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1

Biochar based solid acid catalyst for biodiesel production  

Microsoft Academic Search

A promising catalyst based on a biomass pyrolysis by-product, biochar, has been developed for the production of biodiesel. Two carbon-based solid acid catalysts were prepared by sulfonating pyrolysis char with concentrated or fuming sulfuric acids. Prepared catalysts were studied for their ability to catalyze transesterification of vegetable oils and esterification of free fatty acids. The catalyst sulfonated with the concentrated

Amir Mehdi Dehkhoda; Alex H. West; Naoko Ellis

2010-01-01

2

Mesoporous Silica Supported Solid Acid Catalysts  

SciTech Connect

In this brief proceedings paper, we summarize the results of recent studies of the preparation and characterization of mesoporous silica supported tungstophosphoric acid (TPA/MS) and Cs-substituted tungstophosphoric acid salt (Cs-TPA/MS). In particular, we demonstrate that we have synthesized MS-supported Cs-substituted catalysts having significantly improved dispersion of the active clusters compared to materials described previously in the literature. Transmission electron micrographs and the activity results for a model reaction, the alkylation of 1,3,5-trimethylbenzene by cyclohexene are presented as evidence for the enhanced dispersion and performance. In addition, we demonstrate improvements in the physical and thermal stability of these materials with Cs substitution using various characterization techniques. Finally, we also briefly describe the characterization and catalytic activity of TPA/MS materials, providing evidence for shape selectivity that is likely imparted by the structure of the MS support. The promising results with TPA/MS and Cs-TPA/MS catalysis indicate that they have potential applications in a variety of acid-catalyzed organic reactions involving large-sized reacting, intermediate, and/or product molecules with desired shape selectivity to products and/or intermediates.

Choi, Saemin (ASSOC WESTERN UNIVERSITY); Wang, Yong (BATTELLE (PACIFIC NW LAB)); Nie, Zimin (BATTELLE (PACIFIC NW LAB)); Khmbapati, D (N/A); Liu, Jun (BATTELLE (PACIFIC NW LAB)); Peden, Charles HF (BATTELLE (PACIFIC NW LAB)); A. Corma, F.Melo, S. Mendioroz et al

2000-01-01

3

Solid acid catalysts: Stain and shine  

NASA Astrophysics Data System (ADS)

Catalyst particles for fluid catalytic cracking are vital for the oil-refinery industry, but their activity is hard to diagnose because of their inter- and intra-particle structural inhomogeneity. With fluorescence confocal microscopy and selective staining, one can now pinpoint the catalytic activity within single catalyst particles from an industrial reactor.

Chen, Peng

2011-11-01

4

Hydrolysis of oligosaccharides over solid acid catalysts: a review.  

PubMed

Mild fractionation/pretreatment processes are becoming the most preferred choices for biomass processing within the biorefinery framework. To further explore their advantages, new developments are needed, especially to increase the extent of the hydrolysis of poly- and oligosaccharides. A possible way forward is the use of solid acid catalysts that may overcome many current drawbacks of other common methods. In this Review, the advantages and limitations of the use of heterogeneous catalysis for the main groups of solid acid catalysts (zeolites, resins, carbon materials, clays, silicas, and other oxides) and their relation to the hydrolysis of model soluble disaccharides and soluble poly- and oligosaccharides are presented and discussed. Special attention is given to the hydrolysis of hemicelluloses and hemicellulose-derived saccharides into monosaccharides, the impact on process performance of potential catalyst poisons originating from biomass and biomass hydrolysates (e.g., proteins, mineral ions, etc.). The data clearly point out the need for studying hemicelluloses in natura rather than in model compound solutions that do not retain the relevant factors influencing process performance. Furthermore, the desirable traits that solid acid catalysts must possess for the efficient hemicellulose hydrolysis are also presented and discussed with regard to the design of new catalysts. PMID:24616436

Vilcocq, Léa; Castilho, Paula C; Carvalheiro, Florbela; Duarte, Luís C

2014-04-01

5

Solid acids and their use as environmentally friendly catalysts in organic synthesis  

Microsoft Academic Search

Tightening environmental legislation is driving the fine and speciality chemicals industries to consider alternative processes that avoid the use of conventional mineral acids. The use of heterogeneous catalysts in these processes would vastly simplify catalyst removal, minimizing the amount of waste formed. However, diffusion limitation of liquids within porous solids dictates that effective solid acids for liquid-phase reactions require the

Karen Wilson; James H. Clark

2000-01-01

6

Role of solid acid catalysts in bio diesel production.  

PubMed

Biodiesel is gaining importance as an alternate source of attractive fuel because of depleting fossil fuel resources. It is produced by trans-esterification, in which oil or fat reacts with a monohydric alcohol in presence of a catalyst. In the present work, trans-esterification of sunflower oil with methanol is carried out by using zirconia supported isopoly and heteropoly tungstates (HPAs) as catalysts. Effects of reaction parameters, such as catalyst types and its concentration, molar ratio of sunflower oil to methanol, reaction temperature and time, have been optimized to get higher conversion of sunflower oil and the product distribution of fatty acid methyl esters (FAME) in the trans-esterfication reaction. PMID:21117436

Shivayogimath, C B; Sunita, G; Manoj Kumar, B

2009-07-01

7

Synthesis of biodiesel from a model waste oil feedstock using a carbon-based solid acid catalyst: Reaction and separation  

Microsoft Academic Search

A solid acid catalyst that can keep high activity and stability is necessary when low cost feedstocks are utilized for biodiesel synthesis because the reaction medium contains a large amount of water. Three solid acid catalysts were prepared by the sulfonation of carbonized vegetable oil asphalt and petroleum asphalt. The structure of these catalysts was characterized by a variety of

Qing Shu; Zeeshan Nawaz; Jixian Gao; Yuhui Liao; Qiang Zhang; Dezheng Wang; Jinfu Wang

2010-01-01

8

Topics in Catalysis 6 (1998) 8799 87 Solid acid catalysts based on supported tungsten oxides  

E-print Network

clusters are active and stable catalysts for isomerization, dehydration, and cracking reactions. Brønsted slightly during catalytic reactions. WOx clusters of intermediate size provide the balance between acid sites during catalytic reactions on WOx clusters. Keywords: tungsten oxides, solid acids, acid

Iglesia, Enrique

9

Application of Supercritical Fluids to Solid Acid Catalyst Alkylation and Regeneration  

SciTech Connect

Supercritical fluid (SCF) regeneration is a promising alternative method for regenerating solid catalysts deactivated by carbonaceous deposits. The unique solvent and transport properties of SCFs such as solvent strength similar to liquids and transport properties similar to gases make them highly suitable for extraction of fouling materials from porous heterogeneous catalysts. A brief review of the research work performed at the Idaho National Laboratory (INL) on the application of supercritical fluids to both isobutane/butene alkylation reaction and solid acid catalyst regeneration is presented in this contribution.

Lucia M. Petkovic; Daniel M. Ginosar; David N. Thompson; Kyle C. Burch

2007-05-01

10

A solid acid esterification catalyst which reduces waste and increases yields  

SciTech Connect

Recent research on polymeric catalysts has led to the development of a new solid acid esterification catalyst which is highly active for the esterification of fatty acids and maleic anhydride at elevated temperatures. The use of this catalyst eliminates the need for a final neutralization step which is required when using traditional homogenous acid (H{sub 2}SO{sub 4} and HCl) catalysts. This neutralization step generates large amounts of waste salts and hurts efficiency since unconsumed organic acid reactants are also neutralized. In the high temperature esterification reactions studied here, the production of dialkyl ether by-products from the acid catalyzed self-condensation of alcohol is also greatly reduced allowing for both high activity and selectivity.

Lundquist, E.G. [Rohm and Haas Co., Spring House, PA (United States)

1993-12-31

11

A microalgae residue based carbon solid acid catalyst for biodiesel production.  

PubMed

Biodiesel production from microalgae is recognized as one of the best solutions to deal with the energy crisis issues. However, after the oil extraction from the microalgae, the microalgae residue was generally discarded or burned. Here a novel carbon-based solid acid catalyst derived from microalgae residue by in situ hydrothermal partially carbonization were synthesized. The obtained catalyst was characterized and subjected to both the esterification of oleic acid and transesterification of triglyceride to produce biodiesel. The catalyst showed high catalytic activity and can be regenerated while its activity can be well maintained after five cycles. PMID:23953130

Fu, Xiaobo; Li, Dianhong; Chen, Jie; Zhang, Yuanming; Huang, Weiya; Zhu, Yi; Yang, Jun; Zhang, Chengwu

2013-10-01

12

Novel Solid Acid Catalyst, Bentonite-Supported Polytrifluoromethanesulfosiloxane for Friedel–Crafts Acylation of Ferrocene  

Microsoft Academic Search

Solid acid catalyst, bentonite-supported polytrifluoromethanesulfosiloxane (B-PTFMSS) has been for the first time prepared and used in the Friedel–Crafts acylation of ferrocene with various acyl chlorides. The catalytic activities were influenced by reaction time, reaction temperature, solvent and loaded amount of B-PTFMSS. It was found that the new catalyst B-PTFMSS possessed the advantages of high activities giving similar yield of aliphatic

Rui-Jue Hu; Bao-Guo Li

2004-01-01

13

Catalysis science of the solid acidity of model supported tungsten oxide catalysts  

Microsoft Academic Search

A series of supported WO3 catalysts were synthesized by incipient wetness impregnation of ammonium metatungstate aqueous solutions onto Al2O3, TiO2, Nb2O5, and ZrO2 supports as a function of tungsten oxide loading. The resulting solid acid catalysts were physically characterized with in situ Raman and UV–vis spectroscopy and chemically probed by methanol dehydration to dimethyl ether (CH3OH-TPSR and steady-state CH3OH dehydration).

Israel E. Wachs; Taejin Kim; Elizabeth I. Ross

2006-01-01

14

Alkene Isomerization Using a Solid Acid as Activator and Support for a Homogeneous Catalyst  

ERIC Educational Resources Information Center

An upper-level undergraduate experiment that, in addition to introducing students to catalysis using an air sensitive transition-metal complex, introduces the use of a solid acid as an activator and support for the catalyst is developed. The increased stability acquired in the course of the process affords the opportunity to characterize the…

Seen, Andrew J.

2004-01-01

15

SYNTHESIS OF COUMARINS CATALYZED BY ECO-FRIENDLY W\\/ZrO2 SOLID ACID CATALYST  

Microsoft Academic Search

Synthesis of substituted coumarins via reactions of resorcinol and substituted resorcinol with ethyl acetoacetate and ethyl ?-methylacetoacetate (Pechmann reaction) are reported, in which the production of environmentally harmful waste streams is minimized by the use of a novel solid acid catalyst.

Benjaram M. Reddy; Vangala R. Reddy; D. Giridhar

2001-01-01

16

A highly active bagasse-derived solid acid catalyst with properties suitable for production of biodiesel.  

PubMed

A novel bagasse-based solid acid catalyst was successfully prepared through sulfonation of incompletely carbonized bagasse. A range of conditions for producing the catalyst were investigated, and the optimized catalyst, produced under carbonization at 648 K for 0.5 h and sulfonation at 423 K for 15 h, showed excellent catalytic activity and resulted in around 95 % yield of methyl oleate. Its activity was not only substantially greater than that of niobic acid and Amberlyst-15, but also comparable to or superior to that of catalysts made from pure starch or glucose, respectively. Additionally, the bagasse-derived catalyst could be repeatedly employed for at least eight cycles and still retained around 90 % of its original activity, exhibiting excellent operational stability. Furthermore, the catalyst efficiently converted waste cooking oils with 38.6 wt % free fatty acids into biodiesel and afforded a high yield of about 93.8 % within 12 h. These results clearly show that the bagasse-derived catalyst is economic, eco-friendly, and promising for biodiesel production from low-cost feedstocks and may find wide applications. PMID:22693163

Lou, Wen-Yong; Guo, Qiang; Chen, Wen-Jing; Zong, Min-Hua; Wu, Hong; Smith, Thomas J

2012-08-01

17

Synthesis of biodiesel from waste vegetable oil with large amounts of free fatty acids using a carbon-based solid acid catalyst  

Microsoft Academic Search

A carbon-based solid acid catalyst was prepared by the sulfonation of carbonized vegetable oil asphalt. This catalyst was employed to simultaneously catalyze esterification and transesterification to synthesis biodiesel when a waste vegetable oil with large amounts of free fatty acids (FFAs) was used as feedstock. The physical and chemical properties of this catalyst were characterized by a variety of techniques.

Qing Shu; Jixian Gao; Zeeshan Nawaz; Yuhui Liao; Dezheng Wang; Jinfu Wang

2010-01-01

18

Esterification by ZrO2 and Mo-ZrO2 ECO-Friendly Solid Acid Catalysts  

Microsoft Academic Search

Esterification of mono-and dicarboxylic acids catalysed by single (ZrO2) and mixed oxide (Mo-ZrO2) eco-friendly solid acid catalysts is described. The Mo-ZrO2 catalyst exhibits better catalytic performance than ZrO2.

Basude Manohar; Vangala R. Reddy; Benjaram M. Reddy

1998-01-01

19

Direct production of biodiesel from high-acid value Jatropha oil with solid acid catalyst derived from lignin  

PubMed Central

Background Solid acid catalyst was prepared from Kraft lignin by chemical activation with phosphoric acid, pyrolysis and sulfuric acid. This catalyst had high acid density as characterized by scanning electron microscope (SEM), energy-dispersive x-ray spectrometry (EDX) and Brunauer, Emmett, and Teller (BET) method analyses. It was further used to catalyze the esterification of oleic acid and one-step conversion of non-pretreated Jatropha oil to biodiesel. The effects of catalyst loading, reaction temperature and oil-to-methanol molar ratio, on the catalytic activity of the esterification were investigated. Results The highest catalytic activity was achieved with a 96.1% esterification rate, and the catalyst can be reused three times with little deactivation under optimized conditions. Biodiesel production from Jatropha oil was studied under such conditions. It was found that 96.3% biodiesel yield from non-pretreated Jatropha oil with high-acid value (12.7 mg KOH/g) could be achieved. Conclusions The catalyst can be easily separated for reuse. This single-step process could be a potential route for biodiesel production from high-acid value oil by simplifying the procedure and reducing costs. PMID:22145867

2011-01-01

20

Catalytic cracking of a polyolefin mixture over different acid solid catalysts  

Microsoft Academic Search

Catalytic cracking of a polyolefin mixture consisting of polypropylene and both low- and high-density polyethylene has been studied at 400 C over a variety of acid solids as catalysts. The highest activities were obtained over HMCM-41, n-HZSM-5 zeolite, with nanometer crystal size, and HBeta zeolite. The high surface area and large pores present in HMCM-41 are responsible for the high

David P. Serrano; José Aguado; José M. Escola

2000-01-01

21

Catalytic hydrothermal pretreatment of corncob into xylose and furfural via solid acid catalyst.  

PubMed

Selectively catalytic hydrothermal pretreatment of corncob into xylose and furfural has been developed in this work using solid acid catalyst (SO4(2-)/TiO2-ZrO2/La(3+)). The effects of corncob-to-water ratio, reaction temperature and residence time on the performance of catalytic hydrothermal pretreatment were investigated. Results showed that the solid residues contained mainly lignin and cellulose, which was indicative of the efficient removal of hemicelluloses from corncob by hydrothermal method. The prepared catalyst with high thermal stability and strong acid sites originated from the acid functional groups was confirmed to contribute to the hydrolysis of polysaccharides into monosaccharides followed by dehydration into furfural. Highest furfural yield (6.18 g/100g) could be obtained at 180°C for 120 min with 6.80 g/100g xylose yield when the corncob/water ratio of was 10:100. Therefore, selectively catalytic hydrothermal pretreatment of lignocellulosic biomass into important platform chemicals by solid acids is considered to be a potential treatment for biodiesel and chemical production. PMID:24632409

Li, Huiling; Deng, Aojie; Ren, Junli; Liu, Changyu; Lu, Qi; Zhong, Linjie; Peng, Feng; Sun, Runcang

2014-04-01

22

31P chemical shift of adsorbed trialkylphosphine oxides for acidity characterization of solid acids catalysts.  

PubMed

A comprehensive study has been made to predict the adsorption structures and (31)P NMR chemical shifts of various trialkylphosphine oxides (R3PO) probe molecules, viz., trimethylphosphine oxide (TMPO), triethylphosphine oxide (TEPO), tributylphosphine oxide (TBPO), and trioctylphosphine oxide (TOPO), by density functional theory (DFT) calculations based on 8T zeolite cluster models with varied Si-H bond lengths. A linear correlation between the (31)P chemical shifts and proton affinity (PA) was observed for each of the homologous R3PO probe molecules examined. It is found that the differences in (31)P chemical shifts of the R3POH(+) adsorption complexes, when referring to the corresponding chemical shifts in their crystalline phase, may be used not only in identifying Brønsted acid sites with varied acid strengths but also in correlating the (31)P NMR data obtained from various R3PO probes. Such a chemical shift difference therefore can serve as a quantitative measure during acidity characterization of solid acid catalysts when utilizing (31)P NMR of various adsorbed R3PO, as proposed in our earlier report (Zhao; et al. J. Phys. Chem. B 2002, 106, 4462) and also illustrated herein by using a mesoporous H-MCM-41 aluminosilicate (Si/Al = 25) test adsorbent. It is indicative that, with the exception of (TMPO), variations in the alkyl chain length of the R3PO (R = C(n)H(2n+1); n > or = 2) probe molecules have only negligible effect on the (31)P chemical shifts (within experimental error of ca. 1-2 ppm) either in their crystalline bulk or in their corresponding R3POH(+) adsorption complexes. Consequently, an average offset of 8 +/- 2 ppm was observed for (31)P chemical shifts of adsorbed R3PO with n > or = 2 relative to TMPO (n = 1). Moreover, by taking the value of 86 ppm predicted for TMPO adsorbed on 8T cluster models as a threshold for superacidity (Zheng; et al. J. Phys. Chem. B 2008, 112, 4496), a similar threshold (31)P chemical shift of ca. 92-94 ppm was deduced for TEPO, TBPO, and TOPO. PMID:18646739

Zheng, Anmin; Huang, Shing-Jong; Chen, Wen-Hua; Wu, Pei-Hao; Zhang, Hailu; Lee, Huang-Kuei; de Ménorval, Louis-Charles; Deng, Feng; Liu, Shang-Bin

2008-08-14

23

Synthesis of biodiesel from a model waste oil feedstock using a carbon-based solid acid catalyst: reaction and separation.  

PubMed

A solid acid catalyst that can keep high activity and stability is necessary when low cost feedstocks are utilized for biodiesel synthesis because the reaction medium contains a large amount of water. Three solid acid catalysts were prepared by the sulfonation of carbonized vegetable oil asphalt and petroleum asphalt. The structure of these catalysts was characterized by a variety of techniques. A new process that used the coupling of the reaction and separation was employed, which greatly improved the conversion of cottonseed oil (triglyceride) and free fatty acids (FFA) when a model waste oil feedstock was used. The vegetable oil asphalt-based catalyst showed the highest catalytic activity. This was due to the high density and stability of its acid sites, its loose irregular network, its hydrophobicity that prevented the hydration of -OH species, and large pores that provided more acid sites for the reactants. PMID:20219353

Shu, Qing; Nawaz, Zeeshan; Gao, Jixian; Liao, Yuhui; Zhang, Qiang; Wang, Dezheng; Wang, Jinfu

2010-07-01

24

Sulfonated mesoporous silica-carbon composites and their use as solid acid catalysts  

NASA Astrophysics Data System (ADS)

The synthesis of highly functionalized porous silica-carbon composites made up of sulfonic groups attached to a carbon layer coating the pores of three types of mesostructured silica (i.e. SBA-15, KIT-6 and mesocellular silica) is presented. The synthesis procedure involves the following steps: (a) removal of the surfactant, (b) impregnation of the silica pores with a carbon precursor, (c) carbonization and (d) sulfonation. The resulting silica-carbon composites contain ˜30 wt % of carbonaceous matter with a high density of acidic groups attached to the deposited carbon (i.e.sbnd SO3H, sbnd COOH and sbnd OH). The structural characteristics of the parent silica are retained in the composite materials, which exhibit a high surface area, a large pore volume and a well-ordered porosity made up uniform mesopores. The high density of the sulfonic groups in combination with the mesoporous structure of the composites ensures that a large number of active sites are easily accessible to reactants. These sulfonated silica-carbon composites behave as eco-friendly, active, selective, water tolerant and recyclable solid acids. In this study we demonstrate the usefulness of these composites as solid acid catalysts for the esterification of maleic anhydride, succinic acid and oleic acid with ethanol. These composites exhibit a superior intrinsic catalytic activity to other commercial solid acids such as Amberlyst-15.

Valle-Vigón, Patricia; Sevilla, Marta; Fuertes, Antonio B.

2012-11-01

25

Sulfamic acid: an efficient, cost-effective and recyclable solid acid catalyst for the three-component synthesis of ?-amino nitriles  

Microsoft Academic Search

?-Amino nitriles are synthesized by the three-component coupling reaction of aldehydes, amines and trimethylsilyl cyanide using sulfamic acid as a heterogeneous solid acid catalyst, under solvent-free conditions in excellent yields. The catalyst was recovered by simple filtration and was recycled in subsequent reactions.

Akbar Heydari; Samad Khaksar; Mehrdad Pourayoubi; Ali Reza Mahjoub

2007-01-01

26

Efficient solid acid catalyst containing Lewis and Brønsted Acid sites for the production of furfurals.  

PubMed

Self-assembled nanoparticulates of porous sulfonated carbonaceous TiO2 material that contain Brønsted and Lewis acidic sites were prepared by a one-pot synthesis method. The material was characterized by XRD, FTIR spectroscopy, NH3 temperature-programmed desorption, pyridine FTIR spectroscopy, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, N2 -sorption, atomic absorbance spectroscopy, and inductively coupled plasma optical emission spectroscopy. The carbonaceous heterogeneous catalyst (Glu-TsOH-Ti) with a Brønsted-to-Lewis acid density ratio of 1.2 and more accessible acid sites was effective to produce 5-hydroxymethylfurfural and furfural from biomass-derived mono- and disaccharides and xylose in a biphasic solvent that comprised water and biorenewable methyltetrahydrofuran. The catalyst was recycled in four consecutive cycles with a total loss of only 3?% activity. Thus, Glu-TsOH-Ti, which contains isomerization and dehydration catalytic sites and is based on a cheap and biorenewable carbon support, is a sustainable catalyst for the production of furfurals, platform chemicals for biofuels and chemicals. PMID:24807741

Mazzotta, Michael G; Gupta, Dinesh; Saha, Basudeb; Patra, Astam K; Bhaumik, Asim; Abu-Omar, Mahdi M

2014-08-01

27

Catalytic cracking of a polyolefin mixture over different acid solid catalysts  

SciTech Connect

Catalytic cracking of a polyolefin mixture consisting of polypropylene and both low- and high-density polyethylene has been studied at 400 C over a variety of acid solids as catalysts. The highest activities were obtained over HMCM-41, n-HZSM-5 zeolite, with nanometer crystal size, and HBeta zeolite. The high surface area and large pores present in HMCM-41 are responsible for the high conversions obtained with this catalyst. Likewise, in the case of n-HZSM-5, the presence of a high external surface area enhances its cracking activity, because the zeolite external acid sites are not sterically hindered for the conversion of the bulky polyolefin molecules. Significant differences are observed in the product distribution: n-HZSM-5 shows the highest selectivity toward C{sub 1}--C{sub 4} gaseous hydrocarbons (50 wt %), HBeta leads mainly to liquid hydrocarbons in the range C{sub 5}--C{sub 12} (60 wt %), whereas HMCM-41 yields both C{sub 5}--C{sub 12} (54 wt %) and C{sub 13}--C{sub 30} (32 wt %) fractions. A certain loss of activity of these catalysts has been observed after one cycle of regeneration. For HMCM-41, this phenomenon is caused by both dealumination and particle aggregation that take place during the regeneration treatment.

Serrano, D.P.; Aguado, J.; Escola, J.M.

2000-05-01

28

Esterification of palmitic acid with methanol over tungsten oxide supported on zirconia solid acid catalysts: effect of method of preparation of the catalyst on its structural stability and reactivity  

Microsoft Academic Search

Esterification of palmitic acid with methanol was studied on zirconia supported tungsten oxide solid acid catalysts prepared by both impregnation and co-precipitation methods; the tungsten loading and calcination temperature were varied. These catalysts were characterized by X-ray diffraction for structural elucidation and by temperature-programmed desorption of ammonia for their surface acidity. Whereas the impregnated catalysts exhibited both tetragonal and monoclinic

Sridarala Ramu; N. Lingaiah; B. L. A. Prabhavathi Devi; R. B. N. Prasad; I. Suryanarayana; P. S. Sai Prasad

2004-01-01

29

The Origin of Regioselectivity in 2-butanol Dehydration on Solid Acid Catalysts  

SciTech Connect

The origin in the variations of trans-/cis-2-butene product selectivity ratios in 2-butanol dehydration over solid acid catalysts were investigated using a combined experimental-theory approach. Reactivity measurements over ?-Al2O3, AlOx/SBA-15, and H-form zeolites with widely varying Si/Al ratios and pore structures showed over two orders of magnitude change in the trans-/cis-2-butene product ratio. Activation energy barriers calculated for the concerted C-O and ?-C-H bond breakings of adsorbed butoxy intermediates by dispersion-corrected DFT calculations correctly predicted the trans-/cis-2-butene product ratio observed on ?-Al2O3. The very low trans-2-butene selectivity on ?-Al2O3 can now be understood by the formation of a late transition state with high energy barrier caused by the strong van der Waals interaction between the ?-H atoms and the flat catalyst surface. Decreasing the dispersive attractive force between the adsorbed butoxide and the surface (e.g., by moving it further away from the support surface in AlOx/SBA-15) leads to almost equimolar formation of the trans- and cis-2-butene isomers. Trans-/cis-2-butene selectivity ratios much higher than that dictated by thermodynamic equilibrium can be achieved by introducing additional geometric constraints around the active catalytic site (e.g., varying the 3D environment around the active center in zeolites). We propose a model to explain the widely varying trans-/cis-2-butene selectivity in 2-butanol dehydration over solid acid catalysts that is consistent with the experimental results in this study. A key outcome of the study is the realization that van der Waals interactions between the reactant and the active catalyst surface must be included in the theoretic models in order to be able to accurately predict product selectivities. This information, in turn, significantly advances our ability to develop catalyst materials with designed active centers in order to achieve desired regioselectivities.

Kwak, Ja Hun; Rousseau, Roger J.; Mei, Donghai; Peden, Charles HF; Szanyi, Janos

2011-10-17

30

Efficient production of biodiesel from high free fatty acid-containing waste oils using various carbohydrate-derived solid acid catalysts.  

PubMed

In the present study, such carbohydrate-derived catalysts have been prepared from various carbohydrates such as d-glucose, sucrose, cellulose and starch. The catalytic and textural properties of the prepared catalysts have been investigated in detail and it was found that the starch-derived catalyst had the best catalytic performance. The carbohydrate-derived catalysts exhibited substantially higher catalytic activities for both esterification and transesterification compared to the two typical solid acid catalysts (sulphated zirconia and Niobic acid), and gave markedly enhanced yield of methyl esters in converting waste cooking oils containing 27.8wt% high free fatty acids (FFAs) to biodiesel. In addition, under the optimized reaction conditions, the starch-derived catalyst retained a remarkably high proportion (about 93%) of its original catalytic activity even after 50 cycles of successive re-use and thus displayed very excellent operational stability. Our results clearly indicate that the carbohydrate-derived catalysts, especially the starch-derived catalyst, are highly effective, recyclable, eco-friendly and promising solid acid catalysts that are highly suited to the production of biodiesel from waste oils containing high FFAs. PMID:18504123

Lou, Wen-Yong; Zong, Min-Hua; Duan, Zhang-Qun

2008-12-01

31

Activity and Evolution of Vapor Deposited Pt-Pd Oxygen Reduction Catalysts for Solid Acid Fuel Cells  

SciTech Connect

The performance of hydrogen fuel cells based on the crystalline solid proton conductor CsH2PO4 is circumscribed by the mass activity of platinum oxygen reduction catalysts in the cathode. Here we report on the first application of an alloy catalyst in a solid acid fuel cell, and demonstrate an activity 4.5 times greater than Pt at 0.8 V. These activity enhancements were obtained with platinum-palladium alloys that were vapor-deposited directly on CsH2PO4 at 210 C. Catalyst mass activity peaks at a composition of 84 at% Pd, though smaller activity enhancements are observed for catalyst compositions exceeding 50 at% Pd. Prior to fuel cell testing, Pd-rich catalysts display lattice parameter expansions of up to 2% due to the presence of interstitial carbon. After fuel cell testing, a Pt-Pd solid solution absent of lattice dilatation and depleted in carbon is recovered. The structural evolution of the catalysts is correlated with catalyst de-activation.

Papandrew, Alexander B [ORNL; Chisholm, Calum R [ORNL; Zecevic, strahinja [LiOx, Inc., Pasadena, California 91106, United States; Veith, Gabriel M [ORNL; Zawodzinski, Thomas A [ORNL

2013-01-01

32

Oil palm trunk and sugarcane bagasse derived solid acid catalysts for rapid esterification of fatty acids and moisture-assisted transesterification of oils under pseudo-infinite methanol.  

PubMed

The use of pseudo-infinite methanol in increasing the rate of esterification and transesterification reactions was studied using oil palm trunk (OPT) and sugarcane bagasse (SCB) derived solid acid catalysts. The catalysts were prepared by incomplete carbonisation at 400°C for 8h, followed by sulfonation at 150°C for 15h and characterised using TGA/DTA, XRD, FT-IR, SEM-EDS, EA and titrimetric determinations of acid sites. Under optimal reaction conditions, the process demonstrated rapid esterification of palmitic acid, with FAME yields of 93% and 94% in 45min for OPT and SCB catalysts, respectively. With the process, moisture levels up to 16.7% accelerated the conversion of low FFA oils by sulfonated carbon catalysts, through moisture-induced violent bumping. Moisture assisted transesterification of palm olein containing 1.78% FFA and 8.33% added water gave FAME yield of 90% in 10h, which was two folds over neat oil. PMID:24561631

Ezebor, Francis; Khairuddean, Melati; Abdullah, Ahmad Zuhairi; Boey, Peng Lim

2014-04-01

33

Sulfuric acid functional zirconium (or aluminum) incorporated mesoporous MCM-48 solid acid catalysts for alkylation of phenol with tert-butyl alcohol  

NASA Astrophysics Data System (ADS)

Several zirconium (or aluminum) incorporated mesoporous MCM-48 solid acid catalysts (SO42-/Zr-MCM-48 and SO42-/Al-MCM-48) were prepared by the impregnation method and their physicochemical properties were characterized by means of XRD, FT-IR, TEM, NH3-TPD and N2 physical adsorption. Also, the catalytic activities of these solid acid catalysts were evaluated by the alkylation of phenol with tert-butyl alcohol. The effect of weight hour space velocity (WHSV), reaction time and reaction temperature on catalytic properties was also studied. The results show that the SO42-/Zr-MCM-48 and SO42-/Al-MCM-48 still have good mesoporous structure and long range ordering. Compared with the Zr (or Al)-MCM-48 samples, SO42-/Zr-MCM-48 and SO42-/Al-MCM-48 solid acid catalysts have strong acidity and exhibit high activities in alkylation reaction of phenol with tert-butyl alcohol. The SO42-/Zr-MCM-48-25 (molar ratio of Si/Zr=0.04) catalyst was found to be the most promising and gave the highest phenol conversion among all catalysts. A maximum phenol conversion of 91.6% with 4-tert-butyl phenol (4-TBP) selectivity of 81.8% was achieved when the molar ratio of tert-butyl alcohol:phenol is 2:1, reaction time is 2 h, the WHSV is 2 h-1 and the reaction temperature is 140 °C.

Jiang, Tingshun; Cheng, Jinlian; Liu, Wangping; Fu, Lie; Zhou, Xuping; Zhao, Qian; Yin, Hengbo

2014-10-01

34

A highly efficient magnetic solid acid catalyst for synthesis of 2,4,5-trisubstituted imidazoles under ultrasound irradiation.  

PubMed

Fe(3)O(4) nanoparticles were prepared by chemical coprecipitation method and subsequently coated with 3-aminopropyltriethoxysilane (APTES) via silanization reaction. Grafting of chlorosulfuric acid on the amino-functionalized Fe(3)O(4) nanoparticles afforded sulfamic acid-functionalized magnetic nanoparticles (SA-MNPs). SA-MNPs was found to be a mild and effective solid acid catalyst for the efficient, one-pot, three-component synthesis of 2,4,5-trisubstituted imidazoles under ultrasound irradiation. This protocol afforded corresponding imidazoles in shorter reaction durations, and in high yields. This green procedure has many obvious advantages compared to those reported in the previous literatures, including avoiding the use of harmful catalysts, easy and quick isolation of the products, excellent yields, short routine, and simplicity of the methodology. PMID:23137656

Safari, Javad; Zarnegar, Zohre

2013-03-01

35

Fructose dehydration to 5-hydroxymethylfurfural over solid acid catalysts in a biphasic system.  

PubMed

Different acidic heterogeneous catalysts like alumina, aluminosilicate, zirconium phosphate, niobic acid, ion-exchange resin Amberlyst-15, and zeolite MOR have been studied in fructose dehydration to 5-hydroxymethylfurfural (HMF). The acidity of these materials was characterized using temperature-programmed desorption of NH? and IR spectroscopy of adsorbed pyridine. The nature and strength of acid sites was shown to play a crucial role in the selectivity towards HMF. Brønsted acid sites in the case of zeolites and ion-exchange resin led to high selectivities in the dehydration of fructose with an increase in selectivity with the addition of an organic phase. Lewis acidity in the case of phosphate and oxides resulted in the intensive production of humins from fructose at the initial stages of the process, whereas organic phase addition did not affect selectivity. PMID:22777706

Ordomsky, Vitaly V; van der Schaaf, John; Schouten, Jaap C; Nijhuis, T Alexander

2012-09-01

36

Synthesis and characterization of sulfonated single-walled carbon nanotubes and their performance as solid acid catalyst  

SciTech Connect

Single-walled carbon nanotubes (SWCNTs) were treated with sulfuric acid at 300 deg. C to synthesize sulfonated SWCNTs (s-SWCNTs), which were characterized by electron microscopy, infrared, Raman and X-ray photoelectron spectroscopy, and thermo analysis. Compared with activated carbon, more sulfonic acid groups can be introduced onto the surfaces of SWCNTs. The high degree ({approx}20 wt%) of surface sulfonation led to hydrophilic sidewalls that allows the SWCNTs to be uniformly dispersed in water and organic solvents. The high surface acidity of s-SWCNTs was demonstrated by NH{sub 3} temperature-programmed desorption technique and tested by an acetic acid esterification reaction catalyzed by s-SWCNTs. The results show that the water-dispersive s-SWCNTs are an excellent solid acid catalyst and demonstrate the potential of SWCNTs in catalysis applications. - Graphical abstract: Sulfonated SWCNTs with 20 wt% -SO{sub 2}OH groups were prepared by a high-temperature H{sub 2}SO{sub 4} process, which transformed the hydrophobic surface of pristine SWCNTs to a hydrophilic surface and provided an excellent performance as solid acid catalyst.

Yu Hao [School of Chemical and Energy Engineering, South China University of Technology, Guangzhou 510641 (China)], E-mail: yuhao@scut.edu.cn; Jin Yuguang; Li Zhili [School of Chemical and Energy Engineering, South China University of Technology, Guangzhou 510641 (China); Peng Feng [School of Chemical and Energy Engineering, South China University of Technology, Guangzhou 510641 (China)], E-mail: cefpeng@scut.edu.cn; Wang Hongjuan [School of Chemical and Energy Engineering, South China University of Technology, Guangzhou 510641 (China)

2008-03-15

37

Eco-friendly heterogeneous solid acids as novel and recyclable catalysts in ionic medium for tetrahydropyranols  

Microsoft Academic Search

A variety of aldehydes and homoallylic alcohols undergo smoothly Prins-cyclization on the surface of solid acids such as H-ZSM-5 zeolite or Amberlyst-15® ion-exchange resin in 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid to afford the corresponding tetrahydropyranols in high yields with cis-diastereoselectivity. The recovered ionic liquid containing solid acid was recycled in subsequent runs without loss of activity.

J. S Yadav; B. V. S Reddy; M. Sridhar Reddy; N Niranjan

2004-01-01

38

Synthesis of a nano-crystalline solid acid catalyst from fly ash and its catalytic performance  

Microsoft Academic Search

The synthesis of nano-crystalline activated fly ash catalyst (AFAC) with crystallite size of 12nm was carried out by chemical and thermal treatment of fly ash, a waste material generated from coal-burning power plants. Fly ash was chemically activated using sulfuric acid followed by thermal activation at 600°C. The variation of surface and Physico-chemical properties of the fly ash by activation

Chitralekha Khatri; Ashu Rani

2008-01-01

39

Reactions of aqueous glucose solution over solid-acid Y-zeolite catalyst at 110-160 C  

SciTech Connect

Reactions of glucose with solid-acid Y-zeolite catalyst were studied to see if this heterogeneous system could produce oxygenated hydrocarbons by shape-selective, acid-catalyzed processes at fairly low temperatures. Experimentally, aqueous solutions of glucose (12 wt %) were reacted with HY-zeolite powder in a well-mixed batch reactor at temperatures ranging from 110 to 160 C and catalyst concentrations ranging from 2 to 20 g/150 ml. Unreacted glucose and oxygenated hydrocarbon products were measured by HPLC as a function of reaction time (0-24 h) and process conditions. Glucose conversions of 100% were obtained at 160 C after an 8-h reaction time. The apparent activation energy based on glucose conversion was 23.25 [plus minus] 0.40 kcal/mol. Several acid-catalyzed reactions were identified, including isomerization of glucose to fructose, partial dehydration of glucose to 5-(hydroxymethyl)furfural (HMF), rehydration and cleavage of HMF to formic acid and 4-oxo-pentanoic acid, and carbonization . Polymers of HMF and seven minor additional products in the lower molecular weight organic acids/aldehydes/ketones elution range were also isolated by HPLC. High yields of organic acids relative to HMF and lowered selectivity of HMF in the bulk phase relative to the homogeneous acid-catalyzed reaction suggests the possibility of molecular sieving reactions within the Y-zeolite in addition to reactions on the outer surface of the Y-zeolite particle.

Lourvanij, K.; Rorrer, G.L. (Oregon State Univ., Corvallis (United States))

1993-01-01

40

Sulfamic acid: an efficient, cost-effective and recyclable solid acid catalyst for the Friedlander quinoline synthesis  

Microsoft Academic Search

o-Aminoaryl ketones undergo smooth condensation with ?-methylene ketones in the presence of sulfamic acid (NH2SO3H) (SA) under mild reaction conditions to afford the corresponding polysubstituted quinolines in excellent yields. The catalyst can be recovered by simple filtration and can be recycled in subsequent reactions. The method is simple, cost-effective and environmentally benign.

J. S. Yadav; P. Purushothama Rao; D. Sreenu; R. Srinivasa Rao; V. Naveen Kumar; K. Nagaiah; A. R. Prasad

2005-01-01

41

Solvent free synthesis of quinoxalines, dipyridophenazines and chalcones under microwave irradiation with sulfated Degussa titania as a novel solid acid catalyst  

Microsoft Academic Search

Sulfated TiO2–P25 (Degussa titania) has been prepared by sol–gel method using H2SO4 and characterized by FT-IR, XRD, FE-SEM, EDS, HR-TEM, XPS, DRS and BET surface area measurements. Sulfate loading by H2SO4 increases the Lewis acidity of Degussa tiatania. This catalyst gives an excellent yield with less reaction time and is an inexpensive and easily recyclable solid acid catalyst for the

B. Krishnakumar; M. Swaminathan

42

Vapor phase nitration of benzene over solid acid catalysts IV. Nitration with nitric acid (3); supported sulfuric acid catalyst with co-feeding of a trace amount of sulfuric acid  

Microsoft Academic Search

In the vapor phase nitration of benzene with diluted nitric acid, we have succeeded in keeping a high nitration activity of the supported sulfuric acid catalyst for more than 2 months by co-feeding a trace amount of sulfuric acid (H2SO4\\/HNO3=1\\/5000 (wt. ratio)). The results after 60 days on-stream over 10wt.%–H2SO4\\/SiO2 catalyst are as follows: yield of nitrobenzene (NB), 93% based

H Sato; K Nagai; H Yoshioka; Y Nagaoka

1999-01-01

43

Polypyrrole based strong acid catalyst for acetalization  

NASA Astrophysics Data System (ADS)

Novel polypyrrole based acid catalyst has been synthesized through the neutralization reaction of polypyrrole and sulfuric acid. The polypyrrole based acid owned the acidity as high as 6.0 mmol/g, which was much higher than that of the traditional solid acids such as Nafion and Amberlyst-15 (0.8 mmol/g). The catalytic activities of the novel solid acid were investigated through the acetalization. The results showed that the novel solid acid held high activities for the reactions. Furthermore, the recycled activities of the catalyst indicated that the solid acid owned high stability during the catalytic process and little acid sites dropped from polypyrrole. The high acidity and stability made the novel polypyrrole based acid hold great potential for the green chemical processes.

Liang, Xuezheng; Cheng, Yuxiao; Qi, Chenze

2011-09-01

44

UBC Social Ecological Economic Development Studies (SEEDS) Student Report Investigation of Solid Acid Catalyst Functionalization for the Production of Biodiesel  

E-print Network

, waste vegetable oils can be used as a feedstock for biodiesel production. However, waste vegetable oils on the development of the acid density of the catalyst; and analyze the effect of functionalization steps phase contact (BC-A-VS), or ozonating the biochar (BC-A-O). These procedures increase the acid density

45

SYNTHESIS AND CHARACTERIZATION OF A NOVEL SOLID ACID CATALYST FOR IMPROVED USE OF WASTE OIL FEEDSTOCK FOR BIODIESEL PRODUCTION  

EPA Science Inventory

Carbon Catalyst Synthesis - Sucrose was treated directly with excess sulfuric acid sulfuric acid (9:1 mol/mol, 25°C). A carbon foam (nearly 20 fold increase in bulk volume) was immediately formed. The foam was then washed until no sulfate was dete...

46

Transesterification of soybean oil over WO3 supported on AlPO4 as a solid acid catalyst.  

PubMed

WO(3)/AlPO(4) catalysts were prepared by impregnation of AlPO(4) with ammonium metatungstate. Powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, and thermo gravimetric and differential thermal analysis (TG-DTA) demonstrated that the tungsten compound was incorporated into AlPO(4) forming the catalyst with an enhanced acidity. When transesterification of soybean oil over the catalysts was performed, the catalyst with 30 wt.% WO(3) loading and calcined at 1073 K, exhibited the best catalytic activity with a conversion of 72.5%. The transesterification was optimal at 453 K for 5h with a methanol/oil ratio of 30:1 and catalyst dosage of 5 wt.%. Free fatty acid (FFA) and water did not affect the catalytic activity. The catalyst proved to be stable over four transesterification cycles as it lost only 4% of its activity after being reused four times. The catalyst could be used for the transesterification of low-cost oils for biodiesel production. PMID:22728183

Xie, Wenlei; Yang, Dong

2012-09-01

47

Elucidation of the catalytic cracking pathway for unsaturated mono-, di-, and triacylglycerides on solid acid catalysts  

Microsoft Academic Search

Heterogeneous catalytic transformation of lipids to transportation fuels offers a unique opportunity to provide sustainable energy while utilizing the current petroleum refining infrastructure. The reaction chemistry for the heterogeneous catalytic cracking of unsaturated acylglycerides was studied. Mono-, di-, and triolein, which are acylglycerides with oleic acid as the fatty acid constituent, were reacted at 400°C over H+ZSM-5, faujasite, and silica–alumina

Tracy J. Benson; Rafael Hernandez; W. Todd French; Earl G. Alley; William E. Holmes

2009-01-01

48

Supercritical/Solid Catalyst (SSC)  

ScienceCinema

INL's patented, continuous-flow Supercritical/Solid Catalyst (SSC) produces the highest ASTM-quality B-100 biodiesel from waste fats, oils, and greases at the site of waste generation. SSC delivers low-cost transportation fuel, avoids significant landfill costs for municipalities, and reduces potent methane and other emissions produced in landfills from these wastes. You can learn more about INL's energy research programs at http://www.facebook.com/idahonationallaboratory.

None

2013-05-28

49

Zirconium(IV) tungstate nanoparticles prepared through chemical co-precipitation method and its function as solid acid catalyst  

NASA Astrophysics Data System (ADS)

In this paper, we report the synthesis of zirconium(IV) tungstate nanoparticles, a new and efficient catalyst for the oxidation of benzyl alcohol and esterification of acetic acid with various alcohols. The nanoparticle catalyst was prepared using the room temperature chemical co-precipitation method. The catalyst was characterized with thermogravimetric and differential thermal analysis, elemental analysis, X-ray diffraction analysis (XRD), fourier transform infrared spectroscopy (FT-IR), high-resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM) and the Brunauer-Emmett-Teller (BET) surface area. The crystallite size was found to be ~20 nm as revealed by XRD, HRTEM and AFM. The Na+ exchange capacity was found to be 2.76 meq g-1 and the surface area of the compound measured using BET method was found to be 250-265 m2 g-1. The high value of ion exchange capacity indicates the presence of surface hydroxyl groups. The prepared nanoparticles have proven to be excellent catalysts for both oxidation and ester synthesis under mild reaction conditions. The mechanism of the catalytic reaction was studied as well.

Sadanandan, Manoj; Bhaskaran, Beena

2014-08-01

50

Sulfamic acid: An efficient and cost-effective solid acid catalyst for the synthesis of ?-aminophosphonates at ambient temperature  

Microsoft Academic Search

Sulfamic acid catalyzed solvent-free protocol has been developed for the synthesis of ?-aminophosphonates by three component condensation between aldehydes, amines and diethyl phosphite at ambient temperature.

S. D. Mitragotri; D. M. Pore; U. V. Desai; P. P. Wadgaonkar

2008-01-01

51

An efficient solid acid catalyst: Poly p-styrenesulfonic acid supported on SBA15 via surface-initiated ATRP  

Microsoft Academic Search

The sulfonic acid-functionalized mesoporous organic–inorganic hybrid materials were synthesized via atom transfer radical polymerization (ATRP) method. SBA-15 material was first grafted with 4-(chloromethyl)phenyltrimethoxysilane. The surface-initiated polymerization of sodium p-styrenesulfonate inside the pore wall of functionalized SBA-15 results in p-styrenesulfonic acid functionalized SBA-15 (PSS-SBA-15). The results of FT-IR, nitrogen sorption isotherm, XRD, TEM and thermal gravimetric analyses (TGA) confirm that the

Congming Li; Jie Yang; Peiyuan Wang; Jian Liu; Qihua Yang

2009-01-01

52

Esterification of bio-oil from mallee (Eucalyptus loxophleba ssp. gratiae) leaves with a solid acid catalyst: Conversion of the cyclic ether and terpenoids into hydrocarbons.  

PubMed

Bio-oil from pyrolysis of mallee (Eucalyptus loxophleba ssp. gratiae) leaves differs from that obtained with wood by its content of cyclic ethers, terpenoids and N-containing organic compounds. Upgrading of the leaf bio-oil in methanol with a solid acid catalyst was investigated and it was found that the N-containing organics in the bio-oil lead to deactivation of the catalyst in the initial stage of exposure and have to be removed via employing high catalyst loading to allow the occurrence of other acid-catalysed reactions. Eucalyptol, the main cyclic ether in the bio-oil, could be converted into the aromatic hydrocarbon, p-cymene, through a series of intermediates including ?-terpineol, terpinolene, and ?-terpinene. Various steps such as ring-opening, dehydration, isomerisation, and aromatization were involved in the conversion of eucalyptol. The terpenoids in bio-oil could also be converted into aromatic hydrocarbons that can serve as starting materials for the synthesis of fine chemicals, via the similar processes. PMID:22940326

Hu, Xun; Gunawan, Richard; Mourant, Daniel; Wang, Yi; Lievens, Caroline; Chaiwat, Weerawut; Wu, Liping; Li, Chun-Zhu

2012-11-01

53

Sulfamic Acid: An Efficient, Cost-Effective, and Reusable Solid Acid Catalyst for the Synthesis of 1,8-Naphthyridines Under Solvent-Free Heating and Microwave Irradiation  

Microsoft Academic Search

An efficient and convenient method is described for the synthesis of 1,8-naphthyridines in excellent yields by condensation of 2-aminonicotinaldehyde with various active methylene compounds in the presence of sulfamic acid as the catalyst in a solvent-free media using both conventional heating and microwave irradiation.

Y. Thirupathi Reddy; P. Raghotham Reddy; M. Nikhil Reddy; B. Rajitha; Peter A. Crooks

2008-01-01

54

Surfactants from biomass: a two-step cascade reaction for the synthesis of sorbitol fatty acid esters using solid acid catalysts.  

PubMed

Sorbitol fatty esters have been prepared through a two-step catalytic process which involves the protection of the polyalcohol by ketalization followed by esterification with the fatty acid. Inorganic molecular sieves with different pore topologies as well as heteropolyacids (HPA) were used as acid catalysts to perform both the ketalization and the esterification step. These catalysts are found to hydrolyze the ketal function and promote the esterification between the free hydroxy groups and oleic acid in a cascade process. The results show a positive shape-selectivity effect when the process is carried out using tridirectional, and especially monodirectional (mordenite), zeolites, such that the ratio of mono- to higher esters and the hydroxy number of the final product are increased as compared to those obtained for the homogeneous-catalyzed process. PMID:18605669

Corma, Avelino; Hamid, Sharifah B A; Iborra, Sara; Velty, Alexandra

2008-01-01

55

TiO 2–SO 4 2? as a novel solid acid catalyst for highly efficient, solvent free and easy synthesis of chalcones under microwave irradiation  

Microsoft Academic Search

TiO2–SO42? has been prepared by the sol–gel method using H2SO4 and used for the synthesis of chalcones under microwave irradiation. Sulfate loading by H2SO4 increases the Lewis acidity of TiO2. This catalyst gives an excellent yield with less reaction time and is an inexpensive, easily recyclable catalyst for this reaction.

B. Krishnakumar; R. Velmurugan; M. Swaminathan

2011-01-01

56

Isobutane\\/butene alkylation on solid catalysts. Where do we stand?  

Microsoft Academic Search

Liquid-phase processes with concentrated sulfuric acid or hydrogen fluoride as catalysts are currently being used in petroleum refining for the manufacture of alkylation gasoline from isobutane and butenes. While the product, i.e., alkylate, is a most valuable gasoline component, the existing processes for its manufacture are less satisfactory. Replacement of the liquid catalysts by a solid acid is an important

J. Weitkamp; Y. Traa

1999-01-01

57

Immobilized cell reactors in mineralization of dicarboxylic acid solid waste  

Microsoft Academic Search

Dicarboxylic acid solid waste containing phthalic acid, malic acid, quinone, saturated and unsaturated dicarboxylic esters etc., are discharged in huge quantities during the crackdown of benzene over the catalyst vanadium at temperatures greater than 500 C in a dicarboxylic acid manufacturing industry. Concern over the biological effects of these compounds underlines the necessity to treat this solid waste. The role of

Ganesh Kumar Arumugam; Swarnalatha Somasundaram; Victor Babu Kassey; Sekaran Ganesan

2006-01-01

58

Acid monolayer functionalized iron oxide nanoparticle catalysts  

NASA Astrophysics Data System (ADS)

Superparamagnetic iron oxide nanoparticle functionalization is an area of intensely active research, with applications across disciplines such as biomedical science and heterogeneous catalysis. This work demonstrates the functionalization of iron oxide nanoparticles with a quasi-monolayer of 11-sulfoundecanoic acid, 10-phosphono-1-decanesulfonic acid, and 11-aminoundecanoic acid. The carboxylic and phosphonic moieties form bonds to the iron oxide particle core, while the sulfonic acid groups face outward where they are available for catalysis. The particles were characterized by thermogravimetric analysis (TGA), transmission electron microscopy (TEM), potentiometric titration, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray photoelectron spectrometry (XPS), and dynamic light scattering (DLS). The sulfonic acid functionalized particles were used to catalyze the hydrolysis of sucrose at 80° and starch at 130°, showing a higher activity per acid site than the traditional solid acid catalyst Amberlyst-15, and comparing well against results reported in the literature for sulfonic acid functionalized mesoporous silicas. In sucrose catalysis reactions, the phosphonic-sulfonic nanoparticles (PSNPs) were seen to be incompletely recovered by an external magnetic field, while the carboxylic-sulfonic nanoparticles (CSNPs) showed a trend of increasing activity over the first four recycle runs. Between the two sulfonic ligands, the phosphonates produced a more tightly packed monolayer, which corresponded to a higher sulfonic acid loading, lower agglomeration, lower recoverability through application of an external magnetic field, and higher activity per acid site for the hydrolysis of starch. Functionalizations with 11-aminoundecanoic acid resulted in some amine groups binding to the surfaces of iron oxide nanoparticles. This amine binding is commonly ignored in iron oxide nanoparticle syntheses and functionalizations for biomedical and catalytic applications, affecting understandings of surface charge and other material properties.

Ikenberry, Myles

59

Biodiesel Production by Ethanolysis of Various Vegetable oils Using Calcium Ethoxide as Solid Base Catalyst  

Microsoft Academic Search

In this study, fatty acid ethyl esters (FAEE) were produced from 4 different vegetable oils (sunflower, cotton seed, olive oil and used frying oil) using calcium ethoxide as a heterogeneous solid base catalyst. The ester preparation involved a two-step transesterification reaction, followed by purification. The effects of the mass ratio of catalyst to oil, the molar ratio of ethanol to

G. Anastopoulos; G. S. Dodos; S. Kalligeros; F. Zannikos

2012-01-01

60

Calcium-based Lewis acid catalysts.  

PubMed

Recently, Lewis acidic calcium salts bearing weakly coordinating anions such as Ca(NTf?)?, Ca(OTf)?, CaF? and Ca[OCH(CF?)?]? have been discovered as catalysts for the transformation of alcohols, olefins and carbonyl compounds. High stability towards air and moisture, selectivity and high reactivity under mild reaction conditions render these catalysts a sustainable and mild alternative to transition metals, rare-earth metals or strong Brønsted acids. PMID:23712417

Begouin, Jeanne-Marie; Niggemann, Meike

2013-06-17

61

Sulfamic Acid as a Novel, Efficient, Cost?Effective, and Reusable Solid Acid Catalyst for the Synthesis of Pyrroles under Solvent?Free Conditions  

Microsoft Academic Search

Paal–Knorr condensation of 2,5?hexadione with primary amines in the presence of a catalytic amount of sulfamic acid under solvent?free conditions has been accomplished with an excellent yield. This is a very easy, rapid, and high?yielding reaction for the synthesis N?substituted pyrrole derivatives.

Surya K. De

2008-01-01

62

Inorganic solid acids and their use in acid-catalyzed hydrocarbon reactions  

Microsoft Academic Search

It is possible to say that solid acid catalysis involves the largest amounts of catalysts used and the largest economical effort in the oil refining and chemical industry. In this review the author has tried to describe perhaps the most important solid acids based on inorganic oxides, going from their preparation procedures and characterization, to their catalytic activity for a

A. Corma

1995-01-01

63

Novel Solid Base Catalysts for the Production of Biodiesel from Lipids  

E-print Network

The primary commercial biodiesel production processes use homogeneous base catalysts which cause separation and wastewater discharge problems. Solid base catalysts can overcome these drawbacks. However, a solid base catalyst ...

Zhao, Lina

2010-12-17

64

Method For Reactivating Solid Catalysts Used For Alklation Reactions  

DOEpatents

A method for reactivating a solid alkylation catalyst is provided which can be performed within a reactor that contains the alkylation catalyst or outside the reactor. Effective catalyst reactivation is achieved whether the catalyst is completely deactivated or partially deactivated. A fluid reactivating agent is employed to dissolve catalyst fouling agents and also to react with such agents and carry away the reaction products. The deactivated catalyst is contacted with the fluid reactivating agent under pressure and temperature conditions such that the fluid reactivating agent is dense enough to effectively dissolve the fouling agents and any reaction products of the fouling agents and the reactivating agent. Useful pressures and temperatures for reactivation include near-critical, critical, and supercritical pressures and temperatures for the reactivating agent. The fluid reactivating agent can include, for example, a branched paraffin containing at least one tertiary carbon atom, or a compound that can be isomerized to a molecule containing at least one tertiary carbon atom.

Ginosar, Daniel M. (Idaho Falls, ID); Thompson, David N. (Idaho Falls, ID); Coates, Kyle (Shelley, ID); Zalewski, David J. (Proctorville, OH); Fox, Robert V. (Idaho Falls, ID)

2005-05-03

65

Calcined Mg–Al hydrotalcites as solid base catalysts for methanolysis of soybean oil  

Microsoft Academic Search

Methyl ester of fatty acids, derived from vegetable oils or animal fats and known as biodiesel, is a promising alternative diesel fuel regarding the limited resources of fossil fuel and the environmental concerns. In this work, an environmentally benign process for the methanolysis of soybean oil to methyl esters using calcined Mg–Al hydrotalcites as solid base catalysts in a heterogeneous

Wenlei Xie; Hong Peng; Ligong Chen

2006-01-01

66

Molybdenum Dioxide As A Solid Oxide Fuel Cell Anodic Catalyst  

E-print Network

able to produce stable anodes for a sustainable amount of time at the fuel cell operating temperatureMolybdenum Dioxide As A Solid Oxide Fuel Cell Anodic Catalyst Jay Thunstrom, Su Ha, Oscar Flores are being developed. One of the most auspicious and the topic presented here is the solid oxide fuel cell

Collins, Gary S.

67

Application of solid ash based catalysts in heterogeneous catalysis  

SciTech Connect

Solid wastes, fly ash, and bottom ash are generated from coal and biomass combustion. Fly ash is mainly composed of various metal oxides and possesses higher thermal stability. Utilization of fly ash for other industrial applications provides a cost-effective and environmentally friendly way of recycling this solid waste, significantly reducing its environmental effects. On the one hand, due to the higher stability of its major component, aluminosilicates, fly ash could be employed as catalyst support by impregnation of other active components for various reactions. On the other hand, other chemical compounds in fly ash such as Fe{sub 2}O{sub 3} could also provide an active component making fly ash a catalyst for some reactions. In this paper, physicochemical properties of fly ash and its applications for heterogeneous catalysis as a catalyst support or catalyst in a variety of catalytic reactions were reviewed. Fly-ash-supported catalysts have shown good catalytic activities for H{sub 2} production, deSOx, deNOx, hydrocarbon oxidation, and hydrocracking, which are comparable to commercially used catalysts. As a catalyst itself, fly ash can also be effective for gas-phase oxidation of volatile organic compounds, aqueous-phase oxidation of organics, solid plastic pyrolysis, and solvent-free organic synthesis. 107 refs., 4 figs., 2 tabs.

Shaobin Wang [Curtin University of Technology, Perth, WA (Australia). Department of Chemical Engineering

2008-10-01

68

Application of solid ash based catalysts in heterogeneous catalysis.  

PubMed

Solid wastes, fly ash, and bottom ash are generated from coal and biomass combustion. Fly ash is mainly composed of various metal oxides and possesses higher thermal stability. Utilization of fly ash for other industrial applications provides a cost-effective and environmentally friendly way of recycling this solid waste, significantly reducing its environmental effects. On the one hand, due to the higher stability of its major component, aluminosilicates, fly ash could be employed as catalyst support by impregnation of other active components for various reactions. On the other hand, other chemical compounds in fly ash such as Fe2O3 could also provide an active component making fly ash a catalyst for some reactions. In this paper, physicochemical properties of fly ash and its applications for heterogeneous catalysis as a catalyst support or catalyst in a variety of catalytic reactions were reviewed. Fly-ash-supported catalysts have shown good catalytic activities for H2 production, deSO(x), deNO(x), hydrocarbon oxidation,and hydrocracking, which are comparable to commercially used catalysts. As a catalyst itself, fly ash can also be effective for gas-phase oxidation of volatile organic compounds, aqueous-phase oxidation of organics, solid plastic pyrolysis, and solvent-free organic synthesis. PMID:18939526

Wang, Shaobin

2008-10-01

69

Synthesis of chalcones catalyzed by a novel solid sulfonic acid from bamboo  

Microsoft Academic Search

A novel solid acid catalyst, bamboo char sulfonic acid, has been prepared and applied in the synthesis of chalcones at high yields in a heterogenous acid system under solvent-free condition. The experimental results have shown that this catalyst could be easily recycled and with no significant loss of catalytic efficiency for the subsequent reactions.

Qiong Xu; Zhigao Yang; Dulin Yin; Feng Zhang

2008-01-01

70

Dehydration of glycerol over niobia-supported silicotungstic acid catalysts.  

PubMed

Liquid-phase dehydration of glycerol to acrolein over nanosized niobia-supported silicotungstic acid catalysts was performed to investigate the effect of the silicotungstic acid loading on the catalytic performance of the catalysts. The catalysts were prepared by following an impregnation method with different HSiW loadings in the range of 10-50 wt%. The prepared catalysts were characterized by N2 physisorption, XRD, FT-IR, TPD of ammonia, and TGA. Dehydration of glycerol was conducted in an autoclave reactor under the conditions of controlled reaction temperatures under corresponding pressure. Increasing HSiW loading rapidly increased the acidity of HSiW/Nb205 catalyst and rate of glycerol conversion, but acrolein selectivity decreased due to enhanced deactivation of the catalyst by carbon deposit. Consequently, it was confirmed that catalytic activity for the dehydration of glycerol to acrolein was dependant on the acidity of catalyst and can be controlled by HSiW loading. PMID:23646735

Lee, Young Yi; Ok, Hye Jeong; Moon, Dong Ju; Kim, Jong Ho; Park, Nam Cook; Kim, Young Chul

2013-01-01

71

Acidic ionic liquid as "quasi-homogeneous" catalyst for controllable synthesis of cellulose acetate.  

PubMed

In this paper, we demonstrated that acidic ionic liquids (ILs) can be used as "quasi-homogeneous" catalysts for the efficient acetylation of cellulose. Unlike existing techniques that use large amount of ILs as solvent to dissolve and acetylate cellulose, a small amount of acidic ILs was used as catalyst in this study to overcome the low efficiency associated with relatively high viscosity and costs of ILs during homogeneous acetylation. Fully substituted cellulose acetate with a conversion of 88.8% was obtained by using only 9mol% IL 1-vinyl-3-(3-sulfopropyl) imidazolium hydrogen sulfate as catalyst, which is much higher than that of common commercialized solid acid catalysts. The degree of substitution and solubility of the obtained cellulose acetate can be facilely controlled by varying the concentration of ILs and reaction time. The dual function of swelling and catalyzing of acidic ILs for the acetylation of cellulose is responsible for the excellent catalytic performance. PMID:25256462

Tian, Dong; Han, Yangyang; Lu, Canhui; Zhang, Xinxing; Yuan, Guiping

2014-11-26

72

Solid acids for green chemistry.  

PubMed

Solid acids and especially those based on micelle-templated silicas and other mesoporous high surface area support materials are beginning to play a significant role in the greening of fine and specialty chemicals manufacturing processes. A wide range of important organic reactions can be efficiently catalyzed by these materials, which can be designed to provide different types of acidity as well as high degrees of reaction selectivity. The solid acids generally have high turnover numbers and can be easily separated from the organic components. The combination of this chemistry with innovative reaction engineering offers exciting opportunities for innovative green chemical manufacturing in the future. PMID:12234209

Clark, James H

2002-09-01

73

Alumino-rhenium-sulphide catalysts in hydrogenation of carboxylic acids  

SciTech Connect

Alumino-rhenium sulfide catalysts containing 1.5, 5 and 8% rhenium are active in hydrogenation of mono-, dicarboxylic acids (isobutyric, valeric, pelargonic and succinic) and a fraction of synthetic fatty acids to corresponding alcohols at 210 to 270/sup 0/C and a partial pressure of hydrogen of 25 MPa. These catalysts appear to be more selective and are more stable than other well-known oxide catalysts. 2 tables.

Ryashentseva, M.A.; Minachev, Kh.M.; Yunusov, M.P.; Serodzhev, A.T.

1982-01-01

74

Solid acid (superacid) catalyzed regioselective adamantylation of substituted benzenes  

Microsoft Academic Search

Adamantylation of substituted benzenes with 1-bromo-adamantane was catalyzed by solid acids including acidic ion exchange and ionomer resins, HY zeolite, sulfated zirconia and supported superacids on HY zeolite and SiO2. Adamantylation generally takes place in excellent yield giving predominantly para products without formation of byproducts. The reactions did not require the usual workup of Friedel-Crafts reactions as catalysts were simply

George A. Olah; Béla Török; Tatyana Shamma; Marianna Török; G. K. Surya Prakash

1996-01-01

75

A microstructural investigation of model solid state hydrodesulfurization catalysts  

NASA Astrophysics Data System (ADS)

Model molybdenum disulfide-based solid state synthesis catalysts have been prepared and tested catalytically in the HDS of thiophene. Both promoted and sulfur-deficient samples were prepared and the kinetic analyses were done at temperatures ranging from 473-673 K and atmospheric pressure. Structural characterization was carried out using X-ray diffraction and analytical and high resolution electron microscopy. The results indicate that the active catalysts possess a high degree of disorder in the (10 overline10), (10 overline11), (10 overline12) directions, which represent the edges of the MoS 2 crystal. This work also establishes that both Group VIII promotion and sulfur deficiency lead to similar structural changes in the molybdenum sulfide lattice of this specific solid state system. These structural traits can be correlated with increased HDS activity.

Sachdev, Amit; Lindner, James; Schwank, Johannes; Garcia, Maria A. Villa

1990-08-01

76

Production of Jatropha biodiesel fuel over sulfonic acid-based solid acids.  

PubMed

Sulfonic acid-functionalized platelet SBA-15 mesoporous silica with an acid capacity of 2.44mmol H(+) g-cat(-1) (shortly termed 15SA-SBA-15-p) was one-pot synthesized by co-condensation method. When applied as solid acid catalyst in synthesis of Jatropha biodiesel fuel (BDF), the 15SA-SBA-15-p catalyst showed higher activity and resistances to water and free fatty acid (FFA) than commercial sulfonic resins of Amberlyst-15 and SAC-13. For the continuous Jatropha BDF production, a steady 75-78wt% of fatty acid methyl ester (FAME) content was obtained over 15SA-SBA-15-p catalyst at 150°C for 75h, whereas the Amberlyst-15 and SAC-13 catalysts were quickly deactivated due to the decomposition of thermally unstable framework and serious leaching of sulfonic acids. More importantly, the quality, stability and cold flow characteristic of Jatropha BDF synthesized by 15SA-SBA-15-p catalyst were better than those synthesized by Amberlyst-15 and SAC-13 catalysts, making the blending with petro-diesel an easy task. PMID:24548779

Chen, Shih-Yuan; Lao-Ubol, Supranee; Mochizuki, Takehisa; Abe, Yohko; Toba, Makoto; Yoshimura, Yuji

2014-04-01

77

A microstructural investigation of model solid state hydrodesulfurization catalysts  

Microsoft Academic Search

Model molybdenum disulfide-based solid state synthesis catalysts have been prepared and tested catalytically in the HDS of thiophene. Both promoted and sulfur-deficient samples were prepared and the kinetic analyses were done at temperatures ranging from 473-673 K and atmospheric pressure. Structural characterization was carried out using X-ray diffraction and analytical and high resolution electron microscopy. The results indicate that the

Amit Sachdev; James Lindner; Johannes Schwank; Maria A. Villa Garcia

1990-01-01

78

EPA'S CATALYST RESEARCH PROGRAM: ENVIRONMENTAL IMPACT OF SULFURIC ACID EMISSIONS  

EPA Science Inventory

A sulfuric acid review conference sponsored by EPA's automotive Catalyst Research Program was held recently at Hendersonville, NC, for researchers whose work is funded by EPA. Emissions characterization research indicated that in-use catalyst-equipped vehicles emit low levels of ...

79

Low acid producing solid propellants  

NASA Technical Reports Server (NTRS)

The potential environmental effects of the exhaust products of conventional rocket propellants have been assessed by various groups. Areas of concern have included stratospheric ozone, acid rain, toxicity, air quality and global warming. Some of the studies which have been performed on this subject have concluded that while the impacts of rocket use are extremely small, there are propellant development options which have the potential to reduce those impacts even further. This paper discusses the various solid propellant options which have been proposed as being more environmentally benign than current systems by reducing HCI emissions. These options include acid neutralized, acid scavenged, and nonchlorine propellants. An assessment of the acid reducing potential and the viability of each of these options is made, based on current information. Such an assessment is needed in order to judge whether the potential improvements justify the expenditures of developing the new propellant systems.

Bennett, Robert R.

1995-01-01

80

Cyclobutane amino acids and peptidomimetics, parallel catalyst screening for aziridination  

E-print Network

This thesis describes two projects: (i) syntheses and conformational studies of cyclobutane amino acids and peptidomimetics; and, (ii) parallel screening of catalysts for asymmetric aziridination. Syntheses and conformational studies of nonnatural...

Li, Shih-ming

2012-06-07

81

A novel Brønsted acid catalyst for Friedel–Crafts acylation  

Microsoft Academic Search

Bis(trifluoroalkylsulfonylimino)trifluoromethanesulfonic acid has demonstrated remarkable catalytic ability in the electrophilic acylation of aromatic substrates. Various perfluoroalkyl substituted aroyl chlorides are employed in Friedel–Crafts acylation typically using 1mol% of catalyst.

Anna G. Posternak; Romute Yu. Garlyauskayte; Lev M. Yagupolskii

2009-01-01

82

Method for producing iron-based acid catalysts  

SciTech Connect

A method for preparing an acid catalyst with a long shelf-life is described. Crystalline iron oxides are doped with lattice compatible metals which are heated with halogen compounds at elevated temperatures.

Farcasiu, M.; Kathrein, H.; Kaufman, P.B.; Diehl, J.R.

1998-04-01

83

Facile synthesis of highly efficient and recyclable magnetic solid acid from biomass waste.  

PubMed

In this work, sawdust, a biomass waste, is converted into a magnetic porous carbonaceous (MPC) solid acid catalyst by an integrated fast pyrolysis-sulfonation process. The resultant magnetic solid acid has a porous structure with high surface area of 296.4 m(2) g(-1), which can be attributed to the catalytic effect of Fe. The catalytic activity and recyclability of the solid acid catalyst are evaluated during three typical acid-catalyzed reactions: esterification, dehydration, and hydrolysis. The favorable catalytic performance in all three reactions is attributed to the acid's high strength with 2.57 mmol g(-1) of total acid sites. Moreover, the solid acid can be reused five times without a noticeable decrease in catalytic activity, indicating the stability of the porous carbon (PC)-sulfonic acid group structure. The findings in the present work offer effective alternatives for environmentally friendly utilization of abundant biomass waste. PMID:23939253

Liu, Wu-Jun; Tian, Ke; Jiang, Hong; Yu, Han-Qing

2013-01-01

84

Intermediates to ethylene glycol: carbonylation of formaldehyde catalyzed by Nafion solid perfluorosulfonic acid resin  

SciTech Connect

Details of a series of reactions for the production of ethylene glycol using a catalyst of Nafion solid perfluorosulfonic acid resin was detailed. The reactions included the carbonylation of formaldehyde and esterification and then hydrogenation of the product of the carbonylation, glycolic acid. Other preparations included in the work included methyl glycolate, acetylglycolic acid, methyl acetylglycolate, and methyl methoxyacetate.

Hendriksen, D.E.

1983-01-01

85

Staining of fluid-catalytic-cracking catalysts: localising Brønsted acidity within a single catalyst particle.  

PubMed

A time-resolved in situ micro-spectroscopic approach has been used to investigate the Brønsted acidic properties of fluid-catalytic-cracking (FCC) catalysts at the single particle level by applying the acid-catalysed styrene oligomerisation probe reaction. The reactivity of individual FCC components (zeolite, clay, alumina and silica) was monitored by UV/Vis micro-spectroscopy and showed that only clay and zeolites (Y and ZSM-5) contain Brønsted acid sites that are strong enough to catalyse the conversion of 4-fluorostyrene into carbocationic species. By applying the same approach to complete FCC catalyst particles, it has been found that the fingerprint of the zeolitic UV/Vis spectra is clearly recognisable. This almost exclusive zeolitic activity is confirmed by the fact that hardly any reactivity is observed for FCC particles that contain no zeolite. Confocal fluorescence microscopy images of FCC catalyst particles reveal inhomogeneously distributed micron-sized zeolite domains with a highly fluorescent signal upon reaction. By examining laboratory deactivated FCC catalyst particles in a statistical approach, a clear trend of decreasing fluorescence intensity, and thus Brønsted acidity, of the zeolite domains is observed with increasing severity of the deactivation method. By comparing the average fluorescence intensities obtained with two styrenes that differ in reactivity, it has been found that the Brønsted acid site strength within FCC catalyst particles containing ZSM-5 is more uniform than within those containing zeolite Y, as confirmed with temperature-programmed desorption of ammonia. PMID:22161809

Buurmans, Inge L C; Ruiz-Martínez, Javier; van Leeuwen, Sanne L; van der Beek, David; Bergwerff, Jaap A; Knowles, William V; Vogt, Eelco T C; Weckhuysen, Bert M

2012-01-23

86

Preparation of a novel carbon-based solid acid from cassava stillage residue and its use for the esterification of free fatty acids in waste cooking oil.  

PubMed

A novel carbon-based solid acid catalyst was prepared by the sulfonation of incompletely carbonized cassava stillage residue (CSR) with concentrated sulfuric acid, and employed to catalyze the esterification of methanol and free fatty acids (FFAs) in waste cooking oil (WCO). The effects of the carbonization and the sulfonation temperatures on the pore structure, acid density and catalytic activity of the CSR-derived catalysts were systematically investigated. Low temperature carbonization and high temperature sulfonation can cause the collapse of the carbon framework, while high temperature carbonization is not conducive to the attachment of SO3H groups on the surface. The catalyst showed high catalytic activity for esterification, and the acid value for WCO is reduced to below 2mg KOH/g after reaction. The activity of catalyst can be well maintained after five cycles. CSR can be considered a promising raw material for the production of a new eco-friendly solid acid catalyst. PMID:24661813

Wang, Lingtao; Dong, Xiuqin; Jiang, Haoxi; Li, Guiming; Zhang, Minhua

2014-04-01

87

KI-impregnated oyster shell as a solid catalyst for soybean oil transesterification  

Microsoft Academic Search

Research on inexpensive and green catalysts is needed for economical production of biodiesel. The goal of the research was to test KI-impregnated calcined oyster shell as a solid catalyst for transesterification of soybean oil. Specific objectives were to characterize KI-impregnated oyster shell, determine the effect of reaction variables and reaction kinetics. The catalyst was synthesized by impregnating KI on calcined

Suguna Jairam; Praveen Kolar; Ratna Sharma-Shivappa; Jason A. Osborne; Jack P. Davis

88

Transesterification of crude palm kernel oil and crude coconut oil by different solid catalysts  

Microsoft Academic Search

This work reports on the preliminary results of using several acidic and basic solids, such as ZrO2, ZnO, SO42?\\/SnO2, SO42?\\/ZrO2, KNO3\\/KL zeolite and KNO3\\/ZrO2 as heterogeneous catalysts for crude palm kernel oil (PKO) and crude coconut oil (CCO) transesterification with methanol. It was found that ZnO and SO42?\\/ZrO2 exhibited the highest activity for both PKO and CCO transesterification. In the

Jaturong Jitputti; Boonyarach Kitiyanan; Pramoch Rangsunvigit; Kunchana Bunyakiat; Lalita Attanatho; Peesamai Jenvanitpanjakul

2006-01-01

89

Lewis acid-assisted formic acid dehydrogenation using a pincer-supported iron catalyst.  

PubMed

Formic acid (FA) is an attractive compound for H2 storage. Currently, the most active catalysts for FA dehydrogenation use precious metals. Here, we report a homogeneous iron catalyst that, when used with a Lewis acid (LA) co-catalyst, gives approximately 1,000,000 turnovers for FA dehydrogenation. To date, this is the highest turnover number reported for a first-row transition metal catalyst. Preliminary studies suggest that the LA assists in the decarboxylation of a key iron formate intermediate and can also be used to enhance the reverse process of CO2 hydrogenation. PMID:24999607

Bielinski, Elizabeth A; Lagaditis, Paraskevi O; Zhang, Yuanyuan; Mercado, Brandon Q; Würtele, Christian; Bernskoetter, Wesley H; Hazari, Nilay; Schneider, Sven

2014-07-23

90

Organometallic catalysts for primary phosphoric acid fuel cells  

NASA Technical Reports Server (NTRS)

A continuing effort by the U.S. Department of Energy to improve the competitiveness of the phosphoric acid fuel cell by improving cell performance and/or reducing cell cost is discussed. Cathode improvement, both in performance and cost, available through the use of a class of organometallic cathode catalysts, the tetraazaannulenes (TAAs), was investigated. A new mixed catalyst was identified which provides improved cathode performance without the need for the use of a noble metal. This mixed catalyst was tested under load for 1000 hr. in full cell at 160 to 200 C in phosphoric acid H3PO4, and was shown to provide stable performance. The mixed catalyst contains an organometallic to catalyze electroreduction of oxygen to hydrogen peroxide and a metal to catalyze further electroreduction of the hydrogen peroxide to water. Cathodes containing an exemplar mixed catalyst (e.g., Co bisphenyl TAA/Mn) operate at approximately 650 mV vs DHE in 160 C, 85% H3PO4 with oxygen as reactant. In developing this mixed catalyst, a broad spectrum of TAAs were prepared, tested in half-cell and in a rotating ring-disk electrode system. TAAs found to facilitate the production of hydrogen peroxide in electroreduction were shown to be preferred TAAs for use in the mixed catalyst. Manganese (Mn) was identified as a preferred metal because it is capable of catalyzing hydrogen peroxide electroreduction, is lower in cost and is of less strategic importance than platinum, the cathode catalyst normally used in the fuel cell.

Walsh, Fraser

1987-01-01

91

Elucidating the nature of the cobalt centres in CoAPO-18 acid catalysts  

SciTech Connect

A combined UV-Vis and FTIR spectroscopic approach, supplemented by the use of probe molecules (N{sub 2}, CO, C{sub 2}H{sub 4} and H{sub 2}O) as selective adsorbates, has clarified the atomic environment of cobalt centres in CoAPO-18 solid acid catalysts. These catalysts have both framework Co(II) ions in tetrahedral coordination and coordinatively-unsaturated Co(II) Lewis acid centres. But, only approximately half of the tetrahedral ions generate Bronsted OH groups (bridged between Co and P) and are oxidizable to framework Co(III). These bridged OHs, which are the active catalytic centres in acid-catalysis, are strongly influenced by the adsorbates in that the Co(H) ions of the [O{sub 3}CoO(H)] units undergo significant changes in the coordination sphere: the stronger is the ligand (adsorbate), the larger is the number of catalytic centres that are modified.

Marchese, L.; Martra, G.; Damilano, N.; Coluccia, S. [Universita di Torino (Italy); Thomas, J.M. [Royal Institution of Great Britain, London (United Kingdom)

1996-12-31

92

Green chemistry: biodiesel made with sugar catalyst.  

PubMed

The production of diesel from vegetable oil calls for an efficient solid catalyst to make the process fully ecologically friendly. Here we describe the preparation of such a catalyst from common, inexpensive sugars. This high-performance catalyst, which consists of stable sulphonated amorphous carbon, is recyclable and its activity markedly exceeds that of other solid acid catalysts tested for 'biodiesel' production. PMID:16281026

Toda, Masakazu; Takagaki, Atsushi; Okamura, Mai; Kondo, Junko N; Hayashi, Shigenobu; Domen, Kazunari; Hara, Michikazu

2005-11-10

93

Green chemistry: Biodiesel made with sugar catalyst  

NASA Astrophysics Data System (ADS)

The production of diesel from vegetable oil calls for an efficient solid catalyst to make the process fully ecologically friendly. Here we describe the preparation of such a catalyst from common, inexpensive sugars. This high-performance catalyst, which consists of stable sulphonated amorphous carbon, is recyclable and its activity markedly exceeds that of other solid acid catalysts tested for `biodiesel' production.

Toda, Masakazu; Takagaki, Atsushi; Okamura, Mai; Kondo, Junko N.; Hayashi, Shigenobu; Domen, Kazunari; Hara, Michikazu

2005-11-01

94

Solid-phase extraction of acidic herbicides.  

PubMed

A discussion of solid-phase extraction method development for acidic herbicides is presented that reviews sample matrix modification, extraction sorbent selection, derivatization procedures for gas chromatographic analysis, and clean-up procedures for high-performance liquid chromatographic analysis. Acidic herbicides are families of compounds that include derivatives of phenol (dinoseb, dinoterb and pentachlorophenol), benzoic acid (acifluorfen, chloramben, dicamba, 3,5-dichlorobenzoic acid and dacthal--a dibenzoic acid derivative), acetic acid [2,4-dichlorophenoxyacetic acid (2,4-D), 4-chloro-2-methylphenoxyacetic acid (MCPA) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T)], propanoic acid [dichlorprop, fluazifop, haloxyfop, 2-(4-chloro-2-methylphenoxy)propanoic acid (MCPP) and silvex], butanoic acid [4-(2,4-dichlorophenoxy)butanoic acid (2,4-DB) and 4-(4-chloro-2-methylphenoxy)butanoic acid (MCPB)], and other miscellaneous acids such as pyridinecarboxylic acid (picloram) and thiadiazine dioxide (bentazon). PMID:10941675

Wells, M J; Yu, L Z

2000-07-14

95

Electrowinning of Nickel from Spent Nickel Catalyst Leachate with Sulphoric Acid  

Microsoft Academic Search

Large amount of Nickel catalysts are used by different industries resulting in the production of large amount of solid waste containing nickel which is the spent or deactivated catalysts. These catalysts contain from 14-24% nickel based on the production company and the process. Nickel electro-winning from spent catalyst leachate solutions is studied to determine the best operative conditions such as

R. Ghanem; H. Farag; Y. Eltaweel; Mona E. Ossman

96

On the nature of the deactivation of supported palladium nanoparticle catalysts in the decarboxylation of fatty acids.  

SciTech Connect

Supported palladium catalysts are effective catalysts for the hydrogen-free decarboxylation of fatty acids. However, the catalysts deactivate severely after one use. Here, the recyclability of a well-defined, mesoporous silica-supported palladium nanoparticle catalyst is evaluated in the batch decarboxylation of stearic acid at 300 C under inert atmosphere, producing n-heptadecane. The nature of the catalyst deactivation is examined in detail via an array of characterization techniques. X-ray photoelectron spectroscopy (XPS) demonstrates that little palladium surface oxidation occurs over the course of the reaction, and a combination of X-ray absorption spectroscopy and transmission electron microscopy (TEM) suggests negligible particle sintering or agglomeration. Physisorption and chemisorption measurements demonstrate substantial loss in total surface area and porosity as well as accessible palladium surface area with these losses attributed to significant organic deposition on the catalyst, as verified via thermogravimetric analysis. High temperature calcination is applied to combust and remove these residues, but resultant nanoparticle agglomeration is significant. Solid state nuclear magnetic resonance spectroscopy (NMR), Fourier transform infrared spectroscopy (FT-IR) and solid dissolution followed by organic extraction methodologies demonstrate that the carbonaceous deposits are not coke but rather strongly adsorbed reactants and products. Detrimental coke formation, as suggested by prior literature, is verified to be absent, as extraction of the surface-deposited organic species yields nearly complete recovery of the total surface area, pore volume, and active palladium surface area. Furthermore, the regenerated catalyst exhibits a corresponding significant recovery of decarboxylation activity.

Ping, E. W.; Pierson, J.; Wallace, R.; Miller, J. T.; Fuller, T. F.; Jones, C. W. (Chemical Sciences and Engineering Division); (Georgia Institute of Technology)

2011-04-15

97

Thermal decomposition of lignocellulosic biomass in the presence of acid catalysts.  

PubMed

Transformation of lignocellulosic biomass to biofuels involves multiple processes, in which thermal decomposition, hydrotreatment are the most central steps. Current work focuses on the impact of several solid acids and Keggin-type heteropolyacids on the decomposition temperature (Td) of pine wood and the characterization of the resulted products. It has been observed that a mechanical mixture of solid acids with pine wood has no influence on Td, while the use of heteropolyacids lower the Td by 100°C. Moreover, the treatment of biomass with a catalytic amount of H3PW12O40 leads to formation of three fractions: solid, liquid and gas, which have been investigated by elemental analysis, TGA, FTIR, GC-MS and NMR. The use of heteropolyacid leads, at 300°C, to a selective transformation of more than 50 wt.% of the holocellulose part of the lignocellulosic biomass. Moreover, 60 wt.% of the catalyst H3PW12O40 are recovered. PMID:24055967

Larabi, Cherif; al Maksoud, Walid; Szeto, Kai C; Roubaud, Anne; Castelli, Pierre; Santini, Catherine C; Walter, Jean J

2013-11-01

98

A functionally stable manganese oxide oxygen evolution catalyst in acid.  

PubMed

First-row metals have been a target for the development of oxygen evolution reaction (OER) catalysts because they comprise noncritical elements. We now report a comprehensive electrochemical characterization of manganese oxide (MnOx) over a wide pH range, and establish MnOx as a functionally stable OER catalyst owing to self-healing, is derived from MnOx redeposition that offsets catalyst dissolution during turnover. To study this process in detail, the oxygen evolution mechanism of MnOx was investigated electrokinetically over a pH range spanning acidic, neutral, and alkaline conditions. In the alkaline pH regime, a ?60 mV/decade Tafel slope and inverse first-order dependence on proton concentration were observed, whereas the OER acidic pH regime exhibited a quasi-infinite Tafel slope and zeroth-order dependence on proton concentration. The results reflect two competing mechanisms: a one-electron one-proton PCET pathway that is dominant under alkaline conditions and a Mn(3+) disproportionation process, which predominates under acidic conditions. Reconciling the rate laws of these two OER pathways with that of MnOx electrodeposition elucidates the self-healing characteristics of these catalyst films. The intersection of the kinetic profile of deposition and that of water oxidation as a function of pH defines the region of kinetic stability for MnOx and importantly establishes that a non-noble metal oxide OER catalyst may be operated in acid by exploiting a self-healing process. PMID:24669981

Huynh, Michael; Bediako, D Kwabena; Nocera, Daniel G

2014-04-23

99

Analysis of recycled poly (styrene-co-butadiene) sulfonation: a new approach in solid catalysts for biodiesel production.  

PubMed

The disposal of solid waste is a serious problem worldwide that is made worse in developing countries due to inadequate planning and unsustainable solid waste management. In Mexico, only 2% of total urban solid waste is recycled. One non-recyclable material is poly (styrene-co-butadiene), which is commonly used in consumer products (like components of appliances and toys), in the automotive industry (in instrument panels) and in food services (e.g. hot and cold drinking cups and glasses). In this paper, a lab-scale strategy is proposed for recycling poly (styrene-co-butadiene) waste by sulfonation with fuming sulfuric acid. Tests of the sulfonation strategy were carried out at various reaction conditions. The results show that 75°C and 2.5 h are the operating conditions that maximize the sulfonation level expressed as number of acid sites. The modified resin is tested as a heterogeneous catalyst in the first step (known as esterification) of biodiesel production from a mixture containing tallow fat and canola oil with 59% of free fatty acids. The preliminary results show that esterification can reach 91% conversion in the presence of the sulfonated polymeric catalyst compared with 67% conversion when the reaction is performed without catalyst. PMID:24098857

Aguilar-Garnica, Efrén; Paredes-Casillas, Mario; Herrera-Larrasilla, Tito E; Rodríguez-Palomera, Felicia; Ramírez-Arreola, Daniel E

2013-01-01

100

Understanding the leaching properties of heterogenized catalysts: a combined solid-state and PHIP NMR study.  

PubMed

Para-hydrogen induced polarization (PHIP) NMR in solution, combined with solid-state NMR, can be efficiently employed for the highly sensitive in-situ detection of the leaching properties of immobilized catalysts. The knowledge of this property is important for possible applications of PHIP experiments in medicine, biology or industry, where leached catalysts poison the solution of hyperpolarized products. As experimental example Wilkinson's catalyst RhCl(PPh(3))(3) (1) immobilized on mesoporous silica is chosen. As model reaction the hydrogenation of styrene in solvents with different polarities (methanol-d(4), acetone-d(6) and benzene-d(6)) is used. A (31)P solid-state MAS-NMR study reveals that there are two different species of catalysts on the silica, namely coordinatively bound catalysts and physisorbed catalyst. Only the second species exhibits substantial leaching, which is visible in a strong PHIP enhancement of the reaction product. PMID:21435842

Gutmann, Torsten; Ratajczyk, Tomasz; Xu, Yeping; Breitzke, Hergen; Grünberg, Anna; Dillenberger, Sonja; Bommerich, Ute; Trantzschel, Thomas; Bernarding, Johannes; Buntkowsky, Gerd

2010-11-01

101

Phase transitions in a bed of vanadium catalyst for sulfuric acid production: experiment and modeling  

Microsoft Academic Search

Sulfur dioxide oxidation on vanadium catalysts in sulfuric acid production may cause phase transitions in the catalyst active component. These phase transitions involve crystallization of vanadium(IV), and may influence catalyst activity. In the present study, we show that reaction mixture flow through a fixed catalyst bed is accompanied by the moving front of crystal phase, which decreases SO2 conversion at

B. S. Bal’zhinimaev; N. P. Belyaeva; S. I. Reshetnikov; E. S. Yudina; A. A. Ivanov

2001-01-01

102

Mesoporous siliconiobium phosphate as a pure Brønsted acid catalyst with excellent performance for the dehydration of glycerol to acrolein.  

PubMed

The development of solid acid catalysts that contain a high density of Brønsted acid sites with suitable acidity, as well as a long lifetime, is one of great challenges for the efficient dehydration of glycerol to acrolein. Herein, we report on a mesoporous siliconiobium phosphate (NbPSi-0.5) composite, which is a promising solid Brønsted acid that is a potential candidate for such a high-performance catalyst. A variety of characterization results confirm that NbPSi-0.5 contains nearly pure Brønsted acid sites and has well-defined large mesopores. In addition, NbPSi-0.5 contains a similar amount of acid sites and exhibits weaker acidity than that of the highly acidic niobium phosphate and HZSM-5 zeolite. NbPSi-0.5 is quite stable and has a high activity for the dehydration of glycerol. The stability of NbPSi-0.5 is about three times higher than that of the reported catalyst. The significantly enhanced catalytic performance of NbPSi-0.5 can be attributed to 1) nearly pure Brønsted acidity, which suppresses side reactions that lead to coke formation; 2) a significant reduction of pore blocking due to the mesopores; and 3) a decrease in the amount and oxidation temperature of coke. PMID:23132784

Choi, Youngbo; Park, Dae Sung; Yun, Hyeong Jin; Baek, Jayeon; Yun, Danim; Yi, Jongheop

2012-12-01

103

Catalysts based in cerium oxide for wet oxidation of acrylic acid in the prevention of environmental risks  

Microsoft Academic Search

Acrylic acid is a refractory compound for the non-catalytic wet oxidation (WO) process and can seriously damage the environment when released in industrial effluents. Oxidation of acrylic acid by catalytic wet oxidation (CWO) was studied in slurry conditions in a high-pressure batch reactor at 200°C and 15bar of oxygen partial pressure. Several solid cerium-based catalysts prepared in our laboratory were

Adrián M. T Silva; Rita R. N Marques; Rosa M Quinta-Ferreira

2004-01-01

104

Relative reactivities of solid benzoic acids  

E-print Network

RELATIVE REACTIVITIES OF SOLID BENZOIC ACIDS A Thesis By EDWIN J, WARWAS Submitted to the Graduate College of the Texas A8rM University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE January 1967' Major... Subject: Chemistry RELATIVE REACTIVITIES OF SOLID BENZOIC ACIDS A Thesis By EDWIN J. WARWAS Submitted to the Graduate College of the Texas ASSAM University in partial fulfillment of the requirements for the degree of MAST ER OF S CIENCE January...

Warwas, Edwin James

2012-06-07

105

Superprotonic solid acids: Structure, properties, and applications  

NASA Astrophysics Data System (ADS)

In this work, the structure and properties of superprotonic MH nXO4-type solid acids (where M = monovalent cation, X = S, Se, P, As, and n = 1, 2) have been investigated and, for the first time, applied in fuel cell devices. Several MH nXO4-type solid acids are known to undergo a "superprotonic" solid-state phase transition upon heating, in which the proton conductivity increases by several orders of magnitude and takes on values of ˜10 -2O-1cm-1. The presence of superprotonic conductivity in fully hydrogen bonded solid acids, such as CsH2PO4, has long been disputed. In these investigations, through the use of pressure, the unequivocal identification of superprotonic behavior in both RbH2PO4 and CsH2PO 4 has been demonstrated, whereas for chemically analogous compounds with smaller cations, such as KH2PO4 and NaH2PO 4, superprotonic conductivity was notably absent. Such observations have led to the adoption of radius ratio rules, in an attempt to identify a critical ion size effect on the presence of superprotonic conductivity in solid acids. It has been found that, while ionic size does play a prominent role in the presence of superprotonic behavior in solid acids, equally important are the effects of ionic and hydrogen bonding. Next, the properties of superprotonic phase transition have been investigated from a thermodynamic standpoint. With contributions from this work, a formulation has been developed that accounts for the entropy resulting from both the disordering of both hydrogen bonds and oxy-anion librations in the superprotonic phase of solid acids. This formulation, fundamentally derived from Linus Pauling's entropy rules for ice, accurately accounts for the change in entropy through a superprotonic phase transition. Lastly, the first proof-of-priniciple fuel cells based upon solid acid electrolytes have been demonstrated. Initial results based upon a sulfate electrolyte, CsHSO4, demonstrated the viability of solid acids, but poor chemical stability under the highly reducing H2 gas environment of the fuel cell anode. Later experiments employing a CsH2PO4 electrolyte proved quite successful. The results of these solid acid-based fuel cell measurements suggest solid acids could serve as an alternative to current state-of-the-art fuel cell electrolytes.

Boysen, Dane Andrew

106

Synthesis of methyl esters from waste cooking oil using construction waste material as solid base catalyst.  

PubMed

The current research investigates synthesis of methyl esters by transesterification of waste cooking oil in a heterogeneous system, using barium meliorated construction site waste marble as solid base catalyst. The pretreated catalyst was calcined at 830 °C for 4h prior to its activity test to obtained solid oxide characterized by scanning electron microscopy/energy dispersive spectroscopy, BET surface area and pore size measurement. It was found that the as prepared catalyst has large pores which contributed to its high activity in transesterification reaction. The methyl ester yield of 88% was obtained when the methanol/oil molar ratio was 9:1, reaction temperature at 65 °C, reaction time 3h and catalyst/oil mass ratio of 3.0 wt.%. The catalyst can be reused over three cycles, offer low operating conditions, reduce energy consumption and waste generation in the production of biodiesel. PMID:23186664

Balakrishnan, K; Olutoye, M A; Hameed, B H

2013-01-01

107

Solid-state NMR concepts for the investigation of supported transition metal catalysts and nanoparticles.  

PubMed

In recent years, solid-state NMR spectroscopy has evolved into an important characterization tool for the study of solid catalysts and chemical processes on their surface. This interest is mainly triggered by the need of environmentally benign organic transformations ("green chemistry"), which has resulted in a large number of new catalytically active hybrid materials, which are organized on the meso- and nanoscale. Typical examples of these catalysts are supported homogeneous transition metal catalysts or transition metal nanoparticles (MNPs). Solid-state NMR spectroscopy is able to characterize both the structures of these materials and the chemical processes on the catalytic surface. This article presents recent trends both on the characterization of immobilized homogeneous transition metal catalysts and on the characterization of surface species on transition metal surfaces. PMID:23972428

Gutmann, Torsten; Grünberg, Anna; Rothermel, Niels; Werner, Mayke; Srour, Mohamad; Abdulhussain, Safaa; Tan, Shulin; Xu, Yeping; Breitzke, Hergen; Buntkowsky, Gerd

2013-01-01

108

[Experimental and kinetic modeling of acid/base and redox reactions over oxide catalysts  

SciTech Connect

The research has involved the characterization of catalyst acidity, [sup 2]D NMR studies of Bronsted acid sites, and kinetic, calorimetric, and spectroscopic studies of methylamine synthesis and related reactions over acid catalysts. Approach of this work was to explore quantitative correlations between factors that control the generation, type, strength, and catalytic properties of acid sites on zeolite catalysts. Microcalorimetry, thermogravimetric analysis, IR spectroscopy, and NMR spectroscopy have provided information about the nature and strength of acid sites in zeolites. This was vital in understanding the catalytic cycles involved in methylamine synthesis and related reactions over zeolite catalysts.

Not Available

1993-01-01

109

Involvement of solid acid on Al and Ga-doped porous silica in the Diels–Alder reaction  

Microsoft Academic Search

The Diels–Alder reaction of 2,3-dimethylbutadiene with p-benzoquinone using Al- and Ga-doped porous silica, i.e., MCM-41, zeolite, and amorphous silica, was studied focusing on individual effects of types, strength, and amount of acid sites and pore size of solid acid catalysts. MCM-41 and amorphous silica-based catalysts exhibited high activity for the Diels–Alder reaction, while zeolites only showed low activity. Comparison with

Atsushi Satsuma; Yoshihide Segawa; Hisao Yoshida; Tadashi Hattori

2004-01-01

110

Radiation-induced reactions of CO?H 2 gas mixtures over various solid catalysts  

NASA Astrophysics Data System (ADS)

Studies have been carried out of radiation-induced reactions of CO?H 2 gas mixtures in the presence of various solid catalysts in order to find possibilities of synthesizing organic raw materials from CO?H 2 by radiation for the future. The solid catalysts studied include Fischer-Tropsch catalyst (Fe?Cu supported by diatomaceous earth), titania(TiO 2), and silica gel. Analysis of the reaction products over Fischer-Tropsch catalyst or semiconductors such as TiO 2 and ZnO?Cr 2O 3 reveals that these solid catalysts do not sensitize the radiation chemical reaction of CO?H 2 but show the secondary effects on the reaction so as to induce the hydrogenation of olefins produced by the catalytic reaction and of aldehydes produced in gas phase by radiation. On the other hand, silica gel and other insulators such as alumina have been found to exhibit high catalytic activity in the formation of hydrocarbons from CO?H 2 under electron beam irradiation at 300°C. It has been shown experimentally that secondary reactions between H 2 and carbonaceous solid produced from CO make a substantial contribution to the formation of hydrocarbons from CO?H 2 over silica gel. In an attempt to find the role of silica gel in the reaction to produce hydrocarbons, radiation-induced reactions have been studied of H 2 with the carbonaceous solid that had been produced by irradiation of CO in the absence of solid catalyst, over TiO 2, or over silica gel. The results indicate that silica gel not only enhances the yields of CO 2 and carbonaceous solid from CO but also promotes hydrogenation reactions of the carbonaceous solid under electron beam irradiation.

Nagai, S.; Arai, H.; Hatada, M.

111

Matrix acidity determination: A bench scale method for predicting resid cracking of FCC catalysts  

SciTech Connect

Novel methods for determination of matrix acidity of cracking catalysts are discussed. Virgin matrix acidity is determined after complete destruction of the zeolite phase by acid treating the catalyst at pH 2. Properties of acid-treated catalyst closely approximate those of pure matrix. However, the virgin matrix acidity does not correlate with resid cracking performance of the catalyst under commercial or pilot plant conditions. A second method has been developed that facilitates the measurement of matrix acidity on a laboratory deactivated sample with properties similar to that in the commercial cracking unit. The approach is based on total destruction of the zeolite by steaming at 870 C for 5 h. Acidity of the steamed catalyst closely resembles that of steamed pure matrix and has a good correlation with the resid cracking activity in the pilot plant testing. Preservation of matrix acid sites during hydrothermal deactivation was shown to be an important requirement for achieving high resid cracking activity.

Alerasool, S.; Doolin, P.K.; Hoffman, J.F. (Ashland Petroleum Co., KY (United States). Research and Development Dept.)

1995-02-01

112

An Eco-Friendly Improved Protocol for the Synthesis of Bis(3-indolyl)methanes Using Poly(4-vinylpyridinium)hydrogen Sulfate as Efficient, Heterogeneous, and Recyclable Solid Acid Catalyst  

PubMed Central

Highly efficient and eco-friendly protocol for the synthesis of bis(3-indolyl)methanes by the electrophilic substitution reaction of indole with aldehydes catalyzed by poly(4-vinylpyridinium)hydrogen sulfate was described. Excellent yields, shorter reaction times, simple work-up procedure, avoiding hazardous organic solvents, and reusability of the catalyst are the most obvious advantages of this method. PMID:24052864

Banothu, Janardhan; Gali, Rajitha; Velpula, Ravibabu; Bavantula, Rajitha; Crooks, Peter A.

2013-01-01

113

Metal extraction from spent sulfuric acid catalyst through alkaline and acidic leaching  

Microsoft Academic Search

Spent catalyst from manufacture of sulfuric acid production (main elemental composition: 3.5% V, 0.63% Ni, 7.9% Fe and 9.64% Si) can be used as a secondary source of vanadium and nickel. Extraction of these metals was studied using two different leaching systems (alkaline and acidic). Statistical design of the experiments and ANOVA (analysis of variance) were performed in order to

A. Ognyanova; A. T. Ozturk; I. De Michelis; F. Ferella; G. Taglieri; A. Akcil; F. Vegliò

2009-01-01

114

Polymerization of Fatty Acid Methyl Ester Using Acidic Ionic Liquid as Catalyst  

Microsoft Academic Search

The polymerization of fatty acid methyl ester was investigated using biodiesel as the feed in the presence of a Brönsted-Lewis acidic ionic liquid (IL). A synergetic effect of Brönsted and Lewis acid sites enhanced the catalytic performance of the IL. 1-(3-Sulfonic acid)-propyl-3-methylimidazole chlorozincinate ([HO3S-(CH2)3-mim]Cl-ZnCl2, molar fraction of ZnCl2 was 0.67) was an efficient catalyst for the polymerization. The effects of

Shiwei LIU; Lu LI; Shitao YU; Congxia XIE; Fusheng LIU; Zhanqian SONG

2010-01-01

115

Wet oxidation of acid brown dye by hydrogen peroxide using heterogeneous catalyst Mn-salen-Y zeolite: A potential catalyst  

Microsoft Academic Search

Catalytic wet hydrogen peroxide oxidation of acid dye has been explored in this study. Manganese(III) complex of N,N?-ethylene bis(salicylidene-aminato) (salenH2) has been encapsulated in super cages of zeolite-Y by flexible ligand method. The catalyst has been characterized by FT-IR, XRD, TG\\/DTA and nitrogen adsorption studies. The effects of various parameters such as pH, catalyst and hydrogen peroxide concentration on the

Rathinam Aravindhan; Nishtar Nishad Fathima; Jonnalagadda Raghava Rao; Balachandran Unni Nair

2006-01-01

116

Sulfamic Acid as a Green, Efficient, Recyclable and Reusable Catalyst for Direct Addition of Aliphatic Acid with Cyclic Olefins  

Microsoft Academic Search

Sulfamic acid has been used as a catalyst for esterification of cyclic olefins with aliphatic acids, and good olefins conversion as well as excellent esters selectivity was obtained. The catalyst could be recycled easily by filtration and directly reused in the next run with satisfactory results.

Bo Wang; Yanlong Gu; Liming Yang; Jishuan Suo; Okamoto Kenichi

2004-01-01

117

Acid properties of silica-alumina catalysts and catalytic degradation of polyethylene  

Microsoft Academic Search

A relationship between the acid strengths and amounts of silica-alumina catalysts and the compositions of products formed by the catalytic degradation of polyethylene at 673 K was studied. The acid strengths and amounts were varied with SiOâ\\/AlâOâ weight ratio in the catalysts. Although the resulting products and amounts were varied with SiOâ\\/AlâOâ weight ratio in the catalysts. Although the resulting

Hironobu Ohkita; Ryuji Nishiyama; Yoshihisa Tochihara; Takanori Mizushima; Noriyoshi Kakuta; Yoshio Morioka; Akifumi Ueno; Yukihiko Namiki; Susumu Tanifuji; Hiroshi Katoh; Hideo Sunazuka; Reikichi Nakayama; Takashi Kuroyanagi

1993-01-01

118

Acidic and basic surface sites of zirconia-based biomass gasification gas clean-up catalysts  

Microsoft Academic Search

The surface structures of ZrO2, Y2O3–ZrO2 and SiO2–ZrO2 catalysts were studied in relation to their basicity and acidity, and the relationship between surface structure and gasification gas clean-up activity was evaluated. The physical properties of the catalysts were characterized by BET, XRD and Raman spectroscopy. The basicity and acidity of the catalysts were measured by CO2-TPD and NH3-TPD, respectively. The

Tiia Viinikainen; Hanne Rönkkönen; Heather Bradshaw; Hazel Stephenson; Sanna Airaksinen; Matti Reinikainen; Pekka Simell; Outi Krause

2009-01-01

119

Reaction of 5-ethylidene-2-norbomene with formic acid: cation exchange resins as catalysts  

Microsoft Academic Search

The esterification of formic acid with ethylidene norbornene (ENB), i.e. 5-ethylidene bicyclo[2.2.1]hept 2-ene was carried out with and without cation exchange resins as catalysts. The effect of various parameters e.g. speed of agitation, catalyst loading, mole ratio of the reactants, temperature, concentration of formic acid in aqueous solutions were studied to optimise the reaction conditions; the reusability of catalysts was

Basudeb Saha

1998-01-01

120

Heterogeneous interesterification of triacylglycerols catalyzed by using potassium-doped alumina as a solid catalyst.  

PubMed

Heterogeneous interesterification of vegetable oils offers an environmentally more attractive option for the modification of edible oils to meet the specifications for certain food applications. In this work, potassium-doped alumina (KNO3/Al2O3) was prepared using an impregnation method, followed by calcinations at a temperature of 700 °C, and was then employed as heterogeneous catalysts for the interesterification of triacylglycerols. The solid catalyst was characterized by means of Hammett titration method, power X-ray diffraction, scanning electron microscopy, and nitrogen adsorption-desorption techniques. It was determined that the catalyst with KNO3 loading of 35% on alumina support and calcined at 700 °C exhibited the best catalytic activities toward the interesterification between soybean oil and methyl stearate under solvent-free conditions. Also, the solid base catalyst was successfully applied to the interesterification of soybean oil and lard blends in a heterogeneous manner. The physicochemical properties of the interesterified products were investigated using gas chromatography, high-performance liquid chromatography, and confocal laser scanning microscopy. It was found that the slip melting point and crystal morphology had a significant variation after the interesterification reaction as a result of the modification in the TAG profile. With the solid base catalyst, an environmentally friendly approach for the interesterification of triacylglycerols in a heterogeneous manner was developed. PMID:25298314

Xie, Wenlei; Chen, Jing

2014-10-29

121

Manipulating catalytic pathways: deoxygenation of palmitic acid on multifunctional catalysts.  

PubMed

The mechanism of the catalytic reduction of palmitic acid to n-pentadecane at 260 °C in the presence of hydrogen over catalysts combining multiple functions has been explored. The reaction involves rate-determining reduction of the carboxylic group of palmitic acid to give hexadecanal, which is catalyzed either solely by Ni or synergistically by Ni and the ZrO2 support. The latter route involves adsorption of the carboxylic acid group at an oxygen vacancy of ZrO2 and abstraction of the ?-H with elimination of O to produce the ketene, which is in turn hydrogenated to the aldehyde over Ni sites. The aldehyde is subsequently decarbonylated to n-pentadecane on Ni. The rate of deoxygenation of palmitic acid is higher on Ni/ZrO2 than that on Ni/SiO2 or Ni/Al2O3, but is slower than that on H-zeolite-supported Ni. As the partial pressure of H2 is decreased, the overall deoxygenation rate decreases. In the absence of H2, ketonization catalyzed by ZrO2 is the dominant reaction. Pd/C favors direct decarboxylation (-CO2), while Pt/C and Raney Ni catalyze the direct decarbonylation pathway (-CO). The rate of deoxygenation of palmitic acid (in units of mmol moltotal metal(-1) h(-1)) decreases in the sequence r(Pt black) ?r(Pd black) >r(Raney Ni) in the absence of H2 . In situ IR spectroscopy unequivocally shows the presence of adsorbed ketene (C=C=O) on the surface of ZrO2 during the reaction with palmitic acid at 260 °C in the presence or absence of H2. PMID:23519964

Peng, Baoxiang; Zhao, Chen; Kasakov, Stanislav; Foraita, Sebastian; Lercher, Johannes A

2013-04-01

122

Silica-bonded N-propyl sulfamic acid as an efficient catalyst for the formylation and acetylation of alcohols and amines under heterogeneous conditions  

Microsoft Academic Search

A simple and efficient procedure for the preparation of silica-bonded N-propyl sulfamic acid (SBNPSA) by the reaction of 3-aminopropylsilica (1) and chlorosulfonic acid in chloroform is described. This solid acid is employed as a new catalyst for the formylation of alcohols and amines with ethyl formate under mild and heterogeneous conditions at room temperature with good to excellent yields. Also,

Khodabakhsh Niknam; Dariush Saberi

2009-01-01

123

SOLID-STATE SYNTHESIS OF HETEROCYCLIC HYDRAZONES USING MICROWAVES UNDER CATALYST-FREE CONDITIONS  

EPA Science Inventory

The reaction of neat 5- or 8-oxobenzopyran-2(1H)-ones with a variety of aromatic and heteroaromatic hydrazines are accelerated upon irradiation in a household microwave overn in the absence of any catalyst, solid support or solvent thus providing an environmentally friendly pathw...

124

SOLID-STATE SYNTHESIS OF HETEROCYCLIC HYDRAZONES USING MICROWAVES UNDER CATALYST-FREE CONDITIONS  

EPA Science Inventory

The reaction of neat 5- or 8-oxobenzopyran-2(1H)-ones with a variety of aromatic and heteroaromatic hydrazines are remarkably accelerated upon irradiation in a household microwave oven in the absence of any catalyst, solid support or solvent. The approach provides an attractive a...

125

SOLID-STATE SYNTHESIS OF HETEROCYCLIC HYDRAZONES USING MICROWAVES UNDER CATALYST-FREE CONDITIONS  

EPA Science Inventory

The reaction of neat 5- or 8-oxobenzopyran-2(1H)-0nes with a variety of aromatic and heteroaromatic hydrazines are remarkably acceleterated upon irradiation in a household microwave oven in the absence of any catalyst, solid support or solvent. The approach provides an attractive...

126

Dimerization of fatty acid methyl ester using Brönsted–Lewis acidic ionic liquid as catalyst  

Microsoft Academic Search

The dimerization of fatty acid methyl ester was investigated using Brönsted–Lewis acidic ionic liquids (ILs) as catalysts. It is found that IL (3-sulfonic acid)-propyl-triethylammonium chlorozincinate [HO3S–(CH2)3–NEt3]Cl–ZnCl2 (x=0.64, x: molar fraction of ZnCl2, x=moles of ZnCl2\\/(moles of ZnCl2+moles of ammonium salt) was of good catalytic performance. Under the optimum conditions m(biodiesel):m(IL) 15:1, biodiesel 15g, reaction temperature 240°C, and reaction time 5h,

Shiwei Liu; Hongxia Zhou; Shitao Yu; Congxia Xie; Fusheng Liu; Zhanqian Song

2011-01-01

127

Sonophotochemical Degradation of Bisphenol A with Solid Catalysts  

NASA Astrophysics Data System (ADS)

In order to investigate the degradation of bisphenol A (BPA) solution under sono, photo, sonocatalytic, photocatalytic and sonophotocatalytic processes, the BPA concentration and the total organic carbon (TOC) concentration were analyzed. The degradation rate of BPA was higher at high frequency (1 MHz) than at low frequency (300 kHz). At high frequency the acoustic period is shorter, and a high H2O2 concentration is therefore produced in aqueous solutions, which can enhance the degradation rate. The degradation rates of BPA were 0.0060, 0.0258, and 0.0451 min-1 under the sonocatalytic (1 MHz), photocatalytic and sonophotocatalytic processes respectively. The combined system of the sonochemical and photocatalytic processes can enhance the degradation rate of BPA compared with individual processes (sono and photocatalytic processes). The order of degradation of BPA (CuO>ZnO?TiO2) and TOC (TiO2>ZnO>CuO) differed for each of the three types of catalysts. The separation characteristics of catalysts were dissimilar for each of the two frequencies.

Myunghee Lim,; Younggyu Son,; Beomguk Park,; Jeehyeong Khim,

2010-07-01

128

Metal-organic frameworks as solid catalysts for the synthesis of nitrogen-containing heterocycles.  

PubMed

Metal-organic frameworks (MOFs) are finding increasing application as solid catalysts for liquid phase reactions leading to the synthesis of fine chemicals. In the present review we have focused on those reports describing the use of MOFs as catalysts for the synthesis of N-containing heterocycles that is a class of organic compounds with high added value due to their therapeutic use as drugs and their remarkable biological activities. After an introduction describing relevant structural features of MOFs and the nature of their active sites, this manuscript is organized according to the type of N-containing heterocycle synthesized employing MOFs as catalysts including pyrimidines, N-substituted piperidines, quinolines, indoles, N-substituted imidazoles, triazoles and heterocyclic amides. Special attention has been paid to the structural stability of MOFs under the reaction conditions, to the occurrence of metal leaching and reusability. The final section of this review provides some concluding remarks and future prospects for the field, with emphasis on showing the superiority of MOFs with respect to other solid catalysts for this type of liquid phase organic reactions and pointing out that the final goal in this research would be the use of these materials as catalysts in real industrial synthesis. PMID:24614959

Dhakshinamoorthy, Amarajothi; Garcia, Hermenegildo

2014-08-21

129

A NiFeCu alloy anode catalyst for direct-methane solid oxide fuel cells  

NASA Astrophysics Data System (ADS)

In this study, a new anode catalyst based on a NiFeCu alloy is investigated for use in direct-methane solid oxide fuel cells (SOFCs). The influence of the conductive copper introduced into the anode catalyst layer on the performance of the SOFCs is systematically studied. The catalytic activity for partial oxidation of methane and coking resistance tests are proposed with various anode catalyst layer materials prepared using different methods, including glycine nitrate process (GNP), physical mixing (PM) and impregnation (IMP). The surface conductivity tests indicate that the conductivities of the NiFe-ZrO2/Cu (PM) and NiFe-ZrO2/Cu (IMP) catalysts are considerably greater than that of NiFe-ZrO2/Cu (GNP), which is consistent with the SEM results. Among the three preparation methods, the cell containing the NiFe-ZrO2/Cu (IMP) catalyst layer performs best on CH4-O2 fuel, especially under reduced temperatures, because the coking resistance should be considered in real fuel cell conditions. The cell containing the NiFe-ZrO2/Cu (IMP) catalyst layer also delivers an excellent operational stability using CH4-O2 fuel for 100 h without any signs of decay. In summary, this work provides new alternative anode catalytic materials to accelerate the commercialization of SOFC technology.

Wang, Wei; Zhu, Huaiyu; Yang, Guangming; Park, Hee Jung; Jung, Doh Won; Kwak, Chan; Shao, Zongping

2014-07-01

130

Synthesis of Condensed Benzo[ N,N ]-Heterocycles by Microwave-Assisted Solid Acid Catalysis  

Microsoft Academic Search

The synthesis of several types of condensed benzo[N,N]-heterocycles such as benzimidazoles, benzodiazepines, quinoxalinones by a microwave-assisted solvent-free solid acid catalyzed\\u000a method is described. The commercially available, inexpensive K-10 montmorillonite is an excellent catalyst for the synthesis\\u000a of the target compounds. Our approach is based on the reactions of a wide variety of o-phenylenediamines, with ketones, aldehydes and bifunctional reagents, respectively.

Shainaz M. Landge; Béla Török

2008-01-01

131

Acid\\/epoxy reaction catalyst screening for low temperature (120 °C) powder coatings  

Microsoft Academic Search

This paper describes efforts to identify and screen suitable acid\\/epoxy reaction catalysts for low temperature curing (?120°C) powder coatings including tertiary amines, ammonium compounds, and metal complexes. Thermal analysis techniques were developed to aid evaluation of catalyst efficacy and a statistical design of experiments was carried out to study several commercially available catalysts. In three different resin\\/crosslinker systems, the effect

Glen Merfeld; Chris Molaison; Rainer Koeniger; A. Ersin Acar; Steve Mordhorst; Joe Suriano; Pat Irwin; Ron Singh Warner; Ken Gray; Mark Smith; Kevin Kovaleski; Greg Garrett; Steve Finley; Debora Meredith; Mike Spicer; Tom Naguy

2005-01-01

132

Method of performing sugar dehydration and catalyst treatment  

SciTech Connect

The invention includes a method of treating a solid acid catalyst. After exposing the catalyst to a mixture containing a sugar alcohol, the catalyst is washed with an organic solvent and is then exposed to a second reaction mixture. The invention includes a process for production of anhydrosugar alcohol. A solid acid catalyst is provided to convert sugar alcohol in a first sample to an anhydrosugar alcohol. The catalyst is then washed with an organic solvent and is subsequently utilized to expose a second sample. The invention includes a method for selective production of an anhydrosugar. A solid acid catalyst is provided within a reactor and anhydrosugar alcohol is formed by flowing a starting sugar alcohol into the reactor. The acid catalyst is then exposed to an organic solvent which allows a greater amount of additional anhydrosugar to be produced than would occur without exposing the acid catalyst to the organic solvent.

Hu, Jianli [Kennewick, WA; Holladay, Johnathan E [Kennewick, WA; Zhang, Xinjie [Burlington, MA; Wang, Yong [Richland, WA

2010-06-01

133

Catalysts  

NSDL National Science Digital Library

There are two types of catalysis reactions: homogeneous and heterogeneous. In a homogeneous reaction, the catalyst is in the same phase as the reactants. In a heterogeneous reaction, the catalyst is in a different phase from the reactants. This activity addresses homogeneous catalysis.

Consortium, The C.

2011-12-11

134

Gallium(III) triflate: an efficient and a sustainable Lewis acid catalyst for organic synthetic transformations.  

PubMed

Green chemical processes play a crucial role in sustainable development, and efficient recyclable catalysts that can be conveniently applied in various chemical reactions are the key elements for the development of sustainable synthetic processes. Many organic transformations rely on Lewis and Brønsted acid catalysts, and such molecules have been widely studied in organic synthesis. Over the years, researchers have looked for Lewis acid catalysts that provide high selectivity and high turnover frequency but are also stable in aqueous media and recoverable. Since the first preparation of trifluoromethanesulfonic acid by Hazeldine (triflic acid, HOTf), researchers have synthesized and used numerous metal triflates in a variety of organic reactions. Even though the rare earth metal triflates have played a major role in these studies, the majority of rare earth triflates lack one or more of the primary properties of sustainable catalysts: low cost and easy availability of the metals, easy preparation of triflates, aqueous/thermal stability, recyclability, and catalytic efficiency. In this Account, we describe the synthetic applications of Ga(OTf)(3) and its advantages over similar catalysts. Ga(OTf)(3) can be conveniently prepared from gallium metal or gallium chloride in excess of trifluoromethanesulfonic acid (triflic acid) under reflux. Among many Lewis acid catalysts recently studied, Ga(OTf)(3) is water tolerant and soluble and requires very low catalyst loading to drive various acid-catalyzed reactions including Friedel-Crafts alkylation, hydroxyalkylation, and acylation selectively and efficiently. In many reactions Ga(OTf)(3) demonstrated high chemo- and regioselectivity, high yields, excellent stability, and recyclability. We successfully synthesized many biologically active heterocycles and their fluoroanalogs under mild conditions. Many challenging reactions such as the ketonic Strecker reactions proceed efficiently via Ga(OTf)(3) catalysis. Because it is stable in water, this catalyst provides the opportunity to study substrates and develop new synthetic protocols in aqueous media, significantly reducing the production of hazardous waste from organic solvents and toxic catalyst systems. PMID:22148160

Prakash, G K Surya; Mathew, Thomas; Olah, George A

2012-04-17

135

Heterogeneous catalysts for the transformation of fatty acid triglycerides and their derivatives to fuel hydrocarbons  

NASA Astrophysics Data System (ADS)

The results of studies devoted to the catalysts for transformation of fatty acid triglycerides and their derivatives to fuel hydrocarbons are presented and described systematically. Various approaches to the use of heterogeneous catalysts for the production of biofuel from these raw materials are considered. The bibliography includes 134 references.

Yakovlev, Vadim A.; Khromova, Sofia A.; Bukhtiyarov, Valerii I.

2011-10-01

136

Glucose dehydration to 5-hydroxymethylfurfural in a biphasic system over solid acid foams.  

PubMed

A solid acid foam-structured catalyst based on a binderless zirconium phosphate (ZrPO) coating on aluminum foam was prepared. The catalyst layer was obtained by performing a multiple washcoating procedure of ZrPO slurry on the anodized aluminum foam. The effect of the pretreatment of ZrPO, the concentration of the slurry, and the amount of coating on the properties of the foam was studied. The catalytic properties of the prepared foams have been evaluated in the dehydration of glucose to 5-hydroxymethylfurfural (HMF) in a biphasic reactor. The catalytic behavior of ZrPO foam-based catalysts was studied in a rotating foam reactor and compared with that of bulk ZrPO. The effect of a silylation procedure on the selectivity of the process was shown over bulk and foam catalysts. This treatment resulted in a higher selectivity due to the deactivation of unselective Lewis acid sites. Addition of methylisobutylketone leads to extraction of HMF from the aqueous phase and stabilization of the selectivity to HMF over bulk ZrPO. A more intensive contact of the foam with the aqueous and organic phases leads to an increase in the selectivity and resistance to deactivation of the foam in comparison with a bulk catalyst. PMID:23616489

Ordomsky, Vitaly V; van der Schaaf, John; Schouten, Jaap C; Nijhuis, T Alexander

2013-09-01

137

Ultrasound assisted transesterification of waste cooking oil using heterogeneous solid catalyst.  

PubMed

Transesterification based biodiesel production from waste cooking oil in the presence of heterogeneous solid catalyst has been investigated in the present work. The effect of different operating parameters such as type of catalyst, catalyst concentration, oil to methanol molar ratio and the reaction temperature on the progress of the reaction was studied. Some studies related to catalyst reusability have also been performed. The important physicochemical properties of the synthesized biodiesel have also been investigated. The results showed that tri-potassium phosphate exhibits high catalytic activity for the transesterification of waste cooking oil. Under the optimal conditions, viz. catalyst concentration of 3wt% K3PO4, oil to methanol molar ratio of 1:6 and temperature of 50°C, 92.0% of biodiesel yield was obtained in 90min of reaction time. Higher yield was obtained in the presence of ultrasound as compared to conventional approach under otherwise similar conditions, which can be attributed to the cavitational effects. Kinetic studies have been carried out to determine the rate constant at different operating temperatures. It was observed that the kinetic rate constant increased with an increase in the temperature and the activation energy was found to be 64.241kJ/mol. PMID:24935026

Pukale, Dipak D; Maddikeri, Ganesh L; Gogate, Parag R; Pandit, Aniruddha B; Pratap, Amit P

2015-01-01

138

Solid-supported reagents and catalysts for the preparation of large ring compounds  

Microsoft Academic Search

Parallel combinatorial synthesis in solution using immobilized reagents, catalysts, and scavengers has emerged as a powerful technique for the preparation of diverse libraries of compounds. This technique has only recently been applied to the synthesis of large-ring compounds. In this comprehensive review several strategies are presented and discussed, including Pd-catalyzed allylic alkylation, Stille-coupling, macrolactonization and macrolactamization using solid supported reagents

Elisabeth Gonthier; Rolf Breinbauer

2005-01-01

139

Phase Behavior of Complex Superprotonic Solid Acids  

NASA Astrophysics Data System (ADS)

Superprotonic phase transitions and thermal behaviors of three complex solid acid systems are presented, namely Rb3H(SO4) 2-RbHSO4 system, Rb3H(SeO4)2-Cs 3H(SeO4)2 solid solution system, and Cs6 (H2SO4)3(H1.5PO4) 4. These material systems present a rich set of phase transition characteristics that set them apart from other, simpler solid acids. A.C. impedance spectroscopy, high-temperature X-ray powder diffraction, and thermal analysis, as well as other characterization techniques, were employed to investigate the phase behavior of these systems. Rb3H(SO4)2 is an atypical member of the M3H(XO4)2 class of compounds (M = alkali metal or NH4+ and X = S or Se) in that a transition to a high-conductivity state involves disproportionation into two phases rather than a simple polymorphic transition [1]. In the present work, investigations of the Rb3H(SO4)2-RbHSO4 system have revealed the disproportionation products to be Rb2SO 4 and the previously unknown compound Rb5H3(SO 4)4. The new compound becomes stable at a temperature between 25 and 140 °C and is isostructural to a recently reported trigonal phase with space group P3m of Cs5H 3(SO4)4 [2]. At 185 °C the compound undergoes an apparently polymorphic transformation with a heat of transition of 23.8 kJ/mol and a slight additional increase in conductivity. The compounds Rb3H(SeO4)2 and Cs 3H(SeO4)2, though not isomorphous at ambient temperatures, are quintessential examples of superprotonic materials. Both adopt monoclinic structures at ambient temperatures and ultimately transform to a trigonal (R3m) superprotonic structure at slightly elevated temperatures, 178 and 183 °C, respectively. The compounds are completely miscible above the superprotonic transition and show extensive solubility below it. Beyond a careful determination of the phase boundaries, we find a remarkable 40-fold increase in the superprotonic conductivity in intermediate compositions rich in Rb as compared to either end-member. The compound Cs6(H2SO4)3(H 1.5PO4)4 is unusual amongst solid acid compounds in that it has a complex cubic structure at ambient temperature and apparently transforms to a simpler cubic structure of the CsCl-type (isostructural with CsH2PO4) at its transition temperature of 100-120 °C [3]. Here it is found that, depending on the level of humidification, the superprotonic transition of this material is superimposed with a decomposition reaction, which involves both exsolution of (liquid) acid and loss of H2O. This reaction can be suppressed by application of sufficiently high humidity, in which case Cs6(H2SO4)3(H 1.5PO4)4 undergoes a true superprotonic transition. It is proposed that, under conditions of low humidity, the decomposition/dehydration reaction transforms the compound to Cs6(H2-0.5xSO 4)3(H1.5PO4)4-x, also of the CsCl structure type at the temperatures of interest, but with a smaller unit cell. With increasing temperature, the decomposition/dehydration proceeds to greater and greater extent and unit cell of the solid phase decreases. This is identified to be the source of the apparent negative thermal expansion behavior. References: [1] L.A. Cowan, R.M. Morcos, N. Hatada, A. Navrotsky, S.M. Haile, Solid State Ionics 179 (2008) (9-10) 305. [2] M. Sakashita, H. Fujihisa, K.I. Suzuki, S. Hayashi, K. Honda, Solid State Ionics 178 (2007) (21-22) 1262. [3] C.R.I. Chisholm, Superprotonic Phase Transitions in Solid Acids: Parameters affecting the presence and stability of superprotonic transitions in the MHnXO4 family of compounds (X=S, Se, P, As; M=Li, Na, K, NH4, Rb, Cs), Materials Science, California Institute of Technology, Pasadena, California (2003).

Panithipongwut, Chatr

140

Structural analysis of nickel doped cerium oxide catalysts for fuel reforming in solid oxide fuel cells  

NASA Astrophysics Data System (ADS)

As world energy demands increase, research into more efficient energy production methods has become imperative. Heterogeneous catalysis and nanoscience are used to promote chemical transformations important for energy production. These concepts are important in solid oxide fuel cells (SOFCs) which have attracted attention because of their potential to provide an efficient and environmentally favorable power generation system. The SOFC is also fuel-flexible with the ability to run directly on many fuels other than hydrogen. Internal fuel reforming directly in the anode of the SOFC would greatly reduce the cost and complexity of the device. Methane is the simplest hydrocarbon and a main component in natural gas, making it useful when testing catalysts on the laboratory scale. Nickel (Ni) and gadolinium (Gd) doped ceria (CeO 2) catalysts for potential use in the SOFC anode were synthesized with a spray drying method and tested for catalytic performance using partial oxidation of methane and steam reforming. The relationships between catalytic performance and structure were then investigated using X-ray diffraction, transmission electron microscopy, and environmental transmission electron microscopy. The possibility of solid solutions, segregated phases, and surface layers of Ni were explored. Results for a 10 at.% Ni in CeO2 catalyst reveal a poor catalytic behavior while a 20 at.% Ni in CeO2 catalyst is shown to have superior activity. The inclusion of both 10 at.% Gd and 10 at.% Ni in CeO2 enhances the catalytic performance. Analysis of the presence of Ni in all 3 samples reveals Ni heterogeneity and little evidence for extensive solid solution doping. Ni is found in small domains throughout CeO2 particles. In the 20 at.% Ni sample a segregated, catalytically active NiO phase is observed. Overall, it is found that significant interaction between Ni and CeO2 occurs that could affect the synthesis and functionality of the SOFC anode.

Cavendish, Rio

141

Synthesis of aliphatic polyesters by polycondensation using inorganic acid as catalyst  

PubMed Central

An effective route for the synthesis of aliphatic polyesters made from adipic or sebacic acid and alkanediols, using inorganic acid as a catalyst is reported. The monomer composition, reaction time, catalyst type, and reaction conditions were optimized to yield polyesters with weight average molecular weights of 23,000 for adipic acid and 85,000 for sebacic acid-based polyesters. The polymers melt at temperatures of 52–65°C and possess melt viscosity in the range of 5600–19,400cP. This route represents an alternative method for producing aliphatic polyesters for possible use in the preparation of degradable disposable medical supplies.

Sokolsky-Papkov, Marina; Langer, Robert; Domb, Abraham J.

2014-01-01

142

Bifunctional Organic Polymeric Catalysts with a Tunable Acid-Base Distance and Framework Flexibility  

NASA Astrophysics Data System (ADS)

Acid-base bifunctional organic polymeric catalysts were synthesized with tunable structures. we demonstrated two synthesis approaches for structural fine-tune. In the first case, the framework flexibility was tuned by changing the ratio of rigid blocks to flexible blocks within the polymer framework. In the second case, we precisely adjusted the acid-base distance by distributing basic monomers to be adjacent to acidic monomers, and by changing the chain length of acidic monomers. In a standard test reaction for the aldol condensation of 4-nitrobenzaldehyde with acetone, the catalysts showed good reusability upon recycling and maintained relatively high conversion percentage.

Chen, Huanhui; Wang, Yanan; Wang, Qunlong; Li, Junhui; Yang, Shiqi; Zhu, Zhirong

2014-09-01

143

Surface properties of pillared acid-activated bentonite as catalyst for selective production of linear alkylbenzene  

NASA Astrophysics Data System (ADS)

Acid-activated and pillared montmorillonite were prepared as novel catalysts for alkylation of benzene with 1-decene for production of linear alkylbenzene. The catalysts were characterized by X-ray diffraction, FT-IR spectroscopy, N2 adsorption isotherms, temperature programmed desorption of NH3, scanning electron microscopy and elemental and thermal analysis techniques. It was found that acid-activation of clays prior to pillaring increased the porosity, total specific surface area, total pore volume and surface acidity of the catalysts. Optimization of the reaction conditions was performed by varying catalyst concentration (0.25-1.75 wt%), reactants ratio (benzene to 1-decene of 8.75, 12 and 15) and temperature (115-145 °C) in a batch slurry reactor. Under optimized conditions more than 98% conversion of 1-decene, and complete selectivity for monoalkylbenzenes were achieved.

Faghihian, Hossein; Mohammadi, Mohammad Hadi

2013-01-01

144

Production of biodiesel and lactic acid from rapeseed oil using sodium silicate as catalyst.  

PubMed

Biodiesel and lactic acid from rapeseed oil was produced using sodium silicate as catalyst. The transesterification in the presence of the catalyst proceeded with a maximum yield of 99.6% under optimized conditions [3% (w/w) sodium silicate, methanol/oil molar ratio 9/1, reaction time 60 min, reaction temperature 60°C, and stirring rate 250 rpm]. After six consecutive transesterification reactions, the catalyst was collected and used for catalysis of the conversion of glycerol to lactic acid. A maximum yield of 80.5% was achieved when the reaction was carried out at a temperature of 300°C for 90 min. Thus, sodium silicate is an effective catalyst for transesterification and lactic acid production from the biodiesel by-product, glycerol. PMID:21530245

Long, Yun-Duo; Guo, Feng; Fang, Zhen; Tian, Xiao-Fei; Jiang, Li-Qun; Zhang, Fan

2011-07-01

145

Microwave-assisted solid acid-catalyzed one-pot synthesis of isobenzofuran-1(3 H)-ones  

Microsoft Academic Search

A new, solid acid-catalyzed microwave-assisted environmentally benign synthesis of isobenzofuran-1(3H)-ones is described. Montmorillonite K-10 appeared to be an excellent catalyst for the condensation and successive lactonization reactions. Reaction of phthalaldehydic acid (2-carboxybenzaldehyde) with methylaryl and cyclic ketones was initiated by microwave irradiation and occurred in one step. The reactions were complete in 10–30 minutes providing excellent yields (90–98%).

Shainaz M. Landge; Martin Berryman; Béla Török

2008-01-01

146

Magnetic solid base catalyst CaO/CoFe2O4 for biodiesel production: Influence of basicity and wettability of the catalyst in catalytic performance  

NASA Astrophysics Data System (ADS)

A novel magnetic solid base catalyst CaO/CoFe2O4 was successfully prepared with CoFe2O4 synthesized by hydrothermal method as the magnetic core and applied to the transesterification of soybean oil for the production of biodiesel. The magnetic solid base catalysts were characterized by a series of techniques including CO2-TPD, powder XRD, TGA, TEM and the contact angle measurement of the water droplet. It was demonstrated that CaO/CoFe2O4 has stronger magnetic strength indicating perfect utility for repeated use and better basic strength. Compared with CaO/ZnFe2O4 and CaO/MnFe2O4, solid base catalyst CaO/CoFe2O4 has better catalytic performance, weaker hydroscopicity and stronger wettability, demonstrating that catalytic performance was relative to both basicity of catalyst and the full contact between the catalyst and the reactants, but the latter was a main factor in the catalytic system.

Zhang, Pingbo; Han, Qiuju; Fan, Mingming; Jiang, Pingping

2014-10-01

147

[Experimental and kinetic modeling of acid/base and redox reactions over oxide catalysts]. Technical progress report  

SciTech Connect

The research has involved the characterization of catalyst acidity, {sup 2}D NMR studies of Bronsted acid sites, and kinetic, calorimetric, and spectroscopic studies of methylamine synthesis and related reactions over acid catalysts. Approach of this work was to explore quantitative correlations between factors that control the generation, type, strength, and catalytic properties of acid sites on zeolite catalysts. Microcalorimetry, thermogravimetric analysis, IR spectroscopy, and NMR spectroscopy have provided information about the nature and strength of acid sites in zeolites. This was vital in understanding the catalytic cycles involved in methylamine synthesis and related reactions over zeolite catalysts.

Not Available

1993-07-01

148

CO oxidation on Ta-Modified SnO2 solid solution catalysts  

NASA Astrophysics Data System (ADS)

Co-precipitation method was adopted to prepare Sn-Ta mixed oxide catalysts with different Sn/Ta molar ratios and used for CO oxidation. The catalysts were investigated by N2-Brunauer-Emmett-Teller (N2-BET), X-ray diffraction patterns (XRD), H2-temperature programmed reduction (H2-TPR), Thermal Gravity Analysis - Differential Scanning Calorimetry (TGA-DSC) techniques. It is revealed that a small amount of Ta cations can be doped into SnO2 lattice to form solid solution by co-precipitation method, which resulted in samples having higher surface areas, improved thermal stability and more deficient oxygen species on the surface of SnO2. As a result, those Sn rich Sn-Ta solid solution catalysts with an Sn/Ta molar ratio higher than 4/2 showed significantly enhanced activity as well as good resistance to water deactivation. It is noted here that if tantala disperses onto SnO2 surface instead of doping into its lattice, it will then have negative effect on its activity.

Han, Xue; Xu, Xianglan; Liu, Wenming; Wang, Xiang; Zhang, Rongbin

2013-06-01

149

Improved anode catalysts for coal gas-fueled phosphoric acid fuel cells  

NASA Astrophysics Data System (ADS)

The development, optimization and demonstration of contaminant-tolerant anode catalyst formulations for phosphoric acid fuel cells is the overall objective of this project. The goal is to develop supported catalyst systems that will not only be able to operate on feed gases containing high levels of CO, H2S, and COS, but will, in fact, encourage the shift reaction to convert the CO to additional H2 or anodically convert CO to CO2, boosting the power content of the fuel gas. Of CO conversion is not feasible, a secondary goal is to demonstrate CO- and H2S-tolerant catalysts so that gas cleanup requirements can be minimized. Upper limits for individual contaminant concentrations and mixtures of contaminant gases that can be tolerated by the advanced anode catalysts will be determined. This quarter, the two catalysts selected for testing were Pt-Ti-Ru and Pt-Ti-ZA, hydrogen/hydrogen cell testing continued.

Kackley, Nancy; Kosek, John A.

1989-09-01

150

Sulfamic acid as a cost-effective catalyst instead of metal-containing acids for acetolysis of cyclic ethers  

Microsoft Academic Search

Sulfamic acid has been used as an efficient catalyst and green alternative for metal-containing acidic materials to promote the acetolysis reaction of THF to produce 1,4-diacetoxybutane. This method is also applicable to the acetolysis of other cyclic ethers, such as methyl substituted THF and tetrahydropyran and 1,4-dioxane, which is less reactive.

Bo Wang; Yanlong Gu; Weizhong Gong; Yuru Kang; Liming Yang; Jishuan Suo

2004-01-01

151

Direct asymmetric hydrogenation of ?-keto acids by using the highly efficient chiral spiro iridium catalysts.  

PubMed

A new efficient and highly enantioselective direct asymmetric hydrogenation of ?-keto acids employing the Ir/SpiroPAP catalyst under mild reaction conditions has been developed. This method might be feasible for the preparation of a series of chiral ?-hydroxy acids on a large scale. PMID:25384177

Yan, Pu-Cha; Xie, Jian-Hua; Zhang, Xiang-Dong; Chen, Kang; Li, Yuan-Qiang; Zhou, Qi-Lin; Che, Da-Qing

2014-11-20

152

Highly enantioselective electrophilic ?-bromination of enecarbamates: chiral phosphoric acid and calcium phosphate salt catalysts.  

PubMed

Metal-free chiral phosphoric acids and chiral calcium phosphates both catalyze highly enantio- and diastereoselective electrophilic ?-bromination of enecarbamates to provide an atom-economical synthesis of enantioenriched vicinal haloamines. Either enantiomer can be formed in good yield with excellent diastereo- and enantioselectivity simply by switching the catalyst from a phosphoric acid to its calcium salt. PMID:22686436

Alix, Aurélien; Lalli, Claudia; Retailleau, Pascal; Masson, Géraldine

2012-06-27

153

Cyclic amino acid salts as catalysts for the asymmetric Michael reaction  

Microsoft Academic Search

Different chiral cyclic amino acid alkali metal and ammonium salts were used as catalysts for the asymmetric Michael addition of aldehydes to nitrostyrene. The reaction yield and stereoselectivity depend slightly on the salt cation. The highest yield of the reaction (up to 100%) was obtained with (S)-morpholine-3-carboxylic acid salts, which gave moderate to good enantioselectivities (up to 72% ee) and

Marju Laars; Henri Raska; Margus Lopp; Tõnis Kanger

2010-01-01

154

Bioleaching of spent refinery processing catalyst using Aspergillus niger with high-yield oxalic acid  

Microsoft Academic Search

A spent refinery processing catalyst was physically and chemically characterized, and subjected to one-step and two-step bioleaching processes using Aspergillus niger. During bioleaching of the spent catalysts of various particle sizes (“as received”, 100–150?m, <37?m, and x¯=2.97 (average) ?m) and pulp densities, the biomass dry weight and pH were determined. The corresponding leach liquor was analysed for excreted organic acids

Deenan Santhiya; Yen-Peng Ting

2005-01-01

155

Novel acidic ionic liquids mediated zinc chloride: Highly effective catalysts for the Beckmann rearrangement  

Microsoft Academic Search

A mild, efficient, and eco-friendly procedure for Beckmann rearrangement was catalyzed by a series of novel Brønsted acidic ionic liquids (ILs) consisiting double –SO3H cations mediated zinc chloride (ILs–ZnCl2) catalytic system. High yields of amides were achieved by using 5mol.% of ILs–ZnCl2 catalysts. In addition, the catalyst system could be recycled and reused for three times.

Xiaofei Liu; Linfei Xiao; Hugjiltu Wu; Zhen Li; Jing Chen; Chungu Xia

2009-01-01

156

Process for the generation of .alpha., .beta.-unsaturated carboxylic acids and esters using niobium catalyst  

DOEpatents

A process using a niobium catalyst includes the step of reacting an ester or carboxylic acid with oxygen and an alcohol in the presence a niobium catalyst to respectively produce an .alpha.,.beta.-unsaturated ester or carboxylic acid. Methanol may be used as the alcohol, and the ester or carboxylic acid may be passed over the niobium catalyst in a vapor stream containing oxygen and methanol. Alternatively, the process using a niobium catalyst may involve the step of reacting an ester and oxygen in the presence the niobium catalyst to produce an .alpha.,.beta.-unsaturated carboxylic acid. In this case the ester may be a methyl ester. In either case, niobium oxide may be used as the niobium catalyst with the niobium oxide being present on a support. The support may be an oxide selected from the group consisting of silicon oxide, aluminum oxide, titanium oxide and mixtures thereof. The catalyst may be formed by reacting niobium fluoride with the oxide serving as the support. The niobium catalyst may contain elemental niobium within the range of 1 wt % to 70 wt %, and more preferably within the range of 10 wt % to 30 wt %. The process may be operated at a temperature from 150 to 450.degree. C. and preferably from 250 to 350.degree. C. The process may be operated at a pressure from 0.1 to 15 atm. absolute and preferably from 0.5-5 atm. absolute. The flow rate of reactants may be from 10 to 10,000 L/kg.sub.(cat) /h, and preferably from 100 to 1,000 L/kg.sub.(cat) /h.

Gogate, Makarand Ratnakav (Durham, NC); Spivey, James Jerome (Cary, NC); Zoeller, Joseph Robert (Kingsport, TN)

1999-01-01

157

Efficient synthesis of spironaphthopyrano [2,3-d]pyrimidine-5,3'-indolines under solvent-free conditions catalyzed by SBA-Pr-SO3H as a nanoporous acid catalyst.  

PubMed

A green, simple one-pot synthesis of spironaphthopyrano[2,3-d]pyrimidine-5,3'-indoline derivatives by a three-component reaction of isatins, 2-naphthol, and barbituric acids under solvent-free conditions in the presence of SBA-Pr-SO(3)H has been accomplished. Sulfonic acid functionalized SBA-15 (SBA-Pr-SO(3)H) as a heterogeneous nanoporous solid acid catalyst was found to be an efficient and recyclable acid catalyst in this synthesis. PMID:25286212

Ziarani, Ghodsi Mohammadi; Lashgari, Negar; Faramarzi, Sakineh; Badiei, Alireza

2014-01-01

158

Reaction of dicyclopentadiene with formic acid and chloroacetic acid with and without cation-exchange resins as catalysts  

Microsoft Academic Search

The uncatalysed and catalysed (with cation-exchange resin) esterification of formic acid and chloroacetic acid, with dicyclopentadiene (DCPD), i.e. 4,7-methano-3a,4,7,7a-tetrahydroindene, was carried out. The effect of various parameters, e.g. speed of agitation, catalyst loading, mole ratio of the reactants, temperature, concentration of formic acid in aqueous solutions were studied to optimise the reaction conditions. DCPD cam be quantitatively converted to the

Basudeb Saha; Man Mohan Sharma

1997-01-01

159

Activity enhancement by acetic acid in cyclohexane oxidation using Ti-containing zeolite catalyst  

Microsoft Academic Search

Titanium silicalite (TS-1) was hydrothermally crystallised from a titanosilicate gel. The solid material was characterised by XRD, IR, and SEM, and then used as a catalyst in the liquid phase oxidation of cyclohexane with hydrogen peroxide. The reaction was carried out for 6h, at the temperature between 40 and 80°C. It was found that a marked increase in the catalytic

Tawan Sooknoi; Jumras Limtrakul

2002-01-01

160

Vanadium phosphate catalysts for biodiesel production from acid industrial by-products.  

PubMed

Biodiesel production from high acidity industrial by-products was studied using heterogeneous acid catalysts. These by-products contain 26-39% of free fatty acids, 45-66% of fatty acids methyl esters and 0.6-1.1% of water and are consequently inadequate for direct basic catalyzed transesterification. Macroporous vanadyl phosphate catalysts with V/P=1 (atomic ratio) prepared via sol-gel like technique was used as catalyst and it was possible to produce in one reaction batch a biodiesel contain 87% and 94% of FAME, depending on the by-product used as raw material. The initial FAME content in the by-products had a beneficial effect on the reactions because they act as a co-solvent, thus improving the miscibility of the reaction mixture components. The water formed during esterification process seems to hinder the esters formation, possibly due to competitive adsorption with methanol and to the promotion of the FAME hydrolysis reaction.The observed catalyst deactivation seems to be related to the reduction of vanadium species. However, spent catalysts can be regenerated, even partially, by reoxidation of the reduced vanadium species with air. PMID:22902409

Domingues, Carina; Correia, M Joana Neiva; Carvalho, Renato; Henriques, Carlos; Bordado, João; Dias, Ana Paula Soares

2013-04-10

161

Tungstophosphoric acid supported on silica gel (H 3PW 12O 40\\/SiO 2) as an eco-friendly, reusable and heterogeneous catalyst for chemoselective oxathioacetalization of carbonyl compounds in solution or under solvent-free conditions  

Microsoft Academic Search

Solid heteropoly acid supported on silica gel (H3PW12O40\\/SiO2) is easily used as a heterogonous, reusable and efficient catalyst for conversion of aromatic and aliphatic aldehydes and ketones to their corresponding 1,3-oxathiolanes at room temperature in solution or under solvent-free conditions. The catalyst can be easily recovered and reused for several times without loss of its activity.

Habib Firouzabadi; Nasser Iranpoor; Abbas Ali Jafari; Mohammad Reza Jafari

2006-01-01

162

Ammonolysis of esters of hydroxybenzoic acids on a boron phosphate catalyst  

SciTech Connect

In this investigation boron phosphate catalyst was used for ammonolysis of methyl and ethyl esters of salicylic and 4-hydroxybenzoic acids. It was shown that ammonolysis of methyl and ethyl esters of salicylic and 4-hydroxybenzoic acids in presence of boron phosphate catalyst at a ratio of 3-7 moles of ammonia per mole of ester in a contact time of 1-5 sec at 380-400/sub 0/ can be used for obtaining o- and p- hydroxybenzonitriles in yields of over 90% of the theoretical.

Suvorov, B.V.; Bukeikhanov, N.R.; Li, L.V.; Zulkasheva, A.Z.

1987-09-10

163

CO2-free power generation on an iron group nanoalloy catalyst via selective oxidation of ethylene glycol to oxalic acid in alkaline media.  

PubMed

An Fe group ternary nanoalloy (NA) catalyst enabled selective electrocatalysis towards CO2-free power generation from highly deliverable ethylene glycol (EG). A solid-solution-type FeCoNi NA catalyst supported on carbon was prepared by a two-step reduction method. High-resolution electron microscopy techniques identified atomic-level mixing of constituent elements in the nanoalloy. We examined the distribution of oxidised species, including CO2, produced on the FeCoNi nanoalloy catalyst in the EG electrooxidation under alkaline conditions. The FeCoNi nanoalloy catalyst exhibited the highest selectivities toward the formation of C2 products and to oxalic acid, i.e., 99 and 60%, respectively, at 0.4 V vs. the reversible hydrogen electrode (RHE), without CO2 generation. We successfully generated power by a direct EG alkaline fuel cell employing the FeCoNi nanoalloy catalyst and a solid-oxide electrolyte with oxygen reduction ability, i.e., a completely precious-metal-free system. PMID:25004118

Matsumoto, Takeshi; Sadakiyo, Masaaki; Ooi, Mei Lee; Kitano, Sho; Yamamoto, Tomokazu; Matsumura, Syo; Kato, Kenichi; Takeguchi, Tatsuya; Yamauchi, Miho

2014-01-01

164

CO2-Free Power Generation on an Iron Group Nanoalloy Catalyst via Selective Oxidation of Ethylene Glycol to Oxalic Acid in Alkaline Media  

PubMed Central

An Fe group ternary nanoalloy (NA) catalyst enabled selective electrocatalysis towards CO2-free power generation from highly deliverable ethylene glycol (EG). A solid-solution-type FeCoNi NA catalyst supported on carbon was prepared by a two-step reduction method. High-resolution electron microscopy techniques identified atomic-level mixing of constituent elements in the nanoalloy. We examined the distribution of oxidised species, including CO2, produced on the FeCoNi nanoalloy catalyst in the EG electrooxidation under alkaline conditions. The FeCoNi nanoalloy catalyst exhibited the highest selectivities toward the formation of C2 products and to oxalic acid, i.e., 99 and 60%, respectively, at 0.4?V vs. the reversible hydrogen electrode (RHE), without CO2 generation. We successfully generated power by a direct EG alkaline fuel cell employing the FeCoNi nanoalloy catalyst and a solid-oxide electrolyte with oxygen reduction ability, i.e., a completely precious-metal-free system. PMID:25004118

Matsumoto, Takeshi; Sadakiyo, Masaaki; Ooi, Mei Lee; Kitano, Sho; Yamamoto, Tomokazu; Matsumura, Syo; Kato, Kenichi; Takeguchi, Tatsuya; Yamauchi, Miho

2014-01-01

165

Oxidation of ethane to ethylene and acetic acid by MoVNbO catalysts M. Roussel1  

E-print Network

1 Oxidation of ethane to ethylene and acetic acid by MoVNbO catalysts M. Roussel1 , M. Bouchard1VNbO catalysts could be made up from (VNbMo)5O14-type microdomains embedded in MoO3 matrix seems still topical. Keywords MoVNbO catalysts; acetic acid; ethylene; mild oxidation of ethane; nanosized (VNbMo)5O14

Paris-Sud XI, Université de

166

Efficient conversion of triacylglycerols and fatty acids to biodiesel in a microwave reactor using metal triflate catalysts.  

PubMed

We report that catalytic quantities of the Lewis acidic metal catalysts scandium triflate and bismuth triflate promote conversion of oleic, linoleic, palmitic and myristic acids and their glyceryl triesters to the corresponding methyl esters (biodiesel) in greater than 90% yield upon microwave heating. Additionally, both catalysts could be recovered and reused in esterification reactions at least six times. PMID:20714659

Socha, Aaron M; Sello, Jason K

2010-10-21

167

Enhanced Oxygen Reduction Activity In Acid By Tin-Oxide Supported Au Nanoparticle Catalysts  

SciTech Connect

Gold nanoparticles supported on hydrous tin-oxide (Au-SnO{sub x}) are active for the four-electron oxygen reduction reaction in an acid electrolyte. The unique electrocatalytic of the Au-SnO is confirmed by the low amount of peroxide detected with rotating ring-disk electrode voltammetry and Koutecky-Levich analysis. In comparison, 10 wt % Au supported on Vulcan carbon and SnO{sub x} catalysts both produce significant peroxide in the acid electrolyte, indicating only a two-electron reduction reaction. Characterization of the Au-SnO{sub x} catalyst reveals a high-surface area, amorphous support with 1.7 nm gold metal particles. The high catalytic activity of the Au-SnO is attributed to metal support interactions. The results demonstrate a possible path to non-Pt catalysts for proton exchange membrane fuel cell cathodes.

Baker,W.; Pietron, J.; Teliska, M.; Bouwman, P.; Ramaker, D.; Swider-Lyons, K.

2006-01-01

168

Catalytic wet air oxidation of carboxylic acids on TiO{sub 2}-supported ruthenium catalysts  

SciTech Connect

The total oxidation of aqueous solutions of carboxylic acids by air was studied in a slurry reactor over the temperature range 180--100 C and oxygen partial pressure of 0.3--1.8 MPa in the presence of a 2.8%Ru/TiO{sub 2} catalyst. The influence of various parameters is presented: the catalytic wet air oxidation of succinic acid is 0 order with respect to succinic acid; the order with respect to oxygen pressure is 0.4, and the activation energy is ca. 125 kJ/mol. It was found that acetic acid, which is one of the intermediates, and CO{sub 2} have no retarding effect on the total organic carbon abatement rate of succinic acid. Substitution of one hydrogen atom of the methyl group in acetic acid by Cl, OH, or NH{sub 2} gives an increase of the oxidation rate. However, it was proposed that the low activity of acetic acid oxidation is due not only to the difficulty to oxidize the methyl group, but also to the low adsorption coefficient of acetic acid on ruthenium surface. Inorganic salts, such as sodium chloride, only slightly decrease the oxidation rate of acetic acid. The absence of metal ions (Ru, Ti) in the effluents after reaction and the absence of particle sintering indicate also a high stability of the catalyst under the conditions employed. The catalyst can be recycled without loss of activity after the second run. The activity becomes stable after the attainment of a steady-state coverage of the Ru particles by oxygen. The study of the effect of reduction-oxidation treatments of the catalyst showed that the activity depends on the oxidation state of the surface.

Beziat, J.C.; Besson, M.; Gallezot, P. [CNRS, Villeurbanne (France). Inst. de Recherches sur la Catalyse] [CNRS, Villeurbanne (France). Inst. de Recherches sur la Catalyse; Durecu, S. [TREDI, Vandoeuvre-les-Nancy (France). Dept. Recherche] [TREDI, Vandoeuvre-les-Nancy (France). Dept. Recherche

1999-02-15

169

Synthesis of quinolines by a solid acid-catalyzed microwave-assisted domino cyclization–aromatization approach  

Microsoft Academic Search

A microwave-assisted solid acid-catalyzed synthesis of quinolines from anilines and cinnamaldehydes is described. Use of montmorillonite K-10 results in a one-pot process; the cyclization and oxidation steps readily take place in a domino approach. Reactions were completed in a matter of minutes and provided excellent yields. The efficient and ecofriendly catalyst and the convenience of the product isolation make this

Omar De Paolis; Liliana Teixeira; Béla Török

2009-01-01

170

Platinum catalyst degradation in phosphoric acid fuel cells for stationary applications  

Microsoft Academic Search

A study is presented on the degradation of platinum alloy cathode catalysts operated in phosphoric acid fuel cells. The impact of time and temperature on the fundamental decay mechanism was studied with a surface area loss model and experimental electrochemical surface area measurements. It is suggested that platinum particle migration on the carbon support surface is the dominant mechanism for

T. T. Aindow; A. T. Haug; D. Jayne

2011-01-01

171

An efficient green catalyst comprising 12-tungstophosphoric acid and MCM-41: synthesis characterization and diesterification of succinic acid, a potential bio-platform molecule  

Microsoft Academic Search

An efficient green catalyst comprising 12-tungstophosphoric acid (TPA) and MCM-41 was synthesized. The catalytic activity was evaluated for liquid phase solvent free diesterification of succinic acid. The support and the synthesized catalyst were characterized by various physico-chemical techniques. Fourier transform infrared, diffuse reflectance spectroscopy, and P NMR spectra indicate that the Keggin structure of TPA was not destroyed after anchoring

Varsha Brahmkhatri; Anjali Patel

2012-01-01

172

An efficient green catalyst comprising 12-tungstophosphoric acid and MCM-41: synthesis characterization and diesterification of succinic acid, a potential bio-platform molecule  

Microsoft Academic Search

An efficient green catalyst comprising 12-tungstophosphoric acid (TPA) and MCM-41 was synthesized. The catalytic activity was evaluated for liquid phase solvent free diesterification of succinic acid. The support and the synthesized catalyst were characterized by various physico-chemical techniques. Fourier transform infrared, diffuse reflectance spectroscopy, and P NMR spectra indicate that the Keggin structure of TPA was not destroyed after anchoring

Varsha Brahmkhatri; Anjali Patel

2011-01-01

173

Supported organoiridium catalysts for alkane dehydrogenation  

DOEpatents

Solid supported organoiridium catalysts, a process for preparing such solid supported organoiridium catalysts, and the use of such solid supported organoiridium catalysts in dehydrogenation reactions of alkanes is provided. The catalysts can be easily recovered and recycled.

Baker, R. Thomas; Sattelberger, Alfred P.; Li, Hongbo

2013-09-03

174

Synergistic chiral ion pair catalysts for asymmetric catalytic synthesis of quaternary ?,?-diamino acids.  

PubMed

The combination of a chiral phosphate anion with a silver ion has been demonstrated as a powerful and synergistic ion pair catalyst for the aza-Mannich reaction. A series of valuable quaternary ?,?-diamino acid derivatives was obtained in high yield, and with excellent diastereo- (up to 25:1 dr) and enantioselectivity (up to 99% ee). The adducts can be smoothly transformed into the corresponding protected chiral quaternary ?,?-diamino acids by a one-pot hydrolysis reaction. PMID:22472066

Shi, Shi-Hui; Huang, Fu-Ping; Zhu, Ping; Dong, Zhen-Wen; Hui, Xin-Ping

2012-04-20

175

Hydrometallurgical route to recover molybdenum, nickel, cobalt and aluminum from spent hydrotreating catalysts in sulphuric acid medium.  

PubMed

This work describes a hydrometallurgical route for processing spent commercial catalysts (CoMo and NiMo/Al2O3), for recovering the active phase and support components. They were initially pre-oxidized (500 degrees C, 5h) in order to eliminate coke and other volatile species present. Pre-oxidized catalysts were dissolved in H2SO4 (9molL-1) at approximately 90 degrees C, and the remaining residues separated from the solution. Molybdenum was recovered by solvent extraction using tertiary amines. Alamine 304 presented the best performance at pH around 1.8. After this step, cobalt (or nickel) was separated by adding aqueous ammonium oxalate in the above pH. Before aluminum recovery, by adding NaOH to the acid solution, phosphorus (H2PO4-) was removed by passing the liquid through a strong anion exchange column. Final wastes occur as neutral and colorless sodium sulphate solutions and the insoluble solid in the acid leachant. The hydrometallurgical route presented in this work generates less final aqueous wastes, as it is not necessary to use alkaline medium during the metal recovery steps. The metals were isolated in very high yields (>98wt.%). PMID:18400377

Valverde, Ivam Macedo; Paulino, Jéssica Frontino; Afonso, Julio Carlos

2008-12-30

176

SOLID-STATE SYNTHESIS OF HETEROCYCLIC HYDRAZONES USING MICROWAVES UNDER CATALYST-FREE CONDITIONS: JOURNAL ARTICLE (1437A)  

EPA Science Inventory

NRMRL-CIN-1437A Jeselnik, M., Varma*, R.S., Polanc, S., and Kocevar, M. "Solid-State Synthesis of Heterocyclic Hydrazones using Microwaves under Catalyst-free Conditions http:///www.mdpi.net/ecsoc-5/." Fifth International Electronic Conference on Synthetic Organic Chemistry, h...

177

UreaFormaldehyde-Resin Gel Time As Affected by the pH Value, Solid Content, and Catalyst  

E-print Network

. If this correction is not precise, the glue line will be uncured or overcured, and this will result in poor bond­1569, 2007 Key words: adhesives; catalysts; gelation; resins; thermo- sets INTRODUCTION The pH value, solid bond strength, the press time and temperature must be adjusted for the pH envi- ronment

Wang, Siqun

178

Carbon quantum dots with photo-generated proton property as efficient visible light controlled acid catalyst  

NASA Astrophysics Data System (ADS)

Developing light-driven acid catalyst will be very meaningful for the controlled-acid catalytic processes towards a green chemical industry. Here, based on scanning electrochemical microscopy (SECM) and ?pH testing, we demonstrate that the 5-10 nm carbon quantum dots (CQDs) synthesized by electrochemical ablation of graphite have strong light-induced proton properties under visible light in solution, which can be used as an acid catalyst. The 5-10 nm CQDs' catalytic activity is strongly dependent on the illumination intensity and the temperature of the reaction system. As an effective visible light driven and controlled acid-catalyst, 5-10 nm CQDs can catalyze a series of organic reactions (esterification, Beckmann rearrangement and aldol condensation) with high conversion (34.7-46.2%, respectively) in water solution under visible light, while the 1-4 nm CQDs and 10-2000 nm graphite do not have such excellent catalytic activity. The use of 5-10 nm CQDs as a light responsive and controllable photocatalyst is truly a novel application of carbon-based nanomaterials, which may significantly push research in the current catalytic industry, environmental pollution and energy issues.Developing light-driven acid catalyst will be very meaningful for the controlled-acid catalytic processes towards a green chemical industry. Here, based on scanning electrochemical microscopy (SECM) and ?pH testing, we demonstrate that the 5-10 nm carbon quantum dots (CQDs) synthesized by electrochemical ablation of graphite have strong light-induced proton properties under visible light in solution, which can be used as an acid catalyst. The 5-10 nm CQDs' catalytic activity is strongly dependent on the illumination intensity and the temperature of the reaction system. As an effective visible light driven and controlled acid-catalyst, 5-10 nm CQDs can catalyze a series of organic reactions (esterification, Beckmann rearrangement and aldol condensation) with high conversion (34.7-46.2%, respectively) in water solution under visible light, while the 1-4 nm CQDs and 10-2000 nm graphite do not have such excellent catalytic activity. The use of 5-10 nm CQDs as a light responsive and controllable photocatalyst is truly a novel application of carbon-based nanomaterials, which may significantly push research in the current catalytic industry, environmental pollution and energy issues. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr03996j

Li, Haitao; Liu, Ruihua; Kong, Weiqian; Liu, Juan; Liu, Yang; Zhou, Lei; Zhang, Xing; Lee, Shuit-Tong; Kang, Zhenhui

2013-12-01

179

Tritium labeling of amino acids and peptides with liquid and solid tritium  

SciTech Connect

Amino acids and peptides were labeled with liquid and solid tritium at 21 K and 9 K. At these low temperatures radiation degradation is minimal, and tritium incorporation increases with tritium concentration and exposure time. Ring saturation in L-phenyl-alanine does not occur. Peptide linkage in oligopeptides is stable toward tritium. Deiodination in 3-iodotyrosine and 3,5-diiodotyrosine occurs readily and proceeds in steps by losing one iodine atom at a time. Nickel and noble metal supported catalysts when used as supports for dispersion of the substrate promote tritium labeling at 21 K. Our study shows that both liquid and solid tritium are potentially useful agents for labeling peptides and proteins. 11 refs., 1 fig., 3 tabs.

Peng, C.T.; Hua, R.L.; Souers, P.C.; Coronado, P.R.

1988-01-01

180

Tritium labeling of amino acids and peptides with liquid and solid tritium  

SciTech Connect

Amino acids and peptides were labeled with liquid and solid tritium at 21/degree/K and 9/degree/K. At these low temperatures radiation degradation is minimal, and tritium incorporation increases with tritium concentration and exposure time. Ring saturation in L-phenylalanine does not occur. Peptide linkage in oligopeptides is stable toward tritium. Deiodination in 3-iodotyrosine and 3,5-diiodotyrosine occurs readily and proceeds in steps by losing one iodine atom at a time. Nickel and noble metal supported catalysts when used as supports for dispersion of the substrate promote tritium labeling at 21 K. Our study shows that both liquid and solid tritiums are potentially useful agents for labeling peptides and proteins.

Souers, P.C.; Coronado, P.R.; Peng, C.T.; Hua, R.L.

1988-01-01

181

Hydrogenation of biofuels with formic acid over a palladium-based ternary catalyst with two types of active sites.  

PubMed

A composite catalyst including palladium nanoparticles on titania (TiO2) and on nitrogen-modified porous carbon (Pd/TiO2@N-C) is synthesized from palladium salts, tetrabutyl titanate, and chitosan. N2 sorption isotherms show that the catalyst has a high BET surface area (229?m(2) ?g(-1)) and large porosity. XPS and TEM characterization of the catalyst shows that palladium species with different chemical states are well dispersed across the TiO2 and nitrogen-modified porous carbon, respectively. The Pd/TiO2@N-C catalyst is very active and shows excellent stability towards hydrogenation of vanillin to 2-methoxy-4-methylphenol using formic acid as hydrogen source. This activity can be attributed to a synergistic effect between the Pd/TiO2 (a catalyst for dehydrogenation of formic acid) and Pd/N-C (a catalyst for hydrogenation of vanillin) sites. PMID:24861954

Wang, Liang; Zhang, Bingsen; Meng, Xiangju; Su, Dang Sheng; Xiao, Feng-Shou

2014-06-01

182

The effect of oleic acid stabilizer on the surface properties of bimetallic PtNi catalysts.  

PubMed

A detailed study on the surface properties of oleic acid-stabilized PtNi nanoparticles supported on silica is reported. The oleic acid-stabilized PtNi nanoparticles were synthesized using NaBH4 as the reducing agent at various temperatures and oleic acid concentrations, prior to incorporation onto the silica support. X-ray diffraction studies of the unsupported oleic acid-stabilized PtNi particles revealed that the PtNi existed as alloys. Upon incorporation onto silica support, surface properties of the catalysts were investigated using H2-temperature reduction (H2-TPR), H2-temperature desorption (H2-TPD) and H2-chemisorption techniques. It was found that for the bimetallic catalysts, no oxides or very little oxidation occurred. Furthermore, these catalysts exhibited both Pt and Ni active sites on its surface though the availability of Ni active sites was dominant. A comparison of the surface properties of these materials with those prepared without oleic acid in our previous work [N. H. H. Abu Bakar et al., J. Catal. 265, 63 (2009)] and how they affect the hydrogenation of benzene is also discussed. PMID:23901527

Abu Bakar, N H H; Abu Bakar, M; Bettahar, M M; Ismail, J; Monteverdi, S

2013-07-01

183

Synthesis of highly dispersed and active palladium/carbon nanofiber catalyst for formic acid electrooxidation  

NASA Astrophysics Data System (ADS)

Highly dispersed and active palladium/carbon nanofiber (Pd/CNF) catalyst is synthesized by NaBH4 reduction with trisodium citrate as the stabilizing agent. The obtained Pd/CNF catalyst is characterized by high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). The results show that the Pd nanoparticles with an average particle size of ca. 3.8 nm are highly dispersed on the CNF support even with a small ratio of citrate to Pd precursor, which is believed to be due to the pH adjustment of citrate stabilized colloidal Pd nanoparticles. The cyclic voltammetry and chronoamperometry techniques show that the obtained Pd/CNF catalyst exhibits good catalytic activity and stability for the electrooxidation of formic acid.

Qin, Yuan-Hang; Yue-Jiang; Yang, Hou-Hua; Zhang, Xin-Sheng; Zhou, Xing-Gui; Niu, Li; Yuan, Wei-Kang

2011-05-01

184

Biodiesel production from waste cooking oil using a heterogeneous catalyst from pyrolyzed rice husk.  

PubMed

A solid acid catalyst was prepared by sulfonating pyrolyzed rice husk with concentrated sulfuric acid, and the physical and chemical properties of the catalyst were characterized in detail. The catalyst was then used to simultaneously catalyze esterification and transesterification to produce biodiesel from waste cooking oil (WCO). In the presence of the as-prepared catalyst, the free fatty acid (FFA) conversion reached 98.17% after 3h, and the fatty acid methyl ester (FAME) yield reached 87.57% after 15 h. By contrast, the typical solid acid catalyst Amberlyst-15 obtained only 95.25% and 45.17% FFA conversion and FAME yield, respectively. Thus, the prepared catalyst had a high catalytic activity for simultaneous esterification and transesterification. In addition, the catalyst had excellent stability, thereby having potential use as a heterogeneous catalyst for biodiesel production from WCO with a high FFA content. PMID:24405650

Li, Ming; Zheng, Yan; Chen, Yixin; Zhu, Xifeng

2014-02-01

185

Production of biodiesel from mixed waste vegetable oil using an aluminium hydrogen sulphate as a heterogeneous acid catalyst  

Microsoft Academic Search

Al(HSO4)3 heterogeneous acid catalyst was prepared by the sulfonation of anhydrous AlCl3. This catalyst was employed to catalyze transesterification reaction to synthesis methyl ester when a mixed waste vegetable oil was used as feedstock. The physical and chemical properties of aluminum hydrogen sulphate catalyst were characterized by scanning electron microscopy (SEM) measurements, energy dispersive X-ray (EDAX) analysis and titration method.

Kasirajan Ramachandran; Pandian Sivakumar; Tamilarasan Suganya; Sahadevan Renganathan

2011-01-01

186

Acidity and Catalytic Activity of a Nafion-H\\/Silica Nanocomposite Catalyst Compared with a Silica-Supported Nafion Sample  

Microsoft Academic Search

The characterization of acid sites in the recently developed Nafion-H\\/silica nanocomposite catalyst was carried out through pyridine adsorption using the surface FT-IR technique. For comparison, an impregnated Nafion-H\\/SiO2 catalyst was also studied. A large number of free surface SO3H groups was detected on the surface of the Nafion-H\\/silica nanocomposite, in contrast to the impregnated catalyst. Pyridine adsorption demonstrates that Brønsted

Béla Török; Imre Kiricsi; Árpád Molnár; George A. Olah

2000-01-01

187

Catalytic wet air oxidation of acetic acid on carbon-supported ruthenium catalysts  

SciTech Connect

Ruthenium catalysts prepared by ion exchange of active carbons and high-surface-area graphites are active for the wet air oxidation of aqueous solutions of acetic acid (5-20 g/liter). A total conversion into CO{sub 2} can be achieved between 448 and 473 K using air as oxidizing agent. No leaching of ruthenium can be detected which indicates that the reaction proceeds on the heterogeneous catalysts. For the same particle size (1 nm), graphite-supported ruthenium catalysts are much more active (up to 0.4 mol h{sup -1} g{sub RU}{sup -1} at 473 K in a stirred batch reactor pressurized with air at 10 MPa) than active carbon-supported catalysts. The lower activities of the latters could be due to internal diffusion limitation since the 1-nm Ru particles are located inside the micropores. However, graphite-supported catalysts might be intrinsically more active because of an electron transfer from graphite to metal particles which would increase the resistance of ruthenium to oxygen poisoning. It was also shown that the activity of ruthenium is particle size dependent: the smaller the sizes, the lower the activities. This effect could be interpreted by the higher adsorption energy of oxygen on the small particles which produces a poisoning of the metal surface. From measurements of the reaction rates on the Ru/HSAG graphite catalyst at different temperatures, pressures, and acetic acid concentrations, it was established that the reaction orders were zero and 0.65 with respect to the concentration and oxygen pressure, respectively; the activation energy of the reaction was 100.5 kJ mol{sup -1}. An equation describing the reaction kinetics was proposed. 23 refs., 4 figs., 2 tabs.

Gallezot, P.; Chaumet, S.; Perrard, A. [Institut de Recherches sur la Catalyse, Villeurbanne (France)] [and others] [Institut de Recherches sur la Catalyse, Villeurbanne (France); and others

1997-05-01

188

Laser-synthesized catalysts  

SciTech Connect

A solid catalyst material is evaporated from a coating on a transparent solid substrate and is condensed onto a solid polymeric organic catalyst carrier or into a liquid, by passing a laser beam through said solid transparent substrate and onto the back of said coating and contacting said catalyst carrier or liquid with the evaporated catalyst material. Suitably, the laser source is a ruby or a rhodamine dye laser; a suitable catalyst material is rhodium metal; and a suitable solid polymeric organic catalyst carrier is polystyrene crosslinked by divinyl benzene and a suitable liquid is aqueous polyvinyl alcohol. The process minimizes the exposure to heat of the catalyst carrier or suspending liquid.

Menger-Hammond, E.L.; Novotny, M.

1984-09-18

189

Carbon-supported PtAu alloy nanoparticle catalysts for enhanced electrocatalytic oxidation of formic acid  

NASA Astrophysics Data System (ADS)

The understanding of the electrocatalytic activity of bimetallic nanoparticle catalysts requires the ability to precisely control the composition and phase properties. In this report, we describe a new strategy in the preparation of a series of carbon supported platinum-gold bimetallic nanoparticles with various bimetallic compositions which were loaded onto a carbon black support and subjected subsequently by thermal treatment (Pt100-mAum/C). The Pt100-mAum/C catalysts are characterized by X-ray diffraction (XRD), transmission electron spectroscopy (TEM), and induced coupled plasma-atomic emission spectroscopy (ICP-AES). The XRD pattern for the bimetallic nanoparticles shows single-phase alloy character. This ability enabled us to establish the correlation between the bimetallic composition and the electrocatalytic activity for formic acid (FA) electrooxidation. The electrocatalytic activities of the catalysts toward FA oxidation reaction are shown to strongly depend on the bimetallic PtAu composition. Within a wide range of bimetallic composition, the Pt50Au50/C catalyst shows the highest electrocatalytic activity for the FA oxidation, with a mass activity eight times higher than that of Pt/C. The high performance of the PtAu/C catalyst can be ascribed to the increased selectivity toward the FA dehydrogenation at the decreased availability of adjacent Pt atoms.

Chen, Guoqin; Li, Yunhua; Wang, Dong; Zheng, Li; You, Guirong; Zhong, Chuan-Jian; Yang, Lefu; Cai, Fan; Cai, Junxiu; Chen, Bing H.

2011-10-01

190

Reducing Pt use in the catalysts for formic acid electrooxidation via nanoengineered surface structure  

NASA Astrophysics Data System (ADS)

The design of active and durable catalysts for formic acid (FA) electrooxidation requires controlling the amount of three neighboring platinum atoms in the surface of Pt-based catalysts. Such requirement is studied by preparing Pt decorated Pd/C (donated as Pt-Pd/C) with various Pt:Pd molar ratios via galvanic displacement making the amount of three neighboring Pt atoms in the surface of Pt-Pd/C tunable. The decorated nanostructures are confirmed by XPS, HS-LEIS, cyclic voltammetry and chronoamperometric measurements, demonstrating that Pt-Pd/C (the optimal molar ratio, Pt:Pd = 1:250) exhibits superior activity and durability than Pd/C and commercial Pt/C (J-M, 20%) catalysts for FA electrooxidation. The mass activity of Pt-Pd/C (Pt:Pd = 1:250) (3.91 A mg-1) is about 98 and 6 times higher than that of commercial Pt/C (0.04 A mg-1) and Pd/C (0.63 A mg-1) at a given potential of 0.1 V vs SCE, respectively. The controlled synthesis of Pt-Pd/C lead to the formation of largely discontinuous Pd and Pt sites and inhibition of CO formation, exhibiting unprecedented electrocatalytic performance toward FA electrooxidation while the cost of the catalyst almost the same as Pd/C. These findings have profound implications to the design and nanoengineering of decorated surfaces of catalysts for FA electrooxidation.

Liao, Mengyin; Wang, Yulu; Chen, Guoqin; Zhou, Hua; Li, Yunhua; Zhong, Chuan-Jian; Chen, Bing H.

2014-07-01

191

Multinuclear solid film state NMR studies of metal oxide catalysts and minerals  

SciTech Connect

Several of our investigations of heterogeneous process by novel NMR experiments and analyses are reviewed and the utility and limitations of NMR spectroscopy for these areas discussed. Out studies have included the following: dynamics and arrangements of proton-containing adsorbates, primarily Bronsted acid sites and water, on the surface of zirconia and alumina catalysts; hydrogen dynamics and coordinates in synthetic aluminum oxyhydroxides; phase separation and crystallinity of synthetic minerals. In combination with the complementary results obtained in our laboratory via infrared spectroscopy, thermal analysis (primarily TGA and DSC), and catalytic activity measurements, these NMR data provide unique and valuable information on atomic and molecular dynamics, identities, and structures without requiring pristine, single crystal specimens.

Maxwell, R.S.; Stec, D.F.; Ellis, P.D. [Pacific Northwest National Lab., Richland, WA (United States)

1996-10-01

192

Methanol Production By Reduction Of Formic Acid Over Cu Catalyst Under Hydrothermal Conditions  

NASA Astrophysics Data System (ADS)

In this paper, a two-step process for converting carbon dioxide into methanol was established, consisting of conversion of carbon dioxide into formic acid and formic acid into methanol by hydrothermal treatment. For our previous studies has investigated the reduction of carbon dioxide to formic acid under hydrothermal conditions, the focus of this paper was set on the reduction of formic acid into methanol. The synthesis of methanol was examined by varying the following parameters: amount of Cu as catalyst, pH of the reagent, amount of Zn as reductant, reaction time and so on. The highest yield of 27.8% was achieved. The results indicated that Zn or Al was able to reduce formic acid to methanol more efficiently than other metal reductants. It was also found out that the addition of acid or alkali was not favorable for the synthesis of methanol.

Cheng, Min; Wu, Bing; Jin, Fangming; Duan, Xiaokun; Wang, Yuanqing

2010-11-01

193

Enhancement of Biodiesel Production from Marine Alga, Scenedesmus sp. through In Situ Transesterification Process Associated with Acidic Catalyst  

PubMed Central

The aim of this study was to increase the yield of biodiesel produced by Scenedesmus sp. through in situ transesterification by optimizing various process parameters. Based on the orthogonal matrix analysis for the acidic catalyst, the effects of the factors decreased in the order of reaction temperature (47.5%) > solvent quantity (26.7%) > reaction time (17.5%) > catalyst amount (8.3%). Based on a Taguchi analysis, the effects of the factors decreased in the order of solvent ratio (34.36%) > catalyst (28.62%) > time (19.72%) > temperature (17.32%). The overall biodiesel production appeared to be better using NaOH as an alkaline catalyst rather than using H2SO4 in an acidic process, at 55.07 ± 2.18% (based on lipid weight) versus 48.41 ± 0.21%. However, in considering the purified biodiesel, it was found that the acidic catalyst was approximately 2.5 times more efficient than the alkaline catalyst under the following optimal conditions: temperature of 70°C (level 2), reaction time of 10?hrs (level 2), catalyst amount of 5% (level 3), and biomass to solvent ratio of 1?:?15 (level 2), respectively. These results clearly demonstrated that the acidic solvent, which combined oil extraction with in situ transesterification, was an effective catalyst for the production of high-quantity, high-quality biodiesel from a Scenedesmus sp. PMID:24689039

Kim, Ga Vin; Choi, WoonYong; Kang, DoHyung; Lee, ShinYoung; Lee, HyeonYong

2014-01-01

194

Pd/C Synthesized with Citric Acid: An Efficient Catalyst for Hydrogen Generation from Formic Acid/Sodium Formate  

PubMed Central

A highly efficient hydrogen generation from formic acid/sodium formate aqueous solution catalyzed by in situ synthesized Pd/C with citric acid has been successfully achieved at room temperature. Interestingly, the presence of citric acid during the formation and growth of the Pd nanoparticles on carbon can drastically enhance the catalytic property of the resulted Pd/C, on which the conversion and turnover frequency for decomposition of formic acid/sodium formate system can reach the highest values ever reported of 85% within 160?min and 64?mol H2 mol?1 catalyst h?1, respectively, at room temperature. The present simple, low cost, but highly efficient CO-free hydrogen generation system at room temperature is believed to greatly promote the practical application of formic acid system on fuel cells. PMID:22953041

Wang, Zhi-Li; Yan, Jun-Min; Wang, Hong-Li; Ping, Yun; Jiang, Qing

2012-01-01

195

Solid-state 27 Al nuclear magnetic resonance investigation of plasma-facilitated NOx reduction catalysts  

SciTech Connect

Aluminum coordination distribution for alumina catalysts supported on mesoporous silica was examined. It is shown that aluminum coordination correlates to activity of the catalysts for plasma-enhanced, selective catalytic reduction of NOx with propene. Catalysts were prepared by incorporating aluminum onto the surface of a mesoporous silica support via three different post-synthesis routes to produce varying aluminum coordination.

Wang, Li Q.; Habeger, Craig F.; Aardahl, Chris L.; Rappe, Kenneth G.; Tran, Diana N.; Avila, Marisol

2002-07-01

196

Geminal Br?nsted Acid Ionic Liquids as Catalysts for the Mannich Reaction in Water  

PubMed Central

Quaternary ammonium geminal Brønsted acid ionic liquids (GBAILs) based on zwitterionic 1,2-bis[N-methyl-N-(3-sulfopropyl)-alkylammonium]ethane (where the carbon number of the alkyl chain is 4, 8, 10, 12, 14, 16, or 18) and p-toluenesulfonic acid monohydrate were synthesized. The catalytic ionic liquids were applied in three-component Mannich reactions with an aldehyde, ketone, and amine at 25 °C in water. The effects of the type and amount of catalyst and reaction time as well as the scope of the reaction were investigated. Results showed that GBAIL-C14 has excellent catalytic activity and fair reusability. The catalytic procedure was simple, and the catalyst could be recycled seven times via a simple separation process without noticeable decreases in catalytic activity. PMID:24837832

He, Leqin; Qin, Shenjun; Chang, Tao; Sun, Yuzhuang; Zhao, Jiquan

2014-01-01

197

Establishing the feasibility of coupled solid-phase extraction-solid-phase derivatization for acidic herbicides.  

PubMed

The significance of this research is that it improves analytical methodology used for organic chemicals in aqueous solutions by establishing the feasibility of heterogeneous chemical derivatization at the liquid-solid interface (i.e., solid-phase reaction or solid-phase derivatization). A solid-phase derivatization method for determining chlorinated herbicide acids was developed. Solid-phase extraction was used to concentrate and retain analytes on sorbents for subsequent solid-phase derivatization. Background interferences were removed from the chromatograms by electronically subtracting the responses of blank, nonfortified analyses from spiked samples. Two extraction sorbents (octadecyl bonded silica and polystyrene-divinylbenzene) and two derivatizing reagents (BF3-MeOH and trimethylsilyldiazomethane) were investigated. Recovery of 13 chlorinated herbicide acids--including pentachlorophenol, dinoseb, and bentazon (having a derivatizable functional group, -OH or -NH, bonded directly to a phenyl group); dicamba, picloram, acifluorfen, 3,5-dichlorobenzoic acid, and dacthal (having a derivatizable functional group, -COOH, bonded directly to a phenyl group); and 2,4-D, 2,4,5-T, dichlorprop, 2,4,5-TP, and 2,4-DB (having a derivatizable functional group, -COOH, bonded directly to a sp3 carbon atom)--was tested. The analytical method developed was proven successful for determining acidic herbicides, except for the dacthal diacid metabolite, in aqueous samples. PMID:17214997

Yu, Lan Z; Wells, Martha J M

2007-03-01

198

Studies on structure and properties of CNSL novolac resins prepared with succinic acid catalyst  

Microsoft Academic Search

Cashew nut shell liquid (CNSL) was used to prepare a glass fabric laminate. Two fast curing model resins were prepared using\\u000a cardanol and formaldehyde in the presence of succinic acid catalyst. The resins possess ortho-ortho and ortho-para linkages.\\u000a The curing kinetics of the resins showed that the resin prepared with mole ratio 0·8 possesses good curing characteristics.\\u000a The IR spectra

K Sathiyalekshmi

1993-01-01

199

Ionic Liquids as Catalysts for Sulfuric Acid Production and Cleaning of Flue Gases  

Microsoft Academic Search

\\u000a The present paper is concerned with catalytic pollution abatement of sulfur and nitrogen oxides in flue gases from industrial\\u000a sources. Especially fundamental and applied research on industrial catalysts and their model systems is presented with regards\\u000a to cleaning of flue gases from fossil fuel based power plants and plants producing sulfuric acid. Combined DeSOx and DeNOx processes are very common

Rasmus Fehrmann; K. M. Eriksen; S. B. Rasmussen; J. Winnick

200

Highly efficient Brønsted acidic ionic liquid-based catalysts for biodiesel synthesis from vegetable oils  

Microsoft Academic Search

Biodiesel has been produced by transesterification of canola oil with methanol in the presence of highly Brønsted acidic ionic liquids based on 1-benzyl-1H-benzimidazole, and the effect of reaction temperature, type and amount of catalyst, molar ratio and reaction time investigated. The results show that the 4B ionic liquid has the highest catalytic activity and best recyclability under the optimised reaction

M. Ghiaci; B. Aghabarari; S. Habibollahi; A. Gil

2011-01-01

201

COMPARISON OF CATALYSTS FOR DIRECT TRANSESTERIFICATION OF FATTY ACIDS IN FREEZE DRIED FORAGE SAMPLES  

Microsoft Academic Search

Our objective was to compare 1.09 M methanolic HCl to 14% BF3 in methanol as catalysts for direct transesterification of fatty acids in freeze-dried forage samples. Samples included blue grama (Bouteloua gracilis), fringed sage (Artemisia frigida), western wheatgrass (Pascopyrum smithii), needle-and-thread (Stipa comata), dalmation toadflax (Linaria dalmatica), needleleaf sedge (Carex eleocharis), and scarlet globemallow (Sphaelercea coccinea). Thin layer chromatographic evaluation

T. R. Weston; J. D. Derner; C. M. Murrieta; B. W. Hess

2006-01-01

202

MoVO-based catalysts for the oxidation of ethane to ethylene and acetic acid. Influence of niobium and/or palladium on physicochemical  

E-print Network

1 MoVO-based catalysts for the oxidation of ethane to ethylene and acetic acid. Influence to acetic acid and ethylene is examined. Catalysts without molybdenum (VNb031Pd3e-4Ox) are also studied for comparison. The structural properties of the precursors and of the catalysts obtained by calcination

Paris-Sud XI, Université de

203

The glmS ribozyme cofactor is a general acid-base catalyst.  

PubMed

The glmS ribozyme is the first natural self-cleaving ribozyme known to require a cofactor. The d-glucosamine-6-phosphate (GlcN6P) cofactor has been proposed to serve as a general acid, but its role in the catalytic mechanism has not been established conclusively. We surveyed GlcN6P-like molecules for their ability to support self-cleavage of the glmS ribozyme and found a strong correlation between the pH dependence of the cleavage reaction and the intrinsic acidity of the cofactors. For cofactors with low binding affinities, the contribution to rate enhancement was proportional to their intrinsic acidity. This linear free-energy relationship between cofactor efficiency and acid dissociation constants is consistent with a mechanism in which the cofactors participate directly in the reaction as general acid-base catalysts. A high value for the Brønsted coefficient (? ~ 0.7) indicates that a significant amount of proton transfer has already occurred in the transition state. The glmS ribozyme is the first self-cleaving RNA to use an exogenous acid-base catalyst. PMID:23113700

Viladoms, Júlia; Fedor, Martha J

2012-11-21

204

Solid–liquid equilibrium in the acetic acid–cyclohexane and acetic acid–trichloroacetic acid systems  

Microsoft Academic Search

Solid–liquid equilibrium in the binary systems acetic acid–cyclohexane and acetic acid–trichloroacetic acid was determined from time–temperature cooling and heating curves. The first system shows an eutectic point at x1?0.08 and T=271.9K. In the second system, a solid compound (1:1) was found and an equilibrium constant of the compound dissociation was calculated.

I Malijevská

2003-01-01

205

Freeze-drying of proteins in glass solids formed by basic amino acids and dicarboxylic acids.  

PubMed

The purpose of this study was to produce and characterize glass-state amorphous solids containing amino acids and organic acids that protect co-lyophilized proteins. Thermal analysis of frozen solutions containing a basic amino acid (e.g., L-arginine, L-lysine, L-histidine) and a hydroxy di- or tricarboxylic acid (e.g., citric acid, L-tartaric acid, DL-malic acid) showed glass transition of maximally freeze-concentrated solute at temperatures (T'g) significantly higher than those of the individual solute solutions. Mixing of the amino acid with some dicarboxylic acids (e.g., oxalic acid) also suggested an upward shift of the transition temperature. Contrarily, combinations of the amino acid with monocarboxylic acids (e.g., acetic acid) had T'gs between those of the individual solute solutions. Co-lyophilization of the basic amino acids and citric acid or L-tartaric acid resulted in amorphous solids that have glass transition temperatures (Tg) higher than the individual components. Mid- and near-infrared analysis indicated altered environment around the functional groups of the consisting molecules. Some of the glass-state excipient combinations protected an enzyme (lactate dehydrogenase, LDH) from inactivation during freeze-drying. The glass-state excipient combinations formed by hydrogen-bonding and electrostatic interaction network would be potent alternative to stabilize therapeutic proteins in freeze-dried formulations. PMID:19122314

Izutsu, Ken-ichi; Kadoya, Saori; Yomota, Chikako; Kawanishi, Toru; Yonemochi, Etsuo; Terada, Katsuhide

2009-01-01

206

Efficient, solventless N-Boc protection of amines carried out at room temperature using sulfamic acid as recyclable catalyst  

Microsoft Academic Search

A simple, rapid, and efficient protocol for the chemoselective N-Boc protection of amines using sulfamic acid as catalyst is described. N-Boc protection of various structurally diverse aliphatic, aromatic, alicyclic, and heterocyclic amines (1°, 2°, 3°) was carried out with (Boc)2O using sulfamic acid as catalyst (5mol%) at room temperature under solventless conditions. The advantages of this method are simplicity, shorter

Dharita J. Upadhyaya; Alessandro Barge; Rachele Stefania; Giancarlo Cravotto

2007-01-01

207

Activity and stability of non-precious metal catalysts for oxygen reduction in acid and alkaline electrolytes  

Microsoft Academic Search

The activity and stability of non-precious metal catalysts (NPMCs) for the oxygen reduction reaction (ORR) in both acid and alkaline electrolytes were studied by the rotating disk electrode technique. The NPMCs were prepared through the pyrolysis of cobalt–iron–nitrogen chelate followed by combination of pyrolysis, acid leaching, and re-pyrolysis. In both environments, the catalysts heat-treated at 800–900°C exhibited relatively high activity.

Xuguang Li; Gang Liu; Branko N. Popov

2010-01-01

208

A sulfated ZrO2 hollow nanostructure as an acid catalyst in the dehydration of fructose to 5-hydroxymethylfurfural.  

PubMed

Mesoporous hollow colloidal particles with well-defined characteristics have potential use in many applications. In liquid-phase catalysis, in particular, they can provide a large active surface area, reduced diffusion resistance, improved accessibility to reactants, and excellent dispersity in reaction media. Herein, we report the tailored synthesis of sulfated ZrO2 hollow nanostructures and their catalytic applications in the dehydration of fructose. ZrO2 hollow nanoshells with controllable thickness were first synthesized through a robust sol-gel process. Acidic functional groups were further introduced to the surface of hollow ZrO2 shells by sulfuric acid treatment followed by calcination. The resulting sulfated ZrO2 hollow particles showed advantageous properties for liquid-phase catalysis, such as well-maintained structural integrity, good dispersity, favorable mesoporosity, and a strongly acidic surface. By controlling the synthesis and calcination conditions and optimizing the properties of sulfated ZrO2 hollow shells, we have been able to design superacid catalysts with superior performance in the dehydration of fructose to 5-hydroxymethyfurfural than the solid sulfated ZrO2 nanocatalyst. PMID:24023048

Joo, Ji Bong; Vu, Austin; Zhang, Qiao; Dahl, Michael; Gu, Minfen; Zaera, Francisco; Yin, Yadong

2013-10-01

209

Low-cost catalysts for the control of indoor CO and PM emissions from solid fuel combustion.  

PubMed

Cu-Mn based mixed oxide type low-cost catalysts have been prepared in supported form using mesoporous Al(2)O(3), TiO(2) and ZrO(2) supports. These supports have been prepared by templating method using a natural biopolymer, chitosan. The synthesized catalysts have been characterized by XRD, BET-SA, SEM, O(2)-TPD and TG investigations. The catalytic activity for CO as well as PM oxidation was studied, in a view of their possible applications in the control of emissions from solid fuel combustion of rural cook-stoves. The trend observed for the catalytic activity of the synthesized catalysts for CO oxidation was ZrO(2)>TiO(2)>Al(2)O(3) while for PM oxidation it was observed to be TiO(2)>ZrO(2)>Al(2)O(3). The effect of CO(2), SO(2) and H(2)O on CO oxidation activity was also investigated, and despite partial deactivation, the catalysts show good CO oxidation activity. An effective regeneration treatment was attempted by heating the partially deactivated catalysts in presence of oxygen. Redox properties of TiO(2) and ZrO(2) and their structure appeared to be responsible for their promotional activity for CO and PM oxidation reactions. These unordered mesoporous materials could be useful for such reactions where mass transfer is more important than shape and size selectivity. PMID:21163572

Doggali, Pradeep; Kusaba, H; Einaga, H; Bensaid, S; Rayalu, S; Teraoka, Y; Labhsetwar, Nitin

2011-02-15

210

Diffusion suppression in vapor-liquid-solid Si nanowire growth by a barrier layer between the Au catalyst and substrate  

NASA Astrophysics Data System (ADS)

Nanowires have attracted significant interest because of their unique characteristics. Vapor-liquid-solid (VLS) growth is the standard method for fabricating nanowires and Au is the most commonly used catalyst. However, Au catalyst droplets diffuse over the Si substrate surface with a high migration velocity and agglomerate at relatively low temperatures. In our previous work, we reported a significant improvement in the positioning and diameter distribution of VLS-grown Si nanowires by inserting a diffusion barrier layer and concluded that the barrier layer suppressed the formation of AuSi eutectic droplets and prevented the droplets diffusing on the substrate surface during nucleation. In the present study, we analyzed the nucleation of the Au catalyst and examined its behavior during nucleation. Detailed multidirectional analysis and in situ observations confirmed that the formation and agglomeration of AuSi eutectic droplets was suppressed by the formation of a silicide layer. This because of the higher reaction temperatures between the diffusion barrier and the substrate silicon, and between the catalyst and the diffusion barrier, compared with the reaction between the Au catalyst and substrate silicon.

Koto, Makoto; Watanabe, Masatoshi; Sugawa, Etsuko; Shimizu, Tomohiro; Shingubara, Shoso

2014-10-01

211

Essential role of catalysts (Mn, Au, and Sn) in the vapor liquid solid growth kinematics of ZnS nanowires  

NASA Astrophysics Data System (ADS)

In this paper, we demonstrate that surface energy of the catalyst is a vital parameter for the growth rate, self doping of the self assembled nanowires synthesized by employing vapor liquid solid growth technique. The synthesis of ZnS nanowires was done by selectively using three different catalysts (Mn, Au, and Sn), where Au, is the most common catalyst, was used as a reference. The distinctive difference in the growth rate was due to the surface energy of the metal alloy droplet and the interface energies, as explained theoretically using thermodynamic approach. We have found that the activation energy of diffusion of (Zn, S) species in the catalyst droplet was low in Sn (0.41 eV for Zn and 0.13 eV for S) and high in Mn (1.79 eV for Zn and 0.61 eV for S) compared to Au (0.62 eV for Zn and 0.21 eV for S) catalyzed ZnS nanostructures. The thermodynamic calculations predicted the growth rates of Sn (7.5 nm/s) catalyzed nanowires was faster than Au (5.1 nm/s) and Mn (4.6 nm/s) catalyzed ZnS nanostructures, which were in agreement with the experimental results. Finally, the location of the catalyst as dopant in the grown nanostructure was predicted and compared with experimental observations.

Rehman, S.; Shehzad, M. A.; Hafeez, M.; Bhatti, A. S.

2014-01-01

212

Stability of solid oxide fuel cell anodes based on YST-SDC composite with Ni catalyst  

NASA Astrophysics Data System (ADS)

Ceramic material based on composite of yttria-doped SrTiO3 (YST) and samaria-doped ceria (SDC) incorporated with Ni catalyst has been evaluated as an anode of solid oxide fuel cell to substitute the use of conventional Ni-based cermets. The results indicated the advantages of suitable Ni addition which could remarkably enhance the electrochemical performance of anode due to the superior in catalytic activity of SDC and Ni towards fuel oxidation. Temperature-programmed reduction (TPR) profiles indicated the existence of bulk-free and interacted NiO in the composites. The cells with Ni/YST-SDC (20 wt% NiO) anodes exhibited stable performance in the prolong operation with tremendously severe conditions in methane fuel with low steam to carbon ratio (S/C = 0.1) and highly humidified hydrogen fuel (40% H2O-H2) compared with the conventional Ni-based cermets. Small amount of deposited carbon was observed and played insignificant effects on the electrochemical performance after the operation for 100 h. The stable performance was ascribable to the excellence in YST-SDC ceramic framework that effectively suppressed the carbon formation. Furthermore, the Ni/YST-SDC anode showed high tolerance in encountering with the redox cycles. From these results, Ni/YST-SDC composite is considered to be a promising candidate for SOFC anode material operating in severe conditions.

Puengjinda, Pramote; Muroyama, Hiroki; Matsui, Toshiaki; Eguchi, Koichi

2012-10-01

213

Revealing the dynamic structure of complex solid catalysts using modulated excitation X-ray diffraction.  

PubMed

X-ray diffraction (XRD) is typically silent towards information on low loadings of precious metals on solid catalysts because of their finely dispersed nature. When combined with a concentration modulation approach, time-resolved high-energy XRD is able to provide the detailed redox dynamics of palladium nanoparticles with a diameter of 2?nm in 2?wt?% Pd/CZ (CZ = ceria-zirconia), which is a difficult sample for extended X-ray absorption fine structure (EXAFS) measurements because of the cerium component. The temporal evolution of the Pd(111) and Ce(111) reflections together with surface information from synchronous diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements reveals that Ce maintains Pd oxidized in the CO pulse, whereas reduction is detected at the beginning of the O2 pulse. Oxygen is likely transferred from Pd to Ce(3+) before the onset of Pd re-oxidation. In this context, adsorbed carbonates appear to be the rate-limiting species for re-oxidation. PMID:24903631

Ferri, Davide; Newton, Mark A; Di Michiel, Marco; Chiarello, Gian Luca; Yoon, Songhak; Lu, Ye; Andrieux, Jérôme

2014-08-18

214

Solid–liquid equilibrium in the acetic acid–acetophenone and acetic acid–formamide systems  

Microsoft Academic Search

Solid–liquid equilibrium in the binary systems acetic acid–acetophenone and acetic acid–formamide was determined from time–temperature cooling and warming curves. The first system shows a sagged curve with a eutectic point at x1?0.6 and T=267.18 K. In the second system a solid compound (2:1) was found and an equilibrium constant of the compound dissociation was calculated.

I. Malijevská; Z. Sedláková

2006-01-01

215

?-linolenic acid production by Cunninghamella japonica in solid state fermentation  

Microsoft Academic Search

The production of lipid and ?-linolenic acid (GLA) by Cunninghamella japonica was studied in solid state fermentations (SSF) on cereal substrates. A number of cereals were used as sources of nutrients for fungal SSF and the substrate which favoured the highest accumulation of lipid and GLA in fermented substrate was determined. The treatment of cereals, addition of nutrients to the

Elena V. Emelyanova

1996-01-01

216

Arachidonic acid production by Mortierella alpina grown on solid substrates  

Microsoft Academic Search

Mortierella alpina grown in solid state fermentations on cereal substrates gave up to 16% lipid in the final biomass. Arachidonic was at 50% of total fatty acids, with a yield of 36 mg\\/g of original substrate. Microbial lipid production was successfully scaled up to use 5-kg dry substrate batches.

S. Stred'anská; D. Slugeti; M. Stred'anský; J. Grego

1993-01-01

217

Transesterification of soybean oil catalyzed by fly ash and egg shell derived solid catalysts  

Microsoft Academic Search

A fly ash supported heterogeneous CaO catalyst has been developed using waste egg shell for transesterification of soybean oil to yield fuel grade biodiesel. The active metal precursor Ca(OH)2 of the catalyst has been economically derived from waste egg shell calcination and the mesoporous, high activity strong base catalyst has been prepared using wet-impregnation method. X-ray diffraction (XRD), scanning electron

R. Chakraborty; S. Bepari; A. Banerjee

2010-01-01

218

Highly efficient Brønsted acidic ionic liquid-based catalysts for biodiesel synthesis from vegetable oils.  

PubMed

Biodiesel has been produced by transesterification of canola oil with methanol in the presence of highly Brønsted acidic ionic liquids based on 1-benzyl-1H-benzimidazole, and the effect of reaction temperature, type and amount of catalyst, molar ratio and reaction time investigated. The results show that the 4B ionic liquid has the highest catalytic activity and best recyclability under the optimised reaction conditions. Thus, this ionic liquid is able to catalyze the transesterification of canola oil to its methyl esters in 5 h with yields of more than 95%. Density functional calculations (B3LYP), using the 6-311G basis set, have been performed to have a better understanding on the reactivity of these catalysts. The catalytic activity of 4B for the transesterification of other vegetable oils and alcohols has also been studied. PMID:20970994

Ghiaci, M; Aghabarari, B; Habibollahi, S; Gil, A

2011-01-01

219

Polystyrene sulphonic acid resins with enhanced acid strength via macromolecular self-assembly within confined nanospace  

NASA Astrophysics Data System (ADS)

Tightening environmental legislation is driving the chemical industries to develop efficient solid acid catalysts to replace conventional mineral acids. Polystyrene sulphonic acid resins, as some of the most important solid acid catalysts, have been widely studied. However, the influence of the morphology on their acid strength—closely related to the catalytic activity—has seldom been reported. Herein, we demonstrate that the acid strength of polystyrene sulphonic acid resins can be adjusted through their reversible morphology transformation from aggregated to swelling state, mainly driven by the formation and breakage of hydrogen bond interactions among adjacent sulphonic acid groups within the confined nanospace of hollow silica nanospheres. The hybrid solid acid catalyst demonstrates high activity and selectivity in a series of important acid-catalysed reactions. This may offer an efficient strategy to fabricate hybrid solid acid catalysts for green chemical processes.

Zhang, Xiaomin; Zhao, Yaopeng; Xu, Shutao; Yang, Yan; Liu, Jia; Wei, Yingxu; Yang, Qihua

2014-01-01

220

Acid zeolites as alcohol racemization catalysts: screening and application in biphasic dynamic kinetic resolution.  

PubMed

Acid zeolites were screened as heterogeneous catalysts for racemization of benzylic alcohols. The most promising zeolites appeared to be H-Beta zeolites, for which the optimal reaction conditions were studied in further detail. The zeolite performance was compared to that of homogeneous acids and acid resins under similar reaction conditions. In a second part of the research, H-Beta zeolites were applied in dynamic kinetic resolution (DKR) of 1-phenylethanol, which was conducted by means of a two-phase approach and which resulted in yields smoothly crossing the 50% border up to 90%, with an enantiomeric excess of >99%. To explore the applicability of this biphasic methodology, several other substrates were examined in the standard racemization reaction and in the biphasic dynamic kinetic resolution. PMID:15565578

Wuyts, S; De Temmerman, K; De Vos, D E; Jacobs, P A

2004-12-17

221

Lactic acid conversion to 2,3-pentanedione and acrylic acid over silica-supported sodium nitrate: Reaction optimization and identification of sodium lactate as the active catalyst  

SciTech Connect

Lactic acid is converted to 2,3-pentanedione, acrylic acid, and other products in vapor-phase reactions over silica-supported sodium lactate formed from sodium nitrate. Multiparameter optimization of reaction conditions using a Box-Benkhen experimental design shows that the highest yield and selectivity to 2,3-pentanedione are achieved at low temperature, elevated pressure, and long contact time, while yield and selectivity to acrylic acid are most favorable at high temperature, low pressure, and short contact time. Post-reaction Fourier transform infrared spectroscopic analyses of the catalyst indicate that sodium nitrate as the initial catalyst material is transformed to sodium lactate at the onset of reaction via proton transfer from lactic acid to nitrate. The resultant nitric acid vaporizes as it is formed, leaving sodium lactate as the sole sodium-bearing species on the catalyst during reaction. 19 refs., 8 figs., 5 tabs.

Wadley, D.C.; Tam, M.S.; Miller, D.J. [Michigan State Univ., East Lansing, MI (United States)] [and others] [Michigan State Univ., East Lansing, MI (United States); and others

1997-01-15

222

Isoselenazolones as catalysts for the activation of bromine: bromolactonization of alkenoic acids and oxidation of alcohols.  

PubMed

Isoselenazolones were synthesized by a copper-catalyzed Se-N bond forming reaction between 2-halobenzamides and selenium powder. The catalytic activity of the various isoselenazolones was studied in the bromolactonization of pent-4-enoic acid. Isoselenazolone 9 was studied as a catalyst in several reactions: the bromolactonization of a series of alkenoic acids with bromine or N-bromosuccinimide (NBS) in the presence of potassium carbonate as base, the bromoesterification of a series of alkenes using NBS and a variety of carboxylic acids, and the oxidation of secondary alcohols to ketones using bromine as an oxidizing reagent. Mechanistic details of the isoselenazolone-catalyzed bromination reaction were revealed by (77)Se NMR spectroscopic and ES-MS studies. The oxidative addition of bromine to the isoselenazolone gives the isoselenazolone(IV) dibromide, which could be responsible for the activation of bromine under the reaction conditions. Steric effects from an N-phenylethyl group on the amide of the isoselenazolone and electron-withdrawing fluoro substituents on the benzo fused-ring of the isoselenazolone appear to enhance the stability of the isoselenazolone as a catalyst for the bromination reaction. PMID:23046286

Balkrishna, Shah Jaimin; Prasad, Ch Durga; Panini, Piyush; Detty, Michael R; Chopra, Deepak; Kumar, Sangit

2012-11-01

223

Photodegradation of nalidixic acid assisted by TiO(2) nanorods/Ag nanoparticles based catalyst.  

PubMed

Two different nanosized TiO2-based catalysts supported onto glass with tailored photocatalytic properties upon irradiation by UV light were successfully employed for the degradation of nalidixid acid, a widely diffused antibacterial agent of environmental relevance known to be non-biodegradable. Anatase rod-like TiO2 nanocrystals (TiO2NRs) and a semiconductor oxide-noble metal nanocomposite TiO2 NRs/Ag nanoparticles (NPs), synthesized by colloidal chemistry routes, were cast onto glass slide and employed as photocatalysts. A commercially available catalyst (TiO2 P25), also immobilized onto a glass slide, was used as a reference material. It was found that both TiO2 NRs/Ag NPs composite and TiO2 NRs demonstrated a photocatalytic efficiency significantly higher than the reference TiO2 P25. Specifically, TiO2 NRs/Ag NPs showed a photoactivity in nalidixic acid degradation 14 times higher than TiO2 P25 and 4 times higher than bare TiO2 NRs in the first 60min of reaction. Several by-products were identified by HPLC-MS along the nalidixic acid degradation, thus getting useful insight on the degradation pathway. All the identified by-products resulted completely removed after 6h of reaction. PMID:23466278

Petronella, F; Diomede, S; Fanizza, E; Mascolo, G; Sibillano, T; Agostiano, A; Curri, M L; Comparelli, R

2013-05-01

224

Enhanced catalytic performance of Pd catalyst for formic acid electrooxidation in ionic liquid aqueous solution  

NASA Astrophysics Data System (ADS)

A protic ionic liquid (IL), n-butylammonium nitrate (N4NO3), is prepared and employed as the electrolyte for formic acid electrooxidation reaction (FAOR) on Pd catalysts. The oxidation peak potential of FAOR in the IL solution shows about a 200 mV negative shift as compared with those in traditional H2SO4/HClO4 electrolytes, suggesting that FAOR can be more easily carried out on Pd catalysts in IL media. The catalytic properties of Pd toward FAOR are not only dependent on the concentration of IL, as a consequence of the varied electronic conductivity of the IL solution, but also on the high potential limit of the cyclic voltammograms. When the Pd catalyst is cycled up to 1.0 V (vs. SCE), which induces a significant oxidation of Pd, it shows ca. 4.0 times higher activity than that not subjected to the Pd oxidation (up to 0.6 V). The Pd oxides, which are more easily formed in IL solution than in traditional H2SO4/HClO4 electrolytes, may play a crucial role in increasing the catalytic activities of Pd toward FAOR. Our work would shed new light on the mechanism of FAOR and highlight the potential applications of IL as green and environment-friendly electrolytes in fuel cells and other technologies.

Feng, Yuan-Yuan; Yin, Qian-Ying; Lu, Guo-Ping; Yang, Hai-Fang; Zhu, Xiao; Kong, De-Sheng; You, Jin-Mao

2014-12-01

225

Catalytic Friedel-Crafts acylation of benzene, chlorobenzene, and fluorobenzene using a novel catalyst system, hafnium triflate and trifluoromethanesulfonic acid  

Microsoft Academic Search

Catalytic Friedel-Crafts acylation of benzene and unactivated benzenes such as chlorobenzene and fluorobenzene has been successfully carried out using hafnium (IV) triflate and trifluoromethanesulfonic acid as catalysts. Both aromatic and aliphatic carboxylic acid chlorides reacted smoothly under the conditions to afford the corresponding aromatic ketones in good yields.

Sh? Kobayashi; Shunsuke Iwamoto

1998-01-01

226

Indium metal-organic frameworks as high-performance heterogeneous catalysts for the synthesis of amino Acid derivatives.  

PubMed

Indium metal-organic frameworks (MOFs) were first used as recyclable heterogeneous Lewis acid catalysts for the synthesis of amino acid derivatives with excellent conversion yields. Moreover, exposed ether groups (Lewis basic sites) on the pore walls of In-MOF 2 could activate trimethylsilyl cyanide, forming hypervalent silicate intermediates, as proven by (29)Si NMR. PMID:25244398

Xia, Jing; Xu, Jianing; Fan, Yong; Song, Tianyou; Wang, Li; Zheng, Jifu

2014-10-01

227

A facile approach for the preparation of tunable acid nano-catalysts with a hierarchically mesoporous structure.  

PubMed

A facile and efficient approach to prepare hierarchically and radially mesoporous nano-catalysts with tunable acidic properties has been successfully developed. The nanospheres show excellent catalytic performance for the acid catalysed reactions, i.e. cracking of 1,3,5-triisopropylbenzene and hydrolysis of sucrose. PMID:24898618

Choi, Youngbo; Yun, Yang Sik; Park, Hongseok; Park, Dae Sung; Yun, Danim; Yi, Jongheop

2014-07-21

228

A novel catalyst of Fe-octacarboxylic acid phthalocyanine supported by attapulgite for degradation of Rhodamine B  

SciTech Connect

A novel nano-composite catalyst was prepared from immobilization of Fe-octacarboxylic acid phthalocyanine onto the supporting material attapulgite. The morphology and structure of the catalyst were analyzed by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared and ultraviolet-visible spectroscopy. The catalyst activity was examined through comparative experiments, and results showed that it exhibited high activity for degradation of Rhodamine B in the presence of hydrogen peroxide. The recycling test was also carried out to prove its reusability in catalytic application.

Fang, Ying [State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Shanghai 201620 (China) [State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Shanghai 201620 (China); College of Materials Science and Engineering, Donghua University, Shanghai 201620 (China); Chen, Dajun, E-mail: cdj@dhu.edu.cn [State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Shanghai 201620 (China) [State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Shanghai 201620 (China); College of Materials Science and Engineering, Donghua University, Shanghai 201620 (China)

2010-11-15

229

Ionic and covalent stabilization of intermediates and transition States in catalysis by solid acids.  

PubMed

Reactivity descriptors describe catalyst properties that determine the stability of kinetically relevant transition states and adsorbed intermediates. Theoretical descriptors, such as deprotonation energies (DPE), rigorously account for Brønsted acid strength for catalytic solids with known structure. Here, mechanistic interpretations of methanol dehydration turnover rates are used to assess how charge reorganization (covalency) and electrostatic interactions determine DPE and how such interactions are recovered when intermediates and transition states interact with the conjugate anion in W and Mo polyoxometalate (POM) clusters and gaseous mineral acids. Turnover rates are lower and kinetically relevant species are less stable on Mo than W POM clusters with similar acid strength, and such species are more stable on mineral acids than that predicted from W-POM DPE-reactivity trends, indicating that DPE and acid strength are essential but incomplete reactivity descriptors. Born-Haber thermochemical cycles indicate that these differences reflect more effective charge reorganization upon deprotonation of Mo than W POM clusters and the much weaker reorganization in mineral acids. Such covalency is disrupted upon deprotonation but cannot be recovered fully upon formation of ion pairs at transition states. Predictive descriptors of reactivity for general classes of acids thus require separate assessments of the covalent and ionic DPE components. Here, we describe methods to estimate electrostatic interactions, which, taken together with energies derived from density functional theory, give the covalent and ionic energy components of protons, intermediates, and transition states. In doing so, we provide a framework to predict the reactive properties of protons for chemical reactions mediated by ion-pair transition states. PMID:25333244

Deshlahra, Prashant; Carr, Robert T; Iglesia, Enrique

2014-10-29

230

Thermal stability, acidity, catalytic properties, and deactivation behaviour of SAPO-5 catalysts: Effect of silicon content, acid treatment, and Na exchange  

SciTech Connect

Crystalline microporous SAPO-5 molecular sieves with different silicon content, acid-treated SAPO-5 and Na-exchanged SAPO-5 were investigated for their thermal stability, and acidic and catalytic properties. SAPO-5 materials with increasing SI framework content exhibited lower thermal stability. The effects of the thermal treatment and Na exchange on the N{sub 2}-sorption capacity (at 78 K) of these materials were studied. In situ IR spectroscopic investigations of pyridine chemisorbed on the aluminophosphate catalysts revealed that the concentration of Broensted and Lewis acid sites are strongly affected by the Si content in the AlPO{sub 4} framework, acid treatment, and Na exchange. The results of temperature programmed desorption (TPD) and stepwise thermal desorption of pyridine suggest that there exists a broad site energy distribution over the aluminophosphate catalysts increases with the increasing Si content in the AlPO{sub 4} framework. The acid treatment and Na exchange showed a decrease in the number of strong acid sites on SAPO-5. The TPD of pyridine over SAPO-5, acid-treated SAPO-5, and Na-exchanged SAPO-5 indicated the presence of two types of acid sites. Correlation between the number of strong acid sites (measured in terms of the chemisorption of pyridine at 673 K) and framework charge on the aluminophosphate catalysts has also been obtained. The catalytic activities of SAPO-5 catalysts in the ethanol, n-hexane, isooctane, toluene, and o-xylene conversion reactions were studied. 22 refs., 11 figs., 5 tabs.

Akolekar, D.B. [Univ. of New South Wales, Kensington (Australia)] [Univ. of New South Wales, Kensington (Australia)

1994-09-01

231

FT-IR and solid-state NMR investigation of phosphorus promoted hydrotreating catalyst precursors  

SciTech Connect

The effect of phosphorus on the structure of Ni-Mo/Al{sub 2}O{sub 3} hydrotreating catalyst precursors has been investigated. Calcined and reduced P/Al{sub 2}O{sub 3}, P-Ni/Al{sub 2}O{sub 3}, P-Mo/Al{sub 2}O{sub 3}, and P-Ni-Mo/Al{sub 2}O{sub 3} (where the wt% P = 0.0 to 10.0 wt % Mo = 8.0 to 12.0, and wt% Ni = 4.0) have been studied using FT-IR, XRD, and {sup 27}Al MAS NMR techniques. Phosphoric acid reacts with alumina hydroxyls forming monomeric and polymeric phosphates. At the higher phosphorus loadings, aluminum phosphate is also formed. On calcined P-Ni/Al{sub 2}O{sub 3}, nickel phosphate is formed. This leads to a decrease in density of Ni{sub 0} sites in the reduced state as measured by CO adsorption. The addition of up to 1.5 wt% P to Mo(8)/Al{sub 2}O{sub 3} promotes the formation of octahedral molybdena on the alumina surface. However, the addition of > 2.0 wt% P results in the formation of bulk MoO{sub 3} and Al{sub 2}(MoO{sub 4}){sub 3} in both P-Mo(8)/Al{sub 2}O{sub 3} and P-Mo(12)/Al{sub 2}O{sub 3}. CO adsorption on reduced P-Ni(4)-Mo(8)/Al{sub 2}O{sub 3} samples shows that the presence of 0.5 wt% P causes a significant increase in the number of sites adsorbing CO. Increasing the P loading further causes a decrease in the number of adsorbing sites; this decrease can be attributed to the formation of either nickel phosphate or nickel molybdate.

DeCanio, E.C.; Edwards, J.C.; Scalzo, T.R.; Storm, D.A. (Texaco Inc., Beacon, NY (United States)) Bruno, J.W. (Wesleyan Univ., Middletown, CT (United States))

1991-12-01

232

Sustainable solid catalyst alkylation of commercial olefins by regeneration with supercritical isobutane  

SciTech Connect

Supercritical isobutane regeneration of a USY zeolite alkylation catalyst was examined in a continuous, automated reaction / regeneration system. Two feeds were studied; a synthetic isobutane / 2-butene blend, and a commercial refinery isoparaffin / olefin blend. The refinery blend was minimally treated, containing a variety of light olefins, and contaminants, including butadiene, oxygenates and sulfur, which are well known to cause severe catalyst deactivation. Synthetic feed experiments showed that high levels of butene conversion was maintained for more than 200 hours time on stream, and that product quality and catalyst maintenance was relatively stable over the course of the experiment using a 3 hour reaction / 3 hour regeneration cycle. Catalyst activity maintenance was lower when the commercial feed was employed. High levels of alkene conversion were maintained for 78 hours and 192 hours using a 3 hour reaction / 3 hour regeneration cycle and a 2 hour reaction / 2 hour regeneration cycle, respectively.

Daniel M. Ginosar; David N. Thompson; Kyle C. Burch

2005-12-01

233

Acid sites and oxidation center in molybdena supported on tin oxide as studied by solid-state NMR spectroscopy and theoretical calculation.  

PubMed

Solid-state NMR spectroscopy and density functional theory (DFT) calculations were employed to study the structure and properties, especially the solid acidity, of molybdenum oxide supported on tin oxide. As demonstrated by solid-state NMR experiments, Mo species are mainly dispersed on the surface of SnO(2) support rather than significantly dissolved into the SnO(2) structure and Brønsted as well as Lewis acid sites are present on the MoO(3)/SnO(2) catalyst. Acid strength of the supported metal oxide is stronger than those of zeolites, e.g., HY and HZSM-5, though the concentration of acid sites is relatively lower. The DFT calculated (13)C chemical shift for acetone adsorbed on MoO(3)/SnO(2) is in good agreement with the experimental value, which confirms our proposed structure of -Mo-(OH)-Sn- for the Brønsted acid site. Reducibility of the supported metal oxide is also demonstrated by solid-state NMR experiments and an active oxidation center of this catalyst is proposed as well. PMID:16710485

Wang, Jiqing; Su, Yongchao; Xu, Jun; Ye, Chaohui; Deng, Feng

2006-05-28

234

Fluoroponytailed crown ethers and quaternary ammonium salts as solid-liquid phase transfer catalysts in organic synthesis.  

PubMed

Fluorous derivatives of dibenzo-18-crown-6 ether were prepared, and then successfully applied in representative solid-liquid phase transfer catalysis reactions, which were performed in standard organic solvents, such as chlorobenzene and toluene, as well as in fluorous solvents, such as perfluoro-1,3-dimethylcyclohexane. It was clearly shown that properly designed fluoroponytailed crown ethers could promote the disintegration of the crystal lattice of alkali salts, and transfer anions from the solid surface into an apolar, non-coordinating perfluorocarbon phase, for phase transfer catalysis reactions in organic synthesis. Furthermore, 3,5-bis(perfluorooctyl)benzyl bromide and triethylamine were reacted under mild conditions to provide an analogue of the versatile phase transfer catalyst, benzyltriethylammonium chloride, containing two fluoroponytails. This fluoroponytailed quaternary ammonium salt was also successfully employed as a catalyst in a variety of organic reactions conducted under solid-liquid phase transfer catalysis conditions, without a perfluorocarbon phase. Thus, being both hydrophobic and lipophobic, fluorous crown ethers and ammonium salts, could be rapidly recovered in quantitative yields, and reused without loss of activity, over several reaction cycles. PMID:21928010

Pozzi, Gianluca; Fish, Richard H

2012-01-01

235

From molecular complexes to complex metallic nanostructures--2H solid-state NMR studies of ruthenium-containing hydrogenation catalysts.  

PubMed

In the last years, the combination of (2)H solid-state NMR techniques with quantum-chemical calculations has evolved into a powerful spectroscopic tool for the characterization of the state of hydrogen on the surfaces of heterogeneous catalysts. In the present minireview, a brief summary of this development is given, in which investigations of the structure and dynamics of hydrogen in molecular complexes, clusters and nanoparticle systems are presented, aimed to understand the reaction mechanisms on the surface of hydrogenation catalysts. The surface state of deuterium/hydrogen is analyzed employing a combination of variable-temperature (2)H static and magic-angle spinning (MAS) solid-state NMR techniques, in which the dominant quadrupolar interactions of deuterium give information on the binding situation and local symmetry of deuterium/hydrogen on molecular species. Using a correlation database from molecular complexes and clusters, the possibility to distinguish between terminal Ru-D, bridged Ru2-D, three-fold Ru3-D, and interstitial Ru6-D is demonstrated. Combining these results with quantum-chemical density functional theory (DFT) calculations allows the interpretation of (2)H solid-state data of complex "real world" nanostructures, which yielded new insights into reaction pathways at the molecular level. PMID:23658058

Gutmann, Torsten; del Rosal, Iker; Chaudret, Bruno; Poteau, Romuald; Limbach, Hans-Heinrich; Buntkowsky, Gerd

2013-09-16

236

Insights into the interplay of Lewis and Brønsted acid catalysts in glucose and fructose conversion to 5-(hydroxymethyl)furfural and levulinic acid in aqueous media.  

PubMed

5-(Hydroxymethyl)furfural (HMF) and levulinic acid production from glucose in a cascade of reactions using a Lewis acid (CrCl3) catalyst together with a Brønsted acid (HCl) catalyst in aqueous media is investigated. It is shown that CrCl3 is an active Lewis acid catalyst in glucose isomerization to fructose, and the combined Lewis and Brønsted acid catalysts perform the isomerization and dehydration/rehydration reactions. A CrCl3 speciation model in conjunction with kinetics results indicates that the hydrolyzed Cr(III) complex [Cr(H2O)5OH](2+) is the most active Cr species in glucose isomerization and probably acts as a Lewis acid-Brønsted base bifunctional site. Extended X-ray absorption fine structure spectroscopy and Car-Parrinello molecular dynamics simulations indicate a strong interaction between the Cr cation and the glucose molecule whereby some water molecules are displaced from the first coordination sphere of Cr by the glucose to enable ring-opening and isomerization of glucose. Additionally, complex interactions between the two catalysts are revealed: Brønsted acidity retards aldose-to-ketose isomerization by decreasing the equilibrium concentration of [Cr(H2O)5OH](2+). In contrast, Lewis acidity increases the overall rate of consumption of fructose and HMF compared to Brønsted acid catalysis by promoting side reactions. Even in the absence of HCl, hydrolysis of Cr(III) decreases the solution pH, and this intrinsic Brønsted acidity drives the dehydration and rehydration reactions. Yields of 46% levulinic acid in a single phase and 59% HMF in a biphasic system have been achieved at moderate temperatures by combining CrCl3 and HCl. PMID:23432136

Choudhary, Vinit; Mushrif, Samir H; Ho, Christopher; Anderko, Andrzej; Nikolakis, Vladimiros; Marinkovic, Nebojsa S; Frenkel, Anatoly I; Sandler, Stanley I; Vlachos, Dionisios G

2013-03-13

237

Continuous esterification of free Fatty acids in crude biodiesel by an integrated process of supercritical methanol and sodium methoxide catalyst.  

PubMed

An integrated process of supercritical methanol (SCM) and sodium methoxide catalyst was developed to produce fatty acid methyl esters (FAMEs) via continuous esterification from crude biodiesel. The crude biodiesel with high free fatty acid (FFA) content must be refined to reduce the acid value (AV) for meeting the quality standards. The process parameters were studied by Box-Behnken design (BBD) of response surface methodology (RSM). The experimental results revealed that the AV of crude biodiesel decreased from 18.66 to 0.55 mg KOH g(-1) at the reaction conditions of 350 °C, 0.5 % amount of sodium methoxide catalyst, and 10 MPa. Temperature shows the most significant effect on the esterification, followed by pressure and amount of sodium methoxide catalyst. This integrated process proved to be a potential route to refine the crude biodiesel because of its continuity, high efficiency, and less energy consumption with relatively moderate reaction conditions compared with conventional methods. PMID:25119550

Zeng, Dan; Li, Ruosong; Feng, Mingjun; Fang, Tao

2014-10-01

238

Porosity and surface area of monolithic carbon aerogels prepared using alkaline carbonates and organic acids as polymerization catalysts  

Microsoft Academic Search

Carbon aerogels were prepared by polymerization of a resorcinol–formaldehyde mixture using different polymerization catalysts such as: sodium or potassium carbonates, oxalic acid or para-toluenesulfonic acid. The carbon aerogel obtained with this last acid was further CO2-activated to 8.5% and 22% burn-off. All samples were characterized by N2 and CO2 adsorption at ?196 and 0°C, respectively, and by mercury porosimetry, scanning

D. Fairén-Jiménez; F. Carrasco-Marín; C. Moreno-Castilla

2006-01-01

239

Catalytic pyrolysis of oil fractions separated from food waste leachate over nanoporous acid catalysts.  

PubMed

Oil fractions, separated from food waste leachate, can be used as an energy source. Especially, high quality oil can be obtained by catalytic cracking. In this study, nanoporous catalysts such as Al-MCM-41 and mesoporous MFI type zeolite were applied to the catalytic cracking of oil fractions using the pyrolysis gas chromatography/mass spectrometry. Mesoporous MFI type zeolite showed better textural porosity than Al-MCM-41. In addition, mesoporous MFI type zeolite had strong Brönsted acidity while Al-MCM-41 had weak acidity. Significant amount of acid components in the food waste oil fractions were converted to mainly oxygenates and aromatics. As a result of its well-defined nanopores and strong acidity, the use of a mesoporous MFI type zeolite produced large amounts of gaseous and aromatic compounds. High yields of hydrocarbons within the gasoline range were also obtained in the case of mesoporous MFI type zeolite, whereas the use of Al-MCM-41, which exhibits relatively weak acidity, resulted in high yields of oxygenates and diesel range hydrocarbons. PMID:22121679

Kim, Seung-Soo; Heo, Hyeon Su; Kim, Sang Guk; Ryoo, Ryong; Kim, Jeongnam; Jeon, Jong-Ki; Park, Sung Hoon; Park, Young-Kwon

2011-07-01

240

Approaches to mitigate metal catalyst deactivation in solid oxide fuel cell (SOFC) fuel electrodes  

NASA Astrophysics Data System (ADS)

While Ni/YSZ cermets have been used successfully in SOFCs, they also have several limitations, thus motivating the use of highly conductive ceramics to replace the Ni components in SOFC anodes. Ceramic electrodes are promising for use in SOFC anodes because they are expected to be less susceptible to sintering and coking, be redox stable, and be more tolerant of impurities like sulfur. In this thesis, for catalytic studies, the infiltration procedure has been used to form composites which have greatly simplified the search for the best ceramics for anode applications. In the development of ceramic fuel electrodes for SOFC, high performance can only be achieved when a transition metal catalyst is added. Because of the high operating temperatures, deactivation of the metal catalyst by sintering and/or coking is a severe problem. In this thesis, two approaches aimed at mitigating metal catalyst deactivation which was achieved by: 1) designing a catalyst that is resistant to coking and sintering and 2) developing a new method for catalyst deposition, will be presented. The first approach involved synthesizing a self-regenerating, "smart" catalyst, in which Co, Cu, or Ni were inserted into the B-site of a perovskite oxide under oxidizing conditions and then brought back to the surface under reducing conditions. This restores lost surface area of sintered metal particles through an oxidation/reduction cycle. Results will be shown for each of the metals, as well as for Cu-Co mixed metal systems, which are found to exhibit good tolerance to carbon deposition and interesting catalytic properties. The second strategy involves depositing novel Pd CeO2 core-shell nanostructure catalysts onto a substrate surface which had been chemically modified to anchor the nanoparticles. The catalyst deposited onto the chemically modified, hydrophobic surface is shown to be uniform and well dispersed, and exhibit excellent thermal stability to temperatures as high as 1373 K. Similar metal catalyst deposition method was also employed to access their suitability for use in SOFC anodes.

Adijanto, Lawrence

241

Three-phase catalytic system of H2O, ionic liquid, and VOPO4-SiO2 solid acid for conversion of fructose to 5-hydroxymethylfurfural.  

PubMed

Efficient transformation of biomass-derived feedstocks to chemicals and fuels remains a daunting challenge in utilizing biomass as alternatives to fossil resources. A three-phase catalytic system, consisting of an aqueous phase, a hydrophobic ionic-liquid phase, and a solid-acid catalyst phase of nanostructured vanadium phosphate and mesostructured cellular foam (VPO-MCF), is developed for efficient conversion of biomass-derived fructose to 5-hydroxymethylfurfural (HMF). HMF is a promising, versatile building block for production of value-added chemicals and transportation fuels. The essence of this three-phase system lies in enabling the isolation of the solid-acid catalyst from the aqueous phase and regulation of its local environment by using a hydrophobic ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][Tf2N]). This system significantly inhibits the side reactions of HMF with H2O and leads to 91?mol?% selectivity to HMF at 89?% of fructose conversion. The unique three-phase catalytic system opens up an alternative avenue for making solid-acid catalyst systems with controlled and locally regulated microenvironment near catalytically active sites by using a hydrophobic ionic liquid. PMID:24729382

Tian, Chengcheng; Zhu, Xiang; Chai, Song-Hai; Wu, Zili; Binder, Andrew; Brown, Suree; Li, Lin; Luo, Huimin; Guo, Yanglong; Dai, Sheng

2014-06-01

242

A Brønsted acidic ionic liquid as an efficient and environmentally benign catalyst for biodiesel synthesis from free fatty acids and alcohols.  

PubMed

Biodiesel could be synthesized using Brønsted acidic ionic liquid N-methyl-2-pyrrolidonium methyl sulfonate ([NMP][CH(3)SO(3)]) as a catalyst, specially with free long-chain fatty acids or their mixtures, as well as with low-molecular weight alcohols as substrates. This catalyst showed good catalytic and reusable performance under mild conditions and without any additional organic solvent. The ionic liquid could be reused eight times after the water in the ionic liquid was removed. The yields of fatty acid alkyl esters could reach between 93.6% and 95.3% after the esterifications were carried out at 70 degrees C for 8h. Therefore, an efficient and environmentally friendly catalyst was provided for the synthesis of biodiesel from low-cost feedstocks such as waste oils. PMID:19427782

Zhang, Lei; Xian, Mo; He, Yucai; Li, Liangzhi; Yang, Jianming; Yu, Shitao; Xu, Xin

2009-10-01

243

Production of biodiesel from mixed waste vegetable oil using an aluminium hydrogen sulphate as a heterogeneous acid catalyst.  

PubMed

Al(HSO(4))(3) heterogeneous acid catalyst was prepared by the sulfonation of anhydrous AlCl(3). This catalyst was employed to catalyze transesterification reaction to synthesis methyl ester when a mixed waste vegetable oil was used as feedstock. The physical and chemical properties of aluminum hydrogen sulphate catalyst were characterized by scanning electron microscopy (SEM) measurements, energy dispersive X-ray (EDAX) analysis and titration method. The maximum conversion of triglyceride was achieved as 81 wt.% with 50 min reaction time at 220°C, 16:1 molar ratio of methanol to oil and 0.5 wt.% of catalyst. The high catalytic activity and stability of this catalyst was related to its high acid site density (-OH, Brönsted acid sites), hydrophobicity that prevented the hydration of -OH group, hydrophilic functional groups (-SO(3)H) that gave improved accessibility of methanol to the triglyceride. The fuel properties of methyl ester were analyzed. The fuel properties were found to be observed within the limits of ASTM D6751. PMID:21621409

Ramachandran, Kasirajan; Sivakumar, Pandian; Suganya, Tamilarasan; Renganathan, Sahadevan

2011-08-01

244

Catalyst Activity and Post-operation Analyses of Pt/TiO2 (Rutile) Catalysts Used in the Sulfuric Acid Decomposition Reaction  

SciTech Connect

Production of hydrogen by splitting of water at lower temperatures than by direct thermal decomposition can be achieved by a series of particular chemical reactions that establish a thermochemical cycle [1]. Among the high number of thermochemical water-splitting cycles proposed in the literature [2], the sulfur-based group is of considerable interest. All the sulfur-based cycles employ the catalytic decomposition of sulfuric acid into SO2 and O2. The produced O2 corresponds to the O2 generated from water in the overall cycle. Research performed at the Idaho National Laboratory [3] has found that even one of the most stables catalysts, Pt supported on low surface area titania, deactivates with time on stream (TOS). To develop an understanding of the factors that cause catalyst deactivation, samples of 1% Pt supported on titania (rutile) catalyst were submitted to flowing concentrated sulfuric acid at 1123 K and atmospheric pressure for different TOSs between 0 and 548 h and a number of chemical and spectroscopic analyses applied to the spent samples.

Lucia M. Petkovic; Daniel M. Ginosar; Harry W. Rollins; Kyle C. Burch; Patrick J. Pinhero; Helen H. Farrell

2007-06-01

245

Silica-bonded N-propyl sulfamic acid used as a heterogeneous catalyst for transesterification of soybean oil with methanol.  

PubMed

The transesterification of soybean oil with methanol was carried out, to produce biodiesel, over silica-bonded N-propyl sulfamic acid in a heterogeneous manner. Results showed that a maximum conversion of 90.5% was achieved using a 1:20 M ratio of soybean oil to methanol and a catalyst amount of 7.5 wt.% at 423 K for 60 h. It was found that the free fatty acid (FFA) and water present in the feedstock had no significant influence on the catalytic activity to the transesterification reaction. Besides, the catalyst also showed activities towards the esterification reaction of FFAs, in terms of the FFA conversion of 95.6% at 423 K for 30 h. Furthermore, the catalyst could be recovered with a better reusability. PMID:21871795

Xie, Wenlei; Yang, Dong

2011-10-01

246

Rare-earth elements modified hydrotalcites and corresponding mesoporous mixed oxides as basic solid catalysts  

Microsoft Academic Search

The inspection of a series of hydrotalcites (HTs) samples prepared under different supersaturation conditions, has allowed the selection of the low supersaturation method conducting to a more disordered HT structure as appropriate to accommodate rare-earth elements (REE) species in HTs structures. The goal is to prepare mesoporous mixed oxides to be used as catalysts for basic catalyzed organic reactions. A

R. Bîrjega; O. D. Pavel; G. Costentin; M. Che; E. Angelescu

2005-01-01

247

Solid state radiolysis of amino acids in an astrochemical perspective  

NASA Astrophysics Data System (ADS)

The aliphatic amino acids L-alanine and L-leucine and the aromatic amino acids L-phenylalanine, L-tyrosine and L-tryptophan were irradiated in the solid state to a dose of 3.2 MGy. The degree of decomposition was measured by differential scanning calorimetry (DSC). Furthermore the degree of radioracemization was measured by optical rotatory dispersion (ORD) spectroscopy. From the DSC measurement a radiolysis rate constant k and the half life T1/2 for each amino acid have been determined and extrapolated to a dose of 14 MGy, which corresponds to the expected total dose delivered by the decay of radionuclides to the organic molecules present in comets and asteroids in 4.6×109 years, the age of the Solar System. It is shown that all the amino acids studied can survive a radiation dose of 14 MGy although they are reduced to 1/4-1/5 of their original value they had at the beginning of the history of the Solar System. Consequently, the amount of alanine or leucine found today in the meteorites known as carbonaceous chondrites is just 1/4-1/5 of the amount originally present at the epoch of the formation of the Solar System 4.6×109 years ago. Among the amino acids studied, tyrosine shows the highest radiation resistance while tryptophan does not combine its relatively high radiation resistance with an elevated level of radioracemization resistance. Apart from the exception of tryptophan, it is shown that the radiolysis rate constants k of all the amino acids studied are in reasonable agreement with the radioracemization rate constant krac.

Cataldo, Franco; Angelini, Giancarlo; Iglesias-Groth, Susana; Manchado, Arturo

2011-01-01

248

BIOINSPIRED CATALYSTS: SYNTHESIS, CHARACTERISATION AND SOME APPLICATIONS  

Microsoft Academic Search

Our recent work concerning the synthesis, characterisation and some applications of bioinspired electron-transfer catalysts is reviewed in this contribution. The catalysts were various mono- or heterobimetallic complexes having either Cu(II) or Cu(II) and Zn(II) as central ions and amino acids, their derivatives or various N- containing organic molecules as ligands. Emphasis was based upon the solid support immobilised versions of

István Pálinkó

249

Cyclization of alkynoic acids in water in the presence of a vesicular self-assembled amphiphilic pincer palladium complex catalyst.  

PubMed

Alkynoic acids were cyclized in the presence of a vesicular palladium-based catalyst and a catalytic amount of triethylamine in water to give the corresponding lactones in moderate-to-good yields. The formation of a vesicular structure was shown to be essential for the promotion of the reaction. PMID:25303771

Hamasaka, Go; Uozumi, Yasuhiro

2014-12-01

250

Polyvalent-metal salts of heteropolyacid as efficient heterogeneous catalysts for Friedel–Crafts acylation of arenes with carboxylic acids  

Microsoft Academic Search

Polyvalent-metal (Ti4+, Fe3+, Sn4+, Bi3+, Ru3+) salts of dodecatungstophosphate act as effective heterogeneous catalysts for Friedel–Crafts acylation of aromatics with carboxylic acids. The Fe3+ salt shows high yields and the highest turnover number (2500) reported to date and can be reused without loss of activity, providing one of the greenest route to aromatic ketones.

Ken-ichi Shimizu; Kenjiro Niimi; Atsushi Satsuma

2008-01-01

251

Comparative analysis of different whole cell immobilized aspergillus niger catalysts for gluconic acid fermentation using pretreated cane molasses  

Microsoft Academic Search

To compare the efficiency of various whole cell immobilization techniques for the production of gluconic acid by Aspergillus niger were investigated using potassium ferrocyanide-treated cane molasses as the substrate. The techniques followed were:(1)Calcium alginate entrapment,(2)cross-linking with glutaraldehyde after cell permeabilization with (a) acetone, (b) toluene and (c) isopropanol and(3)development of granular catalyst.

D. Subba Rao; T. Panda

1994-01-01

252

Green and Efficient Procedure for the Trimethylsilylation of Hydroxy Groups and Their Regeneration Using Sulfamic Acid as Recyclable Catalyst  

Microsoft Academic Search

Structurally diverse alcohols and phenols were efficiently transformed into their corresponding trimethylsilyl ethers with hexamethyldisilazane (HMDS) in the presence of catalytic amounts of sulfamic acid (SA) at room temperature under both acetonitrile and solvent-free conditions. Deprotection of these trimethylsilyl ethers to their parent alcohols and phenols was also achieved using this catalyst in water at room temperature.

Amin Rostami; Firoz Ahmad-Jangi; Mohammad Rezgar Zarebin; Jamal Akradi

2010-01-01

253

A novel direct and one-pot Mannich synthesis of fluorinated ?-aminobutanones with sulfamic acid as a green catalyst  

Microsoft Academic Search

A variety of fluorinated ?-aminobutanones could be obtained in good to excellent yields at room temperature through the direct and three-component Mannich reactions of unmodified acetone with aldehydes and fluorinated anilines in one-pot procedure. Among the catalysts screened, sulfamic acid was tested to the best in aspect of outstanding stability, inexpensive cost, ready recovery and excellently catalytic activity. All the

Min Xia; Yue-Dong Lu

2006-01-01

254

Kinetics and Mechanism of Ethane Oxidation to Acetic Acid on Catalysts Based on Mo-V-Nb Oxides  

E-print Network

Kinetics and Mechanism of Ethane Oxidation to Acetic Acid on Catalysts Based on Mo-V-Nb Oxides and isotopic studies showed that C-H bond activation in ethane by surfaces essentially saturated with lattice oxygens is the sole kinetically relevant step in ethane oxidation on Mo-V-NbOx mixed oxides

Iglesia, Enrique

255

Structural Synergism in Functionalized Polymers: New Catalysts for Transacylation Reactions of Derivatives of Carboxylic and Phosphoric Acids.  

National Technical Information Service (NTIS)

This project has focused on the development of new highly-efficient, selective catalysts for widely-used commercial and biological reactions of carboxylic and phosphoric acids and their derivatives. The first phase of the project included the design and s...

M. Zeldin, W. K. Fife

1991-01-01

256

Chlorine-free Friedel–Crafts acylation of benzene with benzoic anhydride on insoluble heteropoly acid catalyst  

Microsoft Academic Search

Friedel–Crafts acylation of benzene (BEN) with benzoic anhydride (BAN) to produce benzophenone (BPH) was studied over various ion-exchanged heteropoly acids (HPA). No metal chloride such as AlCl3 was used as a catalyst. No acid chloride was used as an acylating agent. Therefore, this reaction could be a model of chlorine-free fine chemical synthesis process. As the activity of benzene was

Tomohiko Tagawa; Junichi Amemiya; Shigeo Goto

2004-01-01

257

One-pot synthesis of 3,4-dihydropyrimidin-2(1 H)-ones using boric acid as catalyst  

Microsoft Academic Search

A simple effective synthesis of 3,4-dihydropyrimidin-2(1H)-one derivatives, using boric acid as catalyst, from aromatic aldehydes, 1,3-dicarbonyl compounds and urea in glacial acetic acid is described. Compared with the classical Biginelli reaction conditions, this new method has the advantage of excellent yields (86–97%) and short reaction time (0.5–2 h).

Shujang Tu; Fang Fang; Chunbao Miao; Hong Jiang; Youjian Feng; Daqing Shi; Xiangshan Wang

2003-01-01

258

On the Acid-Base Mechanism for Ruthenium Water Oxidation Catalysts  

E-print Network

We present a detailed theoretical study of the pathway for water oxidation in synthetic ruthenium-based catalysts. As a first step, we consider a recently discovered single center catalyst, where experimental observations ...

Wang, Lee-Ping

259

Direct Hydrogenation of Biomass-Derived Butyric Acid to n-Butanol over a Ruthenium-Tin Bimetallic Catalyst.  

PubMed

Catalytic hydrogenation of organic carboxylic acids and their esters, for example, cellulosic ethanol from fermentation of acetic acid and hydrogenation of ethyl acetate is a promising possibility for future biorefinery concepts. A hybrid conversion process based on selective hydrogenation of butyric acid combined with fermentation of glucose has been developed for producing biobutanol. ZnO-supported Ru-Sn bimetallic catalysts exhibits unprecedentedly superior performance in the vapor-phase hydrogenation of biomass-derived butyric acid to n-butanol (>98?% yield) for 3500?h without deactivation. PMID:25123894

Lee, Jong-Min; Upare, Pravin P; Chang, Jong-San; Hwang, Young Kyu; Lee, Jeong Ho; Hwang, Dong Won; Hong, Do-Young; Lee, Seung Hwan; Jeong, Myung-Geun; Kim, Young Dok; Kwon, Young-Uk

2014-11-01

260

Liquid phase transesterification of methyl salicylate and phenol over solid acids: Kinetic studies  

Microsoft Academic Search

The liquid phase transesterification of methyl salicylate and phenol to synthesize a value added ester, salol has been studied over the catalysts, ZrO2 (Z), SO42?\\/ZrO2 (SZ) and Mo(VI)\\/ZrO2 (MZ). Physical and chemical characterization of the catalysts in the form of sulfur and Mo(VI) contents, BET surface area, total surface acidity and powder XRD were conducted. Effects of various parameters, such

S. Z. Mohamed Shamshuddin; N. Nagaraju

2007-01-01

261

Solid phase catalysts and reagents. Final technical report, July 1, 1977December 31, 1983  

Microsoft Academic Search

Research supported under this grant for the period 1\\/1\\/80-12\\/31\\/83 has involved six major areas: (1) defining polymer structure-activity relationships in triphase catalytic systems, (2) developing polyether- and polyamide-based catalysts for practical organic synthesis, (3) establishing new synthetic entries into macrolides based on triphase and phase-transfer catalytic principles, (4) introducing new polymeric and monomeric mercury reagents for use in organic synthesis,

Regen

1983-01-01

262

Asymmetric synthesis of protected ?-amino boronic acid derivatives with an air- and moisture-stable Cu(II) catalyst.  

PubMed

The asymmetric borylation of N-tert-butanesulfinyl imines with bis(pinacolato)diboron is achieved using a Cu(II) catalyst and provides access to synthetically useful and pharmaceutically relevant ?-amino boronic acid derivatives. The Cu(II)-catalyzed reaction is performed on the benchtop in air at room temperature using commercially available, inexpensive reagents at low catalyst loadings. A variety of N-tert-butanesulfinyl imines, including ketimines, react readily to provide ?-sulfinamido boronate esters in good yields and with high stereoselectivity. In addition, this transformation is applied to the straightforward, telescoped synthesis of ?-sulfinamido trifluoroborates. PMID:24684495

Buesking, Andrew W; Bacauanu, Vlad; Cai, Irene; Ellman, Jonathan A

2014-04-18

263

The influence of metal and carrier natures on the effectiveness of catalysts of the deoxygenation of fatty acids into hydrocarbons  

NASA Astrophysics Data System (ADS)

The activity and selectivity of palladium, copper, platinum, and nickel catalysts in the decarbonylation of stearic acid into hydrocarbons were studied at a 14 atm hydrogen pressure and temperatures of 300-350°C. If ?-alumina was used as a carrier, the catalysts formed the series Pd > Cu > Pt > Ni according to desired product yields. Quantum-chemical simulation was performed to show that the free energy of activation increased in the same series. The same metals deposited on mixed tungsten and zirconium oxides catalyzed decarbonylation with a low yield of C17 hydrocarbons, likely because such a superacidic carrier could catalyse cracking of olefins or their oligomers formed.

Berenblyum, A. S.; Shamsiev, R. S.; Podoplelova, T. A.; Danyushevsky, V. Ya.

2012-08-01

264

Tuning the acid/metal balance of carbon nanofiber-supported nickel catalysts for hydrolytic hydrogenation of cellulose.  

PubMed

Carbon nanofibers (CNFs) are a class of graphitic support materials with considerable potential for catalytic conversion of biomass. Earlier, we demonstrated the hydrolytic hydrogenation of cellulose over reshaped nickel particles attached at the tip of CNFs. The aim of this follow-up study was to find a relationship between the acid/metal balance of the Ni/CNFs and their performance in the catalytic conversion of cellulose. After oxidation and incipient wetness impregnation with Ni, the Ni/CNFs were characterized by various analytical methods. To prepare a selective Ni/CNF catalyst, the influences of the nature of oxidation agent, Ni activation, and Ni loading were investigated. Under the applied reaction conditions, the best result, that is, 76 % yield in hexitols with 69 % sorbitol selectivity at 93 % conversion of cellulose, was obtained on a 7.5 wt % Ni/CNF catalyst prepared by chemical vapor deposition of CH(4) on a Ni/?-Al(2)O(3) catalyst, followed by oxidation in HNO(3) (twice for 1 h at 383 K), incipient wetness impregnation, and reduction at 773 K under H(2). This preparation method leads to a properly balanced Ni/CNF catalyst in terms of Ni dispersion and hydrogenation capacity on the one hand, and the number of acidic surface-oxygen groups responsible for the acid-catalyzed hydrolysis on the other. PMID:22730195

Van de Vyver, Stijn; Geboers, Jan; Schutyser, Wouter; Dusselier, Michiel; Eloy, Pierre; Dornez, Emmie; Seo, Jin Won; Courtin, Christophe M; Gaigneaux, Eric M; Jacobs, Pierre A; Sels, Bert F

2012-08-01

265

Degradation of salicylic acid by photo-assisted Fenton reaction using Fe ions on strongly acidic ion exchange resin as catalyst  

Microsoft Academic Search

The photo-assisted Fenton degradation of salicylic acid (SA) was studied by using strongly acidic ion exchange resin (SAIER) exchanged with Fe ions as catalyst in the presence of UV light (254nm) and H2O2. The X-ray photoelectron spectroscopy (XPS) results revealed that the Fe ions are indeed anchored by the sulfonate groups on the surface of the SAIER and are Fe3+.

Jiyun Feng; Xijun Hu; Po Lock Yue

2004-01-01

266

Study on the structure, acidic properties of V-Zr nanocrystal catalysts in oxidative dehydrogenation of propane  

NASA Astrophysics Data System (ADS)

A series of V-doped zirconia nanocrystal (the molar ratio of V/Zr varying from 0.001 to 0.15) were prepared via hydrothermal method and performed in oxidative dehydrogenation of propane. It was found that vanadium was highly dispersed on the surface and in the bulk of ZrO2. The distribution of the vanadium species, the valence states and the aggregation state of V species on the surface, as well as the acid properties of the catalysts including kinds, number and strength were detected by the various characteristic methods. The correlation between the V content and the surroundings of the different V species has been studied. The function of acid properties, especially Brønsted acid in the catalytic performance has been discussed. Oxidative dehydrogenation reactions were carried out in a continuous flow fixed bed reactor and ZrV0.01 catalyst showed good conversion and selectivity with a yield of propylene of 21.3%.

Chen, Shu; Ma, Fei; Xu, Aixin; Wang, Lina; Chen, Fang; Lu, Weimin

2014-01-01

267

Model reaction for the in situ characterization of the hydrogenating and acid properties of industrial hydrocracking catalysts  

SciTech Connect

A kinetic study of o-xylene transformation was carried out on a sulfided NiMo on Y zeolite catalyst during the hydrocracking of a model compound (n-heptane) under the following conditions of the process: high hydrogen pressure (5.7 MPa), presence of nitrogen and sulfur-containing compounds. o-Xylene inhibits n-heptane transformation, which can be explained by a competition for the adsorption on the acid sites between o-xylene and the olefinic intermediates of hydrocracking. The products of o-xylene transformation are the following: p- and m-xylenes (isomerization), toluene and trimethylbenzenes (disproportionation), and saturated C{sub 8} naphthenes (dimethylcyclohexane and trimethylcyclopentanes). It is shown that 1,3- and 1,4-dimethylcyclohexanes (and trimethylcyclopentanes) result from the isomerization of m- and p-xylenes. Therefore, the hydrogenating activity of hydrocracking catalysts can be characterized by the formation of dimethylyclohexanes and trimethylcyclopentanes. Furthermore, the isomerization of xylenes, which occurs through an acid mechanism, can be used for characterizing the acid activity of hydrocracking catalysts. This is not the case for disproportion whose rate depends on hydrogen pressure. The validity of o-xylene transformation for characterizing the acid and hydrogenating activities of bifunctional hydrocracking catalysts was confirmed by the use of a series of catalysts having either the same content of NiMo and different contents of zeolite or the same content of zeolite and different contents of NiMo. While the isomerization activity is strictly proportional to the zeolite content and independent of the NiMo content, and the hydrogenating activity is proportional to the NiMo content and independent of the zeolite content. 27 refs., 17 figs., 3 tabs.

Guisnet, M.; Thomazeau, C.; Lemberton, J.L. [Laboratoire de Catalyse en Chimie Organique, Poitiers (France)] [Laboratoire de Catalyse en Chimie Organique, Poitiers (France); Mignard, S. [Institut Francais du Petrole, Rueil-Malmaison (France)] [Institut Francais du Petrole, Rueil-Malmaison (France)

1995-01-01

268

Stepwise engineering of a Pichia pastoris D-amino acid oxidase whole cell catalyst  

PubMed Central

Background Trigonopsis variabilis D-amino acid oxidase (TvDAO) is a well characterized enzyme used for cephalosporin C conversion on industrial scale. However, the demands on the enzyme with respect to activity, operational stability and costs also vary with the field of application. Processes that use the soluble enzyme suffer from fast inactivation of TvDAO while immobilized oxidase preparations raise issues related to expensive carriers and catalyst efficiency. Therefore, oxidase preparations that are more robust and active than those currently available would enable a much broader range of economically viable applications of this enzyme in fine chemical syntheses. A multi-step engineering approach was chosen here to develop a robust and highly active Pichia pastoris TvDAO whole-cell biocatalyst. Results As compared to the native T. variabilis host, a more than seven-fold enhancement of the intracellular level of oxidase activity was achieved in P. pastoris through expression optimization by codon redesign as well as efficient subcellular targeting of the enzyme to peroxisomes. Multi copy integration further doubled expression and the specific activity of the whole cell catalyst. From a multicopy production strain, about 1.3 × 103 U/g wet cell weight (wcw) were derived by standard induction conditions feeding pure methanol. A fed-batch cultivation protocol using a mixture of methanol and glycerol in the induction phase attenuated the apparent toxicity of the recombinant oxidase to yield final biomass concentrations in the bioreactor of ? 200 g/L compared to only 117 g/L using the standard methanol feed. Permeabilization of P. pastoris using 10% isopropanol yielded a whole-cell enzyme preparation that showed 49% of the total available intracellular oxidase activity and was notably stabilized (by three times compared to a widely used TvDAO expressing Escherichia coli strain) under conditions of D-methionine conversion using vigorous aeration. Conclusions Stepwise optimization using a multi-level engineering approach has delivered a new P. pastoris whole cell TvDAO biocatalyst showing substantially enhanced specific activity and stability under operational conditions as compared to previously reported preparations of the enzyme. The production of the oxidase through fed-batch bioreactor culture and subsequent cell permeabilization is high-yielding and efficient. Therefore this P. pastoris catalyst has been evaluated for industrial purposes. PMID:20420682

2010-01-01

269

Efficient hydroalkoxylation of alkenes to generate octane-boosting ethers using recyclable metal triflates and highly active metal triflate\\/Brønsted acid-assisted catalysts  

Microsoft Academic Search

gem-Disubstituted alkenes are directly and readily etherified with alcohols using Al(OTf)3 and Zr(OTf)4 as recyclable Lewis acid catalysts. In contrast, primary or secondary alkene analogues were inert under these conditions, enabling excellent chemoselectivity. Lanthanide triflates are inactive as catalysts for such reactions, as is phosphoric acid. But a combination of these two otherwise inactive entities led to an ‘assisted acidity

D. Bradley G. Williams; Mike S. Sibiya; Pieter S. van Heerden

270

Catalyst-free fatty acid methyl ester production from wet activated sludge under subcritical water and methanol condition.  

PubMed

Wet activated sludge was converted directly into biodiesel using water as hydrolysis reagent to enhance the extraction of lipid in activated sludge, and as catalyst for the conversion of neutral lipids into biodiesel under subcritical conditions. At 175°C, 3.5MPa, a methanol to sludge ratio of 30 (mL/g) and a sludge water content of 84wt.%, about 90% conversion to fatty acid methyl esters was achieved within 24h without the need for conventional catalysts such as KOH and H(2)SO(4). Since water is employed as a catalyst, its removal is not required; therefore, the processing costs for producing biodiesel from activated sludge are reduced. The method has the potential for applications to other feedstock with high water contents such as micro-algae. PMID:22940307

Huynh, Lien Huong; Tran Nguyen, Phuong Lan; Ho, Quoc Phong; Ju, Yi-Hsu

2012-11-01

271

Graphene-based nanomaterials as heterogeneous acid catalysts: a comprehensive perspective.  

PubMed

Acid catalysis is quite prevalent and probably one of the most routine operations in both industrial processes and research laboratories worldwide. Recently, "graphene", a two dimensional single-layer carbon sheet with hexagonal packed lattice structure, imitative of nanomaterials, has shown great potential as alternative and eco-friendly solid carbocatalyst for a variety of acid-catalyzed reactions. Owing to their exceptional physical, chemical, and mechanical properties, graphene-based nanomaterials (G-NMs) offer highly stable Brønsted acidic sites, high mass transfer, relatively large surface areas, water tolerant character, and convenient recoverability as well as recyclability, whilst retaining high activity in acid-catalyzed chemical reactions. This comprehensive review focuses on the chemistry of G-NMs, including their synthesis, characterization, properties, functionalization, and up-to-date applications in heterogeneous acid catalysis. In line with this, in certain instances readers may find herein some criticisms that should be taken as constructive and would be of value in understanding the scope and limitations of current approaches utilizing graphene and its derivatives for the same. PMID:25225721

Garg, Bhaskar; Bisht, Tanuja; Ling, Yong-Chien

2014-01-01

272

Direct one-pot conversion of acylated carbohydrates into their alkylated derivatives under heterogeneous reaction conditions using solid NaOH and a phase transfer catalyst  

Microsoft Academic Search

A convenient one-pot protocol for the direct conversion of acyl-protected carbohydrates into their alkylated counterparts has been developed by using alkyl halides in the presence of solid sodium hydroxide and a phase transfer catalyst. These economically convenient, mild, two-phase reaction conditions allow the preparation of a variety of monosaccharide intermediates for use in the synthesis of complex oligosaccharides.

Soni Kamlesh Madhusudan; Geetanjali Agnihotri; Devendra S. Negi; Anup Kumar Misra

2005-01-01

273

Solid-phase synthesis of new S-glycoamino acid building blocks.  

PubMed

Efficient synthesis of unprotected S-glycoamino acid building blocks in the solid phase by coupling a sugar 1-thiolate with iodine activated fluoren-9-ylmethoxycarbonyl (Fmoc) protected amino acids. PMID:10930259

Jobron, L; Hummel, G

2000-07-27

274

The outer-coordination sphere: incorporating amino acids and peptides as ligands for homogeneous catalysts to mimic enzyme function  

SciTech Connect

Great progress has been achieved in the field of homogeneous transition metal-based catalysis, however, as a general rule these solution based catalysts are still easily outperformed, both in terms of rates and selectivity, by their analogous enzyme counterparts, including structural mimics of the active site. This observation suggests that the features of the enzyme beyond the active site, i.e. the outer-coordination sphere, are important for their exceptional function. Directly mimicking the outer-coordination sphere requires the incorporation of amino acids and peptides as ligands for homogeneous catalysts. This effort has been attempted for many homogeneous catalysts which span the manifold of catalytic reactions and often require careful thought regarding solvent type, pH and characterization to avoid unwanted side reactions or catalyst decomposition. This article reviews the current capability of synthesizing and characterizing this often difficult category of metal-based catalysts. This work was funded by the DOE Office of Science Early Career Research Program through the Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

Shaw, Wendy J.

2012-10-09

275

A novel method for synthesis of phosphomolybdic acid-modified Pd/C catalysts for oxygen reduction reaction  

NASA Astrophysics Data System (ADS)

This manuscript reports a convenient method for immobilizing phosphomolybdic acid (HPMo) on polyaniline (PAN-) functionalized carbon supports. The obtained HPMo-PAN-C sample is used as the support to prepare a Pd/HPMo-PAN-C catalyst. The samples are characterized by Fourier transform infrared spectroscopy, transmission electron microscopy and X-ray diffraction analysis. The results suggest that HPMo retains its Keggin structure and that the presence of HPMo reduces the average particle size of the Pd nano-particles in the obtained Pd/HPMo-PAN-C catalyst. Electro-chemical measurements in 0.5 M HClO4 solution reveal that the Pd/HPMo-PAN-C catalyst has higher catalytic activity for oxygen reduction reactions than does a Pd/C catalyst prepared using a similar procedure. The stability of the Pd/HPMo-PAN-C catalyst is evaluated by multiple-cycle voltammetry techniques; the mass catalytic activity decreases by only 10% after 100 scanning cycles.

Zhu, Mingyuan; Gao, Xiaoling; Luo, Guangqin; Dai, Bin

2013-03-01

276

Multifunctional pd/ni-co catalyst for hydrogen production by chemical looping coupled with steam reforming of acetic Acid.  

PubMed

High yield of high-purity H2 from acetic acid, a model compound of bio-oil obtained from the fast pyrolysis of biomass, was produced by sorption-enhanced steam reforming (SESR). An oxygen carrier was introduced into a chemical loop (CL) coupled to the cyclical SESR process to supply heat in?situ for the endothermic sorbent regeneration to increase the energy efficiency of the process. A new multifunctional 1?%Pd/20?%Ni-20?%Co catalyst was developed for use both as oxygen carrier in the CL and as reforming catalyst in the SESR whereas a CaO-based material was used as CO2 sorbent. In the sorbent-air regeneration step, the Ni-Co atoms in the catalyst undergo strong exothermic oxidation reactions that provide heat for the CaO decarbonation. The addition of Pd to the Ni-Co catalyst makes the catalyst active throughout the whole SESR-CL cycle. Pd significantly promotes the reduction of Ni-Co oxides to metallic Ni-Co during the reforming stage, which avoids the need for a reduction step after regeneration. H2 yield above 90?% and H2 purity above 99.2?vol?% were obtained. PMID:25209388

Fermoso, Javier; Gil, María V; Rubiera, Fernando; Chen, De

2014-11-01

277

MIL-101-SO3 H: A Highly Efficient Brønsted Acid Catalyst for Heterogeneous Alcoholysis of Epoxides under Ambient Conditions.  

PubMed

For the first time, a ?100?% sulfonic acid functionalized metal-organic framework (MOF), MIL-101-SO3 H, with giant pores has been prepared by a hydrothermal process followed by a facile postsynthetic HCl treatment strategy. The replete readily accessible Lewis acidic and especially Brønsted acidic sites distributed throughout the framework as well as high stability endow the resultant MOF exceptionally high efficiency and recyclability, which surpass all other MOF-based catalysts, for the ring opening of epoxides with alcohols (especially, methanol) as nucleophiles under ambient conditions. PMID:25291973

Zhou, Yu-Xiao; Chen, Yu-Zhen; Hu, Yingli; Huang, Gang; Yu, Shu-Hong; Jiang, Hai-Long

2014-11-10

278

Synthesis of dimethyl ether from methanol over aluminium phosphate and silica–titania catalysts  

Microsoft Academic Search

A series of solid–acid catalysts with different content of components were prepared by co-precipitation (sol–gel) method. These samples comprised silica–titania and modified ?-Al2O3 with phosphorus. To determination of optimum ones, the effects of various contents of phosphorus have been investigated. Dehydration of methanol to dimethyl ether (DME) on solid–acid catalysts was studied in a fixed-bed reactor at a temperature of

F. Yaripour; F. Baghaei; I. Schmidt; J. Perregaard

2005-01-01

279

Atmospheric Secondary Aerosol Formation by Heterogeneous Reactions of Aldehydes in the Presence of a Sulfuric Acid Aerosol Catalyst  

NASA Astrophysics Data System (ADS)

Particle growth by the heterogeneous reaction of aldehydes was observed in 0.5 m3 indoor Teflon bags in the presence of background seed aerosols. The aldehydes used were: glyoxal, butanal, hexanal, octanal, and decanal. To study acid catalyst effects on aldehyde heterogeneous reactions, one of the Teflon bags was initially filled with seed aerosols composed of ammonium sulfate-aerosol acidified with sulfuric acid. This result was compared to particle growth reactions that contained only ammonium sulfate as a background seed aerosol. The gas phase aldehydes were then added to the Teflon bags. In selected experiments, 1-decanol was also added to the Teflon bags with aldehydes to clarify particle growth via a heterogeneous hemiacetal/acetal formation in the presence/absence of an acid catalyst. The particle size distribution and growth were measured using a differential mobility analyzer (DMA), and the results were applied to predicting aerosol growth and size distribution changes by condensation and heterogeneous reactions. Aerosols created from the heterogeneous reactions of aldehydes were collected directly on an ungreased zinc selenide (ZnSe) FTIR disk (25 mm in diameter) by impaction. The ZnSe disks were directly analyzed for product functional groups in the aerosol phase using a Fourier transform infrared (FTIR) spectrometer with a deuterated triglycine sulfate (DTGS) detector. Aerosol growth by heterogeneous aldehyde reactions proceeds via a hydration, polymerization process, hemiacetal/acetal formation from the reaction of aldehydes with alcohols. These aldehyde heterogeneous reactions were accelerated in the presence of an acid catalyst, H2SO4, and led to higher aerosol yields than when H2SO4 was not present in the seed aerosol. The FTIR spectra obtained from the growing aerosol, also illustrated aldehyde group transformation in the particle phase as a function of the heterogeneous reaction. It was concluded that aldehydes, which can be produced by atmospheric photochemical reactions, can significantly contribute on secondary aerosol formation through heterogeneous reactions in the presence of an acid catalyst.

Jang, M.; Kamens, R. M.

2001-12-01

280

Development of biomimetic catalytic oxidation methods and non-salt methods using transition metal-based acid and base ambiphilic catalysts  

PubMed Central

This review focuses on the development of ruthenium and flavin catalysts for environmentally benign oxidation reactions based on mimicking the functions of cytochrome P-450 and flavoenzymes, and low valent transition-metal catalysts that replace conventional acids and bases. Several new concepts and new types of catalytic reactions based on these concepts are described. PMID:21558760

MURAHASHI, Shun-Ichi

2011-01-01

281

Oxyhydrochlorination catalyst  

DOEpatents

An improved catalyst and method for the oxyhydrochlorination of methane is disclosed. The catalyst includes a pyrogenic porous support on which is layered as active material, cobalt chloride in major proportion, and minor proportions of an alkali metal chloride and of a rare earth chloride. On contact of the catalyst with a gas flow of methane, HCl and oxygen, more than 60% of the methane is converted and of that converted more than 40% occurs as monochloromethane. Advantageously, the monochloromethane can be used to produce gasoline boiling range hydrocarbons with the recycle of HCl for further reaction. This catalyst is also of value for the production of formic acid as are analogous catalysts with lead, silver or nickel chlorides substituted for the cobalt chloride.

Taylor, Charles E. (Pittsburgh, PA); Noceti, Richard P. (Pittsburgh, PA)

1992-01-01

282

One-pot three-component Mannich-type reactions using Sulfamic acid catalyst under ultrasound irradiation  

Microsoft Academic Search

Sulfamic acid (NH2SO3H, SA) was used as an efficient, inexpensive, non-toxic and recyclable green catalyst for the ultrasound-assisted one-pot Mannich reaction of aldehydes with ketones and amines. This ultrasound protocol has advantages of high yield, mild condition, no environmental pollution, and simple work-up procedures. Most importantly, ?-aminocarbonyl compounds with ortho-substituted aromatic amines are obtained in acceptable to good yields by

Hongyao Zeng; Hua Li; Huawu Shao

2009-01-01

283

CuO\\/NiO monolithic catalysts for NO x removal from nitric acid plant flue gas  

Microsoft Academic Search

The performance of copper\\/nickel oxide catalysts supported on ceramic monoliths of ?-alumina\\/silicate, for the selective catalytic reduction (SCR) of nitrogen oxides in flue gas from nitric acid plants ([NO]\\/[NOx]=0.7) has been studied. The monoliths prepared were characterised by thermogravimetry, nitrogen adsorption–desorption, mercury intrusion porosimetry (MIP), X-ray diffraction (XRD), electron probe microanalysis wavelength dispersion spectroscopy (EPMA-WDS) and their mechanical strengths were

Jesús Blanco; Pedro Avila; Silvia Suárez; Malcolm Yates; Juan Antonio Martin; Luis Marzo; Carlos Knapp

2004-01-01

284

Chiral rare earth organophosphates as homogeneous Lewis acid catalysts for the highly enantioselective hetero-Diels–Alder reactions  

Microsoft Academic Search

Various trivalent rare earth-chiral phosphate complexes [(R)-1-RE, (R)-3-RE, and (R)-4-Ce] were prepared and evaluated as a Lewis acid catalyst for the asymmetric hetero-Diels–Alder reaction of aldehydes with the Danishefsky's diene. Some of them effectively promoted the reaction at room temperature in the presence or absence of achiral additives under homogeneous conditions to afford the corresponding cycloadducts with high ee's (up

Hiroshi Furuno; Tetsuji Hayano; Takeshi Kambara; Yuichi Sugimoto; Takeshi Hanamoto; Yumiko Tanaka; Yong Zhi Jin; Takumi Kagawa; Junji Inanaga

2003-01-01

285

Effects of Lewis acid-surfactant-combined catalysts on aldol and Diels-Alder reactions in water  

Microsoft Academic Search

Aldol and Diels-Alder reactions in water in the presence of various dodecyl sulfate and dodecanesulfonate salts as Lewis acid-surfactant-combined catalysts have been studied. In the aldol reactions, these salts differed from each other with respect to their catalytic ability at the initial stage of the reaction and to the final yields of the aldol product, while these salts did not

Kei Manabe; Yuichiro Mori; Sh? Kobayashi

1999-01-01

286

Recovery of molybdenum and vanadium from synthetic sulphuric acid leach solutions of spent hydrodesulphurisation catalysts using solvent extraction  

Microsoft Academic Search

A commercially available extractant, LIX®63 was used to investigate the extraction of molybdenum(VI) and vanadium(V) from a synthetic sulphuric acid leach solution of spent hydrodesulphurisation catalysts. The molybdenum(VI) and vanadium(V) were extracted and separated completely from other metals at pH 1.5. The loaded organic solution was easily stripped by NaOH solution with excellent phase separation. After the precipitation of most

Li Zeng; Chu Yong Cheng

2010-01-01

287

Electrochemical Characterization of Solid Acid Fuel Cell Electrodes  

NASA Astrophysics Data System (ADS)

The quest for high-efficiency, high-power output fuel cells can be largely equated to the quest for high-performance components (anode, cathode, electrolyte). Solid Acid electrolytes, notably CsH2PO4, have been demonstrated to be affordable, stable, excellent ion conductors, and impermeable to parasitic fuel cross-over. Moreover, they operate at a temperature `sweet-spot' high enough to promote electrode kinetics and low enough to enable low-cost infrastructure. Fuel cell devices based on these materials are known to be limited, however, by electrode losses---even with high platinum loading. Improving the performance and lowering the cost of these components is necessary if such devices are to be considered viable alternatives. In this work, the primary focus was the development of electrochemical characterization approaches. In doing so, we investigated electrode losses through steady-state and time-dependent electrochemical characterization and identified the primary rate limiting process and mechanism as oxygen reduction at the cathode. To characterize anode kinetics, new testing approaches were implemented which employed robust, asymmetric electrode geometries to isolate electrode kinetics without the inclusion of a reference electrode. These geometries' isolation efficacy was assessed by numerical computation---the results of which were leveraged into an explicitly defined, material-agnostic tool to evaluate asymmetric electrode geometries. While for platinum, the cathode mechanism was shown to be insensitive to the microstructures tested, the mechanism of hydrogen reduction/oxidation was seen to vary between nanoscale powder and microscale defined electrodes---reconfirming the importance of rigorous testing approaches. Asymmetric electrode geometries with defined microstructures allowed direct characterization and comparative evaluation of non-platinum candidates for both the anode and the cathode. On the anode, palladium was over an order of magnitude more active than platinum and nickel, which exhibited a comparable activity. Palladium and silver were shown to be stable cathode materials, though less active than platinum. As a demonstration of the developed methodology's flexibility, a palladium-silver alloy was synthesized and tested. The tools and methodologies developed in this work enable the rapid and flexible screening of electrodes for solid acid fuel cells.

Sasaki, Kenji Alexander

288

Tosic Acid-on-Silica Gel: A Cheap and Eco-friendly Catalyst for a Convenient One-pot Synthesis of Substituted Benzimidazoles  

Microsoft Academic Search

Summary.  2-Substituted and 1,2-disubstited benzimidazoles were prepared efficiently from o-phenylenediamines and aryl aldehydes using p-toluenesulphonic acid (5?mol%)-on-silica gel as a cheap and environmentally benign catalyst.

Manas Chakrabarty; Ratna Mukherjee; Sulakshana Karmakar; Yoshihiro Harigaya

2007-01-01

289

Solvent-Free Tetrahydropyranylation of Alcohols with Sulfamic Acid as Reusable Catalyst  

Microsoft Academic Search

An efficient H2NSO3H-catalyzed solvent-free tetrahydropyranylation of various alcohols at room temperature was investigated. The features of mild conditions, cost-efficient catalyst, simple work-up, and the recyclability of the catalyst were displayed in this article.

Bo Wang; Li-Ming Yang; Ji-Shuan Suo

2003-01-01

290

Catalytic Upgrading of bio-oil using 1-octene and 1-butanol over sulfonic acid resin catalysts  

SciTech Connect

Raw bio-oil from fast pyrolysis of biomass must be refined before it can be used as a transporation fuel, a petroleum refinery feed or for many other fuel uses. Raw bio-oil was upgraded with the neat model olefin, 1-octene, and with 1-octene/1-butanol mixtures over sulfonic acid resin catalysts frin 80 to 150 degrees celisus in order to simultaneously lower water content and acidity and to increase hydrophobicity and heating value. Phase separation and coke formation were key factors limiting the reaction rate during upgrading with neat 1-octene although octanols were formed by 1-octene hydration along with small amounts of octyl acetates and ethers. GC-MS analysis confirmed that olefin hydration, carboxylic acid esterification, acetal formation from aldehydes and ketones and O- and C-alkylations of phenolic compounds occurred simultaneously during upgrading with 1-octene/1-butanol mixtures. Addition of 1-butanol increased olefin conversion dramatically be reducing mass transfer restraints and serving as a cosolvent or emulsifying agent. It also reacted with carboxylic acids and aldehydes/ketones to form esters, and acetals, respectively, while also serving to stabilize bio-oil during heating. 1-Butanol addition also protected the catalysts, increasing catalyst lifetime and reducing or eliminationg coking. Upgrading sharply increased ester content and decreased the amounts of levoglucosan, polyhydric alcohols and organic acids. Upgrading lowered acidity (pH value rise from 2.5 to >3.0), removed the uppleasant ordor and increased hydrocarbon solubility. Water content decreased from 37.2% to < 7.5% dramatically and calorific value increased from 12.6 MJ kg to about 30.0 MJ kg.

Zhang, Zhijun; Wang, Qingwen; Tripathi, Prabhat; Pittman, Charles U.

2011-02-04

291

Interaction of Peroxynitric Acid with Solid H2O Ice  

NASA Technical Reports Server (NTRS)

The uptake of peroxynitric acid (PNA), HO2NO2 or HNO4, on solid H2O ice at 193 K (-80 C) was studied using a fast flow-mass spectrometric technique. An uptake coefficient of 0.15 +/- 0.10 was measured, where the quoted uncertainty denotes 2 standard deviations. The uptake process did not result in the production of gas phase products. The composition of the condensed phase was investigated using programmed heating (3 K/min) of the substrate coupled with mass spectrometric detection of desorbed species. Significant quantities of HNO, and HNO3 desorbed from the substrates at temperatures above 225 K and 246 K, respectively. The desorbed HNO3, which was less than 9% of the desorbed HNO, and remained unchanged upon incubation of the substrate, was likely due to impurities in the HNO4 samples rather than reaction of HNO, on the substrate. The onset temperatures for HNO4 desorption increased with increasing H2O to HNO4 ratios, indicating that HNO4, like HNO3, tends to be hydrated in the presence of water. These observations suggest possible mechanisms for removal of HNO4 or repartitioning of total odd nitrogen species in the Earth's upper troposphere and stratosphere.

Li, Zhuangjie; Friedl, Randall R.; Moore, Steven B.; Sander, Stanley P.

1996-01-01

292

Acid-base site detection and mapping on solid surfaces by Kelvin force microscopy (KFM).  

PubMed

Electrostatic potential at the surface of acidic or basic solids changes under higher relative humidity (RH), as determined by using Kelvin force microscopy (KFM). The potential on acid surfaces becomes more negative as the water vapor pressure increases, while it becomes more positive on basic solids. These results verify the following hypothesis: OH(-) or H(+) ions associated with atmospheric water ion clusters are selectively adsorbed on solid surfaces, depending on the respective Brønsted acid or base character. Therefore, Kelvin microscopy, under variable humidity, is a rigorous but convenient alternative to determine the acid-base character of solid surfaces, with a great advantage: it uses only one amphoteric and simple reagent to determine both the acid and base sites. Moreover, this technique provides information on the spatial distribution of acid-base sites, which is currently inaccessible to any other method. PMID:23126418

Gouveia, Rubia F; Bernardes, Juliana S; Ducati, Telma R D; Galembeck, Fernando

2012-12-01

293

Aerobic oxidation of trimethylbenzenes catalyzed by N, N?, N?-trihydroxyisocyanuric acid (THICA) as a key catalyst  

Microsoft Academic Search

The oxidation of trimethylbenzenes was examined with air or O2 using N,N?,N?-trihydroxyisocyanuric acid (THICA) as a key catalyst. Thus, 1,2,3-, 1,2,4-, and 1,3,5-trimethylbenzenes under air (20atm) in the presence of THICA (5mol%), Co(OAc)2 (0.5mol%), Mn(OAc)2, and ZrO(OAc)2 at 150°C were oxidized to the corresponding benzenetricarboxylic acids in good yields (81–97%). In the aerobic oxidation of 1,2,4-trimethylbenzene by the THICA\\/Co(II)\\/Mn(II) system,

Naruhisa Hirai; Yoshinobu Tatsukawa; Michiko Kameda; Satoshi Sakaguchi; Yasutaka Ishii

2006-01-01

294

Sulfonic Acid Functionalized Nano-?-Al2O3: A New, Efficient, and Reusable Catalyst for Synthesis of 3-Substituted-2H-1,4-Benzothiazines  

PubMed Central

A simple and efficient synthetic protocol has been developed for the synthesis of 3-substituted-2H-1,4-benzothiazines by using a novel sulfonic acid functionalized nano-?-Al2O3 catalyst, devoid of corrosive acidic, and basic reagents. The developed method has the advantages of good to excellent yields, short reaction times, operational simplicity, and a recyclable catalyst. The catalyst can be prepared by a simple procedure from inexpensive and readily available nano-?-Al2O3 and has been shown to be recoverable and reusable up to six cycles without any loss of activity. PMID:23935435

Li, Wei Lin; Tian, Shuan Bao; Zhu, Feng

2013-01-01

295

Improved performance of Mo-V-Te-Nb-O x catalysts prepared from a solution containing drying control chemical additives in propane oxidation to acrylic acid  

Microsoft Academic Search

Mo1.0V0.4Te0.25Nb0.24O\\u000a x\\u000a catalyst was prepared by hydrothermal synthesis in a solution containing a drying control chemical additive (DCCA) such as\\u000a propionic acid (PA) or formamide (FA). The performance of the prepared catalysts in propane oxidation for producing acrylic\\u000a acid (AA) was improved because the catalyst showed an increase in both the activity and AA selectivity. The activity was increased\\u000a due

Sang Seop Kum; Yoon Sik Park; Sang Heup Moon

2011-01-01

296

Ti-MCM-41 supported phosphotungstic acid: An effective and environmentally benign catalyst for epoxidation of styrene  

NASA Astrophysics Data System (ADS)

Mesoporous Ti-MCM-41 molecular sieve was synthesized under hydrothermal conditions. 5, 10, 20, 30 and 50 wt.% phosphotungstic acid (H 3PW 12O 40) (PW) were supported on Ti-MCM-41 and the resulting catalysts were characterized by powder X-ray diffraction (XRD), N 2 adsorption-desorption, Fourier transform infrared spectroscopy (FT-IR), UV-vis diffuse reflectance spectroscopy (DRS), thermogravimetric analysis (TGA) and differential thermal analysis (DTA), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and high-resolution transmission electron microscopy (HRTEM). The host material suffers severe structural distortions at higher loading, which lead to a considerable loss of long-range orders. Their catalytic performances were evaluated in the epoxidation of styrene with dilute H 2O 2 (30%) as an oxidizing agent under liquid-phase reaction conditions over PW/Ti-MCM-41 catalysts for selective synthesis of styrene oxide. The influences of various reaction parameters such as temperature, time, solvents, PW loading and catalyst amount, styrene to H 2O 2 mmol ratios and acetonitrile (MeCN) to N, N-dimethylformamide (DMF) volume ratios on the conversion of styrene and yield as well as selectivity of styrene oxide have also been studied in details. The results revealed that 20% PW/Ti-MCM-41 was more active than other catalysts. The PW/Ti-MCM-41, moreover, was found to be reusable and effective for the epoxidation of styrene.

Wang, GuangJian; Liu, GuangQing; Xu, MingXia; Yang, ZhenXing; Liu, ZhengWang; Liu, YiWu; Chen, ShiFu; Wang, Lei

2008-12-01

297

Catalyst functionalized buffer sorbent pebbles for rapid separation of carbon dioxide from gas mixtures  

SciTech Connect

A method for separating CO.sub.2 from gas mixtures uses a slurried media impregnated with buffer compounds and coating the solid media with a catalyst or enzyme that promotes the transformation of CO.sub.2 to carbonic acid. Buffer sorbent pebbles with a catalyst or enzyme coating are provided for rapid separation of CO.sub.2 from gas mixtures.

Aines, Roger D.

2013-03-12

298

Transesterification of soybean oil catalyzed by potassium loaded on alumina as a solid-base catalyst  

Microsoft Academic Search

Biodiesel fuel, consisting of methyl esters of long chain fatty acids produced by transesterification of vegetable oils or animal fats with methanol, is a promising alternative diesel fuel regarding the limited resources of fossil fuels and the environmental concerns. In this work, an environmentally benign process for the transesterification of soybean oil to methyl esters using alumina loaded with potassium

Wenlei Xie; Hong Peng; Ligong Chen

2006-01-01

299

Microwave radiation solid-phase synthesis of phosphotungstate nanoparticle catalysts and photocatalytic degradation of formaldehyde  

Microsoft Academic Search

Photocatalysts M3PW12O40 (M=NH4+, Cs+, Ag+, Cu2+) were prepared by microwave radiation solid-phase synthesis method. The results from SEM and XRD characterization reveal that the average particle size of M3PW12O40 is 15–80nm. Diffuse reflectance UV–vis spectra of M3PW12O40 shows that the absorption band shifted from 260 to 270–350nm and become broad in comparison with those of H3PW12O40. The results of photocatalytic

Qian Deng; Wenhui Zhou; Xiaomei Li; Zhenshan Peng; Shaoliang Jiang; Ming Yue; Tiejun Cai

2007-01-01

300

An unprecedented (3,4,24)-connected heteropolyoxozincate organic framework as heterogeneous crystalline Lewis acid catalyst for biodiesel production  

PubMed Central

A novel 3D hexadecanuclear heteropolyoxozincate organic framework, IFMC-200, has been successfully synthesized based on a late transition metal-oxygen cluster. IFMC-200 not only represents the first example of (3,4,24)-connected framework but also contains the first 24-connected single metal cluster in a crystal structure. It exhibits superior thermal stability, good water-stability, and even insensitivity to the existence of acid and base within a certain range of pH values. Furthermore, it performs as a heterogeneous crystalline Lewis acid catalyst with good activity for the conversion of long-chain fatty acids rather than short-chain ones, and high recycling efficiency for esterification reaction of fatty acids with alcohols to produce biodiesel. PMID:24019078

Du, Dong-Ying; Qin, Jun-Sheng; Sun, Zhong; Yan, Li-Kai; O'Keeffe, Michael; Su, Zhong-Min; Li, Shun-Li; Wang, Xiao-Hong; Wang, Xin-Long; Lan, Ya-Qian

2013-01-01

301

FEASIBILITY STUDY TO PRODUCE BIODIESEL FROM LOW COST OILS AND NEW CATALYSTS DERIVED FROM AGRICULTURAL & FORESTRY RESIDUES - PHASE I  

EPA Science Inventory

This research will develop and demonstrate the feasibility of preparing reusable and recoverable solid, porous acid and base catalysts for biodiesel production using activated carbon generated from agricultural and forestry residues (i.e., a sustainable biomass).  These ne...

302

Effect of catalyst diameter on vapour-liquid-solid growth of GaAs nanowires  

NASA Astrophysics Data System (ADS)

GaAs nanowires were grown on (111)B GaAs substrates using the vapour-liquid-solid mechanism. The Au/Pt nanodots used to catalyse wire growth were defined lithographically and had varying diameter and separation. An in-depth statistical analysis of the resulting nanowires, which had a cone-like shape, was carried out. This revealed that there were two categories of nanowire present, with differing height and tapering angle. The bimodal nature of wire shape was found to depend critically on the diameter of the Au-Ga droplet atop the nanowire. Transmission electron microscopy analysis also revealed that the density of stacking faults in the wires varied considerably between the two categories of wire. It is believed that the cause of the distinction in terms of shape and crystal structure is related to the contact angle between the droplet and the solid-liquid interface. The dependency of droplet diameter on contact angle is likely related to line-tension, which is a correction to Young's equation for the contact angle of a droplet upon a surface. The fact that contact angle may influence resulting wire structure and shape has important implications for the planning of growth conditions and the preparation of wires for use in proposed devices.

O'Dowd, B. J.; Wojtowicz, T.; Rouvimov, S.; Liu, X.; Pimpinella, R.; Kolkovsky, V.; Wojciechowski, T.; Zgirski, M.; Dobrowolska, M.; Shvets, I. V.; Furdyna, J.

2014-08-01

303

Controlling Axial p-n Heterojunction Abruptness Through Catalyst Alloying in Vapor-Liquid-Solid Grown Semiconductor Nanowires  

SciTech Connect

The p-n junction can be regarded as the most important electronic structure that is responsible for the ubiquity of semiconductor microelectronics today. Efforts to continually scale down the size of electronic components is guiding research to explore the use of nanomaterials synthesized from a bottom-up approach - group-IV semiconductor nanowires being one such material. However, Au-catalyzed synthesis of Si/Si1-x-Gex semiconductor nanowire heterojunctions using the commonly-used vapor-liquid-solid (VLS) growth technique results in diffuse heterojunction interfaces [1], leading to doubts of producing compositionally-sharp p-n junctions using this approach. However, we have recently reported the ability to increase Ge-Si nanowire heterojunction abruptness by VLS synthesis from a Au(1-x)Ga(x) catalyst alloy as shown by EDX analysis in an SEM [2]. In this work, we have extended the use of a AuGa catalyst alloy to produce more compositionally abrupt p-n junction interfaces compared to using pure Au as directly measured by atom probe tomography. As shown in Figure 1(a-b), individual Ge-Si heterostructured nanowires were grown vertically atop Ge(111) microposts. Direct growth on the microposts provides a facile approach to nanowire analysis which circumvents the need to use FIB-based sample preparation techniques. Both nanowires grown from pure Au and a AuGa catalyst alloy were analyzed. The corresponding 3D APT reconstruction of an individual heterostructured nanowire is shown in Figure 1(c) with the corresponding materials labeled. A 1-dimensional composition profile along the analysis direction in Figure 1(d) confirms an increase in heterojunction abruptness for nanowires grown from AuGa (~10nm) compared to nanowires grown from pure Au (~65nm). Analysis of the P distribution within the Si region (Figure 1(e)) indicates that P reaches a constant distribution over approximately 10nm when incorporated through the AuGa catalyst, whereas it continually increases over 100’s of nanometers when incorporated through pure Au. The apparent lower overall P concentration within the nanowire grown from the AuGa alloy suggests that the solubility of P in the alloy is lower compared to pure Au. The ability to controllably increase nanowire p-n junction abruptness is important for nanowire applications as solar cells and tunneling field effect transistors where an increase in device performance is expected from shaper p-n junction interfaces. [1] T.E. Clark et al., Nano Lett. 8 (2008) 1246. [2] D.E. Perea et al., Nano Lett. 11 (2011) 3117. [3] The research was supported through the user program at both the Center for Integrated Nanotechnologies at Los Alamos National Laboratory and the Environmental Molecular Sciences Laboratory at Pacific Northwest National Laboratory.

Perea, Daniel E.; Schreiber, Daniel K.; Devaraj, Arun; Thevuthasan, Suntharampillai; Yoo, Jinkyoung; Dayeh, Shadi A.; Picraux, Samuel T.

2012-07-30

304

Nanoporous TiO 2-supported bimetallic catalysts for methanol oxidation in acidic media  

Microsoft Academic Search

New dynamic aspects of the catalysis of methanol oxidation reaction have been studied. The submonolayer films of bi-functional catalysts (PtRu) were deposited on novel nanostructured supporting materials, designed with the goal of achieving high variability of their electronic and chemical properties to influence the catalytic activity of sub-monolayer catalyst. The mesoscopic TiO2 supporting film formation was investigated using EQCN, voltammetric,

Maria Hepel; Indee Kumarihamy; C. J. Zhong

2006-01-01

305

Temperature-Controlled Catalyst Recycling: New Protocols Based upon Temperature-Dependent Solubilities of Fluorous Compounds and Solid\\/Liquid Phase Separations  

Microsoft Academic Search

The absolute solubilities of fluorous compounds can be tailored by varying the lengths of the (CF2)\\u000a n?1CF3 (Rfn\\u000a )\\u000a segments. Many such compounds exhibit immense solubility increases in organic solvents or neat liquid reactants\\u000a upon heating. Suitably designed fluorous catalysts can therefore be employed under homogeneous conditions\\u000a at elevated temperatures, and recovered by solid\\/liquid phase separation at lower temperatures. Expensive

John A. Gladysz; Verona Tesevic

306

Characterization of the Ni-ScSZ anode with a LSCM–CeO 2 catalyst layer in thin film solid oxide fuel cell running on ethanol fuel  

Microsoft Academic Search

Solid oxide fuel cell (SOFC) running directly on hydrocarbon fuels has attracted much attention in recent years. In this paper, a dual-layer structure anode running on ethanol is fabricated by tape casting and screen-printing method, the addition of a LSCM–CeO2 catalyst layer to the supported anode surface yields better performance in ethanol fuel. The effect that the synthesis conditions of

Bo Huang; Xin-jian Zhu; Wan-qi Hu; Yun-yun Wang; Qing-chun Yu

2010-01-01

307

Friedel–Crafts acylation and related reactions catalysed by heteropoly acids  

Microsoft Academic Search

Recent studies on catalysis by heteropoly acids (HPA) for the Friedel–Crafts acylation of arenes and related Fries rearrangement of aryl esters are reviewed. It is demonstrated that HPA-based solid acids are efficient and environmentally friendly catalysts for these reactions, usually superior in activity to the conventional acid catalysts such as H2SO4 or zeolites.

I. V. Kozhevnikov

2003-01-01

308

A unique quinolineboronic acid-based supramolecular structure that relies on double intermolecular B-N bonds for self-assembly in solid state and in solution  

PubMed Central

The boronic acid functional group plays very important roles in sugar recognition, catalysis, organic synthesis, and supramolecular assembly. Therefore, understanding the unique properties of this functional group is very important. 8-Quinolineboronic acid (8-QBA) is found to be capable of self-assembling in solid state through a unique intermolecular B-N bond mechanism reinforced by intermolecular boronic anhydride formation, ?-? stacking, and hydrogen bond formation. NMR NOE and diffusion studies indicate that intermolecular B-N interaction also exists in solution with 8-QBA. In contrast, a positional isomer of 8-QBA, 5-quinolineboronic acid (5-QBA) showed very different behaviors in crystal packing and in solution and therefore different supramolecular network. Understanding the structural features of this unique 8-QBA assembly could be very helpful for the future design of new sugar sensors, molecular catalysts, and supramolecular assemblies. PMID:18414645

Zhang, Yanling; Li, Minyong; Chandrasekaran, Sekar; Gao, Xingming; Fang, Xikui; Lee, Hsiau-Wei; Hardcastle, Kenneth; Yang, Jenny; Wang, Binghe

2007-01-01

309

Physical stability of spray dried solid dispersions of amorphous tolfenamic acid and polyvinylpyrolidone K30  

E-print Network

PHYSICAL STABILITY OF SPRAY DRIED SOLID DISPERSIONS OF AMORPHOUS TOLFENAMIC ACID AND POLYVINYLPYRROLIDONE K-30 Pia Thybo The Danish University of Pharmaceutical Sciences Copenhagen, Denmark GPEN October 2006 Side 2 Pia Thybo The Danish University...

Thybo, Pia

2006-10-25

310

Synthesis of trifluoromethyl-imines by solid acid\\/superacid catalyzed microwave assisted approach  

Microsoft Academic Search

A new solid acid\\/superacid catalyzed microwave assisted synthesis of trifluoromethyl-imines is described. Various ?,?,?-trifluoromethylketones react readily with primary amines to produce the corresponding imines. Two different strategies have been employed; one is the application of microwave irradiation coupled with solvent-free solid acid catalysis. The other method, for highly deactivated substrates includes the use of a pressure vessel at 175°C temperature,

Mohammed Abid; Markku Savolainen; Shainaz Landge; Jinbo Hu; G. K. Surya Prakash; George A. Olah; Béla Török

2007-01-01

311

Hydrocracking catalyst  

Microsoft Academic Search

The invention relates to a particular method for the preparation of a hydrocracking catalyst, using a high iron content bauxite as a basis. This bauxite is ground and screened to a specific size and mixed with three types of additives: a promoter additive of the P, Mo, Co, Ni, W type. A hardener additive of the phosphoric acid type, ammonium

B. Arias; R. Galiasso; H. Kum

1985-01-01

312

Copper-exchanged mordenites as active catalysts for NO selective catalytic reduction by propene under oxidising conditions: Effect of Si\\/Al ratio, copper content and Brönsted acidity  

Microsoft Academic Search

CuMOR catalysts with different Si\\/Al ratios and copper contents, prepared from the acid and sodium forms, were studied in NO reduction with propene in the presence of excess oxygen. It was observed that the influence of zeolite Si\\/Al ratio on CuMOR catalytic activity for NO SCR by propene depends on the catalyst copper content, the reverse being also true. For

C. Torre-Abreu; M. F. Ribeiro; C. Henriques; F. R. Ribeiro

1997-01-01

313

Suzuki–Miyaura cross-coupling reaction of 1-aryltriazenes with arylboronic acids catalyzed by a recyclable polymer-supported N-heterocyclic carbene–palladium complex catalyst  

PubMed Central

Summary The Suzuki–Miyaura cross-coupling reaction of 1-aryltriazenes with arylboronic acids catalyzed by a recyclable polymer-supported Pd–NHC complex catalyst has been realized for the first time. The polymer-supported catalyst can be re-used several times still retaining high activity for this transformation. Various aryltriazenes were investigated as electrophilic substrates at room temperature to give biaryls in good to excellent yields and showed good chemoselectivity over aryl halides in the reactions. PMID:20703375

Nan, Guangming; Ren, Fang

2010-01-01

314

New chitosan microspheres supported [bis(2-methylallyl)(1,5-cyclooctadienne)ruthenium(II)] as efficient catalysts for colour degradation in the presence of hydrogen peroxide  

Microsoft Academic Search

This paper concerns the immobilisation of either [bis(2-methylallyl)(1,5-cyclooctadienne)ruthenium(II)] (I) or ruthenium chloride (RuCl3) (II) on chitosan microspheres (catalyst I and catalyst II, respectively). These heterogenised catalysts were used for the oxidative degradation of two acid dyes, i.e. [Calmagite (Calma) and Acid Blue 25 (AB25)] in aqueous solution at pH 7.0 in the presence of hydrogen peroxide (H2O2). Prepared solid supports

Mahjoub Jabli; Ridha Touati; Yakdhane Kacem; Bechir Ben Hassine

2012-01-01

315

New chitosan microspheres supported [bis(2-methylallyl)(1,5-cyclooctadienne)ruthenium(II)] as efficient catalysts for colour degradation in the presence of hydrogen peroxide  

Microsoft Academic Search

This paper concerns the immobilisation of either [bis(2-methylallyl)(1,5-cyclooctadienne)ruthenium(II)] (I) or ruthenium chloride (RuCl3) (II) on chitosan microspheres (catalyst I and catalyst II, respectively). These heterogenised catalysts were used for the oxidative degradation of two acid dyes, i.e. [Calmagite (Calma) and Acid Blue 25 (AB25)] in aqueous solution at pH 7.0 in the presence of hydrogen peroxide (H2O2). Prepared solid supports

Mahjoub Jabli; Ridha Touati; Yakdhane Kacem; Bechir Ben Hassine

2011-01-01

316

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

PubMed

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. PMID:16870333

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

2007-01-01

317

Preparation and characterizations of highly dispersed carbon supported PdxPty/C catalysts by a modified citrate reduction method for formic acid electrooxidation  

NASA Astrophysics Data System (ADS)

Carbon supported PdxPty/C (atomic ratio x:y from 1:1 to 6:1) have been prepared by a modified citrate reduction method assisted by inorganic stabilizers. Without using high molecular capping agents as stabilizers, the PdxPty/C catalysts are highly dispersed on the carbon support and no particle aggregations are found for the PdxPty/C catalysts. X-ray photoelectron spectroscopy reveals either Pt or Pd segregation for the PdxPty/C catalysts depending on Pd/Pt atomic ratio. CO stripping in 0.5 M H2SO4 and repeated formic acid oxidation cyclic voltammetry in 0.5 M HCHO + 0.5 M H2SO4 have been conducted to test out the CO tolerance and stability of the catalysts, respectively. It has been found that, with the increase of Pd/Pt atomic ratio, the CO stripping peak potential increases (less CO tolerant), whereas the catalyst stability towards formic acid oxidation decreases. The as-prepared catalysts reveal excellent mass-normalized formic acid oxidation activity as compared with published results possibly due to high dispersion and the absence of high molecular capping agents.

Li, Zuopeng; Li, Muwu; Han, Mingjia; Zeng, Jianhuang; Li, Yuexia; Guo, Yanqin; Liao, Shijun

2014-05-01

318

Mechanisms of catalyst deactivation  

Microsoft Academic Search

The literature treating mechanisms of catalyst deactivation is reviewed. Intrinsic mechanisms of catalyst deactivation are many; nevertheless, they can be classified into six distinct types: (i) poisoning, (ii) fouling, (iii) thermal degradation, (iv) vapor compound formation accompanied by transport, (v) vapor-solid and\\/or solid-solid reactions, and (vi) attrition\\/crushing. As (i), (iv), and (v) are chemical in nature and (ii) and (v)

Calvin H Bartholomew

2001-01-01

319

The Catalytic Cracking of Hydrocarbons in a Riser Simulator: The Effect of Catalyst Accessibility and Acidity  

E-print Network

1 The Catalytic Cracking of Hydrocarbons in a Riser Simulator: The Effect of Catalyst Accessibility-zeolites as main component and on ZSM-5 as additive. These zeolites are bounded individually in a spray-dried the catalytic cracking of 1,3,5-TIPB was #12;3 carried out in other study using the riser

Al-Khattaf, Sulaiman

320

An evaluation of Pt sulfite acid (PSA) as precursor for supported Pt catalysts  

E-print Network

upon impregnation, calcination, and reduction. While all catalysts show retention of some S, reasonably (niobia and silica) display some storage of S even while only Pt-O bands are observed after calcination or reoxidation. More sulfur was eliminated by high temperature calcinations followed by reduction in hydrogen

Regalbuto, John R.

321

Hydrodeoxygenation of bio-derived phenols to hydrocarbons using RANEY Ni and Nafion/SiO2 catalysts.  

PubMed

A simple, green, cost- and energy-efficient route for converting phenolic components in bio-oil to hydrocarbons and methanol has been developed, with nearly 100% yields. In the heterogeneous catalysts, RANEY Ni acts as the hydrogenation catalyst and Nafion/SiO(2) acts as the Brønsted solid acid for hydrolysis and dehydration. PMID:20066309

Zhao, Chen; Kou, Yuan; Lemonidou, Angeliki A; Li, Xuebing; Lercher, Johannes A

2010-01-21

322

Clay Minerals as Solid Acids and Their Catalytic Properties.  

ERIC Educational Resources Information Center

Discusses catalytic properties of clays, attributed to acidity of the clay surface. The formation of carbonium ions on montmorillonite is used as a demonstration of the presence of surface acidity, the enhanced dissociation of water molecules when polarized by cations, and the way the surface can interact with organic substances. (Author/JN)

Helsen, J.

1982-01-01

323

Utilisation of fruits waste for citric acid production by solid state fermentation  

Microsoft Academic Search

A solid state fermentation method was used to utilise pineapple, mixed fruit and maosmi waste as substrates for citric acid production using Aspergillus niger DS 1. Experiments were carried out in the presence and absence of methanol at different moisture levels. In the absence of methanol the maximum citric acid was obtained at 60% moisture level whereas in the presence

D. Kumar; V. K. Jain; G. Shanker; A. Srivastava

2003-01-01

324

Rheology of dilute acid hydrolyzed corn stover at high solids concentration.  

PubMed

The rheological properties of acid hydrolyzed corn stover at high solids concentration (20-35 wt.%) were investigated using torque rheometry. These materials are yield stress fluids whose rheological properties can be well represented by the Bingham model. Yield stresses increase with increasing solids concentration and decrease with increasing hydrolysis reaction temperature, acid concentration, and rheometer temperature. Plastic viscosities increase with increasing solids concentration and tend to decrease with increasing reaction temperature and acid concentration. The solids concentration dependence of the yield stress is consistent with that reported for other fibrous systems. The changes in yield stress with reaction conditions are consistent with observed changes in particle size. This study illustrates that torque rheometry can be used effectively to measure rheological properties of concentrated biomass. PMID:19333558

Ehrhardt, M R; Monz, T O; Root, T W; Connelly, R K; Scott, C T; Klingenberg, D J

2010-02-01

325

One-Pot Synthesis of Graphene-Supported Monodisperse Pd Nanoparticles as Catalyst for Formic Acid Electro-oxidation  

NASA Astrophysics Data System (ADS)

To synthesize monodisperse palladium nanoparticles dispersed on reduced graphene oxide (RGO) sheets, we have developed an easy and scalable solvothermal reduction method from an organic solution system. The RGO-supported palladium nanoparticles with a diameter of 3.8 nm are synthesized in N-methyl-2-pyrrolidone (NMP) and in the presence of oleylamine and trioctylphosphine, which facilitates simultaneous reduction of graphene oxide and formation of Pd nanocrystals. So-produced Pd/RGO was tested for potential use as electrocatalyst for the electro-oxidation of formic acid. Pd/RGO catalyzes formic acid oxidation very well compared to Pd/Vulcan XC-72 catalyst. This synthesis method is a new way to prepare excellent electrocatalysts, which is of great significance in energy-related catalysis.

Yang, Sudong; Dong, Jing; Yao, Zhaohui; Shen, Chengmin; Shi, Xuezhao; Tian, Yuan; Lin, Shaoxiong; Zhang, Xiaogang

2014-03-01

326

One-pot synthesis of graphene-supported monodisperse Pd nanoparticles as catalyst for formic acid electro-oxidation.  

PubMed

To synthesize monodisperse palladium nanoparticles dispersed on reduced graphene oxide (RGO) sheets, we have developed an easy and scalable solvothermal reduction method from an organic solution system. The RGO-supported palladium nanoparticles with a diameter of 3.8?nm are synthesized in N-methyl-2-pyrrolidone (NMP) and in the presence of oleylamine and trioctylphosphine, which facilitates simultaneous reduction of graphene oxide and formation of Pd nanocrystals. So-produced Pd/RGO was tested for potential use as electrocatalyst for the electro-oxidation of formic acid. Pd/RGO catalyzes formic acid oxidation very well compared to Pd/Vulcan XC-72 catalyst. This synthesis method is a new way to prepare excellent electrocatalysts, which is of great significance in energy-related catalysis. PMID:24675779

Yang, Sudong; Dong, Jing; Yao, Zhaohui; Shen, Chengmin; Shi, Xuezhao; Tian, Yuan; Lin, Shaoxiong; Zhang, Xiaogang

2014-01-01

327

One-Pot Synthesis of Graphene-Supported Monodisperse Pd Nanoparticles as Catalyst for Formic Acid Electro-oxidation  

PubMed Central

To synthesize monodisperse palladium nanoparticles dispersed on reduced graphene oxide (RGO) sheets, we have developed an easy and scalable solvothermal reduction method from an organic solution system. The RGO-supported palladium nanoparticles with a diameter of 3.8?nm are synthesized in N-methyl-2-pyrrolidone (NMP) and in the presence of oleylamine and trioctylphosphine, which facilitates simultaneous reduction of graphene oxide and formation of Pd nanocrystals. So-produced Pd/RGO was tested for potential use as electrocatalyst for the electro-oxidation of formic acid. Pd/RGO catalyzes formic acid oxidation very well compared to Pd/Vulcan XC-72 catalyst. This synthesis method is a new way to prepare excellent electrocatalysts, which is of great significance in energy-related catalysis. PMID:24675779

Yang, Sudong; Dong, Jing; Yao, Zhaohui; Shen, Chengmin; Shi, Xuezhao; Tian, Yuan; Lin, Shaoxiong; Zhang, Xiaogang

2014-01-01

328

Heteropoly compounds as solid-phase catalysts in the processes of actinide ion reduction with hydrazine in HNO{sub 3} solutions  

SciTech Connect

Addition of a catalyst, a heterpoly compound (HPC) of the 12th series, in a hydrazine-containing Pu(IV) or Np(V) solution sharply accelerates reduction of these actinides to Pu(III) and Np(IV), respectively. These reactions are irreversible first-order processes. The reaction constant increases linearly as the ratio between the weight of the solid phase and the volume of the liquid phase increases. With increasing the HPC amount on the support the reaction rate increases. Cs{sub 5}P{sub 2}Mo{sub 10}O{sub 40} supported on silica gel was found to be the best catalyst. The activation energy of reduction of Pu(IV) to Pu(III) is about 80 kJ mole{sup {minus}1}. The mechanism of catalytic reactions in the presence of HPC is supposed to consist in the accumulation of heteropoly blue immediately reduces actinide ions.

Fedoseev, A.M.; Tananaev, I.G. [Institute of Physical Chemistry, Moscow (Russian Federation)

1995-01-01

329

H-Gallosilicate (MFI) Propane Aromatization Catalyst: Influence of Si\\/Ga Ratio on Acidity, Activity and Deactivation Due to Coking  

Microsoft Academic Search

Influence of bulk Si\\/Ga ratio of H-gallosilicate (MFI) on its degalliation (during calcination for removal of template and deammoniation of NH4form), acidity\\/acid strength distribution (measured by stepwise thermal desorption and chemisorption of pyridine at 50–400°C using GC techniques and also by acid catalyzed model reactions viz. iso-octane cracking and toluene disproportionation) and initial activity\\/product selectivity and catalyst deactivation in propane

V. R. Choudhary; A. K. Kinage; C. Sivadinarayana; P. Devadas; S. D. Sansare; M. Guisnet

1996-01-01

330

Reaction of carboxylic acids with vinyl ethers under solvent-free conditions using molecular iodine as a catalyst.  

PubMed

The reaction of vinyl ethers with carboxylic acids using iodine as a catalyst under solvent-free conditions was investigated. The reaction of saturated carboxylic acids with vinyl ethers gave the corresponding esters. Mechanistic studies revealed the production of the adduct of the vinyl ether with the carboxylic acid, which then rearranged to form the ester. At low temperatures, the reaction of 2-(1-hydroxycyclohexyl)acetic acid (1) and butyl vinyl ether yielded a butyl ester. However, at a reaction temperature of 80°C, both the esterification and the elimination of a water molecule occurred, yielding the unsaturated butyl ester butyl 2-cyclohexenylacetate. The reaction of 2-((1S,2S,4R)-2-hydroxy-1,7,7-trimethylbicyclo[2.2.1]heptan-2-yl)acetic acid (12) with butyl vinyl ether at low temperatures resulted in a mixture of four compounds. However, similar to the high-temperature (>60°C) reaction of 1, the esterification was accompanied by the elimination of a water molecule to give the unsaturated butyl ester (E)-butyl 2-((1S,4R)-1,7,7-trimethylbicyclo[2.2.1]heptan-2-ylidene)acetate. While a ?-hydrogen was abstracted to form the endo-type double bond in the reaction of 1, an ?-hydrogen was abstracted to form the exo-type double bond in the reaction of 12. PMID:23357815

Hanzawa, Yohko; Kasashima, Yoshio; Hashimoto, Kahoko; Sasaki, Tatsuhiro; Tomisaki, Keita; Mino, Takashi; Sakamoto, Masami; Fujita, Tsutomu

2013-01-01

331

An easy-to-use heterogeneous promoted zirconia catalyst for Knoevenagel condensation in liquid phase under solvent-free conditions  

Microsoft Academic Search

Knoevenagel condensation of various aliphatic, aromatic and heterocyclic aldehydes with malononitrile was carried out in the liquid phase in one step by employing a sulfate-ion promoted zirconia solid acid catalyst. This catalyst facilitates the reaction under solvent-free conditions at moderate temperatures providing excellent yields of the products. The sulfate-ion promoted zirconia catalyst was synthesized by immersing a finely powdered hydrous

Benjaram M. Reddy; Meghshyam K. Patil; Komateedi N. Rao; Gunugunuri K. Reddy

2006-01-01

332

Heterogeneous base catalysts for edible palm and non-edible Jatropha-based biodiesel production  

PubMed Central

Background Transesterification catalyzed by solid base catalyst is a brilliant technology for the noble process featuring the fast reaction under mild reacting condition in biodiesel production. Heterogeneous base catalysts are generally more reactive than solid acid catalysts which require extreme operating condition for high conversion and biodiesel yield. In the present study, synthesis of biodiesel was studied by using edible (palm) or non-edible (Jatropha) feedstock catalyzed by heterogeneous base catalysts such as supported alkali metal (NaOH/Al2O3), alkaline-earth metal oxide (MgO, CaO and SrO) and mixed metal oxides catalysts (CaMgO and CaZnO). Results The chemical characteristic, textural properties, basicity profile and leaching test of synthesized catalysts were studied by using X-ray diffraction, BET measurement, TPD-CO2 and ICP-AES analysis, respectively. Transesterification activity of solid base catalysts showed that?>?90% of palm biodiesel and?>?80% of Jatropha biodiesel yield under 3 wt.% of catalyst, 3 h reaction time, methanol to oil ratio of 15:1 under 65°C. This indicated that other than physicochemical characteristic of catalysts; different types of natural oil greatly influence the catalytic reaction due to the presence of free fatty acids (FFAs). Conclusions Among the solid base catalysts, calcium based mixed metal oxides catalysts with binary metal system (CaMgO and CaZnO) showed capability to maintain the transesterification activity for 3 continuous runs at?~?80% yield. These catalysts render high durability characteristic in transesterification with low active metal leaching for several cycles. PMID:24812574

2014-01-01

333

Synthesis, Structure, and Properties of a Mixed-Valent Triiron Complex of Tetramethyl Reductic Acid, an Ascorbic Acid Analog, and its Relationship to a Functional Non-Heme Iron Oxidation Catalyst System  

PubMed Central

The purple triiron(II,III,III) complex, [Fe3Cl2(TMRASQ)4(HTMRA)2]·C5H12 (1·C5H12), where H2(TMRA) is tetramethyl reductic acid, 4,4,5,5-tetramethyl-2,3-dihydroxy-2-cyclopenten-1-one, and H(TMRASQ) is the semiquinone form of this ligand, was prepared from (Et4N)2[Fe2OCl6] and H2(TMRA) and characterized by X-ray crystallography, Mössbauer spectroscopy, and redox titrations. The physical properties of the complex in solution are consistent with its mixed-valent character, as delineated by a solid-state structure analysis. Assignments of the iron and ligand oxidation states in the crystal were made on the basis of a valence bond sum analysis and the internal ligand geometry. As the first well-characterized iron complex of an ascorbic acid H2(AA) analog, 1 provides insight into the possible coordination geometry of the family of complexes containing H2AA and its analogues. In the presence of air and H2TMRA, 1 is able to catalyze the oxidation of cyclohexane to cyclohexanol with remarkable selectivity, but the nature of the true catalyst remains unknown. PMID:17579400

Kim, YooJin; Feng, Xudong; Lippard, Stephen J.

2011-01-01

334

Esterification of sodium 4-hydroxybenzoate by ultrasound-assisted solid-liquid phase-transfer catalysis using dual-site phase-transfer catalyst.  

PubMed

The catalytic esterification of sodium 4-hydroxybenzoate with benzyl bromide by ultrasound-assisted solid-liquid phase-transfer catalysis (U-SLPTC) was investigated using the novel dual-site phase-transfer catalyst 4,4'-bis(tributylammoniomethyl)-1,1'-biphenyl dichloride (BTBAMBC), which was synthesized from the reaction of 4,4'-bis(chloromethyl)-1,1'-biphenyl and tributylamine. Without catalyst and in the absence of water, the product yield at 60 °C was only 0.36% in 30 min of reaction even under ultrasound irradiation (28 kHz/300 W) and 250 rpm of stirring speed. When 1cm(3) of water and 0.5 mmol of BTBAMBC were added, the yield increased to 84.3%. The catalytic intermediate 4,4'-bis(tributylammoniomethyl)-1,1'-biphenyl di-4-hydroxybenzoate was also synthesized to verify the intrinsic reaction which was mainly conducted in the quasi-aqueous phase locating between solid and organic phases. Pseudo-first-order kinetic equation was used to correlate the overall reaction, and the apparent rate coefficient with ultrasound (28 kHz/300 W) was 0.1057 min(-1), with 88% higher than that (0.0563 min(-1)) without ultrasound. The esterification under ultrasonic irradiation using BTBAMBC by solid-liquid phase-transfer catalysis was developed. PMID:23972326

Yang, Hung-Ming; Chu, Wei-Ming

2014-01-01

335

Microwave-assisted oxidative coupling of amines to imines on solid acid catalysts  

Microsoft Academic Search

A K-10 montmorillonite catalyzed microwave-assisted oxidative coupling of amines is described. Substituted benzylamines readily undergo self-coupling reactions to produce benzylidene–benzylamines, while aliphatic amines and anilines cannot form self-coupled products. A mixture of a benzylamine and an aniline or aliphatic amine, respectively, effectively, and selectively produces mixed imines, such as benzylidene–anilines and benzylidene–alkylamines.

Shainaz M. Landge; Valentina Atanassova; Muralidhara Thimmaiah; Béla Török

2007-01-01

336

ADSORPTION/DESORPTION STUDIES ON SOLID ACID ALKYLATION CATALYSTS USING A TAPERED ELEMENT OSCILLATING MICROBALANCE (TEOM)  

E-print Network

four times more active than SiO2-supported Nafion while providing > 80% C 80% C8 alkylates selectivity for the process to be economically viable. A tapered element oscillating microbalance (TEOM) was used to elucidate for the first time the adsorption...

Gong, Kening

2008-10-23

337

Activated carbons treated with sulphuric acid: Catalysts for catalytic wet peroxide oxidation  

Microsoft Academic Search

Different liquid phase thermal treatments were applied to a commercial activated carbon (Norit ROX 0.8) in order to produce modified activated carbons with varying surface chemistry and increased acidic character. Chemical characterization of the prepared materials includes determination of the point of zero charge and evaluation of the concentration and nature of acidic and basic surface functionalities by acid\\/base titrations

Helder T. Gomes; Sandra M. Miranda; Maria J. Sampaio; Adrián M. T. Silva; Joaquim L. Faria

2010-01-01

338

System for reactivating catalysts  

DOEpatents

A method of reactivating a catalyst, such as a solid catalyst or a liquid catalyst is provided. The method comprises providing a catalyst that is at least partially deactivated by fouling agents. The catalyst is contacted with a fluid reactivating agent that is at or above a critical point of the fluid reactivating agent and is of sufficient density to dissolve impurities. The fluid reactivating agent reacts with at least one fouling agent, releasing the at least one fouling agent from the catalyst. The at least one fouling agent becomes dissolved in the fluid reactivating agent and is subsequently separated or removed from the fluid reactivating agent so that the fluid reactivating agent may be reused. A system for reactivating a catalyst is also disclosed.

Ginosar, Daniel M. (Idaho Falls, ID); Thompson, David N. (Idaho Falls, ID); Anderson, Raymond P. (Idaho Falls, ID)

2010-03-02

339

Short communication Fabrication of solid lipid microcapsules containing ascorbic acid  

E-print Network

2013 Accepted 23 November 2013 Available online 1 December 2013 Keywords: Encapsulation Vitamin C Encapsulation efficiency Lipid shell a b s t r a c t The importance of ascorbic acid (AA) in the human diet has motivated food researchers to develop AA- fortified food products. However, this compound is very unstable

340

Tungsten oxide catalysts supported on activated carbons: effect of tungsten precursor and pretreatment on dispersion, distribution, and surface acidity of catalysts  

Microsoft Academic Search

Tungsten catalysts supported on activated carbon were prepared using tungsten hexacarbonyl, ammonium tungstate, and tungsten pentaethoxide. The catalysts were pretreated in He, dry air, or wet air at 623 K for 6 h before being characterized by N2 adsorption at 77 K, temperature-programmed desorption, X-ray diffraction, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy, and by testing their behavior in

A. F. Pérez-Cadenas; C. Moreno-Castilla; F. J. Maldonado-Hódar; J. L. G. Fierro

2003-01-01

341

Salicylato titanocene complexes as cooperative organometallic Lewis acid and Brønsted acid catalysts for three-component mannich reactions.  

PubMed

A binary acid system has been developed that features an air-stable organometallic precursor, titanocene dichloride, and simple organic cooperative Brønsted acids, which allowed for mild and highly efficient Mannich reactions of both aryl and alkyl ketones with excellent yields and satisfactory diastereoselectivity. Mechanistic studies, including (1) H?NMR titration, X-ray structure analyses as well as isolation of catalytically active species, elucidated the dramatic synergistic effects of this new binary acid system. PMID:24954651

Wu, Ya; Chen, Chun; Jia, Gai; Zhu, Xuyang; Sun, Huaming; Zhang, Guofang; Zhang, Weiqiang; Gao, Ziwei

2014-07-01

342

Molecular\\/electronic structure–surface acidity relationships of model-supported tungsten oxide catalysts  

Microsoft Academic Search

A series of model-supported WO3 catalysts were synthesized on preformed Al2O3, Nb2O5, TiO2, and ZrO2 supports by impregnation of aqueous ammonium metatungstate, (NH4)10W12O41?5H2O. The molecular and electronic structures of the supported tungsten oxide phases were determined with in situ Raman and UV–vis spectroscopy, respectively. The supported tungsten oxide structures are the same on all oxide supports as a function of

Taejin Kim; Andrew Burrows; Christopher J. Kiely; Israel E. Wachs

2007-01-01

343

Non-platinum group metal oxgyen reduction catalysts and their mechanism in both acid and alkaline media: The effect of the catalyst precursor and the ionomer on oxygen reduction  

NASA Astrophysics Data System (ADS)

Non-platinum catalysts are an attractive strategy for lowering the cost of fuel cells, but much more development is needed in order to replace platinum, especially at the cathode where oxygen is reduced. Research groups worldwide have donated material for a study in which precursor structure to catalyst activity correlations are made. The donated samples have been divided into three classes based on their precursor; macrocyclic chelates, small molecule, and polymeric precursors. The precursor is one activity-dictating factor among many, but it is one of the most influential. It was found that macrocyclic chelates on average produced the most active catalysts, having the highest limiting, diffusion-limited, kinetic, and exchange current densities, as well as the lowest overpotentials and H2O2 production. This suggests that the M-N4 atomic structure of the precursor remains largely static throughout heat treatment, as the M-Nx motif is the accepted active site conformation. The other classes were somewhat less active, but the breadth of precursor materials that range in structure and functionality, as well as low associated costs, make them attractive precursor materials. Careful precursor selection based on this analysis was applied to a new generation of catalyst derived from iron salt and 4-aminoantipyrine. An extensive investigation of the reduction of oxygen on the material performed in both acid and alkaline media, and it was found that reduction follows a two-step pathway. While the peroxide reducing step is also very fast, the first step is so rapid that, even at low active site density, the material is almost as active as platinum if all diffusion limitations are removed. In addition to bottom-up catalyst design, the catalyst:ionomer complex, by which catalyst is incorporated into the membrane electrode assembly, also affects reductive kinetics. A series of novel anionically conductive ionomers have been evaluated using a well-described cyanamide derived catalyst, and the ionomeric influence on activity was mechanistically evaluated. It was found that the water-uptake percentage of the ionomer and the ion exchange capacity has a major role in catalyzing the reaction. The ionomer content of the complex must balance ionic and electrical charge transfer, as well as manage a certain degree of hydration at the active site. In order for a catalyst to perform optimally in an operational fuel cell, design considerations must be addressed at the precursor, support, synthesis, morphological, and ionomer-complexing levels. If any level of design is neglected, catalytic performance will be sacrificed.

Robson, Michael H.

344

Scandium trifluoromethanesulfonate as an extremely active Lewis acid catalyst in acylation of alcohols with acid anhydrides and mixed anhydrides  

SciTech Connect

Scandium triflate catalyzes the acylation of alcohols with acid anhydrides or the esterification of alcohols by carboxylic acids in the presence of p-nitrobenzoic anhydrides. The catalytic activity of the scandium triflates is found to be quite high allowing the acylation of secondary and tertiary alcohols.

Ishihara, K.; Kubota, M.; Kurihara, H.; Yamamoto, H. [Nagoya Univ. (Japan)] [Nagoya Univ. (Japan)

1996-07-12

345

Sulfamic acid: a novel and efficient catalyst for the synthesis of aryl-14 H-dibenzo[ a. j]xanthenes under conventional heating and microwave irradiation  

Microsoft Academic Search

A simple and convenient procedure for the synthesis of aryl-14H-dibenzo[a.j]xanthenes is described through a one-pot condensation of ?-naphthol with aryl aldehydes in the presence of sulfamic acid as the catalyst in a solvent-free media using both conventional heating and microwave irradiation.

B. Rajitha; B. Sunil Kumar; Y. Thirupathi Reddy; P. Narsimha Reddy; N. Sreenivasulu

2005-01-01

346

Sulfamic acid as a cost-effective and recyclable catalyst for liquid Beckmann rearrangement, a green process to produce amides from ketoximes without waste  

Microsoft Academic Search

Sulfamic acid (H2NSO3H) has been proved to be an efficient and green catalyst for liquid Beckmann rearrangement of ketoxime in dried acetonitrile. The use of basic neutralization agent has been avoided in this system due to its intrinsic zwitterionic property. Thus it is a green process for preparation of amide from ketoxime without producing any waste.

Bo Wang; Yanlong Gu; Cheng Luo; Tao Yang; Liming Yang; Jishuan Suo

2004-01-01

347

Vanadium Recovery by Leaching in Spent Catalysts for Sulfuric Acid Production Recuperação do Vanádio Contido em Catalisadores Gastos na Produção de Ácido Sulfúrico  

Microsoft Academic Search

Sulfuric acid plants often need catalyst replacement in order to cope with process improvements, removal of broken pellets, dust and moisture damaged particles. This removed material can not be discarded because has high amounts of vanadium. According to the Brazilian Environmental Authority this material must be stored under specified conditions. This situation requires large storing areas potentially useful for other

JOSÉ LUÍS MAGNANI; GEORGE CURY KACHAN; NEWTON LIBANIO FERREIRA

348

Silica sulfuric acid: an efficient and reusable catalyst for the one-pot synthesis of 3,4-dihydropyrimidin-2(1 H)-ones  

Microsoft Academic Search

Silica sulfuric acid efficiently catalyzes the three-component Biginelli reaction between an aldehyde, a ?-dicarbonyl compound and urea or thiourea in refluxing ethanol to afford the corresponding dihydropyrimidinones in high yields. The catalyst is reusable and can be applied several times without any decrease in the yield of the reactions.

Peyman Salehi; Minoo Dabiri; Mohammad Ali Zolfigol; Mohammad Ali Bodaghi Fard

2003-01-01

349

A kinetic study of plutonium dioxide dissolution in hydrochloric acid using iron (II) as an electron transfer catalyst  

SciTech Connect

Effective dissolution of plutonium dioxide has traditionally been accomplished by contact with strong nitric acid containing a small amount of fluoride at temperatures of {approximately} 100 C. In spite of these aggressive conditions, PuO{sub 2} dissolution is sometimes incomplete requiring additional contact with the solvent. This work focused on an alternative to conventional dissolution in nitric acid where an electron transfer catalyst, Fe(II), was used in hydrochloric acid. Cyclic voltammetry was employed as an in-situ analytical technique for monitoring the dissolution reaction rate. The plutonium oxide selected for this study was decomposed plutonium oxalate with > 95% of the material having a particle diameter (< 70 {micro}m) as determined by a scanning laser microscopy technique. Attempts to dry sieve the oxide into narrow size fractions prior to dissolution in the HCl-Fe(II) solvent system failed, apparently due to significant interparticle attractive forces. Although sieve splits were obtained, subsequent scanning laser microscopy analysis of the sieve fractions indicated that particle segregation was not accomplished and the individual sieve fractions retained a particle size distribution very similar to the original powder assemblage. This phenomena was confirmed through subsequent dissolution experiments on the various screen fractions which illustrated no difference in kinetic behavior between the original oxide assemblage and the sieve fractions.

Fife, K.W.

1996-09-01

350

Unusual catalysts from molasses: synthesis, properties and application in obtaining biofuels from algae.  

PubMed

Acid catalysts were prepared by sulfonation of carbon materials obtained from the pyrolysis of sugar beet molasses, a cheap, viscous byproduct in the processing of sugar beets into sugar. Conditions for the pyrolysis of molasses (temperature and time) influenced catalyst performance; the best combination came from pyrolysis at low temperature (420 °C) for a relatively long time (8-15 h), which ensured better stability of the final material. The most effective molasses catalyst was highly active in the esterification of fatty acids with methanol (100 % yield after 3 h) and more active than common solid acidic catalysts in the transesterification of vegetable oils with 25-75 wt % of acid content (55-96 % yield after 8 h). A tandem process using a solid acid molasses catalyst and potassium hydroxide in methanol was developed to de-acidificate and transesterificate algal oils from Chlamydomonas reinhardtii, Nannochloropsis gaditana, and Phaeodactylum tricornutum, which contain high amounts of free fatty acids. The amount of catalyst required for the de-acidification step was influenced by the chemical composition of the algal oil, thus operational conditions were determined not only in relation to free fatty acids content in the oil, but according to the composition of the lipid extract of each algal species. PMID:22678658

Samorì, Chiara; Torri, Cristian; Fabbri, Daniele; Falini, Giuseppe; Faraloni, Cecilia; Galletti, Paola; Spera, Silvia; Tagliavini, Emilio; Torzillo, Giuseppe

2012-08-01

351

Encoding abrupt and uniform dopant profiles in vapor-liquid-solid nanowires by suppressing the reservoir effect of the liquid catalyst.  

PubMed

Semiconductor nanowires (NWs) are often synthesized by the vapor-liquid-solid (VLS) mechanism, a process in which a liquid droplet-supplied with precursors in the vapor phase-catalyzes the growth of a solid, crystalline NW. By changing the supply of precursors, the NW composition can be altered as it grows to create axial heterostructures, which are applicable to a range of technologies. The abruptness of the heterojunction is mediated by the liquid catalyst, which can act as a reservoir of material and impose a lower limit on the junction width. Here, we demonstrate that this "reservoir effect" is not a fundamental limitation and can be suppressed by selection of specific VLS reaction conditions. For Au-catalyzed Si NWs doped with P, we evaluate dopant profiles under a variety of synthetic conditions using a combination of elemental imaging with energy-dispersive X-ray spectroscopy and dopant-dependent wet-chemical etching. We observe a diameter-dependent reservoir effect under most conditions. However, at sufficiently slow NW growth rates (?250 nm/min) and low reactor pressures (?40 Torr), the dopant profiles are diameter independent and radially uniform with abrupt, sub-10 nm axial transitions. A kinetic model of NW doping, including the microscopic processes of (1) P incorporation into the liquid catalyst, (2) P evaporation from the catalyst, and (3) P crystallization in the Si NW, quantitatively explains the results and shows that suppression of the reservoir effect can be achieved when P evaporation is much faster than P crystallization. We expect similar reaction conditions can be developed for other NW systems and will facilitate the development of NW-based technologies that require uniform and abrupt heterostructures. PMID:25363730

Christesen, Joseph D; Pinion, Christopher W; Zhang, Xing; McBride, James R; Cahoon, James F

2014-11-25

352

Regiocontrolled intramolecular cyclizations of carboxylic acids to carbon-carbon triple bonds promoted by acid or base catalyst.  

PubMed

We systematically investigated, for the first time, the relationship between regioselectivity and acid/base effects in the cyclization reactions between carboxylic acids and carbon-carbon triple bonds. We found novel acid- and base-promoted cyclizations to selectively give isocoumarin or pyran-2(2H)-one and phthalide or furan-2(5H)-one skeletons, respectively, and established a catalytic version of regioselective heterocyclic ring synthesis. Density functional theory calculations and application to a short route to thunberginol A were also described. [reaction: see text]. PMID:17107061

Uchiyama, Masanobu; Ozawa, Hiroki; Takuma, Kazuya; Matsumoto, Yotaro; Yonehara, Mitsuhiro; Hiroya, Kou; Sakamoto, Takao

2006-11-23

353

Surface characteristics and electrochemical capacitances of carbon aerogels obtained from resorcinol and pyrocatechol using boric and oxalic acids as polymerization catalysts  

Microsoft Academic Search

Carbon aerogels were prepared by carbonizing (at 500–1500°C) organic aerogels obtained from the polymerization reaction of resorcinol and\\/or pyrocatechol with formaldehyde using boric and oxalic acids as polymerization catalysts. Prepared samples were characterized by different techniques to ascertain their composition, surface chemistry, morphology, and surface physics, determining their electrochemical capacitances in acidic medium. The use of pyrocatechol yielded carbon aerogels

Carlos Moreno-Castilla; Marta B. Dawidziuk; Francisco Carrasco-Marín; Zulamita Zapata-Benabithe

2011-01-01

354

Oxide acid-base reaction relating to the inhibition of vandium attack on REY zeolite catalysts. [Rare earth-exchanged yttrium  

Microsoft Academic Search

Certain materials, especially Sn, passivate the rare earth-exchanged Y zeolite (REY) used in petrochemical fluid-cracking catalysts against vanadium degradation caused by V impurities in the feed oil. The mechanism of passivation was investigated here from the standpoint of high-temperature oxide acid-base reaction; i.e., where the controlling factors were considered to be Lewis acid-base reactions between VâOâ, the RE oxides, SnOâ,

1991-01-01

355

Cu nanoclusters supported on nanocrystalline SiO?-MnO?: a bifunctional catalyst for the one-step conversion of glycerol to acrylic acid.  

PubMed

A material consisting of highly dispersed Cu nanoclusters anchored on nanocrystalline SiO2-MnO2 has been prepared, and was found to act as a bifunctional catalyst for the one-step conversion of glycerol to acrylic acid using H2O2. Under optimized conditions a glycerol conversion of 77.1%, with 74.7% selectivity for acrylic acid, was achieved after 30 h reaction time. PMID:25017454

Sarkar, Bipul; Pendem, Chandrashekar; Sivakumar Konathala, L N; Tiwari, Ritesh; Sasaki, Takehiko; Bal, Rajaram

2014-09-01

356

Narrow (n,m)-Distribution of Single-Walled Carbon Nanotubes Grown Using a Solid Supported Catalyst  

E-print Network

of distinct SWNT structures are formed in the HiPco process, in which disproportionation of CO into CO2:Mo molar ratio of 1:3. Before exposure to the CO feedstock, the catalyst was heated to 500 °C in a flow

Resasco, Daniel

357

Liquefaction with microencapsulated catalysts  

DOEpatents

A method of dispersing a liquefaction catalyst within coal or other carbonaceous solids involves providing a suspension in oil of microcapsules containing the catalyst. An aqueous solution of a catalytic metal salt is emulsified in the water-immiscible oil and the resulting minute droplets microencapsulated in polymeric shells by interfacial polycondensation. The catalyst is subsequently blended and dispersed throughout the powdered carbonaceous material to be liquefied. At liquefaction temperatures the polymeric microcapsules are destroyed and the catalyst converted to minute crystallites in intimate contact with the carbonaceous material.

Weller, Sol W. (Williamsville, NY)

1985-01-01

358

Polycationic ligands in gold catalysis: synthesis and applications of extremely ?-acidic catalysts.  

PubMed

Very often ligands are anionic or neutral species. Cationic ones are rare, and, when used, the positively charged groups are normally appended to the periphery of the ligand. Here, we describe a dicationic phosphine with no spacer between the phosphorus atom and the two positively charged groups. This structural feature makes its donor ability poorer than that of phosphites and only comparable to extremely toxic or pyrophoric compounds such as PF3 or P(CF3)3. By exploiting these properties, a new Au catalyst has been developed displaying a dramatically enhanced capacity to activate ?-systems. This has been used to synthesize very sterically hindered and naturally occurring 4,5-disubstituted phenanthrenes. The present approach is expected to be applicable to the development and improvement of many other transition metal catalyzed transformations that benefit from extremely strong ?-acceptor ligands. The mechanism of selected catalytic transformations has been explored by density functional calculations. PMID:24308636

Carreras, Javier; Gopakumar, Gopinadhanpillai; Gu, Lianghu; Gu, Liangu; Gimeno, Ana; Linowski, Pawel; Petuškova, Jekaterina; Thiel, Walter; Alcarazo, Manuel

2013-12-18

359

Alkylation of 1,3,5-trimethylbenzene with ?-butyrolactone over heteropolyacid catalysts  

Microsoft Academic Search

A Friedel–Crafts-type reaction of 1,3,5-trimethylbenzene with ?-butyrolactone was conducted over various solid acid catalysts such as zeolites, polymer resins, and heteropolyacids. The alkylation to 4-(2,4,6-trimethylphenyl) butyric acid proceeded exclusively with these catalysts; no acylation to the ketone occurred. The heteropolyacids, such as H3PW12O40 and H4SiW12O40, were superior in activity to the other catalysts; they also accelerated the reaction of the

Jianxin Mao; Yuichi Kamiya; Toshio Okuhara

2003-01-01

360

Solid acid proton conductors: from laboratory curiosities to fuel cell electrolytes  

E-print Network

Solid acid proton conductors: from laboratory curiosities to fuel cell electrolytes Sossina Ma The compound CsH2PO4 has emerged as a viable electrolyte for intermediate temperature (200­300 1C cells, in which a composite mixture of the electrolyte, Pt supported on carbon, Pt black and carbon

361

Activation of ZSM-5 catalysts  

SciTech Connect

Greatly increased yields of aromatics were obtainied in the reaction of ethanol over ZSM-5 zeolites if the protonated catalyst was pretreated in aqueous mineral acids or if hydrogen choloride or dichloroethane was added to the feed. The treated catalysts apparently contained less sodium than the ammonium-exchanged catalysts, and in some cases, some alumimum was removed. The product distributions at > 95% conversion were, e.g., 2% by wt benzene, 12% toluene, 24% xylenes, 34% trimethylbenzene, and 11% C/sub 10/+ aromatics from a catalyst treated in 0.6 M nitric acid, and 3% xylenes and 92% C/sub 10/+ aromatics from a catalyst treated in hydrofluoric acid.

Rajadhyaksha, R.A.; Anderson, J.R.

1980-06-01

362

Preparation and Evaluation of Advanced Catalysts for Phosphoric Acid Fuel Cells.  

National Technical Information Service (NTIS)

The platinum electrocatalysts were characterized for their crystallite sizes and the degree of dispersion on the carbon supports. One application of these electrocatalysts was for anodic oxidation of hydrogen in hot phosphoric acid fuel cells, coupled wit...

P. Stonehart, J. Baris, J. Hockmuth, P. Pagliaro

1984-01-01

363

Zymomonas mobilis As Catalyst for the Biotechnological Production of Sorbitol and Gluconic Acid  

Microsoft Academic Search

The conversion of glucose and fructose into gluconic acid (GA) and sorbitol (SOR) was conducted in a batch reactor with free\\u000a (CTAB-treated or not) or immobilized cells of Zymomonas mobilis. High yields (more than 90%) of gluconic acid and sorbitol were attained at initial substrate concentration of 600 g\\/L (glucose\\u000a plus fructose at 1:1 ratio), using cells with glucose-fructose-oxidoreductase activity

Gilmar Sidney Erzinger; Michele Vitolo

364

Zymomonas mobilis as catalyst for the biotechnological production of sorbitol and gluconic acid  

Microsoft Academic Search

The conversion of glucose and fructose into gluconic acid (GA) and sorbitol (SOR) was conducted in a batch reactor with free\\u000a (CTAB-treated or not) or immobilized cells of Zymomonas mobilis. High yields (more than 90%) of gluconic acid and sorbitol were attained at initial substrate concentration of 600 g\\/L (glucose\\u000a plus fructose at 1:1 ratio), using cells with glucose-fructose-oxidoreductase activity

Gilmar Sidney Erzinger; Michele Vitolo

2006-01-01

365

Zn(1.2)H(0.6)PW(12)O(40) Nanotubes with double acid sites as heterogeneous catalysts for the production of biodiesel from waste cooking oil.  

PubMed

Out of the frying pan: A ZnPW nanotube catalyst containing Brønsted and Lewis double acid sites promotes the conversion of waste cooking oil into biodiesel. The catalytic activity of the ZnPW nanotubes is stable to the presence of free fatty acids or water in the feedstock. The high catalytic activity of the ZnPW nanotubes is attributed to the synergistic effect of Lewis acid sites and Brønsted acid sites.Zinc dodecatungstophosphate (Zn(1.2)H(0.6)PW(12)O(40); ZnPW) nanotubes, which feature Lewis acid and Brønsted acid sites, were prepared using cellulose fibers as templates. The structure, acid properties, and catalytic activity of the nanotubes as heterogeneous catalysts for biodiesel production were then studied in detail. The ZnPW nanocatalyst exhibited higher catalytic activities for the simultaneous esterification and transesterification of palmitic acid than the parent acid catalyst 12-tungstophosphoric acid (H(3)PW(12)O(40)). Moreover, the doubly acidic nanotubes led to markedly enhanced yields of methyl esters in the conversion of waste cooking oil (containing 26.89 wt % free fatty acids and 1 % moisture) to biodiesel. The catalyst could be recycled and reused with negligible loss in activity over five cycles. The ZnPW nanocatalyst is acid- and water-tolerant and is an environmentally benign heterogeneous catalyst for the production of biodiesel from low-quality feedstocks. PMID:19191363

Li, Jing; Wang, Xiaohong; Zhu, Weimin; Cao, Fenghua

2009-01-01

366

Effect of carbon chain length on esterification of carboxylic acids with methanol using acid catalysis  

Microsoft Academic Search

This paper reports on an investigation into the impact of carboxylic acid chain length on the kinetics of liquid-phase acid-catalyzed esterification. Using sulfuric acid and a commercial Nafion\\/silica composite solid acid catalyst (SAC-13), initial kinetics were measured for the reactions of a series of linear chain carboxylic acids (acetic, propionic, butyric, hexanoic, and caprylic acid) with methanol at 60?°C. It

Yijun Liu; Edgar Lotero; James G. Goodwin

2006-01-01

367

3D-nanoarchitectured Pd/Ni catalysts prepared by atomic layer deposition for the electrooxidation of formic acid.  

PubMed

Three-dimensionally (3D) nanoarchitectured palladium/nickel (Pd/Ni) catalysts, which were prepared by atomic layer deposition (ALD) on high-aspect-ratio nanoporous alumina templates are investigated with regard to the electrooxidation of formic acid in an acidic medium (0.5 M H2SO4). Both deposition processes, Ni and Pd, with various mass content ratios have been continuously monitored by using a quartz crystal microbalance. The morphology of the Pd/Ni systems has been studied by electron microscopy and shows a homogeneous deposition of granularly structured Pd onto the Ni substrate. X-ray diffraction analysis performed on Ni and NiO substrates revealed an amorphous structure, while the Pd coating crystallized into a fcc lattice with a preferential orientation along the [220]-direction. Surface chemistry analysis by X-ray photoelectron spectroscopy showed both metallic and oxide contributions for the Ni and Pd deposits. Cyclic voltammetry of the Pd/Ni nanocatalysts revealed that the electrooxidation of HCOOH proceeds through the direct dehydrogenation mechanism with the formation of active intermediates. High catalytic activities are measured for low masses of Pd coatings that were generated by a low number of ALD cycles, probably because of the cluster size effect, electronic interactions between Pd and Ni, or diffusion effects. PMID:24605281

Assaud, Loïc; Monyoncho, Evans; Pitzschel, Kristina; Allagui, Anis; Petit, Matthieu; Hanbücken, Margrit; Baranova, Elena A; Santinacci, Lionel

2014-01-01

368

Advances in liquid-phase Friedel-Crafts acylation of aromatics catalyzed by heterogeneous solids  

Microsoft Academic Search

In the last few decades, significant improvements toward the development of environmentally benign processes have been achieved in the liquid-phase Friedel-Crafts acylation reactions. Many efforts have been devoted to the research on solid catalysts adequate to substitute homogeneous protonic acids or Lewis acids as traditionally employed catalysts in the acid-catalyzed Friedel-Crafts acylation processes. This short article describes the recent developments

Suman K. Jana

2006-01-01

369

Structural and electrochemical characterization of carbon supported Pt-Pr catalysts for direct ethanol fuel cells prepared using a modified formic acid method in a CO atmosphere.  

PubMed

Pt-Pr/C electrocatalysts were prepared using a modified formic acid method, and their activity for carbon monoxide and ethanol oxidation was compared to Pt/C. No appreciable alloy formation was detected by XRD analysis. By TEM measurements it was found that Pt particle size increases with an increasing Pr content in the catalysts and with decreasing metal precursor addition time. XPS measurements indicated Pt segregation on the catalyst surface and the presence of Pr2O3 and PrO2 oxides. The addition of Pr increased the electro-catalytic activity of Pt for both CO and CH3CH2OH oxidation. The enhanced activity of Pt-Pr/C catalysts was ascribed to both an electronic effect, caused by the presence of Pr2O3, and the bi-functional mechanism, caused by the presence of PrO2. PMID:23752757

Corradini, Patricia Gon; Antolini, Ermete; Perez, Joelma

2013-07-28

370

Effect of Periodic Water Addition on Citric Acid Production in Solid State Fermentation  

NASA Astrophysics Data System (ADS)

Water addition is one of the methods used to control the moisture loss in solid state fermentation (SSF). However, none of the studies report the timing of water addition and amount of water to be added in SSF. Therefore, this work was undertaken with an objective to evaluate the performance of periodic water addition on citric acid production in SSF. Experiments were conducted at different moistures (50-80 %) and temperatures (30-40 °C) to simulate the conditions in a fermenter. Citric acid production by Aspergillus niger (ATCC 9029) using sugarcane baggase was chosen as a model system. Based on the moisture profile, citric acid and sugar data, a strategy was designed for periodic addition of water. Water addition at 48, 96, 144 and 192 h enhanced the citric acid production by 62 % whereas water addition at 72, 120, and 168 h increased the citric acid production by just 17 %.

Utpat, Shraddha S.; Kinnige, Pallavi T.; Dhamole, Pradip B.

2013-09-01

371

Proton transfer reactions between nitric acid and acetone, hydroxyacetone, acetaldehyde and benzaldehyde in the solid phase.  

PubMed

The heterogeneous and homogeneous reactions of acetone, hydroxyacetone, acetaldehyde and benzaldehyde with solid nitric acid (HNO(3)) films have been studied with Reflection-Absorption Infrared Spectroscopy (RAIRS) under Ultra-High Vacuum (UHV) conditions in the 90-170 K temperature range. In the bulk or at the surface of the films, nitric acid transfers its proton to the carbonyl function of the organic molecules, producing protonated acetone-H(+), hydroxyacetone-H(+), acetaldehyde-H(+) and benzaldehyde-H(+), and nitrate anions NO(3)(-), a reaction not observed when nitric acid is previously hydrated [J. Lasne, C. Laffon and Ph. Parent, Phys. Chem. Chem. Phys., 2012, 14, 697]. This provides a molecular-scale description of the carbonyl protonation reaction in an acid medium, the first step of the acid-catalyzed condensation of carbonyl compounds, fuelling the growth of secondary organic aerosols (SOA) in the atmosphere. PMID:23090634

Lasne, Jérôme; Laffon, Carine; Parent, Philippe

2012-12-01

372

Polyunsaturated fatty acids production with a solid-state column reactor.  

PubMed

To investigate the potential production of polyunsaturated fatty acids (PUFAs), a solid-state column reactor of rice bran with Mortierella alpina was used. The optimal conditions for PUFAs production were rice bran supplementation with 3.75% (ww(-1)) nitrogen source at initial moisture content 57%, initial pH 6-7, aeration, and incubation at 20 degrees C for 5 days and then at 12 degrees C for 7 days. Each gram of substrate carbon yielded 127 mg of total PUFAs, 12 mg of eicosapentaenoic acid (EPA), 6 mg of arachidonic acid (AA), 5mg of alpha-linolenic acid (ALA), and 117 mg of linoleic acid (LA) after 12 days incubation. Aeration enhanced the productions of AA, EPA, and total PUFAs. Supplementation of the nitrogen source on the fourth day and then a shift to lower temperature on the fifth day increased EPA production. PMID:18230414

Jang, Hung-Der; Yang, Shang-Shyng

2008-09-01

373

Mixing Acid Salts and Layered Double Hydroxides in Nanoscale under Solid Condition  

PubMed Central

The immobilization of potassium sorbate, potassium aspartate and sorbic acid in layered double hydroxide under solid condition was examined. By simply mixing two solids, immobilization of sorbate and aspartate in the interlayer space of nitrate-type layered double hydroxide, so called intercalation reaction, was achieved, and the uptakes, that is, the amount of immobilized salts and the interlayer distances of intercalation compounds were almost the same as those obtained in aqueous solution. However, no intercalation was achieved for sorbic acid. Although intercalation of sorbate and aspartate into chloride-type layered double hydroxide was possible, the uptakes for these intercalation compounds were lower than those obtained using nitrate-type layered double hydroxide. The intercalation under solid condition could be achieved to the same extent as for ion-exchange reaction in aqueous solution, and the reactivity was similar to that observed in aqueous solution. This method will enable the encapsulation of acidic drug in layered double hydroxide as nano level simply by mixing both solids. PMID:25080007

Nakayama, Hirokazu; Hayashi, Aki

2014-01-01

374

Mixing Acid Salts and Layered Double Hydroxides in Nanoscale under Solid Condition.  

PubMed

The immobilization of potassium sorbate, potassium aspartate and sorbic acid in layered double hydroxide under solid condition was examined. By simply mixing two solids, immobilization of sorbate and aspartate in the interlayer space of nitrate-type layered double hydroxide, so called intercalation reaction, was achieved, and the uptakes, that is, the amount of immobilized salts and the interlayer distances of intercalation compounds were almost the same as those obtained in aqueous solution. However, no intercalation was achieved for sorbic acid. Although intercalation of sorbate and aspartate into chloride-type layered double hydroxide was possible, the uptakes for these intercalation compounds were lower than those obtained using nitrate-type layered double hydroxide. The intercalation under solid condition could be achieved to the same extent as for ion-exchange reaction in aqueous solution, and the reactivity was similar to that observed in aqueous solution. This method will enable the encapsulation of acidic drug in layered double hydroxide as nano level simply by mixing both solids. PMID:25080007

Nakayama, Hirokazu; Hayashi, Aki

2014-01-01

375

Ionic liquid-regulated sulfamic acid: chemoselective catalyst for the transesterification of ?-ketoesters  

Microsoft Academic Search

1-Propyl-3-methylimidazolium chloride ([C3MIm]Cl) ionic liquid and sulfamic acid (NH2SO3H), as a synergetic catalytic medium, were used for the transesterification of acetoacetate with alcohols of different structures. It shows the good ability for the chemoselective transesterificatin of ?-ketoesters and maintains its catalytic activity in the reuse.

Wang Bo; Yang Li Ming; Suo Ji Shuan

2003-01-01

376

H-gallosilicate (MFI) propane aromatization catalyst: Influence of Si/Ga ratio on acidity, activity and deactivation due to coking  

SciTech Connect

Influence of bulk Si/Ga ratio of H-gallosilicate (MFI) on its degalliation (during calcination for removal of template and deammoniation of NH{sub 4} form), acidity/acid strength distribution (measured by stepwise thermal desorption and chemisorption of pyridine at 50-400{degrees}C using GC techniques and also by acid catalyzed model reactions viz. iso-octane cracking and toluene disproportionation) and initial activity/product selectivity and catalyst deactivation in propane aromatization (at 550{degrees}C) has been investigated. Framework Si/Ga ratio was measured by {sup 29}Si MAS NMR. Information on the external acid sites is obtained by isooctane cracking. The influence of poisoning of strong acid sites (by pyridine) on acid catalyzed model reactions and the effect of deactivation on the product distribution in the propane aromatization have also been studied. 21 refs., 19 figs., 3 tabs.

Choudhary, V.R.; Kinage, A.K.; Sivadinarayana, C. [National Chemical Lab., Pune (India)] [and others] [National Chemical Lab., Pune (India); and others

1996-01-01

377

2H-solid state NMR and DSC study of isobutyric acid in mesoporous silica materials.  

PubMed

Solid state deuterium NMR has been used to study the molecular motion of d(6)-isobutyric acid (d(6)-iBA) in the pure (unconfined) state and confined in the cylindrical pores of two periodic mesoporous silica materials (MCM-41, pore size 3.3 nm and SBA-15, pore size 8 nm), and in a controlled pore glass (CPG-10-75, pore size ca. 10 nm). The line shape analysis of the spectra at different temperatures revealed three rotational states of the iBA molecules: liquid (fast anisotropic reorientation of the molecule), solid I (rotation of the methyl group) and solid II (no rotational motion on the time scale of the experiment). Transition temperatures between these states were determined from the temperature dependence of the fraction of molecules in these states. Whereas the solid I-solid II transition temperature is not affected by confinement, a significant lowering of the liquid-solid I transition temperature in the pores relative to the bulk acid was found for the three matrix materials, exhibiting an unusual dependence on pore size and pore morphology. Complementary DSC measurements on the same systems show that the rotational melting (solid I-liquid) of d(6)-iBA in the pores occurs at a temperature 20-45 K below the thermodynamic melting point. This finding indicated that the decoupling of rotational and translational degrees of freedom in phase transitions in confined systems previously found for benzene is not restricted to molecules with non-specific interactions, but represents a more general phenomenon. PMID:17487322

Vyalikh, A; Emmler, Th; Shenderovich, I; Zeng, Y; Findenegg, G H; Buntkowsky, G

2007-06-14

378

Furfural modified asphalt obtained by using a Lewis acid as a catalyst  

SciTech Connect

Asphalt is solid or semi-solid at room temperature, becomes soft and starts flowing upon heating, and becomes hard and brittle at very low temperatures. States have been facing problems such as cracking, rutting, and asphalt adhesion to aggregates in their asphaltic pavements for years. Many polymer additives have been used in asphalt to reduce these problems, but little work has been done using chemically modified products of asphalt to attempt to solve these serious problems of asphalt pavements. The above mentioned problems decrease the life of the pavements, resulting in an increase of maintenance and/or replacement costs. There are two types of cracking which can occur in asphalt pavement; one related to load, and the other related to thermal stress. The load-related cracking is known as fatigue cracking and is defined as fracture under repeated or cyclic stress having a maximum value of less than the tensile strength of the material. The thermal cracking occurs due to pavement shrinkage at low temperature causing the shrinkage stresses to exceed the tensile strength. FHWA researchers have found furfural to be a suitable candidate for functional group modification of asphalt. The modified product shows improved performance as well as improved rheological properties.

Memon, G.M. [FHWA/EBA Engineering Inc., McLean, VA (United States); Chollar, B.H. [FHWA, McLean, VA (United States)

1996-12-31

379

ZnO/carbon nano composite: Effective catalyst for the photo degradation of Acid Blue 113  

NASA Astrophysics Data System (ADS)

Zinc oxide carbon composite (ZnO/C) was synthesized by self - propagating solution combustion method. This method enabled the addition of carbon insitu to the metal oxide. The composite synthesized were characterised by XRD, SEM and BET analysis. This composite was used for the removal of organic pollutants such as the dye Acid blue 113 by UV irradiation performed in a batch reactor. The influence of various experimental parameters such as the initial concentration of the dye, Concentration of the photocatalyst and the pH on the photo catalytic degradation under UV irradiation was studied. It has been observed that the degradation of the dye to be more pronounced in neutral medium. The degradation of acid blue 113 was found to increase with ZnO/C composites loading and decreases with decrease in concentration of the composite.

Sunitha, S.; Rao, A. Nageswara; Karthikeyan, J.; Krithiga, T.

2013-06-01

380

Photocatalytic degradation of 2,4-dichlorophenoxyacetic acid using nanocrystalline cryptomelane composite catalysts  

Microsoft Academic Search

2,4-Dichlorophenoxyacetic acid is a common systemic herbicide used in the control of broadleaf weeds. It is the third-most widely used herbicide in the world. 2,4-D heterogeneous photocatalysis has emerged as a useful process to aid remediation of wastewater contamination. Manganese oxide with 2×2 tunnel structure, cryptomelane show good results in the photodegradation of 2,4-D and excellent performance in the photodegradation

M. Alvarez Lemus; T. López; S. Recillas; D. M. Frías; M. Montes; J. J. Delgado; M. A. Centeno; J. A. Odriozola

2008-01-01

381

Oxidation catalyst  

DOEpatents

The present invention generally relates to catalyst systems and methods for oxidation of carbon monoxide. The invention involves catalyst compositions which may be advantageously altered by, for example, modification of the catalyst surface to enhance catalyst performance. Catalyst systems of the present invention may be capable of performing the oxidation of carbon monoxide at relatively lower temperatures (e.g., 200 K and below) and at relatively higher reaction rates than known catalysts. Additionally, catalyst systems disclosed herein may be substantially lower in cost than current commercial catalysts. Such catalyst systems may be useful in, for example, catalytic converters, fuel cells, sensors, and the like.

Ceyer, Sylvia T. (Cambridge, MA); Lahr, David L. (Cambridge, MA)

2010-11-09

382

Catalyst Alloys Processing  

NASA Astrophysics Data System (ADS)

Catalysts are one of the key materials used for diamond formation at high pressures. Several such catalyst products have been developed and applied in China and around the world. The catalyst alloy most widely used in China is Ni70Mn25Co5 developed at Changsha Research Institute of Mining and Metallurgy. In this article, detailed techniques for manufacturing such a typical catalyst alloy will be reviewed. The characteristics of the alloy will be described. Detailed processing of the alloy will be presented, including remelting and casting, hot rolling, annealing, surface treatment, cold rolling, blanking, finishing, packaging, and waste treatment. An example use of the catalyst alloy will also be given. Industrial experience shows that for the catalyst alloy products, a vacuum induction remelt furnace can be used for remelting, a metal mold can be used for casting, hot and cold rolling can be used for forming, and acid pickling can be used for metal surface cleaning.

Tan, Xincai

2014-10-01

383

Regeneration of a deactivated USY alkylation catalyst using supercritical isobutane  

SciTech Connect

Off-line, in-situ alkylation activity recovery from a completely deactivated solid acid catalyst was examined in a continuous-flow reaction system employing supercritical isobutane. A USY zeolite catalyst was initially deactivated during the liquid phase alkylation of butene with isobutane in a single-pass reactor and then varying amounts of alkylation activity were recovered by passing supercritical isobutane over the catalyst bed at different reactivation conditions. Temperature, pressure and regeneration time were found to play important roles in the supercritical isobutane regeneration process when applied to a completely deactivated USY zeolite alkylation catalyst. Manipulation of the variables that influence solvent strength, diffusivity, surface desorption, hydride transfer rates, and coke aging, strongly influence regeneration effectiveness.

Daniel M. Ginosar; David N. Ghompson; Kyle C. Burch

2005-01-01

384

The development and applications of CAVERN methods for in situ NMR studies of reactions on solid acids  

Microsoft Academic Search

This article reviews many technical details of in situ NMR applied in catalysis and reactions on catalysts. Several generations\\u000a of CAVERN devices, which are at the heart of in situ NMR, are described in great detail. The use of these devices allows cryogenic\\u000a preparation of solids, liquids and moisture- or air-sensitive samples for variable temperature, magic angle spinning NMR studies.

T. Xu; J. F. Haw

1997-01-01

385

Photocatalytic oxidation of salicylic acid and 4-chlorophenol in aqueous solutions mediated by modified AlFe 2O 3 catalyst under sunlight  

Microsoft Academic Search

The visible light photochemical and photocatalytic oxidation of salicylic acid and 4-chlorophenol in a photoelectrocatalytic degradation reactor, at room temperature, under sunlight illumination, coated with anatase TiO2-based Fe2O3 and AlFe2O3 photocatalysts were investigated. The solar radiation can effectively be applied to accelerate the process using suitable catalyst for economically cleaning the major fresh water sources. The profile of the oxidation

S. S. Shinde; C. H. Bhosale; K. Y. Rajpure

2011-01-01

386

Silica supported perchloric acid (HClO 4SiO 2): A highly efficient and reusable catalyst for geminal diacylation of aldehydes under solvent-free conditions  

Microsoft Academic Search

Perchloric acid immobilized on silica gel has been found to be an efficient and expedient catalyst for geminal diacylation of aldehydes. A wide variety of aromatic and aliphatic aldehydes can be easily transformed into the corresponding acylals using 0.5mol% HClO4-SiO2 within 2–10min under solvent-free conditions at room temperature. The notable advantages of this protocol are: the reaction requires less reaction

Abu T. Khan; Lokman H. Choudhury; Subrata Ghosh

2006-01-01

387

Mesoporous silica iron-doped as stable and efficient heterogeneous catalyst for the degradation of C.I. Acid Orange 7 using sono–photo-Fenton process  

Microsoft Academic Search

Iron-containing mesostructured silica (Fe2O3\\/SBA-15) was prepared and used as heterogeneous catalyst in the integrated sono–photo-Fenton process. The effect of hydrogen peroxide concentration, initial pH, Fe2O3\\/SBA-15 loading, ultrasonic power, and initial solution concentration on the decolorization of C.I. Acid Orange 7 (AO7) by the integrated heterogeneous sono–photo-Fenton process was investigated in order to optimize process efficiency. The results showed that the

Xin Zhong; Sebastien Royer; Hui Zhang; Qianqian Huang; Luojing Xiang; Sabine Valange; Joel Barrault

2011-01-01

388

[BPy]HSO4 Acidic Ionic Liquid as a Novel, Efficient, and Environmentally Benign Catalyst for Synthesis of 1,5?Benzodiazepines under Mild Conditions  

Microsoft Academic Search

A novel and simple ionic liquid methodology for the synthesis of 1,5?benzodiazepines is described. 1?Butylpyridinium hydrogen sulphate ([BPy]HSO4), an acidic room?temperature ionic liquid, as a novel and efficient catalyst, was synthesized and used in the preparation of a series of 1,5?benzodiazepine derivatives by the reaction of o?phenylenediamine with chalcones under mild conditions. This method is easy, efficient, environmentally friendly, economical,

Yuying Du; Fuli Tian; Wenzhi Zhao

2006-01-01

389

Arginine as a General Acid Catalyst in Serine Recombinase-mediated DNA Cleavage*  

PubMed Central

Members of the serine family of site-specific DNA recombinases use an unusual constellation of amino acids to catalyze the formation and resolution of a covalent protein-DNA intermediate. A recent high resolution structure of the catalytic domain of Sin, a particularly well characterized family member, provided a detailed view of the catalytic site. To determine how the enzyme might protonate and stabilize the 3?O leaving group in the strand cleavage reaction, we examined how replacing this oxygen with a sulfur affected the cleavage rate by WT and mutant enzymes. To facilitate direct comparison of the cleavage rates, key experiments used suicide substrates that prevented religation after cleavage. The catalytic defect associated with mutation of one of six highly conserved arginine residues, Arg-69 in Sin, was partially rescued by a 3? phosphorothiolate substrate. We conclude that Arg-69 has an important role in stabilizing the 3?O leaving group and is the prime candidate for the general acid that protonates the 3?O, in good agreement with the position it occupies in the high resolution structure of the active site of Sin. PMID:23970547

Keenholtz, Ross A.; Mouw, Kent W.; Boocock, Martin R.; Li, Nan-Sheng; Piccirilli, Joseph A.; Rice, Phoebe A.

2013-01-01

390

Platinum-nickel catalyst: The effect of promoters in cis-oleic acid adsorption  

NASA Astrophysics Data System (ADS)

The study of the cis-oleic acid adsorption, on clean and promoted (K, Mg, Co, B or Pd) PtNi(1 1 1) surface was performed by quatum chemical calculations. The oleic acid adsorption on PtNi(1 1 1) surface shows a weak molecule-surface interaction. No preferential site for Cdbnd C adsorption is computed and only the Cdbnd O adsorption is favored on the clean PtNi(1 1 1) surface. The adsorption properties of the PtNi(1 1 1) are improved by promoters. The stability of the system is increased and the Cdbnd C/surface distances are reduced when promoters are present. Among the considered promoters, Co has the best performance in terms of system stability. The lowest C p orbital substantially interacts with Pt and Co s, p and d orbitals. The change electron density of metal centers, enhance the Cdbnd C adsorption being the Pt-C interaction the more favored. After adsorption, the strength of the Cdbnd C, Ptsbnd Pt and Ptsbnd Co bonds decrease while a molecule-surface bond is formed.

Simonetti, S.; Martirena, M.; Ulacco, S.; Brizuela, G.

2013-01-01

391

Arginine as a general acid catalyst in serine recombinase-mediated DNA cleavage.  

PubMed

Members of the serine family of site-specific DNA recombinases use an unusual constellation of amino acids to catalyze the formation and resolution of a covalent protein-DNA intermediate. A recent high resolution structure of the catalytic domain of Sin, a particularly well characterized family member, provided a detailed view of the catalytic site. To determine how the enzyme might protonate and stabilize the 3'O leaving group in the strand cleavage reaction, we examined how replacing this oxygen with a sulfur affected the cleavage rate by WT and mutant enzymes. To facilitate direct comparison of the cleavage rates, key experiments used suicide substrates that prevented religation after cleavage. The catalytic defect associated with mutation of one of six highly conserved arginine residues, Arg-69 in Sin, was partially rescued by a 3' phosphorothiolate substrate. We conclude that Arg-69 has an important role in stabilizing the 3'O leaving group and is the prime candidate for the general acid that protonates the 3'O, in good agreement with the position it occupies in the high resolution structure of the active site of Sin. PMID:23970547

Keenholtz, Ross A; Mouw, Kent W; Boocock, Martin R; Li, Nan-Sheng; Piccirilli, Joseph A; Rice, Phoebe A

2013-10-01

392

Soluble Solids, Acidity, Canopy Fruit Distribution, and Disease Susceptibility of Selected Grape Cultivars in Quebec  

Microsoft Academic Search

Twenty grapevine genotypes (‘Chancellor’, ‘Delisle’, ‘ES-6–12–28’, ‘ES-4–7–25’, ‘GR-7’, ‘Hibernal’, ‘Sabrevois’, ‘Kay Gray’, ‘Lucie Kuhlmann’, ‘Michurinetz’, ‘Okanagan Riesling’, ‘Prairie Star’, ‘St. Croix’, ‘St. Pepin’, ‘Seyval Noir’, ‘Seyval Blanc’, ‘SV-18–307’, ‘Vandal-Cliche’, ‘Vidal Blanc’, and ‘Siegerrebe’) were evaluated under different winter protection methods in Frelighsburg, Quebec, Canada. The effects of these methods on soluble solids, acidity, fruit canopy distribution, and susceptibility to diseases

Shahrokh Khanizadeh; Djamila Rekika; Laetitia Porgès; Audrey Levasseur; Yvon Groleau; Helen Fisher

2008-01-01

393

Prototype demonstration of dual sorbent injection for acid gas control on municipal solid waste combustion units  

SciTech Connect

This report gathered and evaluated emissions and operations data associated with furnace injection of dry hydrated lime and duct injection of dry sodium bicarbonate at a commercial, 1500 ton per day, waste-to-energy facility. The information compiled during the project sheds light on these sorbents to affect acid gas emissions from municipal solid waste combustors. The information assesses the capability of these systems to meet the 1990 Clean Air Act and 1991 EPA Emission Guidelines.

None

1994-05-01

394

A shrinking core model for slow combustion of solid 5- O -caffeoylquinic acid  

Microsoft Academic Search

The oxidation of 5-O-caffeoylquinic acid (5-CQA) was investigated in the temperature range from 161 to 188 °C. The kinetic experiments were carried\\u000a out in small batch reactors made of glass, where a very thin (1.1 ?m) fixed bed of powder 5-CQA was in contact with air at\\u000a approximately 91.4 kPa. Aqueous 5-CQA solutions were prepared with the solid found in the reactors at

Everton Fernando ZanoeloCristina; Cristina Benincá

395

Oxidative degradation of dinitro butyl phenol (DNBP) utilizing hydrogen peroxide and solar light over a Al2O3-supported Fe(III)-5-sulfosalicylic acid (ssal) catalyst.  

PubMed

A novel and efficient photo-Fenton catalyst of Fe(III)-5-sulfosalicylic acid (ssal) supported on Al(2)O(3) was prepared and characterized by FT-IR and TEM-EDX technique. A detailed investigation of photocatalytic degradation of 2-sec-butyl-4,6-dinitrophenol (DNBP) using this catalyst and H(2)O(2) under solar light irradiation was carried out. The effects of reaction parameters on photodegradation performance were investigated by examining H(2)O(2) dosage, catalyst loading, solution pH, initial DNBP concentration and temperature. The optimal conditions were an initial DNBP concentration of 40 mg L(-1) at pH 2.5 and temperature 30 degrees C with catalyst loading of 1.0 g L(-1) and H(2)O(2) concentration of 5 mmol L(-1) under solar light irradiation for 100 min. Almost complete degradation of DNBP was observed with [Fe(III)-ssal]-Al(2)O(3)/H(2)O(2) process under the optimal conditions. The degradation of DNBP by photo-Fenton-type process can be divided into the initiation phase and the fast phase. The kinetics of Fenton oxidation is complex and the degradation of DNBP in the two phases both can be described by a pseudo-first-order kinetic model. No obvious decline in efficiency of the [Fe(III)-ssal]-Al(2)O(3) catalyst was observed after 5 repeated cycles indicating this catalyst is stable and reusable. A possible reaction mechanism was proposed on the basis of all the information obtained under various experimental conditions. PMID:20034737

Zhang, Qian; Jiang, Wen-Feng; Wang, Hui-Long; Chen, Mao-Du

2010-04-15

396

One-Pot Synthesis of ?-Acetamido Ketones Using Boric Acid at Room Temperature  

PubMed Central

?-acetamido ketones were synthesized in excellent yields through one-pot condensation reaction of aldehydes, acetophenones, acetyl chloride, and acetonitrile in the presence of boric acid as a solid heterogeneous catalyst at room temperature. It is the first successful report of boric acid that has been used as solid acid catalyst for the preparation of ?-acetamido ketones. The remarkable advantages offered by this method are green catalyst, mild reaction conditions, simple procedure, short reaction times, and good-to-excellent yields of products. PMID:22666168

Karimi-Jaberi, Zahed; Mohammadi, Korosh

2012-01-01

397

A metal-free aerobic oxidation of nitrotoluenes catalyzed by N,N',N?-trihydroxyisocyanuric acid (THICA) and a novel approach to the catalyst.  

PubMed

A metal-free catalytic system with N,N',N?-trihydroxyisocyanuric acid (THICA) as the catalyst for the oxidation of nitrotoluenes is introduced, and a novel Pd-free approach for the synthesis of THICA was developed. In a solution of acetic acid, THICA and concentrated nitric acid, nitrotoluenes especially polynitrotoluenes such as 2,4,6-trinitrotoluene (TNT), were converted into the desired carboxylic acids under 0.2 MPa of O(2) at 100°C with yields up to 99%. THICA was synthesized from N-hydroxyphtalimide through a four-step synthesis in a total yield of 46%. A possible mechanism of this catalytic process was proposed where NO(2) and nitric acid first induced a radical of THICA, which then abstracts a hydrogen atom from the methyl on the aromatic ring to form a benzyl radical. This radical then initiates subsequent reactions. The production of the benzyl radical was supported by ESR measurements. PMID:20869170

Wang, Kai; Zhou, Zhiming; Song, Jinhong; Bi, Lixue; Shen, Ning; Wu, Yukai; Chen, Fuxue; Wen, Hongliang

2010-12-15

398

Effects of metal and acidic sites on the reaction by-products of butyl acetate oxidation over palladium-based catalysts.  

PubMed

Catalytic oxidation is widely used in pollution control technology to remove volatile organic compounds. In this study, Pd/ZSM-5 catalysts with different Pd contents and acidic sites were prepared via the impregnation method. All the catalysts were characterized by means of N2 adsorption-desorption, X-ray fluorescence (XRF), H2 temperature programmed reduction (H2-TPR), and NH3 temperature programmed desorption (NH3-TPD). Their catalytic performance was investigated in the oxidation of butyl acetate experiments. The by-products of the reaction were collected in thermal desorption tubes and identified by gas chromatography/mass spectrometry. It was found that the increase of Pd content slightly changed the catalytic activity of butyl acetate oxidation according to the yield of CO2 achieved at 90%, but decreased the cracking by-products, whereas the enhancement of strong acidity over Pd-based catalysts enriched the by-product species. The butyl acetate oxidation process involves a series of reaction steps including protolysis, dehydrogenation, dehydration, cracking, and isomerization. Generally, butyl acetate was cracked to acetic acid and 2-methylpropene and the latter was an intermediate of the other by-products, and the oxidation routes of typical by-products were proposed. Trace amounts of 3-methylpentane, hexane, 2-methylpentane, pentane, and 2-methylbutane originated from isomerization and protolysis reactions. PMID:25079284

Yue, Lin; He, Chi; Hao, Zhengping; Wang, Shunbing; Wang, Hailin

2014-03-01

399

Solvent-free direct preparation of dichloropropanol from glycerol and hydrochloric acid gas in the presence of H 3PMo 12? X W X O 40 catalyst and\\/or water absorbent  

Microsoft Academic Search

Solvent-free direct preparation of dichloropropanol (DCP) from glycerol and hydrochloric acid gas was carried out in the presence of H3PMo12?XWXO40 (X=0, 3, 6, 9, and 12) heteropolyacid (HPA) catalyst and\\/or water absorbent. Acid strength of the HPA catalyst played an important role in determining the catalytic performance in the solvent-free direct preparation of DCP. Water formed during the reaction retarded

Sang Hee Lee; Sun Ho Song; Dong Ryul Park; Ji Chul Jung; Ji Hwan Song; Sung Yul Woo; Won Seob Song; Myong Suk Kwon; In Kyu Song

2008-01-01

400

Tetraphosphine Linker Scaffolds with a Tetraphenyltin Core for Superior Immobilized Catalysts: A Solid-State NMR Study  

E-print Network

already been used in the group to determine the mobility of a deuterated alkyl chain in the coordination sphere of a metal complex.26 Because of this great analytical potential, classical solid-state NMR of the dry materials and HRMAS of slurries... already been used in the group to determine the mobility of a deuterated alkyl chain in the coordination sphere of a metal complex.26 Because of this great analytical potential, classical solid-state NMR of the dry materials and HRMAS of slurries...

Perera, Melanie Ingrid

2012-10-19

401

Solid phase extraction of petroleum carboxylic acids using a functionalized alumina as stationary phase.  

PubMed

Petroleum essentially consists of a mixture of organic compounds, mainly containing carbon and hydrogen, and, in minor quantities, compounds with nitrogen, sulphur, and oxygen. Some of these compounds, such as naphthenic acids, can cause corrosion in pipes and equipment used in processing plants. Considering that the methods of separation or clean up the target compounds in low concentrations and in complex matrix use large amounts of solvents or stationary phases, is necessary to study new methodologies that consume smaller amounts of solvent and stationary phases to identify the acid components present in complex matrix, such as crude oil samples. The proposed study aimed to recover acid compounds using the solid phase extraction method, employing different types of commercial stationary ion exchange phases (SAX and NH(2)) and new phase alumina functionalized with 1,4-bis(n-propyl)diazoniabicyclo[2.2.2]octane chloride silsesquioxane (Dab-Al(2)O(3)), synthesized in this work. Carboxylic acids were used as standard mixture in the solid phase extraction for further calculation of recovery yield. Then, the real sample (petroleum) was fractionated into saturates, aromatics, resins, and asphaltenes, and the resin fraction of petroleum (B1) was eluted through stationary ion exchange phases. The stationary phase synthesized in this work showed an efficiency of ion exchange comparable to that of the commercial stationary phases. PMID:22589166

de Conto, Juliana Faccin; Nascimento, Juciara dos Santos; de Souza, Driele Maiara Borges; da Costa, Luiz Pereira; Egues, Silvia Maria da Silva; Freitas, Lisiane Dos Santos; Benvenutti, Edilson Valmir

2012-04-01

402

Development of ternary alloy cathode catalysts for phosphoric acid fuel cells: Final report  

SciTech Connect

The overall objective of the program was the identification development and incorporation of high activity platinum ternary alloys on corrosion resistant supports, for use in advanced phosphoric acid fuel cells. Two high activity ternary alloys, Pr-Cr-Ce and Pt-Ni-Co, both supported on Vulcan XC-72, were identified during the course of the program. The Pr-Ni-Co system was selected for optimization, including preparation and evaluation on corrosion resistant supports such as 2700/degree/C heat-treated Vulcan XC-72 and 2700/degree/ heat-treated Black Pearls 2000. A series of tests identified optimum metal ratios, heat-treatment temperatures and heat-treatment atmospheres for the Pr-Ni-Co system. During characterization testing, it was discovered that approximately 50% of the nickel and cobalt present in the starting material could be removed, subsequent to alloy formation, without degrading performance. Extremely stable full cell performance was observed for the Pt-Ni-Co system during a 10,000 hour atmosphere pressure life test. Several theories are proposed to explain the enhancement in activity due to alloy formation. Recommendations are made for future research in this area. 62 refs., 23 figs., 27 tabs.

Not Available

1988-11-01

403

Formic Acid Dehydrogenation on Au-Based Catalysts at Near-Ambient Temperatures  

SciTech Connect

Formic acid (HCOOH) is a convenient hydrogen carrier in fuel cells designed for portable use. Recent studies have shown that HCOOH decomposition is catalyzed with Ru-based complexes in the aqueous phase at near-ambient temperatures. HCOOH decomposition reactions are used frequently to probe the effects of alloying and cluster size and of geometric and electronic factors in catalysis. These studies have concluded that Pt is the most active metal for HCOOH decomposition, at least as large crystallites and extended surfaces. The identity and oxidation state of surface metal atoms influence the relative rates of dehydrogenation (HCOOH {yields} H{sub 2} + CO{sub 2}) and dehydration (HCOOH {yields} H{sub 2}O + CO) routes, a selectivity requirement for the synthesis of CO-free H{sub 2} streams for low-temperature fuel cells. Group Ib and Group VIII noble metals catalyze dehydrogenation selectively, while base metals and metal oxides catalyze both routes, either directly or indirectly via subsequent water-gas shift (WGS) reactions.

Ojeda, Manuel; Iglesia, Enrique

2008-11-24

404

Nano-tribological and wear behavior of boric acid solid lubricant.  

SciTech Connect

One uses atomic force microscopy to explore the surface morphology, frictional characteristics (i.e., friction mapping) and surface adhesive forces of boric acid-treated aluminum surfaces. In earlier studies, boric acid was shown to be an effective solid lubricant providing 0.02 to 0.1 friction coefficients to the sliding surfaces of metallic and ceramic materials. In this study, the authors mainly focused on the friction and wear behavior of cleaved single crystals of boric acid. Tests were performed on uncoated and boric acid-coated surfaces of aluminum substrates, as well as the bulk boric acid material. The nano-scale wear of the boric acid crystals manifested itself in the displacement of atomic planes which, in turn, resulted in the formation of the worn area grown by a spiral-growth mechanism. In addition, new crystals in the vicinity of the sliding contact areas were formed. These crystals formed by a spiral dislocation mechanism. The nanoscale friction measurements showed that the friction coefficient of a Si{sub 3}N{sub 4} tip against the boric acid single crystal, was in the range of 0.07 to 0.13, depending on the sliding direction with respect to the crystallographic orientation. The friction coefficients of the boric acid-coated aluminum substrates varied between 0.11 and 0.19. While these values were consistent with earlier findings and further demonstrated the lubricity of boric acid, they were higher than the previous measurements (i.e., 0.011-0.1) obtained on a pin-on-disk machine using steel or ceramic pins. An explanation is provided for this phenomenon.

Mirmiran, S.; Tsukruk, V. V.; Erdemir, A.; Energy Technology; Western Michigan Univ.

1999-01-01

405

Single event kinetic modeling of solid acid alkylation of isobutane with butenes over proton-exchanged Y-Zeolites  

E-print Network

Complex reaction kinetics of the solid acid alkylation of isobutane with butenes over a proton-exchanged Y-zeolite has been modeled at the elementary step level. Starting with a computer algorithm that generated the reaction network based...

Martinis Coll, Jorge Maximiliano

2006-04-12

406

Optimization of biodiesel production process from soybean oil using the sodium potassium tartrate doped zirconia catalyst under Microwave Chemical Reactor.  

PubMed

A solid base catalyst was prepared by the sodium potassium tartrate doped zirconia and microwave assisted transesterification of soybean oil was carried out for the production of biodiesel. It was found that the catalyst of 2.0(n(Na)/n(Zr)) and calcined at 600°C showed the optimum activity. The base strength of the catalysts was tested by the Hammett indicator method, and the results showed that the fatty acid methyl ester (FAME) yield was related to their total basicity. The catalyst was also characterized by FTIR, TGA, XRD and TEM. The experimental results showed that a 2.0:1 volume ratio of methanol to oil, 65°C reaction temperature, 30 min reaction time and 10 wt.% catalyst amount gave the highest the yield of biodiesel. Compared to conventional method, the reaction time of the way of microwave assisted transesterification was shorter. The catalyst had longer lifetime and maintained sustained activity after being used for four cycles. PMID:23587823

Li, Yihuai; Ye, Bin; Shen, Jiaowen; Tian, Zhen; Wang, Lijun; Zhu, Luping; Ma, Teng; Yang, Dongya; Qiu, Fengxian

2013-06-01

407

Hydroquinone-O,O?-diacetic acid as a more labile replacement for succinic acid linkers in solid-phase oligonucleotide synthesis  

Microsoft Academic Search

Hydroquinone-O,O?-diacetic acid (QDA) can be used to link nucleosides to CPG or polystyrene supports instead of succinic acid. Cleavage of oligodeoxy- or oligoribonucleotides, using ammonium hydroxide, requires only two to five minutes. The QDA linker is stable, easily prepared and does not require any other changes to the reagents, methods, or instrumentation used in automated solid-phase oligonucleotide synthesis.

Richard T. Pon; Shuyuan Yu

1997-01-01

408

The effect of metal–acid balance in Pt-loading dealuminated Y zeolite catalysts on the hydrogenation of benzene  

Microsoft Academic Search

The performances of various Pt-loading dealuminated Y zeolite catalysts for the hydrogenation of benzene were investigated in detail. The load of platinum was from 0.05% to 2% and the Si\\/Al ratio of the dealuminated Y zeolite was 17 or 2.6. It is found that the reaction condition and catalyst composition can influence the benzene conversion and the product selectivity substantially.

Jun Wang; Quanzhi Li; Jiandong Yao

1999-01-01

409

Advanced materials for environmental catalysts.  

PubMed

Recent advances in the synthesis and characterization of materials for environmental catalysts are reported in this paper. Highly advanced environmental catalysts for decomposition of volatile organic compounds and nitrogen oxides were artificially designed based on a concept usually employed in the fields of solid-state chemistry and solid-state ionics. Catalytically active materials for complete ethylene oxidation were prepared by a citrate sol-gel method as a key process to obtain CeO(2)-ZrO(2)-Bi(2)O(3) solid solutions. On the other hand, direct NO decomposition catalysts were designed and prepared focusing on the open spaces and oxide anion vacancies in the crystal lattice. Evaluation of the materials as environmental catalysts demonstrated significant advantages over the conventional ones. The design strategy, synthetic method, and structural features of these concerto catalysts are addressed. PMID:19243066

Imanaka, Nobuhito; Masui, Toshiyuki

2009-01-01

410

Solid-Phase Formation Of Isovaline, A Non-Biological, Meteoritic Amino Acid  

NASA Astrophysics Data System (ADS)

Among the Murchison (CM) meteoritic amino acids, isovaline stands out as being non-biological (nonprotein) and having a high abundance. Approximately equal amounts of D- and L-isovaline have been reported in CM meteorites, but the molecule's structure appears to prohibit racemization in aqueous solutions. While it is possible that isovaline could be made by the oft-studied Strecker reaction, laboratory experiments have seldom been able to produce this molecule from realistic molecular precursors. Recently we have investigated the low-temperature solid-phase chemistry of isovaline with an eye toward the molecule's formation, its stability, and the interconversion of its D- and L-enantiomers. Ion-irradiated isovaline-containing ices were examined by IR spectroscopy and highly-sensitive LC/ToF-MS methods to assess both amino acid destruction and racemization. Samples were studied both in the presence and absence of water-ice, and the destruction of isovaline was measured as a function of radiation dose. In addition, we have continued our earlier work on solid-phase amino acid formation, extending it to cover isovaline. In this presentation we will report the results of these newer investigations. This work was supported by a grant to the Goddard Center for Astrobiology through the NASA Astrobiology Institute. AL was supported by an award from the Summer Undergraduate Internship in Astrobiology program.

Hudson, Reggie L.; Lewis, A. S.; Moore, M. H.; Dworkin, J. P.; Glavin, D. P.

2007-10-01

411

Experimental and theoretical analysis of Friedel–Crafts acylation of thioanisole to 4-(methylthio)acetophenone using solid acids  

Microsoft Academic Search

4-(Methylthio)acetophenone is an important drug intermediate used for the synthesis of Vioxx (Rofecoxib), an NSAID, which has selective COX-2 inhibition. It is typically produced on industrial scale by Friedel–Crafts acylation using homogeneous corrosive and polluting acid catalysts such as aluminium chloride in more than stoichiometric amounts with acetyl chloride as the acylating agent. This process creates pollution problems related to

Ganapati D. Yadav; Ramesh D. Bhagat

2005-01-01

412

Coke-free direct formic acid solid oxide fuel cells operating at intermediate temperatures  

NASA Astrophysics Data System (ADS)

Formic acid is investigated as a fuel for Solid Oxide Fuel Cells (SOFCs) for the first time. Thermodynamic calculations demonstrate that carbon deposition is avoidable above 600 °C. The carbon deposition properties are also investigated experimentally by first treating a nickel plus yttria-stabilized zirconia (Ni-YSZ) anode material in particle form under a formic acid-containing atmosphere for a limited time at 500-800 °C and then analyzing the particles by O2-TPO. This analysis confirms that carbon deposition on Ni-YSZ is weak above 600 °C. We further treat half-cells composed of YSZ electrolyte and Ni-YSZ anode under formic acid-containing atmosphere at 600, 700 and 800 °C; the anodes maintain their original geometric shape and microstructure and show no obvious weight gain. It suggests that formic acid can be directly fed into SOFCs constructed with conventional nickel-based cermet anodes. I-V tests show that the cell delivers a promising peak power density of 571 mW cm-2 at 800 °C. In addition, the cells also show good performance stability. The results indicate that formic acid is highly promising as a direct fuel for SOFCs without the need for cell material modifications.

Chen, Yubo; Su, Chao; Zheng, Tao; Shao, Zongping

2012-12-01

413

Kinetic Modeling of Hydrocarbon Processing and the Effect of Catalyst Deactivation by Coke Formation  

Microsoft Academic Search

Previously derived fundamental rate equations for coke formation and catalyst deactivation are applied to the modeling of a number of commercial processes: steam reforming of natural gas, styrene production from ethylbenzene, catalytic cracking of heavy oil fractions, methanol?to?olefins on SAPO 34, and solid acid alkylation on a Y zeolite. The modeling accounts in great detail for the chemistry of the

G. F. Froment

2008-01-01

414

Hydrochloric acid aerosol and gaseous hydrogen chloride partitioning in a cloud contaminated by solid rocket exhaust  

NASA Technical Reports Server (NTRS)

Partitioning of hydrogen chloride between hydrochloric acid aerosol and gaseous HCl in the lower atmosphere was experimentally investigated in a solid rocket exhaust cloud diluted with humid ambient air. Airborne measurements were obtained of gaseous HCl, total HCl, relative humidity and temperature to evaluate the conditions under which aerosol formation occurs in the troposphere in the presence of hygroscopic HCl vapor. Equilibrium predictions of HCl aerosol formation accurately predict the measured HCl partitioning over a range of total HCl concentrations from 0.6 to 16 ppm.

Sebacher, D. I.; Bendura, R. J.; Wornom, D. E.

1980-01-01

415

Determination of the mean solid-liquid interface energy of pivalic acid  

NASA Technical Reports Server (NTRS)

A high-confidence solid-liquid interfacial energy is determined for an anisotropic material. A coaxial composite having a cylindrical specimen chamber geometry provides a thermal gradient with an axial heating wire. The surface energy is derived from measurements of grain boundary groove shapes. Applying this method to pivalic acid, a surface energy of 2.84 erg/sq cm was determined with a total systematic and random error less than 10 percent. The value of interfacial energy corresponds to 24 percent of the latent heat of fusion per molecule.

Singh, N. B.; Gliksman, M. E.

1989-01-01

416

Light-induced, site-selective isomerization of glyoxylic acid in solid xenon  

NASA Astrophysics Data System (ADS)

The isomerization of glyoxylic acid (GA) and its water complex was studied in a low temperature xenon matrix. The aim of these studies was to understand how xenon environment affects the cis-trans GA interconversion upon near infrared irradiation. In solid xenon, the GA conformers are embedded in two different matrix sites. These show up as different vibrational bands of GA that exhibit different kinetic rates of isomerization. Upon complexation with water, the isomerization process slows down. Xenon matrix appears not to affect energy relaxation process via intramolecular or intermolecular hydrogen bond as compared with previous experiments in an argon.

Olbert-Majkut, Adriana; Wierzejewska, Maria; Lundell, Jan

2014-11-01

417

Solid-state NMR studies of theophylline co-crystals with dicarboxylic acids.  

PubMed

In this work, three polycrystalline materials containing co-crystals of theophylline with malonic, maleic, and glutaric acids were studied using (13)C, (15)N and (1)H solid-state NMR and FT-IR spectroscopy. The NMR assignments were supported by gauge including projector augmented waves (GIPAW) calculations of chemical shielding, performed using X-ray determined geometry. The experimental (13)C cross polarization/magic angle spinning (CP/MAS) NMR results and the calculated isotropic chemical shifts were in excellent agreement. A rapid and convenient method for theophylline co-crystals crystal structure analysis has been proposed for co-crystals, which are potentially new APIs. PMID:25194346

Pindelska, Edyta; Sokal, Agnieszka; Szeleszczuk, Lukasz; Pisklak, Dariusz Maciej; Kolodziejski, Waclaw

2014-11-01

418

Solid-state complexes of poly(alpha-amino acid)s and transition metal chlorides  

NASA Astrophysics Data System (ADS)

Poly(4-vinyl pyridine) (P4VP) and dichlorotricarbonyl ruthenium(II) dimer are shown via fourier transform infrared (FTIR) analysis and group theory to form coordination crosslinks. The crosslinks occur by coordination of two pyridine groups to each Rusp{2+} metal center. As the percentage of dimer is increased, FTIR shows evidence of metal pendant groups in addition to the coordination crosslinks. Quantitative measurements from FTIR spectra are used to correlate the number of crosslinks with the amount of dimer present in the mixture. Poly(L-histidine) (PHIS) and poly(L-lysine) (PLYS) are shown to have glass transition temperatures when heated in the solid state. These transition temperatures at 169sp°C for PHIS and 178sp°C have never been reported in the literature. When combined with several first-row transition metal ions (Cosp{2+},\\ Nisp{2+},\\ Cusp{2+},\\ Znsp{2+}) PHIS forms coordination crosslinks. Differential scanning calorimetry (DSC) shows an increase in glass transition temperature for metal/PHIS complexes, with the greatest enhancement (6.9sp°C/mol% metal salt) from nickel chloride. FTIR shows evidence of coordination to both the histidine side chains and to the amide group in the backbone of PHIS. When combined with two second-row metal ions (Rusp{2+},\\ Pdsp{2+}) coordination crosslinks also form, with only histidine side chains involved in the crosslinking. Glass transition temperature is enhanced by 11.5sp°C/mol% metal salt with dichlorobisacetonitrile palladium(II). PLYS does not form coordination crosslinks in the presence of the same first-row metal ions. However, thermal and spectral data suggest a metal salts form pendant groups on the polymer chain via the carbonyl oxygen in the backbone. This metal-polymer coordination causes disruption of hydrogen bonding resulting in a decrease in the glass transition temperature with the addition of metal salts. Statistical models illustrate that ligand field stabilization is an important parameter for the prediction of a change in Tg when metal ions are added to the polymer. Statistical models also confirm that the mechanism, which changes Tg and the spectral data in PLYS/metal blends, is different than the mechanism suggested for PHIS and P4VP complexes.

McCurdie, Mary Pat

419

Parallel transport of an organic acid by solid-phase and macropore diffusion in a weakly basic ion exchanger  

SciTech Connect

The parallel transport of an organic acid by solid-phase and macropore diffusion within a porous ion exchanger was studied by measuring equilibrium isotherms and uptake curves for adsorption of acetic acid and lactic acid on a weakly basic ion exchanger, DIAION WA30. Experimental adsorption isotherms were correlated by the Langmuir equation. The Langmuir equilibrium constant of acetic acid was close to that of lactic acid, and the saturation capacity of acetic acid was about 84% that of lactic acid. Intraparticle effective diffusivity D{sub eff} was determined using the homogeneous Fickian diffusion model. The value of D{sub eff} for acetic acid was about 1.5 times lactic acid. Because D{sub eff} increased with linearly increasing bulk phase concentration C{sub 0}, D{sub eff} was separated to the solid-phase diffusivity D{sub s} and the macropore diffusivity D{sub P} by applying the parallel diffusion model. The model agreed well with the experimental curves. The values of D{sub S} and D{sub P} for acetic acid were about 2 and 1.5 times those of lactic acid, respectively. The acetic acid and the lactic acid may be separated by the difference of the diffusion rates.

Yoshida, Hiroyuki; Takatsuji; Wataru

2000-04-01

420

Friedel–Crafts acylation of anisole with propionic anhydride over mesoporous superacid catalyst UDCaT-5  

Microsoft Academic Search

The synthesis of 4-methoxypropiophenone, an intermediate for the production of fine chemicals and pharmaceuticals, was carried out via Friedel–Crafts acylation of anisole with propionic anhydride by using various solid acid catalysts. The reactions were carried out under solvent-free conditions. A novel mesoporous superacid catalyst UDCaT-5 developed in our laboratory was the most active, selective and robust. The conversion of propionic

Ganapati D. Yadav; Ginish George

2006-01-01

421

Preparation of Carboxymethylchitosan Nanoparticles with Acid-Sensitive Bond Based on Solid Dispersion of 10-Hydroxycamptothecin  

PubMed Central

Solid dispersions were prepared by a conventional solvent evaporation method from the water-insoluble model drug 10-hydroxycamptothecin (HCPT) and monomethoxypoly(ethylene glycol) 2000 (mPEG 2000). And then one type of novel biodegradable nanoparticles, the solid dispersion (HCPT/mPEG-CHO) grafted with carboxymethylchitosan (HCPT/mPEG-g-CMCTS) was synthesized. The increase in HCPT solubility of solid dispersion was up to 21-fold compared with the original drug. With the increasing of the amount of mPEG-CHO, solubility of HCPT was from 7.71??g/mL to 25.82??g/mL. Colloid systems based on solid dispersion were stable in aqueous medium at 5°C. After 5 months storage at 25°C, the solid dispersions do not change at all. HCPT/mPEG-g-CMCTS was synthesized by grafting reaction of carboxymethylchitosan with mPEG-CHO to form Schiff base which is sensitive to acid environment. The release rate of HCPT from this conjugate in pH 5.4 was much higher than that in the environment of pH 7.4 and p H 4.5. The cumulative release percentages are 45%, 25%, and 15%, respectively. The cumulative release percentage of HCPT in conjugate was only 15% within 85?h while the original drug was up to 70% in pH 7.4, showing a significant slow-release property. This drug model can be attractive candidates as delivery biosystems in tumor therapy. PMID:22389854

Yao, Risheng; Liu, Lu; Deng, Shengsong; Ren, Weitao

2011-01-01

422

Silver ion chromatography using solid-phase ex- traction columns packed with a bonded-sulfonic acid phase  

Microsoft Academic Search

Commercial solid-phase extraction columns packed with a stationary phase with bonded benzenesulfonic acid groups are readily converted to the silver ion form and can then be used for silver ion chromatography of lipids. To illustrate the utility of such procedures, methyl ester derivatives of fatty acids with zero to six double bonds were separated from each other by a simple

William W. Christie

423

High piezoelectric performance of poly(lactic acid) film manufactured by solid-state extrusion  

NASA Astrophysics Data System (ADS)

Recently, the application of uniaxially stretched poly(l-lactic acid) (PLLA) films to speakers, actuators, and pressure sensors has been attempted, taking advantage of their piezoelectric performance. However, the shear piezoelectric constant d14 of uniaxially stretched PLLA film is conventionally 6-10 pC N-1. To realize a high sensitivity of pressure sensors, compact speakers, and actuators, and a low driving voltage, further improvement of the piezoelectric performance is desired. In this study, we carried out solid-state extrusion (SSE) to stretch and orient poly(d-lactic acid) (PDLA) and verified its effects on piezoelectric performance. By SSE, we were able to improve the mechanical strength and elastic modulus of PDLA samples. Furthermore, the d14 of the samples was significantly increased to approximately 20 pC N-1.

Yoshida, Mitsunobu; Onogi, Takayuki; Onishi, Katsuki; Inagaki, Takuma; Tajitsu, Yoshiro

2014-09-01

424

Electrochemical performance and durability of carbon supported pt catalyst in contact with aqueous and polymeric proton conductors.  

PubMed

Significant differences in catalyst performance and durability are often observed between the use of a liquid electrolyte (e.g., sulfuric acid), and a solid polymer electrolyte (e.g., Nafion). To understand this phenomenon, we studied the electrochemical behavior of a commercially available carbon supported platinum catalyst in four different electrode structures: catalyst powder (CP), catalyst ionomer electrode (CIE), half membrane electrode assembly (HMEA), and full membrane electrode assembly (FMEA) in both ex situ and in situ experiments under a simulated start/stop cycle. We found that the catalyst performance and stability are very much influenced by the presence of the Nafion ionomers. The proton conducting phase provided by the ionomer and the self-assembled electrode structure render the catalysts a higher utilization and better stability. This is probably due to an enhanced dispersion, an improved proton-catalyst interface, the restriction of catalyst particle aggregation, and the improved stability of the ionomer phase especially after the lamination. Therefore, an innovative electrode HMEA design for ex-situ catalyst characterization is proposed. The electrode structure is identical to the one used in a real fuel cell, where the protons transport takes place solely through solid state proton conducting phase. PMID:25216270

Andersen, Shuang Ma; Skou, Eivind

2014-10-01

425

Pretreatment-Catalyst effects and the combined severity parameter  

Microsoft Academic Search

Fractionation of lignocellulosic materials into high-yield cellulosic solid components can be accomplished with acid-catalyzed\\u000a aqueous and mixed aqueous and nonaqueous media, with the latter leading to high lignin and xyland removal. Concepts combining\\u000a only time and temperature pulping profile with catalyst concentration are presented to correlate these two types of fractionation\\u000a methods with pulping variables. Severity concepts combining time and

Helena L. Chum; David K. Johnson; Stuart K. Black; Ralph P. Overend

1990-01-01

426

Optimization of Citric Acid Production from a New Strain and Mutant of Aspergillus niger Using Solid State Fermentation  

Microsoft Academic Search

A new strain of Aspergillus niger isolated from soil and its mutant were used for citric acid production from carob under solid-state fermentation conditions. The parental strain produced 30 g\\/kg citric acid, while the mutant G4, selected after four rounds of gamma ray irradiation, produced 60 g\\/kg. Maximum citric acid production was obtained after 7 days of incubation, as the

Faiez Alani; Murray Moo-Young; William Anderson; Zakaria Bataine

2007-01-01

427

Biosourced polymetallic catalysts: an efficient means to synthesize underexploited platform molecules from carbohydrates.  

PubMed

Polymetallic hyperaccumulating plants growing on wastes from former mining activity were used as the starting material in the preparation of novel plant-based Lewis acid catalysts. The preparation of biosourced Lewis acid catalysts is a new way to make use of mining wastes. These catalysts were characterized by X-ray fluorescence, X-ray diffraction, inductively coupled plasma mass spectrometry, and direct infusion electrospray ionization mass spectrometry. These analyses revealed a complex composition of metal species, present mainly as polymetallic chlorides. The catalysts proved to be efficient and recyclable in a solid-state version of the Garcia Gonzalez reaction, which has been underexploited until now in efforts to use carbohydrates from biomass. This methodology was extended to various carbohydrates to obtain the corresponding polyhydroxyalkyl furans in 38-98% yield. These plant-based catalysts may be a better alternative to classical Lewis acid catalysts that were previously used for the Garcia Gonzalez reaction, such as ZnCl2 , FeCl3 , and CeCl3 , which are often unrecyclable, require aqueous treatments, or rely on metals, the current known reserves of which will be consumed in the coming decades. Moreover, the plant-based catalysts allowed novel control of the Garcia Gonzalez reaction, as two different products were obtained depending on the reaction conditions. PMID:25044809

Escande, Vincent; Olszewski, Tomasz K; Petit, Eddy; Grison, Claude

2014-07-01

428

An Investigation of Solid-State Amidization and Imidization Reactions in Vapor Deposited Poly (amic acid)  

SciTech Connect

The condensation polymerization reaction of 4,4'-oxydianiline (ODA) with pyromellitic dianhydride (PMDA) to form poly(amic acid) and the subsequent imidization reaction to form polyimide were investigated for films prepared using vapor deposition polymerization techniques. Fourier-transform infrared spectroscopy (FT-IR), thermal analysis, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) of films at different temperatures indicate that additional solid-state polymerization occurs prior to imidization reactions. Experiments reveal that, upon vapor deposition, poly(amic acid) oligomers form that have a number-average molecular weight of about 1500 Daltons. Between 100 - 130 C these chains undergo additional condensation reaction to form slightly higher molecular weight oligomers. Calorimetry measurements show that this reaction is exothermic ({Delta}H {approx} -30 J/g) with an activation energy of about 120 kJ/mol. Experimental reaction enthalpies are compared to results from ab initio molecular modeling calculations to estimate the number of amide groups formed. At higher temperatures (150 - 300 C) imidization of amide linkages occurs as an endothermic reaction ({Delta}H {approx} +120 J/g) with an activation energy of about 130 kJ/mol. Solid-state kinetics were found to depend on reaction conversion as well as the processing conditions used to deposit films.

Anthamatten, M; Letts, S A; Day, K; Cook, R C; Gies, A P; Hamilton, T P; Nonidez, W K

2004-06-28

429

Enhancement of carvedilol solubility by solid dispersion technique using cyclodextrins, water soluble polymers and hydroxyl acid.  

PubMed

Aim of the present work is to enhance aqueous solubility of carvedilol (CV) by solid dispersion technique using wide variety of carriers such as: ?-cyclodextrin (?CD), hydroxypropyl-?-cyclodextrin (HP?CD), tartaric acid (TA), polyvinyl pyrrolidone K-30 (PVP K-30) and poloxamer-407 (PLX-407). Various products of 'CV-solid dispersion' had been studied extensively in various pH conditions to check enhancement of solubility and dissolution characteristics of carvedilol. Any physical change upon interaction between CV and carriers was confirmed by instrumental analysis: XRD, DSC, FTIR and SEM. Negative change of Gibb's free energy and complexation constants (Kc, 75-240M(-1), for cyclodextrins and 1111-20,365M(-1), for PVP K-30 and PLX-407) were the evidence of stable nature of the binding between CV and carriers. 'Solubility enhancement factor' of ionized-CV was found high enough (340 times) with HP?CD in presence of TA. TA increases the binding efficiency of cyclodextrin and changing the pH of microenvironment in dissolution medium. In addition, ionization process was used to increase the apparent intrinsic solubility of drug. In vitro, dissolution time of CV was remarkably reduced in the solid dispersion system compared to that of pure drug. This may be attributed to increased wettability, dispersing ability and transformation of crystalline state of drug to amorphous one. PMID:24705456

Yuvaraja, K; Khanam, Jasmina

2014-08-01

430

Convenient synthesis of unsymmetrical organochalcogenides using organoboronic acids with dichalcogenides via cleavage of the S-S, Se-Se, or Te-Te bond by a copper catalyst.  

PubMed

This article describes the methodology for a copper-catalyzed preparation of numerous monochalcogenides from dichalcogenides with organoboronic acids. Unsymmetrical diorgano-monosulfides, selenides, and tellurides can be synthesized by the coupling of dichalcogenides with aryl- or alkylboronic acids using a copper catalyst in air. The present reaction can take advantage of both organochalcogenide groups on dichalcogenide. PMID:17288374

Taniguchi, Nobukazu

2007-02-16

431

Sulfamic acid as an efficient and recyclable catalyst for the ring opening of epoxides with amines and anilines: An easy synthesis of ?-amino alcohols under solvent-free conditions  

Microsoft Academic Search

Application of sulfamic acid as an efficient and green catalyst for the ring opening of epoxides by aliphatic and aromatic amines under solvent-free conditions is described. In this process the use of basic neutralization agent was not required due to the intrinsic zwitterionic property of sulfamic acid. The salient features of this methodology are cheaper process, easy availability of the

Ahmed Kamal; B. Rajendra Prasad; A. Malla Reddy; M. Naseer A. Khan

2007-01-01

432

pKa Modulation of the Acid/Base Catalyst within GH32 and GH68: A Role in Substrate/Inhibitor Specificity?  

PubMed Central

Glycoside hydrolases of families 32 (GH32) and 68 (GH68) belong to clan GH-J, containing hydrolytic enzymes (sucrose/fructans as donor substrates) and fructosyltransferases (sucrose/fructans as donor and acceptor substrates). In GH32 members, some of the sugar substrates can also function as inhibitors, this regulatory aspect further adding to the complexity in enzyme functionalities within this family. Although 3D structural information becomes increasingly available within this clan and huge progress has been made on structure-function relationships, it is not clear why some sugars bind as inhibitors without being catalyzed. Conserved aspartate and glutamate residues are well known to act as nucleophile and acid/bases within this clan. Based on the available 3D structures of enzymes and enzyme-ligand complexes as well as docking simulations, we calculated the pKa of the acid-base before and after substrate binding. The obtained results strongly suggest that most GH-J members show an acid-base catalyst that is not sufficiently protonated before ligand entrance, while the acid-base can be fully protonated when a substrate, but not an inhibitor, enters the catalytic pocket. This provides a new mechanistic insight aiming at understanding the complex substrate and inhibitor specificities observed within the GH-J clan. Moreover, besides the effect of substrate entrance on its own, we strongly suggest that a highly conserved arginine residue (in the RDP motif) rather than the previously proposed Tyr motif (not conserved) provides the proton to increase the pKa of the acid-base catalyst. PMID:22662155

Yuan, Shuguang; Le Roy, Katrien; Venken, Tom; Lammens, Willem; Van den Ende, Wim; De Maeyer, Marc

2012-01-01

433

pKa modulation of the acid/base catalyst within GH32 and GH68: a role in substrate/inhibitor specificity?  

PubMed

Glycoside hydrolases of families 32 (GH32) and 68 (GH68) belong to clan GH-J, containing hydrolytic enzymes (sucrose/fructans as donor substrates) and fructosyltransferases (sucrose/fructans as donor and acceptor substrates). In GH32 members, some of the sugar substrates can also function as inhibitors, this regulatory aspect further adding to the complexity in enzyme functionalities within this family. Although 3D structural information becomes increasingly available within this clan and huge progress has been made on structure-function relationships, it is not clear why some sugars bind as inhibitors without being catalyzed. Conserved aspartate and glutamate residues are well known to act as nucleophile and acid/bases within this clan. Based on the available 3D structures of enzymes and enzyme-ligand complexes as well as docking simulations, we calculated the pKa of the acid-base before and after substrate binding. The obtained results strongly suggest that most GH-J members show an acid-base catalyst that is not sufficiently protonated before ligand entrance, while the acid-base can be fully protonated when a substrate, but not an inhibitor, enters the catalytic pocket. This provides a new mechanistic insight aiming at understanding the complex substrate and inhibitor specificities observed within the GH-J clan. Moreover, besides the effect of substrate entrance on its own, we strongly suggest that a highly conserved arginine residue (in the RDP motif) rather than the previously proposed Tyr motif (not conserved) provides the proton to increase the pKa of the acid-base catalyst. PMID:22662155

Yuan, Shuguang; Le Roy, Katrien; Venken, Tom; Lammens, Willem; Van den Ende, Wim; De Maeyer, Marc

2012-01-01

434

Complexability of o -bisguanidinobenzenes with arsenic and phosphoric acids in solution and solid states, and the potential use of their immobilized derivatives as solid base ligands for metal salts and arsenic acid  

Microsoft Academic Search

The role of o-bisguanidinobenzenes (BGBs) as new Brønsted base ligands for arsenic and phosphoric acids was examined. In solution state,\\u000a complexation was evaluated by Job’s plot in 1H NMR experiment, indicating a 1:1 complex formation, whereas in solid state crystalline structures of complexes obtained\\u000a were addressed by X-ray crystallographic analysis and\\/or solid state 13C NMR experiment, in which 1:2 complexes

Tomoya Ito; Koji Suda; Takuya Kumamoto; Waka Nakanishi; Toshiko Watanabe; Tsutomu Ishikawa; Hiroko Seki; Masatoshi Kawahata; Kentaro Yamaguchi; Yasumitsu Ogura; Kazuo T. Suzuki

2010-01-01

435

Catalytic properties of heteropoly acid\\/zeolite hybrid materials: toluene disproportionation and transalkylation with 1,2,4-trimethylbenzene  

Microsoft Academic Search

A series of hybrid heteropoly acid (HPA)\\/zeolite catalysts has been prepared by supporting 12-tungstophosphoric acid (H3PW12O40) on a faujasitic matrix. It has been shown that the structure of a dealuminated zeolite Y is retained upon contact with a very strong solid acid. The catalytic properties of the hybrid catalysts were examined in the two gas-phase reactions: disproportionation of toluene and

B. Sulikowski; R. Rachwalik

2003-01-01

436

Recovery of Alkylation Activity in Deactivated USY Catalyst Using Supercritical Fluids: A Comparison of Light Hydrocarbons  

SciTech Connect

Off-line, in-situ alkylation activity recovery from a completely deactivated solid acid catalyst was examined in a continuous-flow reaction system employing supercritical fluids (SCF). A USY zeolite catalyst was initially deactivated during the liquid phase alkylation of butene with isobutane in a single-pass reactor and then varying amounts of alkylation activity were recovered by passing supercritical fluids over the catalyst bed. A comparison of reactivation fluids on catalyst activity recovery is reported. Fluids examined included helium, propane, n-butane, isobutane, n-pentane, and isopentane. Phases studied included gas, liquid, and supercritical. As much as 82% of the fresh catalyst activity was recovered when employing supercritical isobutane. The ability of the fluid to facilitate a hydride reaction with the adsorbed deactivating high-molecular weight carbocations was indicated as an important property necessary to attain high levels of catalyst activity recovery. Activity recovery utilizing supercritical fluids that enhance reactivation by both reacting with and desorbing fouling compounds appears to be a promising technique to advance solid catalyst alkylation.

Daniel M. Ginosar; David N. Thompson; Kyle C. Burch

2004-05-01

437

Reuse of sewage sludge as a catalyst in ozonation--efficiency for the removal of oxalic acid and the control of bromate formation.  

PubMed

Sewage derived sludge is produced with an annual amount increase of 2% all over the world and it is an urgent issue to be addressed by human being. In the present study, sludge was converted into sludge-based catalyst (SBC) with ZnCl2 as activation agent and characterized by several methods (e.g., scanning electron microscope, X-ray photoelectron spectroscope and Fourier transform infrared spectroscope). Then it was used as a catalyst to enhance the removal of refractory organic matter, oxalic acid, and to control the formation of bromate (BrO3-) in bench semi-continuous ozonation experiments. The effects of various operating parameters on the control of BrO3- formation were investigated. Furthermore, the mechanism for the enhancement of organic matter removal and the control of BrO3- formation was discussed as well. Results indicate that the combination of SBC with ozone shows a strong synergistic effect, resulting in a notable improvement on oxalic acid removal. A crucial surface reaction mechanism for the enhancement of organic matter removal is proposed on the basis of negative effect of higher pH and no inhibition effect of tert-butanol. The control for BrO3- formation was demonstrated and the reason for its control in the process of O3/SBC is the combined effect of SBC reductive properties, ozone exposure decrease and hydrogen peroxide concentration increase. PMID:23021317

Wen, Gang; Pan, Zhi-Hui; Ma, Jun; Liu, Zheng-Qian; Zhao, Lei; Li, Jun-Jing

2012-11-15

438

Deactivation mechanism of potassium on the V?O?/CeO? catalysts for SCR reaction: acidity, reducibility and adsorbed-NOx.  

PubMed

A series of V2O5/CeO2 catalysts with different potassium loadings were prepared to investigate alkali deactivations for selective catalytic reduction of NOx with NH3. An alkali poisoning mechanism could be attributed to surface acidity, reducibility, and NOx adsorption/desorption behaviors. The detailed factors are as follows: (1) decrease of surface acidity suppresses NH3 adsorption by strong bonding of alkali to vanadia (major factor); (2) low reducibility prohibits NH3 activation and NO oxidation by formation bonding of alkali to vanadia and ceria (important factor); (3) active NOx(-) species at low temperature diminish because of coverage of alkali on the surfaces (minor factor); and (4) stable, inactive nitrate species at high temperature increase by generating new basic sites (important factor). PMID:24634979

Peng, Yue; Li, Junhua; Huang, Xu; Li, Xiang; Su, Wenkang; Sun, Xiaoxu; Wang, Dezhi; Hao, Jiming

2014-04-15

439

Isolable gold(I) complexes having one low-coordinating ligand as catalysts for the selective hydration of substituted alkynes at room temperature without acidic promoters.  

PubMed

Hydration of a wide range of alkynes to the corresponding ketones has been afforded in high yields at room temperature by using gold(I)-phosphine complexes as catalyst, with no acidic cocatalysts required. Suitable substrates covering alkyl and aryl terminal alkynes, enynes, internal alkynes, and propargylic alcohols, including enantiopure forms, are cleanly transformed to the corresponding ketones in nearly quantitative yields. Acid-labile groups present in the substrates are preserved. The catalytic activity strongly depends on both the nature of the phosphine coordinated to the gold (I) center and the softness of the counteranion, the complex AuSPhosNTf(2) showing the better activity. A plausible mechanism for the hydration of alkynes through ketal intermediates is proposed on the basis of kinetic studies. The described catalytic system should provide an efficient alternative to mercury-based methodologies and be useful in synthetic programs. PMID:19170603

Leyva, Antonio; Corma, Avelino

2009-03-01

440

Catalysts and method  

DOEpatents

An improved catlayst and method for the oxyhydrochlorination of methane is disclosed. The catalyst includes a pyrogenic porous support on which is layered as active material, cobalt chloride in major proportion, and minor proportions of an alkali metal chloride and of a rare earth chloride. On contact of the catalyst with a gas flow of methane, HC1 and oxygen, more than 60% of the methane is converted and of that converted more than 40% occurs as monochloromethane. Advantageously, the monochloromethane can be used to produce gasoline boiling range hydrocarbons with the recycle of HCl for further reaction. This catalyst is also of value for the production of formic acid as are analogous catalysts with lead, silver or nickel chlorides substituted for the cobalt chloride.

Taylor, Charles E. (Pittsburgh, PA); Noceti, Richard P. (Pittsburgh, PA)

1991-01-01

441

Characterization and dynamic properties for the solid inclusion complexes of ?-cyclodextrin and perfluorooctanoic acid.  

PubMed

The structural characterization and dynamic properties of solid-state inclusion complexes (ICs) formed between ?-cyclodextrin (?-CD; host) and perfluorooctanoic acid (PFOA; guest) were investigated using (13)C NMR spectroscopy. The 1:1 and 2:1 host/guest solid-state complexes were prepared using a modified dissolution method to obtain complexes with high phase purity. These complexes were further characterized using differential scanning calorimetry (DSC), FT-IR spectroscopy, powder X-ray diffraction (PXRD), (19)F directpolarization (DP), and (13)C cross-polarization (CP) with magic-angle spinning (MAS) NMR spectroscopy. The (19)F ? (13)C CP results provided unequivocal support for the formation of well-defined inclusion compounds. The phase purity of the complexes formed between ?-CD and PFOA were assessed using the (19)F DP NMR technique at variable temperature (VT) and MAS at 20 kHz. The complexes were found to be of high phase purity when prepared in accordance with the modified dissolution method. The motional dynamics of the guest in the solid complexes were assessed using T1/T2/T1? relaxation NMR methods at ambient and VT conditions. The relaxation data revealed reliable and variable guest dynamics for the 1:1 versus 2:1 complexes at the VTs investigated. The motional dynamics of the guest molecules involve an ensemble of axial motions of the whole chain and 120° rotational jumps of the methyl (CF3) group at the termini of the perfluorocarbon chain. The axial and rotational dynamics of the guest in the 1:1 and 2:1 complexes differ in distribution and magnitude in accordance with the binding geometry of the guest within the host. PMID:23713518

Karoyo, Abdalla H; Sidhu, Paul; Wilson, Lee D; Hazendonk, Paul

2013-07-11

442

Reducing acid leaching of manganiferous ore: Effect of the iron removal operation on solid waste disposal  

SciTech Connect

The process of reducing acid leaching of manganiferous ore is aimed at the extraction of manganese from low grade manganese ores. This work is focused on the iron removal operation. The following items have been considered in order to investigate the effect of the main operating conditions on solid waste disposal and on the process costs: (i) type and quantity of the base agent used for iron precipitation, (ii) effective need of leaching waste separation prior to the iron removal operation, (iii) presence of a second leaching stage with the roasted ore, which might also act as a preliminary iron removal step, and (iv) effect of tailings washing on the solid waste classification. Different base compounds have been tested, including CaO, CaCO{sub 3}, NaOH, and Na{sub 2}CO{sub 3}. The latter gave the best results concerning both the precipitation process kinetics and the reagent consumption. The filtration of the liquor leach prior to iron removal was not neces