pingbo; Zhou, Yan; Fan, Mingming; Jiang, Pingping

    2014-03-01

    Surface hydrophobically modified PdCl2/Si-Cu-HMS-m materials were successfully synthesized via a simple silylation process using methyltrichlorosilane and phenyltrichlorosilane respectively. They were characterized by a series of techniques including FT-IR, powder XRD, nitrogen adsorption-desorption, and the contact angle measurement of the water droplet. It was demonstrated that the mesoporous structure of Cu-HMS was retained after modification and that hydrophobicity was enhanced. However, silylation agents had a significant influence on catalytic performance. The experimental results indicated that PdCl2/Si-Cu-HMS-CH3 showed a high catalytic activity for the gas phase oxidative carbonylation of ethanol to diethyl carbonate (DEC) and a small steric hindrance but a weak hydrophobicity in comparison with PdCl2/Si-Cu-HMS-Ben catalyst, demonstrating that catalytic performance was relative to both by-product water and structure of molecular sieves catalyst, but the latter was a main factor in the catalytic system. In addition, a probable mechanism has been proposed to explain this result that structure of molecular sieves was the main factor of influencing catalytic performance.

  10. Effect of calcination temperature on the catalytic activity of nanosized TiO(2) for ozonation of trace 4-chloronitrobenzene.

    PubMed

    Ye, Miaomiao; Chen, Zhonglin; Zhang, Tuqiao; Shao, Weiyun

    2012-01-01

    Nanosized titanium dioxides were synthesized by hydrolysis of TiCl(4) followed by calcination at different temperatures ranging from 300 to 1,000 °C. The as-prepared samples were characterized by X-ray diffraction, N(2) adsorption-desorption, and zeta potential analysis. The catalytic activities of the TiO(2) nanoparticles were tested by catalytic ozonation of trace 4-chloronitrobenzene (4-CNB) in water. Moreover, the catalytic ozonation activity of a sample calcined at 400 °C (denoted as T400) was tested in aqueous solution using electron paramagnetic resonance (EPR) spin trapping technique with 5,5-dimethyl-1-pyrroline N-oxide (DMPO) spin trap. It was found that with increasing calcination temperatures, the average crystallite size and average pore size increased, in contrast the BET surface areas decreased. However, the isoelectric point (IEP) first increased, and then decreased. The ozone adsorption on the catalyst surface played an important role in determining their catalytic activity. Sample T400 with the IEP of 7.0, farthest away from the 4-CNB solution pH value (pH = 5.3), showed the best catalytic activity. The EPR experiments further confirmed that the hydroxyl radicals TiO(2)-catalyzed ozonation followed a radical-type mechanism.

  11. In Situ CO2 Efflux from Leaf Litter Layer Showed Large Temporal Variation Induced by Rapid Wetting and Drying Cycle

    PubMed Central

    Ataka, Mioko; Kominami, Yuji; Yoshimura, Kenichi; Miyama, Takafumi; Jomura, Mayuko; Tani, Makoto

    2014-01-01

    We performed continuous and manual in situ measurements of CO2 efflux from the leaf litter layer (RLL) and water content of the leaf litter layer (LWC) in conjunction with measurements of soil respiration (RS) and soil water content (SWC) in a temperate forest; our objectives were to evaluate the response of RLL to rainfall events and to assess temporal variation in its contribution to RS. We measured RLL in a treatment area from which all potential sources of CO2 except for the leaf litter layer were removed. Capacitance sensors were used to measure LWC. RLL increased immediately after wetting of the leaf litter layer; peak RLL values were observed during or one day after rainfall events and were up to 8.6-fold larger than RLL prior to rainfall. RLL declined to pre-wetting levels within 2–4 day after rainfall events and corresponded to decreasing LWC, indicating that annual RLL is strongly influenced by precipitation. Temporal variation in the observed contribution of RLL to RS varied from nearly zero to 51%. Continuous in situ measurements of LWC and CO2 efflux from leaf litter only, combined with measurements of RS, can provide robust data to clarify the response of RLL to rainfall events and its contribution to total RS. PMID:25271761

  12. In situ CO2 efflux from leaf litter layer showed large temporal variation induced by rapid wetting and drying cycle.

    PubMed

    Ataka, Mioko; Kominami, Yuji; Yoshimura, Kenichi; Miyama, Takafumi; Jomura, Mayuko; Tani, Makoto

    2014-01-01

    We performed continuous and manual in situ measurements of CO2 efflux from the leaf litter layer (R(LL)) and water content of the leaf litter layer (LWC) in conjunction with measurements of soil respiration (RS) and soil water content (SWC) in a temperate forest; our objectives were to evaluate the response of R(LL) to rainfall events and to assess temporal variation in its contribution to R(S). We measured R(LL) in a treatment area from which all potential sources of CO2 except for the leaf litter layer were removed. Capacitance sensors were used to measure LWC. R(LL) increased immediately after wetting of the leaf litter layer; peak R(LL) values were observed during or one day after rainfall events and were up to 8.6-fold larger than R(LL) prior to rainfall. R(LL) declined to pre-wetting levels within 2-4 day after rainfall events and corresponded to decreasing LWC, indicating that annual R(LL) is strongly influenced by precipitation. Temporal variation in the observed contribution of R(LL) to RS varied from nearly zero to 51%. Continuous in situ measurements of LWC and CO2 efflux from leaf litter only, combined with measurements of RS, can provide robust data to clarify the response of R(LL) to rainfall events and its contribution to total R(S).

  13. (Catalytic mechanism of hydrogenase from aerobic N sub 2 -fixing microorganisms)

    SciTech Connect

    Arp, D.J.

    1991-01-01

    The results of this DOE-sponsored project have contributed to our understanding of the catalytic mechanism of A. vinelandii hydrogenase. A group of inhibitors have been characterized. These provide information about the different types of redox clusters involved in catalysis and the roles of each. One group has already used acetylene in a study of three desulfovibrian hydrogenases and shown that only the NiFe hydrogenases are inhibited. We have characterized a number of spectral properties of A. vinelandii hydrogenase. The EPR signals associated with this hydrogenase in the reduced state are reminiscent of other NiFe dimeric hydrogenases such as A. eutrophus, but distinctly difference from others such as D. gigas and Chromatium vinosum. Thus, while the NiFe dimeric hydrogenases are now recognized as a large group of similar enzymes, there are differences in the spectral and catalytic properties which are not explained by their similar redox inventories, identical subunit structures, immunological cross reactivity and conserved sequences. The inhibitors we have characterized are also proving of value in the spectral characterizations. Surprisingly, we only see a significant EP signal attributable to Ni after the enzyme has been inactivated with O{sub 2} and then reduced (though not reactivated). No spectral perterbations (EPR or UV-V is) of active enzyme can be attributed to binding of H{sub 2}, even though H{sub 2} clearly binds to this form of the enzyme. Acetylene, which does not substantially perterb the EPR signal of active hydrogenase, does result in a new absorption envelope in the UV-V is spectrum. Overall, the results of this project have revealed the complex interactions of the redox clusters in catalysis through studies of inhibitor mechanisms and spectral properties. 14 refs., 9 figs.

  14. IDENTIFICATION AND RESPONSES TO POTENTIAL EFFECTS OF SCR AND WET SCRUBBERS ON SUBMICRON PARTICULATE EMISSIONS AND PLUME CHARACTERISTICS

    EPA Science Inventory

    Applications of selective catalytic reduction (SCR) systems and wet flue gas desulfurization (FGD) scrubbers on coal-fired boilers have led to substantial reductions in emissions of nitrogen oxides (NOX) and sulfur dioxide (SO2). However, observations of pilot- and full-scale tes...

  15. IDENTIFICATION AND RESPONSES TO POTENTIAL EFFECTS OF SCR AND WET SCRUBBERS ON SUBMICRON PARTICULATE EMISSIONS AND PLUME CHARACTERISTICS

    EPA Science Inventory

    Applications of selective catalytic reduction (SCR) systems and wet flue gas desulfurization (FGD) scrubbers on coal-fired boilers have led to substantial reductions in emissions of nitrogen oxides (NOX) and sulfur dioxide (SO2). However, observations of pilot- and full-scale tes...

  16. Novel preparation of highly dispersed Ni2P embedded in carbon framework and its improved catalytic performance

    NASA Astrophysics Data System (ADS)

    Wang, Shan; Wang, Kang; Wang, Xitao

    2016-11-01

    Highly dispersed Ni2P embedded in carbon framework with different phosphidation temperature was prepared through carbonizing Ni-alginate gel and followed by phosphidation with PPh3 in liquid phase. The significant effects of phosphidation temperature on Ni2P particle size and catalytic properties for isobutane dehydrogenation to isobutene were investigated. The results showed that Ni2P catalyst derived from the Ni-alginate gel (Ni2P-ADC), consisting of Ni2P particles embedded in carbon walls, possessed smaller particle size and more active site compared with Ni2P catalyst supported on active carbon (Ni2P/AC) prepared by impregnation method. The Ni2P-ADC catalyst phosphorized at 578 K for 3 h exhibited the highest catalytic performance, with the corresponding selectivity of isobutene approaching 89% and conversion approaching 15% after reaction for 4.5 h at 833 K, whereas Ni2P/AC catalyst prepared by impregnation method displays a much lower catalytic activity. The improved catalytic performance of the Ni2P-ADC can be ascribed to the smaller and highly dispersed Ni2P particles incorporated into carbon framework resulting from Ni-alginate gel.

  17. Hierarchical structured MnO2@SiO2 nanofibrous membranes with superb flexibility and enhanced catalytic performance.

    PubMed

    Wang, Xueqin; Dou, Lvye; Yang, Liu; Yu, Jianyong; Ding, Bin

    2017-02-15

    Constructing nanostructured catalyst-embedded ceramic fibrous membranes would facilitate the remediation or preliminary treatment of dyeing wastewater, however, most of such membranes are brittle with low deformation resistance, thus, restricting their widely applications. Herein, the flexible and hierarchical nanostructured MnO2-immobilized SiO2 nanofibrous membranes (MnO2@SiO2 NFM) were fabricated by combining the electrospinning technique with hydrothermal method. The morphologies of membranes could be regulated from nanowires and nanoflower to mace-like structure via varying concentration of reactants. The resultant MnO2@SiO2 NFM could cooperate with hydrogen peroxide to form a Fenton-like reagent for the degradation of methylene blue (MB). The resultant membrane exhibited prominent catalytic performance towards MB, including high degradation degree of 95% within 40min, fast degradation rate of 0.0865min(-1), and excellent reusability in 5 cycles. Moreover, the membranes could be used in a wide pH range of 0 to 14 and the degradation degree reached 76% during dynamic filtration process with a flux of 490,000Lm(-2)h(-1). The successful fabricating of such membrane with extraordinary catalytic performance would provide a platform for preparing high-performance catalysts for remediation of dyeing wastewater. Copyright © 2016 Elsevier B.V. All rights reserved.

  18. Study on the mechanism of NH3-selective catalytic reduction over CuCexZr1-x/TiO2

    NASA Astrophysics Data System (ADS)

    Chen, Xujuan; Sun, Xiaoliang; Gong, Cairong; Lv, Gang; Song, Chonglin

    2016-06-01

    Copper-cerium-zirconium catalysts loaded on TiO2 prepared by a wet impregnation method were investigated for NH3-selective catalytic reduction (SCR) of NOx. The reaction mechanism was proposed on the basis of results from in situ diffuse reflectance infrared transform spectroscopy (DRIFT). When NH3 is introduced, ammonia bonded to Lewis acid sites is more stable over CuCe0.25Zr0.75/TiO2 at high temperature, while Brønsted acid sites are more important than Lewis acid sites at low temperature. For the NH3+NO+O2 co-adsorption, NH3 species occupy most of activity sites on CuCe0.25Zr0.75/TiO2 catalyst, and mainly exist in the forms of NH4 + (at low temperature) and NH3 coordinated (at high temperature), playing a crucial role in the NH3-SCR process. Two different reaction routes, the L-H mechanism at low temperature (< 200°C) and the E-R mechanism at high temperature (> 200°C), are presented for the SCR reaction over CuCe0.25Zr0.75/TiO2 catalyst.

  19. Heterogeneous catalytic oxidation of As(III) on nonferrous metal oxides in the presence of H2O2.

    PubMed

    Kim, Dong-hyo; Bokare, Alok D; Koo, Min suk; Choi, Wonyong

    2015-03-17

    The oxidation of As(III) (arsenite) to As(V) (arsenate), a critical pretreatment process for total arsenic removal, is easily achieved using chemical oxidation methods. Hydrogen peroxide (H2O2) is widely used as an environmentally benign oxidant but its practical use for the arsenite oxidation is limited by the strong pH dependence and slow oxidation kinetics. This study demonstrated that H2O2-induced oxidation of As(III) can be markedly enhanced in the presence of nonferrous metal oxides (e.g., WO3, TiO2, ZrO2) as a heterogeneous catalyst working over a wide pH range in ambient reaction conditions. In particular, TiO2 is an ideal catalyst because it is not only active and stable but also easily available and inexpensive. Although the photocatalytic oxidation of As(III) on TiO2 was intensively studied, the thermal catalytic activities of TiO2 and other nonferrous metal oxides for the arsenic oxidation have been little investigated. The heterogeneous oxidation rate increased with increasing the TiO2 surface area and [H2O2] and weakly depended on pH whereas the homogeneous oxidation by H2O2 alone was favored only at alkaline condition. The oxidation rate in the TiO2/H2O2 system was not reduced at all in the absence of dioxygen. It was not retarded at all by OH radical scavengers but markedly inhibited by hydroperoxyl radical scavengers. It is proposed that the surface complexation of H2O2 on TiO2 induces the generation of the surface hydroperoxyl radical through an inner-sphere electron transfer, which subsequently reacts with As(III). The catalytic activity of TiO2 was maintained without showing any sign of deactivation. The heterogeneous catalytic oxidation is proposed as a viable method for the preoxidation treatment of As(III)-contaminated water under ambient conditions.

  20. Single-step process to prepare CeO2 nanotubes with improved catalytic activity.

    PubMed

    González-Rovira, Leandro; Sánchez-Amaya, José M; López-Haro, Miguel; del Rio, Eloy; Hungría, Ana B; Midgley, Paul; Calvino, José J; Bernal, Serafín; Botana, F Javier

    2009-04-01

    CeO(2) nanotubes have been grown electrochemically using a porous alumina membrane as a template. The resulting material has been characterized by means of scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy, high-angle annular dark-field scanning transmission electron microscopy tomography, high-resolution electron microscopy (HREM), and electron energy loss spectroscopy. According to SEM, the outer diameter of the nanotubes corresponds to the pore size (200 nm) of the alumina membrane, and their length ranges between 30 and 40 microm. HREM images have revealed that the width of the nanotube walls is about 6 nm. The catalytic activity of these novel materials for the CO oxidation reaction is compared to that of a polycrystalline powder CeO(2) sample prepared by a conventional route. The activity of the CeO(2) nanotubes is shown to be in the order of 400 times higher per gram of oxide at 200 degrees C (77.2 x 10(-2) cm(3) CO(2) (STP)/(gxs) for the nanotube-shaped CeO(2) and 0.16 x 10(-2) cm(3) CO(2) (STP)/(gxs) for the powder CeO(2)).

  1. Visible light plasmonic heating of Au-ZnO for the catalytic reduction of CO2

    NASA Astrophysics Data System (ADS)

    Wang, Congjun; Ranasingha, Oshadha; Natesakhawat, Sittichai; Ohodnicki, Paul R.; Andio, Mark; Lewis, James P.; Matranga, Christopher

    2013-07-01

    Plasmonic excitation of Au nanoparticles attached to the surface of ZnO catalysts using low power 532 nm laser illumination leads to significant heating of the catalyst and the conversion of CO2 and H2 reactants to CH4 and CO products. Temperature-calibrated Raman spectra of ZnO phonons show that intensity-dependent plasmonic excitation can controllably heat Au-ZnO from 30 to ~600 °C and simultaneously tune the CH4 : CO product ratio. The laser induced heating and resulting CH4 : CO product distribution agrees well with predictions from thermodynamic models and temperature-programmed reaction experiments indicating that the reaction is a thermally driven process resulting from the plasmonic heating of the Au-ZnO. The apparent quantum yield for CO2 conversion under continuous wave (cw) 532 nm laser illumination is 0.030%. The Au-ZnO catalysts are robust and remain active after repeated laser exposure and cycling. The light intensity required to initiate CO2 reduction is low (~2.5 × 105 W m-2) and achievable with solar concentrators. Our results illustrate the viability of plasmonic heating approaches for CO2 utilization and other practical thermal catalytic applications.Plasmonic excitation of Au nanoparticles attached to the surface of ZnO catalysts using low power 532 nm laser illumination leads to significant heating of the catalyst and the conversion of CO2 and H2 reactants to CH4 and CO products. Temperature-calibrated Raman spectra of ZnO phonons show that intensity-dependent plasmonic excitation can controllably heat Au-ZnO from 30 to ~600 °C and simultaneously tune the CH4 : CO product ratio. The laser induced heating and resulting CH4 : CO product distribution agrees well with predictions from thermodynamic models and temperature-programmed reaction experiments indicating that the reaction is a thermally driven process resulting from the plasmonic heating of the Au-ZnO. The apparent quantum yield for CO2 conversion under continuous wave (cw) 532 nm laser

  2. Fe2O3 particles as superior catalysts for low temperature selective catalytic reduction of NO with NH3.

    PubMed

    Wang, Xiaobo; Gui, Keting

    2013-12-01

    Fe2O3 particle catalysts were experimentally studied in the low temperature selective catalytic reduction (SCR) of NO with NH3. The effects of reaction temperature, oxygen concentration, [NH3]/[NO] molar ratio and residence time on SCR activity were studied. It was found that Fe2O3 catalysts had high activity for the SCR of NO with NH3 in a broad temperature range of 150-270 degrees C, and more than 95% NO conversion was obtained at 180 degrees C when the molar ratio [NH3]/[NO] = 1, the residence time was 0.48 seconds and O2 volume fraction was 3%. In addition, the effect of SO2 on SCR catalytic activity was also investigated at the temperature of 180 degrees C. The results showed that deactivation of the Fe2O3 particles occurred due to the presence of SO2 and the NO conversion decreased from 99.2% to 58% in 240 min, since SO2 gradually decreased the catalytic activity of the catalysts. In addition, X-ray diffraction, Thermogravimetric analysis and Fourier transform infrared spectroscopy were used to characterize the fresh and deactivated Fe2O3 catalysts. The results showed that the deactivation caused by SO2 was due to the formation of metal sulfates and ammonium sulfates on the catalyst surface during the de-NO reaction, which could cause pore plugging and result in suppression of the catalytic activity.

  3. Synergistic Ion-Binding Catalysis Demonstrated via an Enantioselective, Catalytic [2,3]-Wittig Rearrangement

    PubMed Central

    2016-01-01

    Sigmatropic rearrangements number among the most powerful complexity-building transformations in organic synthesis but have remained largely insensitive to enantioselective catalysis due to the diffuse nature of their transition structures. Here, we describe a synergistic ion-binding strategy for asymmetric catalysis of anionic sigmatropic rearrangements. This approach is demonstrated with the enantioselective [2,3]-Wittig rearrangement of α-allyloxy carbonyl compounds to afford highly enantioenriched homoallylic alcohol products. Chiral thiourea catalysts are shown to engage reactive anions and their countercations through a cooperative set of attractive, noncovalent interactions. Catalyst structure–reactivity–selectivity relationship studies and computational analyses provide insight into catalyst–substrate interactions responsible for enantioinduction and allude to the potential generality of this catalytic strategy. PMID:27413786

  4. Bis(imidazolin-2-iminato) rare earth metal complexes: synthesis, structural characterization, and catalytic application.

    PubMed

    Trambitas, Alexandra G; Melcher, Daniel; Hartenstein, Larissa; Roesky, Peter W; Daniliuc, Constantin; Jones, Peter G; Tamm, Matthias

    2012-06-18

    Reaction of anhydrous rare earth metal halides MCl(3) with 2 equiv of 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-imine (Im(Dipp)NH) and 2 equiv of trimethylsilylmethyl lithium (Me(3)SiCH(2)Li) in THF furnished the complexes [(Im(Dipp)N)(2)MCl(THF)(n)] (M = Sc, Y, Lu). The molecular structures of all three compounds were established by single-crystal X-ray diffraction analyses. The coordination spheres around the pentacoordinate metal atoms are best described as trigonal bipyramids. Reaction of YbI(2) with 2 equiv of LiCH(2)SiMe(3) and 2 equiv of the imino ligand Im(Dipp)NH in tetrahydrofuran did not result in a divalent complex, but instead the Yb(III) complex [(Im(Dipp)N)(2)YbI(THF)(2)] was obtained and structurally characterized. Treatment of [(Im(Dipp)N)(2)MCl(THF)(n)] with 1 equiv of LiCH(2)SiMe(3) resulted in the formation of [(Im(Dipp)N)(2)M(CH(2)SiMe(3))(THF)(n)]. The coordination arrangement of these compounds in the solid state at the metal atoms is similar to that found for the starting materials, although the introduction of the neosilyl ligand induces a significantly greater distortion from the ideal trigonal-bipyramidal geometry. [(Im(Dipp)N)(2)Y(CH(2)SiMe(3))(THF)(2)] was used as precatalyst in the intramolecular hydroamination/cyclization reaction of various terminal aminoalkenes and of one aminoalkyne. The complex showed high catalytic activity and selectivity. A comparison with the previously reported dialkyl yttrium complex [(Im(Dipp)N)Y(CH(2)SiMe(3))(2)(THF)(3)] showed no clear tendency in terms of activity.

  5. Catalytic Oxidation of Carbon Black Over Ru/CoxMgyAl2 Catalysts

    NASA Astrophysics Data System (ADS)

    Aoun, Amal; Aouad, Samer; Nakat, John El; Khoury, Bilal El; Aad, Edmond Abi; Aboukaïs, Antoine

    Different catalysts based on ruthenium impregnated on hydrotalcites (Ru/CoxMgyAl2-HT) were prepared by wet impregnation from aqueous nitrosyl nitrate solutions and activated under air at 600 °C for 4 h. The reactivity of the catalysts was evaluated in the oxidation of carbon black (CB). The results showed that the best catalyst decreased the temperature at which the rate of carbon black oxidation is the highest by about 150 °C. This good reactivity was attributed to the formation of easily reducible ruthenium and cobalt oxide species at the surface of the support. The addition of ruthenium made the reduction of surface and bulk cobalt oxides possible at lower temperatures.

  6. Spliceosomal snRNAs: Mg(2+)-dependent chemistry at the catalytic core?

    PubMed

    Villa, Tommaso; Pleiss, Jeffrey A; Guthrie, Christine

    2002-04-19

    Since the discovery of self-splicing RNAs, it has been suspected that the snRNAs are the catalytic components of the spliceosome. Recent evidence supports both the catalytic potential of the spliceosomal snRNAs and their resemblance to elements of group II introns.

  7. Synthesis of nanostructured framework of novel ZnBaO2 nanopowder via wet chemical approach and hepatocytotoxicity response

    NASA Astrophysics Data System (ADS)

    Athar, Taimur; Vishwakarma, Sandeep Kumar; Alabass, Razzaq; Alqaralosy, Ahmed; Khan, Aleem Ahmed

    2016-08-01

    Wet synthetic process is an effective and facile method at low cost, environmentally benign process for easy scaling-up and then used for fabrication of multi-utility devices. Self-assembling of nanobrick leads to architecture framework with new functional properties which help to make its vast applications as nanodevices with their intrinsic shape, size and functional properties. The bimetallic oxide nanostructure with phase structure was characterized by FTIR, UV-visible electronic absorption, XRD, thermal studies, SEM, TEM, DLS and fluorescence. Nanocrystalline ZnBaO2 powder can be used due to its chemical stability and excellent transmission in the visible region. It was observed that the annealing rate plays an important role to redefine the structural and other physicochemical properties which finally help to change gel into crystalline functional properties with porosity. Wet chemical approach can be used for the synthesis of other metal oxide nanopowders which can be easily scale up for production level. Along with synthesis and characterization, we also assessed biological responses of human hepatocytes exposed to ZnBaO2 nanopowder. Cell membrane permeability and ammonia detoxification were investigated against various concentrations of nanoparticles on in vitro cultured hepatocytes. Our results suggest that low concentrations (<40 μg/ml) of ZnBaO2 nanopowder have no cytotoxic effect on hepatocytes viability, proliferation and detoxification, whereas concentrations above 40 μg/ml depict significant toxicity on cells.

  8. Methodology to assay CYP2E1 mixed function oxidase catalytic activity and its induction

    PubMed Central

    Cederbaum, Arthur I.

    2014-01-01

    The cytochrome P450 mixed function oxidase enzymes are the major catalysts involved in drug metabolism. There are many forms of P450. CYP2E1 metabolizes many toxicologically important compounds including ethanol and is active in generating reactive oxygen species. Since several of the contributions in the common theme series “Role of CYP2E1 and Oxidative/Nitrosative Stress in the Hepatotoxic Actions of Alcohol” discuss CYP2E1, this methodology review describes assays on how CYP2E1 catalytic activity and its induction by ethanol and other inducers can be measured using substrate probes such as the oxidation of para-nitrophenol to para-nitrocatechol and the oxidation of ethanol to acetaldehyde. Approaches to validate that a particular reaction e.g. oxidation of a drug or toxin is catalyzed by CYP2E1 or that induction of that reaction is due to induction of CYP2E1 are important and specific examples using inhibitors of CYP2E1, anti-CYP2E1 IgG or CYP2E1 knockout and knockin mice will be discussed. PMID:25454746

  9. High NO2/NOx emissions downstream of the catalytic diesel particulate filter: An influencing factor study.

    PubMed

    He, Chao; Li, Jiaqiang; Ma, Zhilei; Tan, Jianwei; Zhao, Longqing

    2015-09-01

    Diesel vehicles are responsible for most of the traffic-related nitrogen oxide (NOx) emissions, including nitric oxide (NO) and nitrogen dioxide (NO2). The use of after-treatment devices increases the risk of high NO2/NOx emissions from diesel engines. In order to investigate the factors influencing NO2/NOx emissions, an emission experiment was carried out on a high pressure common-rail, turbocharged diesel engine with a catalytic diesel particulate filter (CDPF). NO2 was measured by a non-dispersive ultraviolet analyzer with raw exhaust sampling. The experimental results show that the NO2/NOx ratios downstream of the CDPF range around 20%-83%, which are significantly higher than those upstream of the CDPF. The exhaust temperature is a decisive factor influencing the NO2/NOx emissions. The maximum NO2/NOx emission appears at the exhaust temperature of 350°C. The space velocity, engine-out PM/NOx ratio (mass based) and CO conversion ratio are secondary factors. At a constant exhaust temperature, the NO2/NOx emissions decreased with increasing space velocity and engine-out PM/NOx ratio. When the CO conversion ratios range from 80% to 90%, the NO2/NOx emissions remain at a high level.

  10. Simultaneous treatment of NO and SO2 with aqueous NaClO2 solution in a wet scrubber combined with a plasma electrostatic precipitator.

    PubMed

    Park, Hyun-Woo; Choi, Sooseok; Park, Dong-Wha

    2015-03-21

    NO and SO2 gases that are generally produced in thermal power plants and incinerators were simultaneously removed by using a wet scrubber combined with a plasma electrostatic precipitator. The wet scrubber was used for the absorption and oxidation of NO and SO2, and non-thermal plasma was employed for the electrostatic precipitation of aerosol particles. NO and SO2 gases were absorbed and oxidized by aerosol particles of NaClO2 solution in the wet scrubber. NO and SO2 reacted with the generated NaClO2 aerosol particles, NO2 gas, and aqueous ions such as NO2(-), NO3(-), HSO3(-), and SO4(2-). The aerosol particles were negatively charged and collected on the surface of grounded anode in the plasma electrostatic precipitator. The NO and SO2 removal efficiencies of the proposed system were 94.4% and 100% for gas concentrations of 500 mg/m(3) and a total gas flow rate of 60 Nm(3)/h, when the molar flow rate of NaClO2 and the gas-liquid contact time were /min and 1.25 s, respectively. The total amount and number of aerosol particles in the exhaust gas were reduced to 7.553 μg/m(3) and 210/cm(3) at the maximum plasma input power of 68.8 W, which are similar to the values for clean air. Copyright © 2014 Elsevier B.V. All rights reserved.

  11. Role of photon emission for the increase of catalytic activity of SiO2 and zirconium polyphosphates

    NASA Astrophysics Data System (ADS)

    Gul'yanova, S. G.; Samuilova, O. K.; Chechlova, T. K.

    1997-08-01

    The influence of the monochromatic light with different wavelength on the catalytic activity and selectivity of SiO2 and zirconium polyphosphates was studied. It was shown that the wavelength of the falling irradiation differently influence on the rates of isopropyl alcohol dehydration and dehydrogenation on SiO2 surface. The influence of the falling irradiation on the catalytic activity and selectivity of zirconium polyphosphates in the reaction of isopropyl alcohol conversion depends both on the wavelength of the falling irradiation and the composition of the samples. The change of the catalytic properties was explained by the selective influence of the short-wave irradiation on the structural water state and the variation of the number and condition of active centers of the catalysts surface during the exposure.

  12. Mechanical bending induced catalytic activity enhancement of monolayer 1 T'-MoS2 for hydrogen evolution reaction

    NASA Astrophysics Data System (ADS)

    Shi, Wenwu; Wang, Zhiguo; Fu, Yong Qing

    2017-09-01

    In this paper, mechanisms behind enhancement of catalytic activity of MoS2 mono-layer (three atomic layers) for hydrogen evolution reaction (HER) by mechanically applying bending strain were investigated using density functional theory. Results showed that with the increase of bending strains, the Gibbs free energy for hydrogen adsorption on the MoS2 mono-layer was decreased from 0.18 to -0.04 eV and to 0.13 eV for the bend strains applied along the zigzag and armchair directions, respectively. The mechanism for the enhanced catalytic activity comes from the changes of density of electronic states near the Fermi energy level, which are induced by the changes of the Mo-S and Mo-Mo bonds upon bending. This report provides a new design methodology to improve the catalytic activity of catalysts based on two-dimensional transition metal dichalcogenides through a simple mechanical bending.

  13. Structure, bonding, and catalytic activity of monodisperse, transition-metal-substituted CeO2 nanoparticles.

    PubMed

    Elias, Joseph S; Risch, Marcel; Giordano, Livia; Mansour, Azzam N; Shao-Horn, Yang

    2014-12-10

    We present a simple and generalizable synthetic route toward phase-pure, monodisperse transition-metal-substituted ceria nanoparticles (M0.1Ce0.9O2-x, M = Mn, Fe, Co, Ni, Cu). The solution-based pyrolysis of a series of heterobimetallic Schiff base complexes ensures a rigorous control of the size, morphology and composition of 3 nm M0.1Ce0.9O2-x crystallites for CO oxidation catalysis and other applications. X-ray absorption spectroscopy confirms the dispersion of aliovalent (M(3+) and M(2+)) transition metal ions into the ceria matrix without the formation of any bulk transition metal oxide phases, while steady-state CO oxidation catalysis reveals an order of magnitude increase in catalytic activity with copper substitution. Density functional calculations of model slabs of these compounds confirm the stabilization of M(3+) and M(2+) in the lattice of CeO2. These results highlight the role of the host CeO2 lattice in stabilizing high oxidation states of aliovalent transition metal dopants that ordinarily would be intractable, such as Cu(3+), as well as demonstrating a rational approach to catalyst design. The current work demonstrates, for the first time, a generalizable approach for the preparation of transition-metal-substituted CeO2 for a broad range of transition metals with unparalleled synthetic control and illustrates that Cu(3+) is implicated in the mechanism for CO oxidation on CuO-CeO2 catalysts.

  14. Catalytic hydrolysis of COS over CeO2 (110) surface: A density functional theory study

    NASA Astrophysics Data System (ADS)

    Song, Xin; Ning, Ping; Wang, Chi; Li, Kai; Tang, Lihong; Sun, Xin

    2017-08-01

    Density functional theory (DFT) calculations were performed to investigate the reaction pathways for catalytic hydrolysis of COS over CeO2 (110) surface using Dmol3 model. The thermodynamic stability analysis for the suggested routes of COS hydrolysis to CO2 and H2S was evaluated. The absolute values of adsorption energy of H2O-CeO2 are higher than that of COS-CeO2. Meanwhile, the adsorption energy and geometries show that H2O is easier adsorbed on the surface of CeO2 (110) than COS. H2O plays a role as a bridge in the process of joint adsorption. H2O forms more Cesbnd Osbnd H groups on the CeO2 (110) surface. CeO2 decreases the maximum energy barrier by 76.15 kcal/mol. The migration of H from H2O to COS is the key for the hydrolysis reaction. Csbnd O channel is easier to occur than Csbnd S channel. Experimental result shows that adding of CeO2 can increase COS removal rate and prolong the 100% COS removal rate from 180 min to 210 min. The difference between Fe2O3 and CeO2 for the hydrolysis of COS is characterized in the atomic charge transfer and the formation of Hsbnd O bond and Hsbnd S bond. The transfer effect of H in H2O to S in COS over CeO2 decreases the energy barriers of hydrolysis reaction, and enhances the reaction activity of COS hydrolysis.

  15. Synthesis, characterization, electronic structure and catalytic activity of new ruthenium carbonyl complexes of N-[(2-pyridyl)methylidene]-2-aminothiazole

    NASA Astrophysics Data System (ADS)

    Kundu, Subhankar; Sarkar, Deblina; Jana, Mahendra Sekhar; Pramanik, Ajoy Kumar; Jana, Subrata; Mondal, Tapan Kumar

    2013-03-01

    Reaction of ruthenium carbonyls, [Ru(CO)2Cl2]n/[Ru(CO)4I2] with bidentate Schiffs base ligands derived by the condensation of pyridine-2-carboxaldehyde with 2-aminothiazole in a 1:1 mole ratio in acetonitrile led to the formation of complexes having general formula [Ru(CO)2(L)X2] (X = Cl (1) and I (2)) (L = N-[(2-pyridyl)methylidene]-2-aminothiazole). The compounds have been characterized by various analytical and spectroscopic (IR, electronic and 1H NMR) studies. In acetonitrile solution the complexes exhibit a weak broad metal-ligand to ligand charge transfer (MLLCT) band along with ILCT transitions. The compounds are emissive in room temperature upon excitation in the ILCT band. The complexes exhibit a quasi-reversible one electron Ru(II)/Ru(III) oxidation couple at 1.44 V for 1 and 0.94 V for 2. Catalytic activity of these compounds is investigated to the oxidation of PhCH2OH to PhCHO, 2-butanol (C4H9OH) to 2-butanone, 1-phenylethanol (PhC2H4OH) to acetophenone, cyclopentanol (C5H9OH) to cyclopentanone, cyclohexanol to cyclohexanone, cycloheptanol to cycloheptanone and cycloctanol to cycloctanone using N-methylmorpholine-N-oxide (NMO) as oxidant. The catalytic efficiency of 2 is greater than complex 1 and well correlate with the metal oxidation potential of the complexes. DFT, NBO and TDDFT calculations are employed to explain the structural and electronic features and to support the spectroscopic assignments.

  16. Identification and Characterization of an Alternatively Spliced Isoform of the Human Protein Phosphatase 2Catalytic Subunit*

    PubMed Central

    Migueleti, Deivid L. S.; Smetana, Juliana H. C.; Nunes, Hugo F.; Kobarg, Jörg; Zanchin, Nilson I. T.

    2012-01-01

    PP2A is the main serine/threonine-specific phosphatase in animal cells. The active phosphatase has been described as a holoenzyme consisting of a catalytic, a scaffolding, and a variable regulatory subunit, all encoded by multiple genes, allowing for the assembly of more than 70 different holoenzymes. The catalytic subunit can also interact with α4, TIPRL (TIP41, TOR signaling pathway regulator-like), the methyl-transferase LCMT-1, and the methyl-esterase PME-1. Here, we report that the gene encoding the catalytic subunit PP2Acα can generate two mRNA types, the standard mRNA and a shorter isoform, lacking exon 5, which we termed PP2Acα2. Higher levels of the PP2Acα2 mRNA, equivalent to the level of the longer PP2Acα mRNA, were detected in peripheral blood mononuclear cells that were left to rest for 24 h. After this time, the peripheral blood mononuclear cells are still viable and the PP2Acα2 mRNA decreases soon after they are transferred to culture medium, showing that generation of the shorter isoform depends on the incubation conditions. FLAG-tagged PP2Acα2 expressed in HEK293 is catalytically inactive. It displays a specific interaction profile with enhanced binding to the α4 regulatory subunit, but no binding to the scaffolding subunit and PME-1. Consistently, α4 out-competes PME-1 and LCMT-1 for binding to both PP2Acα isoforms in pulldown assays. Together with molecular modeling studies, this suggests that all three regulators share a common binding surface on the catalytic subunit. Our findings add important new insights into the complex mechanisms of PP2A regulation. PMID:22167190

  17. Pd-catalytic hydrodechlorination of chlorinated hydrocarbons in groundwater using H2 produced by a dual-anode system.

    PubMed

    Xie, Shiwei; Yuan, Songhu; Liao, Peng; Jia, Mengqi; Wang, Yin

    2015-12-01

    Water electrolysis has been employed for in situ supplying H2 to Pd-catalytic treatment of groundwater, but the treatment efficiency is greatly inhibited by the concomitant production of O2. In this study, a new dual-anode system is proposed to improve the efficiency. An inert anode and an iron anode are used simultaneously to produce O2 and Fe(II), respectively. The quick oxidative precipitation of Fe(II) by O2 removes both Fe(II) and O2, improving the utilization of cathodic H2 for the subsequent Pd-catalytic hydrodechlorination. Feasibility tests in the lab show that Pd-catalytic hydrodechlorination of trichloroethylene (TCE) was considerably increased by the addition of an iron anode to the conventional two-electrode system. Scale-up tests at an abandoned chemical site demonstrated that chlorobenzenes in the groundwater were largely hydrodechlorinated to benzene, showing a maximum efficiency with the currents of 0.24 and 0.16 A applied to the inert and iron anodes, respectively, at the flow rate of 6 L/h. In a 3-month intermittent field test, Pd normalized rate constants of hydrodechlorinating three chlorobenzenes are comparable to the conventional means of H2 supply, while the cost for hydrodechlorination normalized by one mole [H] is much lower. The dual-anode system is an effective means to supplying H2 in situ for Pd-catalytic treatment. Copyright © 2015 Elsevier Ltd. All rights reserved.

  18. Anchoring noble metal nanoparticles on CeO2 modified reduced graphene oxide nanosheets and their enhanced catalytic properties.

    PubMed

    Ji, Zhenyuan; Shen, Xiaoping; Xu, Yuling; Zhu, Guoxing; Chen, Kangmin

    2014-10-15

    The strategy of structurally integrating noble metal, metal oxide, and graphene is expected to offer prodigious opportunities toward emerging functions of graphene-based nanocomposites. In this study, we develop a facile two-step approach to disperse noble metal (Pt and Au) nanoparticles on the surface of CeO2 functionalized reduced graphene oxide (RGO) nanosheets. It is shown that Pt and Au with particle sizes of about 5 and 2nm are well dispersed on the surface of RGO/CeO2. The reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by NaBH4 was used as a model reaction to quantitatively evaluate the catalytic properties of the as-synthesized RGO/Pt/CeO2 and RGO/Au/CeO2 ternary nanocomposites. In such triple-component catalysts, CeO2 nanocrystals provide unique and critical roles for optimizing the catalytic performance of noble metallic Pt and Au, allowing them to express enhanced catalytic activities in comparison with RGO/Pt and RGO/Au catalysts. In addition, a possible mechanism for the enhanced catalytic activities of the RGO/Pt/CeO2 and RGO/Au/CeO2 ternary catalysts in the reduction of 4-NP is proposed. It is expected that our prepared graphene-based triple-component composites, which inherit peculiar properties of graphene, metal oxide, and noble metal, are attractive candidates for catalysis and other applications.

  19. Catalytic Reforming

    SciTech Connect

    Little, D.M.

    1985-01-01

    Don Little's Catalytic Reforming deals exclusively with reforming. With the increasing need for unleaded gasoline, the importance of this volume has escalated since it combines various related aspects of reforming technology into a single publication. For those with no practical knowledge of catalytic reforming, the chemical reactions, flow schemes and how the cat reformer fits into the overall refinery process will be of interest. Contents include: Catalytic reforming in refinery processing: How catalytic reformers work - chemical reactions; Process design; The catalyst, process variables and unit operation; Commercial processes; BTX operation; Feed preparation; naphtha hydrotreating and catalytic reforming; Index.

  20. Mixing in a three-phase system: Enhanced production of oil-wet reservoirs by CO2 injection

    NASA Astrophysics Data System (ADS)

    Jiménez-Martínez, Joaquín.; Porter, Mark L.; Hyman, Jeffrey D.; Carey, J. William; Viswanathan, Hari S.

    2016-01-01

    We recreate three-phase reservoir conditions (high-pressure/temperature) using a microfluidics system and show that the use of scCO2 for restimulation operations, such as hydraulic fracturing, can enhance mixing and production. The results inform hydrocarbon extraction from deep shale formations, which has recently generated an energy boom that has lowered hydrocarbon costs. However, production decreases rapidly and methods to increase efficiency or allow restimulation of wells are needed. In our experiments, the presence of residual brine from initial production creates spatiotemporal variability in the system that causes the injected scCO2 to more effectively interact-mix with trapped hydrocarbon, thereby increasing recovery. We apply volume-averaging techniques to upscale brine saturation, which allows us to analyze the complex three-phase system in the framework of well characterized two-phase systems. The upscaled three-phase system behaves like a two-phase system: greater mixing with larger non-wetting content and higher heterogeneity. The results are contrary to previous observations in water-wet systems.

  1. Visible light plasmonic heating of Au-ZnO for the catalytic reduction of CO2

    DOE PAGES

    Wang, Congjun; Ranasingha, Oshadha; Natesakhawat, Sittichai; ...

    2013-01-01

    Plasmonic excitation of Au nanoparticles attached to the surface of ZnO catalysts using low power 532 nm laser illumination leads to significant heating of the catalyst and the conversion of CO2 and H2 reactants to CH4 and CO products. Temperature-calibrated Raman spectra of ZnO phonons show that intensity-dependent plasmonic excitation can controllably heat Au–ZnO from 30 to ~600 °C and simultaneously tune the CH4 : CO product ratio. The laser induced heating and resulting CH4 : CO product distribution agrees well with predictions from thermodynamic models and temperature-programmed reaction experiments indicating that the reaction is a thermally driven process resultingmore » from the plasmonic heating of the Au-ZnO. The apparent quantum yield for CO2 conversion under continuous wave (cw) 532 nm laser illumination is 0.030%. The Au-ZnO catalysts are robust and remain active after repeated laser exposure and cycling. The light intensity required to initiate CO2 reduction is low ( ~2.5 x 105 W m-2) and achievable with solar concentrators. Our results illustrate the viability of plasmonic heating approaches for CO2 utilization and other practical thermal catalytic applications.« less

  2. Probing the Catalytic Potential of the Hamster Arylamine N-Acetyltransferase 2 Catalytic Triad by Site-directed Mutagenesis of the Proximal Conserved Residue, Tyrosine 190

    PubMed Central

    Zhou, Xin; Zhang, Naixia; Liu, Li; Walters, Kylie J.; Hanna, Patrick E.; Wagner, Carston R.

    2009-01-01

    Summary Arylamine N-acetyltransferases (NATs) play an important role in both detoxification of arylamine and hydrazine drugs and activation of arylamine carcinogens. Since the catalytic triad, Cys-His-Asp, of mammalian NATs has been shown to be essential for maintaining protein stability, rendering it impossible to assess alterations of the triad on catalysis, we explored the impact of the highly conserved proximal residue, Tyr-190, which forms a direct hydrogen bond interaction with one of the triad residues, Asp-122, as well as a potential pi-pi stacking interaction with the active site His-107. Replacement of Hamster NAT2 Tyr-190 by either phenylalanine, isoleucine, or alanine was well tolerated and did not result in significant alterations in the overall fold of the protein. Nevertheless, stopped-flow and steady-state kinetic analysis revealed that Tyr-190 was critical for maximizing the acetylation rate of NAT2 and the transacetylation rate of p-aminobenzoic acid (PABA) when compared to wild type. Tyr-190 was also shown to play an important role in determining the pKa of the active site cysteine during acetylation, as well as the pH versus rate profile for transacetylation. We hypothesized that the pH-dependence was associated with global changes in the active site structure, which was revealed by the superposition of [1H, 15N] HSQC spectra for wild type and Y190A. These results suggest that NAT2 catalytic efficiency is partially governed by the ability of Tyr-190 to mediate the collective impact of multiple side chains on the electrostatic potential and local conformation of active site. PMID:19860825

  3. Additives affecting properties of β-Li2TiO3 pebbles in a modified indirect wet chemistry process

    NASA Astrophysics Data System (ADS)

    Yu, Cheng-Long; Liu, Wei; Yang, Long-Tao; Wang, Dao-Yi; Wu, Kang; Zhang, Zeng-Ping; Wang, Xiu-Feng; Yanagisawa, Kazumichi

    2016-11-01

    Lithium metatitanate (β-Li2TiO3) pebbles were fabricated via the modified indirect wet chemistry method. Effect of varied additives, as polyvinyl alcohol, glycerol, and agar on the properties evolution was investigated. The highest density is obtained by adding 2 wt% (weight percent) polyvinyl alcohol, 3 wt% glycerol, and 3 wt% agar, respectively. β-Li2TiO3 pebbles with relative sintered density of 92.4%T.D. (Theoretical Density), the ratio of the intensity of diffraction peak (002) to that of (-133) of about 2.93, about 1.58 mm in diameter, a better sphericity of 1.02, the particle size of 5-6 μm, and the well-developed surface layered structure are successfully fabricated with 3 wt% glycerol. Glycerol is beneficial to improving the properties by other fabrication method as well.

  4. Designing CuOx Nanoparticle-Decorated CeO2 Nanocubes for Catalytic Soot Oxidation: Role of the Nanointerface in the Catalytic Performance of Heterostructured Nanomaterials.

    PubMed

    Sudarsanam, Putla; Hillary, Brendan; Mallesham, Baithy; Rao, Bolla Govinda; Amin, Mohamad Hassan; Nafady, Ayman; Alsalme, Ali M; Reddy, B Mahipal; Bhargava, Suresh K

    2016-03-08

    This work investigates the structure-activity properties of CuOx-decorated CeO2 nanocubes with a meticulous scrutiny on the role of the CuOx/CeO2 nanointerface in the catalytic oxidation of diesel soot, a critical environmental problem all over the world. For this, a systematic characterization of the materials has been undertaken using transmission electron microscopy (TEM), transmission electron microscopy-energy-dispersive X-ray spectroscopy (TEM-EDS), high-angle annular dark-field-scanning transmission electron microscopy (HAADF-STEM), scanning transmission electron microscopy-electron energy loss spectroscopy (STEM-EELS), X-ray diffraction (XRD), Raman, N2 adsorption-desorption, and X-ray photoelectron spectroscopy (XPS) techniques. The TEM images show the formation of nanosized CeO2 cubes (∼25 nm) and CuOx nanoparticles (∼8.5 nm). The TEM-EDS elemental mapping images reveal the uniform decoration of CuOx nanoparticles on CeO2 nanocubes. The XPS and Raman studies show that the decoration of CuOx on CeO2 nanocubes leads to improved structural defects, such as higher concentrations of Ce(3+) ions and abundant oxygen vacancies. It was found that CuOx-decorated CeO2 nanocubes efficiently catalyze soot oxidation at a much lower temperature (T50 = 646 K, temperature at which 50% soot conversion is achieved) compared to that of pristine CeO2 nanocubes (T50 = 725 K) under tight contact conditions. Similarly, a huge 91 K difference in the T50 values of CuOx/CeO2 (T50 = 744 K) and pristine CeO2 (T50 = 835 K) was found in the loose-contact soot oxidation studies. The superior catalytic performance of CuOx-decorated CeO2 nanocubes is mainly attributed to the improved redox efficiency of CeO2 at the nanointerface sites of CuOx-CeO2, as evidenced by Ce M5,4 EELS analysis, supported by XRD, Raman, and XPS studies, a clear proof for the role of nanointerfaces in the performance of heterostructured nanocatalysts.

  5. Combustion of CH4/H2/air mixtures in catalytic microreactors.

    PubMed

    Specchia, Stefania; Vella, Luigi D; Burelli, Sara; Saracco, Guido; Specchia, Vito

    2009-03-23

    The combustion of CH(4)/H(2)/HC mixtures in a very small space represents an alternative, innovative way to produce thermal/electrical energy. Pd/NiCrO(4) catalysts are lined on SiC monoliths via in situ solution combustion synthesis (SCS), and the monoliths are then tested by feeding CH(4), H(2), and lean CH(4)/H(2) mixtures into a lab-scale test rig at an output thermal power of 7.6 MW(th) m(-3). In all cases, the combustion temperature shifts to values lower than those observed in non-catalytic combustion. When the power density is kept constant (by adding H(2) to the gas mixture), the value of CH(4)-T(50) (the half-conversion temperature of CH(4)) decreases relative to that of pure CH(4), and the slope of the conversion curve becomes steeper. The higher the H(2) concentration is, the higher the reactivity of the mixture towards CH(4) oxidation-probably due to a higher production of H(2) reactive radicals (OH).

  6. Silica-supported Au@hollow-SiO2 particles with outstanding catalytic activity prepared via block copolymer template approach.

    PubMed

    Shajkumar, Aruni; Nandan, Bhanu; Sanwaria, Sunita; Albrecht, Victoria; Libera, Marcin; Lee, Myong-Hoon; Auffermann, Gudrun; Stamm, Manfred; Horechyy, Andriy

    2017-04-01

    Catalytically active Au@hollow-SiO2 particles embedded in porous silica support (Au@hollow-SiO2@PSS) were prepared by using spherical micelles from poly(styrene)-block-poly(4-vinyl pyridine) block copolymer as a sacrificial template. Drastic increase of the shell porosity was observed after pyrolytic removal of polymeric template because the stretched poly(4-vinyl pyridine) chains interpenetrating with silica shell acted as an effective porogen. The embedding of Au@hollow-SiO2 particles in porous silica support prevented their fusion during pyrolysis. The catalytic activity of Au@hollow-SiO2@PSS was investigated using a model reaction of catalytic reduction of 4-nitrophenol and reductive degradation of Congo red azo-dye. Significantly, to the best of our knowledge, Au@hollow-SiO2@PSS catalyst shows the highest activity among analogous systems reported till now in literature. Such high activity was attributed to the presence of multiple pores within silica shell of Au@hollow-SiO2 particles and easy accessibility of reagents to the catalytically active sites of the ligand-free gold surface through the porous silica support.

  7. Catalytic Deoxygenation of 1,2-Propanediol to Give n-Propanol

    SciTech Connect

    Schlaf, Marcel; Ghosh, Prasenjit; Fagan, Paul J.; Hauptman, Elisabeth; Bullock, R. Morris

    2009-03-01

    Catalytic deoxygenation of 1,2-propanediol has been studied as a model the for deoxygenation of polyols and other biomass-derived compounds. Deoxygenation of 1,2-propanediol (1.0 M in sulfolane) catalyzed by {[Cp*Ru(CO)2]2(μ-H)}+OTf – (0.5 mol %) at 110 °C under H2 (750 psi) in the presence of HOTf (60 mM) gives n-propanol (54 %) as the major product, indicating a high selectivity for deoxygenation of the internal OH over the terminal OH of the diol. Di-n propyl ether forms through condensation of n-propanol with itself, and propylene glycol propyl ether arises from condensation of n-propanol with the starting material diol, giving a total of up to 80 % yield for deoxygenation / hydrogenation products under these conditions. The deoxygenation of 1,2-propanediol is strongly influenced by the concentration of acid, giving faster rates and proceeding to higher conversions as the concentration of HOTf is increased. There is little or no dependence of the rate on the pressure of H2. Propionaldehyde was observed as an intermediate, being formed through acid-catalyzed dehydration of 1,2-propanediol. This aldehyde is hydrogenated to n-propanol through an ionic pathway involving protonation of the aldehyde, followed by hydride transfer from the neutral hydride, Cp*Ru(CO)2H. The proposed mechanism for the deoxygenation/hydrogenation reaction involves formation of a highly acidic dihydrogen complex, [Cp*Ru(CO)22-H2)]+OTf-. Regeneration of the dihydrogen complex occurs through reaction of Cp*Ru(CO)2OTf with H2. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

  8. Aerobic oxidative amidation of aromatic and cinnamic aldehydes with secondary amines by CuI/2-pyridonate catalytic system.

    PubMed

    Zhu, Mingwen; Fujita, Ken-ichi; Yamaguchi, Ryohei

    2012-10-19

    A simple and convenient CuI/2-pyridonate catalytic system for the oxidative amidation of aldehydes with secondary amines has been developed. With this system, a variety of useful arylamides have been synthesized in moderate to good yields in the presence of small amount of copper catalyst and the pyridonate ligand, generating only water as a coproduct. Synthesis of cinnamamides was also achieved by the reactions of cinnamaldehydes with secondary amines in moderate yields. Air was successfully employed as a green oxidant in this catalytic system, achieving a safe and atom-efficient system for the synthesis of amides.

  9. A Bioinspired Catalytic Aerobic Oxidative C–H Functionalization of Primary Aliphatic Amines: Synthesis of 1,2-Disubstituted Benzimidazoles

    PubMed Central

    Nguyen, Khac Minh Huy; Largeron, Martine

    2015-01-01

    Aerobic oxidative C–H functionalization of primary aliphatic amines has been accomplished with a biomimetic cooperative catalytic system to furnish 1,2-disubstituted benzimidazoles that play an important role as drug discovery targets. This one-pot atom-economical multistep process, which proceeds under mild conditions, with ambient air and equimolar amounts of each coupling partner, constitutes a convenient environmentally friendly strategy to functionalize non-activated aliphatic amines that remain challenging substrates for non-enzymatic catalytic aerobic systems. PMID:26206475

  10. Selective catalytic reduction of NO{sub 2} with urea in nanocrystalline NaY zeolite

    SciTech Connect

    Gonghu Li; Conrad A. Jones; Vicki H. Grassian; Sarah C. Larsen

    2005-09-10

    In this study, the selective catalytic reduction (SCR) of NO{sub 2} with urea in nanocrystalline NaY zeolite was investigated with in situ transmission Fourier transform infrared (FTIR) spectroscopy and solid-state nuclear magnetic resonance spectroscopy. At T=473 K, the reaction rate for urea-SCR of NO{sub 2} in nanocrystalline NaY zeolite was significantly greater than that in commercial NaY zeolite with a larger crystal size. In addition, a dramatic decrease in the concentration of undesirable surface species, including biuret and cyanuric acid, was observed in nanocrystalline NaY compared with commercial NaY after urea-SCR of NO{sub 2} at T=473 K. The increased reactivity for urea-SCR of NO{sub 2} was attributed to silanol groups and extra-framework aluminum species located on the external surface of nanocrystalline NaY. Specifically, NOx storage as nitrate and nitrite on the internal zeolite surface was coupled to reactive deNOx sites on the external surface. Isotopic labeling combined with IR analysis suggest that NN bond formation involved both an N-atom originating from NO{sub 2} and an N-atom originating from urea. This is the first clear example demonstrating that the increased external surface area (up to 40% of total surface area) of nanocrystalline zeolites can be used as a reactive surface with unique active sites for catalysis.

  11. Catalytic Activity of Human Indoleamine 2,3-Dioxygenase (hIDO1) at Low Oxygen

    PubMed Central

    Kolawole, Ayodele O.; Hixon, Brian P.; Dameron, Laura S.; Chrisman, Ian M.; Smirnov, Valeriy V.

    2015-01-01

    A cytokine-inducible extrahepatic human indoleamine 2,3-dioxygenase (hIDO1) catalyzes the first step of the kynurenine pathway. Immunosuppressive activity of hIDO1 in tumor cells weakens host T-cell immunity, contributing to the progression of cancer. Here we report on enzyme kinetics and catalytic mechanism of hIDO1, studied at varied levels of dioxygen (O2) and L-tryptophan (L-Trp). Using a cytochrome b5-based activating system, we measured the initial rates of O2 decay with a Clark-type oxygen electrode at physiologically-relevant levels of both substrates. Kinetics was also studied in the presence of two substrate analogs: 1-methyl-L-tryptophan and norharmane. Quantitative analysis supports a steady-state rather than a rapid equilibrium kinetic mechanism, where the rates of individual pathways, leading to a ternary complex, are significantly different, and the overall rate of catalysis depends on contributions of both routes. One path, where O2 binds to ferrous hIDO1 first, is faster than the second route, which starts with the binding of L-Trp. However, L-Trp complexation with free ferrous hIDO1 is more rapid than that of O2. As the level of L-Trp increases, the slower route becomes a significant contributor to the overall rate, resulting in observed substrate inhibition. PMID:25712221

  12. In situ catalytic growth of large-area multilayered graphene/MoS2 heterostructures

    NASA Astrophysics Data System (ADS)

    Fu, Wei; Du, Fei-Hu; Su, Juan; Li, Xin-Hao; Wei, Xiao; Ye, Tian-Nan; Wang, Kai-Xue; Chen, Jie-Sheng

    2014-04-01

    Stacking various two-dimensional atomic crystals on top of each other is a feasible approach to create unique multilayered heterostructures with desired properties. Herein for the first time, we present a controlled preparation of large-area graphene/MoS2 heterostructures via a simple heating procedure on Mo-oleate complex coated sodium sulfate under N2 atmosphere. Through a direct in situ catalytic reaction, graphene layer has been uniformly grown on the MoS2 film formed by the reaction of Mo species with S pecies, which is from the carbothermal reduction of sodium sulfate. Due to the excellent graphene ``painting'' on MoS2 atomic layers, the significantly shortened lithium ion diffusion distance and the markedly enhanced electronic conductivity, these multilayered graphene/MoS2 heterostructures exhibit high specific capacity, unprecedented rate performance and outstanding cycling stability, especially at a high current density, when used as an anode material for lithium batteries. This work provides a simple but efficient route for the controlled fabrication of large-area multilayered graphene/metal sulfide heterostructures with promising applications in battery manufacture, electronics or catalysis.

  13. [Catalytic Degradation of Diclofenac Sodium over the Catalyst of 3D Flower-like alpha-FeOOH Synergized with H2O2 Under Visible Light Irradiation].

    PubMed

    Xu, Jun-ge; Li, Yun-qin; Huang, Hua-shan; Yuan, Bao-ling; Cui, Hao-jie; Fu, Ming-lai

    2015-06-01

    Three dimensional (3D) flower-like alpha-FeOOH nanomaterials were prepared by oil bath reflux method using FeSO4, urea, ethanol and water, and the products which were characterized by XRD, FT-IR and SEM techniques. The SEM images showed that the 3D flower-like samples consisted of nanorods with a length of 400-500 nm and a diameter of 40-60 nm. The catalytic performance of the samples was evaluated by catalytic degradation of diclofenac sodium using H2O2 as the oxidant under simulated visible light. The results showed that the as-prepared samples presented high efficient catalytic performances, and more than 99% of the initial diclofenac sodium (30 mg x L(-1)) was degraded in 90 min. A radical mechanism can be proposed for the catalytic degradation of diclofenac sodium solution.

  14. Catalytic oxidation of toluene in contaminant emission control systems using Mn-Ce/gamma-Al2O3.

    PubMed

    Kim, H-J; Choi, S-W; Inyang, H I

    2008-05-01

    Toluene, the alkyl benzene, is a common constituent of contaminant streams emitted by hydrocarbon fuel combustion systems. The oxidation of toluene to less toxic compounds can be enhanced through catalysis. The capacity of Mn-Ce/gamma-Al2O3 to catalyze toluene oxidation was investigated using a fixed bed flow reactor, operating within a temperature range of 160-400 degrees C. Mono-metallic catalysts were prepared with the manganese and cerium contents of 1-21 wt% on gamma-Al2O3, support and bi-metallic catalysts were prepared with cerium (0.5-21 wt%/) on 18.2 wt% manganese. The results indicate that the 18.2 wt% Mn-10.0 wt% Ce catalyst combination had the best catalytic efficiency for toluene oxidation. Increase in cerium loading reduces the surface area of catalytic materials measured by BET, but increases catalytic activity. Data obtained through TGA (Thermogravimetric analysis), XRD (X-ray diffraction) and toluene-TPR (Temperature Programmed Reduction) measurements show that the reduction of the catalysts in the process of toluene oxidation is directly proportional to observed weight loss under hydrogen flow. From these results, it is concluded that cerium improves the catalytic role of manganese in toluene oxidation. Oxygen mobility is also promoted in a redox mechanism in which MnO2 serves as the active sites. These results are useful in the development of toluene emission control systems for hydrocarbon fuel combustion systems.

  15. Prp2-mediated protein rearrangements at the catalytic core of the spliceosome as revealed by dcFCCS

    PubMed Central

    Ohrt, Thomas; Prior, Mira; Dannenberg, Julia; Odenwälder, Peter; Dybkov, Olexandr; Rasche, Nicolas; Schmitzová, Jana; Gregor, Ingo; Fabrizio, Patrizia; Enderlein, Jörg; Lührmann, Reinhard

    2012-01-01

    The compositional and conformational changes during catalytic activation of the spliceosome promoted by the DEAH box ATPase Prp2 are only poorly understood. Here, we show by dual-color fluorescence cross-correlation spectroscopy (dcFCCS) that the binding affinity of several proteins is significantly changed during the Prp2-mediated transition of precatalytic Bact spliceosomes to catalytically activated B* spliceosomes from Saccharomyces cerevisiae. During this step, several proteins, including the zinc-finger protein Cwc24, are quantitatively displaced from the B* complex. Consistent with this, we show that Cwc24 is required for step 1 but not for catalysis per se. The U2-associated SF3a and SF3b proteins Prp11 and Cus1 remain bound to the B* spliceosome under near-physiological conditions, but their binding is reduced at high salt. Conversely, high-affinity binding sites are created for Yju2 and Cwc25 during catalytic activation, consistent with their requirement for step 1 catalysis. Our results suggest high cooperativity of multiple Prp2-mediated structural rearrangements at the spliceosome's catalytic core. Moreover, dcFCCS represents a powerful tool ideally suited to study quantitatively spliceosomal protein dynamics in equilibrium. PMID:22535589

  16. Catalytic oxidation of elemental mercury over the modified catalyst Mn/alpha-Al2O3 at lower temperatures.

    PubMed

    Li, Jianfeng; Yan, Naiqiang; Qu, Zan; Qiao, Shaohua; Yang, Shijian; Guo, Yongfu; Liu, Ping; Jia, Jinping

    2010-01-01

    In order to facilitate the removal of elemental mercury (Hg(0)) from coal-fired flue gas, catalytic oxidation of Hg(0) with manganese oxides supported on inert alumina (alpha-Al2O3) was investigated at lower temperatures (373-473 K). To improve the catalytic activity and the sulfur-tolerance of the catalysts at lower temperatures, several metal elements were employed as dopants to modify the catalyst of Mn/alpha-Al2O3. The best performance among the tested elements was achieved with molybdenum (Mo) as the dopant in the catalysts. It can work even better than the noble metal catalyst Pd/alpha-Al2O3. Additionally, the Mo doped catalyst displayed excellent sulfur-tolerance performance at lower temperatures, and the catalytic oxidation efficiency for Mo(0.03)-Mn/alpha-Al2O3 was over 95% in the presence of 500 ppm SO2 versus only about 48% for the unmodified catalyst. The apparent catalytic reaction rate constant increased by approximately 5.5 times at 423 K. In addition, the possible mechanisms involved in Hg(0) oxidation and the reaction with the Mo modified catalyst have been discussed.

  17. Principles of water oxidation and O2-based hydrocarbon transformation by multinuclear catalytic sites

    SciTech Connect

    Musaev, Djamaladdin G; Hill, Craig L; Morokuma, Keiji

    2014-10-28

    Abstract The central thrust of this integrated experimental and computational research program was to obtain an atomistic-level understanding of the structural and dynamic factors underlying the design of catalysts for water oxidation and selective reductant-free O2-based transformations. The focus was on oxidatively robust polyoxometalate (POM) complexes in which a catalytic active site interacts with proximal metal centers in a synergistic manner. Thirty five publications in high-impact journals arose from this grant. I. Developing an oxidatively and hydrolytically stable and fast water oxidation catalyst (WOC), a central need in the production of green fuels using water as a reductant, has proven particularly challenging. During this grant period we have designed and investigated several carbon-free, molecular (homogenous), oxidatively and hydrolytically stable WOCs, including the Rb8K2[{Ru4O4(OH)2(H2O)4}(γ-SiW10O36)2]·25H2O (1) and [Co4(H2O)2(α-PW9O34)2]10- (2). Although complex 1 is fast, oxidatively and hydrolytically stable WOC, Ru is neither abundant nor inexpensive. Therefore, development of a stable and fast carbon-free homogenous WOC, based on earth-abundant elements became our highest priority. In 2010, we reported the first such catalyst, complex 2. This complex is substantially faster than 1 and stable under homogeneous conditions. Recently, we have extended our efforts and reported a V2-analog of the complex 2, i.e. [Co4(H2O)2(α-VW9O34)2]10- (3), which shows an even greater stability and reactivity. We succeeded in: (a) immobilizing catalysts 1 and 2 on the surface of various electrodes, and (b) elucidating the mechanism of O2 formation and release from complex 1, as well as the Mn4O4L6 “cubane” cluster. We have shown that the direct O-O bond formation is the most likely pathway for O2 formation during water oxidation catalyzed by 1. II. Oxo transfer catalysts that contain two proximal and synergistically interacting redox active metal

  18. Influence of catalyst synthesis method on selective catalytic reduction (SCR) of NO by NH3 with V2O5-WO3/TiO2 catalysts

    DOE PAGES

    He, Yuanyuan; Ford, Michael E.; Zhu, Minghui; ...

    2016-04-14

    We compared the molecular structures, surface acidity and catalytic activity for NO/NH3/O2 SCR of V2O5-WO3/TiO2 catalysts for two different synthesis methods: co-precipitation of aqueous vanadium and tungsten oxide precursors with TiO(OH)2 and by incipient wetness impregnation of the aqueous precursors on a reference crystalline TiO2 support (P25; primarily anatase phase). Bulk analysis by XRD showed that co-precipitation results in small and/or poorly ordered TiO2(anatase) particles and that VOx and WOx do not form solid solutions with the bulk titania lattice. Surface analysis of the co-precipitated catalyst by High Sensitivity-Low Energy Ion Scattering (HS-LEIS) confirms that the VOx and WOx aremore » surface segregated for the co-precipitated catalysts. In situ Raman and IR spectroscopy revealed that the vanadium and tungsten oxide components are present as surface mono-oxo O = VO3 and O = WO4 sites on the TiO2 supports. Co-precipitation was shown for the first time to also form new mono-oxo surface VO4 and WO4 sites that appear to be anchored at surface defects of the TiO2 support. IR analysis of chemisorbed ammonia showed the presence of both surface NH3* on Lewis acid sites and surface NH4+* on Brønsted acid sites. TPSR spectroscopy demonstrated that the specific SCR kinetics was controlled by the redox surface VO4 species and that the surface kinetics was independent of TiO2 synthesis method or presence of surface WO5 sites. SCR reaction studies revealed that the surface WO5 sites possess minimal activity below ~325 °C and their primary function is to increase the adsorption capacity of ammonia. A relationship between the SCR activity and surface acidity was not found. The SCR reaction is controlled by the surface VO4 sites that initiate the reaction at ~200 °C. The co-precipitated catalysts were always more active than the corresponding impregnated catalysts. Finally, we ascribe the higher activity of the co-precipitated catalysts to the presence of

  19. Microscopic investigations of site and functional selectivity of triazole for CO2 capture and catalytic applications.

    PubMed

    Boulmène, Reda; Prakash, Muthuramalingam; Hochlaf, Majdi

    2016-11-02

    Ab initio and DFT studies on CO2 interacting with different tautomers and isomers of triazole (TZ) are carried out to understand the adsorption mechanism and their mutual preferential sites. We used post Hartree-Fock methods (MP2, CCSD(T), and CCSD(T)-F12) and various DFTs (PBE, PBE0, M05-2X, and M11) with and without considering the dispersion correction for comparison. We determined hence the equilibrium structures, vibrational frequencies and binding energies of TZ-CO2 clusters and mapped their potential energy surfaces along the intermonomer coordinates. We find that the most stable TZ-CO2 clusters, some of them are already known, are not relevant for CO2 capture in porous materials. In addition, we show that the bonding between TZ and CO2 is due to various kinds of noncovalent interactions such as π-stacking, acid-base pair electron donor-electron acceptor (EDA) interactions along with N-HO and C-HO H-bonds with CO2. Our analysis reveals the existence of site selectivity effects when CO2 binds to TZ. These effects are related to the magnitude of the interaction potentials, in the order EDA (+N-HO) > EDA (+C-HO) > C(δ+)N[double bond, length as m-dash]N > π-stacking > σ type N-HO > C-HO H-bonds. This is the first report on the importance of competition between EDA, π-stacking and σ-bonds for CO2 capture and catalytic applications. Findings from this work may be used to give insights into the site specific CO2 capture ability of porous materials such as metal organic frameworks (MOFs), zeolitic imidazolate frameworks (ZIFs) or functionalized polymers. Finally, we show that IR spectroscopy of CO2 within the pores is neither a specific nor an efficient marker in probe-molecule experiments.

  20. Ultrasensitive colorimetric detection of Cu2+ ion based on catalytic oxidation of L-cysteine.

    PubMed

    Yin, Kun; Li, Bowei; Wang, Xiaochun; Zhang, Weiwei; Chen, Lingxin

    2015-02-15

    As an essential element, copper ion (Cu(2+)) plays important roles in human beings for its participation in diverse metabolic processes as a cofactor and/or a structural component of enzymes. However, excessive uptake of Cu(2+) ion gives rise to the risk of certain diseases. So, it is important to develop simple ways to monitor and detect Cu(2+) ion. In this study, a simple, facile colorimetric sensor for the ultrasensitive determination of Cu(2+) ion was developed based on the following principle: L-cysteine and 1-chloro-2,4-dinitrobenzene (CDNB) could be conjugated to form the yellow product 2,4-dinitrophenylcysteine (DNPC), which was measurable at 355nm; however, upon addition of Cu(2+) ion, the absorbance of DNPC would be decreased owing to the Cu(2+) ion catalytic oxidation of L-cysteine to L-cystine in the presence of O2. Thus, the colorimetric detection of Cu(2+) ion could be achieved. The optimal pH, buffer, temperature and incubation time for the colorimetric sensor were obtained of pH 6.8 in 0.1M HEPES solution, 90 °C and 50 min, respectively. A good linearity within the range of 0.8-10 nM (r = 0.996) was attained, with a high detectability up to 0.5nM. Analyses of Cu(2+) ion in drinking water, lake water, seawater and biological samples were carried out and the method performances were found to agree well with that obtained by ICP-MS. The developed simple colorimetric sensor proved applicable for Cu(2+) ion determination in real samples with high sensitivity and selectivity. Copyright © 2014 Elsevier B.V. All rights reserved.

  1. The catalytic incineration of (CH3)2S and its mixture with CH(3)SH over a Pt/Al(2)O(3) catalyst.

    PubMed

    Chu, H; Lee, W T; Horng, K H; Tseng, T K

    2001-03-19

    Catalytic incineration is one of the cost-effective technologies to solve the troublesome volatile organic compounds (VOCs). However, some sulfur containing VOCs, such as dimethyl sulfide, may deactivate the Pt catalyst that is commonly used in the catalytic incineration process. This paper provides information on the poisoning effect of (CH3)2S. The catalytic incineration of (CH3)2S, typically emitted from the petrochemical industry, over a Pt/Al(2)O(3) fixed bed catalytic reactor was studied. The effects of operating parameters including inlet temperature, space velocity, (CH3)2S concentration, O2 concentration and catalyst size were characterized. Catalytic incineration on a mixture of (CH3)2S with CH(3)SH was also tested. The results show that the conversions of (CH3)2S increase as the inlet temperature increases and the space velocity decreases. The higher the (CH3)2S concentration is, the lower its conversion is. The O2 concentration has a positive effect on the conversion of (CH3)2S. (CH3)2S has a poisoning effect on the Pt/Al(2)O(3) catalyst, especially at lower temperatures. The conversion of (CH3)2S is significantly suppressed by the existence of CH(3)SH.

  2. Effect of biochar addition on short-term N2O and CO2 emissions during repeated drying and wetting of an anthropogenic alluvial soil.

    PubMed

    Yang, Fang; Lee, Xinqing; Theng, Benny K G; Wang, Bing; Cheng, Jianzhong; Wang, Qian

    2016-06-07

    Agricultural soils are an important source of greenhouse gases (GHG). Biochar application to such soils has the potential of mitigating global anthropogenic GHG emissions. Under irrigation, the topsoils in arid regions experience repeated drying and wetting during the crop growing season. Biochar incorporation into these soils would change the soil microbial environment and hence affect GHG emissions. Little information, however, is available regarding the effect of biochar addition on carbon dioxide (CO2) and nitrous oxide (N2O) emissions from agricultural soils undergoing repeated drying and wetting. Here, we report the results of a 49-day aerobic incubation experiment, incorporating biochar into an anthropogenic alluvial soil in an arid region of Xinjiang Province, China, and measuring CO2 and N2O emissions. Under both drying-wetting and constantly moist conditions, biochar amendment significantly increased cumulative CO2 emission. At the same time, there was a significant reduction (up to ~20 %) in cumulative N2O emission, indicating that the addition of biochar to irrigated agricultural soils may effectively slow down global warming in arid regions of China.

  3. Dependence of Localized Electronic Structure on Ligand Configuration in the [2Fe] Hydrogenase Catalytic Core^*

    NASA Astrophysics Data System (ADS)

    Chang, Christopher H.; Kim, Kwiseon

    2007-03-01

    The [FeFe] hydrogenase enzyme is found in a variety of organisms, including Archaea, Eubacteria, and green algae^1,2, and crystallographically determined atomic position data is available for two examples. The biologically unusual catalytic H-cluster, responsible for proton reduction to H2 in vivo, is conserved in the known structures and includes two bis-thiolato bridged iron ions with extensive cyano- and carbonyl ligation. To address the configurational specificity of the diatomic ligand ligation, density functional theoretical calculations were done on [2Fe] core models of the active center, with varying CO and CN^- ligation patterns. Bonding in each complex has been characterized within the Natural Bond Orbital formalism. The effect of ligand configuration on bonding and charge distribution as well as Kohn-Sham orbital structure will be presented. [1] M. Forestier, P. King, L. Zhang, M. Posewitz, S. Schwarzer, T. Happe, M.L. Ghirardi, and M. Seibert, Eur. J. Biochem. 270, 2750 (2003). [2] Posewitz, M.C., P.W. King, S.L. Smolinski, R.D. Smith, II, A.R. Ginley, M.L. Ghirardi, and M. Seibert, Biochem. Soc. Trans. 33, 102 (2005). ^*This work was supported by the US DOE-SC-BES Hydrogen Fuels Initiative, and done in collaboration with the NREL Chemical and Biosciences Center.

  4. Adatom surface diffusion of catalytic metals on the anatase TiO2(101) surface.

    PubMed

    Alghannam, Afnan; Muhich, Christopher L; Musgrave, Charles B

    2017-02-08

    Titanium oxide is often decorated with metal nano-particles and either serves as a catalyst support or enables photocatalytic activity. The activity of these systems degrades over time due to catalytic particle agglomeration and growth by Ostwald ripening where adatoms dissociate from metal particles, diffuse across the surface and add to other metal particles. In this work, we use density functional theory calculations to study the diffusion mechanisms of select group VIII and 1B late-transition metal adatoms commonly used in catalysis and photocatalysis (Au, Ag, Cu, Pt, Rh, Ni, Co and Fe) on the anatase TiO2(101) surface. All metal adatoms preferentially occupy the bridge site between two 2-fold-coordinated oxygen anions (O2c). Surface migration was investigated by calculating the minimum energy pathway from one bridge site to another along three pathways: two in the [010] direction along a row of surface O2c anions and one in the [101[combining macron

  5. Catalytic activity in lithium-treated core–shell MoOx/MoS2 nanowires

    DOE PAGES

    Cummins, Dustin R.; Martinez, Ulises; Kappera, Rajesh; ...

    2015-09-22

    Significant interest has grown in the development of earth-abundant and efficient catalytic materials for hydrogen generation. Layered transition metal dichalcogenides present opportunities for efficient electrocatalytic systems. Here, we report the modification of 1D MoOx/MoS2 core–shell nanostructures by lithium intercalation and the corresponding changes in morphology, structure, and mechanism of H2 evolution. The 1D nanowires exhibit significant improvement in H2 evolution properties after lithiation, reducing the hydrogen evolution reaction (HER) onset potential by ~50 mV and increasing the generated current density by ~600%. The high electrochemical activity in the nanowires results from disruption of MoS2 layers in the outer shell, leadingmore » to increased activity and concentration of defect sites. This is in contrast to the typical mechanism of improved catalysis following lithium exfoliation, i.e., crystal phase transformation. As a result, these structural changes are verified by a combination of Raman and X-ray photoelectron spectroscopy (XPS).« less

  6. CATALYTIC DYNAMIC RESOLUTION APPLIED TO THE SYNTHESIS OF 2,6-DISUBSTITUTED PIPERIDINES: PREPARATION OF (+)-LUPETIDINE AND (−)-EPIDIHYDROPINIDINE‡

    PubMed Central

    Beng, Timothy K.; Gawley, Robert E.

    2012-01-01

    The diastereoselective synthesis of trans-2,6-disubstituted piperidines has been rendered enantioselective by incorporating a catalytic dynamic resolution into the first alkylation step. The method has been applied to the synthesis of (−)-epidihydropinidine and (+)-trans-lupetidine PMID:22408286

  7. Catalytic conversion of methane to methanol on Cu-SSZ-13 using N2O as oxidant.

    PubMed

    Ipek, B; Lobo, R F

    2016-11-08

    Direct catalytic methanol production from methane is achieved on Cu-SSZ-13 zeolite catalysts using N2O as the oxidant. The methanol production rate on Cu-SSZ-13 (on a per gram basis) was more than twice the rate on Cu-mordenite and more than four times the rate on Cu-ZSM-5.

  8. Catalytic hydrogenation of cyclic carbonates: a practical approach from CO2 and epoxides to methanol and diols.

    PubMed

    Han, Zhaobin; Rong, Liangce; Wu, Jiang; Zhang, Lei; Wang, Zheng; Ding, Kuiling

    2012-12-21

    Two birds with one stone: the simultaneous production of two important bulk chemicals, methanol and ethylene glycol, from CO(2) and ethylene oxide has been achieved under mild conditions by the highly efficient homogeneous catalytic hydrogenation of ethylene carbonate in the presence of a (PNP)Ru(II) catalyst.

  9. Plant carbon-nutrient interactions control CO{sub 2} exchange in Alaskan wet sedge tundra ecosystems

    SciTech Connect

    Johnson, L.C.; Shaver, G.R.; Cades, D.H.; Rastetter, E.; Nadelhoffer, K.; Giblin, A.; Laundre, J.; Stanley, A.

    2000-02-01

    The authors explored the long-term (8-yr) effects of separate field manipulations of temperature and nutrient availability on carbon balance in wet sedge tundra near the Arctic Long Term Ecological Research (LTER) site at Toolik Lake, Alaska. Their goals were (1) to assess the relative importance of chronic warming (with field greenhouses) and increased N and P availability (by fertilization) in controlling gross ecosystem photosynthesis, ecosystem respiration, and ultimately ecosystem C balance; and (2) to attempt to partition ecosystem responses to these treatments between plant and soil contributions. The authors present results of the effects of these manipulations on whole-system CO{sub 2} exchange over seasonal and duel cycles, and on nonrhizosphere soil microbial respiration using in situ soil incubations.

  10. Catalytic decomposition of Ba(NO3)2 on Pt(111)

    SciTech Connect

    Mudiyanselage, Kumudu; Weaver, Jason F.; Szanyi, Janos

    2011-04-07

    The decomposition of Ba(NO3)2 formed on BaO/Pt(111) (Pt(111) surface is partially covered by BaO) in the presence of CO was studied using temperature programmed desorption (TPD), infrared reflection absorption (IRA) and X-ray photoelectron (XP) spectroscopies. The exposure of BaO/Pt(111) to elevated NO2 pressure (1.0×10-4 Torr) at 450 K leads to the formation of Ba(NO3)2, chemisorbed O (OPt) and Pt-oxide-like domains. During TPD, the Ba(NO3)2 begins to thermally decompose near 490 K, releasing NO and NO2 with the maximum NOx desorption rate seen at 605 K. The OPt species formed following the exposure of BaO/Pt(111) to NO2 react with CO to release CO2 at 450 K. The consumption of OPt during CO oxidation initiates the migration of O from the Pt-oxide-like domains to the chemisorbed phase, where the CO oxidation reaction occurs. Therefore, the removal of OPt by CO leads to the reduction of oxidized Pt, and to the formation of metallic Pt(111) domains, where, subsequently, catalytic decomposition of Ba(NO3)2 can take place. The Pt-catalyzed decomposition of Ba(NO3)2 occurs readily at 450 K, a temperature much lower than the onset of the decomposition temperature of Ba(NO3)2 in the presence of oxidized Pt. This work was supported by the US Department of Energy Basic Energy Sciences' Chemical Sciences, Geosciences & Biosciences Division. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

  11. Magnetic porous PtNi/SiO2 nanofibers for catalytic hydrogenation of p-nitrophenol

    NASA Astrophysics Data System (ADS)

    Guan, Huijuan; Chao, Cong; Kong, Weixiao; Hu, Zonggao; Zhao, Yafei; Yuan, Siguo; Zhang, Bing

    2017-06-01

    In this work, the mesoporous SiO2 nanofibers from pyrolyzing precursor of electrospun nanofibers were employed as support to immobilize PtNi nanocatalyst (PtNi/SiO2 nanofibers). AFM, XRD, SEM, TEM, XPS, ICP-AES and N2 adsorption/desorption analysis were applied to systematically investigate the morphology and microstructure of as-prepared products. Results showed that PtNi alloy nanoparticles with average diameter of 18.7 nm were formed and could be homogeneously supported on the surface of porous SiO2 nanofiber, which further indicated that the SiO2 nanofibers with well-developed porous structure, large specific surface area, and roughened surface was a benefit for the support of PtNi alloy nanoparticles. The PtNi/SiO2 nanofibers catalyst exhibited an excellent catalytic activity towards the reduction of p-nitrophenol, and the catalyst's kinetic parameter ( k n = 434 × 10-3 mmol s-1 g-1) was much higher than those of Ni/SiO2 nanofibers (18 × 10-3 mmol s-1 g-1), Pt/SiO2 nanofibers (55 × 10-3 mmol s-1 g-1) and previous reported PtNi catalysts. The catalyst could be easily recycled from heterogeneous reaction system based on its good magnetic properties (the Ms value of 11.48 emu g-1). In addition, PtNi/SiO2 nanofibers also showed an excellent stability and the conversion rate of p-nitrophenol still could maintain 94.2% after the eighth using cycle.

  12. Analysis of the Sensitivity of GEM-MACH PM2.5 Forecasts to the Representation of Wet and Dry Deposition Processes

    NASA Astrophysics Data System (ADS)

    Pavlovic, Radenko; Gong, Wanmin; Moran, Mike; Menard, Sylvain; Anselmo, David; Davignon, Didier

    2014-05-01

    Environment Canada produces 48-hour operational air quality forecasts for Canada twice daily (at 00 and 12 UTC). At the core of the forecast system is the GEM-MACH model, an on-line coupled meteorology and chemistry model that considers gas-phase, aqueous-phase, and heterogeneous chemistry and a number of size-resolved particulate matter (PM) processes, including wet and dry deposition. Predicting PM concentrations, especially for fine particular matter (PM2.5), remains a challenge for air quality models. In this poster we analyze the maximum sensitivity of predicted PM2.5 concentrations to the representation of both wet and dry deposition. For wet deposition, both in-cloud and below-cloud scavenging are considered. An analysis of the impact of wet and dry deposition on PM2.5 concentrations was performed using GEM-MACH model output over the summer and winter seasons of 2012 for a base case and two sensitivity runs, one in which the parameterization of dry deposition was turned off and one in which the parameterization of wet deposition was turned off. The results obtained show that the predicted wet deposition of PM2.5 over North America is generally greater than predicted dry deposition, but both processes can reduce predicted PM2.5 concentration by 25% or more on average. However, the impact of both processes varies significantly from one region to another and is strongly dependent on modelled meteorology, especially the occurrence of precipitation. These results suggest that the details of the treatments of wet and dry deposition of PM2.5 do matter and can enhance or detract from model performance.

  13. Essential biphasic role for JAK3 catalytic activity in IL-2 receptor signaling.

    PubMed

    Smith, Geoffrey A; Uchida, Kenji; Weiss, Arthur; Taunton, Jack

    2016-05-01

    To drive lymphocyte proliferation and differentiation, common γ-chain (γc) cytokine receptors require hours to days of sustained stimulation. JAK1 and JAK3 kinases are found together in all γc-receptor complexes, but how their respective catalytic activities contribute to signaling over time is not known. Here we dissect the temporal requirements for JAK3 kinase activity with a selective covalent inhibitor (JAK3i). By monitoring phosphorylation of the transcription factor STAT5 over 20 h in CD4(+) T cells stimulated with interleukin 2 (IL-2), we document a second wave of signaling that is much more sensitive to JAK3i than the first wave. Selective inhibition of this second wave is sufficient to block cyclin expression and entry to S phase. An inhibitor-resistant JAK3 mutant (C905S) rescued all effects of JAK3i in isolated T cells and in mice. Our chemical genetic toolkit elucidates a biphasic requirement for JAK3 kinase activity in IL-2-driven T cell proliferation and will find broad utility in studies of γc-receptor signaling.

  14. Thermal catalytic oxidation of octachloronaphthalene over anatase TiO2 nanomaterial and its hypothesized mechanism

    PubMed Central

    Su, Guijin; Li, Qianqian; Lu, Huijie; Zhang, Lixia; Huang, Linyan; Yan, Li; Zheng, Minghui

    2015-01-01

    As an environmentally-green technology, thermal catalytic oxidation of octachloronaphthalene (CN-75) over anatase TiO2 nanomaterials was investigated at 300 °C. A wide range of oxidation intermediates, which were investigated using various techniques, could be of three types: naphthalene-ring, single-benzene-ring, and completely ring-opened products. Reactive oxygen species on anatase TiO2 surface, such as O2−• and O2−, contributed to oxidative degradation. Based on these findings, a novel oxidation degradation mechanism was proposed. The reaction at (101) surface of anatase TiO2 was used as a model. The naphthalene-ring oxidative products with chloronaphthols and hydroxyl-pentachloronaphthalene-dione, could be formed via attacking the carbon of naphthalene ring at one or more positions by nucleophilic O2−. Lateral cleavage of the naphthalene ring at different C1-C10 and C4-C9, C1-C2 and C4-C9, C1-C2 or and C3-C4 bond positions by electrophilic O2−• could occur. This will lead to the formation of tetrachlorophenol, tetrachloro-benzoic acid, tetrachloro-phthalaldehyde, and tetrachloro-acrolein-benzoic acid, partially with further transformation into tetrachlorobenzene-dihydrodiol and tetrachloro-salicylic acid. Unexpectedly, the symmetric half section of CN-75 could be completely remained with generating the intricate oxidative intermediates characteristically containing tetrachlorobenzene structure. Complete cleavage of naphthalene ring could produce the ring-opened products, such as formic and acetic acids. PMID:26643373

  15. Thermal catalytic oxidation of octachloronaphthalene over anatase TiO2 nanomaterial and its hypothesized mechanism

    NASA Astrophysics Data System (ADS)

    Su, Guijin; Li, Qianqian; Lu, Huijie; Zhang, Lixia; Huang, Linyan; Yan, Li; Zheng, Minghui

    2015-12-01

    As an environmentally-green technology, thermal catalytic oxidation of octachloronaphthalene (CN-75) over anatase TiO2 nanomaterials was investigated at 300 °C. A wide range of oxidation intermediates, which were investigated using various techniques, could be of three types: naphthalene-ring, single-benzene-ring, and completely ring-opened products. Reactive oxygen species on anatase TiO2 surface, such as O2-• and O2-, contributed to oxidative degradation. Based on these findings, a novel oxidation degradation mechanism was proposed. The reaction at (101) surface of anatase TiO2 was used as a model. The naphthalene-ring oxidative products with chloronaphthols and hydroxyl-pentachloronaphthalene-dione, could be formed via attacking the carbon of naphthalene ring at one or more positions by nucleophilic O2-. Lateral cleavage of the naphthalene ring at different C1-C10 and C4-C9, C1-C2 and C4-C9, C1-C2 or and C3-C4 bond positions by electrophilic O2-• could occur. This will lead to the formation of tetrachlorophenol, tetrachloro-benzoic acid, tetrachloro-phthalaldehyde, and tetrachloro-acrolein-benzoic acid, partially with further transformation into tetrachlorobenzene-dihydrodiol and tetrachloro-salicylic acid. Unexpectedly, the symmetric half section of CN-75 could be completely remained with generating the intricate oxidative intermediates characteristically containing tetrachlorobenzene structure. Complete cleavage of naphthalene ring could produce the ring-opened products, such as formic and acetic acids.

  16. Tuning photo-catalytic activities of TiO2 nanoparticles using dimethacrylate resins.

    PubMed

    Sun, Jirun; Watson, Stephanie S; Allsopp, David A; Stanley, Debbie; Skrtic, Drago

    2016-03-01

    The unique photo-catalytic activities (PCAs) of titanium dioxide nanoparticles (TiO2 NPs) made them attractive in many potential applications in medical devices. The objective of this study is to optimize the benefits of PCAs of TiO2 NPs through varying chemical structures of dimethacrylate resins. TiO2 NPs were functionalized to improve the PCAs and bonding to the resins. The PCAs of TiO2 NPs were evaluated using electron paramagnetic resonance (EPR) and UV-vis spectroscopy to determine the amount of the radicals generated and the energy required for their production, respectively. The beneficial effects of the radicals were assessed through: (1) the improvement of degree of vinyl conversion (DC) and (2) modification of resin hydrophilicity. One-way ANOVA with a 95% confidence interval was used to indicate the significant differences between the experimental groups. EPR and UV-vis results clearly showed that the functionalization of TiO2 NPs enhanced PCAs in terms of generating radicals under visible light irradiation. The presence of hydroxyl and carboxylic acid functionalities played an important role in DC enhancement and hydrophilicity modification. The DC could be increased up to 22% by adding only 0.1wt% TiO2 NPs. Viscosity of the resins had minimal or no role in DC improvement through TiO2 NPs. In resins with abundant hydroxyl groups, radicals were more effective in making the resin more hydrophilic. Knowledge learned from this study will help formulating nano-composites with optimized use of TiO2 PCAs as co-initiators for photo-polymerization, additives for making super-hydrophilic materials and/or antibacterial agents. Copyright © 2015 Academy of Dental Materials. All rights reserved.

  17. Hydrogen-Bonding Network Promoted [3+2] Cycloaddition: Asymmetric Catalytic Construction of Spiro-pseudoindoxyl Derivatives.

    PubMed

    Zhang, Liang-Jie; Wang, Yao; Hu, Xiu-Qin; Xu, Peng-Fei

    2016-03-18

    The enantioselective construction of a spirocyclic quaternary stereogenic carbon center at the C2 position of indole has long been an elusive problem in organic synthesis. Herein, by employing a rationally designed hydrogen-bonding network activation strategy, for the first time, 2,2'-pyrrolidinyl-spirooxindole, which is a valuable and prevalent indole alkaloid scaffold, was directly obtained through a catalytic asymmetric [3+2] cycloaddition reaction with high yields and excellent stereoselectivities.

  18. Mapping the catalytic pocket of phospholipases A2 and C using a novel set of phosphatidylcholines.

    PubMed Central

    Caramelo, J J; Florín-Christensen, J; Florín-Christensen, M; Delfino, J M

    2000-01-01

    A set of radioiodinatable phosphatidylcholines (PCs) derivatized with the Bolton-Hunter reagent (BHPCs) was synthesized to probe the substrate recognition and activity of phospholipases. A common feature of this series is the presence of a bulky 4-hydroxyphenyl group at the end of the fatty acyl chain attached to position sn-2. The distance between the end group and the glycerol backbone was varied by changing the length of the intervening fatty acyl chain (3-25 atoms). Except for the shortest, this chain includes at least one amide linkage. The usefulness of this series of substrates as a molecular ruler was tested by measuring the hydrolytic activities of Naja naja naja phospholipase A(2) (PLA(2)) and Bacillus cereus phospholipase C (PLC) in Triton X-100 micelles. The activity of PLA(2) proved to be highly dependent on the length of the fatty acyl chain linker, the shorter compounds (3-10 atoms) being very poor substrates. In contrast, the PLC activity profile exhibited much less discrimination. In both cases, PCs with 16-21 atom chains at position sn-2 yielded optimal activity. We interpret these findings in terms of fatty acyl chain length-related steric hindrance caused by the terminal aromatic group, affecting the activity of PLA(2) and, to a smaller extent, that of PLC. This notion agrees with the more extended recognition of aliphatic chains inside the narrow channel leading to the catalytic site in the former case. Molecular models of these substrates bound to PLA(2) were built on the basis of the crystallographic structure of Naja naja atra PLA(2) complexed with a phospholipid analogue. Docking of these substrates necessarily requires the intrusion of the bulky 4-hydroxyphenyl group inside the binding pocket and also the failure of the amide group to form hydrogen bonds inside the hydrophobic substrate channel. PMID:10698694

  19. Catalytic roles of Co0 and Co2+ during steam reforming of ethanol on Co/MgO catalysts

    SciTech Connect

    Karim, Ayman M.; Su, Yu; Engelhard, Mark H.; King, David L.; Wang, Yong

    2011-02-25

    Abstract: The catalytic roles of Co0 and Co2+ during steam reforming of ethanol were investigated over Co/MgO catalysts. Catalysts with different Co0/(Co0+Co2+) fraction were prepared through calcination and/or reduction at different temperatures, and the Co0 fraction was quantified by TPR and in-situ XPS. High temperature calcination of Co/MgO allowed us to prepare catalysts with more non-reducible Co2+ incorporated in the MgO lattice, while lower calcination temperatures allowed for the preparation of catalysts with higher Co0/(Co0+Co2+) fractions. The catalytic tests on Co0, non-reducible Co2+, and reducible Co2+ indicated that Co0 is much more active than either reducible or non-reducible Co2+ for C-C cleavage and water gas shift reaction. In addition, catalysts with a higher Co0 surface fraction exhibited a lower selectivity to CH4.

  20. Dentin bond optimization using the dimethyl sulfoxide-wet bonding strategy: A 2-year in vitro study.

    PubMed

    Stape, Thiago Henrique Scarabello; Tjäderhane, Leo; Tezvergil-Mutluay, Arzu; Yanikian, Cristiane Rumi Fujiwara; Szesz, Anna Luiza; Loguercio, Alessandro Dourado; Martins, Luís Roberto Marcondes

    2016-12-01

    This study evaluated a new approach, named dimethyl sulfoxide (DMSO)-wet bonding, to produce more desirable long-term prospects for the ultrafine interactions between synthetic polymeric biomaterials and the inherently hydrated dentin substrate. Sound third molars were randomly restored with/without DMSO pretreatment using a total-etch (Scocthbond Multipurpose: SBMP) and a self-etch (Clearfil SE Bond: CF) adhesive systems. Restored teeth (n=10)/group were sectioned into sticks and submitted to different analyses: micro-Raman determined the degree of conversion inside the hybrid layer (DC); resin-dentin microtensile bond strength and fracture pattern analysis at 24h, 1year and 2 years of aging; and nanoleakage evaluation at 24h and 2 years. DMSO-wet bonding produced significantly higher 24h bond strengths for SBMP that were sustained over the two-year period, with significantly less adhesive failures. Similarly, DMSO-treated CF samples presented significantly higher bond strength than untreated samples at two years. Both adhesives had significant less adhesive failures at 2 years with DMSO. DMSO had no effect on DC of SBMP, but significantly increased the DC of CF. DMSO-treated SBMP samples presented reduced silver uptake compared to untreated samples after aging. Biomodification of the dentin substrate by the proposed strategy using DMSO is a suitable approach to produce more durable hybrid layers with superior ability to withstand hydrolytic degradation over time. Although the active role of DMSO on dentin bond improvement may vary according to monomer composition, its use seems to be effective on both self-etch and etch-and-rinse bonding mechanisms. Copyright © 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  1. Highly selective catalytic reduction of NO via SO2/H2O-tolerant spinel catalysts at low temperature.

    PubMed

    Cai, Xuanxuan; Sun, Wei; Xu, Chaochao; Cao, Limei; Yang, Ji

    2016-09-01

    Selective catalytic reduction of NO X by hydrogen (H2-SCR) in the presence of oxygen has been investigated over the NiCo2O4 and Pd-doped NiCo2O4 catalysts under varying conditions. The catalysts were prepared by a sol-gel method in the presence of oxygen within 50-350 °C and were characterized using XRD, BET, EDS, XPS, Raman, H2-TPR, and NH3-TPD analysis. The results demonstrated that the doped Pd could improve the catalyst reducibility and change the surface acidity and redox properties, resulting in a higher catalytic performance. The performance of NiCo1.95Pd0.05O4 was consistently better than that of NiCo2O4 within the 150-350 °C range at a gas hourly space velocity (GHSV) of 4800 mL g(-1) h(-1), with a feed stream containing 1070 ppm NO, 10,700 ppm H2, 2 % O2, and N2 as balance gas. The effects of GHSV, NO/H2 ratios, and O2 feed concentration on the NO conversion over the NiCo2O4 and NiCo1.95Pd0.05O4 catalysts were also investigated. The two samples similarly showed that an increase in GHSV from 4800 to 9600 mL h(-1) g(-1), the NO/H2 ratio from 1:10 to 1:1, and the O2 content from 0 to 6 % would result in a decrease in NO conversion. In addition, 2 %, 5 %, and 8 % H2O into the feed gas had a slightly negative influence on SCR activity over the two catalysts. The effect of SO2 on the SCR activity indicated that the NiCo1.95Pd0.05O4 possesses better SO2 tolerance than NiCo2O4 catalyst does. Graphical abstract The NiCo1.95Pd0.05O4 catalyst achieved over 90 % NO conversion with N2 selectivity of 100 % in the 200∼250 °C range than the maximum 40.5 % NO conversion over NiCo2O4 with N2 selectivity of approximately 80 % in 350 °C.

  2. Treatment of phenol wastewater by microwave-induced ClO2-CuOx/Al203 catalytic oxidation process.

    PubMed

    Bi, Xiao-yi; Wang, Peng; Jiang, Hong; Xu, Huan-yan; Shi, Shu-Jie; Huang, Jun-li

    2007-01-01

    The catalyst of CuOx/Al2O3 was prepared by the dipping-sedimentation method using gamma-Al2O3 as a supporter. CuO and Cu2O were loaded on the surface of Al2O3, characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). In the presence of CuOx/Al2O3, the microwave-induced chlorine dioxide (ClO2) catalytic oxidation process was conducted for the treatment of synthetic wastewater containing 100 mg/L phenol. The factors influencing phenol removal were investigated and the results showed that microwave-induced ClO2-CuOx/Al2O3 process could effectively degrade contaminants in a short reaction time with a low oxidant dosage, extensive pH range. Under a given condition (ClO2 concentration 80 mg/L, microwave power 50 W, contact time 5 min, catalyst dosage 50 g/L, pH 9), phenol removal percentage approached 92.24%, corresponding to 79.13% of COD(Cr) removal. The removal of phenol by microwave-induced ClO2-CuOx/Al2O3 catalytic oxidation process was a complicated non-homogeneous solid/water reaction, which fitted pseudo-first-order by kinetics. Compared with traditional C1O2 oxidation, ClO2 catalytic oxidation and microwave-induced ClO2 oxidation, microwave-induced ClO2 catalytic oxidation system could significantly enhance the degradation efficiency. It provides an effective technology for the removal of phenol wastewater.

  3. Synthesis of highly active Pt-CeO2 hybrids with tunable secondary nanostructures for the catalytic hydrolysis of ammonia borane.

    PubMed

    Wang, Xiao; Liu, Dapeng; Song, Shuyan; Zhang, Hongjie

    2012-10-21

    We demonstrate a fast and facile ultrasound-assisted method to fabricate Pt-CeO(2) hybrids with tunable secondary nanostructures. The influence of hybrid structures towards their catalytic properties has been studied in depth. As a result the Pt-CeO(2) nanonecklace shows better catalytic performance than the nanoflower and the nanosatellite.

  4. N-doped TiO2 Nanotubes as an Effective Additive to Improve the Catalytic Capability of Methanol Oxidation for Pt/Graphene Nanocomposites

    PubMed Central

    Wang, Xiaohua; Li, Yueming; Liu, Shimin; Zhang, Long

    2016-01-01

    N-doped TiO2 nanotubes have been prepared as additives to improve the catalytic capability of Pt/graphene composites in methanol oxidation reactions. Electrochemical experiments show that the catalytic performance of Pt/graphene composites has been greatly improved by the introduction of N-doped TiO2 nanotubes.

  5. Nanostructured Samarium Doped Fluorapatites and Their Catalytic Activity towards Synthesis of 1,2,4-Triazoles.

    PubMed

    Gangu, Kranthi Kumar; Maddila, Suresh; Maddila, Surya Narayana; Jonnalagadda, Sreekantha B

    2016-09-24

    An investigation was conducted into the influence of the amino acids as organic modifiers in the facile synthesis of metal incorporated fluorapatites (FAp) and their properties. The nanostructured Sm doped fluorapatites (Sm-FAp) were prepared by a co-precipitation method using four different amino acids, namely glutamic acid, aspartic acid, glycine and histidine. The materials were characterized by various techniques including X-ray diffraction (XRD), Fourier transform infra-red spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), high resolution transmission electron microscopy (HR-TEM), N₂-adsorption/desorption isotherm, temperature programmed desorption (TPD) and fluorescence spectrophotometry. Under similar conditions, Sm-FAp prepared using different amino acids exhibited distinctly different morphological structures, surface area and pore properties. Their activity as catalysts was assessed and Sm-FAp/Glycine displayed excellent efficiency in the synthesis of 1,2,4-triazole catalyzing the reaction between 2-nitrobenzaldehyde and thiosemicarbazide with exceptional selectivity and 98% yield in a short time interval (10 min). The study provides an insight into the role of organic modifiers as controllers of nucleation, growth and aggregation which significantly influence the nature and activity of the catalytic sites on Sm-FAp. Sm-FAp could also have potential as photoactive material.

  6. Hydrogen production by thermo-catalytic decomposition of methane: Regeneration of active carbons using CO 2

    NASA Astrophysics Data System (ADS)

    Pinilla, J. L.; Suelves, I.; Utrilla, R.; Gálvez, M. E.; Lázaro, M. J.; Moliner, R.

    Thermo-catalytic decomposition of methane using carbons as catalyst is a very attractive process for free CO 2-hydrogen production. One of the main drawbacks for the sustainability of the process is catalyst deactivation. In this work, regeneration of a deactivated active-carbon catalyst has been studied using CO 2 as activating agent under different regeneration conditions. It has been stated that during the regeneration stage, a compromise between the regeneration of the initial properties of the catalyst and the burn-off is needed in order to keep the sustainability of the process. Three deactivation-regeneration cycles have been performed for two sets of regeneration conditions. A progressive decreasing in the burn-off, surface area and surface oxygenated groups after each decomposition/regeneration cycle is observed. It can be explained considering that the carbon removed during the regeneration steps is not the carbon deposited from methane but the remaining initial catalyst, which is less resistant to gasification. The implication is that after three cycles of decomposition/regeneration, most of the carbon sample consists of carbon formed during the process since the initial catalyst has been gasified.

  7. NASA Aerospace Flight Battery Program: Wet Life of Nickel-Hydrogen (Ni-H2) Batteries. Volume 1, Part 3

    NASA Technical Reports Server (NTRS)

    Jung, David S.; Lee, Leonine S.; Manzo, Michelle A.

    2010-01-01

    This NASA Aerospace Flight Battery Systems Working Group was chartered within the NASA Engineering and Safety Center (NESC). The Battery Working Group was tasked to complete tasks and to propose proactive work to address battery related, agency-wide issues on an annual basis. In its first year of operation, this proactive program addressed various aspects of the validation and verification of aerospace battery systems for NASA missions. Studies were performed, issues were discussed and in many cases, test programs were executed to generate recommendations and guidelines to reduce risk associated with various aspects of implementing battery technology in the aerospace industry. This document contains Part 3 - Volume I: Wet Life of Nickel-Hydrogen (Ni-H2) Batteries of the program's operations.

  8. N2O production pathway change during drought and following wet-up in a controlled rainforest at Biosphere 2 Center

    NASA Astrophysics Data System (ADS)

    van Haren, J.; Yamagishi, H.; Yoshida, N.

    2003-12-01

    N2O is the fourth most important greenhouse gas and it leads to ozone destruction in the stratosphere. Rainforests account for ˜ 20% of global N2O emissions. In soils N2O can be produced though hydroxylamine oxidation by methanotrophs, nitrification, nitrifier denitrification, and denitrification. The former two processes occur under aerobic and the latter two under anaerobic conditions. During a drought, soils are expected to change from more anaerobic to more aerobic conditions, thus leading to a change in N2O production pathway. To test this we conducted a 37-day drought in a controlled rainforest mesocosm at Biosphere 2 Center. Three times during the drought and immediately after wet-up, we collected air and soil samples to determine the N2O isotope changes. Top 10 cm soil Water Filled Pore Space (WFPS) decreased from ˜ 60 to 20% and WFPS below 50 cm decreased from ˜ 50 to 40% during the drought. Meanwhile the whole system N2O flux decreased from 120+/-4 to 41.5+/-2.6 μ g-N/m2/hr. δ 15N, δ 18O, and site preference of N2O increased by 7, ˜2, and ˜2.5‰ , respectively. Immediately following wet-up a pulse of N2O was released with δ 15N, δ 18O, and Site preference 15, 3 and 15‰ lower than before. We will present evidence to support that the stable isotope increase with soil water loss can be explained by an increase in contribution of hydroxylamine oxidation by methanotrophs. Whereas the isotopic change following wet-up is due to increased contribution from nitrifier-denitrification to the overall N2O flux.

  9. Enhanced CO gas sensing properties of Cu doped SnO2 nanostructures prepared by a facile wet chemical method.

    PubMed

    Bhardwaj, Neha; Pandey, Akhilesh; Satpati, Biswarup; Tomar, Monika; Gupta, Vinay; Mohapatra, Satyabrata

    2016-07-28

    We report the synthesis of Cu doped SnO2 nanostructures with enhanced CO gas sensing properties by a facile wet chemical method. The effects of Cu doping on the structural and optical properties of SnO2 nanostructures were investigated using X-ray diffraction, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and high resolution TEM (HRTEM) with energy dispersive X-ray spectroscopy, Raman spectroscopy and photoluminescence spectroscopy. FESEM studies revealed the presence of nanosheets and nanodisc-like structures in Cu doped SnO2 samples. Gas sensing studies showed that the sensor prepared using 1% Cu doped SnO2 nanostructures exhibits highly enhanced CO gas sensing properties as compared to pure SnO2 nanostructures and shows excellent selectivity for CO with negligible interference from CH4, CO2 and NO2. The possible mechanism for the enhanced CO gas sensing properties of Cu doped SnO2 nanostructures is proposed.

  10. [Preparation of β-In2S3 and Catalytic Degradation of Oxytetracycline Under Solar Light Irradiation].

    PubMed

    Ai, Cui-ling; Zhou, Dan-dan; Zhang, Rong-rong; Shao, Xiang-wen; Lei, Ying-jie

    2015-08-01

    The preparation of beta-In2S3 nanomaterial was carried out by reacting In (NO3)3 with thioacetamide through hydrothermal process at 120 degrees C for 12 h. The size and morphology of In2S3 were characterized by the scanning electron microscope (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) while the degradation efficiency was evaluated by the photocatalytic degradation of oxytetracycline under natural sunlight. The results revealed that beta-In2S3 nanoparticles are made up of nanosheets with a length of 15-30 nm and with high efficient catalytic performance, in which more than 98% of the initial oxytetracycline (30 mg x L(-1)) was degraded in 4 h. Furthermore, the prepared pG-In2 S3 can be recycled and kept efficient catalytic performance above 85% even after reusing for four times, which reflected the good stability and relative photocatalytic activity of In2S3.

  11. Simultaneous catalytic removal of NO and N{sub 2}O using Fe-MFI

    SciTech Connect

    Koegel, M.; Turek, T.; Moennig, R.; Schwieger, W.; Tissler, A.

    1999-03-10

    Fe-MFI preparations active for the reduction of nitric oxide and nitrous oxide with hydrocarbons have been prepared by solid-state ion-exchange in the presence of air. While nitrous oxide can be removed by a variety of reducing agents, C{sub 3} hydrocarbons, especially propane, are suitable for the catalytic reduction of nitric oxide. The reduction of nitrous oxide was always enhanced by increasing temperature, whereas maximum NO conversions were observed at temperatures around 300 C. The addition of up to 7% of water was found to decrease the achievable conversions of the nitrogen oxides moderately. The activity for the removal of nitrous oxide was strongly inhibited in the presence of NO, probably via an intermediate formed from NO{sub 2} and the hydrocarbon. On the other hand, the observed NO conversions were not affected by the presence of nitrous oxide. In all cases, considerable amounts of carbon monoxide were formed from the hydrocarbons. It could be shown that the degree of ion-exchange achievable during the solid-state procedure is limited. At iron contents exceeding Fe/Al = 0.5, Fe ions are no longer being introduced into the zeolite. The excess iron is being precipitated as hematite, which is inactive in the reduction of both nitric oxide and nitrous oxide.

  12. The CDC2-related kinase PITALRE is the catalytic subunit of active multimeric protein complexes.

    PubMed Central

    Garriga, J; Mayol, X; Graña, X

    1996-01-01

    PITALRE is a human protein kinase identified by means of its partial sequence identity to the cell division cycle regulatory kinase CDC2. Immunopurified PITALRE protein complexes exhibit an in vitro kinase activity that phosphorylates the retinoblastoma protein, suggesting that PITALRE catalyses this phosphorylation reaction. However, the presence of other kinases in the immunopurified complex could not be ruled out. In the present work, an inactive mutant of the PITALRE kinase has been used to demonstrate that PITALRE is the catalytic subunit responsible for the PITALRE-complex-associated kinase activity, Ectopic overexpression of PITALRE did not increase the total PITALRE kinase activity in the cell, suggesting that PITALRE is regulated by limiting cellular factor(s). Characterization of the PITALRE-containing protein complexes indicated that most of the cellular PITALRE protein exists as a subunit in at least two different active multimeric complexes. Although monomeric PITALRE is also active in vitro, PITALRE present in multimeric complexes exhibits several-fold higher activity than monomeric PITALRE. In addition, overexpression of PITALRE demonstrated the existence of two new associated proteins of approx. 48 and 98 kDa. Altogether these results suggest that, in contrast to the situation with cyclin-dependent kinases, monomeric PITALRE is active, and that association with other proteins modulates its activity and/or its ability to recognize substrates in vivo. PMID:8870681

  13. Catalytic activities of Werner protein are affected by adduction with 4-hydroxy-2-nonenal.

    PubMed

    Czerwińska, Jolanta; Poznański, Jarosław; Dębski, Janusz; Bukowy, Zuzanna; Bohr, Vilhelm A; Tudek, Barbara; Speina, Elżbieta

    2014-01-01

    4-Hydroxy-2-nonenal (HNE) is a reactive α,β-unsaturated aldehyde generated during oxidative stress and subsequent peroxidation of polyunsaturated fatty acids. Here, Werner protein (WRN) was identified as a novel target for modification by HNE. Werner syndrome arises through mutations in the WRN gene that encodes the RecQ DNA helicase which is critical for maintaining genomic stability. This hereditary disease is associated with chromosomal instability, premature aging and cancer predisposition. WRN appears to participate in the cellular response to oxidative stress and cells devoid of WRN display elevated levels of oxidative DNA damage. We demonstrated that helicase/ATPase and exonuclease activities of HNE-modified WRN protein were inhibited both in vitro and in immunocomplexes purified from the cell extracts. Sites of HNE adduction in human WRN were identified at Lys577, Cys727, His1290, Cys1367, Lys1371 and Lys1389. We applied in silico modeling of the helicase and RQC domains of WRN protein with HNE adducted to Lys577 and Cys727 and provided a potential mechanism of the observed deregulation of the protein catalytic activities. In light of the obtained results, we postulate that HNE adduction to WRN is a post-translational modification, which may affect WRN conformational stability and function, contributing to features and diseases associated with premature senescence.

  14. Catalytic activities of Werner protein are affected by adduction with 4-hydroxy-2-nonenal

    PubMed Central

    Czerwińska, Jolanta; Poznański, Jarosław; Dębski, Janusz; Bukowy, Zuzanna; Bohr, Vilhelm A.; Tudek, Barbara; Speina, Elżbieta

    2014-01-01

    4-Hydroxy-2-nonenal (HNE) is a reactive α,β-unsaturated aldehyde generated during oxidative stress and subsequent peroxidation of polyunsaturated fatty acids. Here, Werner protein (WRN) was identified as a novel target for modification by HNE. Werner syndrome arises through mutations in the WRN gene that encodes the RecQ DNA helicase which is critical for maintaining genomic stability. This hereditary disease is associated with chromosomal instability, premature aging and cancer predisposition. WRN appears to participate in the cellular response to oxidative stress and cells devoid of WRN display elevated levels of oxidative DNA damage. We demonstrated that helicase/ATPase and exonuclease activities of HNE-modified WRN protein were inhibited both in vitro and in immunocomplexes purified from the cell extracts. Sites of HNE adduction in human WRN were identified at Lys577, Cys727, His1290, Cys1367, Lys1371 and Lys1389. We applied in silico modeling of the helicase and RQC domains of WRN protein with HNE adducted to Lys577 and Cys727 and provided a potential mechanism of the observed deregulation of the protein catalytic activities. In light of the obtained results, we postulate that HNE adduction to WRN is a post-translational modification, which may affect WRN conformational stability and function, contributing to features and diseases associated with premature senescence. PMID:25170083

  15. Fabrication and mechanical properties of continuously graded WSi{sub 2}-ZrO{sub 2}(2Y) materials using wet-molding

    SciTech Connect

    Arata, K.; Yoshinaka, M.; Hirota, K.; Yamaguchi, O.

    1998-04-01

    Continuously graded WSi{sub 2}-ZrO{sub 2}(2Y) materials with high density (99.2% of theoretical) have been fabricated by uniaxial wet-molding, followed by hot pressing (1,000 C/1h/30MPa) and hot isostatic pressing (1,500 C/2h/196MPa). A mixed solution of glycerin and ethanol with the viscosity of {approx} 6 mPa{center_dot}s has been used as a dispersion medium in the molding process. The sintered materials show a linear composition profile with a transition from WSi{sub 2}/ZrO{sub 2}(2Y) {approx} 75/25 to {approx} 5/95 mol%. Vickers hardness, Hv, for which the value is {approx} 11.2 GPa, is almost independent of the compositional change. Fracture toughness, K{sub C}, increases from 5.6 to 10.3 MPa{center_dot}m{sup 1/2} with increasing ZrO{sub 2}(2Y) composition.

  16. Persistent DNA binding, cleavage performance and eco-friendly catalytic nature of novel complexes having 2-aminobenzophenone precursor.

    PubMed

    Muniyandi, Vellaichamy; Pravin, Narayanaperumal; Subbaraj, Paramasivam; Raman, Natarajan

    2016-03-01

    This paper describes the synthesis of four novel bidentate metal(II) complexes having 2-aminobenzophenone precursor and a co-ligand (anthranilic acid). They are characterized by the usual spectral and analytical data. They adopt octahedral geometrical arrangements around the metal ions which have been confirmed by electronic absorption data. Moreover, the EPR study of Cu(II) complex has provided supportive evidence to the conclusion drawn on the basis of electronic spectrum and magnetic moment value. Powder XRD and SEM studies show that all the complexes are microcrystalline with homogenous morphology. The interaction of these complexes with CT-DNA has been explored by UV-absorption, fluorescence, viscosity, CV and CD techniques which reveal that the complexes could bind to CT-DNA through intercalation. The oxidative cleavage of the metal complexes with pBR322 DNA has also been investigated by gel electrophoresis. Moreover, the antimicrobial bustle shows that all metal chelates have superior activity than the free Schiff base ligand. The catalytic activity of the complexes has been evaluated towards the oxidation of aniline. All the complexes exhibit significant catalytic activity. Among them Cu(II) complex exhibits better catalytic activity than others. This catalytic process occurs at room temperature and it proceeds in water medium which suggests that this is an eco-friendly process. Copyright © 2016 Elsevier B.V. All rights reserved.

  17. Treatment of a simulated phenolic effluent by heterogeneous catalytic ozonation using Pt/Al2O3.

    PubMed

    Fajardo, Ana S; Martins, Rui C; Quinta-Ferreira, Rosa M

    2013-01-01

    Non-catalytic and catalytic ozonation over Pt/Al2O3 were considered in the treatment of a synthetic effluent composed of six phenolic acids usually present in olive mill wastewaters. In both processes the medium pH affected the rate of ozone decomposition and the formation of hydroxyl radicals. The optimum values were achieved for the catalytic system under pH 7 with 93.0 and 47.7%, respectively, of total phenol content and chemical oxygen demand (COD) removal, after 120 minutes of reaction. For pH 3, the catalytic ozonation followed a free radical pathway perceived by the presence of radical scavengers. No significant structural differences were observed between the fresh and used solid catalyst in X-ray diffraction analysis. Aluminium leaching behaviour was also evaluated at the end of each experiment. Moreover, a sequence of feed-batch trials involving the catalyst reutilization exhibited almost constant activity during the operation time. Eco-toxicological tests were performed for both processes, revealing that the treated effluent still presents some ecological impact, although it is lower than that for the raw wastewater.

  18. Catalytic Hydroxylation of Polyethylenes

    PubMed Central

    2017-01-01

    Polyolefins account for 60% of global plastic consumption, but many potential applications of polyolefins require that their properties, such as compatibility with polar polymers, adhesion, gas permeability, and surface wetting, be improved. A strategy to overcome these deficiencies would involve the introduction of polar functionalities onto the polymer chain. Here, we describe the Ni-catalyzed hydroxylation of polyethylenes (LDPE, HDPE, and LLDPE) in the presence of mCPBA as an oxidant. Studies with cycloalkanes and pure, long-chain alkanes were conducted to assess precisely the selectivity of the reaction and the degree to which potential C–C bond cleavage of a radical intermediate occurs. Among the nickel catalysts we tested, [Ni(Me4Phen)3](BPh4)2 (Me4Phen = 3,4,7,8,-tetramethyl-1,10-phenanthroline) reacted with the highest turnover number (TON) for hydroxylation of cyclohexane and the highest selectivity for the formation of cyclohexanol over cyclohexanone (TON, 5560; cyclohexanol/(cyclohexanone + ε-caprolactone) ratio, 10.5). The oxidation of n-octadecane occurred at the secondary C–H bonds with 15.5:1 selectivity for formation of an alcohol over a ketone and 660 TON. Consistent with these data, the hydroxylation of various polyethylene materials by the combination of [Ni(Me4Phen)3](BPh4)2 and mCPBA led to the introduction of 2.0 to 5.5 functional groups (alcohol, ketone, alkyl chloride) per 100 monomer units with up to 88% selectivity for formation of alcohols over ketones or chloride. In contrast to more classical radical functionalizations of polyethylene, this catalytic process occurred without significant modification of the molecular weight of the polymer that would result from chain cleavage or cross-linking. Thus, the resulting materials are new compositions in which hydroxyl groups are located along the main chain of commercial, high molecular weight LDPE, HDPE, and LLDPE materials. These hydroxylated polyethylenes have improved wetting

  19. Mn-Promoted Co3O4/TiO2 as an efficient catalyst for catalytic oxidation of dibromomethane (CH2Br2).

    PubMed

    Mei, Jian; Zhao, Songjian; Huang, Wenjun; Qu, Zan; Yan, Naiqiang

    2016-11-15

    Brominated hydrocarbon is the typical pollutant in the exhaust gas from the synthesis process of Purified Terephthalic Acid (PTA), which may cause various environmental problems once emitted into atmosphere. Dibromomethane (DBM) was employed as the model compound in this study, and a series of TiO2-supported manganese and cobalt oxide catalysts with different Mn/Co molar ratio were prepared by the impregnation method and used for catalytic oxidation of DBM. It was found that the addition of Mn significantly enhanced the catalytic performance of Co/TiO2 catalyst. Among all the prepared catalysts, Mn(1)-Co/TiO2 (Mn/Co molar ratio was 1) catalyst exhibited the highest activity with T90 at about 325°C and good stability maintained for at least 30h at 500ppm DBM and 10% O2 at GHSV=60,000h(-1), and the final products in the reaction were COx, HBr and Br2, without the formation of Br-containing organics. The high activity and high stability might be attributed to the redox cycle (Co(2+)+Mn(4+)↔Co(3+)+Mn(3+)) over Mn-promoted Co3O4/TiO2 catalyst. Based on the results of in situ DRIFT studies and analysis of products, a plausible reaction mechanism for catalytic oxidation of DBM over Mn-Co/TiO2 catalysts was also proposed. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. Rational design of MnO2@MnO2 hierarchical nanomaterials and their catalytic activities.

    PubMed

    Zhang, Bentian; Cheng, Gao; Ye, Wenjin; Zheng, Xiaoying; Liu, Hengfa; Sun, Ming; Yu, Lin; Zheng, Yuying; Cheng, Xiaoling

    2016-11-29

    Hierarchically structured materials have special properties and possess potential in applications in the catalytic and electrochemical fields. Herein, two kinds of hierarchical core-shell nanostructures, lavender-like α-MnO2@α-MnO2 and balsam pear-like α-MnO2@γ-MnO2, were prepared by a facile room-temperature method using α-MnO2 nanowires as a backbone under acidic and alkaline conditions, respectively. When being used as a catalyst for dimethyl ether combustion, α-MnO2@γ-MnO2 exhibited a better performance than α-MnO2@α-MnO2 (T10 = 171 vs. 196 °C; T90 = 220 vs. 258 °C, SV = 30, 000 mL g(-1) h(-1)). It is concluded that the larger surface area, higher reducibility/oxygen mobility, richer surface oxygen species, and the relatively smaller apparent activation energy are responsible for the superior performance of α-MnO2@γ-MnO2.

  1. Synthesis of MoS2 multi-wall nanotubes using wet chemical method with H2O2 as growth promoter

    NASA Astrophysics Data System (ADS)

    Vattikuti, S. V. Prabhakar; Byon, Chan; Reddy, Ch. Venkata

    2015-09-01

    This paper reports the synthesis of MoS2 multi-wall nanotubes (MWNTs) using a wet chemical method assisted by H2O2 solvent as a growth promoter for the first time. The influence of the calcination temperature on the morphology of the nanotubes is discussed. Powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM) were used to characterize the as-prepared MoS2 MWNTs. The powder XRD measurement indicated a hexagonal phase of the MoS2 MWNTs. The addition of H2O2 solvent influenced the growth, and the mean length of the nanotubes was 100-300 nm with diameter of 20-30 nm. The synthetic conditions for optimization of the MoS2 MWNTs are also discussed. The calculated band gap energy is 2.57 eV. The MoS2 MWNTs exhibit higher photocatalytic activity for the degradation of Rhodamine B (RhB) under UV light irradiation for 60 min. The highest photocatalytic activity was obtained with the sample containing 0.5 wt% MoS2 MWNTs, with which more than 98% of the RhB was degraded within 60 min.

  2. In situ X-ray diffraction study of Na+ saturated montmorillonite exposed to variably wet super critical CO2.

    PubMed

    Ilton, Eugene S; Schaef, H Todd; Qafoku, Odeta; Rosso, Kevin M; Felmy, Andrew R

    2012-04-03

    Reactions involving variably hydrated super critical CO(2) (scCO(2)) and a Na saturated dioctahedral smectite (Na-STX-1) were examined by in situ high-pressure X-ray diffraction at 50 °C and 90 bar, conditions that are relevant to long-term geologic storage of CO(2). Both hydration and dehydration reactions were rapid with appreciable reaction occurring in minutes and near steady state occurring within an hour. Hydration occurred stepwise as a function of increasing H(2)O in the system; 1W, 2W-3W, and >3W clay hydration states were stable from ~2-30%, ~31-55 < 64%, and ≥ ~71% H(2)O saturation in scCO(2), respectively. Exposure of sub 1W clay to anhydrous scCO(2) caused interlayer expansion, not contraction as expected for dehydration, suggesting that CO(2) intercalated the interlayer region of the sub 1W clay, which might provide a secondary trapping mechanism for CO(2). In contrast, control experiments using pressurized N(2) and similar initial conditions as in the scCO(2) study, showed little to no change in the d(001) spacing, or hydration states, of the clay. A salient implication for cap rock integrity is that clays can dehydrate when exposed to wet scCO(2). For example, a clay in the ~3W hydration state could collapse by ~3 Å in the c* direction, or ~15%, if exposed to scCO(2) at less than or equal to about 64% H(2)O saturation.

  3. Oxidation of nitrogen oxide in hybrid plasma-catalytic reactors based on DBD and Fe2O3

    NASA Astrophysics Data System (ADS)

    Jõgi, Indrek; Erme, Kalev; Haljaste, Ants; Laan, Matti

    2013-02-01

    In the present study, Fe2O3 was used as catalyst for the removal of NO in a hybrid plasma- catalytic reactor. The catalyst was located either directly inside the hybrid plasma-catalytic reactor or in a separate catalytic reactor, which followed ozone producing and injecting plasma reactor. Ozone production in such a reactor was dependent on the state of the electrode surface. The fresh catalyst ensured an order of magnitude smaller ozone concentration in the outlet of the hybrid reactor. After a short treatment of the catalyst with NO2, its ability to destroy ozone diminished but was regained after heating of the reactor up to 100 °C. Similarly to earlier results obtained with TiO2, the removal of NO in the hybrid reactor with Fe2O3 was enhanced compared to that in an ordinary plasma reactor. In the ozone injection reactor, oxidation of NO to NO2 took place with considerably higher efficiency compared to the hybrid reactor. The use of catalyst in the ozonation stage further improved the oxidation of NO2 to N2O5. The time-dependence effects of NO removal during plasma and ozone oxidation were explained by reactions between NO2 adsorbed on surface, with surface-bound NO3 and gas phase NO as the reaction product. Contribution to the Topical Issue "13th International Symposium on High Pressure Low Temperature Plasma Chemistry (Hakone XIII)", Edited by Nicolas Gherardi, Henryca Danuta Stryczewska and Yvan Ségui.

  4. Photocatalytic energy storage ability of TiO2-WO3 composite prepared by wet-chemical technique.

    PubMed

    Cao, Linglin; Yuan, Jian; Chen, Mingxia; Shangguan, Wenfeng

    2010-01-01

    TiO2-WO3 hybrid photocatalysts were prepared using wet-chemical technique, and their energy storage performance was characterized by electrochemical galvanostatic method. TiO2 powder was coupled with WO3 powder, which was used as electron pool and the reductive energy could be stored in. As a result, the prepared TiO2-WO3 had good energy storage ability while pure TiO2 showed no capacity and pure WO3 showed quite low performance. The energy storage ability was affected by the crystal structure of WO3 and calcination temperature. The photocatalyst had better capacity when WO3 had low degree of crystallinity, since its loose structure made it easier for electrons and cations to pass through. The photocatalytic energy storage performance was also affected by the molar ratio of TiO2 to WO3. Energy storage capacity was significantly dependent on the composition, reaching the maximum value at TiO2/WO3 1:1 (mol/mol).

  5. Photocatalytic activities of wet oxidation synthesized ZnO and ZnO-TiO2 thick porous films

    NASA Astrophysics Data System (ADS)

    Chen, Ruiqun; Han, Jie; Yan, Xiaodong; Zou, Chongwen; Bian, Jiming; Alyamani, Ahmed; Gao, Wei

    2011-05-01

    Highly porous zinc oxide (ZnO) film was produced by using reactive magnetron sputtering zinc target followed by wet oxidation. Titanium dioxide (TiO2) was mixed to the porous films by using either TiO2 target magnetron sputter deposition or sol-spin method. The film thickness could reach 50 μm with uniform porosity. On the sputtering prepared ZnO-TiO2 film surface, fine nanorods with small anatase TiO2 nano-clusters on the tips were observed by SEM and TEM, and the titanium (Ti) composition was determined by XPS as 0.37%. The sol-spin treatment could increase the Ti composition to 4.9%, with reduced pore size compared to the untreated ZnO porous film. Photoluminescence measurements showed that the Ti containing porous film has strong ultraviolet-visible light emission. In the photo-catalysis testing, ZnO and ZnO-TiO2 have similar photo-catalysis activity under 365 nm UV irradiation, but under visible light, the photocatalysis activities of ZnO-TiO2 films were twice higher than that of ZnO porous film, implying promising applications of this porous oxide composite for industrial and dairy farm wastewater treatment.

  6. The use of wet limestone systems for combined removal of SO sub 2 and NO sub x from flue gas

    SciTech Connect

    Lee, G.C. ); Shen, D.X.; Littlejohn, D.; Chang, S.G. )

    1990-03-01

    A new approach by utilizing yellow phosphorus in conventional wet limestone systems for high efficiency control of SO{sub 2} and NO{sub x} emissions from power plants has been developed. The addition of yellow phosphorus in the system induces the production of O{sub 3} which subsequently oxidizes NO to NO{sub 2}. The resulting NO{sub 2} dissolves readily and can be reduced to form ammonium ions by dissolved SO{sub 2} under appropriate conditions. Yellow phosphorus is oxidized to yield P{sub 2}O{sub 5} which picks up water to form H{sub 3}PO{sub 4} mists and can be collected as a valuable product. Proof of concept experiments have been performed using a 20 acfm bench-scale system. The results show that better than 90% of SO{sub 2} and NO in simulated flue gas can be removed. Stoichiometric ratios (P/NO) ranging between 0.6 and 1.5 were obtained. This ratio depends on operating conditions as well as the process configuration. A conceptual process flow diagram has been proposed. A preliminary cost evaluation of this approach appears to indicate great economic potential. 22 refs., 8 figs., 1 tab.

  7. K-Mn supported on three-dimensionally ordered macroporous La0.8Ce0.2FeO3 catalysts for the catalytic combustion of soot

    NASA Astrophysics Data System (ADS)

    Feng, Nengjie; Chen, Chong; Meng, Jie; Liu, Geng; Fang, Fan; Wang, Lei; Wan, Hui; Guan, Guofeng

    2017-03-01

    Three-dimensionally ordered macroporous (3DOM) La0.8Ce0.2FeO3 perovskite was successfully constructed through a colloidal crystal template way. And the K-Mn/3DOM La0.8Ce0.2FeO3 catalyst was obtained by an incipient-wetness impregnation method. The physicochemical characterizations of the material were conducted by means of XRD, FESEM, TEM, N2 adsorption-desorption, H2-TPR, XPS and O2-TPD techniques, and the catalytic performance was evaluated for soot removal. The intact well-ordered macroporous skeleton was remained after K and Mn were loaded, which offered an ideal environment for soot combustion. The generated K2Mn4O8 was well decorated on the skeleton of the 3DOM perovskite, which could increase the concentration of surface oxygen species and enhance the reducibility of catalyst. The as-prepared catalyst exhibited good catalytic performance for soot removal, and could lower the T50 of soot to 377 °C.

  8. Fabrication and mechanical properties of continuously graded MoSi{sub 2}-ZrO{sub 2}(2Y) materials using wet-molding

    SciTech Connect

    Arata, Kenji; Takeuchi, Nobutaka; Yoshinaka, Masaru; Hirota, Ken; Yamaguchi, O.

    1997-08-01

    Continuously graded MoSi{sub 2}-ZrO{sub 2}(2Y) materials with high density (97.5% of theoretical) have been fabricated by uniaxial wet-molding, followed by hot pressing (1,000 C/1 h/30 MPa) and hot isostatic pressing (1,400 C/2 h/196 MPa). Their composition profiles are greatly influenced by the viscosity of mixed solutions of glycerin and ethanol used as a dispersion medium; a linear compositional gradient from MoSi{sub 2}/ZrO{sub 2}(2Y) = 70/30 to {approximately}20/80 mol% is obtained from the solution (50/50 vol%) with a viscosity of {approximately}20 mPa{center_dot}s. Vickers hardness (H{sub v}) and fracture toughness (K{sub IC}) increase from 9.7 to 12.4 GPa and from 5.1 to 12.5 MPa{center_dot}m{sup 1/2}, respectively, with increasing ZrO{sub 2}(2Y) composition.

  9. Remarkable promotion effect of trace sulfation on OMS-2 nanorod catalysts for the catalytic combustion of ethanol.

    PubMed

    Zhang, Jie; Zhang, Changbin; He, Hong

    2015-09-01

    OMS-2 nanorod catalysts were synthesized by a hydrothermal redox reaction method using MnSO4 (OMS-2-SO4) and Mn(CH3COO)2 (OMS-2-AC) as precursors. SO4(2-)-doped OMS-2-AC catalysts with different SO4(2-) concentrations were prepared next by adding (NH4)2SO4 solution into OMS-2-AC samples to investigate the effect of the anion SO4(2-) on the OMS-2-AC catalyst. All catalysts were then tested for the catalytic oxidation of ethanol. The OMS-2-SO4 catalyst synthesized demonstrated much better activity than OMS-2-AC. The SO4(2-) doping greatly influenced the activity of the OMS-2-AC catalyst, with a dramatic promotion of activity for suitable concentration of SO4(2-) (SO4/catalyst=0.5% W/W). The samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma optical emission spectroscopy (ICP-OES), NH3-TPD and H2-TPR techniques. The results showed that the presence of a suitable amount of SO4(2-) species in the OMS-2-AC catalyst could decrease the Mn-O bond strength and also enhance the lattice oxygen and acid site concentrations, which then effectively promoted the catalytic activity of OMS-2-AC toward ethanol oxidation. Thus it was confirmed that the better catalytic performance of OMS-2-SO4 compared to OMS-2-AC is due to the presence of some residual SO4(2-) species in OMS-2-SO4 samples. Copyright © 2015. Published by Elsevier B.V.

  10. Dermally adhered soil: 2. Reconstruction of dry-sieve particle-size distributions from wet-sieve data.

    PubMed

    Choate, LaDonna M; Ranville, James F; Bunge, Annette L; Macalady, Donald L

    2006-10-01

    In the evaluation of soil particle-size effects on environmental processes, particle-size distributions are measured by either wet or dry sieving. Commonly, size distributions determined by wet and dry sieving differ because some particles disaggregate in water. Whereas the dry-sieve distributions are most relevant to the study of soil adherence to skin, soil can be recovered from skin only by washing with the potential for disaggregation whether or not it is subsequently wet or dry sieved. Thus, the possibility exists that wet-sieving measurements of the particle sizes that adhered to the skin could be skewed toward the smaller fractions. This paper provides a method by which dry-sieve particle-size distributions can be reconstructed from wet-sieve particle-size distributions for the same soil. The approach combines mass balances with a series of experiments in which wet sieving was applied to dry-sieve fractions from the original soil. Unless the soil moisture content is high (i.e., greater than or equal to the water content after equilibration with water-saturated air), only the soil particles of diameters less than about 63 microm adhere to the skin. Because of this, the adhering particle-size distribution calculated using the reconstruction method was not significantly different from the wet-sieving determinations.

  11. Asymmetric Construction of Functionalized 1,2-Dihydropyridine and Pyridine Derivatives with Adjacent Stereocenters via a Unified Metal-Free Catalytic Approach.

    PubMed

    Zou, Gong-Feng; Zhang, Shi-Qiang; Wang, Jia-Xin; Liao, Wei-Wei

    2016-07-01

    A novel asymmetric catalytic approach for the construction of enantioenriched functionalized 1,2-dihydropyridines and pyridine derivatives incorporating adjacent quaternary and tertiary stereocenters has been reported. This process involved a metal-free catalytic asymmetric allylic alkylation and a stereospecifically nonoxidative aromatization approach for the desired chiral molecules.

  12. Catalytic hetero-ene reactions of 5-methyleneoxazolines: highly enantioselective synthesis of 2,5-disubstituted oxazole derivatives.

    PubMed

    Luo, Weiwei; Zhao, Jiannan; Yin, Chengkai; Liu, Xiaohua; Lin, Lili; Feng, Xiaoming

    2014-07-18

    An efficient catalytic asymmetric hetero-ene reaction of 5-methyleneoxazolines with 1,2-dicarbonyl compounds (including α-ketoesters and glyoxal derivatives) was realized using Ni(II)-N,N'-dioxide complexes as the catalysts. It provides a rapid, high yielding (up to 99%) route for the preparation of 2,5-disubstituted oxazole derivatives in a highly enantioenriched form (up to >99% ee) under mild conditions.

  13. Study on the catalytic activity of vanadium doped TiO2: Anatase-to-rutile phase transition

    NASA Astrophysics Data System (ADS)

    Zhang, Huiming; Bian, He; Zhang, Shiguo

    2016-01-01

    The catalytic activity of vanadium doped TiO2 in the ethylbenzene oxidative dehydrogenation with CO2 was studied experimentally and theoretically. The experimental results showed that the reduction of ethylbenzene conversion and the styrene selectivity was caused by the transition of anatase to rutile phase. Theoretical results showed that the transition of the anatase to rutile phase was mainly caused by vanadium ions and oxygen vacancies.

  14. Leaf Cutter Ant (Atta cephalotes) Soil Modification and In Situ CO2 Gas Dynamics in a Neotropical Wet Forest

    NASA Astrophysics Data System (ADS)

    Fernandez Bou, A. S.; Carrasquillo Quintana, O.; Dierick, D.; Harmon, T. C.; Johnson, S.; Schwendenmann, L.; Zelikova, T. J.

    2016-12-01

    The goal of this work is to advance our understanding of soil carbon cycling in highly productive neotropical wet forests. More specifically, we are investigating the influence of leaf cutter ants (LCA) on soil CO2 gas dynamics in primary and secondary forest soils at La Selva Biological Station, Costa Rica. LCA are the dominant herbivore in tropical Americas, responsible for as much as 50% of the total herbivory. Their presence is increasing and their range is expanding because of forest fragmentation and other human impacts. We installed gas sampling wells in LCA (Atta cephalotes) nest and control sites (non-nests in the same soil and forest settings). The experimental design encompassed land cover (primary and secondary forest) and soil type (residual and alluvial). We collected gas samples monthly over an 18-month period. Several of the LCA nests were abandoned during this period. Nevertheless, we continued to sample these sites for LCA legacy effects. In several of the sites, we also installed sensors to continuously monitor soil moisture content, temperature, and CO2 levels. Within the 18-month period we conducted a 2-month field campaign to collect soil and nest vent CO2 efflux data from 3 of the nest-control pairs. Integrating the various data sets, we observed that for most of the sites nest and control soils behaved similarly during the tropical dry season. However, during the wet season gas well CO2 concentrations increased in the control sites while levels in the nests remained at dry season levels. This outcome suggests that ants modify soil gas transport properties (e.g., tortuosity). In situ time series and efflux sampling campaign data corroborated these findings. Abandoned nest CO2 levels were similar to those of the active nests, supporting the notion of a legacy effect from LCA manipulations. For this work, the period of abandonment was relatively short (several months to 1 year maximum), which appears to be insufficient for estimating the

  15. Changes in wetting properties of silica surface treated with DPPC in the presence of phospholipase A 2 enzyme

    NASA Astrophysics Data System (ADS)

    Wiącek, Agnieszka Ewa

    2010-10-01

    Wetting properties of silica plates contacted with dipalmitoylphosphatidylcholine (DPPC) or DPPC/enzyme (phospholipase PLA 2) in NaCl solution were determined by thin layer wicking and with a help of Washburn equation. The wicking experiments were performed both for bare plates and the silica plates precontacted overnight with the probe liquid saturated vapors the silica plates, as well as untreated and DPPC (or DPPC/enzyme) treated. Adsorption of DPPC on original silica plates increases a bit hydrophobic character of silica surface in such a way that hydrocarbon chains are directed outwards and the polar part towards the silica surface. However, after the enzyme action the products of DPPC hydrolysis by PLA 2 (palmitic acid and lysophosphatidylcholine) increase again hydrophilic character of silica surface (an increase in acid-base interactions, γsAB). The changes of silica surface wettability are evidently dependent on the time of enzyme contacting with DPPC in NaCl solution. Although, the changes of total surface free energy of silica after treatment with DPPC/enzyme solution are minor about 2-6 mJ/m 2, the changes of the electron-donor ( γs-) and Lifshitz-van der Waals ( γsLW) component of the surface free energy are noticeable. Despite, these results are somehow preliminary, it seems that thin layer wicking method is an interesting tool for investigation of the effect of adsorbed DPPC on hydrophobicity/hydrophilicity of silica surface and influence of enzyme PLA 2 action.

  16. Inhibition of DOI-induced wet dog shakes in the guinea-pig by 5-HT2 receptor antagonists.

    PubMed

    Skingle, M; Cole, N; Higgins, G; Feniuk, W

    1991-01-01

    The preferential 5-HT( 2)/5-HT(1C) receptor agonist DOI (0.1-4 mg/kg s.c.) caused an increase in locomotor activity, grooming and 'wet-dog' shakes (WDS) in the adult guinea-pig. The DOI-induced WDS behaviour was potently inhibited by several antagonists that have high affinity for the 5-HT(2) binding site. The WDS response is likely to be centrally-mediated since the effects of peripherally administered DOI were poorly antagonized by the peripherally-acting 5-HT(2) receptor antagonist BW501C67. Although these studies do not exclude an effect of DOI at 5-HT(1C) receptors, the high potency of ketanserin and spiperone in attenuating the effects of DOI would suggest an effect at the 5-HT(2) receptor. The present data suggest that antagonism of the directly-acting agonist DOI may be useful for assessing the selectivity and duration of action of centrally-acting 5-HT(2) receptor antagonists in the guinea-pig.

  17. Dependence of Protein Adsorption on Wetting Behavior of UHMWPE-HA-Al2O3-CNT Hybrid Biocomposites

    NASA Astrophysics Data System (ADS)

    Gupta, Ankur; Tripathi, Garima; Basu, Bikramjit; Balani, Kantesh

    2012-04-01

    Ultrahigh-molecular-weight polyethylene (UHMWPE) is used as an articulating surface in total hip and knee joint replacement. In order to enhance long-term durability/wear resistance properties, UHMWPE-based polymer-ceramic hybrid composites are being developed. Surface properties such as wettability and protein adsorption alter with reinforcement or with change in surface chemistry. From this perspective, the wettability and protein adsorption behavior of compression-molded UHMWPE-hydroxyapatite (HA)-aluminum oxide (Al2O3)-carbon nanotube (CNT) composites were analyzed in conjunction with surface roughness. The combined effect of Al2O3 and CNT shows enhancement of the contact angle by ~37° compared with the surface of the UHMWPE matrix reinforced with HA. In reference to unreinforced UHMWPE, protein adsorption density also increased by ~230% for 2 wt.%HA-5 wt.%Al2O3-2 wt.%CNT addition to UHMWPE. An important conclusion is that the polar and dispersion components of the surface free energy play a significant role in wetting and protein adsorption than do the total free energy or chemistry of the surface. The results of this study have major implications for the biocompatibility of these newly developed biocomposites.

  18. Surface Acidity as Descriptor of Catalytic Activity for Oxygen Evolution Reaction in Li-O2 Battery.

    PubMed

    Zhu, Jinzhen; Wang, Fan; Wang, Beizhou; Wang, Youwei; Liu, Jianjun; Zhang, Wenqing; Wen, Zhaoyin

    2015-10-28

    Unraveling the descriptor of catalytic activity, which is related to physical properties of catalysts, is a major objective of catalysis research. In the present study, the first-principles calculations based on interfacial model were performed to study the oxygen evolution reaction mechanism of Li2O2 supported on active surfaces of transition-metal compounds (TMC: oxides, carbides, and nitrides). Our studies indicate that the O2 evolution and Li(+) desorption energies show linear and volcano relationships with surface acidity of catalysts, respectively. Therefore, the charging voltage and desorption energies of Li(+) and O2 over TMC could correlate with their corresponding surface acidity. It is found that certain materials with an appropriate surface acidity can achieve the high catalytic activity in reducing charging voltage and activation barrier of rate-determinant step. According to this correlation, CoO should have as active catalysis as Co3O4 in reducing charging overpotential, which is further confirmed by our comparative experimental studies. Co3O4, Mo2C, TiC, and TiN are predicted to have a relatively high catalytic activity, which is consistent with the previous experiments. The present study enables the rational design of catalysts with greater activity for charging reactions of Li-O2 battery.

  19. Non-catalytic transfer hydrogenation in supercritical CO2 for coal liquefaction

    NASA Astrophysics Data System (ADS)

    Elhussien, Hussien

    This thesis presents the results of the investigation on developing and evaluating a low temperature (<150°C) non - catalytic process using a hydrogen transfer agent (instead of molecu-lar hydrogen) for coal dissolution in supercritical CO2. The main idea behind the thesis was that one hydrogen atom from water and one hydrogen atom from the hydrogen transfer agent (HTA) were used to hydrogenate the coal. The products of coal dissolution were non-polar and polar while the supercritical CO2, which enhanced the rates of hydrogenation and dissolution of the non-polar molecules and removal from the reaction site, was non-polar. The polar modifier (PM) for CO2 was added to the freed to aid in the dissolution and removal of the polar components. The addition of a phase transfer agent (PTA) allowed a seamless transport of the ions and by-product between the aqueous and organic phases. DDAB, used as the PTA, is an effective phase transfer catalyst and showed enhancement to the coal dissolution process. COAL + DH- +H 2O → COAL.H2 + DHO-- This process has a great feature due to the fact that the chemicals were obtained without requir-ing to first convert coal to CO and H2 units as in indirect coal liquefaction. The experiments were conducted in a unique reactor set up that can be connected through two lines. one line to feed the reactor with supercritical CO 2 and the other connected to gas chromatograph. The use of the supercritical CO2 enhanced the solvent option due to the chemical extraction, in addition to the low environmental impact and energy cost. In this thesis the experiment were conducted at five different temperatures from atmos-pheric to 140°C, 3000 - 6000 psi with five component of feed mixture, namely water, HTA, PTA, coal, and PM in semi batch vessels reactor system with a volume of 100 mL. The results show that the chemicals were obtained without requiring to first convert coal to CO and H2 units as in indirect coal liquefaction. The results show that

  20. Synthesis, characterization, and catalytic applications of hematite (α-Fe2O3) nanoparticles as reusable nanocatalyst

    NASA Astrophysics Data System (ADS)

    Basavegowda, Nagaraj; Mishra, Kanchan; Rok Lee, Yong

    2017-06-01

    A novel magnetically recoverable hematite nanoparticles (α-Fe2O3 NPs) was fabricated by a simple, one pot, and green method using the rhizome of Cyperus rotundus L., as a reducing and stabilizing agent. The prepared nanoparticles were well characterized by all parameters. TEM showed that the hematite nanoparticles had a rhombohedral shape and ranged in size from 80 to 100 nm. The phase study of the α-Fe2O3 nanoparticles was confirmed by Raman spectroscopy. In addition, the synthesized nanoparticles shows good photocatalytic activity in degradation of highly toxic Congo red dye within 25 min, and the same NPs exhibits higher catalytic activity for the reduction of 4-nitro-o-phenylenediamine (4-NPD) to 1,2,4-benzenetriamine in the presence of NaBH4 within 12 min. After the reaction, the catalyst was recovered and reused three times without significant loss of catalytic activity.

  1. Z-selective, catalytic internal alkyne semihydrogenation under H2/CO mixtures by a niobium(III) imido complex.

    PubMed

    Gianetti, Thomas L; Tomson, Neil C; Arnold, John; Bergman, Robert G

    2011-09-28

    The discovery of a Nb(III)-mediated catalytic hydrogenation of internal alkynes to (Z)-alkenes that proceeds through an unprecedented mechanism is reported. The mechanistic proposal involves initial reduction of the alkyne by the Nb(III) complex (BDI)Nb(N(t)Bu)(CO)(2) to provide a Nb(V) metallacyclopropene, itself capable of σ-bond metathesis reactivity with H(2). The resulting alkenyl hydride species then undergoes reductive elimination to provide the (Z)-alkene product and regenerate a metal complex in the Nb(III) oxidation state. Support for the proposed mechanism is derived from (i) the dependence of the product selectivity on the relative concentrations of CO and H(2), (ii) the isolation of complexes closely related to those proposed to be part of the catalytic cycle, (iii) H/D crossover experiments, and (iv) DFT studies of multiple possible reaction pathways.

  2. Preparation of magnetic Co/graphene sheets composites and investigation on its catalytic activity for H2 generation

    NASA Astrophysics Data System (ADS)

    Zhao, Dongcui; Nan, Zhaodong

    2016-12-01

    A cobalt (Co)/graphene sheets (GRs) composite was synthesized via a one-pot chemical method. The composite shows high saturation magnetizations (Ms), which leads it to be conveniently separated from aqueous solution by an external magnetic field. Compared to the pure Co and some references, the catalytic activity of the as-obtained composite was significantly enhanced for the generation of H2 gas by hydrolysis of NaBH4 solution. Effects of NaBH4 initial concentration, the composite and reaction temperature on the H2 generation rate were investigated. The H2 generation rate is independent with the initial NaBH4 concentration, increased with the reaction temperature increasing. The composite can be continuously used several times with about the same catalytic activity.