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1

Industrial application of solid acid–base catalysts  

Microsoft Academic Search

A statistical survey of industrial processes using solid acid–base catalysts is presented. The number of processes such as alkylation, isomerization, amination, cracking, etherification, etc., and the catalysts such as zeolites, oxides, complex oxides, phosphates, ion-exchange resins, clays, etc., are 127 and 180, respectively. The classification of the types of catalysts into solid acid, solid base, and solid acid–base bifunctional catalysts

Kozo Tanabe; Wolfgang F. Hölderich

1999-01-01

2

The Effect of Supercritical Fluids on Solid Acid Catalyst Alkylation  

SciTech Connect

The alkylation of isobutane with trans-2-butene was explored over six solid acid catalysts in the liquid, near-critical liquid, and supercritical regions through the addition of an inert cosolvent to the reaction feed mixture. The addition of supercritical cosolvents did not result in sustained catalytic alkylation activity. A modest improvement in product yield was obtained with the addition of methane in the modified-liquid region; however, catalyst longevity and product selectivity were decreased compared to cosolvent-free liquid conditions. This paper describes the catalyst screening and selection process, an exploration of catalyst performance with varying concentrations of methane, and an examination of the effects of seven supercritical fluids on catalyst performance. The catalysts included two zeolites, two sulfated metal oxides, and two Nafion catalysts. Three hydrocarbons, two fluorocarbons, carbon dioxide, and sulfur hexafluoride were explored as inert cosolvents added to the reaction mixture.

Ginosar, Daniel Michael; Thompson, David Neil; Burch, Kyle Coates; Zalewski, D. J.

2002-05-01

3

Starch saccharification by carbon-based solid acid catalyst  

NASA Astrophysics Data System (ADS)

The hydrolysis of cornstarch using a highly active solid acid catalyst, a carbon material bearing SO 3H, COOH and OH groups, was investigated at 353-393 K through an analysis of variance (ANOVA) and an artificial neural network (ANN). ANOVA revealed that reaction temperature and time are significant parameters for the catalytic hydrolysis of starch. The ANN model indicated that the reaction efficiency reaches a maximum at an optimal condition (water, 0.8-1.0 mL; starch, 0.3-0.4 g; catalyst, 0.3 g; reaction temperature, 373 K; reaction time, 3 h). The relationship between the reaction and these parameters is discussed on the basis of the reaction mechanism.

Yamaguchi, Daizo; Hara, Michikazu

2010-06-01

4

Esterification of acidic oils over a versatile amorphous solid catalyst.  

PubMed

An amorphous SiO(2)-ZrO(2) catalyst shows high activity in the esterification of free fatty acids contained in vegetable oils while at the same time promoting the transesterification of triglycerides. The catalyst is hence a good candidate for a low-waste deacidification pretreatment or for a one-pot biodiesel production process starting from oils with a high acid content. PMID:19479893

Zaccheria, Federica; Brini, Simona; Psaro, Rinaldo; Scotti, Nicola; Ravasio, Nicoletta

2009-01-01

5

Functionalized carbon nanofibers as solid-acid catalysts for transesterification.  

PubMed

Carbon nanofibers (CNFs) were functionalized with aryl sulfonic acid groups using in situ diazonium coupling. The use of diazonium coupling yielded an acidic carbon material, in which the introduced acidic groups are readily accessible to the triglyceride substrate. The material is an efficient catalyst for the transesterification of triolein and methanol, outperforming conventional sulfonated carbons in both stability and activity per acid site. Upon comparing CNFs with varying degrees of functionalization, a linear correlation between sulfonic acid sites and catalytic performance was found. PMID:23908100

Stellwagen, Daniel R; van der Klis, Frits; van Es, Daan S; de Jong, Krijn P; Bitter, Johannes H

2013-09-01

6

n-hydrocarbons conversions over metal-modified solid acid catalysts  

NASA Astrophysics Data System (ADS)

The quality of a straight-run fuel oil can be improved if saturated n-hydrocarbons of low octane number are converted to their branched counterparts. Poor reactivity of traditional catalysts in isomerization reactions imposed the need for the development of new catalysts among which noble metal promoted acid catalysts, liquid and/or solid acid catalysts take a prominent place. Sulfated zirconia and metal promoted sulfated zirconia exhibit high activity for the isomerization of light alkanes at low temperatures. The present paper highlights the original results which indicate that the modification of sulfated zirconia by incorporation of metals (platinum and rhenium) significantly affects catalytic performances in n-hydrocarbon conversion reactions. Favourable activity/selectivity of the promoted sulfated zirconia depends on the crystal phase composition, critical crystallites sizes, platinum dispersion, total acidity and type of acidity. Attention is also paid to the recently developed solid acid catalysts used in other conversion reactions of hydrocarbons.

Zarubica, A.; Ran?elovi?, M.; Mom?ilovi?, M.; Radulovi?, N.; Putanov, P.

2013-12-01

7

Catalytic dehydration of methanol to dimethyl ether (DME) over solid-acid catalysts  

Microsoft Academic Search

A series of solid-acid catalysts with different components contents were prepared by coprecipitation (sol–gel) method. These samples comprised ?-alumina and modified ?-Al2O3 with silica. The effects of silica various contents have been investigated on purpose to determine an optimum one. Dehydration of methanol to dimethyl ether (DME) on solid-acid catalysts was studied in a fixed-bed flow reactor at a temperature

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

2005-01-01

8

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

9

Enhanced production of hydroxymethylfurfural from fructose with solid acid catalysts by simple water removal methods  

Microsoft Academic Search

This paper demonstrates two simple ways to increase 5-hydroxymethylfurfural (HMF) yield (selectivity) in fructose dehydration with various solid acid catalysts. One is a water removal from the reaction mixture by a mild evacuation at 0.97×105Pa; it increases HMF yield for various catalysts (heteropoly acid, zeolite, and acidic resin). The removal of water suppresses two undesired reactions: the hydrolysis of HMF

Ken-ichi Shimizu; Rie Uozumi; Atsushi Satsuma

2009-01-01

10

Solid catalysts for multistep reactions: one-pot synthesis of 2,3-dihydro-1,5-benzothiazepines with solid acid and base catalysts.  

PubMed

1,5-Benzothiazepines derivatives were obtained first by starting from 1,3-diphenylpropenone derivatives (chalcones) and 2-aminothiophenol by using aluminosilicate solid catalysts. However, diffusional limitations and the strong adsorption of products on the catalyst are deleterious for catalyst activity and life. Then a structured amorphous mesoporous catalyst with large pores and mild acidity that works at higher temperatures allowed us to obtain high conversions (99 %) and selectivities (98 %) of the desired product. A one-pot synthesis of 1,5-benzothiazepines that starts from benzaldehyde, acetophenone, and 2-aminothiophenol with 95 % yield was performed by combining optimized solid base and acid catalysts in batch mode as well as in a continuous-flow reactor system. Much better conversion and selectivity as well as process intensification has been achieved with the structured mesoporous materials by avoiding intermediate and final neutralization and purification steps required in the synthesis reported previously that uses homogeneous catalysts. PMID:24616280

Climent, Maria J; Corma, Avelino; Iborra, Sara; Martí, Laura

2014-04-01

11

Hydrothermal preparation and characterization of novel corncob-derived solid acid catalysts.  

PubMed

Novel corncob-derived solid acid catalysts were successfully synthesized for the first time by the hydrothermal method. The influences of different preparation conditions were investigated, and the structure-function relationships of the resulting catalysts were also discussed on the basis of the analysis of structure and composition. In comparison to conventional solid acid catalysts, the corncob-derived catalyst synthesized under optimized conditions exhibited higher catalytic activity in esterification reactions, yielding nearly 90% methyl oleate in only 2 h. The catalyst retained satisfactory catalytic activity for esterification, even after 8 reaction cycles. Solid-state magic angle spinning (MAS) (13)C nuclear magnetic resonance (NMR) investigations further indicated that the catalyst was composed of polycyclic aromatic carbon sheets bearing -SO3H, -COOH, and -OH groups in adequate amounts and with proper proportions, contributing to its excellent catalytic activity. This work provides a green method to synthesize solid acid catalysts from biomass wastes and may contribute to a holistic approach for biomass conversion. PMID:24820344

Ma, Huan; Li, Jiabao; Liu, Weiwei; Cheng, Beijiu; Cao, Xiaoyan; Mao, Jingdong; Zhu, Suwen

2014-06-11

12

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

13

Deactivation of solid acid catalysts during isobutane alkylation with C4 olefins  

Microsoft Academic Search

Coke formation on solid acid catalysts during isobutane alkylation with C4 olefins was studied. Y-zeolite, mordenite and L-zeolite were investigated, as well as sulfated zirconia catalysts. Zeolites were used in protonic form or after ion exchange with lanthanum nitrate. Studies were carried out in liquid phase in a fixed-bed reactor. It was found that Y-zeolite exchanged with lanthanum, being the

C. A. Querini; E. Roa

1997-01-01

14

Synthesis of dimethyl ether (DME) from methanol over solid-acid catalysts  

Microsoft Academic Search

The catalytic conversion of methanol to dimethyl ether (DME) has been studied over a series of solid-acid catalysts, such as ?-Al2O3, H-ZSM-5, amorphous silica-alumina, as well as titania modified zirconia. All the catalysts are active and selective for DME formation. The apparent activation energy for DME formation over ?-Al2O3 is ca. 25 kcal\\/mol, a value that increases to ca. 37

Mingting Xu; Jack H. Lunsford; D. Wayne Goodman; Alak Bhattacharyya

1997-01-01

15

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

16

Conversion of spent solid phosphoric Acid catalyst to environmentally friendly fertilizer.  

PubMed

Solid phosphoric acid (SPA) catalysts are widely used in the petroleum industry. Despite a high phosphorus content the spent catalyst is generally not reused. Moreover, due to the limited life spans that are achieved industrially, large quantities of spent catalyst requires disposal, often by landfill. SPA can be readily converted to fertilizer, but the presence of carbonaceous deposits on the catalyst presents a potential environmental hazard. This work demonstrates that these deposits are mostly polyaromatic (amorphous carbon) with smaller amounts of oxygenates and aliphatics. Neither the chemical makeup nor the physical structure of the catalyst or the presence of coke precludes it from use as fertilizer. Subsequently, the spent catalyst was milled, neutralized with lime and ammonium hydroxide, and then calcined to yield a phosphate-rich fertilizer. Toxicity characteristic leaching tests of the spent catalyst fertilizer showed low levels of metals and organics, establishing that no harmful compounds are likely to be absorbed into plant life or groundwater. A plant growth study of the spent catalyst fertilizer indicated that it is approximately as effective as superphosphate fertilizer when used in alkaline soil. The spent catalyst fertilizer is environmentally benign and economically efficient. PMID:20146419

Merwe, Werner van der

2010-03-01

17

Mesoporous nickel-aluminosilicate nanocomposite: a solid acid catalyst for ether synthesis.  

PubMed

Mesoporous nickel aluminosilicate, a solid acid catalyst prepared by sol-gel technique was utilized as a heterogeneous catalyst for the synthesis of symmetrical ethers by dehydro-condensation of alcohols. The prepared catalysts were characterized by Fourier-transform infra red spectroscopy (FT-IR), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), N2 adsorption-desorption analysis, temperature programmed desorption of ammonia (TPD) and X-ray photoelectron spectroscopic techniques. The presence of the catalyst assisted the etherification reaction in 30 minutes. Ethers formed in these reactions were quantified by gas chromatography (GC) and the identities of few of them were confirmed by nuclear magnetic resonance spectral data (NMR). PMID:23763171

Neelakandeswari, N; Karvembu, R; Dharmaraj, N

2013-04-01

18

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

19

Influence of solid–acid catalysts on steam reforming and hydrolysis of dimethyl ether for hydrogen production  

Microsoft Academic Search

Influences of solid–acid catalyst on dimethyl ether steam reforming (DME SR) and DME hydrolysis for hydrogen production were investigated. Series of zeolite (JRC-ZHM20(5), JRC-ZHM90(1) as H-mordenite type and JRC-Z5-90H(1) as ZSM-5 type) and of alumina (ALO8, TA1301, TA3301, DK503, NKHD24, NKHO24 and NK324) were used as acidic catalysts for DME hydrolysis. The composite catalysts of the acidic catalyst and CuFe2O4

Kajornsak Faungnawakij; Yohei Tanaka; Naohiro Shimoda; Tetsuya Fukunaga; Shunichiro Kawashima; Ryuji Kikuchi; Koichi Eguchi

2006-01-01

20

Application of solid-acid catalyst and marine macro-algae Gracilaria verrucosa to production of fermentable sugars.  

PubMed

In this study, the hydrolysis of marine macro-algae Gracilaria verrucosa with a solid-acid catalyst was investigated. To optimize the hydrolysis, four reaction factors, including liquid-to-solid ratio, catalyst loading, reaction temperature, and reaction time, were investigated. In the results, the highest total reducing sugar (TRS) yield, 61g/L (51.9%), was obtained under the following conditions: 1:7.5 solid-to-liquid ratio, 15% (w/v) catalyst loading, 140°C reaction temperature, and 150min reaction time. Under these conditions, 10.7g/L of 5-HMF and 2.5g/L of levulinic acid (LA) were generated. The application of solid-acid catalyst and marine macro-algae resources shows a very high potential for production of fermentable sugars. PMID:25625460

Jeong, Gwi-Taek; Kim, Sung-Koo; Park, Don-Hee

2015-04-01

21

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

22

Solid acid catalysts pretreatment and enzymatic hydrolysis of macroalgae cellulosic residue for the production of bioethanol.  

PubMed

The aim of this study is to investigate the technical feasibility of converting macroalgae cellulosic residue (MCR) into bioethanol. An attempt was made to present a novel, environmental friendly and economical pretreatment process that enhances enzymatic conversion of MCR to sugars using Dowex (TM) Dr-G8 as catalyst. The optimum yield of glucose reached 99.8% under the optimal condition for solid acid pretreatment (10%, w/v biomass loading, 4%, w/v catalyst loading, 30min, 120°C) followed by enzymatic hydrolysis (45FPU/g of cellulase, 52CBU/g of ?-glucosidase, 50°C, pH 4.8, 30h). The yield of sugar obtained was found more superior than conventional pretreatment process using H2SO4 and NaOH. Biomass loading for the subsequent simultaneous saccharification and fermentation (SSF) of the pretreated MCR was then optimized, giving an optimum bioethanol yield of 81.5%. The catalyst was separated and reused for six times, with only a slight drop in glucose yield. PMID:25839825

Tan, Inn Shi; Lee, Keat Teong

2015-06-25

23

A comparative study on liquid phase alkylation of 2-methylnaphthalene with long chain olefins using different solid acid catalysts  

Microsoft Academic Search

A comparative study has been made over a variety of solid acid catalysts, which include isopoly and heteropoly ions supported on various supports such as zirconia, titania, a large variety of zeolites and a couple of mesoporous materials for liquid phase alkylation of 2-methylnaphthalene with 1-octene. All the catalyst systems were characterized by nitrogen sorption analysis, X-ray diffraction and NH3-TPD.

Nishita Lucas; Ankur Bordoloi; Amol P. Amrute; Palraj Kasinathan; Ajayan Vinu; Walter Bohringer; Jack C. Q. Fletcher; S. B. Halligudi

2009-01-01

24

Production of 5-hydroxymethylfurfural from corn stalk catalyzed by corn stalk-derived carbonaceous solid acid catalyst.  

PubMed

A carbonaceous solid acid was prepared by hydrothermal carbonization of corn stalk followed by sulfonation and was characterized by FT-IR, XRD, SEM and elemental analysis techniques. The as-prepared corn stalk-derived carbonaceous solid acid catalyst contained SO3H, COOH, and phenolic OH groups, and was used for the one-step conversion of intact corn stalk to 5-hydroxymethylfurfural (5-HMF) in the ionic liquid 1-butyl-3-methyl imidazolium chloride ([BMIM][Cl]), where a 5-HMF yield of 44.1% was achieved at 150 °C in 30 min reaction time. The catalytic system was applicable to initial corn stalk concentration of up to ca. 10 wt.% for the production of 5-HMF. The synthesized catalyst and the developed process of using corn stalk-derived carbon catalyst for corn stalk conversion provide a green and efficient strategy for crude biomass utilization. PMID:25444888

Yan, Lulu; Liu, Nian; Wang, Yu; Machida, Hiroshi; Qi, Xinhua

2014-12-01

25

Acylation of Aromatic Ethers Using Different Carboxylic Acid Anhydrides as Acylating Agents in the Presence of Nontoxic, Noncorrosive Resin Amberlyst 15 as a Solid Acid Catalyst  

Microsoft Academic Search

Friedel–Crafts acylation of aromatic ethers, anisole, 2-methoxynaphthalene, and dimethoxybenzenes with different acid anhydrides is carried out in the presence of an inexpensive and nonhazardous solid acid, Amberlyst 15. The catalyst is reusable, thus making the process environmentally friendly.

Manoj A. Pande; Shriniwas D. Samant

2011-01-01

26

Heteropoly acid supported on titania as solid acid catalyst in alkylation of p-cresol with tert-butanol  

Microsoft Academic Search

Butylation of p-cresol with tert-butanol was investigated on titania modified with 12-tungstophosphoric acid (TPA\\/TiO2) catalyst under vapor phase conditions. Catalysts with different TPA loadings (10–25wt.%) and calcination temperatures (650–750°C) were prepared by suspending titanium hydroxide in methanol solution of TPA followed by drying and calcination. These catalysts were characterized by surface area, XRD, 31P MAS NMR, XPS, NH3-TPD, and FTIR

Suresh M. Kumbar; G. V. Shanbhag; F. Lefebvre; S. B. Halligudi

2006-01-01

27

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

28

Expeditious Pechmann Condensation by Using Biodegradable Cellulose Sulfuric Acid as a Solid Acid Catalyst  

Microsoft Academic Search

A facile synthesis of coumarins was performed in excellent yields via Pechmann condensation by using different type of phenols and ethylacetoacetates under solvent–free media using both conventional method and microwave irradiation in short reaction times is described. The reaction workup is very simple, and the catalyst can be easily separated from the reaction mixture and reused several times in subsequent

B. Suresh Kuarm; J. Venu Madhav; S. Vijaya Laxmi; B. Rajitha; Y. Thirupathi Reddy; P. Narsimha Reddy; Peter A. Crooks

2010-01-01

29

In situ reactive extraction of cottonseeds with methyl acetate for biodiesel production using magnetic solid acid catalysts.  

PubMed

A magnetic solid acid catalyst S2O8(2)(-)/ZrO2-TiO2-Fe3O4 was prepared by coprecipitation and impregnation methods and its catalytic activity was investigated for the reactive extraction of cottonseeds with methyl acetate to produce biodiesel. The physicochemical properties of the catalyst were characterized in detail. The influences of Zr/Ti molar ratio and calcination temperature on the catalytic performance were investigated. Moreover, optimization of the reactive extraction process was performed using response surface methodology coupled with central composite design. The catalyst with a Zr/Ti molar ratio of 3/1 calcined at 550°C showed the best activity. An optimum biodiesel yield of 98.5% was obtained under the reaction temperature of 50°C, catalyst amount of 21.3wt.%, methyl acetate/seed ratio of 13.8ml/g and 10.8h of reaction time. Reuse of this catalyst indicated that it had steady catalytic activity and high recovery rate which could be a promising catalyst for biodiesel production from oilseeds. PMID:25463798

Wu, Haitang; Liu, Yanping; Zhang, Junhua; Li, Guanglu

2014-12-01

30

Generating hydrogen-rich fuel-cell feeds from dimethyl ether (DME) using physical mixtures of a commercial Cu\\/Zn\\/Al 2O 3 catalyst and several solid–acid catalysts  

Microsoft Academic Search

Homogeneous physical mixtures containing a commercial Cu\\/ZnO\\/Al2O3 catalyst and a solid–acid catalyst were used to examine the acidity effects on dimethyl ether hydrolysis and their subsequent effects on dimethyl ether steam reforming (DME-SR). The acid catalysts used were zeolites Y [Si\\/Al=2.5 and 15: denoted Y(Si\\/Al)], ZSM-5 [Si\\/Al=15, 25, 40, and 140: denoted Z(Si\\/Al)] and other conventional catalyst supports (ZrO2, and

Troy A. Semelsberger; Kevin C. Ott; Rodney L. Borup; Howard L. Greene

2006-01-01

31

Solid acid catalysts for converting alkenes and alkanols to carboxylic acids  

Microsoft Academic Search

Tertiary carboxylic acids are presently manufactured by hydrocarboxylation of branched alkenes in the presence of CO, water and a corrosive homogeneous acid. Acidic ion-exchange resins also catalyse the hydrocarboxylation reaction when operated under specific conditions. Critical factors are the use of a moderately polar, non-basic solvent and the maintenance of a very low alkanol or alkene\\/water concentration in the reactor.

J.-P Lange; L Petrus

2001-01-01

32

Simultaneous characterization of acidic and basic properties of solid catalysts by a new TPD method and their correlation to reaction rates  

Microsoft Academic Search

We propose a new TPD method for simultaneously characterizing the acidic and basic properties of solid catalysts by utilizing the co-adsorption of NH3 and CO2 on catalysts. First CO2 was adsorbed on the catalyst sample; then NH3 was adsorbed on it. Another adsorption sequence of NH3 and CO2, and CO2 and NH3 single adsorptions were also conducted. The TPD measurements

Teruoki Tago; Yoshihito Okubo; Shin R. Mukai; Tsunehiro Tanaka; Takao Masuda

2005-01-01

33

Hydrocracking of polyolefins to liquid fuels over strong solid acid catalysts  

SciTech Connect

Post-consumer plastic makes up about 13 wt% of the 48 million tons of total packaging wastes generated annually. Plastics are non-biodegradable, constitute a increasingly large volume of solid wastes (20 vol. % in 1990), and are not being recycled to a significant extent. Pyrolysis, as an alternative for plastic waste recycling, usually results in unsaturated and unstable oils of low yield and value. Significant amounts of char are formed on pyrolyzing plastic wastes. This paper describes the results of hydrocracking of polyolefins over sulfated zirconia catalysts.

Venkatesh, K.R.; Hu, J.; Tierney, J.W.; Wender, I. [Univ. of Pittsburgh, PA (United States)

1995-12-31

34

Low-quality vegetable oils as feedstock for biodiesel production using K-pumice as solid catalyst. Tolerance of water and free fatty acids contents.  

PubMed

Waste oils are a promising alternative feedstock for biodiesel production due to the decrease of the industrial production costs. However, feedstock with high free fatty acids (FFA) content presents several drawbacks when alkaline-catalyzed transesterification reaction is employed in biodiesel production process. Nowadays, to develop suitable processes capable of treating oils with high free fatty acids content, a two-step process for biodiesel production is being investigated. The major problem that it presents is that two catalysts are needed to carry out the whole process: an acidic catalyst for free fatty acids esterification (first step) and a basic catalyst for pretreated product transesterification (second step). The use of a bifunctional catalyst, which allows both reactions to take place simultaneously, could minimize the production costs and time. In the present study, the behavior of pumice, a natural volcanic material used as a heterogeneous catalyst, was tested using oils with several FFA and water contents as feedstock in the transesterification reaction to produce biodiesel. Pumice as a bifunctional solid catalyst, which can catalyze simultaneously the esterification of FFA and the transesterification of fatty acid glycerides into biodiesel, was shown to be an efficient catalyst for the conversion of low-grade, nonedible oil feedstock into biodiesel product. Using this solid catalyst for the transesterification reaction, high FAME yields were achieved when feedstock oils presented a FFA content until approximately 2% wt/wt and a water content until 2% wt/wt. PMID:22799882

Díaz, L; Borges, M E

2012-08-15

35

Mesoporous Silica with Site-Isolated Amine and Phosphotungstic Acid Groups: A Solid Catalyst with Tunable Antagonistic Functions for One-Pot Tandem Reactions  

SciTech Connect

A bifunctional solid catalyst is prepared by combining acid and base functions on mesoporous silica supports. The co-existence of these functions is shown by a two-step reaction sequence in one pot. Excellent product yields, which cannot be obtained by separated acid and base functions in one pot, show the validity of our concept.

Shiju N. R.; Syed K.; Alberts A.; Brown D. and Rothenberg G.

2011-09-15

36

ADSORPTION/DESORPTION STUDIES ON SOLID ACID ALKYLATION CATALYSTS USING A TAPERED ELEMENT OSCILLATING MICROBALANCE (TEOM)  

E-print Network

2-1. Key Operating Parameters of the Reactors for Each Process 20 Table 2-2. Comparison of Material Balance, Raw Material Costs, and Product Sales Revenues for Sulfuric Acid Alkylation Process and Solid Acid/CO2 Alkylation Process 31 Table 2... particles size is 50-53 ?m): (a) mass change due to gas density change at various 224-TMP partial pressures; (b) total mass change (adsorbent is 20.0 mg silica support Davicat SI 1301) and mass change due to gas density change at various 224-TMP partial...

Gong, Kening

2008-10-23

37

Transesterification of triacetin with methanol on solid acid and base catalysts  

Microsoft Academic Search

Biodiesel is a particularly attractive renewable fuel as it can be used in existing engines, is environmentally friendly, and is readily synthesized from animal fats and vegetable oils. Heterogeneous catalysts offer exciting possibilities for improving the economics of biodiesel synthesis; however, few published investigations have addressed the use of such catalysts to date. The purpose of this research was to

Dora E. López; James G. Goodwin; David A. Bruce; Edgar Lotero

2005-01-01

38

Synthesis of phenoxy ethers of methyl lesquerolate over solid acid catalysts  

Technology Transfer Automated Retrieval System (TEKTRAN)

Lesquerolic acid is the primary fatty acid found in Lesquerella. The seeds are 33% oil of which about 55% is the 20 carbon unsaturated hydroxyl fatty acid, lesquerolic acid. A simple derivatization of this fatty acid could expand its potential as an industrial oil. We have used a heterogeneous Le...

39

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...

40

Direct conversion of cellulose to glucose and valuable intermediates in mild reaction conditions over solid acid catalysts  

Microsoft Academic Search

The direct hydrolysis of cellulose to glucose, HMF and other soluble by-products at 190°C in water solution using zeolites (H-BEA, H-MOR), sulphated zirconia supported over mesoporous silica (SBA-15), Amberlyst®15, heteropolyacids and AlCl3·6H2O as acid catalysts was studied using a high cellulose to catalyst ratio (10), not-pretreated (neither mechanically nor chemically) cellulose and a static (not mixed) autoclave. Under these conditions,

P. Lanzafame; D. M. Temi; S. Perathoner; A. N. Spadaro; G. Centi

41

Synthesis of bio-based methacrylic acid by decarboxylation of itaconic acid and citric acid catalyzed by solid transition-metal catalysts.  

PubMed

Methacrylic acid, an important monomer for the plastics industry, was obtained in high selectivity (up to 84%) by the decarboxylation of itaconic acid using heterogeneous catalysts based on Pd, Pt and Ru. The reaction takes place in water at 200-250?°C without any external added pressure, conditions significantly milder than those described previously for the same conversion with better yield and selectivity. A comprehensive study of the reaction parameters has been performed, and the isolation of methacrylic acid was achieved in 50% yield. The decarboxylation procedure is also applicable to citric acid, a more widely available bio-based feedstock, and leads to the production of methacrylic acid in one pot in 41% selectivity. Aconitic acid, the intermediate compound in the pathway from citric acid to itaconic acid was also used successfully as a substrate. PMID:25045161

Le Nôtre, Jérôme; Witte-van Dijk, Susan C M; van Haveren, Jacco; Scott, Elinor L; Sanders, Johan P M

2014-09-01

42

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

E-print Network

Acid Catalyst Functionalization for the Production of Biodiesel Elliot James Nash University of British Functionalization for the Production of Biodiesel By Elliot James Nash Thesis CHBE 493/494 4 April 2013 The Faculty;ii Abstract The adoption of biodiesel as an alternative fuel is gaining momentum despite its large

43

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

44

Supercritical/Solid Catalyst (SSC)  

SciTech Connect

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

2010-01-01

45

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

46

Acidic Cs +, NH 4 +, and K +Salts of 12-Tungstophosphoric Acid as Solid Catalysts for Isobutane\\/2-butene Alkylation  

Microsoft Academic Search

The caesium, ammonium, and potassium salts of 12-tungstophosphoric acid (HPW) have been prepared with different stoichiometries (1?x?3), and their catalytic behavior measured for the liquid phase alkylation of isobutane with 2-butene at 80°C. The salts with a cation content of 2.5?x?3, and that of Cs+withx=2, showed a much higher surface area than the parent acid, which is partially due to

A. Corma; A. Mart??nez; C. Mart??nez

1996-01-01

47

Characterizing Surface Acidic Sites in Mesoporous-Silica-Supported Tungsten Oxide Catalysts Using Solid State NMR and Quantum Chemistry Calculations  

SciTech Connect

The acidic sites in dispersed tungsten oxide supported on SBA-15 mesoporous silica were investigated using a combination of pyridine titration, both fast-, and slow-MAS {sup 15}N NMR, static {sup 2}H NMR, and quantum chemistry calculations. It is found that the bridged acidic -OH groups in surface adsorbed tungsten dimers (i.e., W-OH-W) are the Broensted acid sites. The unusually strong acidity of these Broensted acid sites is confirmed by quantum chemistry calculations. In contrast, terminal W-OH sites are very stable and only weakly acidic as are terminal Si-OH sites. Furthermore, molecular interactions between pyridine molecules and the dimer Broensted and terminal W-OH sites for dispersed tungsten oxide species is strong. This results in restricted molecular motion for the interacting pyridine molecules even at room temperature, i.e., a reorientation mainly about the molecular 2-fold axis. This restricted reorientation makes it possible to estimate the relative ratio of the Broensted (tungsten dimer) to the weakly acidic terminal W-OH sites in the catalyst using the slow-MAS {sup 1}H-{sup 15}N CP PASS method.

Hu, Jian Z.; Kwak, Ja Hun; Wang, Yong; Hu, Mary Y.; Turcu, Romulus VF; Peden, Charles HF

2011-10-18

48

Bioglycerol-based sulphonic acid functionalized carbon: an efficient and recyclable, solid acid catalyst for the regioselective azidolysis of epoxides in aqueous acetonitrile.  

PubMed

A convinent and efficient method was developed for the synthesis of 1,2-azidoalcohols by ring opening of terminal epoxides with sodium azide employing glycerol-based sulphonic acid functionalized carbon as heterogeneous catalyst in aqueous acetonitrile. The reaction is highly regioselective and affords the corresponding products in excellent yields (78-100%) under mild reaction conditions. The catalyst exhibited efficient reusability without loosing its activity even after 5 cycles of azidolysis of methyl 10,11-epoxy undecanoate under optimized conditions within 2 h. PMID:24088523

Vijay, Manneganti; Prasad, Rachapudi Badari Narayana; Devi, Bethala Lakshmi Anu Prabhavathi

2013-01-01

49

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

50

Acidic Cs{sup +}, NH{sub 4}{sup +}, and K{sup +} salts of 12-tungstophosphoric acid as solid catalysts for isobutane/2-butene alkylation  

SciTech Connect

The cesium, ammonium, and potassium salts of 12-tungstophosphoric acid (HPW) have been prepared with different stoichiometries (1{le}x{le}3) and their catalytic behavior measured for the liquid phase alkylation of isobutane with 2-butene at 80{degrees}C. The salts with a cation content of 2.5 {le}x{le}3, and that of Cs{sup +} with x=2, showed a much higher surface area than the parent acid, which is partially due to the formation of micropores. The micropores presented a fairly homogeneous distribution, with an average diameter in the range of 6-11 {Angstrom}, depending on the type of cation and cation content. The activity of the heteropoly acid and their monovalent type B salts for isobutane alkylation could be correlated with the surface acidity of the solids. Thus, the initial (1 min TOS) olefin conversion went through a maximum for the NH{sub 4}{sup +} and K{sup +} salts with a cation content of x = 2.5, and in the range of 2{le}x{le}2.5 in the case of the Cs{sup +} compounds. (NH{sub 4}){sup 2.5}PW showed a very high initial cracking activity (ca. 72 wt% C{sub 5}-C{sub 7} in C{sub 5+}), suggesting the presence of surface acid sites of a higher acid strength in the ammonium salt, as compared to the caesium and potassium salts with similar composition. In all cases the desired trimethylpentanes (TMPs) were the predominant compounds in the C{sub 8} fraction formed in the initial reaction stages. The deactivation rate also depended on the nature of the cation exchanged in the heteropoly salts. 57 refs., 7 figs., 4 tabs.

Corma, A.; Martinez, A.; Martinez, C. [Universidad Politecnica de Valencia (Spain)] [Universidad Politecnica de Valencia (Spain)

1996-12-01

51

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

52

Synthesis and applications of novel imidazole and benzimidazole based sulfonic acid group functionalized Brönsted acidic ionic liquid catalysts  

Microsoft Academic Search

In this study, a variety of imidazole\\/benzimidazole based sulfonic acid group functionalized Brönsted acidic ionic liquids (BAILs) were synthesized. Catalytic activities of BAILs were assessed using multi-component coupling reactions. Catalytic activities of BAILs were high when compared with those of solid acid catalysts such as H-ZSM-5, H-BETA, and sulfonic acid functionalized SBA-15 catalysts. The Hammett acidity order determined from UV–visible

Rajkumar Kore; Rajendra Srivastava

2011-01-01

53

Formic acid fuel cells and catalysts  

DOEpatents

An exemplary fuel cell of the invention includes a formic acid fuel solution in communication with an anode (12, 134), an oxidizer in communication with a cathode (16, 135) electrically linked to the anode, and an anode catalyst that includes Pd. An exemplary formic acid fuel cell membrane electrode assembly (130) includes a proton-conducting membrane (131) having opposing first (132) and second surfaces (133), a cathode catalyst on the second membrane surface, and an anode catalyst including Pd on the first surface.

Masel, Richard I.; Larsen, Robert; Ha, Su Yun

2010-06-22

54

A New Instrument For Characterizing Solid Oxide Fuel Cell Catalysts  

E-print Network

RESEARCH HIGHLIGHTS A New Instrument For Characterizing Solid Oxide Fuel Cell Catalysts From hampered by inadequate catalyst performance, coupled with a lack of fundamental understanding of how the catalyst can be improved. To overcome these challenges, this project developed a new instrument for high

55

The effect of acid–base pairing on catalysis: An efficient acid–base functionalized catalyst for aldol condensation  

Microsoft Academic Search

Acid–base bifunctionalized heterogeneous catalysts may be capable of exhibiting reactivity not achievable with homogeneous catalysts. We investigated the effect of pKa of the acid component of mesoporous solids containing acid–base bifunctionality on their catalytic ability toward aldol condensation between 4-nitrobenzaldehyde and acetone. We found that higher levels of aldol product conversion were obtained when weaker acid components (phosphoric, carboxylic vs

Ryan K. Zeidan; Mark E. Davis

2007-01-01

56

Preparation of poly( p-styrenesulfonic acid) grafted multi-walled carbon nanotubes and their application as a solid-acid catalyst  

Microsoft Academic Search

Poly(p-styenesulfonate acid)-grafted multi-walled carbon nanotubes (PSSA-g-MWCNTs) were prepared by in situ polymerization of sodium p-styrenesulfonate in the presence of MWCNTs, followed by refluxing with concentrated hydrochloric acid. In this reaction system, sodium p-styrenesulfonate served not only as the reaction monomer but also as an amphiphilic dispersant to disperse pristine MWCNTs in water, which is critical for the grafting PSSA onto

Xiao-Hong Zhang; Qian-Qian Tang; Dong Yang; Wei-Ming Hua; Ying-Hong Yue; Bei-Di Wang; Xiao-Huan Zhang; Jian-Hua Hu

2011-01-01

57

Synthesis of Cumene (Isopropylbenzene) from Diisopropylbenzenes in thepresence of Benzene using Triflic acid as catalyst at room temperature  

Microsoft Academic Search

Cumene (isopropylbenzene) is presently produced from benzene and propylene usingeither solid phosphoric acid or anhydrous aluminium chloride or zeolite as catalyst. Large amounts of m- and p- diisopropylbenzenes (DIPB) were produced as by-products from the above processes. Therefore, in order to study the activity of trifluoromethane-sulphonic acid (triflic acid) as catalyst to produce higher yield of cumene from DIPB isomers

M. C. Al-Kinany; S. H. Al-Khowaiter; F. H. Al-Malki

2001-01-01

58

Role of dehydration catalyst acid properties on one-step DME synthesis over physical mixtures  

Microsoft Academic Search

The direct synthesis of dimethyl ether (DME) was studied in a continuous high-pressure unit composed basically of a Berty reactor and on-line gas chromatograph. A commercial methanol synthesis catalyst and some solid-acid catalysts (alumina, HZSM-5, tungsten–zirconia and sulfated-zirconia) were used as physical mixtures. The dehydration catalysts were characterised by pyridine adsorption followed by IR spectroscopy and tested in the methanol

F. S. Ramos; A. M. Duarte de Farias; L. E. P. Borges; J. L. Monteiro; M. A. Fraga; E. F. Sousa-Aguiar; L. G. Appel

2005-01-01

59

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

60

Molybdenum Dioxide As A Solid Oxide Fuel Cell Anodic Catalyst  

E-print Network

hydrocarbons and have great resistance to poisoning. Solid Oxide Fuel Cell Operation Three stages existMolybdenum 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.

61

Heteropoly acids as catalysts for liquid-phase esterification and transesterification  

Microsoft Academic Search

Esterification of hexanoic acid and transesterification of ethyl propanoate and ethyl hexanoate with excess methanol (1:20 molar ratio) are tested at 60°C and ambient pressure with a range of HPA catalysts in homogeneous and heterogeneous systems in comparison with conventional homogeneous and solid acid catalysts such as H2SO4, Amberlyst-15 and zeolites HY and H-Beta. The intrinsic catalytic activity (turnover frequency,

Ali Alsalme; Elena F. Kozhevnikova; Ivan V. Kozhevnikov

2008-01-01

62

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

63

Method for reactivating solid catalysts used in alkylation 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.; Thompson, David N.; Coates, Kyle; Zalewski, David J.; Fox, Robert V.

2003-06-17

64

Syntheses of biodiesel precursors: sulfonic acid catalysts for condensation of biomass-derived platform molecules.  

PubMed

Synthesis of transportation fuel from lignocellulosic biomass is an attractive solution to the green alternative-energy problem. The production of biodiesel, in particular, involves the process of upgrading biomass-derived small molecules to diesel precursors containing a specific carbon range (C11 -C23). Herein, a carbon-upgrading process utilizing an acid-catalyzed condensation of furanic platform molecules from biomass is described. Various types of sulfonic acid catalysts have been evaluated for this process, including biphasic and solid supported catalysts. A silica-bound alkyl sulfonic acid catalyst has been developed for promoting carbon-carbon bond formation of biomass-derived carbonyl compounds with 2-methylfuran. This hydrophobic solid acid catalyst exhibits activity and selectivity that are comparable to those of a soluble acid catalyst. The catalyst can be readily recovered and recycled, possesses appreciable hydrolytic stability in the presence of water, and retains its acidity over multiple reaction cycles. Application of this catalyst to biomass-derived platform molecules led to the synthesis of a variety of furanic compounds, which are potential biodiesel precursors. PMID:24596031

Balakrishnan, Madhesan; Sacia, Eric R; Bell, Alexis T

2014-04-01

65

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

66

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

67

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 9 mol% 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

68

Catalyst and electrode research for phosphoric acid fuel cells  

NASA Technical Reports Server (NTRS)

An account is given of the development status of phosphoric acid fuel cells' high performance catalyst and electrode materials. Binary alloys have been identified which outperform the baseline platinum catalyst; it has also become apparent that pressurized operation is required to reach the desired efficiencies, calling in turn for the use of graphitized carbon blacks in the role of catalyst supports. Efforts to improve cell performance and reduce catalyst costs have led to the investigation of a class of organometallic cathode catalysts represented by the tetraazaannulenes, and a mixed catalyst which is a mixture of carbons catalyzed with an organometallic and a noble metal.

Antoine, A. C.; King, R. B.

1987-01-01

69

Solid Acids for Green Chemistry  

Microsoft Academic Search

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 speciality 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

James H. Clark

2002-01-01

70

Synthesis and acid catalysis of cellulose-derived carbon-based solid acid  

NASA Astrophysics Data System (ADS)

SO 3H-bearing amorphous carbon, prepared by partial carbonization of cellulose followed by sulfonation in fuming H 2SO 4, was applied as a solid catalyst for the acid-catalyzed hydrolysis of ?-1,4 glucan, including cellobiose and crystalline cellulose. Structural analyses revealed that the resulting carbon material consists of graphene sheets with 1.5 mmol g -1 of SO 3H groups, 0.4 mmol g -1 of COOH, and 5.6 mmol g -1 of phenolic OH groups. The carbon catalyst showed high catalytic activity for the hydrolysis of ?-1,4 glycosidic bonds in both cellobiose and crystalline cellulose. Pure crystalline cellulose was not hydrolyzed by conventional strong solid Brønsted acid catalysts such as niobic acid, Nafion ® NR-50, and Amberlyst-15, whereas the carbon catalyst efficiently hydrolyzes cellulose into water-soluble saccharides. The catalytic performance of the carbon catalyst is due to the large adsorption capacity for hydrophilic reactants and the adsorption ability of ?-1,4 glucan, which is not adsorbed to other solid acids.

Suganuma, Satoshi; Nakajima, Kiyotaka; Kitano, Masaaki; Yamaguchi, Daizo; Kato, Hideki; Hayashi, Shigenobu; Hara, Michikazu

2010-06-01

71

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

72

Surface acidity and degree of carburization of modified silver catalysts  

SciTech Connect

The effect has been studied of some compounds as modifying additives on the surface acidity, degree of carburization, aggregation and silver entrainement of silver-pumice catalysts for methanol oxidation. Catalyst samples have been tested in an industrial reactor. The probable mechanism of modifying action of the additives is discussed.

Pestryakov, A.N.; Belousova, V.N.; Roznina, M.I. [Tomsk Institute of Construction Engineering (Russian Federation)

1993-11-10

73

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 ...

74

Tandem Catalytic Conversion of Glucose to 5Hydroxymethylfurfural with an Immobilized Enzyme and a Solid Acid  

E-print Network

to fructose and a solid acid catalyst for fructose dehydration to HMF. A base (-NH2) functionalized mesoporous of tetrahydrofuran (THF) and H2O (4:1 v/v) with 61% yield of fructose and 30% yield of HMF at temperatures >363 K such as fructose can be dehydrated to HMF with various liquid/solid acids in different solvents;2 however

Zhao, Huimin

75

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

76

Sulfonic acid functionalized poly(ethylene glycol dimethacrylate-1-vinyl-1,2,4-triazole) as a high-performance solid acid catalyst for the esterification of lactic acid with methanol.  

PubMed

Sulfonic acid functionalized poly(ethylene glycol dimethacrylate-1-vinyl-1,2,4-triazole), poly(EGDMA-VTAZ-SO(3)H), is evaluated in the esterification of lactic acid with methanol. From nitrogen physisorption data, high surface area (220 m(2)/g) and type IV isotherm are obtained. Conversion measurements indicate a stronger interaction of poly(EGDMA-VTAZ-20%SO(3)H) with water molecules than that occurring in poly(EGDMA-VTAZ-10%SO(3)H). Hence, the higher catalytic activity of poly(EGDMA-VTAZ-10%SO(3)H) is related to the more hydrophobic microenvironment of -SO(3)H sites, which reduces the acid site deactivation associated with adsorption of water generated during the reaction. Moreover, apparent activation energy is found to be 48.02 kJ mol(-1), which can be comparable with the literature values. PMID:22082796

Erdem, Beyhan; Kara, Ali

2012-02-01

77

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

NASA Astrophysics Data System (ADS)

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 m2 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.

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

2013-08-01

78

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

PubMed Central

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?m2 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

79

Reactivity and Characterization of Solid State Hydrodesulfurization Catalysts.  

NASA Astrophysics Data System (ADS)

The identification of the phase responsible for hydrodesulfurization (HDS) activity has been the subject of extensive research. In this study, model solid state catalysts prepared from elemental starting materials were synthesized, characterized, and then used to desulfurize thiophene at temperatures ranging from 200-400 ^circC and a pressure of one atmosphere. The results of this work indicate that an increased HDS activity can be correlated with the presence of a poorly crystalline molybdenum sulfide-like phase detected by XRD, HREM, or AEM. The formation of this sulfur-deficient, non-stoichiometric phase could be accomplished by either removing sulfur directly from the catalyst synthesis mixture to yield a non-stoichiometric MoS_{ rm 2-x} moiety, or by introducing a transition metal promoter such as Fe, Co, Ni, or Cu into the system. The promoter atoms induced structural changes in the molybdenum sulfide edge planes by effectively scavenging sulfur during catalyst synthesis to form promoter sulfide species, which enhanced the formation of a non-stoichiometric, highly active molybdenum sulfide. This morphological effect was the primary function of the promoter in this system. All model catalysts displayed similar structure in the (0002) basal plane of MoS_2; however, only the catalytically active samples showed a high concentration of defects and disorder in the (1010), (1011), and (1012) edge planes. The HREM images obtained from these edge planes and their correlation with HDS activity dramatically illustrated the importance of the often-discussed edge plane structure of MoS_2 and its significance on HDS catalysis. Normalization of the HDS activities for the solid state models and a commercial catalyst with O_2 or CO chemisorption uptakes suggested that a similarity may exist between the catalytically active sites of these materials. In-situ XPS revealed that increasing promoter atom concentrations resulted in a more complete reduction of the promoter atom; but this shift to lower binding energies could not necessarily be correlated with activity. However, it was observed that the more active catalysts all exhibited the ability to dissociate H_2 and remove oxygen from their surface. This H_2 spillover or activation may also influence catalyst performance.

Lindner, James Henry

1990-01-01

80

Biodiesel production process by homogeneous\\/heterogeneous catalytic system using an acid–base catalyst  

Microsoft Academic Search

The transesterification of triglycerides contained in waste oilseed fruits with methanol has been studied in heterogeneous\\/homogeneous systems using acid and base catalysts. The acid catalysts (strong acid catalysts: USY, BEA, FAU-X, and weak acid catalysts: MCM-41 and ITQ-6 with Si\\/Al=?) were prepared by hydrothermal synthesis procedures. In order to obtain acid–base catalysts, potassium was loaded on different materials by ionic

Anastasia Macario; Girolamo Giordano; Barbara Onida; Donato Cocina; Antonio Tagarelli; Angelo Maria Giuffrè

2010-01-01

81

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

82

LOW ACID PRODUCING SOLID PROPELLANTS  

E-print Network

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 HCl 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.

Dr. Robert; R. Bennett

83

Synergism of Clay and Heteropoly Acids as Nano-Catalysts for the Development of Green Processes with Potential Industrial Applications  

Microsoft Academic Search

A large number of inorganic oxides, mixed oxides, including alumina, silica, titania, zirconia, zeolites, carbon, clays and ion exchange resins have been employed as both supports and solid acid catalysts. Clay structure collapses at high temperatures and has to be stablilized. The thermal stability and pore size issues were addressed by pillaring of clays. Natural clays are acid treated or

Ganapati D. Yadav

2005-01-01

84

Upgrading of natural gasoline with trifluoromethane sulfonic acid, hydrofluoric acid and Lewis acid catalyst  

SciTech Connect

Natural gasoline of low octane value derived from natural gas is upgraded to higher octane value by means of a liquid ternary catalyst comprising trifluoromethane-sulfonic acid and hydrogen fluoride in conjunction with a Lewis acid of the formula MX /SUB n/ wherein M is selected from Group III-A, IV-B or V elements of the Periodic Table, x is a halogen and n is a number varying from 3 to 6. Effective upgrading is achieved when the Lewis acid:HF mole ratio of the catalyst ranges from 1:2 to 2:1 at temperatures less than about 120/sup 0/ C. under liquid phase conditions.

Olah, G.A.

1984-09-18

85

Ceria-based solid catalysts for organic chemistry.  

PubMed

Ceria has been the subject of thorough investigations, mainly because of its use as an active component of catalytic converters for the treatment of exhaust gases. However, ceria-based catalysts have also been developed for different applications in organic chemistry. The redox and acid-base properties of ceria, either alone or in the presence of transition metals, are important parameters that allow to activate complex organic molecules and to selectively orient their transformation. Pure ceria is used in several organic reactions, such as the dehydration of alcohols, the alkylation of aromatic compounds, ketone formation, and aldolization, and in redox reactions. Ceria-supported metal catalysts allow the hydrogenation of many unsaturated compounds. They can also be used for coupling or ring-opening reactions. Cerium atoms can be added as dopants to catalytic system or impregnated onto zeolites and mesoporous catalyst materials to improve their performances. This Review demonstrates that the exceptional surface (and sometimes bulk) properties of ceria make cerium-based catalysts very effective for a broad range of organic reactions. PMID:20486156

Vivier, Laurence; Duprez, Daniel

2010-06-21

86

Electrochemical catalyst recovery method  

DOEpatents

A method of recovering catalyst material from latent catalyst material solids includes: a) combining latent catalyst material solids with a liquid acid anolyte solution and a redox material which is soluble in the acid anolyte solution to form a mixture; b) electrochemically oxidizing the redox material within the mixture into a dissolved oxidant, the oxidant having a potential for oxidation which is effectively higher than that of the latent catalyst material; c) reacting the oxidant with the latent catalyst material to oxidize the latent catalyst material into at least one oxidized catalyst species which is soluble within the mixture and to reduce the oxidant back into dissolved redox material; and d) recovering catalyst material from the oxidized catalyst species of the mixture. The invention is expected to be particularly useful in recovering spent catalyst material from petroleum hydroprocessing reaction waste products having adhered sulfides, carbon, hydrocarbons, and undesired metals, and as well as in other industrial applications.

Silva, Laura J. (Richland, WA); Bray, Lane A. (Richland, WA)

1995-01-01

87

Electrochemical catalyst recovery method  

DOEpatents

A method of recovering catalyst material from latent catalyst material solids includes: (a) combining latent catalyst material solids with a liquid acid anolyte solution and a redox material which is soluble in the acid anolyte solution to form a mixture; (b) electrochemically oxidizing the redox material within the mixture into a dissolved oxidant, the oxidant having a potential for oxidation which is effectively higher than that of the latent catalyst material; (c) reacting the oxidant with the latent catalyst material to oxidize the latent catalyst material into at least one oxidized catalyst species which is soluble within the mixture and to reduce the oxidant back into dissolved redox material; and (d) recovering catalyst material from the oxidized catalyst species of the mixture. The invention is expected to be particularly useful in recovering spent catalyst material from petroleum hydroprocessing reaction waste products having adhered sulfides, carbon, hydrocarbons, and undesired metals, and as well as in other industrial applications. 3 figs.

Silva, L.J.; Bray, L.A.

1995-05-30

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

Green chemistry: Biodiesel made with sugar catalyst  

Microsoft Academic Search

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.

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

2005-01-01

90

Heterogeneous catalysts for the production of anthraquinone from 2-benzoylbenzoic acid  

Microsoft Academic Search

In the present paper, the dehydration reaction of 2-benzoylbenzoic acid (BBA) has been investigated in the presence of different heterogeneous catalysts, based on heteropoly acids (polyoxometalates), by using, in a first approach, a batch reactor for screening the best catalysts and, in a second step, a pseudo-continuous multifunctional reactor for determining reaction yields, catalysts productivity and deactivation of the catalyst

R. Tesser; M. Di Serio; M. Ambrosio; E. Santacesaria

2002-01-01

91

The influence of oxygen mobility in solid catalyst on transient regimes of catalytic reaction  

Microsoft Academic Search

Mathematical modeling of the influence of oxygen mobility in solid catalyst on transient regimes of catalytic reaction has been carried out. The region of Thiele modulus ? in which the diffusion of oxygen in solid catalyst effect on the transient regime of reaction was determined. These values of ? lies in the interval of 0.7–7. The diffusion coefficient corresponding to

N. M. Ostrovskii; S. I. Reshetnikov

2005-01-01

92

Pyruvic acid production using methylotrophic yeast transformants as catalyst  

Microsoft Academic Search

Permeabilized transformants of the methylotrophic yeasts Hansenula polymorpha and Pichia pastoris which express both the glycolate oxidase ((S)-2-hydroxyacid oxidase, EC 1.1.3.15) from spinach and an endogenous catalase (EC 1.11.1.6) have been used as catalysts for the oxidation of l-lactic acid to pyruvic acid. Oxidations of the sodium or ammonium salts of l-lactate at concentrations of up to 1.06 M were

Amy Eisenberg; John E. Seip; John E. Gavagan; Mark S. Payne; David L. Anton; Robert DiCosimo

1997-01-01

93

On the acidity and reactivity of highly effective chiral Brønsted acid catalysts: establishment of an acidity scale.  

PubMed

Stronger acid, higher speed: The pKa ?values of a range of binol-derived Brønsted acids of three different types were measured and found to correlate directly with the catalytic properties of the acids: higher rate constants kI were observed for more acidic Brønsted acid catalysts (see plot; binol=1,1'-bi-2-naphthol). PMID:24039083

Kaupmees, Karl; Tolstoluzhsky, Nikita; Raja, Sadiya; Rueping, Magnus; Leito, Ivo

2013-10-25

94

Corrosion-resistant catalyst supports for phosphoric acid fuel cells  

SciTech Connect

High-surface-area carbon blacks such as Vulcan XC-72 (Cabot Corp.) and graphitized carbon blacks such as 2700{degree}C heat-treated Black Pearls 2000 (HTBP) (Cabot Corp.) have found widespread applications as catalyst supports in phosphoric acid fuel cells (PAFCs). However, due to the operating temperatures and pressures being utilized in PAFCs currently under development, the carbon-based cathode catalyst supports suffer from corrosion, which decreases the performance and life span of a PAFC stack. The feasibility of using alternative, low-cost, corrosion-resistant catalyst support (CRCS) materials as replacements for the cathode carbon support materials was investigated. The objectives of the program were to prepare high-surface-area alternative supports and to evaluate the physical characteristics and the electrochemical stability of these materials. The O{sub 2} reduction activity of the platinized CRCS materials was also evaluated. 2 refs., 3 figs.

Kosek, J.A.; Cropley, C.C.; LaConti, A.B.

1990-01-01

95

Corrosion-resistant catalyst supports for phosphoric acid fuel cells  

NASA Astrophysics Data System (ADS)

High-surface-area carbon blacks such as Vulcan XC-72 (Cabot Corp.) and graphitized carbon blacks such as 2700 C heat-treated Black Pearls 2000 (HTBP) (Cabot Corp.) have found widespread applications as catalyst supports in phosphoric acid fuel cells (PAFCs). However, due to the operating temperatures and pressures being utilized in PAFCs currently under development, the carbon-based cathode catalyst supports suffer from corrosion, which decreases the performance and life span of a PAFC stack. The feasibility of using alternative, low-cost, corrosion-resistant catalyst support (CRCS) materials as replacements for the cathode carbon support materials was investigated. The objectives of the program were to prepare high-surface-area alternative supports and to evaluate the physical characteristics and the electrochemical stability of these materials. The O2 reduction activity of the platinized CRCS materials was also evaluated.

Kosek, J. A.; Cropley, C. C.; Laconti, A. B.

96

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

97

Thermally decomposed mesoporous Nickel Iron hydrotalcite: an active solid-base catalyst for solvent-free Knoevenagel condensation.  

PubMed

Thermal decomposition of co-precipitated Ni-Fe-HT materials led to the formation a mesoporous Ni-Fe-HT catalyst and we have demonstrated here its active role as solid and active catalyst for the Knoevenagel condensation reaction of various aldehydes with active methylene compounds (R-CH2-CN, where R=CN or CO2Et). High product yields are obtained at moderate temperature under solvent-free conditions and the catalyst can be easily separated from the reaction mixture, simply by filtration and reused several times without a significant loss of its activity. Since these mesoporous metal oxides derived from the NiFe hydrotalcites, their basicity mediated abstraction of the acidic protons from the active methylene compounds was responsible for their catalytic activity under solvent-free conditions. PMID:25490562

Dumbre, Deepa K; Mozammel, Tibra; Selvakannan, Pr; Hamid, Sharifah Bee Abdul; Choudhary, Vasant R; Bhargava, Suresh K

2015-03-01

98

Kl-impregnated Oyster Shells as a Solid Catalyst for Soybean Oil Transesterificaton  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

99

Acetic Acid from the Carbonylation of Chloride Methane Over Rhodium Based Catalysts  

E-print Network

Acetic Acid from the Carbonylation of Chloride Methane Over Rhodium Based Catalysts Yafang Fan Æ Chloride methane Á Carbonylation Á Rhodium catalysts 1 Introduction The conversion of natural gas has be carbonylated by carbon monoxide over rhodium-based catalyst to produce acetic acid [14]. The possibility

Bao, Xinhe

100

Novel Solid Base Catalysts for the Production of Biodiesel from Lipids  

E-print Network

and stability for biodiesel production still remains a challenge. This dissertation is dedicated to developing novel solid base catalysts and applying them to an environmentally beneficial reactive distillation process for transesterification of vegetable oils...

Zhao, Lina

2010-12-17

101

Proton conducting membrane using a solid acid  

NASA Technical Reports Server (NTRS)

A solid acid material is used as a proton conducting membrane in an electrochemical device. The solid acid material can be one of a plurality of different kinds of materials. A binder can be added, and that binder can be either a nonconducting or a conducting binder. Nonconducting binders can be, for example, a polymer or a glass. A conducting binder enables the device to be both proton conducting and electron conducting. The solid acid material has the general form M.sub.a H.sub.b (XO.sub.t).sub.c.

Chisholm, Calum (Inventor); Narayanan, Sekharipuram R. (Inventor); Boysen, Dane (Inventor); Haile, Sossina M. (Inventor)

2002-01-01

102

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

103

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

1967-01-01

104

Proton conducting membrane using a solid acid  

NASA Technical Reports Server (NTRS)

A solid acid material is used as a proton conducting membrane in an electrochemical device. The solid acid material can be one of a plurality of different kinds of materials. A binder can be added, and that binder can be either a nonconducting or a conducting binder. Nonconducting binders can be, for example, a polymer or a glass. A conducting binder enables the device to be both proton conducting and electron conducting.

Haile, Sossina M. (Inventor); Chisholm, Calum (Inventor); Boysen, Dane A. (Inventor); Narayanan, Sekharipuram R. (Inventor)

2006-01-01

105

Sulphamic Acid (H2NSO3H): A Low Cost, Mild and an Efficient Catalyst for the Synthesis of Substituted N-Phenylpyrazoles Under Solvent-Free Conditions  

Microsoft Academic Search

N-phenylpyrazoles are synthesized by condensing phenylhydrazine and 1,3-diketones in the presence of catalytic amount of sulphamic acid, a mild and an efficient solid acid catalyst, under solvent-free conditions. This condensation proceeds smoothly in shorter reaction time.

Mohan R. Shetty; Shriniwas D. Samant

2011-01-01

106

Sulfamic Acid (H2NSO3H): A Low-Cost, Mild, and Efficient Catalyst for the Synthesis of Substituted N-Phenylpyrazoles Under Solvent-Free Conditions  

Microsoft Academic Search

N-Phenylpyrazoles are synthesized by condensing phenylhydrazine and 1,3-diketones in the presence of a catalytic amount of sulfamic acid, a mild and an efficient solid acid catalyst, under solvent-free conditions. This condensation proceeds smoothly in shorter reaction time.

Mohan R. Shetty; Shriniwas D. Samant

2012-01-01

107

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

108

Preyssler catalyst, [NaP 5W 30O 110] 14?: A green, efficient and reusable catalyst for esterification of salicylic acid with aliphatic and benzylic alcohols  

Microsoft Academic Search

A series of eco-friendly solid acid catalysts, including H14[NaP5W30O110], H14–P5, H14[NaP5W29MoO110], H14–P5Mo, and silica supported H14[NaP5W30O110], H14–P5\\/SiO2 have been used as catalysts for esterification of salicylic acid with aliphatic alcohols (methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, t-butanol, 1-pentanol, and 2-pentanol) and benzylic alcohols (benzyl, 2-methylbenzyl, 2-chlorobenzyl, 4-bromobenzyl, 3-nitrobenzyl, and 4-methoxy benzyl) alcohol.The performance of different forms of Preyssler's anion in the

Fatemeh F. Bamoharram; Majid M. Heravi; Mina Roshani; Manochehr Jahangir; Ali Gharib

2006-01-01

109

Non-noble catalysts and catalyst supports for phosphoric acid fuel cells  

NASA Technical Reports Server (NTRS)

Four different samples of the cubic alloys W sub x-1 Ti sub x C sub 1-y were prepared and found to be active and CO tolerant. When the activities of these cubic alloys were weighted by the reciprocal of the square of the W exchange, they displayed magnitudes and dependence on bulk C deficiency comparable to those of highly active forms of WC. It is concluded that they may offer important insight into the nature of the active sites on, and means for improving the performance of, W-C anode catalysts for use in phosphoric acid fuel cells.

Mcalister, A. J.

1981-01-01

110

Non-noble catalysts and catalyst supports for phosphoric acid fuel cells  

NASA Technical Reports Server (NTRS)

Tungsten carbide, which is known to be active for hydrogen oxidation and CO tolerant has a hexagonal structure. Titanium carbide is inactive and has a cubic structure. Four different samples of the cubic alloys Wx-1TixC were prepared and found to be active and CO tolerant. These alloys are of interest as possible phosphoric acid fuel cell catalysts. They also are of interest as opportunities to study the activity of W in a different crystalline environment and to correlate the activities of the surface sites with surface composition.

Mcalister, A. J.

1980-01-01

111

Non-noble catalysts and catalyst supports for phosphoric acid fuel cells  

NASA Technical Reports Server (NTRS)

Tungsten carbide, which is active for hydrogen oxidation, is CO tolerant and has a hexagonal structure is discussed. Titanium carbide is inactive and has a cubic structure. Four different samples of the cubic alloys W sub x-1Ti sub XC sub 1-y were found to be active and CO tolerant. When the activities of these cubic alloys are weighted by the reciprocal of the square to those of highly forms of WC. They offer important insight into the nature of the active sites on W-C anode catalysts for use in phosphoric acid fuel cells.

Mcalister, A. J.

1981-01-01

112

Highly efficient esterification of carboxylic acids with alcohols by montmorillonite-enwrapped titanium as a heterogeneous acid catalyst  

Microsoft Academic Search

Montmorillonite-enwrapped titanium catalyst was found to efficiently promote the esterification of carboxylic acids with alcohols. In comparison to other catalysts reported to date, this heterogeneous catalyst offers a remarkably simple workup procedure, and is reusable without any appreciable loss in its activity and selectivity.

Tomonori Kawabata; Tomoo Mizugaki; Kohki Ebitani; Kiyotomi Kaneda

2003-01-01

113

Synthesis of a Novel Carbon Based Strong Acid Catalyst Through Hydrothermal Carbonization  

Microsoft Academic Search

A novel carbon based strong acid catalyst has been synthesized through the sulfonation of the carbon materials from glucose.\\u000a The novel acid catalyst was obtained through the hydrothermal carbonization instead of the traditional heat treatment, which\\u000a made the carbonization process under much milder condition with higher yield. The novel heterogeneous catalyst owned the advantages\\u000a of high acidity as much as

Xuezheng Liang; Jianguo Yang

2009-01-01

114

Production of glycolic acid from glycerol using novel fine-disperse platinum catalysts  

NASA Astrophysics Data System (ADS)

Using extractive-pyrolytic method fine-disperse Pt containing composites were synthesized and tested in catalytic glycerol oxidation. Catalyst activity and selectivity to glycolic acid was determined oxidizing glycerol in mild conditions. It was concluded that only iron containing platinum catalysts were selective to glycolic acid. Selectivity to glycolic acid reached 53-60% with glycerol conversion 12-56%.

Sproge, E.; Chornaja, S.; Dubencovs, K.; Kampars, V.; Kulikova, L.; Serga, V.; Karashanova, D.

2015-03-01

115

Catalytic synthesis of benzoic esters with carbon-based solid acid from coal tar  

Microsoft Academic Search

A new carbon-based solid acid catalyst (C- SO3H) was prepared by simultaneous cross- linking coal tar with benzaldehyde,hoist temperature -curing ,sulphonation in sulfuric acid and was characterized by FT-IR,TG-DTG,XRD and neutralization potentiometric titration, and SEM techniques. The results indicated that there is the high density of SO3H groups in forming amorphous coke consisting of polycyclic aromatic carbon sheets, and the

Haie Hao; Baojun Ma; Jinxin Ma; Sun Yuan; Wanyi Liu

2011-01-01

116

Sulfonic acid-functionalized ?-zirconium phosphate single-layer nanosheets as a strong solid acid for heterogeneous catalysis applications.  

PubMed

Solid acids have received considerable attention as alternatives to traditional corrosive and hazardous homogeneous acids because of their advantages in practical applications, including their low corrosion of equipment and high catalytic activity and recyclability. In this work, a strong solid acid was prepared by anchoring thiol group terminated chains on layered ?-zirconium phosphate (ZrP) single-layer nanosheets, followed by oxidation of thiol groups to form sulfonic acid groups. The obtained solid acids were thoroughly characterized and the results proved that sulfonic acid group terminated chains were successfully grafted onto the ZrP nanosheets with a high loading density. Such a strong solid acid based on inorganic nanosheets can be well-dispersed in polar solvents, leading to high accessibility to the acid functional groups. Meanwhile, it can be easily separated from the dispersion system by centrifugation or filtration. The strong solid acid can serve as an effective heterogeneous catalyst for various reactions, including the Bayer-Villiger oxidation of cyclohexanone to ?-caprolactone in the absence of organic solvents. PMID:24708469

Zhou, Yingjie; Huang, Rongcai; Ding, Fuchuan; Brittain, Alex D; Liu, Jingjing; Zhang, Meng; Xiao, Min; Meng, Yuezhong; Sun, Luyi

2014-05-28

117

Selective oxidation of glucose to gluconic acid over Pd–Te supported catalysts  

Microsoft Academic Search

The effect of tellurium introduction on the activity and selectivity of home-made supported palladium catalysts in the oxidation of glucose to gluconic acid was studied. Bimetallic Pd–Te\\/SiO2 and Pd–Te\\/Al2O3 catalysts containing 5wt.% of Pd and 0.3–5wt.% of Te are characterized by both high activity and high selectivity to gluconic acid. However, catalysts 5%Pd–8%Te\\/support show lower conversion but their selectivity to

I. Wito?ska; M. Frajtak; S. Karski

2011-01-01

118

Solid-state NMR studies of the adsorption of acetylene on platinum/alumina catalysts  

E-print Network

SOLID-STATE NMR STUDIES OF THE ADSORPTION OF ACETYLENE ON PLATINUM/ALUMINA CATALYSTS A Thesis by MARSHA JO LUPHER LAMBREGTS Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements... for the degree of MASTER OF SCIENCE December 1991 Major Subject: Chemistry SOLID-STATE NMR STUDIES OF THE ADSORPTION OF ACETYLENE ON PLATINUM/ALUMINA CATALYSTS A Thesis by MARSHA JO LUPHER LAMBREGTS Approved as to style and content by: ames F. Haw...

Lambregts, Marsha Jo Lupher

1991-01-01

119

Novel SBA15 supported heteropoly acid catalysts for benzene alkylation with 1-dodecene  

Microsoft Academic Search

Phosphotungstic acid (PW) catalysts supported on the mesoporous molecular sieve SBA-15 have been prepared, characterized and evaluated in the alkylation reaction of benzene with 1-dodecene. SBA-15 supported PW catalysts exhibit much higher catalytic activity, stability and selectivity compared with HY zeolite. It is proposed that the high dispersion of PW on SBA-15, high surface area, mesoporosity and specific acidity of

Hai-Ou Zhu; Jun Wang; Chong-Yu Zeng; Dong-Yuan Zhao

2003-01-01

120

Comparison of catalysts for direct transesterification of fatty acids in freeze-dried forage samples  

Technology Transfer Automated Retrieval System (TEKTRAN)

Preparation of fatty acid methyl esters from forages comparing BF3 in CH3OH to HCl in CH3OH as a catalyst in single-step direct transesterification has not been reported. Our objective was to compare 1.09 M methanolic HCl to 7% BF3 in CH3OH as catalysts for direct transesterification of fatty acids ...

121

Gas Phase Catalytic Oxidation of ?-Picoline to Nicotinic Acid: Catalysts, Mechanism and Reaction Kinetics  

Microsoft Academic Search

An overview of the fundamental studies on a new method of nicotinic acid synthesis by the gas phase catalytic oxidation of ?-picoline by oxygen is presented. The nature of active component in vanadia catalysts and reactivity of vanadium species are considered. Common features and differences in the mechanistic steps of nicotinic acid formation on various catalysts investigated by in situ

Tamara V. Andrushkevich; Elena V. Ovchinnikova

2012-01-01

122

Acidity and catalytic activity of polyfunctional zeolite catalysts in the benzene-propene-diisopropylbenzene system  

Microsoft Academic Search

Studies on the effect of the acidity of polyfunctional zeolite catalysts on their activity in benzene alkylation by propene and its transalkylation by diisopropylbenzene (DIPB) have revealed that alkylation and transalkylation of aromatics proceed on catalytic centers of different acidity.

I. I. Lishchiner; V. A. Plakhotnik; D. Z. Levin; E. S. Mortikov; V. F. Ilyin

1983-01-01

123

Methane oxidation over SrCeO[sub 3] catalysts: Effect of solid-state reaction temperature  

Microsoft Academic Search

SrCeO[sub 3] catalysts were prepared by solid-state reaction at 750--1400 C. The catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy, and temperature-programmed desorption (TPD) of CO[sub 2]. The surface area of the catalysts decreased with increasing solid-state reaction temperature. The rate equation of the methane oxidation was obtained as r[sub CO[sub x

Hidetoshi Nagamoto; Eiji Shinoda; Hakuai Inoue

1993-01-01

124

Efficient hydrogen generation from sodium borohydride hydrolysis using silica sulfuric acid catalyst  

NASA Astrophysics Data System (ADS)

A heterogeneous acid catalyst, silica sulfuric acid, was prepared from silica gel (SiO2) and sulfuric acid (H2SO4). Addition of SO3H functional group to SiO2 has been confirmed through various characterization techniques. The effect of this heterogeneous acid catalyst on hydrogen generation from sodium borohydride hydrolysis reaction was studied for different ratios of catalyst to NaBH4 and at different temperatures. The catalyst exhibited high catalytic activity towards sodium borohydride hydrolysis reaction. The activation energy of the NaBH4 hydrolysis reaction in the presence of silica sulfuric acid was calculated to be the lowest (17 kJ mol-1) among reported heterogeneous catalysts till date.

Manna, Joydev; Roy, Binayak; Sharma, Pratibha

2015-02-01

125

Solid acids as fuel cell electrolytes.  

PubMed

Fuel cells are attractive alternatives to combustion engines for electrical power generation because of their very high efficiencies and low pollution levels. Polymer electrolyte membrane fuel cells are generally considered to be the most viable approach for mobile applications. However, these membranes require humid operating conditions, which limit the temperature of operation to less than 100 degrees C; they are also permeable to methanol and hydrogen, which lowers fuel efficiency. Solid, inorganic, acid compounds (or simply, solid acids) such as CsHSO4 and Rb3H(SeO4)2 have been widely studied because of their high proton conductivities and phase-transition behaviour. For fuel-cell applications they offer the advantages of anhydrous proton transport and high-temperature stability (up to 250 degrees C). Until now, however, solid acids have not been considered viable fuel-cell electrolyte alternatives owing to their solubility in water and extreme ductility at raised temperatures (above approximately 125 degrees C). Here we show that a cell made of a CsHSO4 electrolyte membrane (about 1.5 mm thick) operating at 150-160 degrees C in a H2/O2 configuration exhibits promising electrochemical performances: open circuit voltages of 1.11 V and current densities of 44 mA cm-2 at short circuit. Moreover, the solid-acid properties were not affected by exposure to humid atmospheres. Although these initial results show promise for applications, the use of solid acids in fuel cells will require the development of fabrication techniques to reduce electrolyte thickness, and an assessment of possible sulphur reduction following prolonged exposure to hydrogen. PMID:11309611

Haile, S M; Boysen, D A; Chisholm, C R; Merle, R B

2001-04-19

126

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

127

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

128

Acid–base titration curves of solid humic acids  

Microsoft Academic Search

A direct discontinuous titration method with NaOH was developed to characterize the acid–base properties of complex natural polyelectrolytes, such as humic substances (HS). The classical batch procedure, suggested originally for examinations of resin-based ion exchanger, was modified to be applicable to HS; the modified method is suitable especially for the measurements of the titration curves of solid humic acids (HA).

Pavel Janoš; Sylvie K?íženecká; Libuše Madronová

2008-01-01

129

Solid acids as substitutes for sulfuric acid in the liquid phase nitration of toluene to nitrotoluene and dinitrotoluene  

Microsoft Academic Search

Our results demonstrate that sulfuric acid supported on preshaped silica is a good catalyst for the nitration of toluene to dinitrotoluene using 65wt.% nitric acid with respect to catalyst performance (activity, selectivity, regenerability) and catalyst handling (storage, stirring, separation). It is imperative to carefully control the water content of the catalyst prior to reaction in order to obtain high activity.

Andreas Kogelbauer; Diego Vassena; Roel Prins; John N Armor

2000-01-01

130

Green acetylation of solketal and glycerol formal by heterogeneous acid catalysts to form a biodiesel fuel additive.  

PubMed

A glut of glycerol has formed from the increased production of biodiesel, with the potential to integrate the supply chain by using glycerol additives to improve biodiesel properties. Acetylated acetals show interesting cold flow and viscosity effects. Herein, a solventless heterogeneously catalyzed process for the acetylation of both solketal and glycerol formal to new products is demonstrated. The process is optimized by studying the effect of acetylating reagent (acetic acid and acetic anhydride), reagent molar ratios, and a variety of commercial solid acid catalysts (Amberlyst-15, zeolite Beta, K-10 Montmorillonite, and niobium phosphate) on the conversion and selectivities. High conversions (72-95%) and selectivities (86-99%) to the desired products results from using acetic anhydride as the acetylation reagent and a 1:1 molar ratio with all catalysts. Overall, there is a complex interplay between the solid catalyst, reagent ratio, and acetylating agent on the conversion, selectivities, and byproducts formed. The variations are discussed and explained in terms of reactivity, thermodynamics, and reaction mechanisms. An alternative and efficient approach to the formation of 100% triacetin involves the ring-opening, acid-catalyzed acetylation from solketal or glycerol formal with excesses of acetic anhydride. PMID:25045049

Dodson, Jennifer R; Leite, Thays d C M; Pontes, Nathália S; Peres Pinto, Bianca; Mota, Claudio J A

2014-09-01

131

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...

132

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...

133

In situ biodiesel production from greasy sewage sludge using acid and enzymatic catalysts.  

PubMed

This study proposes to select the most appropriate sewage sludge (greasy, primary and secondary) for in situ transesterification and to compare the technical, economic and energetic performance of an enzymatic catalyst (Novozym®435) with sulfuric acid. Greasy sludge was selected as feedstock for biodiesel production due to its high lipid content (44.4%) and low unsaponifiable matter. Maximum methyl esters yield (61%) was reached when processing the wet sludge using sulfuric acid as catalyst and n-hexane, followed by dried-greasy sludge catalyzed by Novozym®435 (57% methyl esters). Considering the economic point of view, the process using acid catalyst was more favorable compared to Novozym®435 catalyst due to the high cost of lipase. In general, greasy sludge (wet or dried) showed high potential to produce biodiesel. However, further technical adjustments are needed to make biodiesel production by in situ transesterification using acid and enzymatic catalyst feasible. PMID:25528605

Sangaletti-Gerhard, Naiane; Cea, Mara; Risco, Vicky; Navia, Rodrigo

2015-03-01

134

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

135

Low-temperature, vapor–liquid–solid, laterally grown silicon films using alloyed catalysts  

NASA Astrophysics Data System (ADS)

Using amorphous oxide templates known as micro-crucibles which confine a vapor–liquid–solid catalyst to a specific geometry, two-dimensional silicon thin-films of a single orientation have been grown laterally over an amorphous substrate and defects within crystals have been necked out. The vapor–liquid–solid catalysts consisted nominally of 99% gold with 1% titanium, chromium, or aluminum, and each alloy affected the processing of micro-crucibles and growth within them significantly. It was found that chromium additions inhibited the catalytic effect of the gold catalysts, titanium changed the morphology of the catalyst during processing and aluminum stabilized a potential third phase in the gold–silicon system upon cooling. Two mechanisms for growing undesired nanowires were identified both of which hindered the VLS film growth, fast silane cracking rates and poor gold etching, which left gold nanoparticles near the gold–vapor interface. To reduce the silane cracking rates, growth was done at a lower temperature while an engineered heat and deposition profile helped to reduce NWs caused by the second mechanism. Through experimenting with catalyst compositions, the fundamental mechanisms which produce concentration gradients across the gold–silicon alloy within a given micro-crucible have been proposed. Using the postulated mechanisms, micro-crucibles were designed which promote high-quality, single crystal growth of semiconductors.

LeBoeuf, Jerome L.; Brodusch, Nicolas; Gauvin, Raynald; Quitoriano, Nathaniel J.

2014-12-01

136

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

137

Synthesis and catalytic properties of porous Nb–Mo oxide solid acid  

Microsoft Academic Search

Several porous NbxMo10?x mixed oxides prepared from NbCl5 and MoCl5 in the presence of block copolymer surfactant Pluronic P-123 were examined as potential solid acid catalysts. Amorphous mesoporous structures were observed in samples with x from 10 to 9, whereas samples with higher Mo concentrations (x=3–8) formed large pores by inter-particle voids and a non-porous structures with crystallized molybdenum oxide

Caio Tagusagawa; Atsushi Takagaki; Ai Iguchi; Kazuhiro Takanabe; Junko N. Kondo; Kohki Ebitani; Takashi Tatsumi; Kazunari Domen

2011-01-01

138

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

139

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.

The Concord Consortium

2011-12-11

140

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

141

Silica sulfuric acid a novel and heterogeneous catalyst for the synthesis of some new oxindole derivatives  

Microsoft Academic Search

Silica sulfuric acid catalyzed efficiently the electrophilic substitution reaction of an indoles with various isatins in dicholoro methane to afford the corresponding oxindoles derivatives in high yields under r.t. The catalyst exhibited remarkable reusable activity.

Javad Azizian; Ali A. Mohammadi; Narges Karimi; Mohammad R. Mohammadizadeh; Ali R. Karimi

2006-01-01

142

Preparation and characterization of the phenolated wood using hydrochloric acid (HCl) as a catalyst  

Microsoft Academic Search

Summary  Birch (Betula maximowicziana Regel) wood meal was liquefied in the presence of phenol using hydrochloric acid (HCl) as a catalyst at a temperature of\\u000a 150 C for 2 h in an autoclave. It was found out that HCl acid could be used as an effective catalyst for the hydroxy phenylation\\u000a of wood under the experimental conditions. In this study the

M. H. Alma; M. Yoshioka; Y. Yao; N. Shiraishi

1995-01-01

143

Molybdenum phosphosulfide: an active, acid-stable, earth-abundant catalyst for the hydrogen evolution reaction.  

PubMed

Introducing sulfur into the surface of molybdenum phosphide (MoP) produces a molybdenum phosphosulfide (MoP|S) catalyst with superb activity and stability for the hydrogen evolution reaction (HER) in acidic environments. The MoP|S catalyst reported herein exhibits one of the highest HER activities of any non-noble-metal electrocatalyst investigated in strong acid, while remaining perfectly stable in accelerated durability testing. Whereas mixed-metal alloy catalysts are well-known, MoP|S represents a more uncommon mixed-anion catalyst where synergistic effects between sulfur and phosphorus produce a high-surface-area electrode that is more active than those based on either the pure sulfide or the pure phosphide. The extraordinarily high activity and stability of this catalyst open up avenues to replace platinum in technologies relevant to renewable energies, such as proton exchange membrane (PEM) electrolyzers and solar photoelectrochemical (PEC) water-splitting cells. PMID:25359678

Kibsgaard, Jakob; Jaramillo, Thomas F

2014-12-22

144

Amberlyst 15: A Practical, Mild and Selective Catalyst for Methyl Esterification of Carboxylic Acids  

Microsoft Academic Search

Mild and selective methyl esterification of carboxylic acids are realized using Amberlyst 15 as acid catalyst in methanol. No race mization, epimerization or ketalization products have been observed with this method. Excellent results are obtained in the esterifications of bile acids.

Marino Petrini; Roberto Ballini; Enrico Marcantoni; Goffredo Rosini

1988-01-01

145

A sup 95 Mo solid-state NMR study of hydrodesulfurization catalysts. 1. Formation of fresh HDS catalyst precursors by adsorption of polyoxomolybdates onto. gamma. -alumina  

SciTech Connect

The solid-state {sup 95}Mo NMR of oxomolybdates and polyoxomolybdates adsorbed to {gamma}-alumina was utilized to characterize the molybdenum species present at circa monolayer coverages of molybdenum. This represents the first attempt at using solid-state NMR to look directly at the molybdenum species on the surface of 'fresh' hydrodesulfurization catalyst precursors. The selectively excited central {plus minus}1/2 transition line shapes were obtained, by the solid-echo technique, for several polyoxomolybdates, which are considered model compounds of the surface molybdena species, as well as for the uncalcined and calcined catalysts at various loadings. The spectra were obtained for static and magic angle spinning samples. Static sample spectra of the catalysts reveal inhomogeneously broadened lines owing to a range of surface species being present. Magic and angle spinning spectra show the presence of four possible species on the surface of the uncalcined catalysts and two possible species present on the surface of calcined catalysts. Spikelet echo spectra identified static adsorbed species (speculated to be predominantly adsorbed tetrahedral/octahedral molybdena, and perhaps Al{sub 2}(MoO{sub 4}){sub 3}), and a dynamic species (speculated to be disordered, surface-interactive tetrahedral and octahedral molybdates), in the uncalcined catalyst samples. Upon calcination the line widths of the static and MAS spectra are increased, indicating a polymerization of the surface species to form a MoO{sub 3}-like phase. 67 refs.

Edwards, J.C.; Adams, R.D.; Ellis, P.D. (Univ. of South Carolina, Columbia (United States))

1990-11-07

146

Direct preparation of dichloropropanol from glycerol and hydrochloric acid gas using heteropolyacid (HPA) catalyst by heterogeneous gas phase reaction  

Microsoft Academic Search

Direct preparation of dichloropropanol (DCP) from glycerol and hydrochloric acid gas was carried out in a heterogeneous gas phase reactor using H3PMo12?XWXO40 (X=0, 3, 6, 9, and 12), H4SiW12O40, and H4SiMo12O40 heteropolyacid (HPA) catalysts. Acid property of the HPA catalyst was determined by NH3-TPD measurement in order to correlate the catalytic activity with the acid property of the catalyst. Acid

Sun Ho Song; Dong Ryul Park; Sung Yul Woo; Won Seob Song; Myong Suk Kwon; In Kyu Song

2010-01-01

147

Advances in the Determination of the Architecture of Active Sites in Solid Catalysts  

Microsoft Academic Search

\\u000a We review some of the advances in the determination of the atomic architecture of solid catalysts, in particular using X-ray,\\u000a neutron scattering and spectroscopic techniques. The aim, wherever possible, is to arrive at such structures under operating\\u000a (catalytic) conditions. It is essential to retrieve such information in situ, because it then can serve as a realistic platform for the construction

G. Sankar; R. Raja; J. M. Thomas; D. Gleeson

148

Solid Solutions of WO 3into Zirconia in WO 3–ZrO 2 Catalysts  

Microsoft Academic Search

Catalysts in the WO3–ZrO2 system were produced by coprecipitation of aqueous solutions of zirconium oxynitrate and ammonium metatungstate. Samples were characterized by X-ray powder diffraction, thermogravimetry, and refinement of their crystalline structures with the Rietveld method. This coprecipitation gave rise to solid solutions of tungsten oxide into zirconia; the initial phase was amorphous and crystallized into two tetragonal crystalline phases,

M. A. Cortés-Jácome; J. A. Toledo-Antonio; H. Armendáriz; I. Hernández; X. Bokhimi

2002-01-01

149

Synthesis of aliphatic polyesters by polycondensation using inorganic acid as catalyst.  

PubMed

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. PMID:25473252

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

2011-04-01

150

Application of nanostuctured materials as acid-catalysts in rice straw pyrolysis for bio-oil production  

NASA Astrophysics Data System (ADS)

Rice straw, a waste agro-byproduct, which is abundant lignocellulose products from rice production, is a renewable energy sources in Vietnam. Bio-oil from rice straw is produced by thermal and catalytic pyrolysis using a fixed-bed reactor with heating rate 15oC/min, nitrogen as sweeping gas with flow rate 120ml/min. Final temperature of the pyrolysis reaction is a significantly influence on product yield. The gas yield increased and the solid yield decreased as the pyrolysis temperature increasing from 400oC to 600oC. The bio-oil yield reached a maximum of 48.3 % at the pyrolysis temperature of 550oC. Mesoporous Al-SBA-15 was used as acid catalyst in pyrolysis of rice straw. The obtained results showed that, in the presence of catalyst, yield of gas products increased, whereas liquid yield decreased and solid product remained the same as compared to the non-catalytic experiments. The effect of nanostructured catalysts on the product yields and distribution was investigated.

Dang, Phuong T.; Le, Hy G.; Dinh, Thang C.; Hoang, Thang V.; Bui, Linh H. T.; Hoang, Yen; Tran, Hoa K. T.; Vu, Tuan A.

2008-12-01

151

Chance and necessity in the selection of nucleic acid catalysts  

NASA Technical Reports Server (NTRS)

In Tom Stoppard's famous play [Rosencrantz and Guildenstern are Dead], the ill-fated heroes toss a coin 101 times. The first 100 times they do so the coin lands heads up. The chance of this happening is approximately 1 in 10(30), a sequence of events so rare that one might argue that it could only happen in such a delightful fiction. Similarly rare events, however, may underlie the origins of biological catalysis. What is the probability that an RNA, DNA, or protein molecule of a given random sequence will display a particular catalytic activity? The answer to this question determines whether a collection of such sequences, such as might result from prebiotic chemistry on the early earth, is extremely likely or unlikely to contain catalytically active molecules, and hence whether the origin of life itself is a virtually inevitable consequence of chemical laws or merely a bizarre fluke. The fact that a priori estimates of this probability, given by otherwise informed chemists and biologists, ranged from 10(-5) to 10(-50), inspired us to begin to address the question experimentally. As it turns out, the chance that a given random sequence RNA molecule will be able to catalyze an RNA polymerase-like phosphoryl transfer reaction is close to 1 in 10(13), rare enough, to be sure, but nevertheless in a range that is comfortably accessible by experiment. It is the purpose of this Account to describe the recent advances in combinatorial biochemistry that have made it possible for us to explore the abundance and diversity of catalysts existing in nucleic acid sequence space.

Lorsch, J. R.; Szostak, J. W.

1996-01-01

152

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

153

Cyclobutane amino acids and peptidomimetics, parallel catalyst screening for aziridination  

E-print Network

; and, the octapeptide synthesized in this study adapts an P-hairpin secondary structure, as evidenced by CD and 2D NMR. The second project is parallel catalyst screening for aziridination of olefins. Since aziridines are versatile intermediates...

Li, Shih-ming

1996-01-01

154

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

155

Stability of Supported Platinum Sulfuric Acid Decomposition Catalysts for use in Thermochemical Water Splitting Cycles  

SciTech Connect

The activity and stability of several metal oxide supported platinum catalysts were explored for the sulfuric acid decomposition reaction. The acid decomposition reaction is common to several sulfur based thermochemical water splitting cycles. Reactions were carried out using a feed of concentrated liquid sulfuric acid (96 wt%) at atmospheric pressure at temperatures between 800 and 850 °C and a weight hour space velocity of 52 g acid/g catalyst/hr. Reactions were run at these high space velocities such that variations in kinetics were not masked by surplus catalyst. The influence of exposure to reaction conditions was explored for three catalysts; 0.1-0.2 wt% Pt supported on alumina, zirconia and titania. The higher surface area Pt/Al2O3 and Pt/ZrO2 catalysts were found to have the highest activity but deactivated rapidly. A low surface area Pt/TiO2 catalyst was found to have good stability in short term tests, but slowly lost activity for over 200 hours of continuous operation.

Daniel M. Ginosar; Lucia M. Petkovic; Anne W. Glenn; Kyle C. Burch

2007-03-01

156

COMPARISON OF SODIUM HYPOPHOSPHITE WITH HYPOPHOSPHOROUS ACID AS CURING CATALYSTS FOR DP FINISHING WITH BTCA OR CITRIC ACID  

Technology Transfer Automated Retrieval System (TEKTRAN)

It has been suggested that when sodium hypophosphite (SHP) is used to catalyze crosslinking of cotton by 1,2,3,4-butanetetracarboxylic acid (BTCA) at 160-190 degrees C, the active catalyst may be free hypophosphorous acid, which could form a mixed linear anhydride with, and subsequently a cyclic anh...

157

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

158

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

159

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

160

Kinetics of xylose in hydrolysate using dilute sulphuric acid as catalyst  

Microsoft Academic Search

In the technology of manufacturing fuel alcohol from biomass as feedstock, hydrolysis using dilute acid as catalyst is one way to produce fermentable saccharide. In this process, the yield of xylose is always low because of the degrading during the acid environment. In this paper, the degrading kinetics of xylose in the hydrolysate was investigated under the conventional process conditions

Wei Qi; Suping Zhang; Qingli Xu; Zhenxing Zhu; Yongjie Yan Zhengwei Ren; Yongjie Yan

2009-01-01

161

Evaluating acid and base catalysts in the methylation of milk and rumen fatty acids with special emphasis on conjugated dienes and total trans fatty acids  

Microsoft Academic Search

Milk analysis is receiving increased attention. Milk contains conjugated octadecadienoic acids (18?2) purported to be anticarcinogenic,\\u000a low levels of essential fatty acids, and trans fatty acids that increase when essential fatty acids are increased in dairy rations. Milk and rumen fatty acid methyl esters\\u000a (FAME) were prepared using several acid-(HCl, BF3, acetyl chloride, H2SO4) or base-catalysts (NaOCH3, tetramethylguanidine, diazomethane), or

John K. G. Kramer; Vivek Fellner; Michael E. R. Dugan; Frank D. Sauer; Magdi M. Mossoba; Martin P. Yurawecz

1997-01-01

162

Highly efficient tetradentate ruthenium catalyst for ester reduction: especially for hydrogenation of fatty acid esters.  

PubMed

A new tetradentate ruthenium complex has been developed for hydrogenation of esters. The catalyst's structure features a pyridinemethanamino group and three tight chelating five-membered rings. The structure character is believed to be responsible for its high stability and high carbonylation-resistant properties. Thus, this catalyst shows outstanding performance in the catalytic hydrogenation of a variety of esters, especially for fatty acid esters, which may be used in practical applications. New insight on designing hydrogenation catalyst for reducing esters to alcohols has been provided through theoretical calculations. PMID:25582610

Tan, Xuefeng; Wang, Yan; Liu, Yuanhua; Wang, Fangyuan; Shi, Liyang; Lee, Ka-Ho; Lin, Zhenyang; Lv, Hui; Zhang, Xumu

2015-02-01

163

Platinum catalyst degradation in phosphoric acid fuel cells for stationary applications  

NASA Astrophysics Data System (ADS)

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 surface area change in these catalysts.

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

2011-05-01

164

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

165

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

166

The role of Brønsted acidity in the SCR of NO over Fe-MFI catalysts  

Microsoft Academic Search

The selective catalytic reduction (SCR) of NO with isobutane and with NH3 was studied over Fe-MFI catalysts which differ strongly in Brønsted acidity but are similar in Fe content and structure of Fe sites, having shown similar activity in N2O decomposition in related work. The catalysts were prepared by exchange of Na-ZSM-5 (Si\\/Al ca. 14) with Fe2+ ions formed in

Michael Schwidder; M. Santhosh Kumar; Ursula Bentrup; Javier Pérez-Ramírez; Angelika Brückner; Wolfgang Grünert

2008-01-01

167

Kinetics of benzene alkylation with 1-dodecene over a supported tungstophosphoric acid catalyst  

Microsoft Academic Search

The prepared catalyst of tungstophosphoric acid supported on SiO2 has shown high activity, good selectivity of producing linear alkylbenzene (LAB) and 2-phenyl isomer and sufficient catalytic stability. Kinetics of benzene alkylation with 1-dodecene over this catalyst was investigated in a fixed-bed reactor after eliminating the influence of internal and external transport. Rate models of formation of different isomers of LAB

Jinchang Zhang; Biaohua Chen; Chengyue Li; Zuogang Zhu; Langyou Wen; Enze Min

2003-01-01

168

Oligomerization of 2-methylpropene and transformation of 2,4,4-trimethyl-2-pentene over supported and unsupported perfluorinated resinsulfonic acid catalysts  

SciTech Connect

Oligomerization of 2-methylpropene was studied with two types of supported (on alumina and on silicon carbide) as well neat perfluorinated resinsulfonic acid catalysts. The heterogeneous reactions were carried out over the solid acid catalysts in a continuous flow reactor at temperatures between 85 and 170 C under atmospheric pressure. Under the studied conditions (85 to 105 C, 1 atm pressure, WHSV:1-3 g/g {center dot} h) all catalysts studied are suitable for oligomerization of 2-methyl-propene. Product distributions show regular temperature dependence: upon increasing temperature the molecular weight of oligomers decreases, with no difference in the selectivity of the catalysts. Transformation of 2,4,4-trimethyl-2-pentene in the liquid phase at room temperature shows surprising selectivity using either the hydrated or dehydrated forms of the resinsulfonic acids. In the case of the hydrated forms of the acids, only double bond isomerization takes place. With dehydrated acids oligomerization as well as isomerization occurs. Above 50 C the selectivity is lost.

Bucsi, I.; Olah, G.A. (Univ. of Southern California, University Park, Los Angeles (United States))

1992-09-01

169

Phosphotungstic acid supported on magnetic nanoparticles as an efficient reusable catalyst for epoxidation of alkenes  

SciTech Connect

Highlights: ? Phosphotungstic acid supported on functionalized cobalt ferrite was prepared. ? Silica coated cobalt ferrite nanoparticles were used as support. ? This composite was successfully used as catalyst for epoxidation of alkenes. ? Oxidation reactions were carried out in the presence of t-BuOOH as oxidant. ? The catalyst can be readily separated from solution by magnetic field. -- Abstract: A new magnetically separable catalyst consisting of phosphotungstic acid supported on imidazole functionalized silica coated cobalt ferrite nanoparticles was prepared. The synthesized catalyst was characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR), and inductively coupled plasma atomic emission spectroscopy (ICP-AES). This immobilized phosphotungstic acid was shown to be an efficient heterogeneous catalyst for the epoxidation of various alkenes using tert-butylhydroperoxide (t-BuOOH) as oxidant. The catalyst is readily recovered by simple magnetic decantation and can be recycled several times with no significant loss of catalytic activity.

Kooti, M., E-mail: m_kooti@scu.ac.ir [Department of Chemistry, College of Science, Shahid Chamran University, Ahvaz 61357- 43169 (Iran, Islamic Republic of); Afshari, M. [Department of Chemistry, College of Science, Shahid Chamran University, Ahvaz 61357- 43169 (Iran, Islamic Republic of)] [Department of Chemistry, College of Science, Shahid Chamran University, Ahvaz 61357- 43169 (Iran, Islamic Republic of)

2012-11-15

170

CoBr 2-MnBr 2 containing catalysts for catalytic oxidation of p-xylene to terephthalic acid  

Microsoft Academic Search

Catalytic oxidation of p-xylene (PX) to terephthalic acid (TA) was studied with catalysts containing cobalt acetate, manganese acetate, CoBr2 and MnBr2. The catalysts contain neither highly corrosive hydrogen bromide nor other metal ions, and have the advantage of easy catalyst recovery. The effects of Br\\/Co atomic ratio, reaction time and temperature, PX concentration, oxygen pressure, and catalyst concentration on PX

Kuo-Tseng Li; Shih-Wei Li

2008-01-01

171

Solid electrolyte aided study of the oxidation of hydrogen on copper and copper oxide catalysts  

SciTech Connect

The catalytic oxidation of hydrogen on copper and copper oxide surfaces was studied in a solid electrolyte cell at 250-365[degrees]C and 1 atm. The technique of solid electrolyte potentiometry (SEP) was used to monitor the thermodynamic activity of oxygen adsorbed on the catalyst surface during reaction. The oxygen activity value resulted from a steady-state mass balance of oxygen on the catalyst surface and under specific conditions, was several orders of magnitude lower than the gas-phase oxygen partial pressure. The stable phase of the solid was usually CuO and less frequently Cu[sub 2]O or metallic Cu. The reaction on reduced (Cu metal) surface exhibited much higher rates than on either oxide, while between the latter two, CuO was the least active surface. The rate-determining step on CuO was the surface reaction between atomically adsorbed hydrogen and oxygen. A kinetic model that quantitatively explains both kinetic and potentiometric measurements in the CuO regime is presented. 43 refs., 10 figs.

Balian, A.; Hatzigiannis, G.; Eng, D.; Stoukides, M. (Tufts Univ., Medford, MA (United States))

1994-02-01

172

Kinetics of liquid-solid reactions in naphthenic acid conversion and Kraft pulping  

NASA Astrophysics Data System (ADS)

Two liquid-solid reactions, in which the morphology of the solid changes as the reactions proceeds, were examined. One is the NA conversion in oil by decarboxylation on metal oxides and carbonates, and the other is the Kraft pulping in which lignin removal by delignification reaction. In the study of the NA conversion, CaO was chosen as the catalyst for the kinetic study from the tested catalysts based on NA conversion. Two reaction mixtures, carrier oil plus commercial naphthenic acids and heavy vacuum gas oil (HVGO) from Athabasca bitumen, were applied in the kinetic study. The influence of TAN, temperature, and catalyst loading on the NA conversion and decarboxylation were studied systematically. The results showed that the removal rate of TAN and the decarboxylation of NA were both independent of the concentration of NA over the range studied, and significantly dependent on reaction temperature. The data from analyzing the spent catalyst demonstrated that calcium naphthenate was an intermediate of the decarboxylation reaction of NA, and the decomposition of calcium naphthenate was a rate-determining step. In the study on the delignification of the Kraft pulping, a new mechanism was proposed for the heterogeneous delignification reaction during the Kraft pulping process. In particular, the chemical reaction mechanism took into account the heterogeneous nature of Kraft pulping. Lignin reacted in parallel with sodium hydroxide and sodium sulfide. The mechanism consists of three key kinetic steps: (1) adsorption of hydroxide and hydrosulfide ions on lignin; (2) surface reaction on the solid surface to produce degraded lignin products; and (3) desorption of degradation products from the solid surface. The most important step for the delignification process is the surface reaction, rather than the reactions occurring in the liquid phase. A kinetic model has, thus, been developed based on the proposed mechanism. The derived kinetic model showed that the mechanism could be employed to predict the pulping behavior under a variety of conditions with good accuracy.

Yang, Ling

173

Preparation of encaged heteropoly acid catalyst by synthesizing 12-molybdophosphoric acid in the supercages of Y-type zeolite  

Microsoft Academic Search

12-molybdophosphoric acid encaged in the supercages of Y-type zeolite was synthesized from molybdenum oxide and phosphoric acid, in a slurry mixture of Y-type zeolite crystals and deionized water. After thorough washing in hot water, the 12-molybdophosphoric acid was found to remain in the Y-type zeolite, at an amount estimated to be 0.09 g (g-support)?1. Catalysts thus obtained were found to

Shin R. Mukai; Takao Masuda; Isao Ogino; Kenji Hashimoto

1997-01-01

174

Removal of free fatty acid in waste frying oil by esterification with methanol on zeolite catalysts.  

PubMed

The removal of free fatty acid (FFA) in waste frying oil by esterification with methanol was conducted using various zeolite catalysts. The ZSM-5 (MFI), mordenite (MOR), faujasite (FAU), beta (BEA) zeolites, and silicalite were employed with different Si/Al molar ratio in the reaction. The effects of acidic properties and pore structure of the zeolite catalysts were discussed relating to the conversion of the FFA. The MFI zeolite induced an improvement of the removal efficiency of FFA by cracking to the FFA in its pore structure due to its narrow pore mouth. The catalytic activity for FFA removal was lowered with decreasing of acid strength of the zeolites. The strong acid sites of zeolites induced the high conversion of FFA comparatively. The acid strength and pore structure of acidic zeolites affected the catalytic activity in FFA removal. PMID:18387298

Chung, Kyong-Hwan; Chang, Duck-Rye; Park, Byung-Geon

2008-11-01

175

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

Microsoft Academic Search

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

Lan Z. Yu; Martha J. M. Wells

2007-01-01

176

Solid oxide fuel cells having porous cathodes infiltrated with oxygen-reducing catalysts  

DOEpatents

Solid-oxide fuel cells include an electrolyte and an anode electrically coupled to a first surface of the electrolyte. A cathode is provided, which is electrically coupled to a second surface of the electrolyte. The cathode includes a porous backbone having a porosity in a range from about 20% to about 70%. The porous backbone contains a mixed ionic-electronic conductor (MIEC) of a first material infiltrated with an oxygen-reducing catalyst of a second material different from the first material.

Liu, Meilin; Liu, Ze; Liu, Mingfei; Nie, Lifang; Mebane, David Spencer; Wilson, Lane Curtis; Surdoval, Wayne

2014-08-12

177

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

178

Alkylation of toluene with methanol over heteropoly acid\\/Y-zeolite catalysts  

Microsoft Academic Search

Alkylation of toluene with methanol has been studied in a fixed bed reactor with a continuous flow system. As a promoter,\\u000a heteropoly acids and their metal salts were impregnated on Y-zeolite. Catalyst impregnated with lower amount of heteropoly\\u000a acid showed higher initial activity, and the catalytic activity was enhanced by more electronegative metal ion of heteropoly\\u000a acid salt impregnated on

Chang Yeop Hwang; Jong Woon Kwak; Wha Young Lee; Ho-In Lee

1986-01-01

179

Influence of surface acidity in lactose oxidation over supported Pd catalysts  

Microsoft Academic Search

Lactose oxidation to lactobionic acid was investigated over palladium forms of Beta and MCM-22 zeolites. Different support acidity and the method of palladium introduction were applied. It was observed that the catalyst preparation methods, as well as acidity, influence the activity and selectivity. Pd-H-MCM-22 zeolites were more active, than palladium on conventional supports, for instance silica and alumina, or beta

Anton V. Tokarev; Elena V. Murzina; Prem K. Seelam; Narendra Kumar; Dmitry Yu. Murzin

2008-01-01

180

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

181

Model heterogeneous acid catalysts and metal-support interactions: A combined surface science and catalysis study  

SciTech Connect

This (<100 [Angstrom]) silica-alumina layers were tested as potential model heterogeneous acid catalysts for combined surface science and catalysis studies. Three preparation methods were used: oxidation of r3 [times] r3 R30 Al/Si(111) structure in UHV; deposition on Si(lll) from aqueous solution; and argon ion beam sputter deposition in UHV. The homogeneous thin layers are amorphous, and the chemical environment of surface atoms is similar to that of Si, Al and oxygen atoms on high surface area acid catalysts. Since the ion beam-deposited thin layer of silica-alumina has the same composition as the target zeolite this deposition method is a promising tool to prepare model catalysts using practical catalyst targets. The silica-alumina layers are active in cumene cracking, a typical acid catalyzed reaction. In order to clearly distinguish background reactions and the acid catalyzed reaction at least 20 cm[sup 2] catalyst surface area is needed. Two series of model platinum-alumina catalysts were prepared in a combined UHV -- high pressure reactor cell apparatus by depositing alumina on polycrystalline Pt foil and by vapor depositing Pt on a thin alumina layer on Au. Both model surfaces have been prepared with and without chlorine. AES, CO desorption as well as methyl cyclopentane (MCP) hydrogenolysis studies indicate that the Pt surface area is always higher if a chlorination step is involved. Selectivity patterns in MCP ring opening on Pt-on-alumina'' and on alumina-on-Pt'' are different; only the former is a linear combination of selective and statistical ring opening. Product distribution, however, changes with coverage and reaction time. The properties of the two model catalyst systems and role of chlorine in MCP hydrogenolysis are also discussed.

Boszormenyi, I.

1991-05-01

182

Model heterogeneous acid catalysts and metal-support interactions: A combined surface science and catalysis study  

SciTech Connect

This (<100 {Angstrom}) silica-alumina layers were tested as potential model heterogeneous acid catalysts for combined surface science and catalysis studies. Three preparation methods were used: oxidation of r3 {times} r3 R30 Al/Si(111) structure in UHV; deposition on Si(lll) from aqueous solution; and argon ion beam sputter deposition in UHV. The homogeneous thin layers are amorphous, and the chemical environment of surface atoms is similar to that of Si, Al and oxygen atoms on high surface area acid catalysts. Since the ion beam-deposited thin layer of silica-alumina has the same composition as the target zeolite this deposition method is a promising tool to prepare model catalysts using practical catalyst targets. The silica-alumina layers are active in cumene cracking, a typical acid catalyzed reaction. In order to clearly distinguish background reactions and the acid catalyzed reaction at least 20 cm{sup 2} catalyst surface area is needed. Two series of model platinum-alumina catalysts were prepared in a combined UHV -- high pressure reactor cell apparatus by depositing alumina on polycrystalline Pt foil and by vapor depositing Pt on a thin alumina layer on Au. Both model surfaces have been prepared with and without chlorine. AES, CO desorption as well as methyl cyclopentane (MCP) hydrogenolysis studies indicate that the Pt surface area is always higher if a chlorination step is involved. Selectivity patterns in MCP ring opening on ``Pt-on-alumina`` and on ``alumina-on-Pt`` are different; only the former is a linear combination of selective and statistical ring opening. Product distribution, however, changes with coverage and reaction time. The properties of the two model catalyst systems and role of chlorine in MCP hydrogenolysis are also discussed.

Boszormenyi, I.

1991-05-01

183

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

184

Degradation of oxalic acid from aqueous solutions by ozonation in presence of Ni\\/Al 2O 3 catalysts  

Microsoft Academic Search

The ozonation of oxalic acid has been carried out in an agitated slurry semi-batch reactor using NiO\\/Al2O3 as catalysts. The presence of catalysts in the ozonation processes significantly improves the oxalic acid removal rate, in comparison to the catalytic process. The influence of calcination temperature on the catalyst activity and on leaching of the active component was assessed. At the

Sorin Marius Avramescu; Corina Bradu; Ion Udrea; Nicoleta Mihalache; Florin Ruta

2008-01-01

185

Carbon nanotubes as electronic interconnects in solid acid fuel cell electrodes.  

PubMed

Carbon nanotubes have been explored as interconnects in solid acid fuel cells to improve the link between nanoscale Pt catalyst particles and macroscale current collectors. The nanotubes were grown by chemical vapor deposition on carbon paper substrates, using nickel nanoparticles as the catalyst, and were characterized using scanning electron microscopy and Raman spectroscopy. The composite electrode material, consisting of CsH2PO4, platinum nanoparticles, and platinum on carbon-black nanoparticles, was deposited onto the nanotube-overgrown carbon paper by electrospraying, forming a highly porous, fractal structure. AC impedance spectroscopy in a symmetric cell configuration revealed a significant reduction of the electrode impedance as compared to similarly prepared electrodes without carbon nanotubes. PMID:23942778

Varga, Áron; Pfohl, Moritz; Brunelli, Nicholas A; Schreier, Marcel; Giapis, Konstantinos P; Haile, Sossina M

2013-10-01

186

Acid- and base-functionalized core-confined bottlebrush copolymer catalysts for one-pot cascade reactions.  

PubMed

We demonstrate a novel method that enables the formation of core-confined bottlebrush copolymers (CCBCs) as catalyst supports. Significantly, owing to the site-isolated effect, these CCBC catalysts with the incompatible acidic para-toluenesulfonic acid (PTSA) and basic 4-(dimethylamino)pyridine (DMAP) groups can conduct a simple two-step sequential reaction in one vessel. PMID:25317577

Xiong, Linfeng; Zhang, Hui; Zhong, Aiqing; He, Zidong; Huang, Kun

2014-12-01

187

A new environmental friendly method for the preparation of sugar acids via catalytic oxidation on gold catalysts  

Microsoft Academic Search

A novel and efficient way of producing of aldonic acids is reported. The selective catalytic oxidation of monosaccharides (arabinose, ribose, xylose, lyxose, mannose, rhamnose, glucose, galactose, N-acetyl-glucosamine) and disaccharides (lactose, maltose, cellobiose, melibiose) on Au, Pd and Pt catalysts was investigated. By using the gold catalyst, a total selectivity with respect to aldonic acids and a high catalytic activity for

Agnes Mirescu; Ulf Prüße

2007-01-01

188

Selective poisoning and deactivation of acid sites on sulfated zirconia catalysts for n-butane isomerization  

SciTech Connect

Reaction kinetics measurements, selective poisoning, and microcalorimetry were used to study the activity, selectivity, and deactivation of acid sites on a sulfated zirconia catalyst for n-butane isomerization at 423 K. The sulfated zirconia catalyst has a distribution of acid site strengths, containing 50 {mu}mol/g of strong acid sites characterized by heats of ammonia adsorption from 125 to 165 kJ/mol. The strongest acid sites (heats from 145 to 165 kJ/mol) are responsible for the high initial activity of the catalyst, but these sites deactivate rapidly under reaction conditions. The acid sites exhibiting heats from 125 to 145 kJ/mol are less active than the stronger sites, but deactivate more slowly. Weaker sites have low activity and deactivate more rapidly after the intermediate sites are deactivated or poisoned. Broensted acidity is necessary for extended catalytic activity, although Lewis acid sites may play a role in generating the initial high activity. Acid sites with heats of ammonia adsorption from 125 to 165 kJ/mol show good selectivity for production of isobutane (ca. 93%), while sites with heats from 120 to 125 kJ/mol show lower isobutane selectivity (ca. 80%). 50 refs., 7 figs.

Yaluris, G.; Larson, R.B.; Kobe, J.M. [Univ. of Wisconsin, Madison, WI (United States)] [and others] [Univ. of Wisconsin, Madison, WI (United States); and others

1996-01-01

189

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

190

Synthesis of sulfonated porous carbon nanospheres solid acid by a facile chemical activation route  

NASA Astrophysics Data System (ADS)

Generally, porous carbon nanospheres materials are usually prepared via a template method, which is a multi-steps and high-cost strategy. Here, we reported a porous carbon nanosphere solid acid with high surface area and superior porosity, as well as uniform nanospheical morphology, which prepared by a facile chemical activation with ZnCl2 using resorcinol-formaldehyde (RF) resins spheres as precursor. The activation of RF resins spheres by ZnCl2 at 400 °C brought high surface area and large volume, and simultaneously retained numerous oxygen-containing and hydrogen-containing groups due to the relatively low processing temperature. The presence of these functional groups is favorable for the modification of -SO3H groups by a followed sulfonation treating with sulphuric acid and organic sulfonic acid. The results of N2 adsorption-desorption and electron microscopy clearly showed the preservation of porous structure and nanospherical morphology. Infrared spectra certified the variation of surface functional groups after activation and the successful modification of -SO3H groups after sulfonation. The acidities of catalysts were estimated by an indirect titration method and the modified amount of -SO3H groups were examined by energy dispersive spectra. The results suggested sulfonated porous carbon nanospheres catalysts possessed high acidities and -SO3H densities, which endowed their significantly catalytic activities for biodiesel production. Furthermore, their excellent stability and recycling property were also demonstrated by five consecutive cycles.

Chang, Binbin; Guo, Yanzhen; Yin, Hang; Zhang, Shouren; Yang, Baocheng

2015-01-01

191

Immobilizing Cr3+ with SO3H-functionalized solid polymeric ionic liquids as efficient and reusable catalysts for selective transformation of carbohydrates into 5-hydroxymethylfurfural.  

PubMed

A series of functional polymeric ionic liquids (FPILs) were prepared by coupling of SO3H-functionalized polymeric ionic liquids with different counterpart anions containing or excluding CrCl3·6H2O, and characterized by SEM, FT-IR, XRD, NH3-TPD, TG, melting point, ICP-AES, and TEM. The catalytic activity of the prepared solid FPILs was investigated for the conversion of biomass including fructose, glucose and cellulose into 5-hydroxymethylfurfural (HMF) with the presence of DMSO-mediated solvents, successively producing moderate to excellent yields of HMF under atmospheric pressure. The FPILs catalysts developed in this study present improved performance on fructose-to-HMF conversion over other solid catalysts, such as functional ionic liquids supported by silica, metal oxides and strong acid ion exchange resin catalysts, and can be very easily recycled at least five times without significant loss of activity. In addition, a kinetic analysis was carried out to illustrate the formation of HMF. PMID:23850822

Li, Hu; Zhang, Qiuyun; Liu, Xiaofang; Chang, Fei; Zhang, Yuping; Xue, Wei; Yang, Song

2013-09-01

192

Candida rugosa lipase as an enantioselective catalyst in the esterification of methyl branched carboxylic acids: resolution of rac-3,7-dimethyl-6-octenoic acid (citronellic acid)  

Microsoft Academic Search

Some chiral methyl branched alkanoic and alkenoic acids were used as substrates in esterifications with 1-hexadecanol in cyclohexane at water activity aw=0.8 catalysed by immobilised Candida rugosa lipase (CRL). Citronellic acid was one of several chiral 2- and 3-methyl branched acids that were successfully resolved by the catalyst. With 3-methyl-branched substrates the R-enantiomers reacted fastest, whereas with 2-methyl acids the

Ba-Vu Nguyen; Erik Hedenström

1999-01-01

193

Sulfonic acid functionalized mesoporous MCM-41 silica as a convenient catalyst for Bisphenol-A synthesis.  

PubMed

Sulfonic acid groups anchored to the surface of mesoporous MCM-41 silica have been identified with S K-edge XANES spectra and the material is an efficient catalyst for the liquid phase condensation of phenol with acetone to form Bisphenol-A with high selectivity. PMID:12240100

Das, D; Lee, J F; Cheng, S

2001-11-01

194

Brønsted Acidic Ionic Liquids: Fast, Mild, and Efficient Catalysts for Solvent?Free Tetrahydropyranylation of Alcohols  

Microsoft Academic Search

Brønsted acidic ionic liquids as efficient and reusable catalysts for the protection of alcohols as tetrahydropyranyl (THP) ethers under solvent?free conditions at room temperature was investigated. Good to excellent yields were obtained at a faster rate over [BMIm][HSO4] or [BMIm][H2PO4].

Zhiying Duan; Yanlong Gu; Youquan Deng

2005-01-01

195

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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-an...

196

Conversion of lower alcohols into C 2 –C 4 olefins over acid-base catalysts  

Microsoft Academic Search

The conversion reactions of methanol, ethanol, and their ethers in the presence of acid-base catalysts based on mesoporous\\u000a ZSM-5 and ZSM-11 zeolites, microporous SAPO zeolites, heteropoly acids, and perfluorinated sulfonated cation exchangers are\\u000a discussed. The set of reactions reflects the formation of olefins beginning from ethylene to butenes. The heats of reaction\\u000a were estimated from the calculated values of the

R. V. Ermakov; V. A. Plakhotnik

2008-01-01

197

When gold meets chiral Brønsted acid catalysts: extending the boundaries of enantioselective gold catalysis.  

PubMed

This review describes the development in the use of Au(I)/Brønsted acid binary catalytic systems to enable an enantioselective transformation in one-pot that cannot be achieved by gold catalysts alone. The examples discussed herein are promising since apart from using chiral ligands there exists a possibility of using chiral Brønsted acids. Clearly, the horizon for enantioselective gold catalysis has been expanded as more options to make the gold-catalyzed reactions enantioselective have become available. PMID:25177929

Inamdar, Suleman M; Konala, Ashok; Patil, Nitin T

2014-12-14

198

Synthesis of Nipagin Esters Using Acidic Functional Ionic Liquids as Catalysts  

Microsoft Academic Search

Several Brønsted acidic functional ionic liquids (FILs) with an alkane sulfonic acid group were synthesized. These FILs as dual solvent-catalysts for Nipagin esterification reactions were investigated. The results indicated that [HSO3-pMIM]HSO4 has the best catalytic activity and recyclability among the various kinds of FILs investigated, and its structure was characterized by infrared and NMR. The [HSO3-pMIM]HSO4 could be easily separated

Guohua Wang; Lu Li; Congxia Xie; Shitao Yu; Fusheng Liu; Xiaoling Ye

2011-01-01

199

Transfer Hydrogenation Reaction Of Ketones And Formic Acid Under Hydrothermal Conditions Without A Catalyst  

NASA Astrophysics Data System (ADS)

The hydrothermal experiments with ketones and formic acid showed that the hydrogen transfer reduction of ketones can be conducted with formic acid as a hydride donor in the presence of NaOH at 300° C. The yield of alcohols was considerably higher at a much lower ratio of hydrogen source to ketones than the traditional Meerwein-Ponndorf-Verley reduction, reaching 60% for isopropanol from acetone and 70% for lactic acid from pyruvic acid. Water molecules as a catalyst may directly participate in the transition state by making a hydrogen-bond ring network with the substrate molecules.

Shen, Zheng; Zhang, Yalei; Zhou, Xuefei; Wu, Bing; Cao, Jianglin; Jin, Fangming

2010-11-01

200

Sono-synthesis of biodiesel from soybean oil by KF/?-Al?O? as a nano-solid-base catalyst.  

PubMed

In this work, biodiesel has successfully prepared via ultrasonic method in a short time and low temperature by nano-solid-base catalyst (KF/?-Al?O?). The catalyst was obtained by calcination of a mixture of KF and ?-Al?O? m(KF)/m(?-Al?O?) at 500 °C for 3 h. Nano-solid-base catalyst was characterized with scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR), thermal gravimetry (TG) and the Hammett indicator methods. The TEM image depicted nanoparticles and uniform dispersion of active phase over alumina. The XRD analysis confirmed the formation of potassium aluminum fluoride (K?AlF?) and potassium oxide, active catalyst for transesterification. The transesterification of soybean oil with methanol was performed by using both low frequency ultrasonic reactor (20 kHz) and mechanical stirring in the presence of KF/?-Al?O?. The influence of various parameters such as ultrasonic power, oil/methanol molar ratio, catalyst concentration, time, and temperature were studied on the biodiesel formation. The maximum yield (95%) was achieved by applying 45 W acoustic power, molar ratio of alcohol to oil at 12:1, catalyst concentration of 2.0 wt%, 40 min sonication, and temperature of 50 °C. The transesterification was performed in 360 min using mechanical stirring with 76% yield. The results confirm that ultrasound significantly accelerates the transesterification reaction in comparison with the mechanical stirring. PMID:25445716

Shahraki, H; Entezari, M H; Goharshadi, E K

2015-03-01

201

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

202

Mechanochemical Approach for Selective Deactivation of External Surface Acidity of ZSM-5 Zeolite Catalyst.  

PubMed

The acid sites associated with the external surface of zeolite particles are responsible for undesirable consecutive reactions, such as isomerization, alkylation, and oligomerization, resulting in a lower selectivity to a target product; therefore, the selective modification (deactivation) of the external surface of zeolite particles has been an important issue in zeolite science. Here, a new method for surface deactivation of zeolite catalyst was tested via a mechanochemical approach using powder composer. Postsynthetic mechanochemical treatment of ZSM-5 zeolite causes a selective deactivation of catalytically active sites existing only on the external surface, as a potentially useful catalyst for highly selective production of p-xylene. PMID:25654542

Inagaki, Satoshi; Sato, Koki; Hayashi, Shunsuke; Tatami, Junichi; Kubota, Yoshihiro; Wakihara, Toru

2015-03-01

203

Efficient hydrolysis of cellulose over a novel sucralose-derived solid acid with cellulose-binding and catalytic sites.  

PubMed

A new sucralose-derived solid acid catalyst (SUCRA-SO3H), containing -Cl and -SO3H functional groups, has been shown to be highly effective for hydrolyzing ?-1,4-glucans, completely hydrolyzing cellobiose (1) into glucose (2) in 3 h and converting the microcrystalline cellulose pretreated by the ionic liquid into glucose (2) with a yield of around 55% and a selectivity of 98% within 24 h at a relatively moderate temperature (393K). The enhanced adsorption capacity that the catalyst has for glucan by virtue of the presence of chloride groups that act as cellulose-binding sites offers the possibility of resolving the existing bottleneck in heterogeneous catalysis to hydrolyze cellulose, namely, the low accessibility of cellulose to the reaction position in typical solid catalysts. The apparent activation energy for hydrolysis of cellobiose (1) with SUCRA-SO3H was 94 kJ/mol, which was much lower than that with sulfuric acid (133 kJ/mol) and the corresponding sucrose-derived catalyst (SUCRO-SO3H) without chlorine groups (114 kJ/mol). PMID:24512554

Hu, Shuanglan; Smith, Thomas John; Lou, Wenyong; Zong, Minhua

2014-02-26

204

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...

205

Tetraphosphine Linker Scaffolds with a Tetraphenyltin Core for Superior Immobilized Catalysts: A Solid-State NMR Study  

E-print Network

the mechanism of the phosphonium formation in more detail by utilizing solid-state NMR spectroscopy. It has also been a point of interest to study the linkers and catalysts under realistic conditions, in the presence of solvents. Therefore, HRMAS (high...

Perera, Melanie Ingrid

2012-10-19

206

SOLID-STATE SYNTHESIS OF HETEROCYCLIC HYDRAZONES USING MICROWAVES UNDER CATALYST-FREE CONDITIONS: JOURNAL ARTICLE (1605)  

EPA Science Inventory

NRMRL-CIN-1605 Jeselnik, M., Varma*, R.S., Polanc, S., and Kocevar, M. Solid-State Synthesis of Heterocyclic Hydrazones using Microwaves under Catalyst-free Conditions. Green Chemistry (White, J.D. (Ed.), Cambridge, United Kingdom: Royal Society of Chemistry) (4):35-38 (2002). ...

207

A solid-state NMR investigation of the structure of mesoporous silica nanoparticle supported rhodium catalysts  

SciTech Connect

A detailed study of the chemical structure of mesoporous silica catalysts containing rhodium ligands and nanoparticles (RhP-MSN) was carried out by multi-dimensional solid-state NMR techniques. The degree of functionalization of the rhodium-phosphinosilyl complex to the surface of the RhP-MSN channels was determined by {sup 29}Si NMR experiments. The structural assignments of the rhodium-phosphinosilyl complex were unambiguously determined by employing the novel, indirectly detected heteronuclear correlation ({sup 13}C-{sup 1}H and {sup 31}P-{sup 1}H idHETCOR) techniques, which indicated that oxidation of the attached phosphinosilyl groups and detachment of Rh was enhanced upon syngas conversion.

Rapp, Jennifer; Huang, Yulin; Natella, Michael; Cai, Yang; Lin, Victor S.-Y.; Pruski, Marek

2009-01-04

208

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

209

Acid strength of silica-supported oxide catalysts studied by microcalorimetric measurements of pyridine adsorption  

SciTech Connect

Microcalorimetric measurements of the differential heat of pyridine adsorption were used to probe the distribution of acid strength on a series of silica-supported oxide catalysts. Depositing oxides of the following cations onto silica increased the acid strength of the catalyst: Ga{sup 3{plus}}, Zn{sup 2{plus}}, Al{sup 3{plus}}, Fe{sup 3{plus}}, Fe{sup 2{plus}}, Mg{sup 2{plus}}, and Sc{sup 3{plus}}. The acid strength distribution curves for the supported oxide samples showed either two or three regions of constant heat of adsorption while silica had an energetically homogeneous surface. The Ga, Al, and Sc samples were found to have both Bronsted and Lewis acidity while the remaining samples showed only Lewis acidity. Incremental adsorption of pyridine indicated that the initial region of highest heat corresponds to strong Lewis acidity while intermediate heats seemed to be due to weaker Lewis acid sites or a combination of Lewis and Bronsted acid sites. The final region of lowest heat was due to H-bonded pyridine on silica. Estimates of the entropies of adsorption were determined, providing information about the mobility of the adsorbed pyridine molecules. The initial differential heat of adsorption increases proportionally to the Sanderson electronegativity of the added oxide.

Cardona-Martinez, N.; Dumesic, J.A. (Univ. of Wisconsin, Madison (USA))

1991-02-01

210

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

211

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

NASA Astrophysics Data System (ADS)

The feasibility of adapting phosphoric acid fuel cells to operate on coal gas fuels containing significant levels of contaminants such as CO, H2S and COS was investigated. The overall goal was the development of low-cost, carbon-supported anode fuel cell catalysts that can efficiently operate with a fossil fuel-derived hydrogen gas feed contaminated with carbon monoxide and other impurities. This development would reduce the cost of gas cleanup necessary in a coal gas-fueled PAFC power plant, thereby reducing the final power cost of the electricity produced. The problem to date was that the contaminant gases typically adsorb on catalytic sites and reduce the activity for hydrogen oxidation. An advanced approach investigated was to modify these alloy catalyst systems to operate efficiently on coal gas containing higher levels of contaminants by increasing the alloy catalyst impurity tolerance and ability to extract energy from the CO present through (1) generation of additional hydrogen by promoting the CO/H2 water shift reaction or (2) direct oxidation of CO to CO2 with the same result. For operation on anode gases containing high levels of CO, a Pt-Ti-Zn and Pt-Ti-Ni anode catalyst showed better performance over a Pt baseline or G87A-17-2 catalyst. The ultimate aim was to allow PAFC-based power plants to operate on coal gas fuels containing increased contaminant concentrations, thereby decreasing the need for and cost of rigorous coal gas cleanup procedures.

Kackley, N. D.; McCatty, S. A.; Kosek, J. A.

1990-07-01

212

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

213

Tandem isomerization-decarboxylation of unsaturated fatty acids to olefins via ruthenium metal-as-ligand catalysts  

Technology Transfer Automated Retrieval System (TEKTRAN)

A new facile Ru-catalyzed route to bio-olefins3 from unsaturated fatty acids via readily accessible metal-as-ligand type catalyst precursors, [Ru(CO)2RCO2]n and Ru3(CO)12, will be described. The catalyst apparently functions in a tandem mode by dynamically isomerizing the positions of double bonds i...

214

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

215

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

216

Geminal Brønsted 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

217

Effects of catalyst pore structure and Acid properties on the dehydration of glycerol.  

PubMed

Hierarchical porous catalysts have recently attracted increasing interest because of the enhanced accessibility to active sites on such materials. In this context, previously reported hierarchically mesoporous ASN and ASPN materials are evaluated by applying them to the dehydration of glycerol, and demonstrate excellent catalytic performance. In addition, a comprehensive understanding of the effects of pore structures and the acid properties on the reaction through comparative studies with microporous HZSM-5 and mesoporous AlMCM-41 is provided. PMID:25418679

Choi, Youngbo; Park, Hongseok; Yun, Yang Sik; Yi, Jongheop

2015-03-01

218

Salt-induced peptide formation from amino acids in the presence of clays and related catalysts  

Microsoft Academic Search

The salt-induced peptide formation (SIPF) reaction, starting from the amino acids glycine and\\/or alanine has been performed as wetting\\/drying cycles in the presence of the clay minerals montmorillonite and hectorite and the related catalysts alumina and silica, in order to see whether SIPF and clay-catalysed peptide synthesis reactions could have occurred simultaneously under primitive earth conditions. The results show that

Hoang Le Son; Yuttana Suwannachot; Juraj Bujdak; Bernd M. Rode

1998-01-01

219

Low equivalent weight short-side-chain perfluorosulfonic acid ionomers in fuel cell cathode catalyst layers  

Microsoft Academic Search

The morphology and fuel cell performance of cathode catalyst layers (CCLs) using low equivalent weight (EW) short-side-chain (SSC) perfluorosulfonic acid ionomers have been investigated in this work. The results were compared with those for a baseline CCL containing 30wt% of the conventional ionomer 1100 EW Nafion®. The CCLs fabricated with 10–20wt% of the Aquivion™ ionomer displayed a similar morphology to

Chao Lei; Dmitri Bessarabov; Siyu Ye; Zhong Xie; Steven Holdcroft; Titichai Navessin

2011-01-01

220

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

221

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

222

The glmS Ribozyme Cofactor is a General Acid-Base Catalyst  

PubMed Central

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, Julia; Fedor, Martha J.

2012-01-01

223

Pt/TiO2 (Rutile) Catalysts for Sulfuric Acid Decomposition in Sulfur-Based Thermochemical Water-Splitting Cycles  

SciTech Connect

Thermochemical cycles consist of a series of chemical reactions to produce hydrogen from water at lower temperatures than by direct thermal decomposition. All the sulfur-based cycles for water splitting employ the sulfuric acid decomposition reaction. This work reports the studies performed on platinum supported on titania (rutile) catalysts to investigate the causes of catalyst deactivation under sulfuric acid decomposition reaction conditions. Samples of 1 wt% Pt/TiO2 (rutile) catalysts were submitted to flowing concentrated sulfuric acid at 1123 K and atmospheric pressure for different times on stream (TOS) between 0 and 548 h. Post-operation analyses of the spent catalyst samples showed that Pt oxidation and sintering occurred under reaction conditions and some Pt was lost by volatilization. Pt loss rate was higher at initial times but total loss appeared to be independent of the gaseous environment. Catalyst activity showed an initial decrease that lasted for about 66 h, followed by a slight recovery of activity between 66 and 102 h TOS, and a period of slower deactivation after 102 h TOS. Catalyst sulfation did not seem to be detrimental to catalyst activity and the activity profile suggested that a complex dynamical situation involving platinum sintering, volatilization, and oxidation, along with TiO2 morphological changes affected catalyst activity in a non-monotonic way.

L. M. Petkovic; D. M. Ginosar; H. W. Rollins; K. C. Burch; P. J. Pinhero; H. H. Farrell

2008-04-01

224

Conversion of isoamyl alcohol over acid catalysts: Reaction dependence on nature of active centers  

SciTech Connect

Acid catalysts are known to catalyze the dehydration of alcohols. In addition some oxide catalysts with basic properties have also been shown to play an important role in such dehydration reactions. The dehydration of aliphatic alcohols to olefins has been studied in detail using alumina silica-alumina and zeolite catalysts. The olefin products further undergo isomerization in presence of acidic sites. The reaction of isoamyl alcohol on catalytic surfaces has not been investigated in greater detail. The dehydration of isoamyl alcohol is of considerable interest in fine chemicals. Isoamyl alcohol may also undergo dehydrogenation as observed in the case of n-butanol. The scope of the present work is to identify the nature of the active sites selective for dehydration and dehydrogenation of isoamyl alcohol and to modify the active sites to promote isomerization of dehydrated products. Four catalytic surfaces on which the acidic strength can be varied, as well as selectively suppressed, are chosen for this study. 17 refs., 1 fig., 3 tabs.

Babu, G.P.; Murthy, R.S.; Krishnan, V. [Hindustan Lever Research Centre, Bombay (India)] [Hindustan Lever Research Centre, Bombay (India)

1997-02-01

225

Hydroxyapatite supported caesium carbonate as a new recyclable solid base catalyst for the Knoevenagel condensation in water  

PubMed Central

Summary The Knoevenagel condensation between aromatic aldehydes and malononitrile, ethyl cyanoacetate or malonic acid with hydroxyapatite supported caesium carbonate in water is described. HAP–Cs2CO3 was found to be a highly active, stable and recyclable catalyst under the reaction conditions. PMID:20300501

Gupta, Monika; Anand, Medha

2009-01-01

226

Insights into the Interplay of Lewis and Brnsted Acid Catalysts in Glucose and Fructose Conversion to 5(Hydroxymethyl)furfural and  

E-print Network

Insights into the Interplay of Lewis and Brønsted Acid Catalysts in Glucose and Fructose Conversion is an active Lewis acid catalyst in glucose isomerization to fructose, and the combined Lewis and Brønsted acid]2+ . In contrast, Lewis acidity increases the overall rate of consumption of fructose and HMF

Frenkel, Anatoly

227

Nanoscale organization of thiol and arylsulfonic acid on silica leads to a highly active and selective bifunctional, heterogeneous catalyst.  

PubMed

Ordered mesoporous silicas functionalized with alkylsulfonic acid and thiol group pairs have been shown to catalyze the synthesis of bisphenols from the condensation of phenol and various ketones, with activity and selectivity highly dependent on the distance between the acid and thiol. Here, a new route to thiol/sulfonic acid paired catalysts is reported. A bis-silane precursor molecule containing both a disulfide and a sulfonate ester bond is grafted onto the surface of ordered mesoporous silica, SBA-15, followed by simultaneous disulfide reduction and sulfonate ester hydrolysis. The resulting catalyst, containing organized pairs of arylsulfonic acid and thiol groups, is significantly more active than the alkylsulfonic acid/thiol paired catalyst in the synthesis of bisphenol A and Z, and this increase in activity does not lead to a loss of regioselectivity. The paired catalyst has activity similar to that of a randomly bifunctionalized arylsulfonic acid/thiol catalyst in the bisphenol A reaction but exhibits greater activity and selectivity than the randomly bifunctionalized catalyst in the bisphenol Z reaction. PMID:18788738

Margelefsky, Eric L; Bendjériou, Anissa; Zeidan, Ryan K; Dufaud, Véronique; Davis, Mark E

2008-10-01

228

Isotope composition of carbon in amino acids of solid bitumens  

NASA Astrophysics Data System (ADS)

Primary data are presented on the isotope composition of carbon in individual amino acids from solid bitumens and several biological objects. The amino acids of biological objects are characterized by wide variations of the isotope composition of carbon. This fact occurs owing to the difference in biochemical paths of metabolism resulting in the synthesis of individual amino acids. The ?13C values are somewhat decreased for individual amino acids in asphaltenes, varying from -7.7 to -31.7‰. The carbon of amino acids is weighted in kerits from Bad'el' compared to asphaltenes. All the natural bitumens retain the characteristic trend for natural substances: the isotopically heavy and light amino acids by carbon are glycine and leucine, respectively. The isotope composition of amino-acid carbon is lightened compared to natural bitumens in the samples formed under a pronounced thermal impact (asphalt-like crust and kirishite).

Shanina, S. N.; Bushnev, D. A.

2014-06-01

229

Acid-Base Mechanism for Ruthenium-Based Water Oxidation Catalysts  

SciTech Connect

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 suggest a purely single-center mechanism. We find low activation energies (<5 kcal/mol) for each rearrangement in the catalytic cycle. In the crucial step of O-O bond formation, a solvent water acts as a Lewis base and attacks a highly oxidized Ru{sup V} = O. Armed with the structures and energetics of the single-center catalyst, we proceed to consider a representative Ru-dimer which was designed to form O{sub 2} via coupling between the two centers. We discover a mechanism that proceeds in analogous fashion to the monomer case, with all the most significant steps occurring at a single catalytic center within the dimer. This acid-base mechanism suggests a new set of strategies for the rational design of multicenter catalysts: rather than coordinating the relative orientations of the subunits, one can focus on coordinating solvation-shell water molecules or tuning redox potentials.

Wang, L.P.; Wu, Q.; Van Voorhis, T.

2010-05-17

230

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

231

Surface acidity and basicity of oxide catalysts: From aqueous suspensions to in situ measurements  

Microsoft Academic Search

The catalytic activity of many oxides in various petrochemical and petroleum-refining processes, such as isomerization, alkylation, cracking, aromatization, and many others [1], is due to their Lewis and Brønsted acidities [2]. The research concerning the acid?base properties of inorganic solid surfaces is extensive and has resulted in the modeling of the chemistry of acid?base catalysis and the appearance of new

T. S. Glazneva; N. S. Kotsarenko; E. A. Paukshtis

2008-01-01

232

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

SciTech Connect

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., E-mail: asbhatti@comsats.edu.pk [Center for Micro and Nano Devices (CMND), Department of Physics, COMSATS Institute of Information Technology, Islamabad 44000 (Pakistan)

2014-01-14

233

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

234

Niobium Complexes As Lewis Acid and Radical Catalysts  

SciTech Connect

The reaction of lithium pentaphenylcyclopentadiende (Li C{sub 5}Ph{sub 5}) with niobium pentachloride in dichloromethane or toluene produces insoluble red-orange solids whose C/H/Cl analyses are not consistent with C{sub 5}Ph{sub 5}NbCl{sub 4}. Addition of an acetonitrile solution of LiC{sub 5}Ph{sub 5} with NbCl{sub 5} gives C{sub 5}Ph{sub 5}NbCl{sub 4} observed as a transient product by NMR spectroscopy, which then abstracts H from the acetonitrile solvent to give HC{sub 5}Ph{sub 5} and presumably NbCl{sub 4}CH{sub 2}CN. Reversal of the order of addition gives the {center_dot}C{sub 5}Ph{sub 5} radical as characterized by MS and EPR spectroscopy. Attempts to prepare the trimethylsilyl derivative Me{sub 3}SiC{sub 5}Ph{sub 5} (a less reducing cyclopentadienyl group) were unsuccessful. Reaction was observed only in tetrahydrofuran, producing only Me{sub 3}SiO(CH{sub 2}){sub 4}C{sub 5}Ph{sub 4}(m-C{sub 6}H{sub 4}(CH3)) characterized by {sup 1}H, {sup 13}C NMR and mass spectroscopy. The trimethylsilyltetraphenylcyclopentadienyl derivative, Me{sub 3}Si(H)C{sub 5}Ph{sub 4}, was characterized by {sup 1}H, {sup 13}C NMR and mass spectroscopy. This compound reacts with NbCl{sub 5} to give HCl and ClSiMe{sub 3} and a mixture of HC{sub 5}Ph{sub 4}NbCl{sub 4} and Me{sub 3}SiC{sub 5}Ph{sub 4}NbCl{sub 4}.

Wayne Tikkanen

2005-10-01

235

Nano scale magnetically recoverable supported heteropoly acid as an efficient catalyst for the synthesis of benzimidazole derivatives in water.  

PubMed

12-Tungstophosphoric acid supported on silica-coated magnetic nano particles was prepared and characterized by transmission electron microscopy, scanning electron microscopy, powder X-ray diffraction and inductively coupled plasma atomic emission spectroscopy. Acidity of the catalysts was measured by potentiometric titration with n-butylamine. Catalytic activity of the prepared sample was evaluated in the model synthesis of 1,2-disubstituted benzimidazole derivatives in water. The catalyst showed excellent catalytic activity and the corresponding products were obtained in good to excellent yields under mild reaction conditions. Furthermore, the catalyst could be easily recovered using an external magnet and reused several times. The leaching and surface acidity of the recovered catalyst were also investigated. PMID:24664342

Rafiee, Ezzat; Rahpeima, Nasibeh; Eavani, Sara

2014-01-01

236

SBA-15-functionalized sulfonic acid confined acidic ionic liquid: a powerful and water-tolerant catalyst for solvent-free esterifications.  

PubMed

Incorporating a hydrophobic Brønsted acid ionic liquid (HBAIL) inside the nanospaces of SBA-15-Pr-SO(3)H led to a hydrophobic super Brønsted acid catalyst, which showed excellent catalytic performance in direct esterification of alcohols and carboxylic acids at ambient temperature under solvent-free conditions. PMID:22361844

Karimi, Babak; Vafaeezadeh, Majid

2012-04-01

237

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

238

Efficient production of hydrogen from formic acid using a Covalent Triazine Framework supported molecular catalyst.  

PubMed

A heterogeneous molecular catalyst based on Ir(III) Cp* (Cp*=pentamethylcyclopentadienyl) attached to a covalent triazine framework (CTF) is reported. It catalyses the production of hydrogen from formic acid with initial turnover frequencies (TOFs) up to 27?000?h(-1) and turnover numbers (TONs) of more than one million in continuous operation. The CTF support, with a Brunauer-Emmett-Teller (BET) surface area of 1800?m(2) ?g(-1) , was constructed from an optimal 2:1 ratio of biphenyl and pyridine carbonitrile building blocks. Biphenyl building blocks induce mesoporosity and, therefore, facilitate diffusion of reactants and products whereas free pyridinic sites activate formic acid towards ?-hydride elimination at the metal, rendering unprecedented rates in hydrogen production. The catalyst is air stable, produces CO-free hydrogen, and is fully recyclable. Hydrogen production rates of more than 60?mol?L(-1) ?h(-1) were obtained at high catalyst loadings of 16?wt?% Ir, making it attractive towards process intensification. PMID:25677344

Bavykina, A V; Goesten, M G; Kapteijn, F; Makkee, M; Gascon, J

2015-03-01

239

Acid-base properties, deactivation, and in situ regeneration of condensation catalysts for synthesis of methyl methacrylate  

SciTech Connect

Condensation reaction of a propionate with formaldehyde is a novel route for synthesis of methyl methacrylate (MMA). The reaction mechanism involves a proton abstraction from the propionate on the basic sites and activation of the aliphatic aldehyde on the acidic sites of the catalyst. The acid-base properties of ternary V-Si-P oxide catalysts and their relation to the NWA yield in the vapor phase condensation of formaldehyde with propionic anhydride has been studied for the first time. Five different V-Si-P catalysts with different atomic ratios of vanadium, silicon, and phosphorous were synthesized, characterized, and tested in a fixed-bed microreactor system. A V-Si-P 1:10:2.8 catalyst gave the maximum condensation yield of 56% based on HCHO fed at 300{degrees}C and 2 atm and at a space velocity of 290 cc/g cat{center_dot}h. A parameter called the ``q-ratio`` has been defined to correlate the condensation yields to the acid-base properties. The correlation of q-ratio with the condensation yield shows that higher q-ratios are more desirable. The long-term deactivation studies on the V-Si-P 1: 10:2.8 catalyst at 300{degrees}C and 2 atm and at a space velocity of 290 cc/g cat{center_dot}h show that the catalyst activity drops by a factor of nearly 20 over a 180 h period. The activity can be restored to about 78% of the initial activity by a mild oxidative regeneration at 300{degrees}C and 2 atm. The performance of V-Si-P catalyst has been compared to a Ta/SiO{sub 2} catalyst. The Ta- catalyst is more stable and has a higher on-stream catalyst life.

Gogate, M.R.; Spivey, J.J. [Reseach Triangle Institute, Research Triangle Institute, Research Triangle Park, NC (United States); Zoeller, J.R. [Eastman Chemical Co., Kingsport, TN (United States)

1996-12-31

240

Propane conversion over a Ru\\/CGO catalyst and its application in intermediate temperature solid oxide fuel cells  

Microsoft Academic Search

A Ru\\/CGO catalyst was investigated in combination with a Cu current collector for the direct electro-oxidation and internal\\u000a reforming of propane in a solid oxide fuel cell. The electrochemical power densities for the direct oxidation were larger\\u000a than in the internal reforming process at 750 ?C. The electrochemical performance in the presence of propane was significantly\\u000a affected by the polarization resistance

M. Lo Faro; D. La Rosa; G. Monforte; V. Antonucci; A. S. Arico; P. Antonucci

2007-01-01

241

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

242

Anodic acyloxylation based on the acid–base reactions between acetic acid or trifluoroacetic acid and solid-supported bases  

Microsoft Academic Search

We have developed a novel electrolytic system for anodic acyloxylation based on the acid–base reactions between acetic acid or trifluoroacetic acid and solid-supported bases. On the basis of the electrolytic system, anodic acyloxylation of organic compounds, which even have considerably high oxidation potentials, was successfully carried out to provide the corresponding acyloxylated products in moderate to excellent yields. Furthermore, it

Toshiki Tajima; Yuichiro Kishi; Atsushi Nakajima

2009-01-01

243

Solid-state acid-base reactions of indomethacin and flufenamic acid  

Microsoft Academic Search

The purpose of this study is to understand the mechanism of solid-state acid-base reactions and identify controlling factors for this type of reaction. The reactions between indomethacin and sodium bicarbonate, indomethacin and sodium carbonate, and flufenamic acid and magnesium oxide were investigated using X-ray powder diffraction, Fourier transform infrared spectroscopy, thermogravimetry, and solid-state nuclear magnetic resonance spectrometry. Quantitative methods based

Xiaoming Chen

2000-01-01

244

Gas diffusion electrode setup for catalyst testing in concentrated phosphoric acid at elevated temperatures.  

PubMed

We present a detailed description of the construction and testing of an electrochemical cell setup allowing the investigation of a gas diffusion electrode containing carbon supported high surface area catalysts. The setup is designed for measurements in concentrated phosphoric acid at elevated temperature, i.e., very close to the actual conditions in high temperature proton exchange membrane fuel cells (HT-PEMFCs). The cell consists of a stainless steel flow field and a PEEK plastic cell body comprising the electrochemical cell, which exhibits a three electrode configuration. The cell body and flow field are braced using a KF-25 vacuum flange clamp, which allows an easy assembly of the setup. As demonstrated, the setup can be used to investigate temperature dependent electrochemical processes on high surface area type electrocatalysts, but it also enables quick screening tests of HT-PEMFC catalysts under realistic conditions. PMID:25725862

Wiberg, Gustav K H; Fleige, Michael; Arenz, Matthias

2015-02-01

245

Gas diffusion electrode setup for catalyst testing in concentrated phosphoric acid at elevated temperatures  

NASA Astrophysics Data System (ADS)

We present a detailed description of the construction and testing of an electrochemical cell setup allowing the investigation of a gas diffusion electrode containing carbon supported high surface area catalysts. The setup is designed for measurements in concentrated phosphoric acid at elevated temperature, i.e., very close to the actual conditions in high temperature proton exchange membrane fuel cells (HT-PEMFCs). The cell consists of a stainless steel flow field and a PEEK plastic cell body comprising the electrochemical cell, which exhibits a three electrode configuration. The cell body and flow field are braced using a KF-25 vacuum flange clamp, which allows an easy assembly of the setup. As demonstrated, the setup can be used to investigate temperature dependent electrochemical processes on high surface area type electrocatalysts, but it also enables quick screening tests of HT-PEMFC catalysts under realistic conditions.

Wiberg, Gustav K. H.; Fleige, Michael; Arenz, Matthias

2015-02-01

246

High-temperature sulfuric acid decomposition over complex metal oxide catalysts  

SciTech Connect

Activity and stability of FeTiO3, MnTiO3, NiFe2O4, CuFe2O4, NiCr2O4, 2CuO•Cr2O3, CuO and Fe2O3 for the atmospheric decomposition of concentrated sulfuric acid in sulfur-based thermochemical water splitting cycles are presented. Catalyst activity was determined at temperatures from 725 to 900 °C. Catalytic stability was examined at 850 °C for up to one week of continuous operation. The results were compared to a 1.0 wt% Pt/TiO2 catalyst. Surface area by nitrogen physisorption, X-ray diffraction analyses, and temperature programmed desorption and oxidation were used to characterize fresh and spent catalyst samples. Over the temperature range, the catalyst activity of the complex oxides followed the general trend: 2CuO•Cr2O3 > CuFe2O4 > NiCr2O4 ˜ NiFe2O4 > MnTiO3 ˜ FeTiO3. At temperatures less than 800 °C, the 1.0 wt% Pt/TiO2 catalyst had higher activity than the complex oxides, but at temperatures above 850 °C, the 2CuO•Cr2O3 and CuFe2O4 samples had the highest activity. Surface area was found to decrease for all of the metal oxides after exposure to reaction conditions. In addition, the two complex metal oxides that contained chromium were not stable in the reaction environment; both leached chromium into the acid stream and decomposed into their individual oxides. The FeTiO3 sample also produced a discoloration of the reactor due to minor leaching and converted to Fe2TiO5. Fe2O3, MnTiO3 and NiFe2O4 were relatively stable in the reaction environment. In addition, CuFe2O4 catalyst appeared promising due to its high activity and lack of any leaching issues.

Daniel M. Ginosar; Harry W. Rollins; Lucia M. Petkovic; Kyle C. Burch; Michael J. Rush

2009-05-01

247

Manganese as a substitute for rhenium in CO2 reduction catalysts: the importance of acids.  

PubMed

Electrocatalytic properties, X-ray crystallographic studies, and infrared spectroelectrochemistry (IR-SEC) of Mn(bpy-tBu)(CO)3Br and [Mn(bpy-tBu)(CO)3(MeCN)](OTf) are reported. Addition of Brönsted acids to CO2-saturated solutions of these Mn complexes and subsequent reduction of the complexes lead to the stable and efficient production of CO from CO2. Unlike the analogous Re catalysts, these Mn catalysts require the addition of Brönsted acids for catalytic turnover. Current densities up to 30 mA/cm(2) were observed during bulk electrolysis using 5 mM Mn(bpy-tBu)(CO)3Br, 1 M 2,2,2-trifluoroethanol, and a glassy carbon working electrode. During bulk electrolysis at -2.2 V vs SCE, a TOF of 340 s(-1) was calculated for Mn(bpy-tBu)(CO)3Br with 1.4 M trifluoroethanol, corresponding to a Faradaic efficiency of 100 ± 15% for the formation of CO from CO2, with no observable production of H2. When compared to the analogous Re catalysts, the Mn catalysts operate at a lower overpotential and exhibit similar catalytic activities. X-ray crystallography of the reduced species, [Mn(bpy-tBu)(CO)3](-), shows a five-coordinate Mn center, similar to its rhenium analogue. Three distinct species were observed in the IR-SEC of Mn(bpy-tBu)(CO)3Br. These were of the parent Mn(bpy-tBu)(CO)3Br complex, the dimer [Mn(bpy-tBu)(CO)3]2, and the [Mn(bpy-tBu)(CO)3](-) anion. PMID:23418912

Smieja, Jonathan M; Sampson, Matthew D; Grice, Kyle A; Benson, Eric E; Froehlich, Jesse D; Kubiak, Clifford P

2013-03-01

248

Mesoporous Li\\/ZrO 2 as a solid base catalyst for biodiesel production from transesterification of soybean oil with methanol  

Microsoft Academic Search

Mesoporous 0.1M\\/ZrO2 (M = Li, Na, K, Mg, Ca) solid base catalysts were successfully synthesized by using a sol–gel method. The catalytic activities of the catalysts were tested via transesterification reactions of soybean oil with methanol. Both 0.1Mg\\/ZrO2 and 0.1Ca\\/ZrO2 catalysts showed no catalytic activity in this reaction, while Li, K modified ZrO2 catalysts achieved high yield of biodiesel production.

Yuqi Ding; Hui Sun; Jinzhao Duan; Ping Chen; Hui Lou; Xiaoming Zheng

2011-01-01

249

Kinetics of isobutane selective oxidation over Mo-V-P-As-Cs-Cu-O heteropoly acid catalyst  

Microsoft Academic Search

Isobutane oxidation was investigated in wide ranges of experimental conditions over Mo-V-P-As-Cs-Cu-O heteropoly acid catalyst. The kinetics could be described by an empirical set of first order equations. Methacrylic acid is produced by a series of consecutive reactions via isobutylene and methacrolein. Neither methacrolein nor methacrylic acid is formed directly from isobutane. Both overoxidation of methacrylic acid and total oxidation

Götz-Peter Schindler; Toshiaki Ui; Koichi Nagai

2001-01-01

250

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

251

One-Pot synthesis of phosphorylated mesoporous carbon heterogeneous catalysts with tailored surface acidity  

SciTech Connect

Soft-templated phosphorylated mesoporous carbons with homogeneous distributions of phosphate groups were prepared by a 'one-pot' synthesis method using mixtures of phosphoric acid with hydrochloric, or nitric acids in the presence of Pluronic F127 triblock copolymer. Adjusting the various ratios of phosphoric acid used in these mixtures resulted in carbons with distinct adsorption, structural and surface acidity properties. The pore size distributions (PSDs) from nitrogen adsorption at -196 C showed that mesoporous carbons exhibit specific surface areas as high as 551 m{sup 2}/g and mesopores as large as 13 nm. Both structural ordering of the mesopores and the final phosphate contents were strongly dependent on the ratios of H{sub 3}PO{sub 4} in the synthesis gels, as shown by transmission electron microscopy (TEM), X-ray photoelectron (XPS) and energy dispersive X-ray spectroscopy (EDS). The number of surface acid sites determined from temperature programmed desorption of ammonia (NH{sub 3}-TPD) were in the range of 0.3-1.5 mmol/g while the active surface areas are estimated to comprise 5-54% of the total surface areas. Finally, the conversion temperatures for the isopropanol dehydration were lowered by as much as 100 C by transitioning from the least acidic to the most acidic catalysts surface.

Fulvio, Pasquale F [ORNL; Mahurin, Shannon Mark [ORNL; Mayes, Richard T [ORNL; Bauer, Christopher [ORNL; Wang, Xiqing [ORNL; Veith, Gabriel M [ORNL; Dai, Sheng [ORNL

2012-01-01

252

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

253

Mercury oxidation by hydrochloric acid over TiO 2 supported metal oxide catalysts in coal combustion flue gas  

Microsoft Academic Search

Mercury oxidation by hydrochloric acid over the metal oxides supported by anatase type TiO2 catalysts, 1 wt.% MOx\\/TiO2 where M = V, Cr, Mn, Fe, Ni, Cu, and Mo, was investigated by the Hg0 oxidation and the NO reduction measurements both in the presence and absence of NH3. The catalysts were characterized by BET surface area measurement and Raman spectroscopy. The

Hiroyuki Kamata; Shun-ichiro Ueno; Naoki Sato; Toshiyuki Naito

2009-01-01

254

Degradation of Acid Blue 74 using Fe-ZSM5 zeolite as a heterogeneous photo-Fenton catalyst  

Microsoft Academic Search

Decolourisation and mineralization of an indigoid dye, C.I. Acid Blue 74, was conducted using Fe-ZSM5 zeolite as a catalyst in the presence of UV-C light and H2O2. The effects of different parameters such as amounts of catalyst, initial concentration of the dye and H2O2 and initial pH of the dye solution on the degradation efficiency of the process were assessed.

M. B. Kasiri; H. Aleboyeh; A. Aleboyeh

2008-01-01

255

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

256

Direct Synthesis of Phenol from Benzene on an Activated Carbon Catalyst Treated with Nitric Acid  

NASA Astrophysics Data System (ADS)

Commercially available coal-based activated carbon was treated by nitric acid with different concentrations and the resultant samples were used as catalysts for the direct hydroxylation of benzene to phenol in acetonitrile. Boehm titration, X-ray photoelectron spectroscopy, scanning electron microscope coupled with an energy dispersive X-ray microanalyzer, and Brunauer-Emmett-Teller method were used to characterize the samples. The number of carboxyl groups on the surface was found to be the main factor affecting the catalytic activity. An optimum catalytic performance with a yield of 15.7% and a selectivity of 87.2% to phenol was obtained.

Chen, Cui-hong; Xu, Jia-quan; Jin, Ming-ming; Li, Gui-ying; Hu, Chang-wei

2011-06-01

257

High-temperature sulfuric acid decomposition over complex metal oxide catalysts  

Microsoft Academic Search

Activity and stability of FeTiO3, MnTiO3, NiFe2O4, CuFe2O4, NiCr2O4, 2CuO·Cr2O3, CuO and Fe2O3 for the atmospheric decomposition of concentrated sulfuric acid in sulfur-based thermochemical water splitting cycles are presented. Catalyst activity was determined at temperatures from 725 to 900°C. Catalytic stability was examined at 850°C for up to 1 week of continuous operation. The results were compared to a 1.0wt%

Daniel M. Ginosar; Harry W. Rollins; Lucia M. Petkovic; Kyle C. Burch; Michael J. Rush

2009-01-01

258

Solid phase sequencing of double-stranded nucleic acids  

DOEpatents

This invention relates to methods for detecting and sequencing of target double-stranded nucleic acid sequences, to nucleic acid probes and arrays of probes useful in these methods, and to kits and systems which contain these probes. Useful methods involve hybridizing the nucleic acids or nucleic acids which represent complementary or homologous sequences of the target to an array of nucleic acid probes. These probe comprise a single-stranded portion, an optional double-stranded portion and a variable sequence within the single-stranded portion. The molecular weights of the hybridized nucleic acids of the set can be determined by mass spectroscopy, and the sequence of the target determined from the molecular weights of the fragments. Nucleic acids whose sequences can be determined include nucleic acids in biological samples such as patient biopsies and environmental samples. Probes may be fixed to a solid support such as a hybridization chip to facilitate automated determination of molecular weights and identification of the target sequence.

Fu, Dong-Jing (Waltham, MA); Cantor, Charles R. (Boston, MA); Koster, Hubert (Concord, MA); Smith, Cassandra L. (Boston, MA)

2002-01-01

259

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

260

Friedel-Crafts acylation reactions using heterogeneous catalysts stimulated by conventional and microwave heating  

Microsoft Academic Search

The acylation of anisole with decanoic acid over a range of solid-acid catalysts has been studied under conventional heating and microwave stimulation. The microwave-irradiated experiments exhibited increased reaction rates, the extent of which was dependent upon the nature of the catalyst. The origin of this microwave enhancement has been attributed to the selective desorption of water from the surface of

G. Bond; J. A. Gardner; R. W. McCabe; D. J. Shorrock

2007-01-01

261

Gallium-containing polymer brush film as efficient supported Lewis acid catalyst in a glass microreactor  

PubMed Central

Summary Polystyrene sulfonate polymer brushes, grown on the interior of the microchannels in a microreactor, have been used for the anchoring of gallium as a Lewis acid catalyst. Initially, gallium-containing polymer brushes were grown on a flat silicon oxide surface and were characterized by FTIR, ellipsometry, and X-ray photoelectron spectroscopy (XPS). XPS revealed the presence of one gallium per 2–3 styrene sulfonate groups of the polymer brushes. The catalytic activity of the Lewis acid-functionalized brushes in a microreactor was demonstrated for the dehydration of oximes, using cinnamaldehyde oxime as a model substrate, and for the formation of oxazoles by ring closure of ortho-hydroxy oximes. The catalytic activity of the microreactor could be maintained by periodic reactivation by treatment with GaCl3. PMID:24062830

Munirathinam, Rajesh; Ricciardi, Roberto; Egberink, Richard J M; Huskens, Jurriaan; Holtkamp, Michael; Wormeester, Herbert; Karst, Uwe

2013-01-01

262

Generating hydrogen-rich fuel-cell feeds from dimethyl ether (DME) using Cu\\/Zn supported on various solid-acid substrates  

Microsoft Academic Search

Several incipient wetness prepared catalysts containing copper and zinc were prepared in-house and reactor tested for the production of hydrogen from dimethyl ether steam reforming (DME-SR). The incorporation of copper and zinc onto a solid acid substrate (viz., zeolites ZSM-5 and Y with Si\\/Al=2.5–140, ?-Al2O3, and ZrO2) combined the catalytic components for DME hydrolysis to methanol (MeOH) and methanol steam

Troy A. Semelsberger; Kevin C. Ott; Rodney L. Borup; Howard L. Greene

2006-01-01

263

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

264

Metal-Organic Framework Based upon the Synergy of a Brønsted Acid Framework and Lewis Acid Centers as a Highly Efficient Heterogeneous Catalyst for Fixed-Bed Reactions.  

PubMed

We report a strategy of combining a Brønsted acid metal-organic framework (MOF) with Lewis acid centers to afford a Lewis acid@Brønsted acid MOF with high catalytic activity, as exemplified in the context of MIL-101-Cr-SO3H·Al(III). Because of the synergy between the Brønsted acid framework and the Al(III) Lewis acid centers, MIL-101-Cr-SO3H·Al(III) demonstrates excellent catalytic performance in a series of fixed-bed reactions, outperforming two benchmark zeolite catalysts (H-Beta and HMOR). Our work therefore not only provides a new approach to achieve high catalytic activity in MOFs but also paves a way to develop MOFs as a new type of highly efficient heterogeneous catalysts for fixed-bed reactions. PMID:25773275

Li, Baiyan; Leng, Kunyue; Zhang, Yiming; Dynes, James J; Wang, Jian; Hu, Yongfeng; Ma, Dingxuan; Shi, Zhan; Zhu, Liangkui; Zhang, Daliang; Sun, Yinyong; Chrzanowski, Matthew; Ma, Shengqian

2015-04-01

265

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

266

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

267

Amino acid derived CuII compounds as catalysts for asymmetric oxidative coupling of 2-naphthol.  

PubMed

We report the synthesis and characterization of several novel aminopyridine - L-amino acid derived Cu(II)-complexes. The ligands are prepared by a one-pot reductive alkylation of the L-amino acid scaffold and the respective aminopyridine Cu(II)-complexes were obtained by reaction with CuCl2 or Cu(acetato)2. All compounds were characterized by spectroscopic techniques, as well as ESI-MS. Two of the Cu(II)-complexes were characterized by single-crystal X-ray diffraction, one of them, [Cu(II)(L)(CH3COO)] (HL = (S)-3-phenyl-2-(pyridin-2-ylmethylamino)propanoic acid), being the first ever reported aminopyridine-class Cu(II) complex bearing a tridentate N,N,O donor set and a monodentate acetato ligand. The complexes are tested as catalysts in the oxidative coupling of 2-naphthol in organic solvent-water mixtures using dioxygen as the terminal oxidant. The effect of variables such as ligand denticity and substituents, as well as solvent, temperature and oxidant intake, on the overall performance is studied. In general, moderate to low conversions of 2-naphthol to 1,1'-bi-2-naphthol (BINOL) are obtained. The catalysts also showed moderate to low enantioselectivity. Some aspects of the reaction mechanism were elucidated by spectroscopy, electrochemical and theoretical studies. It was found that basic additives are important for activity, but these also increase the formation of secondary oxidation products. The addition of peroxide scavengers such as KI resulted in an increase of conversion, the yield of BINOL and enantioselectivity. PMID:25434677

Adão, Pedro; Barroso, Sónia; Carvalho, M Fernanda N N; Teixeira, Carlos M; Kuznetsov, Maxim L; Pessoa, João Costa

2015-01-28

268

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

269

Effect of oxygen mobility in solid catalyst on transient regimes of catalytic reaction of methane partial oxidation at short contact times  

Microsoft Academic Search

Mathematical modeling of the effect of the oxygen mobility in a solid oxide catalyst on the dynamics of transients of fast\\u000a catalytic reactions has been carried out. The analysis was based upon the redox mechanistic scheme with a due regard for diffusion\\u000a of oxygen from the bulk of catalyst to its surface. Parameters of kinetic and mathematical models were selected

S. I. Reshetnikov; A. I. Lukashevich; G. M. Alikina; V. A. Sadykov

2006-01-01

270

Fluidized catalyst process for production and hydration of olefins  

SciTech Connect

A continuous multi-stage process is described for increasing octane quality and yield of liquid hydrocarbons from an integrated fluidized catalytic cracking unit and hydration reaction zone comprising: contacting heavy hydrocarbon feedstock in a primary fluidized bed reaction stage with cracking catalyst comprising particulate solid large pore acid aluminosilicate zeolite catalyst at conversion conditions to produce a hydrocarbon effluent comprising gas containing C2-C6 olefins, intermediate hydrocarbons in the gasoline and distillate range, and cracked bottoms; regenerating primary stage zeolite cracking catalyst in a primary stage regeneration zone and returning at least a portion of regenerated zeolite cracking catalyst to the primary reaction stage; reacting an olefinic stream containing at least one iso-olefin with water in a secondary fluidized bed hydration reactor stage in contact with a closed fluidized bed of acid zeolite catalyst particles comprising solid acid zeolite under hydration reaction conditions to effectively convert said isoolefin to alkyl alkanol; adding fresh acid zeolite particles to the secondary stage reactor in an amount sufficient to maintain average equilibrium catalyst particle activity for effective alkanol synthesis reaction without regeneration of the secondary catalyst bed; withdrawing a portion of equilibrium catalyst from the secondary fluidized bed reactor stage; and passing said withdrawn catalyst portion to the primary fluidized bed reaction stage for contact with the petroleum feedstock.

Harandi, M.N.

1993-08-03

271

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

272

Sulfonic Acid-functionalized gold nanoparticles: a colloid-bound catalyst for soft lithographic application on self-assembled monolayers.  

PubMed

In this report, we present a new lithographic approach to prepare patterned surfaces. Self-assembled monolayers (SAMs) of the acid-labile trimethylsilyl ether (TMS-OC(11)H(22)S)(2) (TMS adsorbate) was formed on gold. 5-Mercapto-2-benzimidazole sulfonic acid sodium salt (MBS-Na(+)) was used as a ligand for gold nanoparticles. These monolayer-protected gold colloids (MPCs) were transformed into the catalytically active H(+)-form by ion exchange. This colloid-bound catalyst hydrolyzed the TMS adsorbate (TMS-OC(11)H(22)S)(2) both in solution and when self-assembled on gold surfaces. Microcontact printing of the active colloid-bound catalyst on the preformed TMS SAM led to the deposition of the colloid onto the SAMs. After the catalyst nanoparticles were rinsed off, a patterned surface was created as shown by AFM. PMID:12670250

Li, Xue-Mei; Paraschiv, Vasile; Huskens, Jurriaan; Reinhoudt, David N

2003-04-01

273

Acid Activated Indian Bentonite, an Efficient Catalyst for Esterification of Carboxylic Acids  

Microsoft Academic Search

The preparation, characterization, and catalytic properties of acid activated Indian bentonite (AAIB) are reported. AAIB has\\u000a been characterized by XRD (basal spacing, 15.05 Å), specific surface area (273 m2\\/g), pore volume and pore diameter using BET method, TGA, SEM, and surface acidity by n-butylamine back titration method and infrared spectroscopy using pyridine as a probe molecule. The activity of Montmorillonite\\u000a K10, ZrO2,

B. Vijayakumar; Gopalpur Nagendrappa; B. S. Jai Prakash

2009-01-01

274

The synergic effect between Mo species and acid sites in Mo/HMCM-22 catalysts for methane aromatization.  

PubMed

The acid properties of Mo/HMCM-22 catalyst, which is the precursor form of the working catalyst for methane aromatization reaction, and the synergic effect between Mo species and acid sites were studied and characterized by various characterization techniques. It is concluded that Brønsted and Lewis acidities of HMCM-22 are modified due to the introduction of molybdenum. We suggest a monomer of Mo species is formed by the exchange of Mo species with the Brønsted acid sites. On the other hand, coordinate unsaturated sites (CUS) are suggested to be responsible for the formation of newly detected Lewis acid sites. Computer modelling is established and coupling with experimental results, it is then speculated that the effective activation of methane is properly accomplished on Mo species accommodated in the 12 MR supercages of MCM-22 zeolite whereas the Brønsted acid sites in the same channel system play a key role for the formation of benzene. A much more pronounced volcano-typed reactivity curve of the Mo/HMCM-22 catalysts, as compared with that of the Mo/HZSM-5, with respect to Mo loading is found and this can be well understood due to the unique channel structure of MCM-22 zeolite and synergic effect between Mo species and acid sites. PMID:16186916

Ma, Ding; Zhu, Qingjun; Wu, Zili; Zhou, Danhong; Shu, Yuying; Xin, Qin; Xu, Yide; Bao, Xinhe

2005-08-21

275

Neopentane and solid acids: direct hydron exchange before cracking.  

PubMed

The hydrogen/deuterium exchange reaction of 2,2-dimethylpropane (neopentane) over D(2)O-exchanged zeolites (MOR, FAU, BEA, MFI) using a batch recirculation reactor was studied by means of gas chromatography coupled with mass spectrometer. In the temperature range 473-573 K, H/D exchange proceeds without side reaction such as cracking at short contact times. Indeed the C-H bond has appeared favorably involved in the activation of neopentane compared to the less accessible C-C bond. The transition state allowing hydron exchange is most likely a carbonium species (pentacoordinated carbon) as in the case of the H/D exchange between methane and solid acid. The activation energies of the H/D exchange between neopentane and zeolites are the same for all zeolites indicating a common carbonium ion type transition state. On the basis of previous results in the case of the exchange between methane and liquid superacids, the deuterium exchange rates in neopentane were tentatively related to the acidity of the solids. However the order of activity MOR > MFI > BEA > FAU seems to be related to the size of the pores, which may suggest the involvement of a confinement effect in the zeolites cavities. Moreover we found that H/D exchange takes also place between neopentane and deuterated sulfated zirconia (SZ) emphasizing its strong acidity. PMID:16970460

Walspurger, Stéphane; Sun, Yinyong; Souna Sido, Abdelkarim Sani; Sommer, Jean

2006-09-21

276

Synthesis of fructone over dealmuinated USY supported heteropoly acid and its salt catalysts  

Microsoft Academic Search

12-Phosphotungstic acid (PW) and cesium salt of PW supported on dealuminated ultra-stable Y zeolite (DUSY) with various loadings were prepared by impregnation method, and their physicochemical properties were characterized by X-ray powder diffraction (XRD), N2 adsorption, solid state 31P and 29Si MAS NMR, Hammett indicator and SEM techniques. Their catalytic performances were evaluated in the liquid-phase acetalization of ethyl acetoacetate

Fumin Zhang; Chaoshu Yuan; Jun Wang; Yan Kong; Haiyang Zhu; Chunyan Wang

2006-01-01

277

Synthesis of porous and acidic complex metal oxide catalyst based on group 5 and 6 elements  

Microsoft Academic Search

Complex metal oxides of transition metals using Mo, W, V, Nb and Ta were synthesized by hydrothermal method. The synthesized complex metal oxides were characterized and the solid acid catalytic activity was tested through the Friedel-Crafts alkylation of anisole and benzyl alcohol. X-ray diffraction patterns of the obtained samples showed two peaks at 2?=22° and 46° indicating these materials have

Toru Murayama; Nozomi Kuramata; Shunsuke Takatama; Kosuke Nakatani; Shoko Izumi; Xiaodong Yi; Wataru Ueda

278

The effect of the distance between acidic site and basic site immobilized on mesoporous solid on the activity in catalyzing aldol condensation  

NASA Astrophysics Data System (ADS)

Acid-base bifunctional heterogeneous catalysts containing carboxylic and amine groups, which were immobilized at defined distance from one another on the mesoporous solid were synthesized by immobilizing lysine onto carboxyl-SBA-15. The obtained materials were characterized by X-ray diffraction (XRD), N 2 adsorption, Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron micrographs (SEM), transmission electron micrographs (TEM), elemental analysis, and back titration. Proximal-C-A-SBA-15 with a proximal acid-base distance was more active than maximum-C-A-SBA-15 with a maximum acid-base distance in aldol condensation reaction between acetone and various aldehydes. It appears that the distance between acidic site and basic site immobilized on mesoporous solid should be an essential factor for catalysis optimization.

Yu, Xiaofang; Yu, Xiaobo; Wu, Shujie; Liu, Bo; Liu, Heng; Guan, Jingqi; Kan, Qiubin

2011-02-01

279

Synthesis and characterization of porous layered solid acids  

NASA Astrophysics Data System (ADS)

Four types of zirconium phosphonates with interesting texture have been synthesized and characterized, including zirconium biphenylenebis(phosphonates), zirconium terphenylenebis(phosphonates), zirconium phosphate biphenylenebis-(phosphonates) and zirconium phenylphosphonates. These compounds have been characterized by thermogravimetric analysis, X-ray powder diffraction (XRD), surface area analysis, elemental analysis, 31P solid state NMR, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). When HF and 100% excess Zr were used in the synthesis, the resulting zirconium biphenylenebis-(phosphonates) (Zr-P2-Ph2) compounds have microporosity (10--20 A) and high surface areas (˜400 m2/g). The micropore diameters range from 13 to 18 A, depending on the solvents and the amount of HF used. Zirconium 4,4?-terphenylenebis(phosphonates) (Zr-P2-Ph3) also have mostly microporous properties (11--17 A) if 100% excess Zr was used. SEM and TEM studies revealed that these samples have a stacked layer pattern, instead of a "house of cards" arrangement. A novel model is therefore proposed to explain the porosity and surface area data of these compounds. A number of porous sulfonated zirconium phosphonates, namely, sulfonated zirconium phenylphosphonate, sulfonated zirconium biphenylenebis(phosphonate) and sulfonated zirconium terphenylenebis(phosphonate), have been successfully synthesized. The use of SO3 as the sulfonation agent instead of fuming H2SO4 virtually eliminates the possibility of water contact with the sulfonated samples. The surface acidity of these materials has been characterized in great detail by solid state MAS NMR studies of probe molecules. The results suggest that the acidity of several sulfonated samples is close to 100% H2SO4. The syntheses of structurally stable Al-pillared montmorillonites (Al-mont), Zr-pillared montmorillonites (Zr-mont), phosphated Al-mont, phosphated Zr-mont, sulfated Al-mont and sulfated Zr-mont have been successfully achieved. XRD and surface area analysis (SA) have been used mainly for structural characterization. The modified clays exhibit good thermal stability and surface area values of ˜300 m2/g, and some samples retain their d-spacings after modification if prepared carefully. The acidity strength of the modified pillared samples has been investigated by solid state MAS NMR spectroscopy with acetone-2-13C adsorption. The phosphated Al-pillared montmorillonites have slightly weaker acidity after modification, but the phosphated Zr-pillared montmorillonites have much stronger acidity. Some of the acid sites in one sample even exhibit superacidity.

Wang, Zhike

280

New catalysts based on the heteropoly acid-zeolite system for the synthesis of higher ?-olefins by paraffin cracking  

Microsoft Academic Search

Natural zeolites (clinoptilolite) from the Shankanay deposit in Almaty oblast were used to prepare catalysts for the synthesis\\u000a of higher ?-olefins by paraffin cracking. The modification of zeolite with inorganic and organic heteropoly acids resulted\\u000a in an enhancement of catalytic activity. The olefin yield on the zeolite modified with heteropoly acids was as high as 36.6%\\u000a after one run in

S. R. Konuspayev; K. A. Kadirbekov; R. K. Nurbayeva; A. T. Sarsekova

2011-01-01

281

The Structure and Density of Mo and Acid Sites in Mo-ExchangedH-ZSMZ Catalysts  

SciTech Connect

Mo/H-ZSM5 (1.0-6.3 wt percent Mo; Mo/Al = 0.11-0.68) catalysts for CH4 aromatization were prepared from physical mixtures of MoO3 and H-ZSM5 (Si/Al= 14.3). X-ray diffraction and elemental analysis of physical mixtures treated in air indicate that MoOx species migrate onto the external ZSM5 surface at about 623 K. Between 773 and 973 K, MoOx species migrate inside zeolite channels via surface and gas phase transport, exchange at acid sites, and react to form H2O. The amount of H2O evolved during exchange and the amount of residual OH groups detected by isotopic equilibration with D2 showed that each Mo atom replaces one H+ during exchange. This stoichiometry and the requirement for charge compensation suggest that exchanged species consist of (Mo2O5)2+ditetrahedral structures interacting with two cation exchange sites. The proposed mechanism may provide a general framework to describe the exchange of multivalent cations onto Al sites in zeolites. As the Mo concentration exceeds that required to form a MoOx monolayer on the external zeolite surface ({approx}4 wt percent Mo for the H-ZSM5 used), Mo species sublime as (MoO3)n oligomers or extract Al from the zeolite framework to form inactive Al2(MoO4)3 domains detectable by 27Al NMR. These (Mo2O5)2+ species reduce to form the active MoCx species during the initial stages of CH4 conversion reactions. Optimum CH4 aromatization rates were obtained on catalysts with intermediate Mo contents ({approx}0.4Mo/Al), because both MoCx and acid sites are required to activate CH4 and to convert the initial C2H4 products into C6+ aromatics favored by thermodynamics.

Borry III, Richard W.; Kim, Young Ho; Huffsmith, Anne; Reimer,Jeffrey A.; Iglesia, Enrique

1999-03-01

282

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

283

In Situ High Temperature Surface Enhanced Raman Spectroscopy for the Study of Interface Phenomena: Probing a Solid Acid on Alumina  

SciTech Connect

Herein, we utilize surface enhanced Raman spectroscopy (SERS) for the in situ analyses of catalyst structure while operating at elevated temperatures in various atmospheres. In order to accomplish this, robust SERS substrates were generated by depositing an ultrathin protective coating of alumina on top of silver nanowires (NWs) via atomic layer deposition (ALD). In situ studies were then conducted by analyzing the effects of heating a solid acid, phosphotungstic acid (PTA), on the alumina surface in either an oxygen or hydrogen environment at temperatures up to 400 C. Interestingly, the distance-dependent decay of the enhancement factor of the SERS signal from the underlying NWs allowed us to probe with great detail the interfacial region between the PTA and the alumina surface. The ability to analyze the area closest to the alumina surface was further confirmed by assembling vanadia onto the substrate and monitoring the intensity differences between the V-O-Al and outer V = O bonds.

Dai, Sheng [ORNL; Formo, Eric V [ORNL; Mahurin, Shannon Mark [ORNL; Wu, Zili [ORNL

2011-01-01

284

Cyclisation of Citronellal to Isopulegol Catalysed by Hydrous Zirconia and Other Solid Acids  

Microsoft Academic Search

The cyclisation of citronellal to isopulegol is an important step in the synthesis of menthol. Several zirconia-based catalysts were evaluated for this reaction. Zirconium hydroxides and phosphated zirconia had very good activity and selectivity. Ammonia TPD and pyridine IR studies indicate the presence of strong Lewis together with weak Brønsted acid sites. Other strong acids like sulfated zirconia, Amberlyst, and

G. K Chuah; S. H Liu; S Jaenicke; L. J Harrison

2001-01-01

285

Electrocatalytic Performances of Carbon Supported Metallophthalocyanine and Pt\\/Metallophthalocyanine Catalysts Towards Dioxygen Reduction in Acidic Medium  

Microsoft Academic Search

Electrocatalytic performances of phthalocyanines (Pcs) involving N-benzyl-4-phenyloxyacetamide moieties, dispersed on a high-surface area carbon substrate, Vulcan XC-72 (VC) and Nafion (Nf),\\u000a towards oxygen reduction in acidic medium were determined and compared. The VC\\/Nf\\/CoPc(5) catalyst showed much higher catalytic activity than those of the other Pc(1–4)-based catalysts (H2Pc 1, ZnPc 2, NiPc 3 and CuPc 4) and that of unsubstituted CoPc-based

?. Koç; M. Çamur; M. Bulut; A. R. Özkaya

2009-01-01

286

Molecular water-oxidation catalyst derived from ruthenium diaqua bis(2,2'-bipyridyl-5,5'-dicarboxylic acid)  

Microsoft Academic Search

Controlled-potential electrolysis of cis-Ru\\/sup II\\/Lâ(OHâ)â\\/sup 2 +\\/ (where L is 2,2'-bipyridyl-5,5'-dicarboxylic acid) in 0.5 M HâSOâ solutions leads to the formation of a relatively durable and active molecular water-oxidation catalyst. Detailed analyses by UV-visible absorption spectrophotometry, resonance Raman spectrophotometry, electrochemical measurements, HPLC, and elemental analysis indicate that the water-oxidation catalyst is an oxo-bridged dimer, Lâ(HâO)Ru-O-Ru(OHâ)Lâ. The synthesis, spectrophotometric, and redox

Francois P. Rotzinger; Shekhar Munavalli; Pascal Comte; James K. Hurst; M. Gratzel; Fu Jann Pern; Arthur J. Frank

1987-01-01

287

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

288

Low-grade oils and fats: effect of several impurities on biodiesel production over sulfonic acid heterogeneous catalysts.  

PubMed

Different lipidic wastes and low-grade oils and fats have been characterized and evaluated as feedstocks for the acid-catalyzed production of FAME. The characterization of these materials has revealed significant contents of free fatty acids, Na, K, Ca, Mg, P, unsaponifiable matter and humidity. Arenesulfonic acid-functionalized SBA-15 silica catalyst has provided yields to FAME close to 80% in the simultaneous esterification-transesterification of the different feedstocks, regardless of their nature and properties, using methanol under the following reaction conditions: 160 °C, 2 h, methanol to oil molar ratio of 30, 8 wt.% catalyst loading, and 2000 rpm stirring rate. Nevertheless, reutilization of the catalyst is compromised by high levels of impurities, especially because of deactivation by strong interaction of unsaponifiable matter with the catalytic sites. The conditioning of these materials by aqueous washing in the presence of cationic-exchange resin Amberlyst-15, followed by a drying step, resulted in a lower deactivation of the catalyst. PMID:21862322

Morales, Gabriel; Bautista, L Fernando; Melero, Juan A; Iglesias, Jose; Sánchez-Vázquez, Rebeca

2011-10-01

289

Far infrared spectra of solid state aliphatic amino acids in different protonation states  

E-print Network

Far infrared spectra of solid state aliphatic amino acids in different protonation states Aurélien of zwitterionic, cationic, and anionic forms of aliphatic amino acids in solid state have been studied for all aliphatic amino acids due to the lack of structural data. This work is intended to provide

Paris-Sud XI, Université de

290

Solid-state phase transitions of DL-aminobutyric acid.  

PubMed

Four polymorphs are known for the amino acid racemate DL-aminobutyric acid: one tetragonal form B and three monoclinic forms A, C, and D for which two solid-solid phase transitions take place between 209 and 337 K. The intermediate form A, in space group P2(1)/c, is known to display disorder in the crystalline state with the ethyl side chain occupying three different conformations. The high temperature form D and the low temperature form C have been assumed to display a similar type of disorder in the space group C2/c. The present investigation, on the basis of high quality crystal structures at 100 K (C form), 220 K (A form), 295 K (A form), and 295 K (D form), provides updated results for all three forms and in particular demonstrates that the A ? C and A ? D transitions in fact involve only a partial space group conversion, so that two monoclinic phases are simultaneously present at high and low temperatures. To the best of our knowledge, such a phenomenon has not been observed previously for an organic molecule. The nonroutine refinement of the crystallographic data was performed with a specially adapted version of the program JANA2006. The observed polymorphs are compared with those found for DL-norvaline, DL-norleucine, and DL-methionine. PMID:22867532

Görbitz, Carl Henrik; Alebachew, Fassil; Pet?í?ek, Václav

2012-09-01

291

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

292

A General, Simple Catalyst for Enantiospecific Cross Couplings of Benzylic Ammonium Triflates and Boronic Acids: No Phosphine Ligand Required.  

PubMed

Highly improved conditions for the enantiospecific cross coupling of benzylic ammonium triflates with boronic acids are reported. This method relies on the use of Ni(cod)2 without ancillary phosphine or N-heterocyclic carbene ligands as catalyst. These conditions enable the coupling of new classes of boronic acids and benzylic ammonium triflates. In particular, both heteroaromatic and vinyl boronic acids are well tolerated as coupling partners. In addition, these conditions enable the use of ammonium triflates with a variety of substituents at the benzylic stereocenter. Further, naphthyl-substitution is not required on the benzylic ammonium triflate; ammonium triflates with simple aromatic substituents also undergo this coupling. Good to high yields and levels of stereochemical fidelity are observed. This new catalyst system greatly expands the utility of enantiospecific cross couplings of these amine-derived substrates for the preparation of highly enantioenriched products. PMID:25364060

Shacklady-McAtee, Danielle M; Roberts, Kelsey M; Basch, Corey H; Song, Ye-Geun; Watson, Mary P

2014-07-01

293

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

294

In situ infrared monitoring of the solid/liquid catalyst interface during the three-phase hydrogenation of nitrobenzene over nanosized Au on TiO2.  

PubMed

The three-phase hydrogenation of nitrobenzene catalysed by nanosized gold over titania was investigated in a slurry. Simultaneous in situ ATR-FTIR monitoring of the liquid phase and at the solid/liquid catalyst interface identified the species adsorbed on the catalyst and those in the liquid phase during the reaction. Nitrosobenzene was not detected analytically while the spectroscopic measurements strongly indicated phenylhydroxylamine as an intermediate reacting before desorbing from the catalyst surface. Under the same reaction conditions, azobenzene and hydrazobenzene were identified as intermediates during the hydrogenation of azoxybenzene to aniline. When nitrosobenzene or phenylhydroxylamine was alternately fed as reactant, azoxybenzene was produced via a disproportionation route. With the former, azoxybenzene was not further reduced by hydrogen because nitrosobenzene deactivated the catalyst. Combined with H(2) uptake, the spectroscopic measurements provided new insights into the reaction mechanism of the gold catalysed hydrogenation of nitrobenzene and an update of the corresponding kinetics. PMID:21660327

Richner, Gilles; van Bokhoven, Jeroen A; Neuhold, Yorck-Michael; Makosch, Martin; Hungerbühler, Konrad

2011-07-21

295

Acidic Ionic Liquids as Sustainable Approach of Cellulose and Lignocellulosic Biomass Conversion without Additional Catalysts.  

PubMed

The use of ionic liquids (ILs) for biomass processing has attracted considerable attention recently as it provides distinct features for pre-treated biomass and fractionated materials in comparison to conventional processes. Process intensification through integration of dissolution, fractionation, hydrolysis and/or conversion in one pot should be accomplished to maximise economic and technological feasibility. The possibility of using alternative ILs capable not only of dissolving and deconstructing selectively biomass but also of catalysing reactions simultaneously are a potential solution of this problem. In this Review a critical overview of the state of the art and perspectives of the hydrolysis and conversion of cellulose and lignocellulosic biomass using acidic ILs using no additional catalyst are provided. The efficiency of the process is mainly considered with regard to the hydrolysis and conversion yields obtained and the selectivity of each reaction. The process conditions can be easily tuned to obtain sugars and/or platform chemicals, such as furans and organic acids. On the other hand, product recovery from the IL and its purity are the main challenges for the acceptance of this technology as a feasible alternative to conventional processes. PMID:25703380

da Costa Lopes, André M; Bogel-?ukasik, Rafa?

2015-03-01

296

Ultrasonic enhance acid hydrolysis selectivity of cellulose with HCl-FeCl3 as catalyst.  

PubMed

The effect of ultrasonic pretreatment coupled with HCl-FeCl3 catalyst was evaluated to hydrolyze cellulose amorphous regions. The ultrasonic pretreatment leads to cavitation that affects the morphology and microstructure of fibers, enhancing the accessibility of chemical reagent to the loosened amorphous regions of cellulose. In this work, Fourier transform infrared spectroscopy (FTIR) was used to identify characteristic absorption bands of the constituents and the crystallinity was evaluated by the X-ray diffraction (XRD) technique. The results indicated that appropriate ultrasonic pretreatment assisted with FeCl3 can enhance the acid hydrolysis of amorphous regions of cellulose, thus improving the crystallinity of the remaining hydrocellulose. It was observed that sonication samples that were pretreated for 300 W and 20 min followed by acid hydrolysis had maximum of 78.9% crystallinity. The crystallinity was 9.2% higher than samples that were not subjected to ultrasound. In addition, the average fines length decreased from 49 ?m to 37 ?m. PMID:25498717

Li, Jinbao; Zhang, Xiangrong; Zhang, Meiyun; Xiu, Huijuan; He, Hang

2015-03-01

297

Heterogenization of Homogeneous Catalysts: the Effect of the Support  

SciTech Connect

We have studied the influence of placing a soluble, homogeneous catalyst onto a solid support. We determined that such a 'heterogenized' homogeneous catalyst can have improved activity and selectivity for the asymmetric hydrogenation of enamides to amino acid derivatives. The route of heterogenization of RhDuPhos(COD){sup +} cations occurs via electrostatic interactions with anions that are capable of strong hydrogen bonding to silica surfaces. This is a novel approach to supported catalysis. Supported RhDuPhos(COD){sup +} is a recyclable, non-leaching catalyst in non-polar media. This is one of the few heterogenized catalysts that exhibits improved catalytic performance as compared to its homogeneous analog.

Earl, W.L.; Ott, K.C.; Hall, K.A.; de Rege, F.M.; Morita, D.K.; Tumas, W.; Brown, G.H.; Broene, R.D.

1999-06-29

298

Selective catalytic reduction of NOx with NH3 over a Cu-SSZ-13 catalyst prepared by a solid state ion exchange method  

SciTech Connect

A novel solid state method was developed to synthesize Cu-SSZ-13 catalysts with excellent NH3-SCR performance and durable hydrothermal stability. After the solid state ion exchange (SSIE) process, the SSZ framework structure and surface area was maintained. In-situ DRIFTS and NH3-TPD experiments provide evidence that isolated Cu ions were successfully exchanged into the pores, which are the active centers for the NH3-SCR reaction.

Wang, Di; Gao, Feng; Peden, Charles HF; Li, Junhui; Kamasamudram, Krishna; Epling, William S.

2014-10-28

299

MIL-101-SO3H: 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-SO3H, 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

300

An efficient and heterogeneous recyclable silicotungstic acid with modified acid sites as a catalyst for conversion of fructose and sucrose into 5-hydroxymethylfurfural in superheated water.  

PubMed

Acidity modified silver exchanged silicotungstic acid (AgSTA) catalyst was prepared and characterized by X-ray diffraction, FT-IR spectroscopy, Raman spectroscopy, FT-IR pyridine adsorption, SEM imaging, EDX mapping, and antimicrobial activity was also tested. The catalytic activity was evaluated for the dehydration of fructose and sucrose in superheated water. As a result, 98% conversion of fructose with 85.7% HMF yield and 87.4% HMF selectivity in 120 min reaction time at 120 °C reaction temperature using 10 wt.% of AgSTA catalyst was achieved. While, 92% sucrose conversion with 62.5% of HMF yield was obtained from sucrose at uniform condition in 160 min. The effect of reaction parameters, such as reaction temperature, time, catalyst dosage, and effect acidity on HMF yield was also investigated. The AgSTA catalyst was separated from the reaction mixture by filtration process at end of the reaction and reused eight times without loss of catalytic activity. PMID:23435221

Jadhav, Arvind H; Kim, Hern; Hwang, In Taek

2013-03-01

301

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

302

Catalytic Synthesis of Oxygenates: Mechanisms, Catalysts and Controlling Characteristics  

SciTech Connect

This research focused on catalytic synthesis of unsymmetrical ethers as a part of a larger program involving oxygenated products in general, including alcohols, ethers, esters, carboxylic acids and their derivatives that link together environmentally compliant fuels, monomers, and high-value chemicals. The catalysts studied here were solid acids possessing strong Br�������¸nsted acid functionalities. The design of these catalysts involved anchoring the acid groups onto inorganic oxides, e.g. surface-grafted acid groups on zirconia, and a new class of mesoporous solid acids, i.e. propylsulfonic acid-derivatized SBA-15. The former catalysts consisted of a high surface concentration of sulfate groups on stable zirconia catalysts. The latter catalyst consists of high surface area, large pore propylsulfonic acid-derivatized silicas, specifically SBA-15. In both cases, the catalyst design and synthesis yielded high concentrations of acid sites in close proximity to one another. These materials have been well-characterization in terms of physical and chemical properties, as well as in regard to surface and bulk characteristics. Both types of catalysts were shown to exhibit high catalytic performance with respect to both activity and selectivity for the bifunctional coupling of alcohols to form ethers, which proceeds via an efficient SN2 reaction mechanism on the proximal acid sites. This commonality of the dual-site SN2 reaction mechanism over acid catalysts provides for maximum reaction rates and control of selectivity by reaction conditions, i.e. pressure, temperature, and reactant concentrations. This research provides the scientific groundwork for synthesis of ethers for energy applications. The synthesized environmentally acceptable ethers, in part derived from natural gas via alcohol intermediates, exhibit high cetane properties, e.g. methylisobutylether with cetane No. of 53 and dimethylether with cetane No. of 55-60, or high octane properties, e.g. diisopropylether with blending octane No. of 105, and can replace aromatics in liquid fuels.

Kamil Klier; Richard G. Herman

2005-11-30

303

Continuous Isosorbide Production From Sorbitol Using Solid Acid Catalysis  

SciTech Connect

This is a final report for a project funded by the US Department of Agriculture and managed by the US Department of Energy. The Iowa Corn Promotion Board was the principal contracting entity for the grant. The Iowa Corn Promotion Board subcontracted with General Electric, Pacific Northwest National Lab and New Jersey Institute of Technology to conduct research in this project. The Iowa Corn Promotion Board and General Electric provided cost share for the project. The purpose of this diverse collaboration was to integrate both the conversion and the polymer applications into one project and increase the likelihood of success. This project has led to additional collaborations among other polymer companies. The goals of the project were to develop a renewable route to isosorbide for commercialization that is economically competitive with all existing production technologies and to develop new applications for isosorbide in various products such as polymers and materials. Under this program a novel process for the production of isosorbide was developed and evaluated. The novel process converts corn based sorbitol into isosorbide using a solid catalyst with integrated water removal and product recovery. In addition the work under this program has identified several novel products based on isosorbide chemistries. These market applications include: epoxy resins, UV stabilizers, plasticizers and polyesters. These market applications have commercial interest within the current polymer industry. This report contains an overview summary of the accomplishments. Six inventions and four patent applications have been written as a result of this project. Additional data will be published in the patent applications. The data developed at New Jersey Institute of Technology was presented at two technical conferences held in June of 2006. Several companies have made inquiries about using this material in their products.

Williamson, R.; Holladay,J.; Jaffe, M.; Brunelle, D.

2006-09-29

304

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

305

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

306

Stability and spinodal decomposition of the solid-solution phase in the ruthenium-cerium-oxide electro-catalyst.  

PubMed

The phase diagram of Ru-Ce-O was calculated by a combination of ab initio density functional theory and thermodynamic calculations. The phase diagram indicates that the solubility between ruthenium oxide and cerium oxide is very low at temperatures below 1100 K. Solid solution phases, if existing under normal experimental conditions, are metastable and subject to a quasi-spinodal decomposition to form a mixture of a Ru-rich rutile oxide phase and a Ce-rich fluorite oxide phase. To study the spinodal decomposition of Ru-Ce-O, Ru0.6Ce0.4O2 samples were prepared at 280 °C and 450 °C. XRD and in situ TEM characterization provide proof of the quasi-spinodal decomposition of Ru0.6Ce0.4O2. The present study provides a fundamental reference for the phase design of the Ru-Ce-O electro-catalyst. PMID:25418197

Li, Yanmei; Wang, Xin; Shao, Yanqun; Tang, Dian; Wu, Bo; Tang, Zhongzhi; Lin, Wei

2015-01-14

307

Sulfonic acid functionalized ionic liquid in combinatorial approach, a recyclable and water tolerant-acidic catalyst for one-pot Friedlander quinoline synthesis.  

PubMed

SO(3)H-functionalized ionic liquid was successfully applied as a water tolerant-acidic catalyst for the one-pot domino approach quinoline synthesis in aqueous medium. Various types of quinolines from 2-aminoaryl ketones and beta-ketoesters/ketones were prepared in 85-98% yields using the catalytic system of SO(3)H-functionalized ionic liquid/H(2)O. The ionic liquids was synthesized in a combinatorial fashion. The quinoline products could be conveniently separated from the reaction mixture by filtration, indicating that the whole process was performed in water and exemplifying a green chemistry. More importantly, the catalyst could be easily recycled for five times without loss of much activity. The catalytic system, reported here, possesses advantages of both homogeneous and heterogeneous catalysts. PMID:19883051

Akbari, Jafar; Heydari, Akbar; Reza Kalhor, Hamid; Kohan, Sirus Azizian

2010-01-01

308

Versatile and sustainable synthesis of cyclic imides from dicarboxylic acids and amines by Nb2O5 as a base-tolerant heterogeneous Lewis acid catalyst.  

PubMed

Catalytic condensation of dicarboxylics acid and amines without excess amount of activating reagents is the most atom-efficient but unprecedented synthetic method of cyclic imides. Here we present the first general catalytic method, proceeding selectively and efficiently in the presence of a commercial Nb2 O5 as a reusable and base-tolerant heterogeneous Lewis acid catalyst. The method is effective for the direct synthesis of pharmaceutically or industrially important cyclic imides, such as phensuximide, N-hydroxyphthalimide (NHPI), and unsubstituted cyclic imides from dicarboxylic acid or anhydrides with amines, hydroxylamine, or ammonia. PMID:25225033

Ali, Md Ayub; Siddiki, S M A Hakim; Kon, Kenichi; Hasegawa, Junya; Shimizu, Ken-Ichi

2014-10-27

309

Mesoporous Ti(0.5)Cr(0.5)N supported PdAg nanoalloy as highly active and stable catalysts for the electro-oxidation of formic acid and methanol.  

PubMed

We report a robust noncarbon Ti0.5Cr0.5N support synthesized by an efficient solid-solid phase separation method. This ternary nitride exhibits highly porous, sintered, and random network structure with a crystallite size of 20-40 nm, resulting in a high specific surface area. It is not only kinetically stable in both acid and alkaline media, but also electrochemically stable in the potential range of fuel cell operation. Two typical anode reactions, formic acid oxidation in acid media and methanol oxidation in alkaline media, are employed to investigate the possibility of Ti0.5Cr0.5N as an alternative to carbon. Bimetallic PdAg nanoparticles (?4 nm) act as anode catalysts for the two anode reactions. PdAg/Ti0.5Cr0.5N exhibits much higher mass activity and durability for the two reactions than PdAg/C and Pd/C catalyst, suggesting that mesoporous Ti0.5Cr0.5N is a very promising support in both acid and alkaline media. PMID:24836603

Cui, Zhiming; Yang, Minghui; DiSalvo, Francis J

2014-06-24

310

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

DOEpatents

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

311

The primary zone in the combustion of solid propellants containing catalysts  

SciTech Connect

Using a scanning electron microscope and an x-ray microprobe analyzer, we investigated the structure and composition of the combustion surface of the N propellant containing catalysts (PbO{sub 2}, CuO, PbO{sub 2} + CuO) which was extinguished at various pressures. Based on the obtained results, the heat-transfer coefficient was calculated for the layer above the catalyzed propellant combustion surface and found to be greater than that of the gas by factors ranging from 1.5 to 15. The calculation of the C-phase heat balance for the N propellant with additives showed that the rise in the combustion rate is caused by the increased quantity of heat entering into the C-phase from the zone above the combustion surface. Plus, the driving stage in the combustion of catalyzed propellants is the zone above the combustion surface and not the C-phase reaction layer, as in the case of the propellants without any catalysts.

Denisyuk, A.P.; Demidova, L.A.; Galkin, V.I. [D.I. Mendeleev Russian Chemical Methodology Univ., Moscow (Russian Federation)

1995-09-01

312

A Simple, Efficient Synthesis of 2-Aryl Benzimidazoles Using Silica Supported Periodic Acid Catalyst and Evaluation of Anticancer Activity  

PubMed Central

A new, efficient method for the synthesis of 2-aryl substituted benzimidazole by using silica supported periodic acid (H5IO6-SiO2) as a catalyst has been developed. The salient feature of the present method includes mild reaction condition, short reaction time, high yield and easy workup procedure. The synthesized benzimidazoles exhibited potent anticancer activity against MCF7 and HL60 cell lines. PMID:24052861

Sontakke, Vyankat A.; Ghosh, Sougata; Lawande, Pravin P.; Chopade, Balu A.; Shinde, Vaishali S.

2013-01-01

313

Implication of the acid–base properties of V\\/Ti-oxide catalyst in toluene partial oxidation  

Microsoft Academic Search

The work presents the effect of K-doping on V\\/Ti-oxides taking into account: the surface acid–base properties and the structure of surface vanadia species in respect to the catalyst performance and deactivation. The structure of active surface species determines redox properties, which are related to the catalytic performance by the Mars–van Krevelen mechanism. The reducibility of surface vanadia is studied by

Liubov Kiwi-Minsker; Dmitri A Bulushev; Fabio Rainone; Albert Renken

2002-01-01

314

Superheated water extraction and phase transfer methylation of phenoxy acid herbicides from solid matrices.  

PubMed

Phase transfer catalytic methylation was applied to directly derivatise chlorophenoxy acid herbicides in superheated water extracts from sand and soil samples. The extractions were carried out at 120 degrees C statically for 5 min and then dynamically for 10 min at 1.0 mL min(-1) using water at pH 11.0 for a sand matrix and a flow rate of 0.5 mL min(-1) at pH 7.0 for soil samples. The methylation was carried out on-line on the extraction solution with ultrasonication at 80 degrees C, using either 0.05 mmol tetrabutylammonium bromide (TBAB) or 0.0125 mmol cetyltrimethylammonium bromide (CTAB) as phase transfer catalysts with 0.20 mmol methyl iodide in 2.0 mL dichloromethane trapping solvent. The former catalyst provided a higher yield but the latter gave fewer interfering peaks. The recoveries of most chlorophenoxy acids using the TBAB catalyst ranged from 67 to 105% for sand and from 82 to 114% for soil sample, except phenoxyacetic acid, 2-(2, 4-dichlorophenoxy)propanoic acid and 1-naphthaleneacetic acid, while those by using CTAB were slightly lower. Detection limits of all the analytes extracted from sand using TBAB catalyst were in a range of 5.3-16 microg g(-1) analysed by using gas chromatography with flame ionization detection (GC-FID). PMID:17212966

Chienthavorn, Orapin; Pengpumkiat, Sumate; Noomhorm, Athapol; Smith, Roger M

2007-06-01

315

Photocatalytic detoxification of Acid Red 18 by modified ZnO catalyst under sunlight irradiation  

NASA Astrophysics Data System (ADS)

In this work, hybrid structured Bi-Au-ZnO composite was prepared by precipitation-decomposition method. This method is mild, economical and efficient. Bi-Au-ZnO was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive spectrum (EDS), diffuse reflectance spectra (DRS), photoluminescence spectra (PL) and BET surface area measurements. Photocatalytic activity of Bi-Au-ZnO was evaluated by irradiating the Acid Red 18 (AR 18) dye solution under sun light. Heterostructured Bi-Au-ZnO photocatalyst showed higher photocatalytic activity than those of individual Bi-ZnO, Au-ZnO, bare ZnO, and TiO2-P25 at pH 11. The effects of operational parameters such as the amount of catalyst dosage, dye concentration, initial pH on photo mineralization of AR 18 dye have been analyzed. The mineralization of AR 18 has been confirmed by chemical oxygen demand (COD) measurements. A possible mechanism is proposed for the degradation of AR 18 under sun light. Finally, Bi-Au-ZnO heterojunction photocatalyst was more stable and could be easily recycled several times opening a new avenue for potential industrial applications.

Senthilraja, A.; Subash, B.; Dhatshanamurthi, P.; Swaminathan, M.; Shanthi, M.

2015-03-01

316

Photocatalytic detoxification of Acid Red 18 by modified ZnO catalyst under sunlight irradiation.  

PubMed

In this work, hybrid structured Bi-Au-ZnO composite was prepared by precipitation-decomposition method. This method is mild, economical and efficient. Bi-Au-ZnO was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive spectrum (EDS), diffuse reflectance spectra (DRS), photoluminescence spectra (PL) and BET surface area measurements. Photocatalytic activity of Bi-Au-ZnO was evaluated by irradiating the Acid Red 18 (AR 18) dye solution under sun light. Heterostructured Bi-Au-ZnO photocatalyst showed higher photocatalytic activity than those of individual Bi-ZnO, Au-ZnO, bare ZnO, and TiO2-P25 at pH 11. The effects of operational parameters such as the amount of catalyst dosage, dye concentration, initial pH on photo mineralization of AR 18 dye have been analyzed. The mineralization of AR 18 has been confirmed by chemical oxygen demand (COD) measurements. A possible mechanism is proposed for the degradation of AR 18 under sun light. Finally, Bi-Au-ZnO heterojunction photocatalyst was more stable and could be easily recycled several times opening a new avenue for potential industrial applications. PMID:25437842

Senthilraja, A; Subash, B; Dhatshanamurthi, P; Swaminathan, M; Shanthi, M

2015-03-01

317

Improvement of the preparation method of “ship-in-the-bottle” type 12-molybdophosphoric acid encaged Y-type zeolite catalysts  

Microsoft Academic Search

In this work, efforts were made to improve the preparation method of “ship-in-the-bottle” type 12-molybdophosphoric acid (PMo12) encaged Y-type zeolite catalysts. First, the possibilities of modifying other popular heteropoly acid synthesis methods to prepare encaged catalysts were examined. It was found that only the conventional method, which uses MoO3 and H3PO4 for PMo12 synthesis, led to a significant amount of

Shin R Mukai; Mitsutaka Shimoda; Litsu Lin; Hajime Tamon; Takao Masuda

2003-01-01

318

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...

319

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

320

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

321

Sulfonic acid functionalized nano-?-Al2O3: a new, efficient, and reusable catalyst for synthesis of 3-substituted-2H-1,4-benzothiazines.  

PubMed

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

322

Influence of acid-pepsin secretion on gastric emptying of solids in humans: studies with cimetidine  

Microsoft Academic Search

The commonly accepted model for gastric emptying suggests that the 'antral mill' is responsible for the triturition and subsequent emptying of solid food from the stomach. Little is known about the contribution to solid emptying made by other digestive mechanisms such as acid-pepsin secretion. We have investigated the effect of inhibiting gastic secretion on the rate at which a solid

D D Kerrigan; Y F Mangnall; N W Read; A G Johnson

1991-01-01

323

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

324

The effect of the distance between acidic site and basic site immobilized on mesoporous solid on the activity in catalyzing aldol condensation  

SciTech Connect

Acid-base bifunctional heterogeneous catalysts containing carboxylic and amine groups, which were immobilized at defined distance from one another on the mesoporous solid were synthesized by immobilizing lysine onto carboxyl-SBA-15. The obtained materials were characterized by X-ray diffraction (XRD), N{sub 2} adsorption, Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron micrographs (SEM), transmission electron micrographs (TEM), elemental analysis, and back titration. Proximal-C-A-SBA-15 with a proximal acid-base distance was more active than maximum-C-A-SBA-15 with a maximum acid-base distance in aldol condensation reaction between acetone and various aldehydes. It appears that the distance between acidic site and basic site immobilized on mesoporous solid should be an essential factor for catalysis optimization. -- Graphical abstract: Proximal-C-A-SBA-15 with a proximal acid-base distance and maximum-C-A-SBA-15 with a maximum acid-base distance were synthesized by immobilizing lysine onto carboxyl-SBA-15. Display Omitted Research highlights: {yields} Proximal-C-A-SBA-15 with a proximal acid-base distance. {yields} Maximum-C-A-SBA-15 with a maximum acid-base distance. {yields} Compared to maximum-C-A-SBA-15, proximal-C-A-SBA-15 was more active toward aldol condensation reaction between acetone and various aldehydes.

Yu Xiaofang [College of Chemistry, Jilin University, Jiefang Road 2519, Changchun 130023 (China); Yu Xiaobo [China Pharmaceutical University, Nanjing 210009 (China); Wu Shujie; Liu Bo; Liu Heng [College of Chemistry, Jilin University, Jiefang Road 2519, Changchun 130023 (China); Guan Jingqi, E-mail: guanjq@jlu.edu.c [College of Chemistry, Jilin University, Jiefang Road 2519, Changchun 130023 (China); Kan Qiubin, E-mail: catalysischina@yahoo.com.c [College of Chemistry, Jilin University, Jiefang Road 2519, Changchun 130023 (China)

2011-02-15

325

Catalytic synthesis of diphenylmethane from benzene and formalin with water-tolerant solid acids  

Microsoft Academic Search

The synthesis of diphenylmethane (DPM) from benzene and formalin (a mixture of formaldehyde and water) or paraformaldehyde has been studied using various solid acids. The reaction between benzene and paraformaldehyde (oligomers of formaldehyde) proceeded readily at 140°C on typical solid acids. The activity of a silica-composite of polymer resin, Aciplex-SiO2, was found to be superior to that of other solid

Zhaoyin Hou; Toshio Okuhara

2001-01-01

326

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

327

Application of rare earth modified Zr-based ceria-zirconia solid solution in three-way catalyst for automotive emission control.  

PubMed

Automotive exhaust emission is a major cause of air pollution. Three-way catalyst (TWC) which can eliminate CO, HC (hydrocarbons), and NO(x) simultaneously has been used to control exhaust emissions. Ceria-zirconia is a key component in TWC and most researchers pay attention to Ceria-Zirconia (Ce-rich) solid solution. The research presented in this paper is focused on the intrinsic structure of Ceria-Zirconia (Zr-based) solid solution and its application in TWC. A series of Ce(0.2)Zr(0.8)O(2) modified with rare earths (La, Nd, Pr, Sm, and Y) have been prepared by coprecipitation method combined with supercritical drying technique. All samples showed single tetragonal solid solution, indicating that the rare earth ion inserted into the lattice structure completely, and an approximately linearly relationship between lattice parameter a and the ionic radius of doped rare earth was observed. The catalytic performances of corresponding Pd-only catalysts were investigated in simulated exhaust gas. The presence of La, Nd, and Pr was favorable to the catalytic activity and wide air/fuel operation window. The relationship between the intrinsic structure of the Zr-based ceria-zirconia solid solution and catalytic activity was discussed in detail, which has some reference value for catalyst design and application. PMID:20408547

Wang, Qiuyan; Zhao, Bo; Li, Guangfeng; Zhou, Renxian

2010-05-15

328

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

329

Decolorization of Acid Red 1 by Fenton-like process using rice husk ash-based catalyst.  

PubMed

The decolorization of Acid Red 1 (AR1) in aqueous solution was investigated by Fenton-like process. The effect of different reaction parameters such as different iron ions loading on rice husk ash (RHA), dosage of catalyst, initial pH, the initial hydrogen peroxide concentration ([H(2)O(2)](o)), the initial concentration of AR1 ([AR1](o)) and the reaction temperature on the decolorization of AR1 was studied. The optimal reacting conditions were found to be 0.070 wt.% of iron (III) oxide loading on RHA, dosage of catalyst=5.0 g L(-1), initial pH=2.0, [H(2)O(2)](o)=8 mM, [AR1](o)=50 mg L(-1) at temperature 30 degrees C. Under optimal condition, 96% decolorization efficiency of AR1 was achieved within 120 min of reaction. PMID:20042285

Daud, N K; Hameed, B H

2010-04-15

330

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

331

Formation of Linear Polyenes in Thermal Dehydration of Polyvinyl Alcohol, Catalyzed by Phosphotungstic Acid  

NASA Astrophysics Data System (ADS)

In order to obtain linear polyenes in polyvinyl alcohol films via acid-catalyzed thermal dehydration of the polyvinyl alcohol, we used phosphotungstic acid as the catalyst: a safe and heat-stable solid chemical compound. We established that phosphotungstic acid, introduced as solid nanoparticles into polyvinyl alcohol films, is a more effective dehydration catalyst than hydrochloric acid, since in contrast to HCl it does not evaporate from the film during heat treatment.

Tretinnikov, O. N.; Sushko, N. I.

2015-01-01

332

Easy solid-phase synthesis of pH-insensitive heterogeneous CNTs/FeS Fenton-like catalyst for the removal of antibiotics from aqueous solution.  

PubMed

We report a facile solid method to synthesize efficient carbon-based Fenton-like catalyst (CNTs/FeS) using as-prepared carbon nanotubes (APCNTs), which makes full use of the iron nanoparticles in APCNTs without needless purification. Furthermore, the CNTs/FeS was characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric (TG) and other analysis techniques, and then the CNTs/FeS was used as a Fenton-like catalyst for removing ciprofloxacin from aqueous solution. Response Surface Methodology (RSM) was applied to find the effect of the reaction parameter and the optimum operating condition. Results shows the catalytic reaction had better suitability than previous studies in a wide range of pH values (pH 3-8) and the Fenton-like catalyst CNTs/FeS exhibits good catalytic activity for removing of antibiotic, which be attributed to the synergistic effect of adsorption-advanced oxidation and significantly improves efficiency of advanced oxidation. More importantly, the CNTs/FeS catalyst exhibit good regeneration performance and retains a high catalytic capacity (>75%) even after four reaction cycles. The catalytic mechanism were also studied further, the removal mechanism of ciprofloxacin by a CNTs/FeS heterogeneous Fenton-like process primarily involves three removal pathways occurring simultaneously: (a) adsorption removal by CNTs, (b) Fenton-like degradation catalyzed by FeS, (c) catalytic degradation by CNTs catalyst. And these actions also have synergistic effects for ciprofloxacin removal. PMID:25585283

Ma, Jie; Yang, Mingxuan; Yu, Fei; Chen, Junhong

2015-04-15

333

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

334

AcidBase Mechanism for Ruthenium-Based Water Oxidation Catalysts  

Microsoft Academic Search

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 suggest a purely single-center mechanism. We find low activation energies (<5 kcal\\/mol) for each rearrangement in the catalytic cycle. In the crucial step of O-O bond formation, a solvent

L. P. Wang; Q. Wu; T. Van Voorhis

2010-01-01

335

Solid state radiolysis of non-proteinaceous amino acids in vacuum: astrochemical implications  

E-print Network

Solid state radiolysis of non-proteinaceous amino acids in vacuum: astrochemical implications´miai Kiado´, Budapest, Hungary 2012 Abstract The analysis of the amino acids present in Murchison meteorite and in other carbonaceous chondrites has revealed the presence of 66 different amino acids. Only eight

336

Version du 9/04/04 Optical basicity: a scale of acidity/basicity of solids  

E-print Network

reactions belong to the whole periodic table. Their role in catalysis depends mostly on their acid-base1 Version du 9/04/04 Optical basicity: a scale of acidity/basicity of solids and its application, J.A. Geochim. Cosmochim. Acta. 1993, 57, 3961-3970), a Lewis-related acidity/basicity scale

Paris-Sud XI, Université de

337

Comparison between Ni–Rh\\/gadolinia doped ceria catalysts in reforming of propane for anode implementations in intermediate solid oxide fuel cells  

Microsoft Academic Search

Steam and autothermal reforming of propane over Ni–Rh\\/GDC catalysts prepared by coprecipitation and by Pechini method were investigated in the temperature range 873–1073K. The weight ratio for Ni, Rh and Ce0.8Gd0.2O2 (45:5:50) and the operating temperatures were chosen in order to gain propaedeutical information on fuel reactivity under typical intermediate solid oxide fuel cell (IT-SOFC) operating conditions.The Pechini synthesis allows

M. Boaro; V. Modafferi; A. Pappacena; J. Llorca; V. Baglio; F. Frusteri; P. Frontera; A. Trovarelli; P. L. Antonucci

2010-01-01

338

Formation of Active Sites for Selective Toluene Oxidation during Catalyst Synthesis via Solid-State Reaction of V 2O 5 with TiO 2  

Microsoft Academic Search

Interaction of V2O5 with TiO2 during the preparation of V\\/Ti-oxide catalysts via solid-state reaction has been studied by means of in situ FT-Raman spectroscopy, HRTEM and XPS. This interaction results in the formation of monomeric vanadia species with vanadium in tetrahedral coordination. The bridging oxygen in the V–O–Ti bond is suggested to be responsible for the catalytic activity during the

Dmitri A. Bulushev; Lioubov Kiwi-Minsker; Vladimir I. Zaikovskii; Albert Renken

2000-01-01

339

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

SciTech Connect

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., E-mail: odowdbj@tcd.ie; Shvets, I. V. [CRANN, School of Physics, Trinity College, the University of Dublin, Dublin D2 (Ireland); Wojtowicz, T.; Kolkovsky, V.; Wojciechowski, T.; Zgirski, M. [Institute of Physics, Polish Academy of Sciences, Warsaw 02-668 (Poland); Rouvimov, S. [Notre Dame Integrated Imaging Facility (NDIIF), University of Notre Dame, Notre Dame, Indiana 46556 (United States); Liu, X.; Pimpinella, R.; Dobrowolska, M.; Furdyna, J. [Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556 (United States)

2014-08-14

340

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

341

Resonance Raman and surface- and tip-enhanced Raman spectroscopy methods to study solid catalysts and heterogeneous catalytic reactions.  

SciTech Connect

Resonance Raman (RR) spectroscopy has several advantages over the normal Raman spectroscopy (RS) widely used for in situ characterization of solid catalysts and catalytic reactions. Compared with RS, RR can provide much higher sensitivity and selectivity in detecting catalytically-significant surface metal oxides. RR can potentially give useful information on the nature of excited states relevant to photocatalysis and on the anharmonic potential of the ground state. In this critical review a detailed discussion is presented on several types of RR experimental systems, three distinct sources of so-called Raman (fluorescence) background, detection limits for RR compared to other techniques (EXAFS, PM-IRAS, SFG), and three well-known methods to assign UV-vis absorption bands and a band-specific unified method that is derived mainly from RR results. In addition, the virtues and challenges of surface-enhanced Raman spectroscopy (SERS) are discussed for detecting molecular adsorbates at catalytically relevant interfaces. Tip-enhanced Raman spectroscopy (TERS), which is a combination of SERS and near-field scanning probe microscopy and has the capability of probing molecular adsorbates at specific catalytic sites with an enormous surface sensitivity and nanometre spatial resolution, is also reviewed.

Kim, H.; Kosuda, K. M.; Van Duyne, R. P.; Stair, P. C. (Chemical Sciences and Engineering Division); (Northwestern Univ.)

2010-01-01

342

Nano-Structured Solids and Heterogeneous Catalysts: Powerful Tools for the Reduction of CBRN Threats  

NASA Astrophysics Data System (ADS)

In the field of non-conventional CBRN weapons, the recent rapid development of nanotechnology and catalysis over nanosized solids provides innovative tools for the detection, protection and decontamination against these threats. By improving the efficiency of the countermeasures and by minimizing the negative effects of a deliberate use of CBRN agents, the practical application of the new technologies will readily represent a step forward in lowering the vulnerability of the civilian populations and in preventing the use of mass destruction weapons by terrorist groups or by `rogue states' supporting terrorists' activity. In such scenario, some relevant examples of nanosystems applied to the defense from non-conventional warfare agents will be here presented and commented. The key role of nanotechnology and heterogeneous catalysis for a multidisciplinary approach in counteracting CBRN threats will be highlighted too.

Guidotti, M.; Rossodivita, A.; Ranghieri, M. C.

343

Sulfamic Acid as a Cost-Effective Catalyst for Synthesis of ? -acyloxyacrylate Esters as Candidate Monomers for Bio-Based Polymers by Acylation of Pyruvate Esters  

Microsoft Academic Search

Sulfamic acid was used as an efficient catalyst and green alternative for metal-containing acidic material to promote the acylation of pyruvate esters to produce ? -acyloxyacrylate esters which were candidate monomers for bio-based polymers. Polymers from these monomers were useful materials for bio-based plastics which showed high heat resistance and transparency. A series of ? -acyloxyacrylate esters were converted from

Zhenxin Zhang; Baochun Ma; Qianqian Zhu; Yong Ding; Changming Wang; Wenfeng Song

2012-01-01

344

Sulfamic Acid as A Cost-Effective Catalyst for Synthesis of ?-Acyloxyacrylate Esters as Candidate Monomers for Biobased Polymers by Acylation of Pyruvate Esters  

Microsoft Academic Search

Sulfamic acid was used as an efficient catalyst and green alternative for metal-containing acidic material to promote the acylation of pyruvate esters to produce ?-acyloxyacrylate esters, which were candidate monomers for biobased polymers. Polymers from these monomers were useful materials for bio-based plastics, which showed high heat resistance and transparency. A series of ?-acyloxyacrylate esters were converted from pyruvate esters

Zhenxin Zhang; Baochun Ma; Qianqian Zhu; Yong Ding; Changming Wang; Wenfeng Song

2012-01-01

345

Phosphonic acid functionalized ordered mesoporous material: a new and ecofriendly catalyst for one-pot multicomponent Biginelli reaction under solvent-free conditions.  

PubMed

We report a new ordered 2D hexagonal mesoporous organosilica material (PAFMS-1) bearing phosphonic acid functionality at the surface. This hybrid material showed high Brunauer-Emmett-Teller surface area (565 m(2) g(-1)) and ordered assembly of mesoporoes with an average pore diameter of ca. 2.1 nm. This novel hybrid mesoporous material has been synthesized via cocondensation of (triethoxysilyl)(propyliminomethyl)biphenylmethyl phosphoester (PEFOS) and tetraethyl orthosilicate (TEOS) in the presence of cationic surfactant cetyltrimethylammonium bromide (CTAB) at 373 K. The phosphoester-functionalized organosilane (PEFOS) precursor has been synthesized for the first time by a simple SN2 reaction followed by Suzuki coupling and a Mannich reaction. The material has been characterized by powder X-ray diffraction, N2 sorption, and transmission electron microscopy image analysis, whereas the presence of organic moieties (an aromatic biphenyl ring and an aliphatic side chain), phosphrous, and silicon in the pore wall of the material have been characterized by solid-state magic-angle-spinning NMR, X-ray photoelectron, and Fourier transform infrared (FT-IR) spectroscopic tools. Further, the surface acid strength of the hybrid material has been determined by FT-IR analysis of the samples via temperature-programmed pyridine adsorption studies. The material has been utilized as a reusable heterogeneous catalyst for the synthesis of biologically important and value added multifunctionalized 3,4-dihydropyridin-2-1H-(ones)/3,4-dihydropyridin-2-1H-(thiones) (DHPMs) through a multicomponent Biginelli condensation reaction under solvent-free conditions at 333 K. The phosphonic acid functionalized 2D hexagonal mesoporous material showed much higher catalytic activity in this multicomponent condensation reaction over sulfonic acid functionalized mesoporous silica (MCM-41-SO3H) bearing an aliphatic chain in the hybrid framework. PMID:24372168

Pramanik, Malay; Bhaumik, Asim

2014-01-22

346

Supported Molecular Catalysts: Synthesis, In-Situ Characterization and Performance  

SciTech Connect

The objectives of our work are: (i) to create solid catalysts with active sites that can function in a cooperative manner to enhance reactivity and selectivity, and (ii) to prepare solid catalysts that can perform multiple reactions in a network that in some cases would not be possible in solution due to the incompatibilities of the various catalytic entities (for example an acid and a base). We carried out extensive reactions to test the nature of the cooperative effect caused by thiol/sulfonic acid interactions. The acid/thiol combination provided an example where the two organic groups should be positioned as close to one another as possible. We also studied a system where this is not possible (acid-base). We investigated simultaneously incorporating acid and base groups into the same material. For the case of acid and bases, there is an optimal separation distance (too close allows for neutralization while too far eliminates any cooperative behavior).

Davis, Mark E.

2009-03-13

347

Fabrication of three dimensional (3D) hierarchical Ag/WO3 flower-like catalyst materials for the selective oxidation of m-xylene to isophthalic acid.  

PubMed

A three dimensional (3D) hierarchical silver supported tungsten oxide flower-like microsphere catalyst has been fabricated using a cationic surfactant CTAB. It was found that the crystal-splitting mechanism plays a key role in the formation of this flower-like structure. This catalyst was proved to be highly effective in the liquid phase selective oxidation of m-xylene to isophthalic acid. PMID:25740057

Acharyya, Shankha S; Ghosh, Shilpi; Bal, Rajaram

2015-04-01

348

Selective aerobic oxidation of 1,3-propanediol to 3-hydroxypropanoic acid using hydrotalcite supported bimetallic gold nanoparticle catalyst in water  

NASA Astrophysics Data System (ADS)

Selective oxidation of 1,3-propanediol (1,3-PD) to 3-hydroxypropanoic acid (3-HPA), an important industrial building block, was successfully achieved using hydrotalcite-supported bimetallic Au nanoparticle catalysts in water at 343 K under aerobic and base-free conditions. The highest yield of 42% with 73% selectivity towards 3-HPA was afforded by 1wt% Au0.8Pd0.2-PVP/HT catalyst.

Mohammad, Mujahid; Nishimura, Shun; Ebitani, Kohki

2015-02-01

349

Hazardous waste to materials: recovery of molybdenum and vanadium from acidic leach liquor of spent hydroprocessing catalyst using alamine 308.  

PubMed

Recovery of valuable materials/metals from waste goes hand in hand with environmental protection. This paper deals with the development of a process for the recovery of metals such as Mo, V, Ni, Al from spent hydroprocessing catalyst which may otherwise cause a nuisance if dumped untreated. A detailed study on the separation of molybdenum and vanadium from the leach solution of spent hydroprocessing catalyst of composition: 27.15% MoO?, 1.7% V?O?, 3.75% NiO, 54.3% Al?O?, 2.3% SiO? and 10.4% LOI is reported in this paper. The catalyst was subjected to roasting under oxidizing atmosphere at a temperature of about 550 °C and leaching in dilute sulphuric acid to dissolve molybdenum, vanadium, nickel and part of aluminium. Metals from the leach solution were separated by solvent extraction. Both molybdenum and vanadium were selectively extracted with a suitable organic solvent leaving nickel and dissolved aluminium in the raffinate. Various parameters such as initial pH of the aqueous feed, organic to aqueous ratio (O:A), solvent concentration etc. were optimized for the complete extraction and recovery of Mo and V. Molybdenum and vanadium from the loaded organic were stripped by ammonia solution. They were recovered as their corresponding ammonium salt by selective precipitation, and were further calcined to get the corresponding oxides in pure form. PMID:23644591

Sahu, K K; Agrawal, Archana; Mishra, D

2013-08-15

350

Acid Strength of Support Materials as a Factor Controlling Oxidation State of Palladium Catalyst for Propane Combustion  

Microsoft Academic Search

The support effect on the low temperature catalytic combustion of propane over palladium catalyst was studied by using a series of metal oxides as support materials: MgO, ZrO2, Al2O3, SiO2, SiO2–ZrO2, SiO2–Al2O3, and SO42?–ZrO2. The catalytic activity varied with the kind of the support materials; a support material with moderate acid strength gave maximum conversion. In order to discuss more

Yoshiteru Yazawa; Hisao Yoshida; Nobuyuki Takagi; Shin-ichi Komai; Atsushi Satsuma; Tadashi Hattori

1999-01-01

351

Acidic task-specific ionic liquid as catalyst of microwave-assisted solvent-free Biginelli reaction  

Microsoft Academic Search

A simple and effective synthesis of 3,4-dihydropyrimidin-2(1H)-one and 3,4-dihydropyrimidine-2(1H)-thione derivatives has been developed on the basis of three-component condensation of substituted aromatic and heterocyclic\\u000a aldehydes, methyl acetoacetate, and urea or thiourea in the presence of 10% of an acidic task-specific ionic liquid ([C4mim][HSO4]) as catalyst under microwave irradiation in the absence of a solvent. The proposed procedure ensures short reaction

A. Arfan; L. Paquin; J. P. Bazureau

2007-01-01

352

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

353

Improved zeolite regeneration processes for preparing saturated branched-chain fatty acids  

Technology Transfer Automated Retrieval System (TEKTRAN)

Ferrierite zeolite solid is an excellent catalyst for the skeletal isomerization of unsaturated linear-chain fatty acids (i.e., oleic acid) to unsaturated branched-chain fatty acids (i.e., iso-oleic acid) follow by hydrogenation to give saturated branched-chain fatty acids (i.e., isostearic acid). ...

354

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

355

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

356

SYNTHESIS OF TRIFLUOROMETHYL-IMINES BY SOLID ACID/SUPERACID CATALYZED MICROWAVE ASSISTED APPROACH  

PubMed Central

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, with solid superacid catalysis. Using the solid acid K-10 montmorillonite or the superacidic perfluorinated resinsulfonic acid Nafion-H, a wide variety of trifluoromethylated imines have been synthesized using the above methods. The products have been isolated in good to excellent yields and high selectivities. This new environmentally friendly synthetic methodology provides significantly higher yields than traditional methods during relatively short reaction times for the preparation of the target compounds. PMID:21949445

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

2009-01-01

357

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

358

Encapsulation of ployunsaturated fatty acid esters with solid lipid particles  

Technology Transfer Automated Retrieval System (TEKTRAN)

Polyunsaturated fatty acids (PUFA) such as a-linolenic acid (ALA) and docosahexaenoic acid (DHA) are known to improve cardiovascular and nervous system health. These compounds are increasingly used in food and animal feed formulations. However, the high degree of unsaturation in these structures can...

359

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

E-print Network

1,4-DIPB and 1,3,5-TIPB than the zeolite catalyst. Benzene selectivity was highest for ZSM-5 cracking of isopropyl-benzene, it is established that the cleavage of the propyl group from the benzene ring is the main reaction pathway with the benzene ring remaining unaltered.7 Moreover, transalkylation

Al-Khattaf, Sulaiman

360

A New, Improved, Solid-Acid Catalyzed Process for Generating Linear Alkylbenzenes (LABs)  

Microsoft Academic Search

Linear alkylbenzenes (LABs) comprising >80% 2-phenyl isomer content, have been prepared in high yields from detergent-range linear olefins via regioselective benzene alkylation. HF-treated mordenites, acidic Beta-zeolites, and fluorided montmorillonite clays, each provide enhanced shape-selective alkylation performance when employed as heterogeneous catalysts in the subject syntheses. Both individual C8–C12 a-olefins, as well as mixed, commercial plant-derived, C10 through C14 paraffin dehydrogenate

John F. Knifton; Prakasa Rao Anantaneni; P. Eugene Dai; Melvin E. Stockton

2001-01-01

361

Synthesis of 1?Indanones via Intramolecular Cyclodehydration of 3?Arylpropionic Acids Catalyzed by Heteropoly Acid as Heterogeneous Catalyst  

Microsoft Academic Search

Intramolecular cyclodehydration of 3?arylpropionic acids catalyzed by heteropoly acids was investigated for the first time. Several 3?arylpropionic acids were refluxed and dehydrated in chlorobenzene in the presence of 0.2 equivalent of heteropoly acids, and 1?indanones were obtained in good yield. At the same time, intermolecular Friedel–Crafts acylation were observed in this experiment.

Kun Lan

2007-01-01

362

Selective Hydrogenation of Lactic Acid to 1,2-Propanediol over Highly Active Ruthenium-Molybdenum Oxide Catalysts.  

PubMed

Modification of Ru/C with a small amount of MoOx (Ru?MoOx /C) enhanced the catalytic activity in the hydrogenation of L-lactic acid to form 1,2-propanediol and maintained high selectivity. The turnover frequency based on the amount of Ru over the optimized Ru?MoOx /C catalyst (Mo/Ru molar ratio=1:16) was 114?h(-1) at 393?K, which was about 4 times higher than that over Ru/C. The same effect of MoOx was obtained over Ru?MoOx /SiO2 , although Ru?MoOx /SiO2 showed slightly lower activity than that of Ru?MoOx /C. Ru?MoOx /C achieved a high yield of 95?% in 18?h at 393?K and was applicable to various carboxylic acids to provide the corresponding alcohols in high yields. Modification with MoOx also brought about suppression of racemization and (S)-1,2-propanediol was obtained in high enantiomeric excess at 353?K. Based on kinetic analysis and characterization data, such as XRD, TEM, CO adsorption by a volumetric method, FTIR spectroscopy, and X-ray absorption spectroscopy, for Ru?MoOx /C and Ru?MoOx /SiO2 , the catalyst structure and reaction mechanism are proposed. PMID:25510671

Takeda, Yasuyuki; Shoji, Tomohiro; Watanabe, Hideo; Tamura, Masazumi; Nakagawa, Yoshinao; Okumura, Kazu; Tomishige, Keiichi

2015-04-13

363

The Aerobic Oxidation of Bromide to Dibromine Catalyzed by Homogeneous Oxidation Catalysts and Initiated by Nitrate in Acetic Acid  

SciTech Connect

A small amount of nitrate, ~0.002 molal, initiates the Co/Mn catalyzed aerobic oxidation of bromide compounds (HBr,NaBr,LiBr) to dibromine in acetic acid at room temperature. At temperatures 40oC or less , the reaction is autocatalytic. Co(II) and Mn(II) themselves and mixed with ionic bromide are known homogeneous oxidation catalysts. The reaction was discovered serendipitously when a Co/Br and Co/Mn/Br catalyst solution was prepared for the aerobic oxidation of methyaromatic compounds and the Co acetate contained a small amount of impurity i.e. nitrate. The reaction was characterized by IR, UV-VIS, MALDI and EXAFS spectroscopies and the coordination chemistry is described. The reaction is inhibited by water and its rate changed by pH. The change in these variables, as well as others, are identical to those observed during homogeneous, aerobic oxidation of akylaromatics. A mechanism is proposed. Accidental addition of a small amount of nitrate compound into a Co/Mn/Br/acetic acid mixture in a large, commercial feedtank is potentially dangerous.

Partenheimer, Walt; Fulton, John L.; Sorensen, Christina M.; Pham, Van Thai; Chen, Yongsheng

2014-06-01

364

Hollow Ag@Pd core-shell nanotubes as highly active catalysts for the electro-oxidation of formic acid  

NASA Astrophysics Data System (ADS)

Ag nanowires are prepared as templates by a polyol reduction process. Then Ag nanotubes coated with a thin layer of Pd are synthesized through sequential reduction accompanied with the galvanic displacement reaction. The products show a hollow core-shell nanotubular structure, as demonstrated by detailed characterizations. The Ag@Pd can significantly improve the electrocatalytic activity towards the electro-oxidation of formic acid and enhance the stability of the Pd component. It is proposed that the enhanced electrochemically active surface area and modulated electron structure of Pd by Ag are responsible for the improvement of electrocatalytic activity and durability. The results obtained in this work are different from those previous reports, in which alloy walls with hollow interiors are usually formed. This work provides a new and simple method for synthesizing novel bimetallic core-shell structure with a hollow interior, which can be applied as high-performance catalysts for the electro-oxidation of formic acid.

Jiang, Yuanyuan; Lu, Yizhong; Han, Dongxue; Zhang, Qixian; Niu, Li

2012-03-01

365

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

366

Direct carbocyclizations of benzoic acids: catalyst-controlled synthesis of cyclic ketones and the development of tandem aHH (acyl Heck-Heck) reactions.  

PubMed

The formation of exo-methylene indanones and indenones from simple ortho-allyl benzoic acid derivatives has been developed. Selective formation of the indanone or indenone products in these reactions is controlled by choice of ancillary ligand. This new process has a low environmental footprint as the products are formed in high yields using low catalyst loadings, while the only stoichiometric chemical waste generated from the reactants in the transformation is acetic acid. The conversion of the active cyclization catalyst into the Hermman-Beller palladacycle was exploited in a one-pot tandem acyl Heck-Heck (aHH) reaction, and utilized in the synthesis of donepezil. PMID:25047136

Miles, Kelsey C; Le, Chi Chip; Stambuli, James P

2014-09-01

367

Biodiesel fuel production with solid superacid catalysis in fixed bed reactor under atmospheric pressure  

Microsoft Academic Search

Solid superacid catalysts of sulfated tin and zirconium oxides and tungstated zirconia are prepared and evaluated in the trans-esterification of soybean oil with methanol at 200–300 °C and the esterification of n-octanoic acid with methanol at 175–200 °C. Tungstated zirconia–alumina is a promising solid acid catalyst for the production of biodiesel fuels from soybean oil because of its high performance

Satoshi Furuta; Hiromi Matsuhashi; Kazushi Arata

2004-01-01

368

Solid-State Carbon-13 Nuclear Magnetic Resonance of Humic Acids at High Magnetic Field Strengths  

E-print Network

commonplace in studies of humic substances in soils and sediments, but when modern high-field spectrometersSolid-State Carbon-13 Nuclear Magnetic Resonance of Humic Acids at High Magnetic Field Strengths were insignificant, and spectral interference due humic acids taken under a variety of conditions. We

Hemminga, Marcus A.

369

Non-covalent interactions in water electrolysis: influence on the activity of Pt(111) and iridium oxide catalysts in acidic media.  

PubMed

Electrolyte components, which are typically not considered to be directly involved in catalytic processes at solid-liquid electrified interfaces, often demonstrate a significant or even drastic influence on the activity, stability and selectivity of electrocatalysts. While there has been certain progress in the understanding of these electrolyte effects, lack of experimental data for various important systems frequently complicates the rational design of new active materials. Modern proton-exchange membrane (PEM) electrolyzers utilize Pt- and Ir-based electrocatalysts, which are among the very few materials that are both active and stable under the extreme conditions of water splitting. We use model Pt(111) and Ir-oxide films grown on Ir(111) electrodes and explore the effect of alkali metal cations and sulfate-anions on the hydrogen evolution and the oxygen evolution reactions in acidic media. We demonstrate that sulfate anions decrease the activity of Ir-oxide towards the oxygen evolution reaction while Rb(+) drastically promotes hydrogen evolution reaction at the Pt(111) electrodes as compared to the reference HClO4 electrolytes. Issues related to the activity benchmarking for these catalysts are discussed. PMID:25412811

Ganassin, Alberto; Colic, Viktor; Tymoczko, Jakub; Bandarenka, Aliaksandr S; Schuhmann, Wolfgang

2014-11-21

370

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

371

Two-Stage Conversion of High Free Fatty Acid Jatropha curcas Oil to Biodiesel Using Brønsted Acidic Ionic Liquid and KOH as Catalysts  

PubMed Central

Biodiesel was produced from high free fatty acid (FFA) Jatropha curcas oil (JCO) by two-stage process in which esterification was performed by Brønsted acidic ionic liquid 1-(1-butylsulfonic)-3-methylimidazolium chloride ([BSMIM]Cl) followed by KOH catalyzed transesterification. Maximum FFA conversion of 93.9% was achieved and it reduced from 8.15?wt% to 0.49?wt% under the optimum reaction conditions of methanol oil molar ratio 12?:?1 and 10?wt% of ionic liquid catalyst at 70°C in 6?h. The ionic liquid catalyst was reusable up to four times of consecutive runs under the optimum reaction conditions. At the second stage, the esterified JCO was transesterified by using 1.3?wt% KOH and methanol oil molar ratio of 6?:?1 in 20?min at 64°C. The yield of the final biodiesel was found to be 98.6% as analyzed by NMR spectroscopy. Chemical composition of the final biodiesel was also determined by GC-MS analysis. PMID:24987726

Das, Subrata; Thakur, Ashim Jyoti; Deka, Dhanapati

2014-01-01

372

Novel stereo controlled glycosylation of 1,2,3,4,6-penta- o-acetyl-?- d-glucopyranoside using MgO–ZrO 2 as an environmentally benign catalyst  

Microsoft Academic Search

Glycosylation reactions are most commonly encountered in nature. Synthetically, glycosylations are carried out with Lewis acid catalysts or mineral acids. However an environmental threat associated with catalysts has encouraged process modification by alternative development of solid catalysts based glycosylation reactions, which are commercially viable as well. In this contribution comparative study of glycosidic bond formation of 1,2,3,4,6-penta-o-acetyl-?-d-glucopyranoside with various alcohols

Vishal Y. Joshi; Manohar R. Sawant

2007-01-01

373

The intrinsic acidity constants and specific surface area of marine solid particles  

Microsoft Academic Search

This paper deals with the infrared spectra of “amino acid-clay, calcium carbonate and ?-AlOOH” and “Cu(II)-clay-amino acid”\\u000a model systems, and shows that the model of the ternary surface complex is M-OHLCu (L=amino acid) for marine solid particle-Cu\\u000a (II)-amino acid. Study of the formation mechanism of the ternary surface complex shows that the specific surface area, and\\u000a especially the intrinsic acidity

Xiulin Wang; Zhengbin Zhang; Liansheng Liu

1992-01-01

374

Citric acid production from carob pod by solid-state fermentation  

Microsoft Academic Search

The production of citric acid from carob pod by Aspergillus niger in solid-state fermentation was investigated. The maximal citric acid concentration (176 ± 4 g kg?1 dry pod), biomass dry weight (30 ± 0.7 g kg?1 wet substrate), citric acid yield (55 ± 2%), and sugar utilization (64 ± 2.5%) were obtained at a particle size of 0.5 mm, moisture

T. Roukas

1999-01-01

375

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

376

High-resolution transmission electron microscopy study of carbon deposited on the NiO/MgO solid solution catalysts  

SciTech Connect

The carbon deposition due to the CH{sub 4} decomposition at 790 C over NiO/MgO catalysts was investigated by high-resolution transmission electron microscopy. While no deposits could be detected over the catalysts with a NiO content smaller than 9.1 wt%, they were detected over the catalysts with NiO contents of 23 and 50 wt%. The carbon deposits are composed of platelets located at distances of about 0.34 nm, corresponding to the graphitic carbon. Various structures of the deposited carbon were observed: (a) carbon consisting of platelets parallel to the surface of the particle, which covers a catalyst particle, (b) nanotubes composed of platelets parallel to their axis, and (c) carbon vortexes consisting of platelets parallel to their axis.

Hu, Y.H.; Ruckenstein, E. [State Univ. of New York, Buffalo, NY (United States). Dept. of Chemical Engineering] [State Univ. of New York, Buffalo, NY (United States). Dept. of Chemical Engineering

1999-05-15

377

Impact of Dry Solids and Bile Acid Concentrations on Bile Acid Binding Capacity of Extruded Oat Cereals  

Technology Transfer Automated Retrieval System (TEKTRAN)

Extruded breakfast cereals (EBC), processed from two oat lines, N979-5-2-4 (N979) and ‘Jim’, with beta-glucan concentrations of 8.7 and 4.9%, respectively, were used to determine the impact of dry solids (DS) and bile acid (BA) concentrations on in vitro BA binding efficiency. A full fractional fact...

378

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

379

Solid-State Forms of ?-Resorcylic Acid: How Exhaustive Should a Polymorph Screen Be?  

PubMed Central

A combined experimental and computational study was undertaken to establish the solid-state forms of ?-resorcylic acid (2,4-dihydroxybenzoic acid). The experimental search resulted in nine crystalline forms: two concomitantly crystallizing polymorphs, five novel solvates (with acetic acid, dimethyl sulfoxide, 1,4-dioxane, and two with N,N-dimethyl formamide), in addition to the known hemihydrate and a new monohydrate. Form II°, the thermodynamically stable polymorph at room temperature, was found to be the dominant crystallization product. A new, enantiotropically related polymorph (form I) was obtained by desolvation of certain solvates, sublimation experiments, and via a thermally induced solid?solid transformation of form II° above 150 °C. To establish their structural features, interconversions, and relative stability, all solid-state forms were characterized with thermal, spectroscopic, X-ray crystallographic methods, and moisture-sorption analysis. The hemihydrate is very stable, while the five solvates and the monohydrate are rather unstable phases that occur as crystallization intermediates. Complementary computational work confirmed that the two experimentally observed ?-resorcylic acid forms I and II° are the most probable polymorphs and supported the experimental evidence for form I being disordered in the p-OH proton position. These consistent outcomes suggest that the most practically important features of ?-resorcylic acid crystallization under ambient conditions have been established; however, it appears impractical to guarantee that no additional metastable solid-state form could be found. PMID:21218174

2010-01-01

380

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.

381

Synthesis of a new fluorescent macrocyclic [alpha]-amino acid derivative via tandem cross-enyne\\/ring-closing metathesis cascade catalyzed by ruthenium based catalysts  

Microsoft Academic Search

A simple methodology to a unique macrocyclic ?-amino acid (AAA) derivative involving three step synthetic sequence has been reported. In addition, various ruthenium based catalysts were studied to enhance the selectivity of the desired macrocyclic AAA derivative 6. The fluorescence behavior of these AAA derivatives 5 and 6 indicate their potential applications in biological sciences as biomarkers, ion sensors and

Sambasivarao Kotha; Deepti Bansal; Kuldeep Singh; Subhasree Banerjee

2011-01-01

382

Fe2(S04)3 * Xh2o in Synthesis: A Convenient and Efficient Catalyst for the Esterification of Aromatic Carboxylic Acids With Alcohols  

Microsoft Academic Search

Fe2(S04)3 XH2O has been used for the catalyst in the esterification of aromatic carboxylic acids with alcohols. The method offers mild reaction condition, easy work-up, and high yields of the esterification products.

Gui-Sheng Zhang

1999-01-01

383

Influence of acid catalysts on the structural and magnetic properties of nanocrystalline barium ferrite prepared by sol–gel method  

Microsoft Academic Search

BaFe12O19 powders with nanocrystalline size were prepared by sol–gel techniques. Nitric, hydrochloric, acetic and stearic acid were used to improve the magnetic properties. Amorphous gels were formed with Fe\\/Ba molar ratio of 10.5. Then powders were obtained by subsequent heat treatment at 800–1000°C for 1h. Barium ferrite powder was also synthesized by solid state reaction at 1210°C. X-ray diffraction, scanning

Ebrahim Paimozd; Ali Ghasemi; Abdolhamid Jafari; Hassan Sheikh

2008-01-01

384

The performance of perovskites and spinels as catalysts for oxygen reduction in solid oxide fuel cell cathodes  

NASA Astrophysics Data System (ADS)

The lack of understanding of the catalytic process at the state-of-the-art cathode material surface in solid oxide fuel cells, (La0.8Sr 0.2)0.98MnO3+delta (LSM), has hindered the design of better catalysts. The objectives of this study were to design a system enabling the comparison of catalytic activities of different cathode materials independently of morphological factors, as well as to resolve catalytic processes at the LSM surface. The selection and optimization of potential cathode materials were performed on the basis of thermal expansion, four-probe dc-conductivity and thermoelectric power measurements in air. The materials studied as potential cathodes were tungsten, niobium and molybdenum doped barium cobaltite perovskites, copper manganese, cobalt manganese and cobalt ferrite spinels as well as strontium doped lanthanum cobalt ferrites and lanthanum manganite perovskites. The doped barium cobaltites were found lo offer superior electrical conductivity when octahedral site transition metal average valence was mixed 3+ /4+ compared to mixed 2+/3+. On the other hand, the loss of conductivity associated with octahedral site doping rendered these materials inadequate for solid oxide fuel cells (SOFC) cathode applications. Copper manganese spMd was found to exhibit electrical conductivity as high as ˜200 S.cm-1 at 1073 K and thermal expansion ˜ 11 ppm/K between 298 K and 1200 K. Thermal and chrono-potentiometric studies were used to determine the oxygen diffusivity, in cobalt and strontium doped lanthanum iron perovskites (LSCF), and revealed that the activation of strontium doped lanthanum manganese perovskites (LSM) under cathodic bias is kinetically limited by its rate of oxygen surface exchange, suggesting that the cathodic activation of LSM is due to its change in oxygen content under bias. The electronic defect structure of the cubic spinels was resolved in a defect reaction model involving the thermally activated redox of Cu + and Mn4+ to Cu2+ and Mn3+, as well as the disproportionation of Jahn-Teller ion Mn3+ into Mn2+ and Mn4+ and demonstrated that copper doping enhanced the amount of Mn4+ on octahedral sites. Cyclic voltammetry and potential-dependent electrochemical impedance spectroscopy studies of dense (La0.8Sr0.2)0.98MnO3+delta polycrystalline films revealed that the rate determining step in the oxygen reduction reaction, in the conditions of our study was the first charge transfer between oxygen ad-atoms and octahedral manganese III, as described by (S)Oad + MnxMn?O -adS +Mn•Mn. The catalytic activity of CuzMn3-- zO4 cubic spinets was found superior to that of LSM and of stoichiometrie CoFe2O4 and Co2MnO 4 spinal at intermediate temperature, suggesting that the Mn 3+/Mn4+ redox couple on octahedral sites plays a major role in the catalysis of the oxygen reduction reaction on those transition metal oxide surfaces.

Martin, Boris E.

385

In situ nanocrystalline HZSM-5 zeolites encaged heteropoly acid H 3 PMo 12 O 40 and Ni catalyst for hydroconversion of n-octane  

Microsoft Academic Search

The heteropoly acid H3PMo12O40 (PMo) and Ni in situ encaged in the secondary pore of nanocrystalline HZSM-5 zeolites was prepared from molybdenum oxide and phosphoric acid and nickel nitrate, in a slurry mixture of nanocrystalline HZSM-5 zeolite crystals and deionized water. Catalysts were characterized by ICP, FT-IR, XRD, 31P MAS-NMR, ESR, Py-IR, NH3-TPD, BET, SEM and TEM. PMo cannot enter

Lidong Chen; Xiangsheng Wang; Xinwen Guo; Hongchen Guo; Hai’ou Liu; Yongying Chen

2007-01-01

386

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

387

Synergistic Interplay of a Non-Heme Iron Catalyst and Amino Acid Coligands in H2 O2 Activation for Asymmetric Epoxidation of ?-Alkyl-Substituted Styrenes.  

PubMed

Highly enantioselective epoxidation of ?-substituted styrenes with aqueous H2 O2 is described by using a chiral iron complex as the catalyst and N-protected amino acids (AAs) as coligands. The amino acids synergistically cooperate with the iron center in promoting an efficient activation of H2 O2 to catalyze epoxidation of this challenging class of substrates with good yields and stereoselectivities (up to 97?%?ee) in short reaction times. PMID:25599973

Cussó, Olaf; Ribas, Xavi; Lloret-Fillol, Julio; Costas, Miquel

2015-02-23

388

Highly efficient and chemo selective catalyst system for the synthesis of blossom orange fragrance and flavoring compounds  

Microsoft Academic Search

Acetal and acylal formation reactions of organic compounds are efficiently catalyzed by zirconia-supported mixed oxide systems under liquid-phase reaction conditions. 15WZ-750 (where, W=WO3 and Z=ZrO2) was the most active catalyst, which could be recyclable without loss in its activities. This study reports the use of a non zeolitic solid acid catalyst systems based on zirconia-supported isopoly and heteropoly acids, which

Josena Justus; Ajayan Vinu; Biju M. Devassy; Veerappan V. Balasubramanian; Walter Bohringer; Jack Fletcher; S. B. Halligudi

2008-01-01

389

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

390

Ultrasound assisted arylation of benzyl alcohol with 4-nitrochlorobenzene under a new multi-site phase-transfer catalyst in solid-liquid condition.  

PubMed

The ultrasound assisted preparation of 1-(benzyloxy)-4-nitrobenzene from the reaction of 4-chloronitrobenzene (CNB) and benzyl alcohol was carried out successfully using potassium hydroxide and catalyzed by a new multi-site phase-transfer catalyst (MPTC) viz., 1,3,5-triethyl-1,3,5-trihexyl-1,3,5-triazinane-1,3,5-triium trichloride in a solid-liquid reaction condition (SL-MPTC). The advantage of using SL-MPTC is to avoid a serious hydration of potassium salt of benzyl alcohol in the reaction between 4-chloronitrobenzene (CNB) and benzyl alcohol. The reaction is greatly enhanced in the solid-liquid system, catalyzed by multi-site quaternary ammonium salt (MPTC) and ultrasound irradiation (40 kHz, 300 W) in a batch reactor, it shows that the overall reaction greatly enhanced with ultrasound irradiation than without ultrasound. The reaction mechanism is proposed and verified by examining the experimental evidence. A kinetic model is proposed in which a pseudo first-order rate law is sufficient to describe the results, such as the effects of agitation speed, ultrasound, different phase transfer catalysts and the effect of organic solvents, the amount of newly prepared MPTC, the effect of temperature, the amount of water, the concentration of 4-chloronitrobenzene (CNB) and potassium hydroxide concentrations. The apparent rate constant (kapp) were investigated in detail. Rational explanations to account for the phenomena on the results were made. PMID:24830817

Selvaraj, Varathan; Abimannan, Pachaiyappan; Rajendran, Venugopal

2014-09-01

391

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

392

Studies on the identification of the heteropoly acid generated in the H 3PO 4–WO 3–Nb 2O 5 catalyst and its thermal transformation process  

Microsoft Academic Search

The precursor of the mixed metal oxide catalyst composed of H3PO4–WO3–Nb2O5, which exhibits excellent activity in Friedel–Crafts alkylations, was identified with 31P NMR. It was revealed that the Keggin-type mixed heteropoly acid, H4PNbW11O40, was spontaneously generated during preparation of the H3PO4–WO3–Nb2O5 catalyst. The partial decomposition of H4PNbW11O40 occurred in the temperature range of 673–823 K to give an amorphous oxide

Kazu Okumura; Katsuhiko Yamashita; Kazuhiro Yamada; Miki Niwa

2007-01-01

393

A simple, efficient and environmentally benign synthetic protocol for the synthesis of spirooxindoles using choline chloride-oxalic acid eutectic mixture as catalyst/solvent system.  

PubMed

An efficient and environmentally benign domino protocol has been presented for the synthesis of structurally diverse spirooxindoles spiroannulated with pyranopyridopyrimidines, indenopyridopyrimidines, and chromenopyridopyrimidines involving three-component reaction of aminouracils, isatins and cyclic carbonyl compounds in deep eutectic solvent (choline chloride-oxalic acid: 1:1) which acts as efficient catalyst and environmentally benign reaction medium. The present protocol offers several advantages such as operational simplicity with easy workup, shorter reaction times excellent yields with superior atom economy and environmentally benign reaction conditions with the use of cost-effective, recyclable, non-toxic and bio-degradable DES as catalyst/solvent. PMID:25329839

Khandelwal, Sarita; Rajawat, Anshu; Tailor, Yogesh Kumar; Kumar, Mahendra

2014-01-01

394

Influence of the preparative method on the activity of highly acidic WO{sub x}/ZrO{sub 2} and the relative acid activity compared with zeolites  

SciTech Connect

The acid activity of the solid tungsten/zirconia can be affected by the catalyst preparation method. Reflux of the hydrous zirconia prior to tungsten impregnation gives a catalyst with higher surface area than the nonrefluxed material, 62 vs 32 m{sup 2}/g, but with the same strong acid site density, as determined by n-pentane isomerization activity. It is also shown that the simultaneous coprecipitation of tungsten with the formation of hydrous zirconia yields a catalyst with about two times the strong acid site density of WO{sub x}/ZrO{sub 2} catalysts prepared by impregnation. 30 refs., 6 figs., 12 tabs.

Santiesteban, J.G.; Vartuli, J.C.; Han, S. [Mobil Technology Company, Paulsboro, NJ (United States)] [and others] [Mobil Technology Company, Paulsboro, NJ (United States); and others

1997-06-01

395

Formation routes of interstellar glycine involving carboxylic acids: possible favoritism between gas and solid phase.  

PubMed

Despite the extensive search for glycine (NH?CH?COOH) and other amino acids in molecular clouds associated with star-forming regions, only upper limits have been derived from radio observations. Nevertheless, two of glycine's precursors, formic acid and acetic acid, have been abundantly detected. Although both precursors may lead to glycine formation, the efficiency of reaction depends on their abundance and survival in the presence of a radiation field. These facts could promote some favoritism in the reaction pathways in the gas phase and solid phase (ice). Glycine and these two simplest carboxylic acids are found in many meteorites. Recently, glycine was also observed in cometary samples returned by the Stardust space probe. The goal of this work was to perform theoretical calculations for several interstellar reactions involving the simplest carboxylic acids as well as the carboxyl radical (COOH) in both gas and solid (ice) phase to understand which reactions could be the most favorable to produce glycine in interstellar regions fully illuminated by soft X-rays and UV, such as star-forming regions. The calculations were performed at four different levels for the gas phase (B3LYP/6-31G*, B3LYP/6-31++G**, MP2/6-31G*, and MP2/6-31++G**) and at MP2/6-31++G** level for the solid phase (ice). The current two-body reactions (thermochemical calculation) were combined with previous experimental data on the photodissociation of carboxylic acids to promote possible favoritism for glycine formation in the scenario involving formic and acetic acid in both gas and solid phase. Given that formic acid is destroyed more in the gas phase by soft X-rays than acetic acid is, we suggest that in the gas phase the most favorable reactions are acetic acid with NH or NH?OH. Another possible reaction involves NH?CH? and COOH, one of the most-produced radicals from the photodissociation of acetic acid. In the solid phase, we suggest that the reactions of formic acid with NH?CH or NH?CH?OH are the most favorable from the thermochemical point of view. PMID:22066498

Pilling, Sergio; Baptista, Leonardo; Boechat-Roberty, Heloisa M; Andrade, Diana P P

2011-11-01

396

Pineapple waste - a novel substrate for citric acid production by solid-state fermentation  

Microsoft Academic Search

Citric acid production in solid-state fermentation by Aspergillus foetidus ACM3996 was better on pineapple waste than on apple pomace, wheat bran or rice bran. The highest citric acid content achieved on pineapple waste was 16.1 g per 100 g dried pineapple waste, with a moisture content of 70% and in the presence of 3% methanol. This represents a yield of

Chau T. Tran; David A. Mitchell

1995-01-01

397

Relevance of the Hard-Soft AcidBase (HSAB) Principle to Solid Adhesion  

Microsoft Academic Search

In this paper, the acid-base interaction is shown to consist of at least two major components: the electrostatic (or ionic) and charge transfer (or covalent). To complement existing acid-base theories, we further demonstrate the relevance of the density-functional theory to surface interactions and solid adhesion. On the basis of the density-functional theory, two chemical parameters, i.e., chemical potential ? and

Lieng-Huang Lee

1991-01-01

398

Anomalous Defect\\/Impurity Dominated Dielectric Behaviour of Lauric Acid in the Solid Phase  

Microsoft Academic Search

The dieiectric permittivity and loss of solid lauric acid (C11H23COOH) at. audio and radio frequencies are reported for the temperature range from 1.5K to near the melting point No features attributable to confirsurational interchange within the acid-dimer groups are observed. The peculiarities of the data are discussed in terms of the liquid-liKe regions associated with impurity and defect centres.

S. R. Gough

1981-01-01

399

Design and synthesis of palladium/graphitic carbon nitride/carbon black hybrids as high-performance catalysts for formic acid and methanol electrooxidation  

NASA Astrophysics Data System (ADS)

Here we report a facile two-step method to synthesize high-performance palladium/graphitic carbon nitride/carbon black (Pd/g-C3N4/carbon black) hybrids for electrooxidizing formic acid and methanol. The coating of g-C3N4 on carbon black surface is realized by a low-temperature heating treatment, followed by the uniform deposition of palladium nanoparticles (Pd NPs) via a wet chemistry route. Owning to the significant synergistic effects of the individual components, the preferred Pd/g-C3N4/carbon black electrocatalyst exhibits exceptional forward peak current densities as high as 2155 and 1720 mA mg-1Pd for formic acid oxidation in acid media and methanol oxidation in alkaline media, respectively, far outperforming the commercial Pd-C catalyst. The catalyst also shows reliable stability, demonstrating that the newly-designed hybrids have great promise in constructing high-performance portable fuel cell systems.

Qian, Huayu; Huang, Huajie; Wang, Xin

2015-02-01

400

CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES: Electro-oxidation of Formic Acid on Carbon Supported Edge-Truncated Cubic Platinum Nanoparticles Catalysts  

NASA Astrophysics Data System (ADS)

The oxidation of formic acid on edge-truncated cubic platinum nanoparticles/C catalysts is investigated. X-ray photoelectron spectroscopy analysis indicates that the surface of edge-truncated cubic platinum nanoparticles is composed of two types of coordination sites. The oxidation behavior of formic acid on edge-truncated cubic platinum nanoparticles/C is investigated using cyclic voltammetry. The apparent activation energies are found to be 54.2, 55.0, 61.8, 69.5, 71.9, 69.26, 65.28kJ/mol at 0.15, 0.3, 0.4, 0.5, 0.6, 0.65, 0.7V, respectively. A specific surface area activity of 1.76 mA·cm-2 at 0.4 V indicates that the edge-truncated cubic Platinum nanoparticles are a promising anode catalyst for direct formic acid fuel cells.

Li, She-Qiang; Fu, Xing-Qiu; Hu, Bing; Deng, Jia-Jun; Chen, Lei

2009-11-01

401

Enhanced production of ganoderic acids and cytotoxicity of Ganoderma lucidum using solid-medium culture.  

PubMed

Submerged cultures of Ganoderma lucidum are used to produce fungal mycelium, which is used as a functional food and in the production of various triterpenoids, including ganoderic acids (GAs). Specific culture approaches that produce fungal mycelium with high levels of GAs and good biological activity are critical in the functional food industry. In this study, a solid-medium culture approach to producing mycelium was compared to the submerged culture system. Production of GAs, biomass, intracellular polysaccharides, and cytotoxicity of the cultured mycelium were compared as between solid and submerged culture. Growing G. lucidum strains on solid potato dextrose agar medium increased biomass, the production of ganoderic acid 24 (lanosta-7,9(11), 24-trien-3?-o1-26-oic acid), GAs, and total intracellular polysaccharides as compared to fungi grown in submerged culture. Triterpenoid-enriched methanol extracts of mycelium from solid-medium culture showed higher cytotoxicity than those from submerged culture. The IC(50) values of methanol extracts from solid-medium culture were 11.5, 8.6, and 9.9 times less than submerged culture on human lung cancer cells CH27, melanoma cells M21, and oral cancer cells HSC-3 respectively. The squalene synthase and lanosterol synthase coding genes had higher expression on the culture of solid potato dextrose medium. This is the first report that solid-medium culture is able to increase GA production significantly as compared to submerged culture and, in the process, produces much higher biological activity. This indicates that it may be possible to enhance the production of GAs by implementing mycelium culture on solid medium. PMID:22878212

You, Bang-Jau; Lee, Hong-Zin; Chung, Kuang-Ren; Lee, Miin-Huey; Huang, Mei-Jung; Tien, Ni; Chan, Chiao-Wei; Kuo, Yueh-Hsiung

2012-01-01

402

Domain-confined catalytic soot combustion over Co3O4 anchored on a TiO2 nanotube array catalyst prepared by mercaptoacetic acid induced surface-grafting.  

PubMed

Herein, we introduce a specially designed domain-confined macroporous catalyst, namely, the Co3O4 nanocrystals anchored on a TiO2 nanotube array catalyst, which was synthesized by using the mercaptoacetic acid induced surface-grafting method. This catalyst exhibits much better performance for catalytic soot combustion than the conventional TiO2 powder supported one in gravitational contact mode (GMC). PMID:24177172

Ren, Jiale; Yu, Yifu; Dai, Fangfang; Meng, Ming; Zhang, Jing; Zheng, Lirong; Hu, Tiandou

2013-12-21

403

Inoculation onto Solid Surfaces Protects Salmonella spp. during Acid Challenge: a Model Study Using Polyethersulfone Membranes  

PubMed Central

Salmonellae are the most frequently reported cause of outbreaks of food-borne gastroenteritis in the United States. In clinical trials, the oral infective dose (ID) for healthy volunteers was estimated to be approximately 1 million cells. However, in reports from various outbreaks, the ID of Salmonella species associated with solid foods was estimated to be as few as 100 cells. We found that fresh-cut produce surfaces not only provided suitable solid support for pathogen attachment but also played a critical role in increasing the acid tolerance of the pathogen. However the acidic nature of certain produce played no role in making salmonellae resistant to stomach acidity. Inoculation onto fresh-cut produce surfaces, as well as onto inert surfaces, such as polyethersulfone membranes and tissue paper, increased the survival of salmonellae during acid challenge (50 mM Na-citrate, pH 3.0; 37°C; 2 h) by 4 to 5 log units. Acid challenge experiments using cells inoculated onto polyethersulfone membranes provided a model system suitable for studying the underlying fundamentals of the protection that occurs when Salmonella strains are associated with solid foods. The surface-associated acid protection, which was observed in several Salmonella strains, required de novo protein synthesis and was independent of stationary-phase sigma transcription factor. PMID:11772613

Gawande, Purushottam V.; Bhagwat, Arvind A.

2002-01-01

404

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

405

Brønsted Acid Co-catalysts in Photocatalytic Radical Addition of ?-Amino C–H Bonds Across Michael Acceptors  

PubMed Central

In marked contrast to the variety of strategies available for oxidation and nucleophilic functionalization of methylene groups adjacent to amines, relatively few approaches for modification of this position with electrophilic reaction partners have been reported. In the course of an investigation of the reactions of photogenerated ?-amino radicals with electrophiles, we made the surprising observation that the efficiency of radical photoredox functionalization of N-aryl tetrahydroisoquinolines is dramatically increased in the presence of a Brønsted acid co-catalyst. Optimized conditions provide high yields and efficient conversion to radical addition products for a range of structurally modified tetrahydroisoquinolines and enones using convenient household light sources and commercially available Ru(bpy)3Cl2 as a photocatalyst. Our investigations into the origins of this unexpected additive effect have demonstrated that the carbon–carbon bond-forming step is accelerated by TFA and is a rare example of Brønsted acid catalysis in radical addition reactions. Moreover, a significant conclusion arising from these studies is the finding that product formation is dominated by radical chain processes and not by photocatalyst turnover. Together, these findings have important implications for the future design and mechanistic evaluation of photocatalytic radical processses. PMID:23537318

Espelt, Laura Ruiz; Wiensch, Eric M.; Yoon, Tehshik P.

2013-01-01

406

Solid-State 17O NMR Study of Benzoic Acid Adsorption On Metal Oxide Surfaces  

SciTech Connect

Solid-state 17O NMR spectra of 17O-labeled benzoic and anisic acids are reported and benzoic acid is used to probe the surface of metal oxides. Complexes formed when benzoic acid is dry-mixed with mesoporous silica, and nonporous titania and alumina are characterized. Chemical reactions with silica are not observed. The nature of benzoic acid on silica is a function of the water content of the oxide. The acid disperses in the pores of the silica if the silica is in equilibrium with ambient laboratory humidity. The acid displays high mobility as evidenced by a liquid-like, Lorentzian resonance. Excess benzoic acid remains as the crystalline hydrogen-bonded dimer. Benzoic acid reacts with titania and alumina surfaces in equilibrium with laboratory air to form the corresponding titanium and aluminum benzoates. In both materials the oxygen of the 17O-labeled acid is bound to the metal, showing the reaction proceeds by bond formation between oxygen deficient metal sites and the oxygen of the carboxylic acid. 27Al MAS NMR confirms this mechanism for the reaction on alumina. Dry mixing of benzoic acid with alumina rapidly quenches pentacoordinate aluminum sites, excellent evidence that these sites are confined to the surface of the alumina particles.

Hagaman, Edward {Ed} W [ORNL; Chen, Banghao [ORNL; Jiao, Jian [ORNL; Parsons, Williams [Oak Ridge National Laboratory (ORNL)

2012-01-01

407

New materials for solar thermal storage—solid\\/liquid transitions in fatty acid esters  

Microsoft Academic Search

Solid\\/liquid transitions were studied by DSC measurements in the following fatty acid esters: methyl stearate, methyl palmitate, cetyl stearate, cetyl palmitate and their binary mixtures. Four systems, with phase transition temperature close to room temperature and with high enthalpy of transition and low hysteresis, were selected for further studies relevant to passive solar thermal storage. The selected systems were: methyl

R Nikoli?; M Marinovi?-Cincovi?; S Gadžuri?; I. J Zsigrai

2003-01-01

408

Halogen bond induced phosphorescence of capped ?-amino acid in the solid state.  

PubMed

The Boc and N,N'-dicyclohexylurea capped ?-amino acid upon monobromination showed phosphorescence in the solid state. The compound exhibited different photoluminescence intensity and lifetimes in crystals obtained from ethyl acetate and methanol. X-ray crystallography revealed that the intermolecular C=O…Br halogen bond directs the heavy atom effect to produce the phosphorescence. PMID:23985996

Maity, Suman Kumar; Bera, Santu; Paikar, Arpita; Pramanik, Apurba; Haldar, Debasish

2013-10-11

409

Ultrasensitive detection of nitroexplosive - picric acid via a conjugated polyelectrolyte in aqueous media and solid support.  

PubMed

Picric acid (PA) detection at parts per trillion (ppt) levels is achieved by a conjugated polyelectrolyte (PMI) in 100% aqueous media and on a solid platform using paper strips and chitosan (CS) films. The unprecedented selectivity is accomplished via combination of ground state charge transfer and resonance energy transfer (RET) facilitated by favorable electrostatic interactions. PMID:25811533

Hussain, Sameer; Malik, Akhtar Hussain; Afroz, Mohammad Adil; Iyer, Parameswar Krishnan

2015-04-01

410

Valproic acid-hydrophilic cyclodextrin complexes and valproic acid-solid dispersions: evaluation of their potential pharmaceutical use.  

PubMed

The purpose of this study was to evaluate the potential use of two novel solid formulations of valproic acid (VPA) prepared by complexation with hydrophilic cyclodextrins (CDs) as hydroxypropyl-beta- and sulfobutylether-beta-cyclodextrin and by solid dispersion (SD) in hydrophilic carriers as polyethylene glycol 6000 (PEG 6000) and polyvinylpyrrolidone K-30 (PVP K-30). The corresponding cyclodextrin-based complexes were prepared by the freeze-drying method while the solid dispersions were obtained by the solvent method. Valproic acid solubility improved by CDs complexation and solid dispersion techniques. Comparison of dissolution profiles with that of VPA sodium salt (NaVP) was made by using release parameters such as dissolution efficiency, percent of drug dissolved after 60 min, and difference and similarity factors. Based on difference and similarity factors, it can be concluded that all the VPA formulations possess dissolution profiles essentially equivalent to those of NaVP at pH 6. However, this conclusion is not confirmed by using the analysis of variance (ANOVA) approach, indicating some significant differences between some SD-based formulations and NaVP at that pH value. Preliminary pharmacological studies in the pentylenetetrazole test in rats showed some important differences among the SD-based formulations, NaVP, and VPA as oil/water emulsion. Some implications and limitations of the investigated formulations are discussed. PMID:15000430

Trapani, G; Cutrignelli, A; Latrofa, A; Franco, M; Serra, M; Pisu, M G; Biggio, G; Liso, G

2004-01-01

411

Tessaric acid derivatives induce G2/M cell cycle arrest in human solid tumor cell lines.  

PubMed

A series of analogs were synthesized in a straightforward manner from naturally available sesquiterpenes ilicic acid and tessaric acid. The in vitro antiproliferative activities were examined in the human solid tumor cell lines A2780, HBL-100, HeLa, SW1573, T-47D and WiDr. The most potent analog induced considerably growth inhibition in the range 1.9-4.5 microM. Cell cycle studies for tessaric acid derivatives indicated a prominent arrest of the cell cycle at the G(2)/M phase. Damage to the cells was permanent as determine by the so called 24+24 drug schedule. PMID:19664930

León, Leticia G; Donadel, Osvaldo J; Tonn, Carlos E; Padrón, José M

2009-09-01

412

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

413

Oxidative degradation of different chlorinated phenoxyalkanoic acid herbicides by a hybrid ZrO2 gel-derived catalyst without light irradiation.  

PubMed

The oxidative degradation of 2-methyl-4-chlorophenoxyacetic acid (MCPA), 4-(4-chloro-2-methylphenoxy)butanoic acid (MCPB), 4-chlorophenoxyacetic acid (4-CPA) and 2,4-dichlorophenoxyacetic acid (2,4 D) by ZrO2-acetylacetonate hybrid catalyst (HSGZ) without light irradiation was assessed. The thermal stability of the catalyst was investigated by thermogravimetry, differential thermal analysis, and Fourier transform infrared spectroscopy. For each herbicide, a virtually complete removal in about 3 days without light irradiation at room temperature was achieved. The removal kinetics of the herbicides has been satisfactorily characterized by a double-stage physico-mathematical model, in the hypothesis that a first-order adsorption on HSGZ surface is followed by the herbicide degradation, catalytically driven by HSGZ surface groups. The long-term use of the HSGZ catalyst was assessed by repeated-batch tests. The specific cost for unit-volume removal of herbicide was evaluated by a detailed cost analysis showing that it is comparable with those pertaining to alternative methods. PMID:25479367

Sannino, Filomena; Pernice, Pasquale; Minieri, Luciana; Camandona, Gaia Aurora; Aronne, Antonio; Pirozzi, Domenico

2015-01-14

414

Effects of natural water ions and humic acid on catalytic nitrate reduction kinetics using an alumina supported Pd-Cu catalyst.  

PubMed

Catalytic nitrate reduction was evaluated for the purpose of drinking water treatment. Common anions present in natural waters and humic acid were evaluated for their effects on NO3(-) hydrogenation over a bimetallic supported catalyst (Pd-Cu/gamma-Al2O3). Groundwater samples, with and without powder activated carbon (PAC) pretreatment, were also evaluated. In the absence of inhibitors the NO3- reduction rate was 2.4 x 10(-01) L/min g cat. However, the addition of constituents (SO4(2-), SO3(2-), HS-, CI-, HCO3-, OH-, and humic acid) on the order of representative concentrations for drinking water decreased the NO3- reduction rate. Sulfite, sulfide, and elevated chloride decreased the NO3- reduction rate by over 2 orders of magnitude. Preferential adsorption of Cl- inhibited NO3- reduction to a greater extent than NO2- reduction. Partial regeneration of catalysts exposed to SO3(2-) was achieved by using a dilute hypochlorite solution, however Cu dissolution occurred. Dissolved constituents in the groundwater sample decreased the NO3- reduction rate to 3.7 x 10(-03) L/min g cat and increased ammonia production. Removal of dissolved organic matter from the groundwater using PAC increased the NO3- reduction rate to 5.06 x 10(-02) L/min g cat and decreased ammonia production. Elemental analyses of catalysts exposed to the natural groundwater suggest that mineral precipitation may also contribute to catalyst fouling. PMID:16719114

Chaplin, Brian P; Roundy, Eric; Guy, Kathryn A; Shapley, John R; Werth, Charles J

2006-05-01

415

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

416

Solid supported in situ derivatization extraction of acidic degradation products of nerve agents from aqueous samples.  

PubMed

This study deals with the solid supported in situ derivatization extraction of acidic degradation products of nerve agents present in aqueous samples. Target analytes were alkyl alkylphosphonic acids and alkylphosphonic acids, which are important environmental signatures of nerve agents. The method involved tert-butyldimethylchlorosilane mediated in situ silylation of analytes on commercially available diatomaceous solid phase extraction cartridges. Various parameters such as derivatizing reagent, its concentration, reaction time, temperature and eluting solvent were optimized. Recoveries of the analytes were determined by GC-MS which ranged from 60% to 86%. The limits of detection (LOD) and limit of quantification (LOQ) with selected analytes were achieved down to 78 and 213ngmL(-1) respectively, in selected ion monitoring mode. The successful applicability of method was also demonstrated on samples of biological origin such as plasma and to the samples received in 34th official proficiency test conducted by the Organization for Prohibition the of Chemical Weapons. PMID:25103280

Chinthakindi, Sridhar; Purohit, Ajay; Singh, Varoon; Tak, Vijay; Dubey, D K; Pardasani, Deepak

2014-09-12

417

Combustion Catalysts in Industry- An Update  

E-print Network

Combustion catalysts improve boiler efficiency by extracting more heat energy from the fuel and by reducing heat losses when operating at minimum excess air. In addition, an effective combustion catalyst may reduce the level of smoke and solid...

Merrell, G. A.; Knight, R. S.

418

The oxidation of tetrabromobisphenol A by potassium monopersulfate with an iron(III)-phthalocyanine-tetrasulfonic acid catalyst in the presence of humic acid.  

PubMed

Tetrabromobisphenol A (TBBPA), a type of brominated flame retardant that shows endocrine disruption effects, has been identified in leachates from landfills. Iron(III)-porphyrins that mimic the active site of peroxidases have been shown to be effective in oxidizing halogenated phenols, such as TBBPA. In the present study, TBBPA was subjected to oxidation with potassium monopersulfate (KHSO5) using an iron(III)-phthalocyanine-tetrasulfonic acid (FePcTS), structural analogue of iron(III)-porphyrin, in the presence of humic acid (HA), a major component in landfill leachates. When TBBPA was oxidized using the above system, the levels of degradation and debromination increased with increasing pH in the presence of HA. Because of landfill leachates are weakly alkaline (around pH 8), oxidation products derived from TBBPA were investigated at pH 8. Approximately 48% of the bromine in the degraded TBBPA was incorporated into HA, and hydroxy-tribromobisphenol A was determined to be the major brominated intermediate in the HA fraction. In the iron(III)-porphyrin catalytic systems, the brominated intermediate incorporated into HA is mainly TBBPA, and no hydroxy-substituted bromophenols are found. Thus, the catalytic power of FePcTS is higher than that of iron(III)-porphyrin catalysts. PMID:24798896

Maeno, Shohei; Mizutani, Yusuke; Zhu, Qianqian; Miyamoto, Takafumi; Fukushima, Masami; Kuramitz, Hideki

2014-01-01

419

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

420

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

421

Process of making supported catalyst  

DOEpatents

Oxide supported metal catalysts have an additional metal present in intimate association with the metal catalyst to enhance catalytic activity. In a preferred mode, iridium or another Group VIII metal catalyst is supported on a titania, alumina, tungsten oxide, silica, or composite oxide support. Aluminum ions are readsorbed onto the support and catalyst, and reduced during calcination. The aluminum can be added as aluminum nitrate to the iridium impregnate solution, e.g. chloroiridic acid.

Schwarz, James A. (Fayetteville, NY); Subramanian, Somasundaram (Melvindale, MI)

1992-01-01

422

Mesoporous Silica-Supported Diarylammonium Catalysts for Esterification of Free Fatty Acids in Greases  

Technology Transfer Automated Retrieval System (TEKTRAN)

Biodiesel, typically fatty acid methyl esters (FAME), has received much attention because it is a renewable biofuel that contributes little to global warming compared to petroleum-based diesel fuel. The most common method used for biodiesel production is based on the alkali-catalyzed transesterific...

423

A chemical placebo: NaCl as an effective, cheapest, non-acidic and greener catalyst for Biginelli-type 3,4-dihydropyrimidin-2(1H)-ones (-thiones) synthesis.  

PubMed

Despite prior reports of several really effective catalytic and non-catalytic approaches towards Biginelli's 3,4-dihydropyrimidin-2(1H)-ones, an overwhelming number of new catalysts for the Biginelli reaction have been recently published. Most of the catalysts are somewhat exotic, expensive, harmful and even uneffective in the absence of acidic additives. Herein we reduce the "yet-another-one-catalyst" idea to absurdity by proposing NaCl promotes the reaction that actually requires no catalyst, neither rare nor expensive. PMID:19082754

Kolosov, Maksim A; Orlov, Valeriy D; Beloborodov, Dmitriy A; Dotsenko, Victor V

2009-02-01

424

Sonochemical synthesis of silica and silica sulfuric acid nanoparticles from rice husk ash: a new and recyclable catalyst for the acetylation of alcohols and phenols under heterogeneous conditions.  

PubMed

Silica nanoparticles were synthesized from rice husk ash at room temperature by sonochemical method. The feeding rate of percipiteting agent and time of sonication were investigated. The nanostructure of the synthesized powder was realized by the FE-SEM photomicrograph, FT-IR spectroscopy, XRD and XRF analyses. These analytical observations have revealed that the nano-sized amorphous silica particles are formed and they are spheroidal in shape. The average particle size of the silica powders is found to be around 50 nm. The as-synthesized silica nanoparticles were subsequently modified with chlorosulfonic acid and prepared silica sulfuric acid nanoparticles, which were employed as an efficient catalyst for the acylation of alcohols and phenols with acetic anhydride in excellent yields under solvent-free conditions at room temperature. This reported method is simple, mild, and environmentally viable and catalyst can be simply recovered and reused over 9 times without any significant loss of its catalytic activity. PMID:22934954

Salavati-Niasari, Masoud; Javidi, Jaber

2012-11-01

425

New Lewis-Acidic Molybdenum(II) and Tungsten(II) Catalysts for Intramolecular Carbonyl Ene and Prins Reactions. Reversal of the Stereoselectivity of Cyclization of Citronellal.  

PubMed

New Mo(II) complexes BnEt(3)N(+)[Mo(CO)(4)ClBr(2)](-) (A) and Mo(CO)(5)(OTf)(2) (B) and their W(II) congeners D and E have been developed as catalysts for the title reactions. Unlike other Lewis acids, the latter catalysts exhibit cis-stereoselectivity in the cyclization of citronellal (1 --> 3 with A and 1 --> 5 with B). Isotopic labeling allowed formulation of the reaction mechanism, according to which these complexes act as bulky Lewis acids, eta(1)-coordinated to the carbonyl oxygen. The stereochemistry appears to be controlled by the protruding ligand L(p), which dictates the boatlike transition state III. The kinetically formed cis-alkenol 3 can be equilibrated by [Mo(CO)(4)Br(2)](2) (C) or ZnCl(2) to its trans-epimer 2 via a retro-ene reaction. PMID:11674345

Kocovský, Pavel; Ahmed, Ghafoor; Srogl, Jirí; Malkov, Andrei V.; Steele, John

1999-04-16

426

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

427

Preparation and evaluation of advanced catalysts for phosphoric acid fuel cells  

NASA Technical Reports Server (NTRS)

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 with the influence of low concentrations of carbon monoxide in the fuel gas stream. In a similar way, these platinum on carbon electrocatalysts were evaluated for oxygen reduction in hot phosphoric acid. Binary noble metal alloys were prepared for anodic oxidation of hydrogen and noble metal-refractory metal mixtures were prepared for oxygen reduction. An exemplar alloy of platinum and palladium (50/50 atom %) was discovered for anodic oxidation of hydrogen in the presence of carbon monoxide, and patent disclosures were submitted. For the cathode, platinum-vanadium alloys were prepared showing improved performance over pure platinum. Preliminary experiments on electrocatalyst utilization in electrode structures showed low utilization of the noble metal when the electrocatalyst loading exceeded one weight percent on the carbon.

Stonehart, P.; Baris, J.; Hockmuth, J.; Pagliaro, P.

1984-01-01

428

Development of efficient Lewis acid catalysts for intramolecular cycloaddition reactions of ester-tethered substrates.  

PubMed

We have developed novel bidentate Lewis acids that efficiently promote the intramolecular cycloaddition reactions of ester-tethered substrates. Bis-aluminated triflic amide derivatives [TfN(AlR(1)R(2))2], which are generated by simply mixing triflic amide and 2 equiv of methyl aluminum or aluminum hydride, catalyzed intramolecular Diels-Alder (DA) reactions of ester-tethered 1,7,9-trienes and intermolecular DA reactions of alpha,beta-unsaturated lactones. We also found that bimetallic Lewis acid derived from 1,1'-biphenyl-2,2'-di(triflyl)amide and dimethylaluminum chloride promoted the intramolecular [3 + 2] cycloaddition reaction of acrylate derivatives having an allylsilane part. PMID:17549689

Taguchi, Takeo; Saito, Akio; Yanai, Hikaru

2007-01-01

429

Radionuclide Leaching from Residual Solids Remaining after Acid Dissolution of Composite K East Canister Sludge  

SciTech Connect

Laboratory tests were performed to examine mixed nitric/hydrofluoric acid leach treatments for decontaminating dissolver residual solids (KECDVSR24H-2) produced during a 20- to 24-hr dissolution of a composite K East (KE) Basin canister sludge in 95 C 6 M nitric acid (HNO{sub 3}). The scope of this testing has been described in Section 4.5 of ''Testing Strategy to Support the Development of K Basin Sludge Treatment Process'' (Flament 1998). Radionuclides sorbed or associated with the residual solids generated in the K Basin sludge treatment process can restrict disposal of this solid to the Environmental Restoration Disposal Facility (ERDF). The starting dissolver residual solid for this testing, KECDVSR24H-2, contains radionuclides at concentrations which exceed the ERDF Waste Acceptance Criteria for TRU by about a factor of 70, for {sup 239}Pu by a factor of 200, and for {sup 241}Am by a factor of 50. The solids also exceed the ERDF criterion for {sup 137}Cs by a factor of 2 and uranium by a factor of 5. Therefore, the radionuclides of greatest interest in this leaching study are first {sup 239}Pu and {sup 241}Am (both components of TRU) and then uranium and {sup 137}Cs.

Delegard, C.H.; Rinehart, D.E.; Soderquist, C.Z.; Fadeff, S.K.

1999-04-02

430

Gas-phase isomerization of ethylbenzene over PT-heteropoly acid\\/zeolite catalysts  

Microsoft Academic Search

The catalytic performance and availability of heleropoly compounds in vapor phase isomerizalion of elhylbenzene to xylene\\u000a have been studied. 12-molybdophosphoric acid and its salts of four first row transition metals (Cr. Fe, Co and Ni) were chosen\\u000a as heteropoly compounds, and they were supported together with platinum over Y-zeolite. The experiments were carried out at\\u000a 400‡C, 18 kg\\/cm2 of H2

Gun Dae Lee; Tae Joon Han; Ho-In Lee

1986-01-01

431

Mesoporous Silica-Supported Diarylammonium Catalysts for Esterification of Free Fatty Acids in Greases  

Microsoft Academic Search

Biodiesel (BD), typically consisting of fatty acid methyl esters (FAME), has received much attention because it is a renewable\\u000a biofuel that contributes little to global warming compared to petroleum-based diesel fuel. The most common method used for\\u000a BD production is based on the alkali-catalyzed transesterification of first-use refined oils and fats with an alcohol (e.g.\\u000a methanol). These technologies, however, require

Helen L. NgoNicholas; Nicholas A. Zafiropoulos; Thomas A. Foglia; Edward T. Samulski; Wenbin Lin

2010-01-01

432

Polycondensation reaction and its mechanism during lignocellulosic liquefaction by an acid catalyst: a review  

Microsoft Academic Search

The increase in the residue content resulting from polycondensation would be adverse to the utilization of lignocellulose\\u000a and to the quality of products obtained from liquefied lignocellulosic material. The yield of the residue formed from liquefaction\\u000a and the mechanism of polycondensation were reported mainly by Lin, Yamada and Kobayashi. The major products of cellulosic\\u000a liquefaction are levulinic acid and hydroxymethylfurfural

Min Niu; Guang-jie Zhao; Mehmet Hakki Alma

2011-01-01

433

Catalyst-Free and Site-Specific One-Pot Dual Labeling of a Protein Directed by Two Genetically Incorporated Noncanonical Amino Acids  

PubMed Central

The genetic incorporation of one azide-containing and one keto-containing noncanonical amino acids into a protein at one amber and one ochre mutation sites respectively followed by their orthogonal reactions with one hydroxylamine-containing and one cyclooctyne-containing dyes allows highly efficient one-pot site-specific dual labeling of the protein in a catalyst-free fashion. PMID:22628069

Wu, Bo; Wang, Zhiyong; Huang, Ying; Liu, Wenshe R.

2012-01-01

434

[Catalytic application of synthesizing n-butyl acrylate by a new type nanometer complex heteropoly acid catalyst H3PW12O40/SiO2].  

PubMed

A new nanometer complex heteropoly acid with Keggin structure, H3PW12O40/SiO2, were prepared by sol-gel method, and were characterized with IR, UV, XRD and TEM techniques. By means of this nanometer catalytic materials, the optimum conditions of the n-butyl acrylate synthesis have been studied. The results show that the complex heteropoly acid H3PW12O40/SiO2 nanoparticles have the mean grain size of 40 nm and they are typical amorphous. A strong chemical interaction exists between H3PW12O40 and silica surface. The nanoparticles have high catalytic activity for synthesizing n-butyl acrylate. The optimum catalytic conditions are as follows: the mole ratio of acrylic acid and n-butyl alcohol is 1:1.2, the reaction temperature is approximately 90-96 degrees C, and the catalyst quantity in the reaction is 10% of the acid mass. The conversion proportion is 94.37% and product yield 91.2% in 5 h. Apparently, the unique structure of the Keggin anions and surface acid center and the high specific surface area and the pseudoliquid phase of H3PW12O40/SiO2 play an important role in the esterification reactions with the acid catalyst. PMID:15760024

Zhou, Li-qun; Liu, Shi-zhong; Sun, Ju-tang

2004-10-01

435

Use of pyrolyzed iron ethylenediaminetetraacetic acid modified activated carbon as air-cathode catalyst in microbial fuel cells.  

PubMed

Activated carbon (AC) is a cost-effective catalyst for the oxygen reduction reaction (ORR) in air-cathode microbial fuel cells (MFCs). To enhance the catalytic activity of AC cathodes, AC powders were pyrolyzed with iron ethylenediaminetetraacetic acid (FeEDTA) at a weight ratio of FeEDTA:AC = 0.2:1. MFCs with FeEDTA modified AC cathodes and a stainless steel mesh current collector produced a maximum power density of 1580 ± 80 mW/m(2), which was 10% higher than that of plain AC cathodes (1440 ± 60 mW/m(2)) and comparable to Pt cathodes (1550 ± 10 mW/m(2)). Further increases in the ratio of FeEDTA:AC resulted in a decrease in performance. The durability of AC-based cathodes was much better than Pt-catalyzed cathodes. After 4.5 months of operation, the maximum power density of Pt cathode MFCs was 50% lower than MFCs with the AC cathodes. Pyridinic nitrogen, quaternary nitrogen and iron species likely contributed to the increased activity of FeEDTA modified AC. These results show that pyrolyzing AC with FeEDTA is a cost-effective and durable way to increase the catalytic activity of AC. PMID:23902951

Xia, Xue; Zhang, Fang; Zhang, Xiaoyuan; Liang, Peng; Huang, Xia; Logan, Bruce E

2013-08-28

436

SYNTHESIS OF ALKYL AND ARYLPHOSPHONIC ACID MONOESTERS BY DIRECT ESTERIFICATION OF DIBASIC PHOSPHONIC ACIDS IN THE PRESENCE OF AN ARSONIC ACID CATALYST  

Microsoft Academic Search

Partial hydrolysis of a diester, hydrolysis of the monochloro monoester, or alcoholysis of a phosphonic acid anhydride generally is used to prepare monoesters of alkyl- and arylphosphonic acids. Limited cases have been reported for the esterification of a dibasic phosphonic acid to yield the monoester, and none of these methods are as simple as the analogous method for preparing carboxylic

Michael D. Crenshaw

2004-01-01

437

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

438

Surface Acidity and Solid-State Compatibility of Excipients with an Acid-Sensitive API: Case Study of Atorvastatin Calcium.  

PubMed

The objectives of this study were to measure the apparent surface acidity of common excipients and to correlate the acidity with the chemical stability of an acid-sensitive active pharmaceutical ingredient (API) in binary API-excipient powder mixtures. The acidity of 26 solid excipients was determined by two methods, (i) by measuring the pH of their suspensions or solutions and (ii) the pH equivalent (pHeq) measured via ionization of probe molecules deposited on the surface of the excipients. The chemical stability of an API, atorvastatin calcium (AC), in mixtures with the excipients was evaluated by monitoring the appearance of an acid-induced degradant, atorvastatin lactone, under accelerated storage conditions. The extent of lactone formation in AC-excipient mixtures was presented as a function of either solution/suspension pH or pHeq. No lactone formation was observed in mixtures with excipients having pHeq > 6, while the lactone levels were pronounced (> 0.6% after 6 weeks at 50°C/20% RH) with excipients exhibiting pHeq < 3. The three pHeq regions (> 6, 3-6, and < 3) were consistent with the reported solution pH-stability profile of AC. In contrast to the pHeq scale, lactone formation did not show any clear trend when plotted as a function of the suspension/solution pH. Two mechanisms to explain the discrepancy between the suspension/solution pH and the chemical stability data were discussed. Acidic excipients, which are expected to be incompatible with an acid-sensitive API, were identified based on pHeq measurements. The incompatibility prediction was confirmed in the chemical stability tests using AC as an example of an acid-sensitive API. PMID:25319055

Govindarajan, Ramprakash; Landis, Margaret; Hancock, Bruno; Gatlin, Larry A; Suryanarayanan, Raj; Shalaev, Evgenyi Y

2015-04-01

439

Methanation catalyst recovery  

Microsoft Academic Search

Shell Oil Co. has developed a new system to recover the catalyst used for methanation processes in solids or liquids gasification. Methane is continuously produced by contacting a sulfur-containing gaseous reactant mixture (hydrogen, carbon monoxide and\\/or carbon dioxide) in a reaction zone maintained at temperatures above about 932°F (500°C) with a molten-metal salt-based catalyst system. This system consists of a

T. E. Kiovsky; M. M. Wald

1977-01-01

440

Transformations of anthraquinone-1-nitro-2-carboxylic acid during reduction by hydrogen on a catalyst  

SciTech Connect

We studied the catalytic reduction of anthraquinone-1-nitro-2-carboxylic acid by hydrogen under a pressure of 0.1-5.5 MPa and at temperatures of 20-100/sup 0/C in different solvents. The concentration of the substrate was varied from 0.05 to 0.3 mole/dm/sub 3/. A 5% palladium on carbon was used in a thermostated ideal mixing reactor. The process was controlled by the rate of absorption of hydrogen; polarographic, spectral and GLC methods of analysis were used to identify the compounds and to evaluate the quantitative composition of the products.

Rogovik, V.M.; Dzvinka, R.I.; Vinyukova, M.V.

1987-11-20

441

Metal-loaded CeO 2-ZrO 2 solid solutions as innovative catalysts for automotive catalytic converters  

Microsoft Academic Search

The redox behaviour of a Ce0.5Zr0.5O2 solid solution is investigated by means of temperature programmed reduction (TPR) and oxygen uptake measurements. It is shown that the introduction of ZrO2 into the CeO2 framework, strongly modifies the reduction behaviour in comparison to pure CeO2. Remarkably, in contrast to the CeO2, upon repetitive reduction-oxidation processes, the temperature of reduction of the solid

Paolo Fornasiero; Gabriele Balducci; Sergio Meriani; Roberta di Monte; Mauro Graziani

1996-01-01

442

Iron oxide nanoparticles immobilized to mesoporous NH2-SiO2 spheres by sulfonic acid functionalization as highly efficient catalysts  

NASA Astrophysics Data System (ADS)

A novel SiO2 nanosphere was synthesized by the post-synthetic grafting of sulfonic acid groups on to anionic-surfactant-templated mesoporous NH2-silica (AMAS). This one-pot post-functionalization strategy allowed more metal ions to be homogeneously anchored into the channel of the meso-SiO2 nanosphere. After hydrothermal and calcination treatment, the in situ growth of ?-Fe2O3 on sulfonic acid-functionalized mesoporous NH2-SiO2 (SA-AMAS) exhibited much higher activity in the visible-light assisted Fenton reaction at neutral pH than that for AMAS or meso-SiO2 nanospheres. By analysis, the grafted sulfonic acid group can not only enhance the acid strength of the catalyst, but can also bring more orbital-overlapping between the active sites (FeII and FeIII) and the surface peroxide species, to facilitate the decomposition of H2O2 to hydroxyl radical. The present results provide opportunities for developing heterogeneous catalysts with high-performance in the field of green chemistry and environmental remediation.A novel SiO2 nanosphere was synthesized by the post-synthetic grafting of sulfonic acid groups on to anionic-surfactant-templated mesoporous NH2-silica (AMAS). This one-pot post-functionalization strategy allowed more metal ions to be homogeneously anchored into the channel of the meso-SiO2 nanosphere. After hydrothermal and calcination treatment, the in situ growth of ?-Fe2O3 on sulfonic acid-functionalized mesoporous NH2-SiO2 (SA-AMAS) exhibited much higher activity in the visible-light assisted Fenton reaction at neutral pH than that for AMAS or meso-SiO2 nanospheres. By analysis, the grafted sulfonic acid group can not only enhance the acid strength of the catalyst, but can also bring more orbital-overlapping between the active sites (FeII and FeIII) and the surface peroxide species, to facilitate the decomposition of H2O2 to hydroxyl radical. The present results provide opportunities for developing heterogeneous catalysts with high-performance in the field of green chemistry and environmental remediation. Electronic supplementary information (ESI) available: BET surface area and textural data, degradation results, FTIR spectra, TEM images, and element analysis. See DOI: 10.1039/c4nr05884d

Zhang, Guoliang; Qin, Lei; Wu, Yujiao; Xu, Zehai; Guo, Xinwen

2014-12-01

443

Solid-state properties of softwood lignin and cellulose isolated by a new acid precipitation method.  

PubMed

Solid-state and powder properties of softwood lignin and cellulose prepared by a new catalytic oxidation and acid precipitation method were characterized and compared with the commercial softwood and hardwood lignin and cellulose products. Catalytic pre-treated softwood lignin (CPSL) and cellulose (CPSC) were isolated from pine wood (Pinus sylvestris). CPSL with nearly micronized-scale particle size showed excellent powder flow and densification behavior due to the round shape and electrically minimum charged surface characteristics of particles. CPSL and the reference lignin studied were amorphous solids while CPSC exhibited a typical crystal lattice for cellulose I. In conclusion, physicochemical material properties of lignin and cellulose can be modified for biomedical and pharmaceutical applications with the present catalytic oxidation and acid precipitation method. PMID:22846687

Penkina, Anna; Hakola, Maija; Paaver, Urve; Vuorinen, Sirpa; Kirsimäe, Kalle; Kogermann, Karin; Veski, Peep; Yliruusi, Jouko; Repo, Timo; Heinämäki, Jyrki

2012-12-01

444

Catalytic synthesis of N-alkylacrylamide from acrylonitrile and alcohol with solid acids  

Microsoft Academic Search

Catalytic synthesis of N-alkylacrylamides, which are useful monomers for functional polymers, from acrylonitrile and alcohols, such as 1-adamantanol, tert-butyl alcohol, and isopropyl alcohol has been studied using various solid acids including heteropoly compounds and zeolites. For the reaction with 1-adamantanol or tert-butyl alcohol, a heteropoly compound, Cs2.5H0.5PW12O40, exhibited a high catalytic performance and water-tolerance. On the other hand, for the

Toshio Okuhara; Xin Chen; Hideho Matsuda

2000-01-01

445

Determination of Phenoxy Acid Herbicides in Drinking Waters by HPLC and Solid Phase Extraction  

Microsoft Academic Search

An HPLC procedure for determining phenoxy acid herbicides in waters is described. A LichroSpher RP select B octadecyl-silane analytical column and spectrophotometric detection at 230 nm were used. Adequate retention was achieved with a mobile phase containing MeOH\\/phosphate buffer 10 M pH 2.5\\/PnOH (50\\/42\\/8, v\\/v). The herbicides were isolated from water samples by using a single solid phase extraction procedure

J. M. Sanchis-Mallols; S. Sagrado; M. J. Medina-Hernández; R. M. Villanueva Camañas; E. Bonet-Domingo

1998-01-01

446

Cyclisation of citronellal over heterogeneous inorganic fluorides--highly chemo- and diastereoselective catalysts for (+/-)-isopulegol.  

PubMed

Based on a fluorolytic sol-gel synthesis, nanoscopic metal fluorides and partly hydroxylated metal fluorides were synthesized; varying the F : OH ratio inside these solids yielded catalysts with different combinations and variable strength Lewis and Brønsted acid sites, which demonstrated unexpected catalytic properties for the diastereoselective synthesis of (+/-)-isopulegol. PMID:19137185

Coman, Simona M; Patil, Pratap; Wuttke, Stefan; Kemnitz, Erhard

2009-01-28

447

Preparation of (Ga 1? x Zn x ) (N 1? x O x ) solid-solution from ZnGa 2O 4 and ZnO as a photo-catalyst for overall water splitting under visible light  

Microsoft Academic Search

A solid-solution of GaN and ZnO (Ga1?xZnx) (N1?xOx), as a visible-light-driven photo-catalyst for overall water splitting, is successfully prepared using both ZnGa2O4 and a ZnGa2O4–ZnO mixture. The photo-catalytic activity of the catalyst is found to be dependent on both the Zn\\/Ga ratio of the starting material and the nitridation time, because both factors affect the crystallinity and atomic composition of

Xiaojun Sun; Kazuhiko Maeda; Maël Le Faucheur; Kentaro Teramura; Kazunari Domen

2007-01-01

448

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.

Jalan, V.; Kosek, J.; Giner, J.; Taylor, E. J.; Anderson, E.; Bianchi, V.; Brooks, C.; Cahill, K.; Cropley, C.; Desai, M.; Frost, D.; Morriseau, B.; Paul, B.; Poirier, J.; Rousseau, M.; Swette, L.; Waterhouse, R.

1988-11-01

449

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

450

Phenylenediamine-based FeN(x)/C catalyst with high activity for oxygen reduction in acid medium and its active-site probing.  

PubMed

High-temperature pyrolyzed FeN(x)/C catalyst is one of the most promising nonprecious metal electrocatalysts for oxygen reduction reaction (ORR). However, it suffers from two challenging problems: insufficient ORR activity and unclear active site structure. Herein, we report a FeN(x)/C catalyst derived from poly-m-phenylenediamine (PmPDA-FeN(x)/C) that possesses high ORR activity (11.5 A g(-1) at 0.80 V vs RHE) and low H2O2 yield (<1%) in acid medium. The PmPDA-FeN(x)/C also exhibits high catalytic activity for both reduction and oxidation of H2O2. We further find that the ORR activity of PmPDA-FeN(x)/C is not sensitive to CO and NO(x) but can be suppressed significantly by halide ions (e.g., Cl(-), F(-), and Br(-)) and low valence state sulfur-containing species (e.g., SCN(-), SO2, and H2S). This result reveals that the active sites of the FeN(x)/C catalyst contains Fe element (mainly as Fe(III) at high potentials) in acid medium. PMID:25033100

Wang, Qiang; Zhou, Zhi-You; Lai, Yu-Jiao; You, Yong; Liu, Jian-Guo; Wu, Xia-Ling; Terefe, Ephrem; Chen, Chi; Song, Lin; Rauf, Muhammad; Tian, Na; Sun, Shi-Gang

2014-08-01

451

Synthesis of decapeptide of L-aspartic acid and benzyl-L-aspartic acid by solid phase peptide synthesis.  

PubMed

Polyene macrolide amphotericin B (AmB) is the drug of choice for the treatment of disseminated fungal infections. However, because of its pronounced side effects, the drug has limited applicability. There are few interesting reports, which state that co-administration of the drug with homo-peptide of polyaspartic acid reduces the side effects of the drug. In our present study, an approach has been made to systematically synthesize low molecular weight heteropeptides consisting of L-aspartic acid and its derivative. It was hypothesized that such heteropeptides will reduce the toxic side effects of the drug by facile hydrophobic binding between the polymer and the drug. We have employed the strategy of solid phase peptide synthesis (SPPS) to synthesize low molecular weight hetero-peptides by using L-aspartic acid and benzyl-L-aspartic acid to induce the hydrophobic binding between the peptide and the drug. In future, the proposed methodology can be employed to tailor other polypeptides substituted with benzyl groups to reduce the nephrotoxicity of AmB. PMID:16114487

Yoo, Bong K; Miah, M A Jalil; Lee, Eung-Seok; Han, Kun

2005-07-01

452

Anaerobic fermentation of organic solid wastes: volatile fatty acid production and separation.  

PubMed

Anaerobic fermentation of organic municipal solid waste was investigated using a leach-bed reactor (LBR) to assess the volatile fatty acid (VFA) production efficiency. The leachate recycle rate in the LBR affected the VFA composition of the leachate. A six-fold increase in the recycle rate resulted in an increase of the acetic acid fraction of leachate from 24.7 to 43.0%. The separation of VFAs via leachate replacement resulted in higher total VFA production. VFA separation from synthetic VFA mix and leachate of a fermented organic waste was assessed via a counter-current flow polytetrafluoroethylene (PTFE) membrane contactor. Acetic and propionic acid permeation fluxes of 13.12 and 14.21 g/m(2).h were obtained at low feed pH values when a synthetic VFA mix was used as a feed solution. The highest selectivity was obtained for caproic acid compared to that of other VFAs when synthetic VFA mix or leachate was used as a feed solution. High pH values and the presence of suspended solids in the leachate adversely affected the permeation rate. PMID:24845331

Yesil, H; Tugtas, A E; Bayrakdar, A; Calli, B

2014-01-01

453

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

454

EFFECTS OF LEWIS ACID CATALYSTS ON THE HYDROGENATION AND CRACKING OF TWO-RING AROMATIC AND HYDROAROMATIC STRUCTURES RELATED TO COAL  

SciTech Connect

An investigation was carried out of the hydrogenation and cracking of two-ring aromatic and hydroaromatic compounds catalyzed by ZnCl{sub 2} and AlCl{sub 3}. The rates of both processes are strongly affected by the Bronsted acidity of the active catalyst [e.g., H{sup +}(MX{sub n}Y){sup -}] and the Bronsted basicity of the aromatic portions of the reactant, the latter characteristic being enhanced by either methyl or hydroxyl substitution. The source of hydrogen used for hydrogenation depends on the choice of catalyst. In the presence of AlCl{sub 3}, Scholl condensation of aromatic nuclei serves as the principle source of hydrogen. Molecular hydrogen is used exclusively, though, when hydrogenation is catalyzed by ZnCl{sub 2}. The formation of reaction products and the trends in reactant reactivity are discussed on the basis of carbonium ion mechanisms.

Salim, Sadie S.; Bell, Alexis T.

1980-11-01

455

Iron oxide nanoparticles immobilized to mesoporous NH2-SiO2 spheres by sulfonic acid functionalization as highly efficient catalysts.  

PubMed

A novel SiO2 nanosphere was synthesized by the post-synthetic grafting of sulfonic acid groups on to anionic-surfactant-templated mesoporous NH2-silica (AMAS). This one-pot post-functionalization strategy allowed more metal ions to be homogeneously anchored into the channel of the meso-SiO2 nanosphere. After hydrothermal and calcination treatment, the in situ growth of ?-Fe2O3 on sulfonic acid-functionalized mesoporous NH2-SiO2 (SA-AMAS) exhibited much higher activity in the visible-light assisted Fenton reaction at neutral pH than that for AMAS or meso-SiO2 nanospheres. By analysis, the grafted sulfonic acid group can not only enhance the acid strength of the catalyst, but can also bring more orbital-overlapping between the active sites (Fe(II) and Fe(III)) and the surface peroxide species, to facilitate the decomposition of H2O2 to hydroxyl radical. The present results provide opportunities for developing heterogeneous catalysts with high-performance in the field of green chemistry and environmental remediation. PMID:25482204

Zhang, Guoliang; Qin, Lei; Wu, Yujiao; Xu, Zehai; Guo, Xinwen

2015-01-21

456

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

457

A Materials Approach to Site-Isolation of Grubbs Catalysts from Incompatible Solvents and m -Chloroperoxybenzoic Acid  

Microsoft Academic Search

The development of a method for site-isolation of Grubbs second-generation catalyst from MCPBA is described. In these reac- tions, Grubbs catalyst was dissolved in a solvent consisting of a mixture (1:1 v\\/v) of 1-butyl-3-methylimidazolium hexafluorophosphate and methylene chloride and completely encapsulated within a thimble fabricated from poly- dimethylsiloxane (PDMS). A series of molecules that react by cross metathe- sis or

2008-01-01

458

Applications of the hard-soft acid-base (HSAB) principle to solid adhesion and surface tribointeractions  

Microsoft Academic Search

We attempt to extend the Hard-Soft Acid-Base (HSAB) principle for the reactions in solutions to interactions in solids. First\\u000a we point out the important link between the absolute hardness of acid-and-base and the average energy gap. Then we discuss\\u000a the electronic band structures of various solids, e.g., metals, semimetals, semiconductors, and insulators. On the basis of\\u000a energy gaps, we elaborate

L. H. Lee

459

Characterization of Dispersed Heteropoly Acid on Mesoporous Zeolite Using Solid-State P-31 NMR Spin-Lattice Relaxation  

Microsoft Academic Search

Dispersion and quantitative characterization of supported catalysts is a grand challenge in catalytic science. In this paper, heteropoly acid H3PW12O40 (HPA) is dispersed on mesoporous zeolite silicalite-1 derived from hydrothermal synthesis using carbon black nanoparticle templates, and the catalytic activity is studied for 1-butene isomerization. The HPAs supported on conventional zeolite and on mesoporous zeolite exhibit very different activities and

Kake Zhu; Jian Z. Hu; Xiaoyan She; Jun Liu; Zimin Nie; Yong Wang; Charles HF Peden; Ja Hun Kwak

2009-01-01

460

Consumption of a Solid Fat Rich in Lauric Acid Results in a More Favorable Serum Lipid Profile in Healthy Men and Women than Consumption of a Solid Fat Rich in trans-Fatty Acids1  

Microsoft Academic Search

Solid fats are used in food manufacturing to provide texture and firmness to foods. Such fats are rich in either saturated or trans-fatty acids, both of which increase the risk of coronary heart disease. Epidemiological and experimental studies suggest that trans-fatty acids increase risk more than do saturates because they lower serum high density lipoprotein (HDL) cholesterol. However, there appear

Nicole M. de Roos; Evert G. Schouten; Martijn B. Katan