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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

Activation and reactivity of epoxides on solid acid catalysts  

Microsoft Academic Search

The aminolysis of epoxides over novel solid catalysts (Brönsted-acidic SBA-15 functionalized with propylsulfonic acid and Lewis-acidic Ti-MCM-41) is reported. The acidic properties of these catalysts were determined by FTIR spectroscopy and temperature-programmed desorption of pyridine and NH3, respectively. The mesoporous solid acids of the present study are reusable and exhibit significantly higher catalytic activities than known catalysts for opening of

L. Saikia; J. K. Satyarthi; D. Srinivas; P. Ratnasamy

2007-01-01

3

Hydrocracking with new solid acid catalysts: Model compounds studies  

SciTech Connect

Two new solid acid catalysts have been prepared by supporting zinc chloride on silica gel and acid-exchanged montmorillonite. The acid properties of these catalysts were determined by Hammett indicator method which showed that highly Bronsted acidic sites were present. SEM/EDS studies indicated a uniform distribution of silicon, zinc, and chlorine in the silica gel-zinc chloride catalyst. The activities of these catalysts in the hydrocracking of bibenzyl, polybenzyl, alkylbenzenes, and other heteroatom substituted aromatics were investigated. Their results with model compounds account for the effectiveness of these solid acid catalysts for conversion of coals to lower molecular weight materials.

Sharma, R.K.; Diehl, J.W.; Olson, E.S. (Univ. of North Dakota, Grand Forks (USA))

1990-01-01

4

Hydrocracking with new solid acid catalysts: Model compounds studies  

Microsoft Academic Search

Two new solid acid catalysts have been prepared by supporting zinc chloride on silica gel and acid-exchanged montmorillonite. The acid properties of these catalysts were determined by Hammett indicator method which showed that highly Bronsted acidic sites were present. SEM\\/EDS studies indicated a uniform distribution of silicon, zinc, and chlorine in the silica gel-zinc chloride catalyst. The activities of these

R. K. Sharma; J. W. Diehl; E. S. Olson

1990-01-01

5

Solid acid catalysts for biodiesel production - towards sustainable energy  

Microsoft Academic Search

The advantages of biodiesel as an alterna- tive fuel and the problems involved in its manufactur- ing are outlined. The pros and cons of making biodie- sel via fatty acid esterification using solid acid cata- lysts are examined. The main problem is finding a suitable catalyst that is active, selective, and stable un- der the process conditions. Various solid acids

Gadi Rothenberg

2006-01-01

6

Phosphorylated Mesoporous Carbon as a Solid Acid Catalyst  

SciTech Connect

Mesoporous carbon catalyst supports are attractive due to their wide chemical stability while potentially increasing masstransport through and providing a path for larger molecules to access catalytic sites. Herein we report the synthesis of a 10 phosphorylated mesoporous carbon solid-acid catalyst characterized by NH3-TPD and isopropanol dehydration.

Dai, Sheng [ORNL; Mayes, Richard T [ORNL; Fulvio, Pasquale F [ORNL; Ma, Zhen [ORNL

2011-01-01

7

Solid acid catalysts: Stain and shine  

NASA Astrophysics Data System (ADS)

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

Chen, Peng

2011-11-01

8

Hydrolysis of oligosaccharides over solid Acid catalysts: a review.  

PubMed

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

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

2014-04-01

9

Layered and nanosheet tantalum molybdate as strong solid acid catalysts  

Microsoft Academic Search

Layered and nanosheet aggregates of HTaMoO6 were examined as solid acid catalysts. The HTaMoO6 aggregated nanosheets were formed by soft chemical processing of layered HTaMoO6 using tetra (n-butylammonium) hydroxide. The catalytic activity and acid properties of the HTaMoO6 compounds were compared with those of layered HNbMoO6 and a range of conventional solid acids. The catalytic activity of HTaMoO6 for Friedel–Crafts

Caio Tagusagawa; Atsushi Takagaki; Kazuhiro Takanabe; Kohki Ebitani; Shigenobu Hayashi; Kazunari Domen

2010-01-01

10

Xanthan Sulfuric Acid: An Efficient and Recyclable Solid Acid Catalyst for Pechmann Condensation  

Microsoft Academic Search

In this report, substituted coumarins are formed via Pechmann condensation using various substituted phenols and ethyl acetoacetates in the presence of xanthan sulfuric acid as a solid acid catalyst under solvent-free conditions. This method is very simple, cost-effective, and has shorter reaction times, and the catalyst could be reused.

B. Suresh Kuarm; J. Venu Madhav; B. Rajitha

2012-01-01

11

Xanthan Sulfuric Acid: An Efficient and Recyclable Solid Acid Catalyst for Pechmann Condensation  

Microsoft Academic Search

In this paper, substituted coumarins are reported via Pechmann condensation by using various substituted phenols and ethyl acetoacetates in presence of Xanthan sulfuric acid as a solid acid catalyst under solvent-free conditions. This method is very simple, cost effective, shorter reaction times and the catalyst could be reused.

B. Suresh Kuarm; J. Venu Madhav; B. Rajitha

2011-01-01

12

Prompt gamma activation analysis of solid acid catalysts  

SciTech Connect

Zeolite molecular sieves are important catalysts due to their porous structures, which lead to the size-selective transport of chemical products and reactants. One potential application of the size-selective molecular adsorption properties of zeolites is in the purification of hydrofluorocarbons (HFCs), which are replacing ozone-destroying chlorofluorocarbons in a wide range of uses, e.g., as refrigerants. A first step in understanding adsorption of these HFC molecules by zeolites is obtaining accurate measurements of the number of adsorbate molecules per zeolite supercage. Another class of catalysts, solid superacids, is important for chemical reactions such as isomerization of hydrocarbons, conversion of methanol into hydrocarbons, and polymerization of alkenes. For example, ZrO{sub 2} and TiO{sub 2} have been observed to behave as solid superacids when small amounts of sulfate and hydrogen are incorporated on their surfaces. The acidity of these materials can exceed 104 times that of liquid H{sub 2}SO{sub 4}. One explanation for the {open_quotes}superacid{close_quotes} properties of these materials is that hydrogen ions (Bronstead acid sites) bound to surface oxygens are rendered more acidic by electron withdrawal due to nearby sulfate (SO{sub 4}{sup 2-}) groups. There is much 4 current interest in the synthesis and properties of solid super-acids because they may ultimately replace liquid acids such as H{sub 2}SO{sub 4}, HF, and AICl{sub 3} in industrially important syntheses and thereby reduce the waste streams generated. Characterization of solid acids requires measurements of the hydrogen and sulfate concentrations for correlation with the catalytic properties. We have utilized prompt gamma neutron activation analysis to characterize a number of these materials because of its unique ability to quantitatively measure hydrogen concentrations in addition to a number of other elements.

Crawford, M.K.; Corbin, D.R.; VerNooy, P.D. [DuPont, Wilmington, DE (United States)

1994-12-31

13

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

14

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

15

Determination of the acid strength of solid catalysts in water by means of a kinetic tracer  

Microsoft Academic Search

The kinetic analysis of the hydrolysis of acetals in the presence of various solid acid catalysts, dealuminated H-form mordenites, H-montmorillonite and strong ion exchange resins has been carried out. Experiments performed in water as the solvent at different agitation speeds, catalyst weights and acetal concentrations show that the reaction is not controlled by external diffusion, nor by internal diffusion as

Claude Moreau; Robert Durand; Patrick Geneste; Samir Mseddi

1996-01-01

16

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

17

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

18

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

19

Preparation and characterization of biomass carbon-based solid acid catalyst for the esterification of oleic acid with methanol.  

PubMed

A solid acid catalyst, prepared by sulfonating carbonized corn straw, was proved to be an efficient and environmental benign catalyst for the esterification of oleic acid and methanol. Various synthetic parameters, such as carbonization temperature and time were systematically examined. It was found that the catalyst exhibited the highest acid density of 2.64 mmol/g by NaOH titration. A quantitative yield (98%) of ester was achieved, using the most active sulfonated catalyst at 333 K with a 7 wt.% catalyst/oleic acid ratio for 4h, at a 7:1 M ratio of methanol/oleic acid, while the commercial available Amberlyst-15 only gave 85% yield under the same reaction condition. PMID:23453798

Liu, Tiantian; Li, Zhilong; Li, Wei; Shi, Congjiao; Wang, Yun

2013-04-01

20

Esterification reaction using solid heterogeneous acid catalysts under solvent-less condition  

Microsoft Academic Search

The preparation of di-2-ethylhexylphthalate (DOP) via esterification reaction of phthalic anhydride by 2-ethylhexanol in the presence of solid acidic catalysts has been investigated. The used catalysts were natural zeolite, synthetic zeolites (ZEOKAR-2, ASHNCH-3), heteropolyacid H4Si(W3O10)4 and sulfated ZrO2. The reactions were carried out under solvent-less conditions. It was observed that sulfated ZrO2 has higher reactivity and efficiency among the investigated

Firdovsi Tataroglu Sejidov; Yagoub Mansoori; Nadereh Goodarzi

2005-01-01

21

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

22

Preparation, characterization and catalytic activity of tin oxide-supported 12-tungstophosphoric acid as a solid catalyst  

Microsoft Academic Search

A series of solid acid catalysts were synthesized by incipient wetness impregnation method by varying the wt% of 12-tungstophosphoric acid (TPA) on tin oxide. The prepared catalysts were characterized by thermal analysis, XRD, FT-IR and BET surface area. The acidity of the catalyst was measured by different techniques. The suitability of the materials was studied for acid-catalyzed esterification reaction using

Abd El Rahman S. Khder

2008-01-01

23

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

PubMed

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

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

2012-08-01

24

Comparison between liquid and solid acids catalysts on reducing sugars conversion from furfural residues via pretreatments.  

PubMed

Liquid sulphuric acid is adopted and compared with carbon-based sulfonated solid acids (coal tar-based and active carbon-based) for furfural residues conversion into reducing sugars. The optimum hydrolysis conditions of liquid acid are at 4% of sulphuric acid, 25:1 of liquid and solid ratio, 175°C of reaction temperature and 120min of reaction time. The reducing sugar yields are reached over 60% on liquid acid via NaOH/H2O2, NaOH/microwave and NaOH/ultrasonic pretreatments, whereas only over 30% on solid acids. The TOFs (turnover number frequency) via NaOH/H2O2 pretreatments are 0.093, 0.020 and 0.023h(-1) for liquid sulphuric acid, coal tar-based and active carbon-based solid acids catalysts, respectively. Considering the efficiency, cost and environment factors, the liquid and solid acids have their own advantages of potential commercial application values. PMID:24976491

Lin, Keying; Ma, Baojun; Sun, Yuan; Liu, Wanyi

2014-09-01

25

Chemical mechanism of hydrocarbon cracking over solid acidic catalysts  

SciTech Connect

The article analyzes cracking reactions of isoalkanes and isoolefins over zeolite-based catalysts and discusses formation mechanisms of light reaction products under very mild conditions, at 150-250{degrees}C. Cracking patterns of 28 methyl- and ethyl-branched isoalkanes show that the compositions of light products can be described by an empirical rule: (1) the reaction site is formed at the tertiary carbon atom in an isoalkane molecule, (2) the predominant fission reaction involves the weakest C-C bond in the {alpha}-position to the reaction site, (3) the primary fission products are olefins. None of the cracking mechanisms described in the literature and involving reactions of carbonium and carbonium ions can adequately predict the observed product structures. A new cracking mechanism of isoalkanes which includes reactions between isoalkanes and Bronsted centers on the catalyst surface with the formation of transient hydrosiloxonium ions > Si-O{sup +} (H)-C< is proposed. The ions undergo the scission of the C-C bond in their alkyl groups in the {beta}-position of O{sup +} with the formation of olefin molecules (which rapidly isomerize) and smaller hydrosiloxonium ions. Comparison of cracked products from olefins and alkanes with the same skeletons and the same expected carbocations shows that the respective products are drastically different when they are formed under very mild conditions, i.e., that the cracking mechanisms of olefins and alkanes are also different. Studies of olefins with low oligomerization abilities (to prevent scrambling of the product structures) show that the olefin cracking can indeed be explained by fragmentation of carbenium ions via the {beta}-C-C bond scission mechanism. 40 refs., 2 figs., 12 tabs.

Kissin, Y.V. [Gulf Research and Development Co., Pittsburgh, PA (United States)] [Gulf Research and Development Co., Pittsburgh, PA (United States)

1996-09-15

26

ZnCl 2Zn 2+Montmorillonite composite: efficient solid acid catalyst for benzylation of benzene  

Microsoft Academic Search

A newer type of metal salt–metal ion exchanged Montmorillonite (Mont), MCl2-Mn+-Mont (M=Ni, Cu, Zn; n=2) have been prepared and evaluated as solid acid catalysts for Friedel–Crafts reactions particularly for benzylation of benzene. The activity of such composites depends upon the amount of loading of metal salts on the metal ion exchanged-Mont support and 1.5mmol loading per mole of the support

Anjali Phukan; Jatindra Nath Ganguli; Dipak Kumar Dutta

2003-01-01

27

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.

2011-01-01

28

Which controls the depolymerization of cellulose in ionic liquids: the solid acid catalyst or cellulose?  

PubMed

Cellulose is a renewable and widely available feedstock. It is a biopolymer that is typically found in wood, straw, grass, municipal solid waste, and crop residues. Its use as raw material for biofuel production opens up the possibility of sustainable biorefinery schemes that do not compete with food supply. Tapping into this feedstock for the production of biofuels and chemicals requires--as the first-step--its depolymerization or its hydrolysis into intermediates that are more susceptible to chemical and/or biological transformations. We have shown earlier that solid acids selectively catalyze the depolymerization of cellulose solubilized in 1-butyl-3-methylimidazolium chloride (BMIMCl) at 100 degrees C. Here, we address the factors responsible for the control of this reaction. Both cellulose and solid acid catalysts have distinct and important roles in the process. Describing the depolymerization of cellulose by the equivalent number of scissions occurring in the cellulosic chains allows a direct correlation between the product yields and the extent of the polymer breakdown. The effect of the acid strength on the depolymerization of cellulose is discussed in detail. Practical aspects of the reaction, concerning the homogeneous nature of the catalysis in spite of the use of a solid acid catalyst, are thoroughly addressed. The effect of impurities present in the imidazolium-based ionic liquids on the reaction performance, the suitability of different ionic liquids as solvents, and the recyclability of Amberlyst 15DRY and BMIMCl are also presented. PMID:20155777

Rinaldi, Roberto; Meine, Niklas; vom Stein, Julia; Palkovits, Regina; Schüth, Ferdi

2010-02-22

29

Butyric acid esterification kinetics over Amberlyst solid acid catalysts: the effect of alcohol carbon chain length.  

PubMed

The liquid phase esterification of butyric acid with a series of linear and branched alcohols is examined. Four strong cation exchange resins, Amberlyst™ 15, Amberlyst™ 36, Amberlyst™ BD 20, and Amberlyst™ 70, were used along with para-toluenesulfonic acid as a homogeneous catalyst. The effect of increasing alcohol carbon chain length and branching on esterification rate at 60°C is presented. For all catalysts, the decrease in turnover frequency (TOF) with increasing carbon chain length of the alcohol is described in terms of steric hindrance, alcohol polarity, and hydroxyl group concentration. The kinetics of butyric acid esterification with 2-ethylhexanol using Amberlyst™ 70 catalyst is described with an activity-based, pseudo-homogeneous kinetic model that includes autocatalysis by butyric acid. PMID:23380294

Pappu, Venkata K S; Kanyi, Victor; Santhanakrishnan, Arati; Lira, Carl T; Miller, Dennis J

2013-02-01

30

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

PubMed

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

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

2014-04-01

31

Zr mesoporous molecular sieves as novel solid acid catalysts in synthesizing nitrile and caprolactam.  

PubMed

Zr mesoporous materials with different Si/Zr ratio were synthesized by the surfactant-templated method involving cetyl trimethyl ammonium bromide (CTAB) as template and tetraethyl ortho silicate (TEOS) as organic source of silicon. The synthesized materials were labeled as SiZrMx (where x is Si/Zr = 10, 20 and 30). The BET analysis showed bimodal distribution of pores in SiZrMx structure. An attempt was made to generate super acidity on SiZrM20 by sulfation using sulfuric acid and ammonium sulfate (wt% = 4, 8 and 12). The NH3-TPD results revealed the presence of strong acidity in sulfated Zr-MCM-41. To understand the nature of acidity in Sulfated Zr-MCM-41, the efficiency of the materials is investigated in dehydration of Oximes. The industrially important materials caprolactam and intermediate nitrile were synthesized from their oximes in liquid phase system. Due to strong acidity in sulfated Zr-MCM-41, fast deactivation was observed during the synthesis of caprolactam but, the catalyst showed 96% nitrile selectivity. The strong acidity and medium strong acidity favoured the formation of nitrile and caprolactam respectively. This study revealed the molecular sieves were effective and eco-friendly solid acid catalysts for synthesizing caprolactam and nitrile. PMID:24734693

Nedumaran, D; Pandurangan, A

2014-04-01

32

Supported zirconium sulfate on carbon nanotubes as water-tolerant solid acid catalyst  

SciTech Connect

A new solid acid of zirconium sulfate (CZ) was successfully supported on carbon nanotube (CNT) for esterification reaction. Preparation conditions of the supported CZ have been investigated, to obtain highest catalytic activity for esterification reaction. XRD, TEM, BET, X-ray photoelectron spectra (XPS) and in situ FTIR analysis has also been carried out to understand the characteristics of the catalyst. In the esterification of acrylic acid with n-octanol, the supported CZ exhibited high catalytic activity and stability. The catalytic activity was nearly unchanged during four times of reuse. XRD and TEM analysis indicated that CZ was finely dispersed on CNT. XPS analysis shows that the CZ species was preserved and the chemical environment of the CZ has changed after loaded on CNT. This finding show that CNT as CZ support is an efficient water-tolerant solid acid.

Juan, Joon Ching [Institute of Modern Catalysis, Beijing University of Chemical Technology, State Key Laboratory of Chemical Resource Engineering, Ministry of Education, Beijing 100029 (China); Advanced Catalysis Technology Laboratory, School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Bangi 43600 (Malaysia); Jiang Yajie [Institute of Modern Catalysis, Beijing University of Chemical Technology, State Key Laboratory of Chemical Resource Engineering, Ministry of Education, Beijing 100029 (China); Meng Xiujuan [Institute of Modern Catalysis, Beijing University of Chemical Technology, State Key Laboratory of Chemical Resource Engineering, Ministry of Education, Beijing 100029 (China); Cao Weiliang [Institute of Modern Catalysis, Beijing University of Chemical Technology, State Key Laboratory of Chemical Resource Engineering, Ministry of Education, Beijing 100029 (China); Yarmo, Mohd Ambar [Advanced Catalysis Technology Laboratory, School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Bangi 43600 (Malaysia); Zhang Jingchang [Institute of Modern Catalysis, Beijing University of Chemical Technology, State Key Laboratory of Chemical Resource Engineering, Ministry of Education, Beijing 100029 (China)]. E-mail: zhangjc1@mail.buct.edu.cn

2007-07-03

33

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

34

Influence of solid acid catalyst on DME production directly from synthesis gas over the admixed catalyst of Cu\\/ZnO\\/Al 2O 3 and various SAPO catalysts  

Microsoft Academic Search

This study focused on the effect of solid acid catalyst on the catalytic performance in direct DME synthesis. The various SAPO catalysts were prepared to perform methanol dehydration and direct DME synthesis. In methanol dehydration, SAPO-34 and -18 with strong acid sites and showed high initial activity, but deactivated rapidly. This is mainly attributed to the formation of coking materials

Kye Sang Yoo; Ji-Hyun Kim; Min-Jo Park; Sun-Jin Kim; Oh-Shim Joo; Kwang-Deog Jung

2007-01-01

35

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

Microsoft Academic Search

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

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

2004-01-01

36

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

SciTech Connect

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

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

2013-01-01

37

Magnetic Solid Sulfonic Acid Decorated with Hydrophobic Regulators: A Combinatorial and Magnetically Separable Catalyst for the Synthesis of ?-Aminonitriles.  

PubMed

A three-component, Strecker reaction of a series of aldehydes or ketones, amines, and trimethylsilyl cyanide for the synthesis of ?-aminonitriles in the presence of a catalytic amount of a magnetic solid sulfonic acid catalyst, Fe3O4@SiO2@Me&Et-PhSO3H under solvent-free conditions have been investigated. This catalyst, with a combination of hydrophobicity and acidity on the Fe3O4@SiO2 core-shell of the magnetic nanobeads, as well as its water-resistant property, enabled easy mass transfer and catalytic activity in the Strecker reaction. The catalyst was easily separated by an external magnet and the recovered catalyst was reused in 6 successive reaction cycles without any significant loss of activity. PMID:24932543

Mobaraki, Akbar; Movassagh, Barahman; Karimi, Babak

2014-07-14

38

Degradation of polyethylene and polypropylene into fuel oil by using solid acid and non-acid catalysts  

Microsoft Academic Search

The thermal and catalytic degradation of plastic polymers, polyethylene (PE) at 430°C and polypropylene (PP) at 380°C into fuel oil were carried out by batch operation. The catalysts employed were acid-catalysts silica–alumina (SA-1, SA-2), zeolite ZSM-5 and non acidic mesoporous silica catalysts (silicalite, mesoporous silica gel and mesoporous folded silica (FSM). The yields of product gas, liquid and residues; recovery

Yusaku Sakata; Akinori Muto

1999-01-01

39

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

PubMed

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

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

2014-04-01

40

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

41

Solid acid catalysts from clays: preparation of mesoporous catalysts by chemical activation of metakaolin under acid conditions.  

PubMed

Natural kaolin was treated at 850 or 950 degrees C in air flow to give respectively the metakaolin samples MK8 and MK9. The obtained materials were successively treated at 90 degrees C with a 1 M solution of H(2)SO(4), for various time lengths. The acid treatment of MK8 was found to give a high surface area microporous material with good catalytic properties related to the high density of acid sites, while MK9 gave an ordered mesoporous material with a low density of acid sites. The materials were characterized by several techniques, X-ray powder diffraction, thermogravimetric analysis, N(2) physisorption, scanning electron microscopy, and temperature-programmed desorption of ammonia. The 1-butene isomerization was used as test reaction to evaluate the acidity of the samples. PMID:17451736

Lenarda, M; Storaro, L; Talon, A; Moretti, E; Riello, P

2007-07-15

42

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

PubMed

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

Safari, Javad; Zarnegar, Zohre

2013-03-01

43

Biodiesel production in a membrane reactor using MCM-41 supported solid acid catalyst.  

PubMed

Production of biodiesel from the transesterification between soybean oil and methanol was conducted in this study by a membrane reactor, in which ceramic membrane was packed with MCM-41 supported p-toluenesulfonic acid (PTSA). Box-Behnken design and response surface methodology (RSM) were used to investigate the effects of reaction temperature, catalyst amount and circulation velocity on the yield of biodiesel. A reduced cubic model was developed to navigate the design space. Reaction temperature was found to have most significant effect on the biodiesel yield while the interaction of catalyst amount and circulation velocity have minor effect on it. 80°C of reaction temperature, 0.27 g/cm(3) of catalyst amount and 4.15 mL/min of circulation velocity were proved to be the optimum conditions to achieve the highest biodiesel yield. PMID:24657760

Xu, Wei; Gao, Lijing; Wang, Songcheng; Xiao, Guomin

2014-05-01

44

Solid acid catalysts from clays: Preparation of mesoporous catalysts by chemical activation of metakaolin under acid conditions  

Microsoft Academic Search

Natural kaolin was treated at 850 or 950?°C in air flow to give respectively the metakaolin samples MK8 and MK9. The obtained materials were successively treated at 90?°C with a 1 M solution of H2SO4, for various time lengths. The acid treatment of MK8 was found to give a high surface area microporous material with good catalytic properties related to

M. Lenarda; L. Storaro; A. Talon; E. Moretti; P. Riello

2007-01-01

45

Ultrasound-assisted one-pot synthesis of substituted coumarins catalyzed by poly(4-vinylpyridinium) hydrogen sulfate as an efficient and reusable solid acid catalyst.  

PubMed

Poly(4-vinylpyridinium) hydrogen sulfate solid acid was found to be efficient catalyst for synthesis of substituted coumarins via Pechmann reaction using ultrasound irradiation at room temperature and neat condition in high yields with short reaction times. This methodology offers momentous improvements over various options for the synthesis of coumarins with regard to yield of products, simplicity in operation and green aspects by avoiding toxic catalysts and solvents. Further, the catalyst can be reused and recovered for several times. PMID:23395258

Khaligh, Nader Ghaffari

2013-07-01

46

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

47

Preparation of a carbon-based solid acid catalyst by sulfonating activated carbon in a chemical reduction process.  

PubMed

Sulfonated (SO(3)H-bearing) activated carbon (AC-SO(3)H) was synthesized by an aryl diazonium salt reduction process. The obtained material had a SO(3)H density of 0.64 mmol·g-1 and a specific surface area of 602 m2·g-1. The catalytic properties of AC-SO(3)H were compared with that of two commercial solid acid catalysts, Nafion NR50 and Amberlyst-15. In a 10-h esterification reaction of acetic acid with ethanol, the acid conversion with AC-SO(3)H (78%) was lower than that of Amberlyst-15 (86%), which could be attributed to the fact that the SO(3)H density of the sulfonated carbon was lower than that of Amberlyst-15 (4.60 mmol·g-1). However, AC-SO(3)H exhibited comparable and even much higher catalytic activities than the commercial catalysts in the esterification of aliphatic acids with longer carbon chains such as hexanoic acid and decanoic acid, which may be due to the large specific surface area and mesoporous structures of the activated carbon. The disadvantage of AC-SO(3)H is the leaching of SO(3)H group during the reactions. PMID:20956883

Liu, Xiao-Yan; Huang, Miao; Ma, Hai-Long; Zhang, Zeng-Qiang; Gao, Jin-Ming; Zhu, Yu-Lei; Han, Xiao-Jin; Guo, Xiang-Yun

2010-01-01

48

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

49

Solid phase synthesis of a diketopiperazine catalyst containing the unnatural amino acid ( S)-norarginine  

Microsoft Academic Search

A cyclic dipeptide containing the unnatural amino acid (S)-norarginine, recently shown to display useful catalytic activity, has been synthesized in good yield and high chemical purity using a solid phase protocol. All reactions in the sequence, including a Hofmann rearrangement and cyclization to diketopiperazine, were performed on the Merrifield polystyrene resin and proceed in high yield. In addition to its

Jennifer Kowalski; Mark A. Lipton

1996-01-01

50

Solid superacids as coal liquefaction catalysts  

Microsoft Academic Search

Direct coal liquefaction under mild conditions can be achieved by the use of strong acid catalysts. This research is aimed at exploring the possibility of mile coal liquefaction in the presence of solid superacids, especially oxides of iron, titanium, zirconium, and hafnium treated with sulfate ions. FeâOâ\\/SOâ²⁻ has been shown to be an impressively active catalyst in coal conversion at

J. W. Tierney; I. Wender

1989-01-01

51

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

Microsoft Academic Search

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

H Sato; K Nagai; H Yoshioka; Y Nagaoka

1999-01-01

52

Polypyrrole based strong acid catalyst for acetalization  

NASA Astrophysics Data System (ADS)

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

Liang, Xuezheng; Cheng, Yuxiao; Qi, Chenze

2011-09-01

53

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

54

Protic acid immobilized on solid support as an extremely efficient recyclable catalyst system for a direct and atom economical esterification of carboxylic acids with alcohols.  

PubMed

A convenient and clean procedure of esterification is reported by direct condensation of equimolar amounts of carboxylic acids with alcohols catalyzed by an easy to prepare catalyst system of perchloric acid immobilized on silica gel (HClO(4)-SiO(2)). The direct condensation of aryl, heteroaryl, styryl, aryl alkyl, alkyl, cycloalkyl, and long-chain aliphatic carboxylic acids with primary/secondary alkyl/cycloalkyl, allyl, propargyl, and long-chain aliphatic alcohols has been achieved to afford the corresponding esters in excellent yields. Chiral alcohol and N-t-Boc protected chiral amino acid also resulted in ester formation with the representative carboxylic acid or alcohol without competitive N-t-Boc deprotection and detrimental effect on the optical purity of the product demonstrating the mildness and chemoselectivity of the procedure. The esters of long-chain (>C(10)) acids and alcohols are obtained in high yields. The catalyst is recovered and recycled without significant loss of activity. The industrial application of the esterification process is demonstrated by the synthesis of prodrugs of ibuprofen and a few commercial flavoring agents. Other protic acids such as H(2)SO(4), HBr, TfOH, HBF(4), and TFA that were adsorbed on silica gel were less effective compared to HClO(4)-SiO(2) following the order HClO(4)-SiO(2) > H(2)SO(4)-SiO(2) > HBr-SiO(2) > TfOH-SiO(2) > HBF(4)-SiO(2) approximately TFA-SiO(2). When HClO(4) was immobilized on other solid supports the catalytic efficiency followed the order HClO(4)-SiO(2) > HClO(4)-K10 > HClO(4)-Al(2)O(3) (neutral) > HClO(4)-Al(2)O(3) (acidic) > HClO(4)-Al(2)O(3) (basic). PMID:19618958

Chakraborti, Asit K; Singh, Bavneet; Chankeshwara, Sunay V; Patel, Alpesh R

2009-08-21

55

Hydrocracking of polyolefins to liquid fuels over strong solid acid catalysts  

Microsoft Academic Search

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

K. R. Venkatesh; J. Hu; J. W. Tierney; I. Wender

1995-01-01

56

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

57

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

58

Solid Sulfonic Acid Catalysts Based on Porous Carbons and Carbon-Silica Composites  

NASA Astrophysics Data System (ADS)

Mesoporous carbons prepared using a templating method under different carbonization temperatures are sulfonated with concentrated H2SO4. Without the moving of silica template carbon-silica composites were prepared, which can maintain the pore structure well during sulfonation reaction process. The resultant samples are characterized using nitrogen adsorption, transmission electron microscope, field-emission scanning electron microscope, X-ray diffraction, X-ray photoelectron spectroscopy, and elemental analysis techniques. The catalytic performances of the sulfonated carbons and composites are evaluated by esterification reaction of methanol with acetic acid. The results show that a low-temperature carbonization process is favorable for improving the reaction conversion of acetic acid. In addition, the sulfonated carbon-silica composites show a higher acetic acid conversion than the sulfonated mesoporous carbons.

Tian, Xiao Ning; Luo, Lijuan; Jiang, Zhongqing; Zhao, X. S.

59

Isobutane alkylation with C 4 olefins on a sulfonic solid acid catalyst system based on laminar clays  

Microsoft Academic Search

Natural clays were modified by means of the controlled attack of strong Brönsted acids in aqueous solution. The variations of the surface acidity of the solids, followed by IR of adsorbed pyridine and hammett indicators, indicated a population of Brönsted type sites above 800?mol\\/g, while the surface area increased from 23 up to 105m2\\/g. A series of solids (ATZ-L, ATZ-A

C. E Ramos-Galván; J. M Dom??nguez; G Sandoval-Robles; A Mantilla; G Ferrat

2001-01-01

60

Predictive design of engineered multifunctional solid catalysts.  

PubMed

The ability to devise and design multifunctional active sites at the nanoscale, by drawing on the intricate ability of enzymes to evolve single-sites with distinctive catalytic function, has prompted complimentary and concordant developments in the field of catalyst design and in situ operando spectroscopy. Innovations in design-application approach have led to a more fundamental understanding of the nature of the active site and its mechanistic influence at a molecular level, that have enabled robust structure-property correlations to be established, which has facilitated the dextrous manipulation and predictive design of redox and solid-acid sites for industrially-significant, sustainable catalytic transformations. PMID:24682048

Raja, Robert; Potter, Matthew E; Newland, Stephanie H

2014-06-01

61

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

PubMed

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

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

2012-11-01

62

Silicotungstic acid supported zirconia: An effective catalyst for esterification reaction  

Microsoft Academic Search

A series of solid acid catalysts were synthesized by incipient wetness impregnation method by varying the wt% of silicotungstic acid on hydrous zirconia (ZSTA). The prepared catalysts were characterized by PXRD, FTIR, UV–vis DRS, EPMA, BET surface area, acid sites, etc. FTIR and UV–vis DRS studies indicate that the material retain the Keggin-type structure of silicotungstic acid up to 500°C.

K. M. Parida; Sujata Mallick

2007-01-01

63

Mesoporous H 3PW 12O 40-silica composite: Efficient and reusable solid acid catalyst for the synthesis of diphenolic acid from levulinic acid  

Microsoft Academic Search

Mesoporous H3PW12O40-silica composite catalysts with controllable H3PW12O40 loadings (4.0–65.1%) were prepared by a direct sol–gel–hydrothermal technique in the presence of triblock poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) copolymer. Powder X-ray diffraction (XRD) patterns and nitrogen sorption analysis indicate the formation of well-defined mesoporous materials. With H3PW12O40 loading lower than 20%, the materials exhibit larger BET surface area (604.5–753.0m2g?1), larger and well-distributed pore

Yihang Guo; Kexin Li; Xiaodan Yu; James H. Clark

2008-01-01

64

Evaluation of acidity of strong acid catalysts. 1. Derivation of an acidity function from carbon-13 NMR measurements  

Microsoft Academic Search

The limitations of the Hammett indicator method for acidity measurements of liquid acid catalysts of practical importance and the inapplicability in principle of the Hammett acidity concept to solid acid catalysts are discussed. Evaluation of acidities from the hydronation equilibrium of two simple alcohols, methanol and ethanol, and an α,β-unsaturated detone, 4-methyl-3-penten-2-one (mesityl oxide, I), by carbon-13 NMR is demonstrated

D. Farcasiu; A. Ghenciu; G. Miller

1992-01-01

65

Synthesis and structural study of N-acetyl-1,2,3,4-tetrahydroisoquinoline-2-sulfonamide obtained using H6P2W18O62 as acidic solid catalyst  

NASA Astrophysics Data System (ADS)

At room temperature and under acidic conditions, acylation of sulfamides derivatives in various solvents using diverse solid catalysts has been investigated. The best yields are obtained in acetonitrile with a Wells-Dawson type heteropolyacid H6P2W18O62 as acidic solid catalyst. Crystals of N-acetyl-1,2,3,4-tetrahydroisoquinoline-2-sulfonamide suitable for X-ray study have been obtained after recrystallization in toluene. The detailed analysis of molecular and crystal structure is presented in comparison with the structure of 1,2,3,4-tetrahydroisoquinoline-2-sulfonamide, before acylation, previously studied by our team. The role of both intra- and intermolecular weak interactions is discussed. The Hirshfeld surfaces analysis in form of dnorm representation and decomposed fingerprint plots were used to find out different weak but directional hydrogen bonds and ? interactions. Both structures present similar sandwich structures with alternation of primary layers involving strong hydrogen bonds with secondary layers involving mostly weaker interactions.

Bougheloum, Chafika; Barbey, Carole; Berredjem, Malika; Messalhi, Abdelrani; Dupont, Nathalie

2013-06-01

66

Sulfur and iron co-doped titanoniobate nanosheets: a novel efficient solid acid catalyst for alcoholysis of styrene epoxide at room temperature.  

PubMed

Sulfur and iron co-doped titanoniobate nanosheets were prepared and evaluated in alcoholysis of styrene epoxide. The resultant co-doped catalyst exhibited excellent catalytic performance (yield of 99% with methanol as the nucleophile in only 1 h at room temperature) and may act as a promising candidate in many acid-catalyzed reactions. PMID:23856976

Zhang, Lihong; Hu, Chenhui; Zhang, Junfeng; Cheng, Liyuan; Zhai, Zheng; Chen, Jing; Ding, Weiping; Hou, Wenhua

2013-09-01

67

Chemoselective Tetrahydropyranylation of Alcohols and Their Detetrahydropyranylation Using Silicasulphuric Acid as a Reusable Catalyst  

Microsoft Academic Search

A simple, mild, and efficient protocol for chemoselective protection of alcohols over phenols as tetrahydropyranyl ethers and their deprotection using silicasulphuric acid as a reusable solid acid catalyst is described.

D. M. Pore; Uday V. Desai; R. B. Mane; P. P. Wadgaonkar

2004-01-01

68

Solid Superacids as Coal Liquefaction Catalysts: Quarterly Report, January-March 1988.  

National Technical Information Service (NTIS)

This research is centered on the use of solid superacids as liquefaction catalysts. During this quarter, several metal oxide catalysts were synthesized. These include Fe sub 2 O sub 3 , ZrO sub 2 , and TiO sub 2 , each containing sulfate ions. Acidity mea...

J. W. Tierney I. Wender

1988-01-01

69

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

Microsoft Academic Search

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

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

2012-01-01

70

Calcium-based Lewis acid catalysts.  

PubMed

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

Begouin, Jeanne-Marie; Niggemann, Meike

2013-06-17

71

Catalysis by coke deposits: synthesis of isoprene over solid catalysts.  

PubMed

A help rather than a hindrance: Carbonaceous deposits have been found to play a key role in the selective synthesis of isoprene from formaldehyde and isobutene over solid catalysts. They accumulate on the catalyst surface during the induction period and promote the interaction of the substrates at the steady state. The proposed mechanism shows the way forward for the design of efficient solid catalysts for the synthesis of isoprene. PMID:24129943

Ivanova, Irina; Sushkevich, Vitaly L; Kolyagin, Yury G; Ordomsky, Vitaly V

2013-12-01

72

Sulfated titania [TiO 2\\/SO 4 2?]: A very active solid acid catalyst for the esterification of free fatty acids with ethanol  

Microsoft Academic Search

Sulfated titanias were prepared by using ammonium sulfate and sulfuric acid as sulfate precursors. Depending on the sulfation method, important effects on the acidity, textural properties as well as on activity were found. After ammonium sulfate was used, a large amount of SO linked to the titania surface was observed by FTIR spectroscopy. The acidity strength determined with Hammett indicators

J. L. Ropero-Vega; A. Aldana-Pérez; R. Gómez; M. E. Niño-Gómez

2010-01-01

73

9 A novel process for solid acid catalyzed isobutane\\/butene alkylation  

Microsoft Academic Search

The catalytic chemistry of a new process for alkylation of iso-butane with n-butene with zeolite based solid acid catalysts is described. The Brønsted acid site concentration in the zeolite catalysts is high, while the Lewis acid site concentration is low. The catalysts show high stability against deactivation by coking. In order to retard coking further and to extend the cstalyst

Andreas Feller; Alexander Guzman; Iker Zuazo; Johannes A. Lercher

2003-01-01

74

Catalysts for direct formic acid fuel cells  

NASA Astrophysics Data System (ADS)

Previous work has demonstrated that formic acid fuel cells show interesting properties for micro power generation. In this paper the effects of the anode catalyst composition on fuel cell performance is investigated. In particular, the performance of Pt, Pt/Pd and Pt/Ru catalysts for direct formic acid fuel cells is investigated and their effect on cell power density output at 30 °C are compared. It is found that the open cell potential varies significantly with the catalyst composition. The Pt/Pd catalyst shows an open cell potential of 0.91 V compared to 0.71 V with pure platinum and 0.59 V with Pt/Ru. The current at a cell potential of 0.5 V is 62 mA/cm 2 with Pt/Pd compared to 33 mA/cm 2 with pure platinum and 38 mA/cm 2 with Pt/Ru. Interestingly, the Pt/Ru catalyst gives the most power at low voltage 70 mW/cm 2 at 0.26 V, compared to 43 mW/cm 2 for pure platinum and 41 mW/cm 2 for Pt/Pd. All of the catalysts showed stable operation during several hour tests. Analysis of the data indicates that the addition of palladium enhances the rate of formic acid electrooxidation via a direct reaction mechanism, while ruthenium additions suppress the direct pathway and enhance electrooxidation via a reactive CO intermediate.

Rice, C.; Ha, S.; Masel, R. I.; Wieckowski, A.

75

Mechanism of neopentane cracking over solid acids  

Microsoft Academic Search

Neopentane was used as a probe to test whether catalyst protons can attack the C-C and\\/or the C-H sigma-bonds in the cracking of alkanes. Over a variety of solid acids approximately one CHâ molecule was formed for every neopentane reacted. Moreover, in most cases nearly as much isobutene was formed. With H-Y zeolite (H-Y) and particularly with H-mordenite (H-M), however,

E. A. Lombardo; R. Pierantozzi; W. K. Hall

1988-01-01

76

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

77

Polyamino Acids as Man-Made Catalysts  

Microsoft Academic Search

Polyamino acids are easy to prepare by nucleophile-initiated polymerisation of amino acid N-carboxyanhydrides. Polymers such as poly-(l)-leucine act as robust catalysts for the epoxidation of a wide range of electron-poor alkenes, such as ?-substituted ?,?-unsaturated ketones. The optically active epoxides so formed may be transformed into heterocyclic compounds, polyhydroxylated\\u000a materials and biologically active compounds such as diltiazem and taxol side

Joanne V. Allen; Stanley M. Roberts; Natalie M. Williamson

78

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

79

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

80

Tungstophosphoric and tungstosilicic acids on carbon as acidic catalysts  

Microsoft Academic Search

Tungstophosphoric (TPA) and tungstosilicic acid (TSA) catalysts supported on carbon were studied. They were prepared by equilibrium and incipient wetness impregnation techniques. Solutions of TPA and TSA in 50% v\\/v ethanol–water were used to impregnate carbon at 20°C. The Fourier transform infrared and 31P nuclear magnetic resonance spectroscopies of TPA and TSA supported catalysts dried at 70°C showed that the

Marcelo E Chimienti; Luis R Pizzio; Carmen V Cáceres; Mirta N Blanco

2001-01-01

81

Solid Electrolyte Potentiometry Aided Studies of Oxidic Catalysts  

Microsoft Academic Search

Solid electrolyte potentiometry (SEP) is a valuable tool in the investigation of catalytic gas–solid reactions as it is an in situ technique applicable under working conditions. It is commonly used in combined kinetic and electrochemical measurements and relates the steady state value of the oxygen activity at the catalyst to the observed reaction rates. After the description of principles and

Marvin Estenfelder; Thomas Hahn

2004-01-01

82

Differential thermal analysis as an acidity probe in zeolite catalysts  

SciTech Connect

Differential thermal analysis is used as an acidity strength probe for a series of mordenite (zeolite) catalysts via determining the temperature at which presorbed pyridine completely desorbs from the catalyst. The findings obtained for metal(s) containing mordenite catalysts have been correlated with the Pearson's assumption concerning Lewis acids and bases and the Pauling's electronegativity of the metals contained and found compatible.

Aboul-Gheit, A.K.; Al-Hajjaji, M.A.; Menoufy, M.F.; Abdel-Hamid, S.M.

1986-01-01

83

Chemisorption studies of promoted solid-state HDS catalysts  

Microsoft Academic Search

Oxygen pulse chemisorption measurements were made on a series of model HDS catalysts synthesized from solid-state reactions of elemental starting materials. Three different promoter atoms having the following catalyst stoichiometries were used in this study: P[sub 2x]Mo[sub 1[minus]x]S[sub 2] for the Co and Fe samples and P[sub x]Mo[sub 1[minus]x]S[sub 2] for the Ni series. Four samples from each promoter family

J. Lindner; A. Sachdev; J. Schwank; M. Villa-Garcia

1992-01-01

84

Catalyst Deactivation in Gas–Solid Photocatalysis  

Microsoft Academic Search

Photocatalyst lifetime is potentially important in process economics, as it sets maximum run times between catalyst regeneration or replacement. This note surveys the literature of photocatalytic air treatment and purification in order to identify the emerging photocatalyst deactivation issue. For each pertinent paper, the authors evaluate the total number of molecules converted by a photocatalyst over time and compare this

Michael L. Sauer; David F. Ollis

1996-01-01

85

Novel, benign, solid catalysts for the oxidation of hydrocarbons.  

PubMed

The catalytic properties of two classes of solid catalysts for the oxidation of hydrocarbons in the liquid phase are discussed: (i) microporous solids, encapsulating transition metal complexes in their cavities and (ii) titanosilicate molecular sieves. Copper acetate dimers encapsulated in molecular sieves Y, MCM-22 and VPI-5 use dioxygen to regioselectively ortho-hydroxylate L-tyrosine to L-dopa, phenol to catechol and cresols to the corresponding o-dihydroxy and o-quinone compounds. Monomeric copper phthalocyanine and salen complexes entrapped in zeolite-Y oxidize methane to methanol, toluene to cresols, naphthalene to naphthols, xylene to xylenols and phenol to diphenols. Trimeric mu3-oxo-bridged Co/Mn cluster complexes, encapsulated inside Y-zeolite, oxidize para-xylene, almost quantitatively, to terephthalic acid. In almost all cases, the intrinsic catalytic activity (turnover frequency) of the metal complex is enhanced very significantly, upon encapsulation in the porous solids. Spectroscopic and electrochemical studies suggest that the geometric distortions of the complex on encapsulation change the electron density at the metal ion site and its redox behaviour, thereby influencing its catalytic activity and selectivity in oxidation reactions. Titanosilicate molecular sieves can oxidize hydrocarbons using dioxygen when loaded with transition metals like Pd, Au or Ag. The structure of surface Ti ions and the type of oxo-Ti species generated on contact with oxidants depend on several factors including the method of zeolite synthesis, zeolite structure, solvent, temperature and oxidant. Although, similar oxo-Ti species are present on all the titanosilicates, their relative concentrations vary among different structures and determine the product selectivity. PMID:15901549

Ratnasamy, Paul; Raja, Robert; Srinivas, Darbha

2005-04-15

86

Calcined sodium silicate as solid base catalyst for biodiesel production  

Microsoft Academic Search

This paper examined the use of calcined sodium silicate as a novel solid base catalyst in the transesterification of soybean oil with methanol. The calcined sodium silicate was characterized by DTA-TG, Hammett indicator method, XRD, SEM, BET, IR and FT-IR. It catalyzed the transesterification of soybean oil to biodiesel with a yield of almost 100% under the following conditions: sodium

Feng Guo; Zhen-Gang Peng; Jian-Ying Dai; Zhi-Long Xiu

2010-01-01

87

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

88

Mechanistic studies of isopentane activation over solid acid catalysts. HD exchange with USY zeolite, amorphous silica-alumina and Amberlyst-15  

Microsoft Academic Search

The mechanism of activation of isopentane on USY zeolite, amorphous silica-alumina and Amberlyst-15 catalysts was studied by H-D exchange. Only the zeolite showed exchange with the isopentane at 373 K. The addition of 10% of 2-methyl-1-butene to the isopentane accelerates the exchange with USY zeolite and promotes a small exchange with amorphous silica-alumina and Amberlyst-15. Nevertheless, the selectivity was different.

Claudio J. A. Mota; Sonia C. Menezes; Leonardo Nogueira; W. Bruce Kover

1996-01-01

89

Liquefaction of solid carbonaceous material with catalyst recycle  

DOEpatents

In the two stage liquefaction of a carbonaceous solid such as coal wherein coal is liquefied in a first stage in the presence of a liquefaction solvent and the first stage effluent is hydrogenated in the presence of a supported hydrogenation catalyst in a second stage, catalyst which has been previously employed in the second stage and comminuted to a particle size distribution equivalent to 100% passing through U.S. 100 Mesh, is passed to the first stage to improve the overall operation.

Gupta, Avinash (Bloomfield, NJ); Greene, Marvin I. (Oradell, NJ)

1992-01-01

90

Effects of water on the esterification of free fatty acids by acid catalysts  

Microsoft Academic Search

To maximize the production of biodiesel from soybean soapstock, the effects of water on the esterification of high-FFA (free fatty acid) oils were investigated. Oleic acid and high acid acid oil (HAAO) were esterified by reaction with methanol in the presence of Amberlyst-15 as a heterogeneous catalyst or sulfuric acid as a homogeneous catalyst. The yield of fatty acid methyl

Ji-Yeon Park; Zhong-Ming Wang; Deog-Keun Kim; Jin-Suk Lee

2010-01-01

91

Solid acids for green chemistry.  

PubMed

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

Clark, James H

2002-09-01

92

Evaluation of acidity of strong acid catalysts. 1. Derivation of an acidity function from carbon-13 NMR measurements  

SciTech Connect

The limitations of the Hammett indicator method for acidity measurements of liquid acid catalysts of practical importance and the inapplicability in principle of the Hammett acidity concept to solid acid catalysts are discussed. Evaluation of acidities from the hydronation equilibrium of two simple alcohols, methanol and ethanol, and an {alpha},{beta}-unsaturated detone, 4-methyl-3-penten-2-one (mesityl oxide, I), by carbon-13 NMR is demonstrated for sulfuric acid-water mixtures. The latter compound is particularly useful because the signal for its carbon atom C-4 shifts downfield upon hydronation by almost 50 ppm, whereas the signal for C-3 moves upfield by 3 ppm. The comparison of the chemical shift difference {delta}(C-4)-{delta}(C-3) ({Delta}{delta}) for two different solutions allows a comparison of acidities of the two solutions from which other medium effects upon chemical shifts have been canceled out. The variation of {Delta}{delta} with concentration of I, or the ratio of base (I) to acid, is linear, at least between 1 and 0.5 M of I. Extrapolation of {Delta}{delta} of I to (B)/(AH) = 0 ({Delta}{delta}{sup 0}) allows the use of {sup 13}C NMR spectroscopy to establish a thermodynamically meaningful acidity scale, such as the traditional acidity function H{sub 0}. The slope of {Delta}{delta} vs (B)/(AH) plot changes with acid strength; it is lowest (most negative) for the acidity at which I is half-protonated. The acidity required for half-protonation can thus be accurately determined from this slope. On the other hand, {Delta}{delta} can be also measured at the stoichiometric ratio of the indicator base to acid molecules or sites. The latter approach must be used for comparison of strength of solid acids.

Farcasiu, D.; Ghenciu, A.; Miller, G. (Univ. of Pittsburgh, PA (United States))

1992-03-01

93

Biodiesel production from non-edible Silybum marianum oil using heterogeneous solid base catalyst under ultrasonication.  

PubMed

The aim of this study is to investigate modified TiO2 doped with C4H4O6HK as heterogeneous solid base catalyst for transesterification of non-edible, Silybum marianum oil to biodiesel using methanol under ultrasonication. Upon screening the catalytic performance of modified TiO2 doped with different K-compounds, 0.7 C4H4O6HK doped on TiO2 was selected. The preparation of the catalyst was done using incipient wetness impregnation method. Having doped modified TiO2 with C4H4O6HK, followed by impregnation, drying and calcination at 600°C for 6h, the catalyst was characterized by XRD, FTIR, SEM, BET, TGA, UV and the Hammett indicators. The yield of the biodiesel was proportional to the catalyst basicity. The catalyst had granular and porous structures with high basicity and superior performance. Combined conditions of 16:1 molar ratio of methanol to oil, 5 wt.% catalyst amount, 60°C reaction temperature and 30min reaction time was enough for maximum yield of 90.1%. The catalyst maintained sustained activity after five cycles of use. The oxidative stability which was the main problem of the biodiesel was improved from 2.0h to 3.2h after 30days using ascorbic acid as antioxidant. The other properties including the flash point, cetane number and the cold flow ones were however, comparable to international standards. The study indicated that Ti-0.7-600-6 is an efficient, economical and environmentally, friendly catalyst under ultrasonication for producing biodiesel from S. marianum oil with a substantial yield. PMID:24768105

Takase, Mohammed; Chen, Yao; Liu, Hongyang; Zhao, Ting; Yang, Liuqing; Wu, Xiangyang

2014-09-01

94

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

95

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

96

Preparation of mesoporous polyoxometalate–tantalum pentoxide composite catalyst for efficient esterification of fatty acid  

Microsoft Academic Search

Mesoporous polyoxometalate–tantalum pentoxide composite catalyst, H3PW12O40\\/Ta2O5, was prepared by a one-step sol–gel-hydrothermal method in the presence of triblock copolymer surfactant. Structure, morphology and surface textural property of the composite were characterized. As-prepared H3PW12O40\\/Ta2O5 was applied as a solid acid catalyst for esterification reaction of lauric acid with ethanol, an important pretreatment step in the production of biodiesel from renewable feedstocks.

Leilei Xu; Xia Yang; Xiaodan Yu; Yihang Guo; Maynurkader

2008-01-01

97

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 ...

98

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

99

Nanoporous solids as receptacles and catalysts for unusual conversions of organic compounds  

NASA Astrophysics Data System (ADS)

Solid-state chemical principles, allied to a degree of chemical intuition, enables one to design open-structure solids on to the inner surfaces of which isolated catalytically active sites of different kinds may be placed. With such solids, which act simultaneously both as permeable catalysts and reaction vessels, a number of highly desirable chemical conversions—many of paramount importance in the context of "green" chemistry and clean technology—may be smoothly effected under environmentally benign conditions. Typical examples, illustrated here, include the selective oxidation of toluene to benzaldehyde, current methods of producing alcohols, aldehydes and acids, and the synthesis of ?-caprolactam in a by-product-free manner. Such open-structure solids, which house single-site active centres, are also readily amenable to detailed and precise structural elucidation.

Raja, Robert; Thomas, John Meurig

2006-03-01

100

[sup 13]C solid-state NMR study of ethylene oxidation over supported silver catalysts  

SciTech Connect

Solid-state NMR has been used to study the interaction of ethylene with oxygen in the absence of promoters and moderators over silica-supported silver catalysts. Experiments using nitrous oxide and oxygen as the oxidants have been carried out over Ag/SiO[sub 2] catalyst at temperature ranging from 298 to 613 K. Standard cross-polarization with magic angle spinning (CP/MAS), CP/MAS with dipolar dephasing, and single-pulse experiments have been applied to identify carbon-containing species that are formed on the surface of catalyst at various temperatures. Ethylene, acetic acid, carbon dioxide, ethane and an alkoxy species have been identified. Under the above experimental conditions, no ethylene oxide is detected by NMR. In pursuit of a better understanding of the chemistry taking place on the catalyst, silica-supported silver catalysts as well as pure silica were dosed with labeled ethylene, carbon dioxide and ethylene oxide. It was found that under conditions employed in this study, ethylene oxide reacts with both metal and silica support and thus cannot be observed as the reaction product. Ethylene oxide, however, has been observed after the saturation of silica surface with unlabeled ethylene oxide prior to ethylene oxidation. In conjunction with this project, the author has designed and constructed a multiport high vacuum glass apparatus which was used for sample preparation prior to the NMR experiments as well as chemisorption measurements and a single-coil double resonance probe.

Hosseini, S.

1992-01-01

101

sup 13 C solid-state NMR study of ethylene oxidation over supported silver catalysts  

SciTech Connect

Solid-state NMR has been used to study the interaction of ethylene with oxygen in the absence of promoters and moderators over silica-supported silver catalysts. Experiments using nitrous oxide and oxygen as the oxidants have been carried out over Ag/SiO{sub 2} catalysts at temperature ranging from 298 to 613 K. Standard cross-polarization with magic angle spinning (CP/MAS), CP/MAS with dipolar dephasing, and single-pulse experiments have been applied to identify carbon containing species that are formed on the surface of catalyst at various temperatures. Ethylene, acetic acid, carbon dioxide, ethane and an alkoxy species have been identified. Under the above experimental conditions, no ethylene oxide is detected by NMR. In pursuit of a better understanding of the chemistry taking place on the catalyst, silica-supported silver catalysts as well as pure silica were dosed with labeled ethylene, carbon dioxide and ethylene oxide. It was found that under conditions employed in this study, ethylene oxide reacts with both metal and silica support and thus can not be observed as the reaction product. Ethylene oxide, however, has been observed after saturation of silica surface with unlabeled ethylene oxide prior to ethylene oxidation. A multiport high vacuum glass apparatus was developed along with a single-coil double resonance probe.

Hosseini, S.

1992-07-21

102

{sup 13}C solid-state NMR study of ethylene oxidation over supported silver catalysts  

SciTech Connect

Solid-state NMR has been used to study the interaction of ethylene with oxygen in the absence of promoters and moderators over silica-supported silver catalysts. Experiments using nitrous oxide and oxygen as the oxidants have been carried out over Ag/SiO{sub 2} catalysts at temperature ranging from 298 to 613 K. Standard cross-polarization with magic angle spinning (CP/MAS), CP/MAS with dipolar dephasing, and single-pulse experiments have been applied to identify carbon containing species that are formed on the surface of catalyst at various temperatures. Ethylene, acetic acid, carbon dioxide, ethane and an alkoxy species have been identified. Under the above experimental conditions, no ethylene oxide is detected by NMR. In pursuit of a better understanding of the chemistry taking place on the catalyst, silica-supported silver catalysts as well as pure silica were dosed with labeled ethylene, carbon dioxide and ethylene oxide. It was found that under conditions employed in this study, ethylene oxide reacts with both metal and silica support and thus can not be observed as the reaction product. Ethylene oxide, however, has been observed after saturation of silica surface with unlabeled ethylene oxide prior to ethylene oxidation. A multiport high vacuum glass apparatus was developed along with a single-coil double resonance probe.

Hosseini, S.

1992-07-21

103

Solid-state MAS NMR studies on the hydrothermal stability of the zeolite catalysts for residual oil selective catalytic cracking  

Microsoft Academic Search

By using the solid-state MAS NMR technique, the hydrothermal stabilities (under 100% steam at 1073 K) of HZSM-5 zeolites modified by lanthanum and phosphorus have been studied. They are excellent zeolite catalysts for residual oil selective catalytic cracking (RSCC) processes. It was indicated that the introduction of phosphorus to the zeolite via impregnation with orthophosphoric acid led to dealumination as

Jianqin Zhuang; Ding Ma; Gang Yang; Zhimin Yan; Xiumei Liu; Xianchun Liu; Xiuwen Han; Xinhe Bao; Peng Xie; Zhongmin Liu

2004-01-01

104

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  

Microsoft Academic Search

Sulfonic acid functionalized poly(ethylene glycol dimethacrylate-1-vinyl-1,2,4-triazole), poly(EGDMA-VTAZ-SO3H), is evaluated in the esterification of lactic acid with methanol. From nitrogen physisorption data, high surface area (220m2\\/g) and type II isotherm are obtained. Conversion measurements indicate a stronger interaction of poly(EGDMA-VTAZ-20%SO3H) with water molecules than that occurring in poly(EGDMA-VTAZ-10%SO3H). Hence, the higher catalytic activity of poly(EGDMA-VTAZ-10%SO3H) is related to the more hydrophobic

Beyhan Erdem; Ali Kara

105

In situ solid-state nuclear magnetic resonance studies of reactions in zeolite catalysts  

SciTech Connect

In situ solid-state NMR with magic-angle spinning (MAS) has been used to study reactions on zeolite catalysts. Several new experimental techniques have been developed that enable catalyst samples to be prepared for MAS NMR study without exposure to air or moisture. The design and use of a second-generation CAVERN apparatus that is easily fabricated from glass and other inexpensive materials is described. Two additional CAVERN appartuses that permit shallow bed adsorption of reactants are presented. One of the most successful routes to synthetic fuels in the conversion of methanol to gasoline (MTG) using zeolite catalyst HZSM-5. By using in situ MAS NMR, ethylene and methyl ethyl ether were identified as intermediates in the reaction. CO is neither a catalyst nor an intermediate. Trimethyloxonium, trimethylsulfonium, and trimethylselenonium ions formed on HZSM-5 by adsorption of the corresponding dimethyl chalcogenide. Unlike trialkyloxonium ions, trialkylsulfonium and trialkylselenonium ions were stable at high temperatures and in the presence of alcohols. Trialkylsulfonium and trialkylselenium ions poisoned the catalyst for MTG chemistry by quantitatively titrating the Bronsted acid sites. The chemistry of ethylene glycol, ethylene oxide, acetaldehyde, methyl formate, and acetic acid on zeolite catalysts HZSM-5 and CsHX was studied. Ethylene oxide and ethylene glycol formed 1,4-dioxane on HZSM-5. All compounds produced hydrocarbons and CO as products at high temperatures. In another study, [sup 13]C label exchange between the 1 and 3 positions of allyl alcohol at high temperatures on CsHX zeolite demonstrated formation of an allyl cation. Organic synthetic reactions in zeolites can be tuned to give different products in a predictable manner by coadsorption of other reagents.

Munson, E.J.

1993-01-01

106

Acid and base characteristics of molybdenum carbide catalysts  

Microsoft Academic Search

The acid and base properties of a high surface area Mo2C catalyst were characterized using the temperature programmed desorption of CO2 and NH3, the decomposition of isopropyl alcohol (IPA) as a test reaction and monitoring changes in the associated rates and product selectivities on the addition of acid and base site poisons. The Mo2C catalyst was prepared using the temperature

Shyamal K Bej; Christopher A Bennett; Levi T Thompson

2003-01-01

107

Manganese triazacyclononane oxidation catalysts grafted under reaction conditions on solid cocatalytic supports.  

PubMed

Manganese complexes of 1,4,7-trimethyl-1,4,7-triazacyclononane (tmtacn) are highly active and selective alkene oxidation catalysts with aqueous H(2)O(2). Here, carboxylic acid-functionalized SiO(2) simultaneously immobilizes and activates these complexes under oxidation reaction conditions. H(2)O(2) and the functionalized support are both necessary to transform the inactive [(tmtacn)Mn(IV)(?-O)(3)Mn(IV)(tmtacn)](2+) into the active, dicarboxylate-bridged [(tmtacn)Mn(III)(?-O)(?-RCOO)(2)Mn(III)(tmtacn)](2+). This transformation is assigned on the basis of comparison of diffuse reflectance UV-visible spectra to known soluble models, assignment of oxidation state by Mn K-edge X-ray absorption near-edge spectroscopy, the dependence of rates on the acid/Mn ratios, and comparison of the surface structures derived from density functional theory with extended X-ray absorption fine structure. Productivity in cis-cyclooctene oxidation to epoxide and cis-diol with 2-10 equiv of solid cocatalytic supports is superior to that obtained with analogous soluble valeric acid cocatalysts, which require 1000-fold excess to reach similar levels at comparable times. Cyclooctene oxidation rates are near first order in H(2)O(2) and near zero order in all other species, including H(2)O. These observations are consistent with a mechanism of substrate oxidation following rate-limiting H(2)O(2) activation on the hydrated, supported complex. This general mechanism and the observed alkene oxidation activation energy of 38 ± 6 kJ/mol are comparable to H(2)O(2) activation by related soluble catalysts. Undesired decomposition of H(2)O(2) is not a limiting factor for these solid catalysts, and as such, productivity remains high up to 25 °C and initial H(2)O(2) concentration of 0.5 M, increasing reactor throughput. These results show that immobilized carboxylic acids can be utilized and understood like traditional carboxylic acids to activate non-heme oxidation catalysts while enabling higher throughput and providing the separation and handling benefits of a solid catalyst. PMID:21970696

Schoenfeldt, Nicholas J; Ni, Zhenjuan; Korinda, Andrew W; Meyer, Randall J; Notestein, Justin M

2011-11-23

108

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

PubMed

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

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

2013-01-01

109

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.

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

2013-01-01

110

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

111

Solid-state NMR investigation of promoted silver catalysts  

SciTech Connect

The effects of cesium promoters on silver catalysts, supported by {gamma}-alumina, were studied by adsorbing mono- or dilabeled [{sup 13}C]ethylene onto the catalysts and performing low-temperature (70 K) solid-state {sup 13}C NMR measurements on the ethylene. Selective isotopic enrichment was used to investigate the electronic environment present in and around the ethylene molecule as a function of promoter concentration. Changes in the spectroscopic parameters describing the ethylene lineshapes were extracted using a nonlinear least-squares procedure. These parameters were then used to determine the structure of the ethylene molecule on the surface and to probe the changes induced by adding cesium promoters. Similarly, the state of cesium in the catalyst system was investigated by spin-echo double-resonance spectroscopy and scanning electron microscopy X-ray fluorescence methods. The results imply that the form of cesium is not that of an oxide but, in all probability, reflect those of a cation-anion pair.

Hughes, E.; Koons, J.M.; Wang, J. [Univ. of South Carolina, Columbia, SC (United States). Dept. of Chemistry and Biochemistry] [Univ. of South Carolina, Columbia, SC (United States). Dept. of Chemistry and Biochemistry; Ellis, P.D. [Pacific Northwest National Lab., Richland, WA (United States). Environmental Molecular Sciences Lab.] [Pacific Northwest National Lab., Richland, WA (United States). Environmental Molecular Sciences Lab.

1999-04-25

112

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

113

Silica tungstic acid as an efficient and reusable catalyst for the one-pot synthesis of 2-amino-4H-chromene derivatives.  

PubMed

Silica tungstic acid (STA) has been found to be an efficient and reusable solid acid catalyst for the synthesis of 2-amino-4H-chromenes via the three-component reaction of aromatic aldehydes, malononitrile, and ?-naphthol. STA as a novel solid acid was characterized by X-ray fluorescence, X-ray diffraction, and Fourier transform infrared spectroscopy. PMID:24664332

Farahi, Mahnaz; Karami, Bahador; Alipour, Samambar; Moghadam, Leila Taghavi

2014-01-01

114

Continuous mode linoleic acid hydrogenation on Pd\\/sibunit catalyst  

Microsoft Academic Search

Catalytic hydrogenation of linoleic acid and oleic acid to stearic acid over palladium on mesoporous carbon sibunit (Pd\\/sibunit)\\u000a catalyst was studied in a continuous trickle-bed reactor with the weight hourly space velocity 5.4 h?1 at 120°C and 30 bar using tall oil fatty acid (TOFA) as reactor feed. Stearic acid preparation using TOFA as a raw material\\u000a is of industrial

A. Bernas; I. L. Simakova; K. Eränen; J. Myllyoja; T. Salmi; D. Yu. Murzin

2010-01-01

115

Enantioselective Iodolactonization of Disubstituted Olefinic Acids Using a Bifunctional Catalyst  

PubMed Central

The enantioselective iodolactonizations of a series of diversely-substituted olefinic carboxylic acids are promoted by a BINOL-derived, bifunctional catalyst. Reactions involving 5-alkyl- and 5-aryl-4(Z)-pentenoic acids and 6-alkyl- and 6-aryl-5(Z)-hexenoic acids provide the corresponding ?- and ?-lactones having stereogenic C–I bonds in excellent yields and >97:3 er. Significantly, this represents the first organocatalyst that promotes both bromo- and iodolactonization with high enantioselectivities. The potential of this catalyst to induce kinetic resolutions of racemic unsaturated acids is also demonstrated.

Fang, Chao; Paull, Daniel H.; Hethcox, J. Caleb; Shugrue, Christopher R.; Martin, Stephen F.

2012-01-01

116

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

117

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

118

Preparation, characterization and application of heterogeneous solid base catalyst for biodiesel production from soybean oil  

Microsoft Academic Search

A solid base catalyst was prepared by neodymium oxide loaded with potassium hydroxide and investigated for transesterification of soybean oil with methanol to biodiesel. After loading KOH of 30 wt.% on neodymium oxide followed by calcination at 600 °C, the catalyst gave the highest basicity and the best catalytic activity for this reaction. The obtained catalyst was characterized by means of X-ray

Yihuai Li; Fengxian Qiu; Dongya Yang; Xiaohua Li; Ping Sun

2011-01-01

119

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

SciTech Connect

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

Hendriksen, D.E.

1983-01-01

120

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

PubMed

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

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

2012-01-23

121

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

PubMed

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

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

2014-04-01

122

Structured catalysts for photo-Fenton oxidation of acetic acid  

Microsoft Academic Search

In this work photo-Fenton oxidation of acetic acid, was carried out on perovskites based structured catalysts, in the presence or in the absence of low amounts of Pt. Homogeneous photo-Fenton reaction by ferrioxalate complex has been also performed. The comparison of homogeneous and heterogeneous photo-Fenton oxidation indicates that the use of a heterogeneous structured catalyst greatly improves the total organic

Diana Sannino; Vincenzo Vaiano; Paolo Ciambelli; Lyubov A. Isupova

2011-01-01

123

Effect of water on silica-supported phosphotungstic acid catalysts for 1-butene double bond shift and alkane skeletal isomerization  

Microsoft Academic Search

The thermal stability, acidity, catalytic activity and regenerability of silica-supported phosphotungstic acid were evaluated in reference to the bulk solid acid. Samples were prepared with 5, 10, and 25wt.% heteropolyacid (HPA) on fumed silica to examine the effect of loading on the properties of supported acid catalysts. X-ray absorption spectroscopy indicated that the supported heteropolyacids did not completely decompose when

Billy B Bardin; Robert J Davis

2000-01-01

124

Green chemistry: Biodiesel made with sugar catalyst  

NASA Astrophysics Data System (ADS)

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

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

2005-11-01

125

Green chemistry: biodiesel made with sugar catalyst.  

PubMed

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

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

2005-11-10

126

A One-Bead-One-Catalyst Approach to Aspartic Acid-Based Oxidation Catalyst Discovery  

PubMed Central

We report an approach to the high-throughput screening of asymmetric oxidation catalysts. The strategy is based on application of the one-bead-one-compound library approach, wherein each of our catalyst candidates is based on a peptide scaffold. For this purpose we rely on a recently developed catalytic cycle that employs an acid-peracid shuttle. In order to implement our approach, we developed a compatible linker and demonstrated that the library format is amenable to screening and sequencing of catalysts employing partial Edman degradation and MALDI mass spectrometry analysis. The system was applied to the discovery (and re-discovery) of catalysts for the enantioselective oxidation of a cyclohexene derivative. The system is now poised for application to unprecedented substrate classes for asymmetric oxidation reactions.

Lichtor, Phillip A.; Miller, Scott J.

2011-01-01

127

Evaluation of catalyst acidity and substrate electronic effects in a hydrogen bond-catalyzed enantioselective reaction.  

PubMed

A modular catalyst structure was applied to evaluate the effects of catalyst acidity in a hydrogen bond-catalyzed hetero Diels-Alder reaction. Linear free energy relationships between catalyst acidity and both rate and enantioselectivity were observed, where greater catalyst acidity leads to increased activity and enantioselectivity. A relationship between reactant electronic nature and rate was also observed, although there is no such correlation to enantioselectivity, indicating the system is under catalyst control. PMID:20919686

Jensen, Katrina H; Sigman, Matthew S

2010-11-01

128

Organometallic catalysts for primary phosphoric acid fuel cells  

NASA Technical Reports Server (NTRS)

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

Walsh, Fraser

1987-01-01

129

Transition metal sulfide hydrogen evolution catalysts for hydrobromic acid electrolysis.  

PubMed

Mixed metal sulfides containing combinations of W, Fe, Mo, Ni, and Ru were synthesized and screened for activity and stability for the hydrogen evolution reaction (HER) in aqueous hydrobromic acid (HBr). Co- and Ni-substituted RuS(2) were identified as potentially active HER electrocatalysts by high-throughput screening (HTS), and the specific compositions Co(0.4)Ru(0.6)S(2) and Ni(0.6)Ru(0.4)S(2) were identified by optimization. Hydrogen evolution activity of Co(0.4)Ru(0.6)S(2) in HBr is greater than RuS(2) or CoS(2) and comparable to Pt and commercial Rh(x)S(y). Structural and morphological characterizations of the Co-substituted RuS(2) suggest that the nanoparticulate solids are a homogeneous solid solution with a pyrite crystal structure. No phase separation is detected for Co substitutions below 30% by X-ray diffraction. In 0.5 M HBr electrolyte, the Co-Ru electrode material synthesized with 30% Co rapidly lost approximately 34% of the initial loading of Co; thereafter, it was observed to exhibit stable activity for HER with no further loss of Co. Density functional theory calculations indicate that the S(2)(2-) sites are the most important for HER and the presence of Co influences the S(2)(2-) sites such that the hydrogen binding energy at sufficiently high hydrogen coverage is decreased compared to ruthenium sulfide. Although showing high HER activity in a flow cell, the reverse reaction of hydrogen oxidation is slow on the RuS(2) catalysts tested when compared to platinum and rhodium sulfide, leaving rhodium sulfide as the only suitable tested material for a regenerative HBr cell due its stability compared to platinum. PMID:23205859

Ivanovskaya, Anna; Singh, Nirala; Liu, Ru-Fen; Kreutzer, Haley; Baltrusaitis, Jonas; Nguyen, Trung Van; Metiu, Horia; McFarland, Eric

2013-01-01

130

Dispersion and activity of molybdena-alumina catalysts prepared by impregnation and solid\\/solid wetting methods  

Microsoft Academic Search

Alumina-supported molybdena catalysts were prepared by both the standard incipient wetness method and by mixing MoOâ and AlâOâ (solid\\/solid wetting), followed by thermal treatment of 500 C under dry or wet Oâ atmospheric conditions. These catalysts were characterized by means of Oâ chemisorption at -78 C, COâ uptake at ambient temperature, X-ray diffraction (XRD), and electron spin resonance (ESR) techniques.

B. M. Reddy; E. P. Reddy; S. T. Srinivas

1992-01-01

131

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

SciTech Connect

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

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

2011-04-15

132

Sorption of Humic Acids onto Aquifer Solids.  

National Technical Information Service (NTIS)

A study was made of the sorption of commercial Aldrich humic acid and IHSS Suwannee River humic acid onto three natural aquifer material solids from Barksdale AFB, Louisiana; Blytheville AFB, Arkansas and Columbus AFB, Mississippi. The interactions follow...

M. J. Plana

1997-01-01

133

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

PubMed

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

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

2013-01-01

134

Conjugate addition of methanol to 3-buten-2-one over solid base catalysts  

Microsoft Academic Search

Conjugate addition of methanol to 3-buten-2-one to form 4-methoxy-butan-2-one proceeds effectively over the solid base catalysts such as alkaline earth oxides, strontium hydroxide, barium hydroxide, and alumina supported potassium fluoride and hydroxide at a reaction temperature of 273K. The catalytic activities of magnesium oxide, calcium oxide, and alumina supported KF catalyst were not much affected by exposure of the catalysts

Hajime Kabashima; Tomokazu Katou; Hideshi Hattori

2001-01-01

135

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

PubMed

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

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

2013-11-01

136

Solid-phase extraction of acidic herbicides.  

PubMed

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

Wells, M J; Yu, L Z

2000-07-14

137

A designed organic–zeolite hybrid acid–base catalyst  

Microsoft Academic Search

An organic–zeolite hybrid catalyst was synthesised via solid-state impregnation of the zeolite with an amount of melamine corresponding to 20mol% of the aluminium content. A high density of basic sites is formed in the zeolite. From infrared spectroscopy and TGA measurements we infer that melaminium cations are formed in the zeolite which are highly thermally stable. IR spectroscopic and TGA

Andrew C. Brooks; Liam France; Cecile Gayot; Jerry Pui Ho Li; Ryan Sault; Andrew Stafford; John D. Wallis; Michael Stockenhuber

138

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

Microsoft Academic Search

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

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

2001-01-01

139

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.

140

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

141

Chemical recycling of waste polystyrene into styrene over solid acids and bases  

SciTech Connect

Catalytic degradation of waste polystyrene into styrene was studied using solid acids and bases as catalysts. Partially because of the high yield of distillates from polystyrene and partially because of the high selectivity into styrene in the distillates, solid bases were emphasized to be effective catalysts for the chemical recycling of waste polystyrene. Since there were significant differences in the compositions of distillates yielded on solid acids and bases, degradation mechanisms to styrene and other products on these materials were also briefly discussed. Finally, in order to make a design for disassembly of waste polystyrene into styrene, barium oxide powders, the most effective catalyst for the chemical recycling of waste polystyrene, were dispersed into polystyrene pieces when molded into thin films. Thermal degradation of these films in styrene was successfully carried out without the assistance of any other catalytic compounds.

Zhang, Z.; Hirose, Tamaki; Nishio, Suehiro; Morioka, Yoshio; Azuma, Naoto; Ueno, Akifumi [Shizuoka Univ., Hamamatsu, Shizuoka (Japan); Ohkita, Hironobu [Toyohashi Univ. of Technology, Aichi (Japan); Okada, Mitsunori [Furukawa Electric Co., Ltd., Yokohama, Kanagawa (Japan)

1995-12-01

142

Ultrasonic-assisted transesterification of Jatropha curcus oil using solid catalyst, Na/SiO2.  

PubMed

The production of biodiesel from non-edible vegetable oil using ultrasonication, calls for an efficient solid catalyst to make the process fully ecologically and economically friendly. The methodology allows for the reaction to be run under atmospheric conditions. Solid catalyst and ultrasonication reduced the reaction time comparing to the conventional batch processes and we found 98.53% biodiesel yield. The optimal conditions for biodiesel production is the molar ratio oil to methanol 1:9, Catalyst conc. 3 wt.% of oil and 15 min reaction time. PMID:20359932

Kumar, Dharmendra; Kumar, Gajendra; Poonam; Singh, C P

2010-06-01

143

Kinetics of germanium nanowire growth by the vapor-solid-solid mechanism with a Ni-based catalyst  

NASA Astrophysics Data System (ADS)

The kinetics of vapor-solid-solid (VSS) Ge nanowire growth using a Ni-based catalyst were investigated to probe the rate-limiting step for this complex nanoscale crystal growth process. The effects of key parameters such as temperature and precursor partial pressure on the nanowire growth rate were studied in order to gain detailed insights into the growth kinetics. Two different regimes were observed for VSS growth of Ge nanowires as function of temperature. At higher temperatures (345 °C-375 °C), kinetics data suggest that mass transport of germane precursor to the catalyst surface is rate limiting. At lower temperatures (<345 °C), either surface reaction of the GeH4 precursor on the catalyst or incorporation of Ge into the nanowire across the wire/catalyst interface is rate limiting.

Thombare, Shruti V.; Marshall, Ann F.; McIntyre, Paul C.

2013-12-01

144

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

145

Enhanced life of proton exchange membrane fuel cell catalysts using perfluorosulfonic acid stabilized carbon support  

Microsoft Academic Search

We report a new and simple solution to increase life of Pt\\/C catalysts using the proton-conducting polymer (perfluorosulfonic acid, PFSA) stabilized carbon support (denoted these catalysts as Pt\\/NFC catalysts) as compared to conventional Pt\\/C catalysts commonly used in PEM fuel cells. A high catalytic activity of the catalyst is observed by both CV (cyclic voltammetry) and ORR (oxygen reduction reaction)

Niancai Cheng; Shichun Mu; Xiaojing Chen; Haifeng Lv; Mu Pan; Peter P. Edwards

2011-01-01

146

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

147

PaaSiCats: novel polyamino acid catalysts.  

PubMed

The abilities of five polyamino acids (Paa's) to catalyse the asymmetric epoxidation of enones 1-7 under three sets of reaction conditions were compared: polyneo-pentylglycine and polyleucine showed distinct advantages in most circumstances. All five polymers were adsorbed onto silica and from this further study, immobilised polyneo-pentylglycine (PLNSi) and polyleucine (PLLSi) were shown to be the catalysts of choice for the asymmetric epoxidation of less-reactive alpha,beta-unsaturated ketones. PMID:10824145

Dhanda, A; Drauz, K H; Geller, T; Roberts, S M

2000-06-01

148

Catalytic cracking process employing an acid-reacted metakaolin catalyst  

SciTech Connect

This patent describes a method for cracking hydrocarbons. It comprises: reacting a hydrocarbon feedstock under catalytic cracking conditions with a catalyst which comprises an acid reacted metakaolin composition having a mole composition of about 0.8 to 1.0 Al{sub 2}O{sub 3}.2 SiO{sub 2} and characterized by a surface area of above bout 150 m{sup 2}/g.

Lussier, R.J.

1990-07-10

149

Cu Cr O nanocomposites: Synthesis and characterization as catalysts for solid state propellants  

NASA Astrophysics Data System (ADS)

In this article we present the synthesis of Cu-Cr-O nanocomposites via a citric acid (CA) complexing approach and the evaluation of the as-synthesized Cu-Cr-O nanocomposites as additives for the catalytic combustion of AP (ammonium perchlorate)-based solid state propellants. Techniques of thermo-gravimetric/differential thermal analyzer (TG-DTA), X-ray diffraction (XRD), transmission electron microscopy (TEM) as well as scanning electron microscopy (SEM) have been employed to characterize the thermal decomposition procedure, crystal phase, micro-structural morphologies and grain size of the as-synthesized materials, respectively. The results show that well-crystallized Cu-Cr-O nanocomposites can be produced by using a temperature as low as 600 °C. Phase structure of the as-obtained Cu-Cr-O nanocomposites depends on the Cu/Cr molar ratio in the starting reactants. Addition of the as-synthesized Cu-Cr-O nanocomposites as catalysts enhances the burning rate as well as lowers the pressure exponent of the AP-based solid state propellants considerably. Noticeably, solid state propellants containing Cu-Cr-O nanocomposites with a Cu/Cr molar ratio of 0.7 exhibits the most stable combustion at all pressures.

Li, Wei; Cheng, Hua

2007-08-01

150

Determination of the basic strength of solid catalysts in water by means of a kinetic tracer  

Microsoft Academic Search

The kinetic analysis of the isomerization of glucose into fructose in the presence of solid basic catalysts, cation-exchanged zeolites and anion-modified hydrotalcites, has been performed in order to evaluate the basicity of those solids in water as the solvent and under working reaction conditions. A standardization curve is established by plotting the logarithms of the rate constants of isomerization of

Claude Moreau; Jérôme Lecomte; Alain Roux

2006-01-01

151

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

152

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

153

PROPIEDADES ACIDAS DE LOS CATALIZADORES DE Pt-Sn\\/Al2O3 PREPARADOS POR SOL-GEL ACIDIC PROPERTIES OF Pt-Sn\\/Al2O3 SOL-GEL PREPARED CATALYSTS  

Microsoft Academic Search

The acid properties in sol-gel catalysts were studied. Tin-alumina catalysts were prepared by cogeltion of aluminium tri-sec-butoxide and tetra-butyltin, tetra-ter-amil-oxide tin or tin tetrachloride. Aqueous platinum solutions were used for impregnation. The results shown that the specific surface area and the acidity of the catalysts were only alightly modified by the metal precursors used. The solids prepared with tetrabutyltin showed

R. Silva-Rodrigo; T. López-Goerne; V. Bertin-Mardel; R. Gómez-Romero

2005-01-01

154

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

SciTech Connect

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

Not Available

1993-01-01

155

BINARY MgO-BASED SOLID SOLUTION CATALYSTS FOR METHANE CONVERSION TO SYNGAS  

Microsoft Academic Search

The excellent catalytic performance and high stability of MgO–NiO solid solution catalysts in CH4 conversion to syngas generated the recent outburst of interest for the binary MgO-based solid solutions. This review will focus on the relationship between the catalytic performance of the binary MgO-based solid solution and its properties in the CO2 reforming, the partial oxidation and the steam reforming

Yun Hang Hu; Eli Ruckenstein

2002-01-01

156

NMR-spectroscopic evidence of intermediate-dependent pathways for acetic acid formation from methane and carbon monoxide over a ZnZSM-5 zeolite catalyst.  

PubMed

Two ways: a Zn-modified ZSM-5 zeolite catalyst was developed for the reaction of methane with carbon monoxide to directly produce acetic acid under mild conditions (573-623 K), and two different intermediate-dependent reaction pathways were unambiguously identified for acetic acid formation by in situ solid-state NMR spectroscopy. PMID:22389151

Wang, Xiumei; Qi, Guodong; Xu, Jun; Li, Bojie; Wang, Chao; Deng, Feng

2012-04-16

157

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

158

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

159

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

160

sup 13 C solid-state NMR study of ethylene oxidation over supported silver catalysts  

Microsoft Academic Search

Solid-state NMR has been used to study the interaction of ethylene with oxygen in the absence of promoters and moderators over silica-supported silver catalysts. Experiments using nitrous oxide and oxygen as the oxidants have been carried out over Ag\\/SiOâ catalysts at temperature ranging from 298 to 613 K. Standard cross-polarization with magic angle spinning (CP\\/MAS), CP\\/MAS with dipolar dephasing, and

Hosseini

1992-01-01

161

[sup 13]C solid-state NMR study of ethylene oxidation over supported silver catalysts  

Microsoft Academic Search

Solid-state NMR has been used to study the interaction of ethylene with oxygen in the absence of promoters and moderators over silica-supported silver catalysts. Experiments using nitrous oxide and oxygen as the oxidants have been carried out over Ag\\/SiO[sub 2] catalyst at temperature ranging from 298 to 613 K. Standard cross-polarization with magic angle spinning (CP\\/MAS), CP\\/MAS with dipolar dephasing,

Hosseini

1992-01-01

162

Solid liquid surface energy of pivalic acid  

NASA Astrophysics Data System (ADS)

The Gibbs-Thomson coefficient and the solid-liquid surface energy for pivalic acid have been measured by a direct method. The grain boundary energy of the pivalic acid also has been calculated from the observed grain boundary groove shapes.

Bayender, B.; Mara?li, N.; Çadirli, E.; ?i?man, H.; Gündüz, M.

1998-11-01

163

Wet spinning of solid polyamic acid fibers  

NASA Technical Reports Server (NTRS)

The invention is a process for the production of solid aromatic polyamic acid and polyimide fibers from a wet gel or coagulation bath wet gel using N,N-dimethylacetamide (DMAc) solutions of the polyamic acid derived from aromatic dianhydrides such as 3,3',4,4' benzophenonetetra carboxylic dianhydride (BTDA) and aromatic diamines such as 4,4'-oxydianiline (4,4'-ODA). By utilizing the relationship among coagulation medium and concentration, resin inherent viscosity, resin percent solids, filament diameter, and fiber void content, it is possible to make improved polyamic acid fibers. Solid polyimide fibers, obtained by the thermal cyclization of the polyamic acid precursor, have increased tensile properties compared to fibers containing macropores from the same resin system.

Dorogy, William E., Jr. (inventor); St.clair, Anne K. (inventor)

1991-01-01

164

Dispersion and activity of molybdena-alumina catalysts prepared by impregnation and solid/solid wetting methods  

SciTech Connect

Alumina-supported molybdena catalysts were prepared by both the standard incipient wetness method and by mixing MoO{sub 3} and Al{sub 2}O{sub 3} (solid/solid wetting), followed by thermal treatment of 500 C under dry or wet O{sub 2} atmospheric conditions. These catalysts were characterized by means of O{sub 2} chemisorption at {minus}78 C, CO{sub 2} uptake at ambient temperature, X-ray diffraction (XRD), and electron spin resonance (ESR) techniques. Activities of the catalysts were determined for partial oxidation of methanol and hydrodesulfurization of thiophene at atmospheric pressure. XRD results suggest high dispersion of Mo-oxide on alumina support irrespective of their method of preparation. However, O{sub 2} and CO{sub 2} uptake measurements reveal partial coverage of the Al{sub 2}O{sub 3} support surface by the Mo-oxide phase and appear to depend on the gas atmosphere (wet or dry O{sub 2}) during heat treatments in case of solid/solid wetting method. ESR, oxygen and carbon dioxide uptakes and the catalytic properties clearly demonstrate that spontaneous spreading of MoO{sub 3} on the Al{sub 2}O{sub 3} support at 500 C in the presence of wet O{sub 2} is a most effective alternative method for preparing molybdenum-alumina catalysts.

Reddy, B.M.; Reddy, E.P.; Srinivas, S.T. (Indian Inst. of Chemical Technology, Hyderabad (India))

1992-07-01

165

Low Acid Producing Solid Propellants.  

National Technical Information Service (NTIS)

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 studi...

R. R. Bennett

1995-01-01

166

sp³ -linked amorphous carbon with sulfonic acid groups as a heterogeneous acid catalyst.  

PubMed

SO?H-bearing amorphous carbon prepared from polyvinyl chloride (PVC) is studied as a heterogeneous Brønsted acid catalyst. Sulfonation of partially carbonized PVC produces amorphous carbon consisting of small SO?H-bearing carbon sheets linked by sp³ -based aliphatic hydrocarbons. This carbon material exhibits much higher catalytic performance in the hydrolysis of cellobiose than conventional heterogeneous Brønsted acid catalysts with SO?H groups, including SO?H-bearing amorphous carbon derived from cellulose. This can be attributed to a high density of SO?H groups and the fast diffusion of reactants and products enabled by a flexible carbon network. PMID:22740285

Suganuma, Satoshi; Nakajima, Kiyotaka; Kitano, Masaaki; Hayashi, Shigenobu; Hara, Michikazu

2012-09-01

167

Cathode catalysts for primary phosphoric acid fuel cells  

NASA Technical Reports Server (NTRS)

Alkylation or carbon Vulcan XC-72, the support carbon, was shown to provide the most stable bond type for linking cobalt dehydrodibenzo tetraazannulene (CoTAA) to the surface of the carbon; this result is based on data obtained by cyclic voltammetry, pulse voltammetry and by release of 14C from bonded CoTAA. Half-cell tests at 100 C in 85% phosphoric acid showed that CoTAA bonded to the surface of carbon (Vulcan XC-72) via an alkylation procedure is a more active catalyst than is platinum based on a factor of two improvement in Tafel slope; dimeric CoTAA had catalytic activity equal to platinum. Half-cell tests also showed that bonded CoTAA catalysts do not suffer a loss in potential when air is used as a fuel rather than oxygen. Commercially available polytetrafluroethylene (PTFE) was shown to be unstable in the fuel cell environment with degradation occurring in 2000 hours or less. The PTFE was stressed at 200 C in concentrated phosphoric acid as well as electrochemically stressed in 150 C concentrated phosphoric acid; the surface chemistry of PTFE was observed to change significantly. Radiolabeled PTFE was prepared and used to verify that such chemical changes also occur in the primary fuel cell environment.

1981-01-01

168

Selective oxidation using catalyst electrodes supported on solid electrolyte  

Microsoft Academic Search

The major oxygenated products of the selective oxidation of 1-butene by using a catalyst electrode were maleic anhydride on V2O5\\/YSZ\\/Ag and butadiene on MoO3?Bi2O3?Ag\\/YSZ\\/Ag. Their selectivities were enhanced as compared with the non-electrochemical system.

Seung-Doo Park; Ji-Hoon Jung; Suk-In Hong

1996-01-01

169

Preparation and characterization of a novel solid base catalyst hydroxyapatite loaded with strontium  

Microsoft Academic Search

A novel solid base catalyst was first prepared through calcining a porous hydroxyapatite loaded with Sr(NO3)2 at 873K. The catalyst was characterized by thermal gravimetric analysis, XRD, FT-IR, SEM, BET surface area analysis and the Hammett indicator method. The results indicated that the solid phase reaction of ion-exchange (Ca5(PO4)3(OH)+SrO?Ca5?x Srx(PO4)3(OH)+CaxSr1?xO) occurred at 873K. Moreover, when new phase CaxSr1?xO was dispersed

Wei Chen; Zhiliang Huang; Yu Liu; Qianjun He

2008-01-01

170

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

171

sup 13C solid-state NMR study of ethylene oxidation over supported silver catalysts.  

National Technical Information Service (NTIS)

Solid-state NMR has been used to study the interaction of ethylene with oxygen in the absence of promoters and moderators over silica-supported silver catalysts. Experiments using nitrous oxide and oxygen as the oxidants have been carried out over Ag/SiO(...

S. Hosseini

1992-01-01

172

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

Microsoft Academic Search

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

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

2009-01-01

173

Direct hydrogenation of aromatic carboxylic acids to their corresponding aldehydes with zinc oxide catalysts  

Microsoft Academic Search

High yields of aromatic aldehydes were obtained by direct hydrogenation of aromatic carboxylic acids over different zinc oxide catalysts having distinctive surface properties. The reaction is carried out in a fixed bed reactor in gas phase at 330–350°C. High selectivity of 96% of benzaldehyde at 100% conversion of benzoic acid was achieved using a zinc oxide catalyst having very weakly

W. F. Hölderich; J. Tjoe

1999-01-01

174

Solid acids as fuel cell electrolytes  

NASA Astrophysics Data System (ADS)

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°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°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°C). Here we show that a cell made of a CsHSO4 electrolyte membrane (about 1.5mm thick) operating at 150-160°C in a H2/O2 configuration exhibits promising electrochemical performances: open circuit voltages of 1.11V and current densities of 44mAcm-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.

Haile, Sossina M.; Boysen, Dane A.; Chisholm, Calum R. I.; Merle, Ryan B.

2001-04-01

175

Preparation of microspherical ?-zirconium phosphate catalysts for conversion of fatty acid methyl esters to monoethanolamides  

Microsoft Academic Search

The performance of solid catalysts and catalyst supports is generally believed to be dependent on their morphology, surface area, and architecture. In order to fully exploit their attractive properties in actual practical applications, layered zirconium phosphate materials should be fabricated into macroscopic form. Here, we report the fabrication of microscopic spheres of ?-zirconium phosphate (?-ZrP) by a spray-drying process. The

Fazhi Zhang; Yaru Xie; Wei Lu; Xiaoying Wang; Sailong Xu; Xiaodong Lei

2010-01-01

176

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

177

Heterogeneous catalysis using a nanostructured solid acid resin based on lyotropic liquid crystals.  

PubMed

The catalytic reactivity and selectivity of the first example of a nanostructured solid acid resin (1) are described. This new type of solid acid catalyst is formed by the self-assembly and copolymerization of two acidic lyotropic liquid crystals (LLCs), affording a columnar hexagonal polymer network with monodisperse nanochannels lined with sulfonic acid groups. The performance of this material as a heterogeneous catalyst was compared against that of two commercially available, amorphous sulfonic acid resins: Amberlyst-15 and Nafion NR50. Using the acid-catalyzed esterification of benzyl alcohol with 1-hexanoic acid in dry toluene as a test reaction, it was found that resin 1 displayed only slightly lower overall reactivity as compared to Amberlyst-15 and Nafion NR50 but more than an order of magnitude higher selectivity for the desired ester product over dibenzyl ether side-product. Control experiments revealed that the higher product selectivity is not due to differences in relative acidity between the nanostructured acid resin and the two amorphous resins. Instead, it appears that a large component of the enhanced selectivity is due to the regular nanostructure present in the LLC resin, which affords a much more uniform local acid microenvironment for reactions to occur. Resin 1 can also be recycled with almost complete recovery of catalytic activity and selectivity, and with essentially no leaching of reactive groups into the solution phase. PMID:14871076

Xu, Yanjie; Gu, Weiqiang; Gin, Douglas L

2004-02-18

178

SURFACE ACIDITY OF PALYGORSKITE-SUP PORTED RHODIUM CATALYSTS  

Microsoft Academic Search

Infrared spectra of adsorbed pyridine have been used to obtain qualitative information on the nature of the interaction of pyridine with different rhodium catalysts supported on palygorskite and silica. Based on these data, qualitative definitions of the adsorption sites of these catalysts have been deduced. The catalysts were prepared with natural palygorskite, and palygorskite dehydrated in vacuo at 150~ and

JUANA HERRERO; JESUS A. PAJARES; CARMEN BLANCO

179

Catalysts  

NSDL National Science Digital Library

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

Consortium, The C.

2011-12-11

180

Catalysts  

Microsoft Academic Search

A hydrotreating catalyst which is resistant to carbonaceous deposits and is particularly useful for hydrotreating coal derived liquids, is molybdenum or tungsten disulphide in an amount of 0.1 to 10% by weight, substantially completely on the outer surface of an active carbon support having a surface area in excess of 800 m2\\/g. The catalyst can be made by absorbing molybdenum

D. G. Gavin; M. A. Jones

1982-01-01

181

Kinetics of esterification of propanoic acid with methanol over a fibrous polymer-supported sulphonic acid catalyst  

Microsoft Academic Search

Esterification kinetics of propanoic acid with methanol in the presence of a fibrous polymer-supported sulphonic acid catalyst as well as a conventional resin catalyst was studied. Kinetic experiments were carried out in a laboratory-scale batch reactor operating isothermally at 55, 60 and 63°C and with different initial molar ratios of propanoic acid and methanol (1:1, 2:3 and 3:2). The fibre

J. Lilja; J. Aumo; T. Salmi; D. Yu. Murzin; P. Mäki-Arvela; M. Sundell; K. Ekman; R. Peltonen; H. Vainio

2002-01-01

182

Solid state 13C NMR characterisation study on fourth generation Ziegler-Natta catalysts.  

PubMed

In this study, solid state (13)C NMR spectroscopy was utilised to characterize and identify the metal-ester coordination in active fourth generation (phthalate) Ziegler-Natta catalysts. It is known that different donors affect the active species in ZN catalysts. However, there is still limited data available of detailed molecular information how the donors and the active species are interplaying. One of the main goals of this work was to get better insight into the interactions of donor and active species. Based on the anisotropy tensor values (?(11), ?(22), ?(33)) from low magic-angle spinning (MAS) (13)C NMR spectra in combination with chemical shift anisotropy (CSA) calculations (?(aniso) and ?), both the coordinative metal (Mg/Ti) and the symmetry of this interaction between metal and the internal donor in the active catalyst (MgCl(2)/TiCl(4)/electron donor) system could be identified. PMID:22425229

Heikkinen, Harri; Liitiä, Tiina; Virkkunen, Ville; Leinonen, Timo; Helaja, Tuulamari; Denifl, Peter

2012-01-01

183

Study of a New Iron Phosphate Catalyst for Oxidative Dehydrogenation of Isobutyric Acid  

Microsoft Academic Search

A new method of preparation of iron phosphate-based catalysts has been developed. The catalysts obtained are characterized by a single phase which is very active and selective in methacrylic acid (MAA) formation. This phase, identified as Fe2(PO3OH)P2O7, is an selective but much more active than industrial iron phosphate-based catalysts prepared by another method. The similarities between the catalytic properties of

P. Bonnet; J. M. M. Millet; C. Leclercq; J. C. Védrine

1996-01-01

184

Polymerization of Vinyl Ether by Use of Yttrium Silicate Gel as Solid Acid  

Microsoft Academic Search

The gel of yttrium silicate was utilized as a solid catalyst for the polymerization of vinyl ethers. Several silicate gels showing the different element ratios of silicon and yttrium were prepared by the co-gelation of sodium metasilicate and yttrium(III) chloride from an acidic aqueous solution through neutralization by an aqueous ammonia. The polymerizations of ethyl vinyl ether and n-butyl vinyl

Osamu Moriya; Toshio Sugizaki; Atsuko Kamejima; Ken Iwakura; Takeo Kumon; Toshifumi Kageyama

2006-01-01

185

Supported transition metal oxides as acid cracking catalysts: periodic trends and their relationship to activity and selectivity  

SciTech Connect

Surface phase oxides bonded to a support such as alumina have not been recognized previously to have acid cracking activities in the league of amorphous silica-alumina to the best of their knowledge. In this paper the relative gas-oil cracking activities of all Group IV, V, and VIB oxides supported on alumina (including alumina and rhenia on alumina) are reported. All of the supported oxides are at a surface coverage about one-third that of a monolayer. Tungsten oxide and niobium oxide on alumina have been identified as solids acids with high activity; while molybdenum oxide and rhenium oxide on alumina lead to high coke and gas make even with steam present as a cofeed in the cracking test. The periodic trends of cracking activity are those expected from the charge-to-radius ratio of the metal cation. This class of surface phase oxide solid acids has a wide range of activities (two orders of magnitude) and may prove useful for matching acid strength to specific reactions. In addition, this class of solid acids maintains surface area and cracking activity following high temperature steam treatment, in contrast to many conventional solid acid catalysts.

Murrell, L.L.; Grenoble, D.C.; Kim, C.J.; Dispenziere, N.C. Jr.

1987-10-01

186

Preyssler-Structured Tungstophosphoric Acid Catalyst on Functionalized Silica for Esterification of n Butanol with Acetic Acid  

Microsoft Academic Search

The Preyssler-structured tungstophosphoric acid catalyst supported on functionalized silica (Preyssler\\/F-silica) was prepared\\u000a by means of grafting technique with amine group as coupling media, and its catalytic behavior was investigated in the esterification\\u000a of n-butanol with acetic acid. The catalyst was characterized by infra-red spectroscopy, UV–Vis spectroscopy, Hammett indicator\\u000a and N2 adsorption techniques. Catalysts prepared directly by impregnating Preyssler acid on

Shanshan Wu; Weihong Zhang; Jun Wang; Xiaoqian Ren

2008-01-01

187

Removal of Cl adsorbed on Mn-Ce-La solid solution catalysts during CVOC combustion.  

PubMed

Mn-Ce-La oxide-mixed catalysts prepared by the method of complexation followed by calcination at 750°C were tested in the catalytic combustion of chlorobenzene (CB) taken as a model of chlorinated aromatics. XRD analyses show that Mn and La enter CeO2 matrix with a fluorite-like structure to form solid solution. The catalysts with high ratio of Mn/Mn+Ce+La exhibit high activity for CB combustion, due to high oxygen mobility. For all Mn-Ce-La catalysts, deactivation due to Cl adsorption is observed at different temperatures, depending on composition. At 330°C or higher temperature, the removal of Cl species from the surface in the forms of Cl2 (produced through Deacon reaction) and HCl (produced through hydrolysis of Cl) occurs and the activity of catalysts for CB combustion becomes thus stable. Either the addition of water or the increase in gaseous oxygen concentration can promote the removal of Cl species, and thus to increase the activity for CB combustion. High stable activity of Mn-Ce-La catalysts can be related to the combination of good oxidation and Deacon reaction performances. PMID:24863800

Wang, Xingyi; Ran, Le; Dai, Yu; Lu, Yuanjiao; Dai, Qiguang

2014-07-15

188

Active phase of calcium oxide used as solid base catalyst for transesterification of soybean oil with refluxing methanol  

Microsoft Academic Search

For developing a process of biodiesel production with environmental benignity, much interest has been focused on solid base catalysts such as calcium oxide for transesterification of vegetable oils with methanol. In this paper, the active phase of calcium oxide was investigated by characterizing the catalyst collected after achieving the conversion of edible soybean oil into its methyl ester at reflux

Masato Kouzu; Takekazu Kasuno; Masahiko Tajika; Shinya Yamanaka; Jusuke Hidaka

2008-01-01

189

Conversion of xylose into furfural using lignosulfonic Acid as catalyst in ionic liquid.  

PubMed

Preparation of biopolymer-based catalysts for the conversion of carbohydrate polymers to new energies and chemicals is a hot topic nowadays. With the aim to develop an ecological method to convert xylose into furfural without the use of inorganic acids, a biopolymer-derived catalyst (lignosulfonic acid) was successfully used to catalyze xylose into furfural in ionic acid ([BMIM]Cl). The characteristics of lignosulfonic acid (LS) and effects of solvents, temperature, reaction time, and catalyst loading on the conversion of xylose were investigated in detail, and the reusability of the catalytic system was also studied. Results showed that 21.0% conversion could be achieved at 100 °C for 1.5 h. The method not only avoids pollution from conventional mineral acid catalysts and organic liquids but also maked full use of a byproduct (lignin) from the pulp and paper industry, thus demonstrating an environmentally benign process for the conversion of carbohydrates into furfural. PMID:25007384

Wu, Changyan; Chen, Wei; Zhong, Linxin; Peng, Xinwen; Sun, Runcang; Fang, Junjie; Zheng, Shaobo

2014-07-30

190

Sulfated binary oxide solid superacids  

Microsoft Academic Search

Sulfated binary oxide solid superacids were prepared by the chemical method. The structural properties of the catalyst were examined by using BET, XRD, DTA and IR spectroscopy. Acidity properties of the catalysts were tested by Hammett indicator. Catalytic activity of the catalysts was researched by the reaction of glycerin with acetic acid in toluene. The optimum calcined temperature of the

Hua Yang; Rong Lu; Jingzhe Zhao; Xuwei Yang; Lianchun Shen; Zichen Wang

2003-01-01

191

Solid superacids as coal liquefaction catalysts: Quarterly report, January--March 1989  

Microsoft Academic Search

This research is aimed at exploring the possibility of mild coal liquefaction in the presence of solid superacids, especially oxides of iron, titanium, zirconium, and hafnium mixed with sulfate ions. FeâOâ\\/SOâ²minus\\/\\/ has been shown to be an impressively active catalyst in coal conversion at 400\\/degree\\/C. Our objective is to find conditions under which FeâOâ\\/SOâ²minus\\/\\/ and similar systems catalyze the conversion

J. W. Tierney; I. Wender

1989-01-01

192

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

PubMed

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

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

2012-04-17

193

Silica supported phosphomolybdic acid: an efficient heterogeneous catalyst for Friedlander synthesis of quinolines.  

PubMed

Silica supported phosphomolybdic acid, an eco-friendly heterogeneous catalyst, has been found to be highly efficient for Friedlander synthesis of quinolines in excellent yields. A variety of ketones afford the quinolines smoothly. The catalyst can be easily recovered and reused. PMID:18591832

Das, Biswanath; Krishnaiah, Martha; Laxminarayana, Keetha; Nandankumar, Duddukuri

2008-07-01

194

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

195

Preparation of MCM-41 supported phosphoric acid catalyst for thiophenic compounds alkylation in FCC gasoline  

Microsoft Academic Search

The alkylation of thiophenic sulfur compounds with olefins in FCC gasoline followed by distillation of heavy compounds is a good alternative to classical desulfurization technologies. In this study, the preparation condition of MCM-41 supported phosphoric acid catalyst was optimized and the activity tests in real gasoline proved that the optimal catalyst was promising to be applied in the alkylation transfer

Rong Wang; Yonghong Li

2010-01-01

196

A catalyst system for the formation of amides by reaction of carboxylic acids with blocked isocyanates  

Microsoft Academic Search

A catalyst for the reaction of blocked isocyanates (blocking agent diisopropylamine and dimethyl pyrazole) and carboxylic acids was identified. Magnesium and in some instances calcium salts proved to be highly active as catalyst. This reaction gives amides in quantitative yield and excellent selectivity and is suitable for coating and general chemical purposes.

R. Gertzmann; C. Gürtler

2005-01-01

197

Catalysts  

SciTech Connect

A hydrotreating catalyst which is resistant to carbonaceous deposits and is particularly useful for hydrotreating coal derived liquids, is molybdenum or tungsten disulphide in an amount of 0.1 to 10% by weight, substantially completely on the outer surface of an active carbon support having a surface area in excess of 800 m2/g. The catalyst can be made by absorbing molybdenum or tungsten trisulphide onto the active carbon support and reducing the trisulphide to the disulphide.

Gavin, D.G.; Jones, M.A.

1982-02-02

198

Acid and Base Catalysts in the Hybrid Silica Sol–Gel Process  

Microsoft Academic Search

Sol–gel silicas were synthesized from the hydrolysis of tetraethoxysilane andN-?-aminoethyl-?-aminopropyltrimethoxysilane in the presence of water and ethanol by using ammonium hydroxide or hydrochloric acid as base or acid catalysts, respectively. The influence of the type of the catalyst employed was studied by comparing the surface areas and pore sizes and volumes for both sol–gel silicas. Nitrogen elemental analysis and13C and29Si

Cesar R. Silva; Claudio Airoldi

1997-01-01

199

Metal-organic frameworks of vanadium as catalysts for conversion of methane to acetic acid.  

PubMed

A catalytic system combining the high activity of homogeneous catalysts and the ease of use of heterogeneous catalysts for methane activation is reported. The vanadium-containing metal-organic frameworks (MOFs) MIL-47 and MOF-48 are found to have high catalytic activity and chemical stability. They convert methane selectively to acetic acid with 70% yield (490 TON) based on K(2)S(2)O(8) as an oxidant. Isotopic labeling experiments showed that two methane molecules are converted to the produced acetic acid. The MOF catalysts are reusable and remain catalytically active for several recycling steps without losing their crystalline structures. PMID:21766786

Phan, Anh; Czaja, Alexander U; Gándara, Felipe; Knobler, Carolyn B; Yaghi, Omar M

2011-08-15

200

A humic-acid-like polycondensate produced with no use of catalyst.  

PubMed

The synthesis and physicochemical characterization of a water soluble humic-acid-like polycondensate (HALP), which mimics fundamental physicochemical and spectroscopic properties of natural humic acids is presented. The polymer can be synthesized under ambient O(2) by oxidative co-polymerization of gallic (GA) and protocatechuic (PA) acid at pH >9, with no need for a catalyst. Solid state (13)C NMR spectra for GA-PA-HALP show that ring-opening reactions of GA, PA monomers are involved in GA-PA-HALP formation. EPR spectroscopy shows that GA-PA-HALP contains stable phenol-based radicals, with pH-dependent concentration. The H-binding profile of GA-PA-HALP follows the NICA-Donnan model, with two sets of distributed pK(a) values in the range 4-6 corresponding to carboxyl groups, and 7-9 corresponding to phenolic groups, as in natural HA. GA-PA-HALP bears a permanent negative charge Q(0)=-2.3 equiv kg(-1) which is higher than the literature Q(0) values of -1 to -2 equiv kg(-1) observed for natural HAs. A critical comparison of the present data with literature data is provided. PMID:19394625

Giannakopoulos, Evangelos; Drosos, Marios; Deligiannakis, Yiannis

2009-08-01

201

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

202

Stability of supported platinum sulfuric acid decomposition catalysts for use in thermochemical water splitting cycles  

Microsoft Academic Search

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 (96wt%) at atmospheric pressure at temperatures between 800 and 850?C and a weight hour space

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

2007-01-01

203

Size and ability do matter! Influence of acidity and pore size on the synthesis of hindered halogenated meso-phenyl porphyrins catalysed by porous solid oxides.  

PubMed

The rationalisation of the influence of acidity and pore size of several solid oxides so that they selectively act as supports for preparation of encapsulated porphyrin hybrid materials or as catalysts for synthesis of porphyrins in solution is discussed. Encapsulated porphyrin yields are dependent on both the acidity and the material pore size, Al-MCM-41 being the best fitting solid, with Lewis acidity of 120 ?mol Py per g and a pore size 30 Å. On the other hand, when the goal is the synthesis of hindered mesoarylporphyrins in solution, the best solid porous catalyst is NaY, with Lewis acidity of 510 ?mol Py per g and a pore size 14 Å. This method provides an appealing efficient, reusable and scalable catalyst alternative for one-pot synthesis of meso-arylporphyrins in high yields. PMID:24643723

Silva, Mónica; Fernandes, Auguste; Bebiano, Suse S; Calvete, Mário J F; Ribeiro, M Filipa; Burrows, Hugh D; Pereira, Mariette M

2014-05-27

204

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

205

Toluene and chlorobenzene dinitration over solid H3PO4/MoO3/SiO2 catalyst.  

PubMed

A new catalyst, H(3)PO(4)/MoO(3)/SiO(2), was prepared by modification of MoO(3)/SiO(2) using phosphoric acid. The characterization of the catalyst was performed using Infrared and Raman Spectroscopy, potentiometric titration and nitrogen adsorption-desorption methods. Molybdenum oxides were identified along with phosphomolybdic acid and polymolybdates on the modified surface. The suitability of the catalysts for toluene and chlorobenzene nitration in continuous process was examined. Toluene is effectively nitrated to dinitrotoluene (DNT) in one-stage process (96 wt.% of DNT in the product) and in mild conditions i.e. at room temperature and only with ten-fold excess of nitric acid. In chlorobenzene nitration only twelve-fold excess of nitric acid is needed to obtain as high yield as 95 wt.%. Most importantly, the novel catalysts we have developed, provide the opportunity for sulfuric acid- free nitration of aromatic compounds. PMID:21885194

Adamiak, Joanna; Kalinowska-Alichnewicz, Dorota; Szadkowski, Micha?; Skupi?ski, Wincenty

2011-11-15

206

Effect of calcination temperature on the activity of solid Ca/Al composite oxide-based alkaline catalyst for biodiesel production.  

PubMed

A solid Ca/Al composite oxide-based alkaline catalyst containing Ca(12)Al(14)O(33) and CaO was prepared by chemical synthesis and thermal activation from sodium aluminate solution and calcium hydroxide emulsion. The effect of calcination temperatures ranging from 120 °C to 1000 °C on activity of the catalyst was investigated. The catalyst calcined at 600 °C showed the highest activity with >94% yield of fatty acid methyl esters (i.e. biodiesel) when applied to the transesterification of rapeseed oil at a methanol:oil molar ratio of 15:1 at 65 °C for 3h. Structure and properties of the catalyst were studied and the characterizations with XRD, TGA, FTIR, BET, and SEM demonstrated that the performance of the catalyst was closely related to its specific surface area and crystalline structure. In particular, the generation of crystalline Ca(12)Al(14)O(33) improved the catalytic activity due its synergistic effect with CaO. PMID:23196252

Meng, Yong-Lu; Wang, Bo-Yang; Li, Shu-Fen; Tian, Song-Jiang; Zhang, Min-Hua

2013-01-01

207

Solid-state actinide acid phosphites from phosphorous acid melts  

NASA Astrophysics Data System (ADS)

The reaction of UO3 and H3PO3 at 100 °C and subsequent reaction with dimethylformamide (DMF) produces crystals of the compound (NH2(CH3)2)[UO2(HPO2OH)(HPO3)]. This compound crystallizes in space group P21/n and consists of layers of uranyl pentagonal bipyramids that share equatorial vertices with phosphite units, separated by dimethylammonium. In contrast, the reaction of phosphorous acid and actinide oxides at 210 °C produces a viscous syrup. Subsequent dilution in solvents and use of standard solution-state methods results in the crystallization of two polymorphs of the actinide acid phosphites An(HPO2OH)4 (An=U, Th) and of the mixed acid phosphite-phosphite U(HPO3)(HPO2OH)2(H2O)·2(H2O). ?- and ?-An(HPO2OH)4 crystallize in space groups C2/c and P21/n, respectively, and comprise a three-dimensional network of An4+ cations in square antiprismatic coordination corner-sharing with protonated phosphite units, whereas U(HPO3)(HPO2OH)2(H2O)2·(H2O) crystallizes in a layered structure in space group Pbca that is composed of An4+ cations in square antiprismatic coordination corner-sharing with protonated phosphites and water ligands. We discuss our findings in using solid inorganic reagents to produce a solution-workable precursor from which solid-state compounds can be crystallized.

Oh, George N.; Burns, Peter C.

2014-07-01

208

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

209

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

SciTech Connect

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

Not Available

1993-07-01

210

Supported olefin polymerization catalyst  

SciTech Connect

A solid, hydrocarbon-insoluble, alpha-olefin polymerization catalyst component is described comprising the product formed by: A. complexing a magnesium alkyl composition with an ortho disubstituted hindered carboxylic aromatic acid ester; B. reacting the resulting stable complex with a compatible precipitation agent to form a solid component; and C. reacting the resulting solid with a titanium compound in a suitable diluent containing a suitable electron donor compound.

Johnson, B.V.; Karayannis, N.M.; Hoppin, C.R.; Ornellas, L.

1986-04-08

211

Consequences of acid strength for isomerization and elimination catalysis on solid acids.  

PubMed

We address here the manner in which acid catalysis senses the strength of solid acids. Acid strengths for Keggin polyoxometalate (POM) clusters and zeolites, chosen because of their accurately known structures, are described rigorously by their deprotonation energies (DPE). Mechanistic interpretations of the measured dynamics of alkane isomerization and alkanol dehydration are used to obtain rate and equilibrium constants and energies for intermediates and transition states and to relate them to acid strength. n-Hexane isomerization rates were limited by isomerization of alkoxide intermediates on bifunctional metal-acid mixtures designed to maintain alkane-alkene equilibrium. Isomerization rate constants were normalized by the number of accessible protons, measured by titration with 2,6-di-tert-butylpyridine during catalysis. Equilibrium constants for alkoxides formed by protonation of n-hexene increased slightly with deprotonation energies (DPE), while isomerization rate constants decreased and activation barriers increased with increasing DPE, as also shown for alkanol dehydration reactions. These trends are consistent with thermochemical analyses of the transition states involved in isomerization and elimination steps. For all reactions, barriers increased by less than the concomitant increase in DPE upon changes in composition, because electrostatic stabilization of ion-pairs at the relevant transition states becomes more effective for weaker acids, as a result of their higher charge density at the anionic conjugate base. Alkoxide isomerization barriers were more sensitive to DPE than for elimination from H-bonded alkanols, the step that limits 2-butanol and 1-butanol dehydration rates; the latter two reactions showed similar DPE sensitivities, despite significant differences in their rates and activation barriers, indicating that slower reactions are not necessarily more sensitive to acid strength, but instead reflect the involvement of more unstable organic cations at their transition states. These compensating effects from electrostatic stabilization depend on how similar the charge density in these organic cations is to that in the proton removed. Cations with more localized charge favor strong electrostatic interactions with anions and form more stable ionic structures than do cations with more diffuse charges. Ion-pairs at elimination transition states contain cations with higher local charge density at the sp(2) carbon than for isomerization transition states; as a result, these ion-pairs recover a larger fraction of the deprotonation energy, and, consequently, their reactions become less sensitive to acid strength. These concepts lead us to conclude that the energetic difficulty of a catalytic reaction, imposed by gas-phase reactant proton affinities in transition state analogues, does not determine its sensitivity to the acid strength of solid catalysts. PMID:19374417

Macht, Josef; Carr, Robert T; Iglesia, Enrique

2009-05-13

212

MCF-supported boronic acids as efficient catalysts for direct amide condensation of carboxylic acids and amines.  

PubMed

For efficient direct amide condensations, a new class of catalysts are developed by immobilizing boronic acids on mesocellular siliceous foam. Associated with their large pores, the microenvironments surrounding the immobilized active species greatly influence the catalytic activity. The fluoroalkyl moieties on the silica surface significantly enhance the catalytic performance along with easy recovery and reuse. This approach proposes a potential way to optimize various types of silica-supported catalysts. PMID:24848459

Gu, Liuqun; Lim, Jaehong; Cheong, Jian Liang; Lee, Su Seong

2014-07-01

213

Acid leached Raney copper catalysts for the water–gas shift reaction  

Microsoft Academic Search

Raney copper catalysts were prepared by leaching a ternary alloy of composition Cu(24.8) Zn(25.2) Al(48.3) in nitric and perchloric acid. The acid leaching process was examined as a function of acid strength and total leach time. Similarities in acid and caustic leaching were observed. For example, during the first hour of leaching in both media, aluminium was extracted at a

J. R. Mellor; N. J. Coville; S. H. Durbach; R. G. Copperthwaite

1998-01-01

214

Zirconium phosphonates layered structure catalysts with organic acid pendants 2. Catalytic properties  

Microsoft Academic Search

Catalytic properties of Zirconium phosphonates layered structure (ZPLS) catalysts with organic sulfonic acid pendant groups\\u000a have been studied. The NaOH titration demonstrated the presence of sulfonic acid groups. The ZPLS contained acid sites per\\u000a weight similar to or slightly less than those for cation exchanged resins. The hydrolysis of ethyl acetate and the esterification\\u000a of acetic acid with ethanol were

Chang Mo Nam; Young Gul Kim; Jae Sung Lee

1995-01-01

215

Kinetic study of the esterification of free fatty acids in non-edible Pongamia pinnata oil using acid catalyst  

Microsoft Academic Search

Pre treatment of high free fatty acid containing Pongamia pinnata oil using sulfuric acid catalyst has been optimized. The kinetics of the pre treatment esterification process was studied. The experimental results were found to fit a Pseudo first-order kinetics. The influence of temperature on the rate constants was determined by fitting the results to the Arrhenius equation. The activation energy

J. Nandagopal; V. Sathya; Selva Bala; S. Dinesh Kirupha; P. Vijayalakshmi; S. Sivanesan

2009-01-01

216

Development of heterogeneous catalysts for the conversion of levulinic acid to ?-valerolactone.  

PubMed

?-Valerolactone (GVL) has been identified as a potential intermediate for the production of fuels and chemicals based on renewable feedstocks. Numerous heterogeneous catalysts have been used for GVL production, alongside a range of reaction setups. This Minireview seeks to outline the development of heterogeneous catalysts for the targeted conversion of levulinic acid (LA) to GVL. Emphasis has been placed on discussing specific systems, including heterogeneous noble and base metal catalysts, transfer hydrogenation, and application of scCO? as reaction medium, with the aim of critically highlighting both the achievements and remaining challenges associated with this field. PMID:22890968

Wright, William R H; Palkovits, Regina

2012-09-01

217

Titanium-based solid catalysts for transesterification of methyl-methacrylate by 1-butanol: the homogeneous catalysis contribution  

Microsoft Academic Search

Titanium-based solid catalysts were prepared according to two different procedures. In order to improve the stability of the SiOTi bond in the titanium grafted silica catalysts, the surface remaining hydroxyl groups were passivated to prevent the titanium leaching by SiOTi bond solvolysis. This was performed by grafting trimethoxy-silane groups on isolated silanols of silica, after or before metal grafting. The

Maria Concetta Gaudino; Romain Valentin; Daniel Brunel; François Fajula; Françoise Quignard; Alain Riondel

2005-01-01

218

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

219

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

220

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

221

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

222

Effect of calcination temperature of Ni\\/?-Al2O3 catalyst on the steam reforming of acetic acid  

Microsoft Academic Search

Ni\\/?-Al2O3-550 and Ni\\/?-Al2O3-800 catalysts (calcined at 550°C and 800°C in the catalyst preparation) were prepared with a impregnation method. Steam reforming of acetic acid as a model compound of bio-oil for hydrogen production had been investigated on the catalysts. The fresh catalysts were characterized by X-ray diffraction (XRD), temperature programmed reduction (TPR-H2) and specific surface area analysis (BET). The spent

Lu An; Changqing Dong; Junjiao Zhang; Yongping Yang

2009-01-01

223

Comparison of different Lewis acid supported on hydroxyapatite as new catalysts of Friedel–Crafts alkylation  

Microsoft Academic Search

ZnCl2, NiCl2 and CuCl2 supported on hydroxyapatite (HAP), as a new solid support, catalyse the Friedel–Crafts alkylation of benzene, toluene and p-xylene by benzyl chloride. The reaction proceeds selectively to monoalkyl-compounds and in a short reaction time. The best catalytic activities were observed with the zinc catalysts.

Rachid Tahir; Rachid Nazih

2001-01-01

224

Development of a kinetic model for the esterification of acetic acid with methanol in the presence of a homogeneous acid catalyst  

Microsoft Academic Search

The esterification kinetics of acetic acid with methanol in the presence of hydrogen iodide as a homogeneous acid catalyst was studied with isothermal batch experiments at 30–60°C. The catalyst concentration was varied between 0.05 and 10.0 wt%. The experiments revealed that besides the main reaction, the esterification of acetic acid, a side reaction appeared: the catalyst, hydrogen iodide, was esterified

Robert Rönnback; Tapio Salmi; Antti Vuori; Heikki Haario; Juha Lehtonen; Anna Sundqvist; Esko Tirronen

1997-01-01

225

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

226

Sulfonic acid functionalized poly (ethylene glycol dimethacrylate-1-vinyl-1,2,4-triazole) as an efficient catalyst for the synthesis of methyl propionate  

Microsoft Academic Search

Sulfonic acid functionalized poly (ethylene glycol dimethacrylate-1-vinyl-1,2,4-triazole), poly (EGDMA–VTAZ–SO3H) (average diameter 1.0–1.5mm), was found to be efficient solid acid catalyst for the esterification of methanol and propionic acid under heterogeneous reaction conditions. The pristine polymer, poly (EGDMA–VTAZ), was produced by suspension polymerization and then proton-conducting polymer was obtained by blending of poly (EGDMA–VTAZ) with different percentage of H2SO4 solutions. The

Beyhan Erdem; Ali Kara

2011-01-01

227

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.

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

2014-01-01

228

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

PubMed

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

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

2014-01-01

229

Comparison of acidic and alkaline catalysts for preparation of fatty acid methyl esters from ovine muscle with emphasis on conjugated linoleic acid  

Microsoft Academic Search

Methanolic reagents containing acidic catalysts, HCl (0.5 M, 1 h, 80° C) or BF3 (14%, 1 h, 80° C), or alkaline catalysts, KOH (0.2 M, 15–60 min, 50° C) or NaOCH3 (0.5 M, 15–60 min, 50° C), were compared for use in preparation of fatty acid methyl esters for GC analysis of total lipids from freeze-dried semitendinosus muscle of lambs

C. M. Murrieta; B. W. Hess; D. C. Rule

2003-01-01

230

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

231

Reductive amination of N-linked oligosaccharides using organic acid catalysts  

Microsoft Academic Search

The reductive amination of oligosaccharides with 8-aminopyrene-1,3,6-trisulfonate in several organic acids of varying strength was examined by capillary electrophoresis using laser-induced fluorescence detection. The relationship between the derivatization yield and the pKa of the catalyst (organic acids) is in agreement with the general acid catalysis of the hemiacetal ring opening and the Shiff base formation, one of which is considered

Ramon A. Evangelista; Fu-Tai A. Chen; András Guttman

1996-01-01

232

Organo-niobate Ionic Liquids: Synthesis, Characterization and Application as Acid Catalyst in Pechmann Reactions  

PubMed Central

The combinations of 1-butyl-3-methylimidazolium chloride with NbCl5 yielded ionic mixtures with different melting point temperatures and acidity depending on the niobium molar fraction. The mixtures were characterized by thermal (DSC) and spectroscopic (FT-IR and 1H NMR) analysis. The Pechmann reactions of different phenols with ethylacetoacetate, producing coumarins, was used as model to evaluate the catalytic behavior of these mixtures as acid Lewis catalyst. These reactions were carried out using acidic mixtures of 60 mol%.

Soares, Valerio C. D.; Alves, Melquizedeque B.; Souza, Ernesto R.; Pinto, Ivana O.; Rubim, Joel C.; Andrade, Carlos Kleber Z.; Suarez, Paulo A. Z.

2007-01-01

233

Application of a supported iron oxyhydroxide catalyst in oxidation of benzoic acid by hydrogen peroxide  

Microsoft Academic Search

Oxidation of benzoic acid was studied via Fenton-like reaction using an innovative supported ?-FeOOH catalyst. The decomposition kinetics of hydrogen peroxide was investigated first. Oxidation of benzoic acid by hydrogen peroxide was performed to understand the effects of initial pH and hydrogen peroxide dosage. The treatment efficiency of benzoic acid at an initial pH of 3.2 was higher than at

Shanshan Chou; Chihpin Huang

1999-01-01

234

Durability of WO 3\\/ZrO 2–CuO\\/CeO 2 catalysts for steam reforming of dimethyl ether  

Microsoft Academic Search

Development of catalysts for steam reforming of dimethyl ether (DME) producing hydrogen was carried out with the aim of improving catalyst durability. The catalyst consisted of a mixture of solid acid catalysts for hydration of DME to methanol and 40wt.% CuO\\/CeO2 catalyst for steam reforming of methanol. Among various acid catalysts examined, 10wt.% WO3\\/ZrO2 had the highest performance. WO3\\/ZrO2 showed

Toshiya Nishiguchi; Kengo Oka; Tomoaki Matsumoto; Hiroyoshi Kanai; Kazunori Utani; Seiichiro Imamura

2006-01-01

235

Effect of carbon material on Pd catalyst for formic acid electrooxidation reaction  

NASA Astrophysics Data System (ADS)

Effect of several usually used carbon materials on Pd catalyst for formic acid electrooxidation reaction is studied by physical characterization and electrochemical measurements. New active sites are formed due to the Pd and carbon interaction which is confirmed by the XPS measurements, and electrochemical impedance spectroscopy confirms that the presence of the carbon material reduced the charge transfer resistance. Further, an improved fuel cell performance is observed when integrating the carbon-modified Pd catalyst in to a direct formic acid fuel cell. The results reveal that the carbon material is not only used as support, but also involves the new active sites formation.

Chang, Jinfa; Li, Songtao; Feng, Ligang; Qin, Xiujuan; Shao, Guangjie

2014-11-01

236

The roles of BrØnsted and Lewis surface acid sites in acid-treated montmorillonite supported ZnCl 2 alkylation catalysts  

Microsoft Academic Search

The catalyst known as “clayzic” (ZnCl2 supported on acid-treated montmorillonite) exhibits both BrØnsted and Lewis surface acidities. The relative catalytic activities of these two types of acid site have been determined in a range of reactions, by comparing the activities of clayzic with those of related catalysts which exhibit only one type of surface acidity. Acid-treated montmorillonite has been used

J. Massam; D. R. Brown

1995-01-01

237

Hydrocarbon selectivity model for gas-solid Fischer-Tropsch synthesis on precipitated iron catalysts  

SciTech Connect

The kinetics of the gas-solid Fischer-Tropsch (FT) synthesis over a commercial Fe-Cu-K-SiO{sub 2} catalyst was studied in a continuous spinning basket reactor. Experimental conditions were varied as follows: reactor pressure of 0.8--3.2 MPa, H{sub 2}/CO feed ratio = 0.5--2.0, and a space velocity of 0.5--2.0 {times} 10{sup {minus}3} Nm{sup 3}/kg{sub cat} s at a constant temperature of 523 K. A new product distribution model for linear hydrocarbons is proposed. Deviations from conventional Anderson-Schulz-Flory distribution can be quantitatively described with an {alpha}-olefin readsorption product distribution model. The experimentally observed relatively high yield of methane, relatively low yield of ethene, and both the exponential decrease of the olefin-to-paraffin ratio and the change of the chain growth parameter with chain length can all be predicted from this new model. It combines a mechanistic model of olefin readsorption with kinetics of chain growth and termination on the same catalytic sites. The hydrocarbon formation is based on the surface carbide mechanism by CH{sub 2} insertion. The olefin readsorption rate depends on the chain length because of increasing physisorption strength on the catalyst surface and increasing solubility in FT wax with increasing chain length. Interfacial concentrations of reactive olefins near the gas-wax and wax-catalyst surface are used in the kinetic model. With optimization of three parameters per experimental product distribution, the olefin readsorption product distribution model proved to predict product selectivities accurately over the entire range of experimental conditions. The relative deviations are 10.1% and 9.1% for the selectivity to paraffins and olefins with n < 11, respectively.

Laan, G.P. van der; Beenackers, A.A.C.M. [Univ. of Groningen (Netherlands). Dept. of Chemical Engineering

1999-04-01

238

Liquid phase nitration of benzene over supported ammonium salt of 12-molybdophosphoric acid catalysts prepared by sol-gel method.  

PubMed

A mild and clean liquid nitration of benzene with 65% nitric acid as nitrating agent over silica supported ammonium salt of 12-molybdophosphoric acid catalysts has been investigated. These catalysts with different loadings were prepared by sol-gel method and characterized by X-ray diffraction (XRD) and FTIR spectra. The acidity of these catalysts was measured by the potentiometric titration method. The XRD and IR analysis revealed that supported catalysts possess the Keggin structure which is similar to 12-molybdophosphoric acid. And it can be found that the supported catalysts had high nitration reaction catalytic activity and selectivity over nitrobenzene. The effects of various parameters such as nitric acid/benzene volume ratio, temperature and time of reaction have also been systematically studied. PMID:20185228

Gong, Shuwen; Liu, Lijun; Cui, Qingxin; Ding, Junhong

2010-06-15

239

Superprotonic Solid Acids Thermochemistry, Structure, and Conductivity  

NASA Astrophysics Data System (ADS)

In this work, in order to investigate the thermochemistry and property of the superprotonic solid acid compounds, the measurement methods were established for in situ observation, because superprotonic phases are neither stable at room temperature nor freezable to room temperature. A humidity-controlled TG, DSC and AC impedance measurement system, and high temperature stage for XRD were built for thermal analysis and characterization of the solid acid compounds. The thermodynamic and kinetics of the dehydration and hydration of CsH 2PO4 is investigated by TG, DSC, and XRD analysis. By making use of the enhanced kinetics afforded by SiO2, the phase boundary between CsH2PO4, CsPO3, and dehydrated liquid was precisely determined. The stability of CsH2PO4 and the liquid dehydrate, CsH2(1-x)PO4-x(l), were confirmed by the complete reversal of dehydration to recover these phases in the appropriate temperature and water partial pressure ranges. Rehydration and conversion of CsPO3(s) to CsH2PO4(s) occurs over a period of several hours, depending on temperature, water partial pressure, and morphology of the metaphosphate. High and small particles favor rapid dehydration, whereas the temperature dependence of the rehydration kinetics is nonmonotonic, reaching its fastest rate in the vicinity of the superprotonic transition. Doping Rb and K into CDP was examined and the stable region of Cs 1-xRbxH2PO4 and Cs1-xKxH2PO 4 are determined by in situ XRD and DSC measurement. Then the effects of doping to the structure and conductivity are discussed. It was found that Rb has whole-range solubility for both cubic and monoclinic CDP. Ts increases and Td decrease with Rb content. K has 27% solubility for cubic CDP, T s and Td decrease with K content. The eutectic temperature is 208 +/- 2°C. The lattice size of Rb- or K- doped CDP depends on the averaged cation size. Conductivity linearly decreases by dopant concentration. The impact of K doping is deeper than that of Rb for the equivalent averaged cation size. In situ XRD measurement was carried out using single-crystal CsH2PO4 in order to study the phase transformation mechanism of this compound. A plate-like single crystal with (100) orientation was prepared, and the phase transition was observed by heating and cooling with ramp rate 0.2 K/min. From the obtained XRD profile---the after-first-phase transition (monoclinic?cubic)---the distribution of the domain orientation was estimated. It was found that (100) is the preferential orientation after phase transition, however, the amount of the domains with other orientation is not ignorable. Therefore, it is considered that the phase transformation in CsH 2PO4 is not simple martensitic, but that some other event, such as recrystallization, happens during the transition process.

Ikeda, Ayako

240

Electrode catalyst  

SciTech Connect

An electrode catalyst for a fuel cell comprising at least one boride of molybdenum is disclosed. The electrode catalyst is far more excellent than conventional catalysts such as platinum black in that the resistance to acids is very high, that the polarization is little, that the price is low, etc. It is particularly suitable as an electrode catalyst for a fuel cell employing an acidic electrolyte.

Kudo, T.; Obayashi, H.

1980-12-30

241

Catalytic conversion of cellulose to 5-hydroxymethyl furfural using acidic ionic liquids and co-catalyst.  

PubMed

Efficient catalytic conversion of microcrystalline cellulose (MCC) to 5-hydroxymethyl furfural (HMF), is achieved using acidic ionic liquids (ILs) as the catalysts and metal salts as co-catalysts in the solvent of 1-ethyl-3-methylimidazo-lium acetate ([emim][Ac]). A series of acidic ILs has been synthesized and tested in conversion of MCC to HMF. The effect of reaction conditions, such as reaction time, temperature, catalyst dosage, metal salts, water dosage, Cu(2+) concentration and various acidic ILs are investigated in detail. The results show that CuCl(2) in 1-(4-sulfonic acid) butyl-3-methylimidazolium methyl sulfate ([C(4)SO(3)Hmim][CH(3)SO(3)]), is found to be an efficient catalyst for catalytic conversion of MCC to HMF, and 69.7% yield of HMF is obtained. A mechanism to explain the high activity of CuCl(2) in [C(4)SO(3)Hmim][CH(3)SO(3)] is proposed. To the best of our knowledge, this report first proposes that the Cu(2+) and [C(4)SO(3)Hmim][CH(3)SO(3)] show better catalytic performance in catalytic conversion of MCC to HMF. PMID:22840003

Ding, Zhen-Dong; Shi, Jin-Cai; Xiao, Jing-Jing; Gu, Wen-Xiu; Zheng, Chang-Ge; Wang, Hai-Jun

2012-10-01

242

Improved hydrogen production from formic acid on a Pd/C catalyst doped by potassium.  

PubMed

The rate of hydrogen production from vapour-phase formic acid decomposition can be increased by 1-2 orders of magnitude by doping a Pd/C catalyst with potassium ions. Surface potassium formate and/or bicarbonate species could be involved in the rate-determining step of this reaction. PMID:22447125

Bulushev, Dmitri A; Jia, Lijun; Beloshapkin, Sergey; Ross, Julian R H

2012-05-01

243

[Catalytic ozonation of oxalic acid in water with Pt/graphite catalyst].  

PubMed

Pt/graphite catalyst was prepared by incipient wetness impregnation using H2PtCl6 x 6H2O as precursor substance. The removal efficiencies of oxalic acid by Pt/graphite, graphite catalyzed ozonation and ozonation alone were compared. It was found that the removal efficiency of oxalic acid in ozonation alone, graphite and Pt/graphite catalyzed ozonation was 3.0%, 47.6% and 99.3% respectively under the present experimental conditions. Results showed that loading of Pt could significantly increase the catalytic activity of graphite. Taking oxalic acid degradation efficiency as indication, the preparation conditions of Pt/graphite were optimized. The pretreatment of graphite had no favor to improve the activity of Pt/graphite catalyst. The optimal preparation conditions of Pt/graphite catalyst are as follow: impregnant, distilled water; impregnation time, 24 h; the loading amount of Pt, 1.0%; reduction temperature, 35 degrees C. The Pt/graphite catalyst was used for five times with no significant decrease of its activity and more than 90% oxalic acid removal was obtained. PMID:17674732

Liu, Zheng-Qian; Ma, Jun; Zhao, Lei

2007-06-01

244

Oxidizing of ferulic acid with the use of polyoxometalates as catalysts  

NASA Astrophysics Data System (ADS)

The kinetics of catalytic oxidation for ferulic acid with polyoxometalates used as catalysts was studied. The effect of pH and concentrations of the principal reacting components on the process kinetics was studied. A kinetic scheme of oxidation is proposed, and the values of a number of kinetic parameters of the process are determined.

Povarnitsyna, T. V.; Popova, N. R.; Bogolitsyn, K. G.; Beloglazova, A. L.; Pryakhin, A. N.; Lunin, V. V.

2010-12-01

245

Photo-degradation of acid green dye over Co-ZSM-5 catalysts prepared by incipient wetness impregnation technique.  

PubMed

Co-ZSM-5 catalysts with different Co-loadings (2-30wt.%) were prepared by incipient wetness impregnation method. The prepared solid catalysts were characterized by X-ray diffraction, FTIR, in situ FTIR of pyridine adsorption and surface area measurements. The XRD data presented disintegration in the zeolitic crystalline structure accompanied by an increase in particle size of the prepared solids. New phases, Co(3)O(4) and Co(2)SiO(4), were detected with increasing the Co-loading, which indicate the strong interaction of cobalt ions with the ZSM-5 zeolite. FTIR study proved the presence of Co ions in stabilized sites inside the ZSM-5 framework. The in situ FTIR of adsorbed pyridine determined the type and relative strength of acidity on the surface of the prepared solids. The acidity switched from B-acid sites to L-acid sites with impregnation of cobalt ions in ZSM-5 zeolite. The acidity decreased with increasing Co-loading, which might be due to the destruction of zeolite framework and presence of new phases such as cobalt silicate and cobalt oxide on the surface. The surface texture characteristics changed with the promotion of ZSM-5 by cobalt ions, since a decrease of surface area, mean pore radius and pore volume was observed. The assessment of the catalytic activity was performed by the use of the photo-degradation of acid green (AG) dye as a probe reaction in presence of H(2)O(2) as an oxidant. The pH value controlled the degradation rate since a gradual increase of AG degradation rate was observed with increasing pH value and the optimum H(2)O(2) concentration was 61.6 mmol/l. It was found that, the AG degradation rate increased until an optimum value of Co-loading (ca. 10 wt.%), beyond which a monotonic decrease of reaction rate was recognized. The experimental data pointed to the importance of both the cobalt moieties and the zeolite framework structure in the AG degradation reaction. PMID:17904732

El-Bahy, Zeinhom M; Mohamed, Mohamed M; Zidan, Farouk I; Thabet, Mohamed S

2008-05-01

246

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

PubMed

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

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

2014-02-01

247

The behavior of palladium catalysts in direct formic acid fuel cells  

NASA Astrophysics Data System (ADS)

Previous work has considered the behavior of platinum based catalysts in direct methanol and Direct Formic Acid Fuel Cells (DFAFCs). In this paper, we explore the behavior of palladium-based anode catalyst for DFAFCs. The palladium catalysts produce significant performance enhancements. DFAFCs operated with dry air and zero back-pressure can generate power densities of 255˜230 mW cm -2 at relatively high voltages of 0.40˜0.50 V in a concentration range of formic acid from 3.0 to 15.0 M at a room temperature of 20 °C, which are not quite different from a hydrogen-air polymer exchange membrane (PEM) fuel cell with power density of 320 mW cm -2 obtained under the comparable conditions, and much higher than a direct methanol fuel cell (DMFC) with power density of 50 mW cm -2. The stability of the membrane electrode assembly (MEA) with palladium catalyst has also been evaluated. There is some decay in performance over several hours. However, the performance loss of DFAFCs can be fully recovered by applying a positive potential at the fuel cell anode after short-term life test. These results demonstrate that DFAFCs with palladium anode catalyst have exceptional properties for portable power applications.

Zhu, Yimin; Khan, Zakia; Masel, R. I.

248

Photodegradation of acid green dye over Co–ZSM-5 catalysts prepared by incipient wetness impregnation technique  

Microsoft Academic Search

Co–ZSM-5 catalysts with different Co-loadings (2–30wt.%) were prepared by incipient wetness impregnation method. The prepared solid catalysts were characterized by X-ray diffraction, FTIR, in situ FTIR of pyridine adsorption and surface area measurements. The XRD data presented disintegration in the zeolitic crystalline structure accompanied by an increase in particle size of the prepared solids. New phases, Co3O4 and Co2SiO4, were

Zeinhom M. El-Bahy; Mohamed M. Mohamed; Farouk I. Zidan; Mohamed S. Thabet

2008-01-01

249

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

PubMed

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

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

2008-12-30

250

Esterification of free fatty acids using water-tolerable Amberlyst as a heterogeneous catalyst  

Microsoft Academic Search

To produce biodiesel from high free fatty acid (FFA) oils, the esterification characteristics of two kinds of heterogeneous acid catalysts, Amberlyst 15 and Amberlyst BD20, were compared. When the FFA contents of oils were 50.0 and 99.8wt%, the activity of Amberlyst 15 gradually decreased with recycling, whereas the activity of Amberlyst BD20 was maintained during recycling. The activity of Amberlyst

Ji-Yeon Park; Deog-Keun Kim; Jin-Suk Lee

2010-01-01

251

Esterification of maleic acid with ethanol over cation-exchange resin catalysts  

Microsoft Academic Search

Diethyl maleate is an important intermediate extensively used in the production of latex emulsion polymers, thermoplast and thermoset plastics. The current paper delineates the efficacy of several heterogeneous catalysts, such as Indion-170, Amberlyst-36, Amberlyst-15, Amberlite IRA 120, 20% DTP\\/K-10 (dodecatungstophosphoric acid supported on K-10 clay) in the esterification of maleic acid with ethanol at reflux. Amongst these Indion-170, Amberlyst-36, Amberlyst-15

G. D. Yadav; M. B Thathagar

2002-01-01

252

Support effect in hydrotreating catalysts: hydrogenation properties of molybdenum sulfide supported on ?-zeolites of various acidities  

Microsoft Academic Search

In order to better understand the role of the acidity of the support on the hydrogenation properties of a molybdenum sulfide phase, a ?-zeolite with a nominal Si\\/Al = 13.8 was partially (Si\\/Al = 15.0 and 18.7) and fully dealuminated (Si\\/Al ?800, no Brönsted acidity). To achieve a reasonable Mo loading with a high Mo dispersion, the Mo\\/? catalysts were prepared by

Claude-Emmanuel Hédoire; Catherine Louis; Anne Davidson; Michèle Breysse; Françoise Maugé; Michel Vrinat

2003-01-01

253

Long chain cellulose esters with very low DS obtained with non-acidic catalysts  

Microsoft Academic Search

Long-chain cellulose esters with very low degree of substitution (DS<0.3), useful for specialty applications, were obtained\\u000a by reaction with fatty acids (FAs) without solvent for cellulose. Non-acidic catalysts such as FA salts were used to limit\\u000a the cellulose degradation when subjected to reaction at high temperatures. The surfactant character of this type of molecules\\u000a was employed to create an emulsion

J. Peydecastaing; S. Girardeau; C. Vaca-Garcia; M. E. Borredon

2006-01-01

254

Preparation of ruthenium supported catalysts for wet air oxidation of p-hydroxybenzoic acid  

Microsoft Academic Search

Ru\\/TiO2 and Ru\\/ZrO2 catalysts were prepared by incipient-wetness method of sol-gel supports. They were characterized by means of nitrogen adsorption-desorption, X-ray diffraction (XRD) and transmission electron microscopy (TEM). Catalytic properties of the samples were determined in the wet air oxidation of p-hydroxybenzoic acid chosen as a model compound of olive oil wastewaters. The effect of the acid used for the

Mohamed Triki; Doan Pham Minh; Zouhaier Ksibi; Abdelhamid Ghorbel; Pierre Gallezot; Michèle Besson

2006-01-01

255

Development of molecular and solid catalysts for the direct low-temperature oxidation of methane to methanol.  

PubMed

The direct low-temperature oxidation of methane to methanol is demonstrated on a highly active homogeneous molecular catalyst system and on heterogeneous molecular catalysts based on polymeric materials possessing ligand motifs within the material structure. The N-(2-methylpropyl)-4,5-diazacarbazolyl-dichloro-platinum(II) complex reaches significantly higher activity compared to the well-known Periana system and allows first conclusions on electronic and structural requirements for high catalytic activity in this reaction. Interestingly, comparable activities could be achieved utilizing a platinum modified poly(benzimidazole) material, which demonstrates for the first time a solid catalyst with superior activity compared to the Periana system. Although the material shows platinum leaching, improved activity and altered electronic properties, compared to the conventional Periana system, support the proposed conclusions on structure-activity relationships. In comparison, platinum modified triazine-based catalysts show lower catalytic activity, but rather stable platinum coordination even after several catalytic cycles. Based on these systems, further development of improved solid catalysts for the direct low-temperature oxidation of methane to methanol is feasible. PMID:19780100

Palkovits, Regina; von Malotki, Christian; Baumgarten, Martin; Müllen, Klaus; Baltes, Christian; Antonietti, Markus; Kuhn, Pierre; Weber, Jens; Thomas, Arne; Schüth, Ferdi

2010-02-22

256

Deactivation of carbon supported palladium catalyst in direct formic acid fuel cell  

NASA Astrophysics Data System (ADS)

A new carbon black supported palladium catalyst for direct formic acid fuel cell applications has been prepared and characterized by X-ray diffraction. Bi-modal distribution of Pd crystallite sizes was observed. The average Pd size for crystallites in small size and large size ranges were about 2.7 nm and 11.2 nm, respectively. The initial activity of the catalyst in the oxidation of formic acid tested in a fuel cell was similar to a commercial well dispersed 20 wt.% Pd/Vulcan. The rates of the fuel cell power decay were measured for formic acid of two purities for various current loadings. The results showed that various mechanisms contribute to the decrease of cell power with time. In direct formic acid fuel cell (DFAFC) fed with a very pure HCOOH accumulation of CO 2 gas bubbles in anode catalyst layer is responsible for observed power decay. In DFAFC fed with a pure for analysis (p.a.) grade formic acid the formation of CO ads poison from the formic acid impurities is the main deactivation reason.

Miko?ajczuk, A.; Borodzinski, A.; Kedzierzawski, P.; Stobinski, L.; Mierzwa, B.; Dziura, R.

2011-07-01

257

Gibberellic acid production using different solid-state fermentation systems  

Microsoft Academic Search

Gibberellic acid production in liquid fermentation was compared with production of this compound in solid-state fermentation systems using cassava flour, sugar cane bagasse and low density polyurethane. Gibberella fujikuroi produced 23 mg of gibberellin\\/ml in 120h of liquid fermentation. Solid-state fermentation on bagasse showed excellent growth but presented gibberellin extraction problems. Very low production and growth was observed in solid-state

A. Tomasini; C. Fajardo; J. Barrios-Gonza´lez

1997-01-01

258

Hydrogenation of Biofuels with Formic Acid over a Palladium-Based Ternary Catalyst with Two Types of Active Sites.  

PubMed

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

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

2014-06-01

259

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

SciTech Connect

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

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

1988-01-01

260

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

SciTech Connect

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

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

1988-01-01

261

Mechanism of hydrodenitrogenation (Part 4) infrared spectroscopy of acidic molybdena catalysts  

SciTech Connect

Mo oxide catalysts supported over a complete series of silica-aluminas have been characterized in the oxidic and reduced states, by means of total acidity measurements and by infrared spectroscopy. Ammonia chemisorption was used to titrate the total acidity of the catalysts, and IR absorption of adsorbed pyridine to distinguish Bronsted from Lewis acid sites. The formation of new acidity upon deposition of molybdena on silica-alumina supports was then explained on the basis of a simple surface model. The new acidity is of both Lewis and Bronsted type, the preponderance of one over the other depending on support composition, as well as loading and state of oxidation of Mo. High-alumina supports and low Mo loading favor dispersed Mo species, in particular bidentate and monodentate di-oxo Mo species. The latter is responsible for the new Bronsted acidity. Coordinative unsaturation of polymolybdates is responsible for the new Lewis acidity, which is increased upon reduction of Mo. High-silica supports favor monodentate species (high Bronsted acidity) up to 4 wt % MoO{sub 3}. Beyond that, polymolybdates species and Lewis acidity predominate. 7 refs., 4 figs.

Miranda, R.

1990-01-01

262

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

263

Efficiencies of acid catalysts in the hydrolysis of lignocellulosic biomass over a range of combined severity factors  

Microsoft Academic Search

Dicarboxylic organic acids have properties that differ from those of sulfuric acid during hydrolysis of lignocellulose. To investigate the effects of different acid catalysts on the hydrolysis and degradation of biomass compounds over a range of thermochemical pretreatments, maleic, oxalic and sulfuric acids were each used at the same combined severity factor (CSF) values during hydrolysis. Xylose and glucose concentrations

Jae-Won Lee; Thomas W. Jeffries

2011-01-01

264

Solid–liquid surface energy of pivalic acid  

Microsoft Academic Search

The Gibbs–Thomson coefficient and the solid–liquid surface energy for pivalic acid have been measured by a direct method. The grain boundary energy of the pivalic acid also has been calculated from the observed grain boundary groove shapes.

B. Bayender; N Mara?li; E Çadirli; H ?i?man; M Gündüz

1998-01-01

265

Physicochemical pretreatments and hydrolysis of furfural residues via carbon-based sulfonated solid acid.  

PubMed

Potential commercial physicochemical pretreatment methods, NaOH/microwave and NaOH/ultrasound were developed, and the carbon-based sulfonated solid acid catalysts were prepared for furfural residues conversion into reducing sugars. After the two optimum pretreatments, both the content of cellulose increased (74.03%, 72.28%, respectively) and the content of hemicellulose (94.11%, 94.17% of removal rate, respectively) and lignin (91.75%, 92.09% of removal rate, respectively) decreased in furfural residues. The reducing sugar yields of furfural residues with the two physicochemical pretreatments on coal tar-based solid acid reached 33.94% and 33.13%, respectively, higher than that pretreated via NaOH alone (27%) and comparable to that pretreated via NaOH/H2O2 (35.67%). The XRD patterns, IR spectra and SEM images show microwave and ultrasound improve the pretreatment effect. The results demonstrate the carbon-based sulfonated solid acids and the physicochemical pretreatments are green, effective, low-cost for furfural residues conversion. PMID:24508657

Ma, Bao Jun; Sun, Yuan; Lin, Ke Ying; Li, Bing; Liu, Wan Yi

2014-03-01

266

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

267

A Modified Solid-State Reduction Method to Prepare Supported Platinum Nanoparticle Catalysts for Low Temperature Fuel Cell Application  

SciTech Connect

A modified solid state reduction (SSR) method, by which the platinum salt is reduced into platinum nanoparticles by sodium formate in solid state and under low temperature (below 180 C) conditions, is introduced here. The high performance catalysts based on carbon nanotubes (CNTs) supported platinum and platinum promoted by Mo (VI) and Si (IV) were prepared successfully by this method. The catalysts, with small particle size and uniform distribution were active toward the electrooxidation reaction of methanol. Among a few catalysts promoted by silicon, molybdenum and tungsten elements, catalysts co-promoted by silicon and molybdenum elements shows best performance. The particle size of promoted Pt/CNTs, calculated from XRD patterns, is small as 3.0 1.5 nm, and the results of transmission electron microscopy (TEM) revealed that the distribution of particle size is uniform. In comparison with the liquid-state synthesis, the advantages of SSR method include its environmental benefits due to less water usage and significantly reduced pollutants generation, as well as its suitability for large scale preparation.

Hu, Michael Z. [ORNL

2009-01-01

268

Hydrogenation of succinic acid to 1,4-butanediol over rhenium catalyst supported on copper-containing mesoporous carbon.  

PubMed

Copper-containing mesoporous carbon (Cu-MC) was prepared by a single-step surfactant-templating method. For comparison, copper-impregnated mesoporous carbon (Cu/MC) was also prepared by a surfactant-templating method and a subsequent impregnation method. Rhenium catalysts supported on copper-containing mesoporous carbon and copper-impregnated mesoporous carbon (Re/Cu-MC and Re/Cu/MC, respectively) were then prepared by an incipient wetness method, and they were applied to the liquid-phase hydrogenation of succinic acid to 1,4-butanediol (BDO). It was observed that copper in the Re/Cu-MC catalyst was well incorporated into carbon framework, resulting in higher surface area and larger pore volume than those of Re/Cu/MC catalyst. Therefore, Re/Cu-MC catalyst showed higher copper dispersion than Re/Cu/MC catalyst, although both catalysts retained the same amounts of copper and rhenium. In the liquid-phase hydrogenation of succinic acid to BDO, Re/Cu-MC catalyst showed a better catalytic activity than Re/Cu/MC catalyst. Fine dispersion of copper in the Re/Cu-MC catalyst was responsible for its enhanced catalytic activity. PMID:24245272

Hong, Ung Gi; Park, Hai Woong; Lee, Joongwon; Hwang, Sunhwan; Kwak, Jimin; Yi, Jongheop; Song, In Kyu

2013-11-01

269

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

PubMed Central

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

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

2014-01-01

270

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

Microsoft Academic Search

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

Boris E. Martin

2007-01-01

271

Calcium oxide as a solid base catalyst for transesterification of soybean oil and its application to biodiesel production  

Microsoft Academic Search

In order to study solid base catalyst for biodiesel production with environmental benignity, transesterification of edible soybean oil with refluxing methanol was carried out in the presence of calcium oxide (CaO), -hydroxide (Ca(OH)2), or -carbonate (CaCO3). At 1h of reaction time, yield of FAME was 93% for CaO, 12% for Ca(OH)2, and 0% for CaCO3. Under the same reacting condition,

Masato Kouzu; Takekazu Kasuno; Masahiko Tajika; Yoshikazu Sugimoto; Shinya Yamanaka; Jusuke Hidaka

2008-01-01

272

Synthesis of bis(2-ethylhexyl) phthalate over methane sulfonic acid catalyst. Kinetic investigations  

Microsoft Academic Search

The kinetic model for the synthesis of bis(2-ethylhexyl) phthalate from phthalic anhydride and 2-ethylhexanol in the presence\\u000a of methane sulfonic acid as a catalyst has been derived, based on the investigation carried out in an isothermal, semibatch\\u000a reactor. The first step, the formation of mono(2-ethylhexyl) phthalate, is very fast and irreversible. The second step, the\\u000a esterification of monoester with 2-ethylhexanol,

Jerzy Skrzypek; Maria Lachowska; Maria Kulawska; Henryk Moroz

2008-01-01

273

Influence of the carrier on steam reforming of acetic acid over Ru-based catalysts  

Microsoft Academic Search

The reaction of steam reforming of acetic acid (HAc), a model compound of pyrolysis-oil, over ruthenium catalysts supported on Al2O3 and MgO\\/Al2O3 carriers has been investigated employing transient and steady-state techniques. Main objective is the establishment of the reaction network over a wide temperature range and the elucidation of the role of MgO on intrinsic catalytic activity. It has been

Aristides C. Basagiannis; Xenophon E. Verykios

2008-01-01

274

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

Microsoft Academic Search

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

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

275

Dehydration of xylose into furfural over micro-mesoporous sulfonic acid catalysts  

Microsoft Academic Search

Surfactant-templated micro-mesoporous silicas possessing sulfonic acid groups (SAGs) have been prepared, characterized, and tested as catalysts in the dehydration of d-xylose to furfural. All of the materials possessed catalytic activity. In general, selectivity to furfural was lower for a poorly ordered microporous hybrid material, prepared via the co-condensation of (3-mercaptopropyl)trimethoxysilane with bis(trimethoxysilylethyl)benzene, than for mesoporous MCM-41 silica anchored with SAGs

Ana S. Dias; Martyn Pillinger; Anabela A. Valente

2005-01-01

276

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

277

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.

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

2012-01-01

278

The influence of acidic and alkaline precursors on Pt Ru\\/C catalyst performance for a direct methanol fuel cell  

Microsoft Academic Search

This research aims to increase the activity of platinum–ruthenium alloy (PtRu\\/C) catalysts for methanol electrooxidation. The direct methanol fuel cell (DMFC) anodic PtRu\\/C catalysts were prepared from acidic and alkaline Pt(NH3)2(NO2)2 solutions as Pt precursors, respectively, and with the same acidic Ru compound but without Cl? ion as the Ru precursor by thermal reduction. The phase structures, lattice parameters, particle

Zhen-Bo Wang; Ge-Ping Yin; Peng-Fei Shi

2007-01-01

279

Autothermal reforming of methane over Ni catalysts supported over CaO–CeO 2–ZrO 2 solid solution  

Microsoft Academic Search

Ni catalysts supported on various solid solutions of ZrO2 with alkaline earth oxide and\\/or rare earth oxide were synthesized. The catalytic activities were compared for partial oxidation of methane and autothermal reforming of methane. For partial oxidation of methane, the Ni catalyst supported on a CaO–ZrO2 solid solution showed a high activity. Incorporation of CaO in the ZrO2 matrix was

Tatsuya Takeguchi; Shin-Nosuke Furukawa; Masashi Inoue; Koichi Eguchi

2003-01-01

280

Enhancing the efficiency and regioselectivity of p450 oxidation catalysts by unnatural amino Acid mutagenesis.  

PubMed

The development of effective strategies for modulating the reactivity and selectivity of cytochrome P450 enzymes represents a key step toward expediting the use of these biocatalysts for synthetic applications. We have investigated the potential of unnatural amino acid mutagenesis to aid efforts in this direction. Four unnatural amino acids with diverse aromatic side chains were incorporated at 11 active-site positions of a substrate-promiscuous CYP102A1 variant. The resulting "uP450s" were then tested for their catalytic activity and regioselectivity in the oxidation of two representative substrates: a small-molecule drug and a natural product. Large shifts in regioselectivity resulted from these single mutations, and in particular, for para-acetyl-Phe substitutions at positions close to the heme cofactor. Screening this mini library of uP450s enabled us to identify P450 catalysts for the selective hydroxylation of four aliphatic positions in the target substrates, including a C(sp(3) )?H site not oxidized by the parent enzyme. Furthermore, we discovered a general activity-enhancing effect of active-site substitutions involving the unnatural amino acid para-amino-Phe, which resulted in P450 catalysts capable of supporting the highest total turnover number reported to date on a complex molecule (34?650). The functional changes induced by the unnatural amino acids could not be reproduced by any of the 20 natural amino acids. This study thus demonstrates that unnatural amino acid mutagenesis constitutes a promising new strategy for improving the catalytic activity and regioselectivity of P450 oxidation catalysts. PMID:24692265

Kolev, Joshua N; Zaengle, Jacqueline M; Ravikumar, Rajesh; Fasan, Rudi

2014-05-01

281

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

282

Activity and stability of pyrolyzed iron ethylenediaminetetraacetic acid as cathode catalyst in microbial fuel cells.  

PubMed

A low-cost and effective iron-chelated catalyst was developed as an electrocatalyst for the oxygen reduction reaction (ORR) in microbial fuel cells (MFCs). The catalyst was prepared by pyrolyzing carbon mixed iron-chelated ethylenediaminetetraacetic acid (PFeEDTA/C) in an argon atmosphere. Cyclic voltammetry measurements showed that PFeEDTA/C had a high catalytic activity for ORR. The MFC with a PFeEDTA/C cathode produced a maximum power density of 1122 mW/m(2), which was close to that with a Pt/C cathode (1166 mW/m(2)). The PFeEDTA/C was stable during an operation period of 31 days. Based on X-ray diffraction and X-ray photoelectron spectroscopy measurements, quaternary-N modified with iron might be the active site for the oxygen reduction reaction. The total cost of a PFeEDTA/C catalyst was much lower than that of a Pt catalyst. Thus, PFeEDTA/C can be a good alternative to Pt in MFC practical applications. PMID:21324675

Wang, Li; Liang, Peng; Zhang, Jian; Huang, Xia

2011-04-01

283

Aluminum chloride as a solid is not a strong Lewis acid.  

PubMed

Aluminum chloride is used extensively as Lewis acid catalyst in a variety of industrial processes, including Friedel-Crafts and Cl/F exchange reactions. There is a common misconception that pure AlCl3 is itself a Lewis acid. In the current study, we use experimental and computational methods to investigate the surface structure and catalytic properties of solid AlCl3. The catalytic activity of AlCl3 for two halide isomerization reactions is studied and compared with different AlF3 phases. It is shown that pure solid AlCl3 does not catalyze these reactions. The (001) surface of crystalline AlCl(3) is the natural cleavage plane and its structure is predicted via first principles calculations. The chlorine ions in the outermost layer of the material mask the Al3+ ions from the external gas phase. Hence, the experimentally found catalytic properties of pure solid AlCl3 are supported by the predicted surface structure of AlCl3. PMID:16623514

Murthy, J Krishna; Gross, Udo; Rüdiger, Stephan; Rao, V Venkat; Kumar, V Vijaya; Wander, A; Bailey, C L; Harrison, N M; Kemnitz, Erhard

2006-04-27

284

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

285

Process optimization and performance evaluation on sequential ionic liquid dissolution-solid acid saccharification of sago waste.  

PubMed

The production of reducing sugars from sago waste via sequential ionic liquid dissolution-solid acid saccharification was optimized in this study. Ionic liquid dissolution of sago waste with 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) was conducted prior to the solid acid saccharification with Amberlyst 15 (A15). The effect of time, temperature and substrate loading during dissolution reaction; and the effect of time, temperature and catalyst loading during saccharification reaction were examined by applying central composite design (CCD) separately. Both dissolution and saccharification reactions were respectively modeled into quadratic polynomial equations with good predictive accuracies. A high reducing sugars yield of 98.3% was obtained under the optimized conditions, i.e. dissolution at 1.75h, 160°C, 1.5% substrate loading, and saccharification at 0.5h, 130°C, 4% catalyst loading. From comparison studies of different saccharification schemes, the sequential ionic liquid dissolution-solid acid saccharification has proven to be a potential method in reducing sugars production from the lignocellulosic biomass. PMID:23280179

Lee, Kiat Moon; Ngoh, Gek Cheng; Chua, Adeline Seak May

2013-02-01

286

Electrocatalytic performance of carbon supported Pd catalyst modified with Keggin type of Sn-substituted polyoxometalatate for formic acid oxidization  

NASA Astrophysics Data System (ADS)

The carbon supported Pd(Pd/C) catalyst modified by the new polyoxometalate with Keggin type of Sn-Substituted structure K7CoIIW11O39SnIVOH (Pd/C-K7) catalyst is prepared with the simple impregnation-reduction method. This work investigates the effects of Pd/C-K7 catalyst for direct formic acid fuel cells (DFAFCs). The morphology, structure, size and composition of the Pd/C-K7 catalyst are characterized by transmission electron microscopy (TEM) energy dispersive spectrum (EDS), X-ray diffraction (XRD). Cyclic voltammetry, chronoamperometry and CO-stripping voltammetry tests demonstrate the Pd/C-K7 catalyst have higher electrocatalytic activity, better electrochemical stability, and higher resistance to CO poisoning over the unmodified Pd/C catalyst for the formic acid oxidation reaction (FAOR) owing to K7CoIIW11O39SnIVOH with Keggin structure. Therefore, the Pd/C-K7 catalyst could be used as the excellent anodic catalyst in DFAFCs.

Ji, Yun; Shen, Liping; Wang, Anxing; Wu, Min; Tang, Yawen; Chen, Yu; Lu, Tianhong

287

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

288

Transient methods for in situ NMR of reactions on solid catalysts using temperature jumps  

SciTech Connect

Two methods for carrying out magic angle spinning (MAS) NMR experiments with temperature jumps were evaluated for their suitability for studies of rapid chemical reactions in situ. Temperature profiles, both spatial and temporal, were determined through the use of {sup 207}Pb chemical shift thermometry and melting transitions. Our inductive heating experiments were performed using an unmodified double resonance, single coil MAS probe by injecting a continuous signal 130 kHz off-resonance from the {sup 1}H frequency into the decoupler channel. While the spectrometer used was generally capable of performing continuous wave (CW) heating experiments with 100 W, the standard probe design limited CW heating power to nearly 20 W; thus, the results reported here understate the potential of the method. Using a combination of thermometry techniques, it was possible to establish 30-60-s heating regiments for in situ {sup 1}H and {sup 13}C NMR studies of the reactions of methanol on the acidic zeolite catalyst HZSM-5. Application of 18 W at 199.7 MHz to a 5-mm-o.d. Pt-coated zirconia rotor heated the samples from an initial value of 298 K to a final state fully equilibrated at 623 K in 30 s or less. Single-shot {sup 1}H spectra acquired every 3 s during the dynamic part of the experiment and {sup 13}C Spectra acquired after quenches to 298 K were consistent with established features of the catalytic reaction mechanism. 29 refs., 10 figs.

Ferguson, D.B.; Haw, J.F. [Texas A& M Univ., College Station, TX (United States)

1995-09-15

289

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

Microsoft Academic Search

Biodiesel could be synthesized using Brønsted acidic ionic liquid N-methyl-2-pyrrolidonium methyl sulfonate ([NMP][CH3SO3]) as a catalyst, specially with free long-chain fatty acids or their mixtures, as well as with low-molecular weight alcohols as substrates. This catalyst showed good catalytic and reusable performance under mild conditions and without any additional organic solvent. The ionic liquid could be reused eight times after

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

2009-01-01

290

Transient optical absorption spectra in pulse irradiated solid amino acids  

Microsoft Academic Search

A preliminary pulse radiolytic study is reported on transient optical absorption spectra in solid amino acids. Spectra have been obtained by improved Cherenkov Light Self-absorption Method applied during 5.5 s pulses of 10 or 13 MeV linac electrons. Amino acids exhibit a very different type of behaviour: from lack of absorption signal (at the present sensitivity of the system) to

Z. P. Zagórski; Z. Tomasi?ski

1990-01-01

291

Microbial production of gallic acid by modified solid state fermentation  

Microsoft Academic Search

  Bioconversion of tannin to gallic acid from powder of teri pod (Caesalpinia digyna) cover was achieved by the locally isolated fungus, Rhizopus oryzae, in a bioreactor with a perforated float for carrying solid substrate and induced inoculum. Modified Czapek-Dox medium, put\\u000a beneath the perforated float, with 2% tannic acid at pH 4.5, temperature 32°C, 93% relative humidity, incubated for 3

B Kar; R Banerjee; B C Bhattacharyya

1999-01-01

292

Esterification of free fatty acids using water-tolerable Amberlyst as a heterogeneous catalyst.  

PubMed

To produce biodiesel from high free fatty acid (FFA) oils, the esterification characteristics of two kinds of heterogeneous acid catalysts, Amberlyst 15 and Amberlyst BD20, were compared. When the FFA contents of oils were 50.0 and 99.8 wt%, the activity of Amberlyst 15 gradually decreased with recycling, whereas the activity of Amberlyst BD20 was maintained during recycling. The activity of Amberlyst 15 was inhibited by the water produced during the esterification process, but the activity of Amberlyst BD20 was not similarly affected by water. In images obtained with a scanning electron microscope (SEM), many pores were seen within the Amberlyst 15 catalyst, whereas Amberlyst BD20 showed few pores. Despite the fact that the pores of the catalyst play a role in increasing the number of active sites, Amberlyst BD20, which had fewer pores, was deemed to have more desirable performance in reducing the inhibition by water of the esterification of high FFA oils. PMID:19362818

Park, Ji-Yeon; Kim, Deog-Keun; Lee, Jin-Suk

2010-01-01

293

Graphene-Based Non-Noble-Metal Catalysts for Oxygen Reduction Reaction in Acid  

SciTech Connect

Non-noble-metal catalysts based on Fe-N-C moieties have shown promising oxygen reduction reaction (ORR) activity in proton exchange membrane fuel cells (PEMFCs). In this study, we report a facile method to prepare a Fe-N-C catalyst based on modified graphene (Fe-N-rGO) from heat treatment of a mixture of Fe salt, graphitic carbon nitride (g-C{sub 3}N{sub 4}), and chemically reduced graphene (rGO). The Fe-N-rGO catalyst was found to have pyridinic N-dominant heterocyclic N (40% atomic concentration among all N components) on the surface and have an average Fe coordination of {approx}3 N (Fe-N{sub 3,average}) in bulk. Rotating disk electrode measurements revealed that Fe-N-rGO had high mass activity in acid and exhibited high stability at 0.5 V at 80 C in acid over 70 h, which was correlated to low H{sub 2}O{sub 2} production shown from rotating ring disk electrode measurements.

H Byon; J Suntivich; Y Shao-Horn

2011-12-31

294

Characterization of iron counter-ion environment in bulk and supported phosphomolybdic acid based catalysts  

NASA Astrophysics Data System (ADS)

Extended X-ray absorption fine structure (EXAFS) was used to characterize the environment of iron counter-cations in Keggin type phosphomolybdic compounds used as catalysts for oxidation reactions. Iron doped compounds corresponding to bulk acid and to acid supported on the cesium salt were prepared and studied. Iron formed hexa-hydrated complex of both Fe3+ and Fe2+ in the bulk acid, whereas it was present as Fe(OH)2+ hydroxy-cations in the acid supported on the cesium salt. Upon heating the hexa-hydrated complex lost one molecule of water to bind to the Keggin anion through a terminal oxygen. (Fe O Mo bond). The environment of the iron hydroxy-cation changed upon heating while its closer coordination append to remained unchanged.

Huynh, Q.; Millet, J. M. M.

2005-05-01

295

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

296

Citric acid production by solid state fermentation using sugarcane bagasse  

Microsoft Academic Search

A solid state fermentation (SSF) method was used to produce citric acid by Aspergillus niger DS 1 using sugarcane bagasse as a carrier and sucrose or molasses based medium as a moistening agent. Initially bagasse and wheat bran were compared as carrier. Bagasse was the most suitable carrier, as it did not show agglomeration after moistening with medium, resulting in

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

2003-01-01

297

Evolution of solid phase homochirality for a proteinogenic amino acid.  

PubMed

The inexorable evolution of solid-phase single chirality is demonstrated for the first time for a proteinogenic amino acid. Enantioenrichment is observed both under attrition-enhanced conditions and without the aid of particle grinding. Differences in the form of the conversion profiles for the process under the two sets of conditions provide suggestions concerning the mechanism of the transformation. PMID:18954052

Viedma, Cristobal; Ortiz, José E; de Torres, Trinidad; Izumi, Toshiko; Blackmond, Donna G

2008-11-19

298

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

299

Synthesis and thermal energy storage characteristics of polystyrene- graft-palmitic acid copolymers as solid–solid phase change materials  

Microsoft Academic Search

A series of polystyrene graft palmitic acid (PA) copolymers as novel polymeric solid–solid phase change materials (PCMs) were synthesized. In solid–solid PCMs, polystyrene is the skeleton and PA is a functional side chain that stores and releases heat during its phase transition process. The heat storage of copolymers is due to phase transition between crystalline and amorphous states of the

Ahmet Sar?; Cemil Alkan; Alper Biçer; Ali Karaipekli

2011-01-01

300

CALCULATION OF THE SURFACE AREAS AND THE ACID STRENGTH OF NiSO4, CuSO4 AND CoSO4.H20 AND THE USE OF THESE CATALYSTS ON DEHYDRATION OF SOME ALCOHOLS  

Microsoft Academic Search

SUMMARY In this study; the surfaces of the catalysts were examined by electron microscope and their surface areas were calculated with gas adsorption method as a unit of m2g-1. In addition, the acid strength on solid catalysts (NiSO4, CuSO4, CoSO4.H2O) was determined by Hammett indicator adsorption method and also, dehydration reactions of 2,6-dimethyl-4-heptanol, 3,7-dimethyl-3-octanol and 2-octanol were investigated with the

MUSTAFA RIDVANLAR; ÜLKÜ OYMAN

301

The use of solid supports to generate nucleic acid carriers.  

PubMed

Nucleic acids are the foundation stone of all cellular processes. Consequently, the use of DNA or RNA to treat genetic and acquired disorders (so called gene therapy) offers enormous potential benefits. The restitution of defective genes or the suppression of malignant genes could target a range of diseases, including cancers, inherited diseases (cystic fibrosis, muscular dystrophy, etc.), and viral infections. However, this strategy has a major barrier: the size and charge of nucleic acids largely restricts their transit into eukaryotic cells. Potential strategies to solve this problem include the use of a variety of natural and synthetic nucleic acid carriers. Driven by the aim and ambition of translating this promising therapeutic approach into the clinic, researchers have been actively developing advanced delivery systems for nucleic acids for more than 20 years. A decade ago we began our investigations of solid-phase techniques to construct families of novel nucleic acid carriers for transfection. We envisaged that the solid-phase synthesis of polycationic dendrimers and derivatized polyamimes would offer distinct advantages over solution phase techniques. Notably in solid phase synthesis we could take advantage of mass action and streamlined purification procedures, while simplifying the handling of compounds with high polarities and plurality of functional groups. Parallel synthesis methods would also allow rapid access to libraries of compounds with improved purities and yields over comparable solution methodologies and facilitate the development of structure activity relationships. We also twisted the concept of the solid-phase support on its head: we devised miniaturized solid supports that provided an innovative cell delivery vehicle in their own right, carrying covalently conjugated cargos (biomolecules) into cells. In this Account, we summarize the main outcomes of this series of chemically related projects. PMID:22390230

Unciti-Broceta, Asier; Díaz-Mochón, Juan José; Sánchez-Martín, Rosario M; Bradley, Mark

2012-07-17

302

Tungstic acid functionalized mesoporous SBA-15: a novel heterogeneous catalyst for facile one-pot synthesis of 2-amino-4H-chromenes in aqueous medium.  

PubMed

A new highly ordered mesoporous tungstic acid functionalized SBA-15, TAFMC-1 has been synthesized via post-synthesis modification of mesoporous SBA-15 with (3-chloropropyl) triethoxysilane followed by substitution reaction of chlorine atom of the 3-chloropropyl group by tungstic acid group under refluxing conditions in n-hexane. The tungstic acid functionalized mesoporous silica material has been characterized by using small angle powder X-ray diffraction, N2 sorption, HR-TEM, FE-SEM, FT-IR and solid state MAS NMR studies. TAFMC-1 catalyzes the facile one-pot catalytic three-component condensation reaction of resorcinol, aromatic aldehyde and malononitrile for the synthesis of a diverse range of 2-amino-4H-chromenes in aqueous medium. This heterogeneous catalyst can be recycled very efficiently for six consecutive reaction cycles without significant loss of catalytic activity. PMID:23760225

Kundu, Sudipta K; Mondal, John; Bhaumik, Asim

2013-08-01

303

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

304

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

PubMed

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. PMID:24463793

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

2014-01-01

305

Solid-state characterization of mefenamic acid.  

PubMed

The purpose of this study was to characterize mefenamic acid (MA) from commercial samples and samples crystallized from different solvents. Various techniques used for characterization included microscopy (hot stage microscopy, scanning electron microscopy), intrinsic dissolution rate, differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy and powder X-ray diffractometry (pXRD). The commercial samples varied in their crystal habit, thermal behavior, and intrinsic dissolution rate. It was found that the commercial samples were polymorphic Form I, which converted to Form II on heating in a DSC pan. Similarly, compression in an intrinsic dissolution rate (IDR) press resulted in the conversion of Form I to Form II. On the other hand, the samples recrystallized from different solvents under varying conditions yielded different crystal habits. Stirring and degree of supersaturation significantly influenced the crystal habit in all the solvents used in the study. Samples crystallized from ethanol and tetrahydrofuran yielded Form I, which behaved similarly to the commercial samples (M1 and M3). Recrystallization from ethyl acetate at a fast cooling rate yielded Form I, which on melting crystallized to Form II. The form I crystallized from ethyl acetate by fast cooling converted partially to form II on storing at ambient conditions. Forms I and II of MA were enantiotropically related. The results demonstrate the variable material characteristics of the commercial samples of MA and the influence of the crystallizing conditions on the formation of the polymorphs. PMID:14999737

Panchagnula, Ramesh; Sundaramurthy, Prakash; Pillai, Omathanu; Agrawal, Shrutidevi; Raj, Yasvanth Ashok

2004-04-01

306

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

307

Preparation and properties of new acid catalysts obtained by grafting alkoxides and derivatives on the most common supports. Part II: Grafting zirconium and silicon alkoxides on ?-alumina  

Microsoft Academic Search

In this work, the preparation and properties of the acid catalysts obtained by grafting zirconium and silicon alkoxides and zirconium-sulfated alkoxide on ?-alumina were studied. The catalysts prepared were examined with electrochemical techniques to evaluate the hydroxyl density, the ZPC (zero point charge) and the intrinsic surface ionization constants. The catalysts were also submitted to TPD (temperature-programmed desorption) analysis using

P Iengo; M Di Serio; V Solinas; D Gazzoli; G Salvio; E Santacesaria

1998-01-01

308

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

309

Photoassisted Fenton mineralisation of Acid Violet 7 by heterogeneous Fe(III)–Al 2O 3 catalyst  

Microsoft Academic Search

Photoassisted Fenton mineralisation of an azo dye Acid Violet 7 was studied in detail using a Fe(III) loaded Al2O3 as a heterogeneous catalyst in the presence of H2O2 and UV-A light. The catalyst ferrioxalate–Al2O3 is more efficient than ferricnitrate–Al2O3. 35% Fe3+ loaded Al2O3 shows maximum efficiency in the degradation. The effects of reaction parameters such as catalyst loading, H2O2 concentration,

Inbasekaran Muthuvel; Meenakshisundaram Swaminathan

2007-01-01

310

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

PubMed

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

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

2013-09-16

311

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

PubMed

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

Pozzi, Gianluca; Fish, Richard H

2012-01-01

312

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

PubMed

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

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

2013-05-01

313

Acid catalysts based on Cu/Ru alumina: Conversion of butyraldehyde to dibutyl ether  

SciTech Connect

A system made by combining two nonalloying metals, ruthenium and copper, using alumina as the oxide support was studied. This bimetallic supported catalyst has been used mainly in hydrogenoloysis, dehydrogenation, and oxidation reactions of hydrocarbons. The preparation of such materials has been proposed to effect the selectivity and activity of a highly active metal by inclusions of a second less active metal. The samples were characterized by electron paramagnetic resonance spectrometry (EPR), X-ray diffraction (XRD), surface area, and surface acidities. The techniques EPR and XRD are ideal for studying the electronic and structural changes of the samples at different temperatures and concentrations. The primary reaction involved in this study was the hydrogenation of an aldehyde to the corresponding alcohol. A secondary reaction occurred as well. The acid catalyzed, substitution or bimolecular dehydration of the alcohol to the dibutyl ether was observed under certain catalytic conditions. These catalysts appeared to act as acid/base. Therefore this reaction to produce the ether is of special importance. A correlation between the electronic, structural and catalytic properties has been made to understand molecular processes` role in catalytic phenomena. 44 refs., 6 figs., 5 tabs.

Jansen, S.; Palmieri, M.; Gomez, M. [Temple Univ., Philadelphia, PA (United States)] [Temple Univ., Philadelphia, PA (United States); Lawrence, S. [Saginaw Valley State Univ., University Center, MI (United States)] [Saginaw Valley State Univ., University Center, MI (United States)

1996-10-01

314

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

PubMed

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

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

2014-06-19

315

A Mild and Efficient Chemoselective Tetrahydropyranylation of Alcohols Using Bronsted Acidic Ionic Liquid as Catalyst Under Solvent-Free Conditions  

Microsoft Academic Search

A straightforward and efficient method for preparation of morpholinium bisulfate ([mroH] HSO4) as a novel acidic IL is reported. The application of this efficient and inexpensive acidic ionic liquid catalyst for tetrahydropyranylation of alcohols under mild and solvent-free conditions at room was investigated.

Abdol R. Hajipour; Zahra. Nasresfahani

2011-01-01

316

Aromatic Compounds Mannich Reaction Using Economical Acidic Ionic Liquids Based on Morpholinium Salts as Dual Solvent-Catalysts  

Microsoft Academic Search

Economical acidic ionic liquids containing an alkanesulfonic acid group in a morpholinium cation were found to be effective catalysts for the Mannich reactions of various kinds of aromatic aldehydes, acetophenone and aromatic amines at mild reaction conditions. The satisfactory results were obtained with short reaction time, good yields of the Mannich bases and simplicity in the experimental procedure. These ionic

Caibo Yue

2010-01-01

317

Mild and Efficient Chemoselective Tetrahydropyranylation of Alcohols Using Brønsted Acidic Ionic Liquid as Catalyst Under Solvent-Free Conditions  

Microsoft Academic Search

A straightforward and efficient method for preparation of morpholinium bisulfate ([mroH]HSO4) as a novel acidic ionic liquid is reported. The application of this efficient and inexpensive acidic ionic liquid catalyst for tetrahydropyranylation of alcohols under mild and solvent-free conditions at room was investigated.

Abdol R. Hajipour; Zahra Nasresfahani

2012-01-01

318

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

319

Intrinsic kinetics of the gas–solid Fischer–Tropsch and water gas shift reactions over a precipitated iron catalyst  

Microsoft Academic Search

The kinetics of the gas–solid Fischer–Tropsch synthesis over a commercial Fe–Cu–K–SiO2 catalyst was studied in a continuous spinning basket reactor. Experimental conditions were varied as follows: reactor pressure of 0.8–4.0MPa, H2\\/CO feed ratio of 0.25–4.0, and space velocity of 0.5–2.0×10?3Nm3kgcat?1s?1 at a constant temperature of 523K. A number of Langmuir–Hinshelwood–Hougen–Watson type rate equations were derived on the basis of a

Gerard P. van der Laan; Antonie A. C. M. Beenackers

2000-01-01

320

Characterization of V2O5-AlPO4 catalysts by 51V and 1H magic-angle spinning solid-state nuclear magnetic resonance spectroscopy.  

PubMed

Amorphous aluminum orthophosphate is used as a carrier for preparing a series of V2O5-AlPO4 catalysts with varying vanadia content. The catalysts were characterized by solid-state 51V and 1H magic-angle spinning nuclear magnetic resonance (MAS NMR), electron spin resonance (ESR) and X-ray diffraction (XRD). The XRD patterns of the catalysts remained amorphous at all loadings studied. 51V Solid-state NMR spectra revealed the presence of V2O5 microcrystallites at higher vanadia loadings. The 1H MAS NMR spectra of the catalysts showed a maximum consumption of support hydroxyl groups at 6 wt.-% V2O5 indicating the completion of a monolayer at this composition. PMID:7894983

Lakshmi, L J; Srinivas, S T; Rao, P K; Nosov, A V; Lapina, O B; Mastikhin, V M

1995-01-01

321

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

322

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

323

Liquid Hydrofluoric Acid Sorption Using Solid Media - Part 1  

Microsoft Academic Search

The conversion of the uranium hexafluoride (UFâ) which is removed from the Molten Salt Reactor Experiment (MSRE), into a stable oxide for long-term storage will produce a significant amount of slightly contaminated, concentrated aqueous hydrofluoric acid (HF). Sin&the handling of this HF is complicated and dangerous, it was decided to transform it into a stable solid fluoride (e.g., CaFâ, AlFâ,

Osborne

2000-01-01

324

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

PubMed

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

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

2013-03-13

325

Carbon supported platinum catalysts for catalytic wet air oxidation of refractory carboxylic acids  

Microsoft Academic Search

Carbon supported platinum (1% wt) catalysts were prepared by the incipient wetness impregnation method and by organometallic chemical vapor deposition. Catalyst characterization was carried out by means of adsorption and thermogravimetric techniques, and by electron microscopy. The catalyst with higher metal dispersion was produced by incipient wetness impregnation. The catalysts were tested in the catalytic wet air oxidation (200°C and

H. T. Gomes; Ph. Serp; Ph. Kalck; J. L. Figueiredo; J. L. Faria

2005-01-01

326

Polyethylene glycol immobilized on silica gel as a new solid–liquid phase-transfer catalyst for regioselective azidolysis of epoxides in water: An efficient route to 1,2-azido alcohols  

Microsoft Academic Search

Polyethylene glycol, a polymer widely used for biomedical applications and in supported synthesis, was easily immobilized on silica gel and used as a new solid–liquid phase-transfer catalyst. It is proved to be an efficient heterogeneous catalyst for regioselective ring opening of epoxide by azide ion in water to give azidohydrine in excellent yield under mild reaction conditions. The polymeric catalyst

Ali-Reza Kiasat; Maryam Zayadi

2008-01-01

327

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

PubMed

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

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

2011-07-01

328

Three-Phase Catalytic System of H2 O, 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][Tf2 N]). This system significantly inhibits the side reactions of HMF with H2 O 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

329

The Role of the Liquid?Solid Interface in the Preparation of Supported Catalysts  

Microsoft Academic Search

The contribution of the Interface Science to the preparation of supported catalysts during the last two decades is presented. It is illustrated how the concepts and the methodologies of the Interface Science could be effectively used for an in?depth understanding of the phenomena involved in the initial preparation step. This, extremely critical step, concerns the deposition of transition metal species

Kyriakos Bourikas; Christos Kordulis; Alexis Lycourghiotis

2006-01-01

330

Evidence for a boroxinate based Brønsted acid derivative of VAPOL as the active catalyst in the catalytic asymmetric aziridination reaction.  

PubMed

Studies are described that were designed to determine the structure of the active catalyst in the asymmetric catalytic aziridination of imines with ethyl diazoacetate (AZ reaction). Evidence suggests that the active catalyst contains a boroxine ring in which one of the three boron atoms is spiro-fused with the two phenol groups of the VAPOL ligand. (11)B and (1)H NMR evidence supports the boroxinate structure B in which the counterion to the boroxinate is the protonated form of the imine. The boroxinate structure is also supported by two solid state structures of a VAPOL boroxinate in which the gegen cation is tetramethyl ammonium and 4-dimethylaminopyridinium. PMID:19813716

Hu, Gang; Huang, Li; Huang, Rui H; Wulff, William D

2009-11-01

331

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

332

Chirality-specific growth of single-walled carbon nanotubes on solid alloy catalysts.  

PubMed

Carbon nanotubes have many material properties that make them attractive for applications. In the context of nanoelectronics, interest has focused on single-walled carbon nanotubes (SWNTs) because slight changes in tube diameter and wrapping angle, defined by the chirality indices (n,?m), will shift their electrical conductivity from one characteristic of a metallic state to one characteristic of a semiconducting state, and will also change the bandgap. However, this structure-function relationship can be fully exploited only with structurally pure SWNTs. Solution-based separation methods yield tubes within a narrow structure range, but the ultimate goal of producing just one type of SWNT by controlling its structure during growth has proved to be a considerable challenge over the last two decades. Such efforts aim to optimize the composition or shape of the catalyst particles that are used in the chemical vapour deposition synthesis process to decompose the carbon feedstock and influence SWNT nucleation and growth. This approach resulted in the highest reported proportion, 55 per cent, of single-chirality SWNTs in an as-grown sample. Here we show that SWNTs of a single chirality, (12,?6), can be produced directly with an abundance higher than 92 per cent when using tungsten-based bimetallic alloy nanocrystals as catalysts. These, unlike other catalysts used so far, have such high melting points that they maintain their crystalline structure during the chemical vapour deposition process. This feature seems crucial because experiment and simulation both suggest that the highly selective growth of (12,?6) SWNTs is the result of a good structural match between the carbon atom arrangement around the nanotube circumference and the arrangement of the catalytically active atoms in one of the planes of the nanocrystal catalyst. We anticipate that using high-melting-point alloy nanocrystals with optimized structures as catalysts paves the way for total chirality control in SWNT growth and will thus promote the development of SWNT applications. PMID:24965654

Yang, Feng; Wang, Xiao; Zhang, Daqi; Yang, Juan; Luo, Da; Xu, Ziwei; Wei, Jiake; Wang, Jian-Qiang; Xu, Zhi; Peng, Fei; Li, Xuemei; Li, Ruoming; Li, Yilun; Li, Meihui; Bai, Xuedong; Ding, Feng; Li, Yan

2014-06-26

333

Direct amidation of carboxylic acids catalyzed by ortho-iodo arylboronic acids: catalyst optimization, scope, and preliminary mechanistic study supporting a peculiar halogen acceleration effect.  

PubMed

The importance of amides as a component of biomolecules and synthetic products motivates the development of catalytic, direct amidation methods employing free carboxylic acids and amines that circumvent the need for stoichiometric activation or coupling reagents. ortho-Iodophenylboronic acid 4a has recently been shown to catalyze direct amidation reactions at room temperature in the presence of 4A molecular sieves as dehydrating agent. Herein, the arene core of ortho-iodoarylboronic acid catalysts has been optimized with regards to the electronic effects of ring substitution. Contrary to the expectation, it was found that electron-donating substituents are preferable, in particular, an alkoxy substituent positioned para to the iodide. The optimal new catalyst, 5-methoxy-2-iodophenylboronic acid (MIBA, 4f), was demonstrated to be kinetically more active than the parent des-methoxy catalyst 4a, providing higher yields of amide products in shorter reaction times under mild conditions at ambient temperature. Catalyst 4f is recyclable and promotes the formation of amides from aliphatic carboxylic acids and amines, and from heteroaromatic carboxylic acids and other functionalized substrates containing moieties like a free phenol, indole and pyridine. Mechanistic studies demonstrated the essential role of molecular sieves in this complex amidation process. The effect of substrate stoichiometry, concentration, and measurement of the catalyst order led to a possible catalytic cycle based on the presumed formation of an acylborate intermediate. The need for an electronically enriched ortho-iodo substituent in catalyst 4f supports a recent theoretical study (Marcelli, T. Angew. Chem. Int. Ed.2010, 49, 6840-6843) with a purported role for the iodide as a hydrogen-bond acceptor in the orthoaminal transition state. PMID:23013456

Gernigon, Nicolas; Al-Zoubi, Raed M; Hall, Dennis G

2012-10-01

334

Bioconversion of MSW (Municipal Solid Waste) and Recovery of Organic Acids.  

National Technical Information Service (NTIS)

Research was conducted to determine the feasibility of bioprocessing municipal solid waste (MSW) to produce organic acids and recover the acids for hydrocarbon fuels production. This work focused on acid production from anaerobic digestion of a simulated ...

A. A. Antonopoulos E. G. Wene

1987-01-01

335

Magnesium oxide-supported ziegler catalyst modified with acid and higher alkanol, and process for preparing narrow MWD HDPE  

Microsoft Academic Search

This patent describes a coordination-catalyst suitable for the polymerization of olefins. It comprises a titanium component and an organoaluminum compound reducing agent on a magnesium oxide support which has been pre-treated with a molar deficiency of a carboxylic acid with respect to the magnesium oxide support. The titanium component is the reaction product of an alkanol having 5 to 12

J. T. T

1989-01-01

336

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

337

SO?H-functionalized acidic ionic liquids as catalysts for the hydrolysis of cellulose.  

PubMed

The conversion of cellulose into valuable chemicals to deal with the depletion of fossil fuel has got much attention. Completing the hydrolysis of cellulose under mild conditions is the key step. In this study, six kinds of SO(3)H-functionalized acidic ionic liquids were used as acid catalyst to promote the hydrolysis of cellulose in 1-butyl-3-methylimidazolium chloride ([BMIM]Cl). All of them were efficient for the hydrolysis of cellulose, with the maximum total reducing sugars (TRS) yields over 83% at 100 °C. Acidic ionic liquids with analogous structures showed similar catalytic activities. Triethyl-(3-sulfo-propyl)-ammonium hydrogen sulfate (IL-5 in this study) was the optimum ionic liquid for cellulose hydrolysis, with the maximum TRS yield at 100 °C up to 99% when the dosage used was 0.2g. In addition, the water in [BMIM]Cl had negative effect on cellulose hydrolysis. Therefore, controlling the content of water in a comparatively low level is quite necessary. PMID:23218286

Liu, Yuanyuan; Xiao, Wenwen; Xia, Shuqian; Ma, Peisheng

2013-01-30

338

Pt\\/TiO 2 (rutile) catalysts for sulfuric acid decomposition in sulfur-based thermochemical water-splitting cycles  

Microsoft Academic Search

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 1wt% Pt\\/TiO2 (rutile) catalysts submitted to flowing concentrated sulfuric acid at 1123K and atmospheric pressure for different times

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

2008-01-01

339

Hydrogenation of unsaturated carboxylic acids on functional gel-type resin supported Pd catalysts: The effect of reactant structure  

Microsoft Academic Search

Functional gel-type resin-based palladium catalysts (0.5–2wt.% Pd) of well dispersed Pd nanoparticles were prepared and characterized by SEM, TEM techniques and swelling measurements. The role of specific properties of gel-type matrix was studied in the hydrogenation of unsaturated CC bonds in series of carboxylic acids, derivatives of acrylic acid. They differ in the type of substituents (methyl, phenyl and carboxyl

A. Knapik; A. Drelinkiewicz; M. Szaleniec; W. Makowski; A. Waksmundzka-Góra; A. Bukowska; W. Bukowski; J. Noworól

2008-01-01

340

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

Microsoft Academic Search

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

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

2003-01-01

341

Asymmetric Mukaiyama aldol reaction of silyl enol ethers with aldehydes using a polymer-supported chiral Lewis acid catalyst  

Microsoft Academic Search

Chiral N-sulfonylated ?-amino acid monomer (5) derived from (S)-tryptophan was copolymerized with styrene and divinylbenzene under radical polymerization conditions to give a polymer-supported N-sulfonyl-(S)-tryptophan (6). Treatment of the polymer-supported chiral ligand with 3,5-bis(trifluoromethyl)phenyl boron dichloride afforded a polymeric Lewis acid catalyst (16) effective for asymmetric Mukaiyama aldol reaction of silyl enol ethers and aldehydes. Various aldehydes were allowed to react

Shinichi Itsuno; Shinnosuke Arima; Naoki Haraguchi

2005-01-01

342

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

343

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

Microsoft Academic Search

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

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

2005-01-01

344

Pt? Sn Al 2 O 3 sol-gel catalysts: catalystic properties  

Microsoft Academic Search

Platinum-tin supported catalysts at various tin and platinum contents were prepared by the sol-gel method by adding tetrabutyltin to a homogeneous solution containing aluminum tri-sec-butoxide (TBA). After gelation, the solids were dried, calcined and then impregnated with an aqueous solution of hexachloroplatinic acid. Catalysts prepared by this method show specific BET areas around 270 m2\\/g and platinum dispersion up to

R. Gómez; V. Bertin; T. López; I. Schifter; G. Ferrat

1996-01-01

345

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

346

Acid-base properties of the active sites of the surface of a skeletal nickel and promoted skeletal nickel catalyst  

NASA Astrophysics Data System (ADS)

The acid-base and adsorption properties of the active sites of the surface of a skeletal nickel and promoted nickel catalyst in aqueous solutions were studied by the potentiometric and pKspectroscopy methods. Titanium added as a promoter resulted in an increased number of lines in the pK spectra, which may attest to higher chemical activity of the promoted catalyst. An increase in the pH value of the media was shown to cause a shift in the process equilibria toward the formation of atomic strongly-bound forms of adsorbed hydrogen.

Filippov, D. V.; Kravchenko, A. V.; Ulitin, M. V.; Ryazanov, M. A.

2010-03-01

347

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

PubMed

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

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

2014-04-18

348

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

349

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

PubMed

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

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

2012-08-01

350

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

351

The acidity influence of solid wastes carbon fluoride production of SICP on products strength  

Microsoft Academic Search

This submission describes methods of solid waste utilization. The acid content in fluorideanhydrite solid waste influences upon products strength, raising it. If fluorideanhydrite acidity is less 6 or 15%, it's possible to raise it by adding of foul acid electrolyte. There was experimentally stated that the electrolyte admixtures do not reduce product strength. And so we can utilize these kinds

T. S. Tsygankova; Y. M. Fedorchuk

2004-01-01

352

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

353

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

354

Enantioselective fluorescent recognition of a soluble "supported" chiral acid: toward a new method for chiral catalyst screening.  

PubMed

The long-chain aliphatic-group-substituted mandelic acid 3c, which is soluble only in THF and insoluble in water and many polar/nonpolar organic solvents, has been synthesized. This unique solubility allows 3c to be easily isolated from reaction mixtures and makes it potentially useful for catalyst screening. The fluorescent sensors (R)- and (S)-1 can be used to determine the ees of various samples of 3c generated from a series of catalyst screening experiments. The fluorescence measurements correlate well with the conventional HPLC-chiral column analysis. This work demonstrates that the enantioselective fluorescent recognition of organic substrates can lead to a fundamentally new method for chiral catalyst screening. [reaction: see text] PMID:16048312

Li, Zi-Bo; Lin, Jing; Qin, Ying-Chuan; Pu, Lin

2005-08-01

355

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

Microsoft Academic Search

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

Jiyun Feng; Xijun Hu; Po Lock Yue

2004-01-01

356

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

PubMed Central

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

2010-01-01

357

Methanesulfonamide: a cosolvent and a general acid catalyst in sharpless asymmetric dihydroxylations.  

PubMed

To obtain information about the effect that methanesulfonamide has in the hydrolysis step in Sharpless asymmetric dihydroxylation, a series of aliphatic and conjugated aromatic olefins were dihydroxylated with and without methanesulfonamide. The hypothesis in this study was that methanesulfonamide is a cosolvent that aids in the transfer of the hydroxide ions from the water phase to the organic phase. A plot of t90% versus the computational partition coefficient clog P of the intermediate osmate ester of nonterminal aliphatic olefins revealed that the polarity of the intermediate osmate ester has a significant effect on the reaction time and methanesulfonamide effect. The more polar the intermediate osmate ester, the faster is the reaction without methanesulfonamide and the smaller the accelerating methanesulfonamide effect. Methanesulfonamide had no accelerating effect in the asymmetric dihydroxylation of short chain terminal aliphatic olefins as a result of easier accessibility of terminal osmate ester groups to the water phase. A cosolvent hypothesis was found not to be valid in asymmetric dihydroxylations of conjugated aromatic olefins. In the reaction conditions used in Sharpless asymmetric dihydroxylation, weakly acidic methanesulfonamide was found to be a general acid catalyst that protonates the intermediate osmate esters of conjugated aromatic olefins in the hydrolysis step. PMID:19301884

Junttila, Mikko H; Hormi, Osmo O E

2009-04-17

358

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

359

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

360

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

361

SO2-4/TiO2-SiO2 Mixed Oxide Catalyst, I: Synthesis, Characterization, and Acidic Properties.  

PubMed

A series of sulfate-doped titania-silica mixed oxides have been prepared by immersing titania-silica gel in the required volume of sulfuric acid, followed by drying. The mixed oxide gel is obtained by hydrolyzing an equimolar mixture of tetraethylorthosilicate (TEOS) and tetrabutylorthotitanate (TBOT) at pH 3. The materials, after calcining at 723 K for 4 h, are characterized by XRD, FT-IR, the BET method, and surface acid strength by the Hammett indicator method. The catalytic activity tests are carried in a fixed bed catalytic reactor (i.d. = 10 mm) for alcohol conversion, whereas cumene cracking/dehydrogenation reactions are carried out in a micropulse reactor. XRD results shows that the titania-silica mixture is amorphous and the crystallization starts with sulfation. The surface of the mixed oxide contains both bridged and normal hydroxyl groups, as observed from FT-IR data. The surface area of the material is not much altered by sulfation and lies within 50 m2/g. The acid strength of 4 wt% SO2-4/TiO2-SiO2 is found to be stronger than that of 100% concentrated H2SO4. In the case of 2-propanol conversion, low acetone selectivity indicates the presence of weak basic sites, whereas methanol conversion over all solids shows that dehydration follows a parallel and consecutive pathway. A good correlation is found between the cumene cracking and the acidity of the catalysts. Copyright 1999 Academic Press. PMID:10395770

Parida; Samantaray; Mishra

1999-08-01

362

Method of preparing a hydroconversion sulfided molybdenum catalyst concentrate  

SciTech Connect

In a method for preparing a catalyst wherein aqueous phosphomolybdic acid is heated in the presence of a hydrocarbonaceous oil and a gas selected from the group consisting of a hydrogen-containing gas, a hydrogen sulfide-containing gas and mixtures thereof to convert the phosphomolybdic acid to a solid catalyst, the improvement is described which comprises: (a) forming a mixture of a hydrocarbonaceous oil comprising constituents boiling above about 1050/sup 0/F and the aqueous solution of phosphomolybdic acid in an amount to provide from about 0.2 to 2 weight percent molybdenum, calculated as elemental molybdenum, based on the hydrocarbonaceous oil to produce a water-containing catalyst precursor concentrate; (b) drying the water-containing catalyst precursor concentrate to remove the water and produce a substantially water-free catalyst precursor concentrate; (c) contacting the water-free catalyst precursor concentrate with added hydrogen sulfide at a temperature from about 50/sup 0/ to about 600/sup 0/F and a hydrogen sulfide partial pressure ranging from about 14.7 psia to about 100 psia to produce a sulfided catalyst precursor concentrate; (d) separating the unreacted hydrogen sulfide from the sulfided catalyst precursor concentrate; (e) heating the sulfided catalyst precursor concentrate in the absence of hydrogen sulfide and in the absence of hydrogen, at a temperature of at least about 650/sup 0/F and a total pressure ranging from about 0 to about 100 psig, for a time sufficient to convert the sulfided catalyst precursor to a solid molybdenum-containing catalyst and, thereby, produce a catalyst concentrate.

Bearden, R. Jr.; Aldridge, C.L.; Mayer, F.X.; Taylor, J.H.; Lewis, W.E.

1988-04-26

363

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

364

Double bond isomerization of olefin-containing feeds with minimal oligomerization using surface acidity deactivated zeolite catalysts  

SciTech Connect

A method is described for double bond isomerization of alpha-olefin-containing organic feedstock with minimal oligomerization which comprises contacting said feedstock under double bond isomerization conditions with a double bond isomerization catalyst comprising a zeolite having a Constraint Index of 1 to 12 whose surface has been at least partially deactivated for acid catalyzed reactions by chemisorption of an alkyl-substituted pyridine surface-deactivating agent which possesses an average cross section diameter greater than that of the zeolite pores.

Haag, W.O.; Heck, R.H.; Santiesteban, J.G.; Shihabi, D.S.

1993-08-17

365

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...

366

Preparation of Keggin and Preyssler Heteropolyacid Catalysts on Amine-modified SBA15 and Their Catalytic Performances in Esterification of n Butanol with Acetic Acid  

Microsoft Academic Search

The Keggin and Preyssler-structured tungstophosphoric acid catalysts anchored on the surface of modified SBA-15 (KNS and PNS)\\u000a by grafting amine groups into system, and were characterized by infra-red spectroscopy, X-ray diffraction, N2-adsorption, Hammett indicator and UV-Vis spectroscopy. Their catalytic behaviors were investigated in the esterification\\u000a of n-butanol with acetic acid. Characterization results for obtained catalysts verified the ordered hexagonal mesostructure

Shanshan Wu; Jun Wang; Weihong Zhang; Xiaoqian Ren

2008-01-01

367

Alkylation of aromatic compounds with multi-component Lewis acid catalysts of ZnCl 2 and ionic liquids with different organic cations  

Microsoft Academic Search

Alkylation of aromatic compounds with various alkylating agents such as benzyl chloride, benzyl alcohol and isopropyl chloride\\u000a were investigated using ZnCl2 based ionic liquid (ILs) Lewis acid catalysts. Multi-component Lewis acid catalysts of ZnCl2 and ionic liquids such as 1-butyl-3-methylimidazolium bromide, 1-butylpyridinium bromide, cholin chloride and tetrabutylammonium\\u000a bromide were prepared, supported on silica gel, and compared for alkylation reactions with

Rajendra Srivastava; Shin-Ichiro Fujita; Shuhei Okamura; Masahiko Arai

2009-01-01

368

Green, One-Pot, Solvent-Free Synthesis of 1,2,4,5Tetrasubstituted Imidazoles Using a Brønsted Acidic Ionic Liquid as Novel and Reusable Catalyst  

Microsoft Academic Search

3-Methyl-1-(4-sulfonic acid)butylimidazolium hydrogen sulfate [(CH2)4SO3HMIM][HSO4], a Brønsted acidic ionic liquid, has been used as an efficient, green, and reusable catalyst for the synthesis of 1,2,4,5-tetrasubstituted imidazoles using benzil, an aromatic aldehyde, and a primary amine in the presence of ammonium acetate under solvent-free conditions. The catalyst could be recycled and reused several times without noticeably decreasing the catalytic activity.

Abolghasem Davoodnia; Majid M. Heravi; Zahra Safavi-Rad; Niloofar Tavakoli-Hoseini

2010-01-01

369

On the acid-dealumination of USY zeolite: a solid state NMR investigation  

Microsoft Academic Search

The dealumination of USY (ultrastable Y) zeolites by nitric acid and oxalic acid treatment was systematically investigated by multinuclear solid-state NMR and MQ MAS NMR experiments. The results show that both acids are very effective in removing non-framework Al as well as framework Al but that aluminum is extracted from the lattice at a higher rate by oxalic acid even

Zhimin Yan; Ding Ma; Jianqin Zhuang; Xianchun Liu; Xiumei Liu; Xiuwen Hana; Xinhe Bao; Fuxiang Chang; Lei Xu; Zhongmin Liu

2003-01-01

370

In situ fourier transform infrared study of crotyl alcohol, maleic acid, crotonic acid, and maleic anhydride oxidation on a V-P-O industrial catalyst  

SciTech Connect

Crotyl alcohol, maleic acid, crotonic (2-butenoic) acid, and maleic anhydride were fed to an in situ infrared cell at 300/sup 0/C containing a P/V = 1.1 vanadium-phosphorous-oxide (V-P-O) catalyst used for the selective oxidation of n-butane. Crotyl alcohol was used as a mechanistic probe for the formation of reactive olefin species observed during previous n-butane and 1-butene studies. Crotonic acid, maleic acid, and maleic anhydride were fed as probes for the existence of other possible adsorbed intermediates. Olefin species and maleic acid are proposed as possible reaction intermediates in n-butane selective oxidation to maleic anhydride. The involvement of peroxide species in the oxidation of butadiene to maleic acid is also discussed.

Wenig, R.W.; Schrader, G.L.

1987-10-22

371

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

372

Thermochemical comparison of Argonne premium coal samples with model solid acids  

SciTech Connect

This presentation is a summary of results acquired over the last five years using the heats of interaction of a series of bases with various solid acids as a means for classifying them. A sulfonic acid resin provides a solid model for Broensted acidity. Silica is a model solid for hydrogen bonding interactions and several grades of graphitized carbon black are an excellent model for van der Waals/dispersion force interactions. Heats of interaction of the series of bases with several types of Argonne premium coals compared with those for the model solids and serve as a means for coal classification.

Arnett, E.M.; Hutchinson, B.J.; Gumkowski, M.; Liu, Q.

1988-01-01

373

Direct foamed and nano-catalyst impregnated solid-oxide fuel cell (SOFC) cathodes  

SciTech Connect

A binder system containing polyurethane precursors was used to in situ foam (direct foam) a (La{sub 0.6}Sr{sub 0.4}){sub 0.98} (Co{sub 0.2} Fe{sub 0.8})O{sub 3-{delta}} (LSCF) cathode composition upon a yttrium-stabilized zirconia (YSZ) electrolyte coated with a porous #3;10 mm thick cathode active layer. The YSZ electrolyte was #3;110 mm in thickness, and a full cell was created by application of a Ni/(Ce{sub 0.9}Gd{sub 0.1})O{sub 2} cermet as the baseline anode. Cells possessing the foamed LSCF cathode were compared to cells constructed via standard methods in terms of resultant microstructure, electrochemical performance, and introceptive character. The foamed cathode tended to possess a high level of tortuous porosity which was ellipsoidal and interconnected in character. Both the standard and foamed cathode structures were subjected to an infiltration process, and the resultant microstructure was examined. The impregnation efficiency of the foamed cathode was at least #3;10% greater per deposition than that of an unfoamed porous LSCF cathode. The SOFC with the Pt nano-catalyst impregnated foamed cathode demonstrated a maximum power density of 593 mW/cm{sup 2} utilizing wet H{sub 2} fuel, which is 52% higher than a SOFC with the baseline Pt-impregnated LSCF cathode (#3;390 mW/cm{sup 2}) at 800 {degrees}C. The cathode compositional and microstructural alterations obtainable by foaming led to the elevated power performance, which was shown to be quite high relative to standard SOFCs with a thick YSZ electrolyte.

Gandavarapu, Sodith R.; Sabolsky, Katarzyna; Gerdes, Kirk; Sabolsky, Edward M.

2013-03-01

374

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

375

Sulfated tin oxide as solid superacid catalyst for transesterification of waste cooking oil: An optimization study  

Microsoft Academic Search

Biodiesel is a renewable, biodegradable and non-toxic fuel which can be easily produced through transesterification reaction. However, current commercial usage of refined vegetable oils for biodiesel production is impractical and uneconomical due to high feedstock cost and priority as food resources. Low-grade oil, typically waste cooking oil can be a better alternative; however, the high free fatty acids (FFA) content

Man Kee Lam; Keat Teong Lee; Abdul Rahman Mohamed

2009-01-01

376

Comparative characterization of basicity and acidity of metal oxide catalysts for the oxidative coupling of methane by different methods  

Microsoft Academic Search

A comprehensive study of the surface basicity and acidity of alkaline earth metal oxides, La2O3\\/CaO, CeO2\\/CaO and ZnO-doped NaOH (11 mol-%)\\/CaO which had earlier been tested as catalysts for the oxidative coupling of methane was performed. For determining the acid-base properties two probe reactions, i.e., the decomposition of 2-propanol to acetone and propene and the retroaldolisation of diacetone alcohol, further

Petra Käßner; Manfred Baerns

1996-01-01

377

Solar photocatalytic treatment of landfill leachate using a solid mineral by-product as a catalyst.  

PubMed

The treatment of municipal solid waste landfill leachate in a pilot plant made up of solar compound parabolic collectors, using a solid industrial titanium by-product (WTiO(2)) containing TiO(2) and Fe(III) as a photocatalyst, was investigated. In the study evidence was found showing that the degradation performed with WTiO(2) was mainly due to the Fe provided by this by-product, instead of TiO(2). However, although TiO(2) had very little effect by itself, a synergistic effect was observed between Fe and TiO(2). The application of WTiO(2), which produced coupled photo-Fenton and heterogeneous catalysis reactions, achieved a surprisingly high depuration level (86% of COD removal), higher than that reached by photo-Fenton using commercial FeSO(4) (43%) in the same conditions. After the oxidation process the biodegradability and toxicity of the landfill leachate were studied. The results showed that the leachate biodegradability was substantially increased, at least in the first stages of the process, and again that WTiO(2) was more efficient than FeSO(4) in terms of increasing biodegradability. PMID:22633861

Poblete, Rodrigo; Prieto-Rodríguez, Lucia; Oller, Isabel; Maldonado, Manuel I; Malato, Sixto; Otal, Emilia; Vilches, Luis F; Fernández-Pereira, Constantino

2012-08-01

378

Electrochemical Characterization of Solid Acid Fuel Cell Electrodes  

NASA Astrophysics Data System (ADS)

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

Sasaki, Kenji Alexander

379

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

380

Esterification of oleic acid in a three-phase, fixed-bed reactor packed with a cation exchange resin catalyst.  

PubMed

Esterification of oleic acid was performed in a three-phase fixed-bed reactor with a cation exchange resin catalyst (Amberlyst-15) at high temperature, which was varied from 80 to 120 °C. The fatty acid methyl ester (FAME) yields in the fixed-bed reactor were increased with increases in the reaction temperature, methanol flow rate and bed height. Moreover, the FAME yields were higher than those obtained using a batch reactor due to an equilibrium shift toward the product that resulted from continuous evaporation of the produced water. In addition, there was no catalyst deactivation during the esterification of oleic acid. However, addition of sunflower oil to the oleic acid reduced the FAME yield obtained from simultaneous esterification and transesterification. The FAME yield was 97.5% at a reaction temperature of 100 °C in the fixed-bed with a height of 5 cm when the methanol and oleic acid feed rates were 8.6 and 9.0 mL/h, respectively. PMID:20855192

Son, Sung Mo; Kimura, Hiroko; Kusakabe, Katsuki

2011-01-01

381

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.

382

Acid strength of proton donors in complexes of nontransition metal halides as a measure of the activity of electrophilic polymerisation catalysts  

NASA Astrophysics Data System (ADS)

Data on one of the most urgent problems in modern theoretical chemistry are reviewed: the calculation of the acid strength of the complexes formed by the interaction of Lewis acids with proton donors, and the correlation of the acid strength with the activity and selectivity of these complexes as catalysts of electrophilic processes. Complexes based on aluminium and magnesium chlorides and on boron fluorides are discussed. It is shown that increasing the acid strength of these complexes as catalysts of electrophilic polymerisation reactions increases their activity but lowers their selectivity. The bibliography includes 43 references.

Minsker, Karl S.; Babkin, Vasilii A.; Zaikov, Gennadii E.

1994-03-01

383

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

PubMed

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

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

2012-12-01

384

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

385

Process for catalyst recovery  

SciTech Connect

This patent describes a process for recovering a homogeneous catalyst from a catalytic reaction mixture. It comprises: removing the reaction mixture solvent using temperatures such that decomposition of the catalyst is minimized; simultaneously adding a lower alkanoic acid; and recovering the precipitated homogeneous catalyst.

Bodurow, C.C.

1990-08-21

386

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.

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

387

B-doped Pd catalyst: boosting room-temperature hydrogen production from formic acid-formate solutions.  

PubMed

Facile production of hydrogen at room temperature is an important process in many areas including alternative energy. In this Communication, a potent boron-doped Pd nanocatalyst (Pd-B/C) is reported for the first time to boost hydrogen generation at room temperature from aqueous formic acid-formate solutions at a record high rate. Real-time ATR-IR spectroscopy is applied to shed light on the enhanced catalytic activity of B-doping and reveals that the superior activity of Pd-B/C correlates well with an apparently impeded COad accumulation on its surfaces. This work demonstrates that developing new anti-CO poisoning catalysts coupled with sensitive interfacial analysis is an effective way toward rational design of cost-effective catalysts for better hydrogen energy exploitation. PMID:24635163

Jiang, Kun; Xu, Ke; Zou, Shouzhong; Cai, Wen-Bin

2014-04-01

388

Base adsorption calorimetry for characterising surface acidity: a comparison between pulse flow and conventional “static” techniques  

Microsoft Academic Search

A pulsed flow adsorption microcalorimeter (pulse-FMC) has been developed by modifying a Setaram 111. It is tested in comparison with a conventional pulsed static adsorption microcalorimeter (pulse-SMC) for characterising surface acidity of solid acid catalysts. Small pulses of 1% ammonia in helium are delivered to an activated catalyst sample and its surface acidity is differentially profiled in terms of the

S. P. Felix; C. Savill-Jowitt; D. R. Brown

2005-01-01

389

Extraction of zirconium and hafnium from nitric acid solutions by solid extractant based on tributyl phosphate  

SciTech Connect

A study has been made of extraction equilibrium and kinetics and the influence of temperature and aqueous phase acidity on the extraction of zirconium and hafnium from nitric acid solutions by a solid extractant based on tributyl phosphate. Results are presented from pilot-plant experiments on Zr and Hf extraction from acidic pulps with high silicon contents, using pulsed columns.

Korovin, V.Yu.; Yagodin, G.A.; Savel`eva, V.I. [Dnieper Scientific Center, Dneprodzerzhinsk (Ukraine)

1994-10-20

390

Synthesis, characterization and application of a nano-manganese-catalyst as an efficient solid catalyst for solvent free selective oxidation of ethylbenzene, cyclohexene, and benzylalcohol  

NASA Astrophysics Data System (ADS)

The object of this study is to synthesize the heterogeneous Mn-nano-catalyst (MNC) which has been covalently anchored on a modified nanoscaleSiO2/Al2O3, and characterized by FT-IR, UV-Vis, CHN elemental analysis, EDS, TEM, and EDX. The method is efficient for the highly selective oxidation of ethylbenzene, cyclohexene, and benzylalcohol without the need to any solvents, using tert-butyl hydroperoxide (TBHP) as an oxidant. Oxidation of ethylbenzene, cyclohexene, and benzylalcohol gave acetophenone, 2-cyclohexene-1-one and benzaldehyde, respectively, as major products. Reaction conditions have been optimized by considering the effect of various factors such as reaction time, amounts of substrates and oxidant, Mn-nano-catalyst and application of various solvents.

Habibi, Davood; Faraji, Ali Reza

2013-07-01

391

Photoassisted reaction of H/sub 2/ with CO/sub 2/ over solid catalysts. Technical report  

SciTech Connect

The dark and photoassisted reactions of CO/sub 2/ with H/sub 2/ over alpha-Fe/sub 2/O3, Zn-Fe-oxide, Co-Mo-Al-oxide, Co-Mo-Al-oxide, Co-Mo-Ti-oxide, platinized La-Ni-oxide and platinized SrTiO/sub 3/ were investigated in the absence and presence of water vapor. Illumination was by a Hg-Xe-lamp at wavelengths above 350nm. The incident light flux, measured by ferrioxalate actinometry, was (1.02 + or - 0.08) x 10/sup 17/ power photons/sec. Reactants in the ratio of H/sub 2/:CO/sub 2/ = 2:1 were passed once over dry films of powdered catalysts at 30 C and latm with contact times of 1/2 or 1 min. Products were analyzed by gas chromatography. No reaction took place in the absence of catalyst. Catalyzed rates of production of products were constant over the 22-hr periods investigated. CO was the only product obtained in significant amounts in the dark. Under illumination, rates of formation of CO increased by a factor of 2 - 4.5. CH/sub 4/ was the only other product of the photoassisted reaction in the absence of water vapor, with yields less than 0.2 mole% of those of CO. In the presence of water vapor (3 mole% of supplied CO/sub 2/), formic acid was produced at rates up to 19 mole% the rate of formation of CO, along with minor amounts of CH/sub 4/, CH/sub 2/O and CH/sub 3/OH, all produced at rates less than 0.2 mole% that of CO. The highest photoassisted yields were obtained over Co-Mo-Al oxide, with efficiency of conversion of incident photons into products around 0.35 molecule of product/incident photon. The corresponding estimated quantum yield was 1 molecule of product/absorbed photon.

Lichtin, N.N.; Vijayakumar, K.M.; Rubio, B.I.

1986-11-14

392

Study of preparation and properties on solid superacid sulfated titania–silica nanomaterials  

Microsoft Academic Search

Solid superacid sulfated titania–silicon (SO42?\\/TiO2–SiO2) nanocatalysts were prepared by the chemical method. The structure and the properties of the catalysts were examined by using XRD, BET, DTA and IR spectroscopy. Acidity properties of the catalysts were tested by Hammett indicator. Catalytic activity of the catalysts was evaluated by the reaction of glycerin with acetic acid in toluene. The optimum calcination

Hua Yang; Rong Lu; Li Wang

2003-01-01

393

Efficient and selective conversion of methyl lactate to acrylic acid using Ca 3(PO 4) 2–Ca 2(P 2O 7) composite catalysts  

Microsoft Academic Search

Calcium phosphate Ca3(PO4)2 and calcium pyrophosphate Ca2(P2O7) composite catalysts of different weight ratios were prepared by a slurry-mixing method. These composite catalysts were calcined at 500°C in air and characterized by N2 sorption for specific surface area by XRD for crystal phases and by TPD-NH3 (acidity), TPD-CO2 (basicity) and SEM for morphological features. All the Ca3(PO4)2–Ca2(P2O7) composite catalysts were found

Ju Hyeong Hong; Jong-Min Lee; Hyungrok Kim; Young Kyu Hwang; Jong-San Chang; Shiva B. Halligudi; Yo-Han Han

2011-01-01

394

Nanoporous PdNi Alloy Nanowires As Highly Active Catalysts for the Electro-Oxidation of Formic Acid.  

PubMed

Highly active and durable catalysts for formic acid oxidation are crucial to the development of direct formic acid fuel cell. In this letter, we report the synthesis, characterization, and electrochemical testing of nanoporous Pd(57)Ni(43) alloy nanowires for use as the electrocatalyst towards formic acid oxidation (FAO). These nanowires are prepared by chemically dealloying of Ni from Ni-rich PdNi alloy nanowires, and have high surface area. X-ray diffraction data show that the Pd(57)Ni(43) nanowires have the face-centered cubic crystalline structure of pure Pd, whereas X-ray photoelectron spectroscopy confirm the modification of electronic structure of Pd by electron transfer from Ni to Pd. Electrocatalytic activity of the nanowires towards FAO exceeds that of the state-of-the-art Pd/C. More importantly, the nanowires are highly resistant to deactivation. It is proposed that the high active surface area and modulated surface properties by Ni are responsible for the improvement of activity and durability. Dealloyed nanoporous Pd(57)Ni(43) alloy nanowires are thus proposed as a promising catalyst towards FAO. PMID:21192691

Du, Chunyu; Chen, Meng; Wang, Wengang; Yin, Geping

2011-02-01

395

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

396

Effects of acid catalyst type on structural, morphological, and optoelectrical properties of spin-coated TiO2 thin film  

NASA Astrophysics Data System (ADS)

The effects of different acid catalysts of nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, boric acid, acetic acid, and citric acid on structural, morphological, and optoelectrical properties of nanocrystalline spin-coated TiO2 thin films synthesized via alkoxide sol-gel route were investigated. It was found that only the sols with HNO3 and HCl are suitable for film preparation. The X-ray diffractometry and Raman analysis showed that crystalline phases could be controlled by the type of acid catalyst. Although the H2SO4 sol shows good stability, it causes extremely different morphology to form due to its different sol nature and high contact angle. Fourier transformed infrared spectra confirmed the presence of acid anion species in all samples even after calcination. Furthermore, it was inferred from UV-visable absorption spectra that although the band gap and thickness of the films are independent of acid catalyst type, the refractive index and porosity of the films are strongly affected by the type of acids.

Golobostanfard, Mohammad Reza; Abdizadeh, Hossein

2013-03-01

397

Effect of the catalyst composition in the Pt x (Ru–Ir) 1? x \\/C system on the electro-oxidation of methanol in acid media  

Microsoft Academic Search

The effect of variations in the composition for ternary catalysts of the type Ptx(Ru–Ir)1?x\\/C on the methanol oxidation reaction in acid media for x values of 0.25, 0.50 and 0.75 is reported. The catalysts were prepared by the sol–gel method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic absorption spectroscopy (AAS) and energy dispersive X-ray (EDX) analyses.

K. I. B. Eguiluz; G. R. Salazar-Banda; D. Miwa; S. A. S. Machado; L. A. Avaca

2008-01-01

398

Perfluorosulfonic acid-functionalized Pt\\/carbon nanotube catalysts with enhanced stability and performance for use in proton exchange membrane fuel cells  

Microsoft Academic Search

To further improve lifetime and performance of carbon nanotube (CNT) supported Pt catalysts for proton exchange membrane fuel cells, perfluorosulfonic acid (PFSA) was introduced by a simple colloid route to functionalize Pt (PFSA-Pt\\/CNT) catalysts. Here the PFSA is available as a binder to tightly anchor Pt nano-particles onto the CNT surfaces, and as a proton conductor to increase the triple

Daping He; Shichun Mu; Mu Pan

2011-01-01

399

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

400

SO{sub 4}{sup 2{minus}}/TiO{sub 2}-SiO{sub 2} mixed oxide catalyst. 1: Synthesis, characterization, and acidic properties  

SciTech Connect

A series of sulfate-doped titania-silica mixed oxides have been prepared by immersing titania-silica gel in the required volume of sulfuric acid, followed by drying. The mixed oxide gel is obtained by hydrolyzing an equimolar mixture of tetraethylorthosilicate (TEOS) and tetrabutylorthotitanate (TBOT) at pH 3. The materials, after calcining at 723 K for 4 h, are characterized by XRD, FT-IR, the BET method, and surface acid strength by the Hammett indicator method. The catalytic activity tests are carried in a fixed bed catalytic reactor (i.e. = 10 mm) for alcohol conversion, whereas cumene cracking/dehydrogenation reactions are carried out in a micropulse reactor. XRD results shows that the titania-silica mixture is amorphous and the crystallization starts with sulfation. The surface of the mixed oxide contains both bridged and normal hydroxyl groups, as observed from FT-IR data. The surface area of the material is not much altered by sulfation and lies within 50 m{sup 2}/g. The acid strength of 4 wt% SO{sub 4}{sup 2{minus}}/TiO{sub 2}-SiO{sub 2} is found to be stronger than that of 100% concentrated H{sub 2}SO{sub 4}. In the case of 2-propanol conversion, low acetone selectivity indicates the presence of weak basic sites, whereas methanol conversion over all solids shows that dehydration follows a parallel and consecutive pathway. A good correlation is found between the cumene cracking and the acidity of the catalysts.

Parida, K.M.; Samantaray, S.K.; Mishra, H.K. [CSIR, Orissa (India). Regional Research Lab.] [CSIR, Orissa (India). Regional Research Lab.

1999-08-01

401

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

402

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.

2014-01-01

403

A study of tin dioxide and antimony tetroxide supported vanadium oxide catalysts by solid-state 51V and 1H NMR techniques.  

PubMed

A series of vanadia catalysts with various V2O5 loadings supported on SnO2 and alpha-Sb2O4 are investigated by the application of X-ray diffraction and solid-state 51V and 1H NMR techniques. XRD results show no evidence for the formation of a crystalline vanadia phase on both supports. However, the 51V NMR spectra of the catalysts reveal the existence of two types of vanadia species on the surface of the support: one due to a dispersed vanadia phase at lower vanadia loadings and the other due to a crystalline vanadia phase at higher vanadium content. The quantity of the dispersed vanadia phase, however, depends on the nature of the support material. The 1H NMR results provide evidence for the existence or non-existence of a metal oxide support interaction through the support surface hydroxyl groups. PMID:1365738

Reddy, B M; Mastikhin, V M

1992-12-01

404

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.

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

2009-01-01

405

Citric and gluconic acid production from fig by Aspergillus niger using solid-state fermentation  

Microsoft Academic Search

  The production of citric and gluconic acids from fig by Aspergillus niger ATCC 10577 in solid-state fermentation was investigated. The maximal citric and gluconic acids concentration (64 and 490\\u000a g\\/kg dry figs, respectively), citric acid yield (8%), and gluconic acid yield (63%) were obtained at a moisture level of 75%,\\u000a initial pH 7.0, temperature 30°C, and fermentation time in 15

T Roukas

2000-01-01

406

Regioselective ?-Alkylation of Silyl Enolates using a Mild Catalyst ZnCl2 Doped on Acidic Alumina  

Microsoft Academic Search

ZnCl2 doped acidic alumina used as a solid support acts as a better Lewis acid in the SNl reaction of trimethyl silyl enol ethers with 3, allylic and benzylic halides to yield exclusively the substituted product in excellent yields. This method has been employed for the synthesis of monocyclic sesquitepene hydrocarbon, (±)-?-bisabolene and a monoterpene, 2,6-dimethyl-7-octen-4-one.

G. L. Kad; Vasundhara Singh; Anupam Khurana; Sangeeta Chaudhary; Jasvinder Singh

1999-01-01

407

Hydrogen sensor based on antimonium pentoxide-phosphoric acid solid electrolyte  

Microsoft Academic Search

A solid composite electrolyte with high proton conductivity based on antimonium pentoxide with additives of phosphoric acid has been obtained. A potentiometric solid-state gas sensor using this electrolyte has been developed for detecting small amounts of hydrogen (10–2000 ppm) in gas mixtures at ambient temperature. The sensor consists of the reference electrode: Ag or Ag\\/(Ag + Ag2SO4), the solid composite

V. G. Ponomareva; G. V. Lavrova; E. F. Hairetdinov

1997-01-01

408

Characterizing the weak organic acids used in low solids fluxes  

Microsoft Academic Search

The elimination of chlorofluorocarbons (CFCs) and other chlorinated cleaning solvents due to their long-term environmental\\u000a impact has lead electronic assemblers to examine soldering fluxes that reduce or eliminate the need for post-solder cleaning.\\u000a Today, low solids fluxes are replacing more traditional rosin-based and water-soluble fluxes because many of them can be used\\u000a in a no-clean process. Most low solids fluxes

Brian A. Smith; Laura J. Turbini

1999-01-01

409

Modification of acid supports by solid-state redox reaction  

Microsoft Academic Search

The solid-state redox reaction of a number of metals in contact with ZSM-5 and Y zeolites, ?-alumina, and silica was investigated by temperature-programmed hydrogen evolution (TPHE), diffuse reflectance Fourier transform IR spectroscopy (DRIFT), X-ray absorption near-edge structure spectroscopy (XANES), and X-ray powder diffraction (XRD). Among all studied metals, gallium, zinc, manganese, and iron were found to undergo a solid-state redox

A. Hagen; E. Schneider; A. Kleinert; F. Roessner

2004-01-01

410

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

411

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

412

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

PubMed

To synthesize monodisperse palladium nanoparticles dispersed on reduced graphene oxide (RGO) sheets, we have developed an easy and scalable solvothermal reduction method from an organic solution system. The RGO-supported palladium nanoparticles with a diameter of 3.8?nm are synthesized in N-methyl-2-pyrrolidone (NMP) and in the presence of oleylamine and trioctylphosphine, which facilitates simultaneous reduction of graphene oxide and formation of Pd nanocrystals. So-produced Pd/RGO was tested for potential use as electrocatalyst for the electro-oxidation of formic acid. Pd/RGO catalyzes formic acid oxidation very well compared to Pd/Vulcan XC-72 catalyst. This synthesis method is a new way to prepare excellent electrocatalysts, which is of great significance in energy-related catalysis. PMID:24675779

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

2014-01-01

413

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

414

H-Gallosilicate (MFI) Propane Aromatization Catalyst: Influence of Si\\/Ga Ratio on Acidity, Activity and Deactivation Due to Coking  

Microsoft Academic Search

Influence of bulk Si\\/Ga ratio of H-gallosilicate (MFI) on its degalliation (during calcination for removal of template and deammoniation of NH4form), acidity\\/acid strength distribution (measured by stepwise thermal desorption and chemisorption of pyridine at 50–400°C using GC techniques and also by acid catalyzed model reactions viz. iso-octane cracking and toluene disproportionation) and initial activity\\/product selectivity and catalyst deactivation in propane

V. R. Choudhary; A. K. Kinage; C. Sivadinarayana; P. Devadas; S. D. Sansare; M. Guisnet

1996-01-01

415

Olefin polymerization catalyst compositions and polymerization process  

SciTech Connect

This patent describes a process for the catalytic polymerization of an olefin by contact with a catalyst composition comprising an organoaluminum compound, a selectivity control agent and a solid titanium-containing catalyst component in which the atomic ratio of aluminum to titanium is from 1:1 to 150:1. The solid component is obtained by: (a) halogenating a magnesium compound of the formula MgR'R'' where R' is an alkoxide or aryloxide group and R'' is an alkoxide or aryloxide group or halogen, with a tetravalent titanium halide in the presence of a halohydrocarbon and an electron donor, therein forming a halogenated product; (b) contacting the halogenated product with an acid halide; (c) contacting the resulting acid halide-treated product with a tetravalent titanium halide at a temperature of about 40/sup 0/ to about 140/sup 0/C; and (d) washing the resulting titanium halide-treated product with an inert hydrocarbon liquid.

Job, R.C.

1987-04-14

416

Reaction of carboxylic acids with vinyl ethers under solvent-free conditions using molecular iodine as a catalyst.  

PubMed

The reaction of vinyl ethers with carboxylic acids using iodine as a catalyst under solvent-free conditions was investigated. The reaction of saturated carboxylic acids with vinyl ethers gave the corresponding esters. Mechanistic studies revealed the production of the adduct of the vinyl ether with the carboxylic acid, which then rearranged to form the ester. At low temperatures, the reaction of 2-(1-hydroxycyclohexyl)acetic acid (1) and butyl vinyl ether yielded a butyl ester. However, at a reaction temperature of 80°C, both the esterification and the elimination of a water molecule occurred, yielding the unsaturated butyl ester butyl 2-cyclohexenylacetate. The reaction of 2-((1S,2S,4R)-2-hydroxy-1,7,7-trimethylbicyclo[2.2.1]heptan-2-yl)acetic acid (12) with butyl vinyl ether at low temperatures resulted in a mixture of four compounds. However, similar to the high-temperature (>60°C) reaction of 1, the esterification was accompanied by the elimination of a water molecule to give the unsaturated butyl ester (E)-butyl 2-((1S,4R)-1,7,7-trimethylbicyclo[2.2.1]heptan-2-ylidene)acetate. While a ?-hydrogen was abstracted to form the endo-type double bond in the reaction of 1, an ?-hydrogen was abstracted to form the exo-type double bond in the reaction of 12. PMID:23357815

Hanzawa, Yohko; Kasashima, Yoshio; Hashimoto, Kahoko; Sasaki, Tatsuhiro; Tomisaki, Keita; Mino, Takashi; Sakamoto, Masami; Fujita, Tsutomu

2013-01-01

417

Recovery of nickel from spent NiO/Al2O3 catalyst through sulfuric acid leaching, precipitation and solvent extraction.  

PubMed

Effective recovery of nickel (Ni) from spent NiO/Al(2)O(3) catalyst in a simple hydrometallurgical route is suggested. Nickel recovery of 99.5% was achieved with sulfuric acid leaching. The leach liquor was partly neutralized and nickel ammonium sulfate was precipitated by adding ammonia. The nickel in the supernatant was concentrated by solvent extraction using D2EHPA and subsequently stripped back into sulfuric acid and returned to the precipitation stage. Necessary counter current extraction and stripping stages were determined in McCabe-Thiele diagrams. The suggested method appears simple and very effective in recovering nickel from spent catalysts from the petrochemical industry. PMID:21930525

Nazemi, M K; Rashchi, F

2012-05-01

418

Solid state fermentation for L-glutamic acid production using Brevibacterium sp  

Microsoft Academic Search

Solid state fermentation system was used to cultivate Brevibacterium sp. on sugar cane bagasse impregnated with a medium containing glucose, urea, mineral salts and vitamins for producing L-glutamic acid. Maximum yields (80 mg glutamic acid per g dry bagasse with biomass and substrate - mg\\/gds) were obtained when bagasse of mixed particle size was moistened at 85–90 % mositure level

K. Madhavan Nampoothiri; Ashok Pandey

1996-01-01

419

Solid-state fermentation for the synthesis of citric acid by Aspergillus niger  

Microsoft Academic Search

Solid-state fermentation was carried out to evaluate three different agro-industrial wastes, sugar cane bagasse, coffee husk and cassava bagasse for their efficiency in production of citric acid by a culture of Aspergillus niger. Cassava bagasse best supported the mould's growth, giving the highest yield of citric acid among the tested substrates. Results showed the fungal strain had good adaptation to

Luciana P. S Vandenberghe; Carlos R Soccol; Ashok Pandey; J.-M Lebeault

2000-01-01

420

Analysis of solids resulted from dilute-acid pretreatment of lignocellulosic biomass  

Microsoft Academic Search

Lignocellulosic biomass materials were pretreated with dilute sulfuric acid, followed by analysis of partially and extensively washed pretreated solids. It is demonstrated that it is of crucial importance to perform extensive washing for accurate carbohydrate analyses to be obtained. Klason lignin, acid-soluble lignin, and ash analyses were not significantly affected by the extent of washing.

T. Hsu; Q. Nguyen

1995-01-01

421

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

Microsoft Academic Search

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

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

2003-01-01

422

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.

423

Synthesis, Structure, and Properties of a Mixed-Valent Triiron Complex of Tetramethyl Reductic Acid, an Ascorbic Acid Analog, and its Relationship to a Functional Non-Heme Iron Oxidation Catalyst System  

PubMed Central

The purple triiron(II,III,III) complex, [Fe3Cl2(TMRASQ)4(HTMRA)2]·C5H12 (1·C5H12), where H2(TMRA) is tetramethyl reductic acid, 4,4,5,5-tetramethyl-2,3-dihydroxy-2-cyclopenten-1-one, and H(TMRASQ) is the semiquinone form of this ligand, was prepared from (Et4N)2[Fe2OCl6] and H2(TMRA) and characterized by X-ray crystallography, Mössbauer spectroscopy, and redox titrations. The physical properties of the complex in solution are consistent with its mixed-valent character, as delineated by a solid-state structure analysis. Assignments of the iron and ligand oxidation states in the crystal were made on the basis of a valence bond sum analysis and the internal ligand geometry. As the first well-characterized iron complex of an ascorbic acid H2(AA) analog, 1 provides insight into the possible coordination geometry of the family of complexes containing H2AA and its analogues. In the presence of air and H2TMRA, 1 is able to catalyze the oxidation of cyclohexane to cyclohexanol with remarkable selectivity, but the nature of the true catalyst remains unknown.

Kim, YooJin; Feng, Xudong; Lippard, Stephen J.

2011-01-01

424

Active sites in vanadia\\/titania catalysts for selective aerial oxidation of ?-picoline to nicotinic acid  

Microsoft Academic Search

Vanadia\\/titania catalysts with varying vanadium content were prepared by impregnation using three different titania carrier materials of varying surface area. The structure of active vanadium species for ?-picoline oxidation was investigated. Vanadium is mainly in the +5 oxidation state as revealed by electron paramagnetic resonance (EPR) and 51V magic-angle spinning nuclear magnetic resonance (51V MAS NMR) spectroscopy techniques. Diffuse reflectance

Darbha Srinivas; Wolfgang F. Hölderich; Steffen Kujath; Michael H. Valkenberg; Thirumalaiswamy Raja; Lakshi Saikia; Ramona Hinze; Veda Ramaswamy

2008-01-01

425

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

426

Kinetic model for the dimerisation of 1-hexene over a solid phosphoric acid catalyst  

Microsoft Academic Search

Batch kinetic experiments at 150°C, 200°C and 250°C showed that the reaction can be modeled with a three step sequential reaction scheme. This involves firstly linear isomerisation of 1-hexene followed by skeletal isomerisation and finally dimerisation and cracking. The first and last steps in the sequence are modeled as reversible reactions. When first order reaction kinetics is assumed for each

Renier Schwarzer; Elizabeth du Toit; Willie Nicol

2008-01-01

427

Hydroisomerization and hydrocracking of alkanes. 7. Influence of the balance between acid and hydrogenating functions on the transformation of n-decane on PtHY catalysts  

SciTech Connect

The transformation of n-decane was studied at 473 K, 101 kPa and pH{sub 2}/p{sub n-decane} = 9 on a series of PtHY catalysts containing from 0.02 to 1.5 wt% platinum and with Si/Al atomic ratios of 3, 9, or 35. The ratio between the number of accessible Pt atoms and the number of acid sites on which the heat of ammonia adsorption is greater than 100 kJ mol{sup -1} (n{sub Pt}/n{sub A}) was chosen for characterizing the balance between the hydrogenating and the acid functions. The activities, stabilities, and selectivities of the catalysts are definitely governed by this balance. For low values of N{sub Pt}/n{sub A} (<0.03), the activity per acid site is low, the deactivation is rapid and n-decane leads directly to all the isomerization and cracking products. For high values ({ge}0.17) the activity per acid sites is maximal, the deactivation is very slow and n-decane transforms successively into monobranched isomers, dibranched isomers, and tribranched isomers plus cracking products. In this latter case the catalyst can be considered as an ideal bifunctional catalyst, namely a catalyst on which only one transformation of the alkene intermediates on the acid sites can occur during their diffusion from the platinum sites on which they are generated to those on which they are hydrogenated. Therefore the reaction scheme of n-decane transformation matches the reaction scheme of olefinic intermediates. From the product distribution established on ideal catalysts the mechanism of the transformation of olefinic intermediates can be deduced. Branching isomerization occurs through protonated cyclopropane and cyclobutane intermediates. 29 refs., 9 figs., 5 tabs.

Alvarez, F.; Ribeiro, F.R. [Instituto Superior Tecnico, Lisboa Codex (Portugal)] [Instituto Superior Tecnico, Lisboa Codex (Portugal); Perot, G.; Thomazeau, C. [Universite de Poitiers (France)] [Universite de Poitiers (France)

1996-09-01

428

Two-Stage Conversion of High Free Fatty Acid Jatropha curcas Oil to Biodiesel Using Br?nsted 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.

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

2014-01-01

429

Partial oxidation of methane on silica-supported silicomolybdic acid catalysts in an excess amount of water vapor  

SciTech Connect

Partial oxidation of methane into oxygenates such as methanol and formaldehyde on highly dispersed MoO{sub 3}/SiO{sub 2} catalysts was studied in an excess amount of water vapor. The reaction was carried out at 873 K using gases consisting of oxygen, methane, and water vapor. The selectivity of oxygenates was found to be a strong function of water vapor, and increased as the fraction of water vapor in a feed gas increased. Inversely, the selectivity of CO and CO{sub 2} in the products decreased as the fraction of water vapor increased. This is ascribed to the formation of silicomolybdic acid (SMA:H{sub 4}SiMo{sub 12}O{sub 40}) over the silica surface during the reaction, partially evidenced by IR measurements. Accordingly, silica-supported SMA catalysts were prepared and applied to the partial oxidation of methane under the same conditions as described above to see if SMA works as the active species for the reaction. Although SMA easily decomposed into SiO{sub 2} and MoO{sub 3} at 873 K without water vapor, it worked well for the production of oxygenates when the fraction of water vapor was more than 50% in the feed gas. The yield of oxygenates increased up to 20% of methane as the fraction of water vapor was around 60%; methane conversion was about 25% and the selectivity of oxygenates was 90%. In this paper, the authors will emphasize that SMA formed on the silica surface are the active species of silica-supported MoO{sub 3} catalysts for the partial oxidation of methane in an excess amount of water vapor.

Sugino, Tomomi; Kido, Ayako; Azuma, Naoto; Ueno, Akifumi; Udagawa, Yasuo

2000-02-15

430

The lactate dehydrogenase catalyzed pyruvate adduct reaction: simultaneous general acid-base catalysis involving an enzyme and an external catalyst.  

PubMed

The pH dependence of the reaction catalyzed by lactate dehydrogenase, where pyruvate adds covalently to NAD to yield a NAD-Pyr adduct, together with published data on the pH dependence of parameters in the normal redox reaction suggests similar binding modes for enolpyruvate and lactate in their complexes with E X NAD (where E is one-fourth of the tetramer), for ketopyruvate in its complexes with the protonated species, E X H X NAD and E X H X NADH, and for the NAD--Pyr adduct and NADH plus pyruvate in their complexes with E X H. These similarities, together with previous data, suggest a reaction scheme for the formation of the enzyme-adduct complex that includes the relevant proton-transfer steps. Seven different amine chloride buffers were used in a study of the reverse adduct reaction, i.e., the decomposition of E X H X NAD--Pyr. These act with varying efficiencies as external general acid catalysts; the enzyme apparently acts as a (internal) general base. The involvement of the amine chloride buffers as external general catalysts is supported by the concentration dependence of the buffer effect, by a Brönsted plot, and by solvent deuterium isotope effects. The involvement of the enzyme as an internal general catalyst is inferred from the pH dependence of the reaction and the identities of the nearby groups in the E X H X NAD--Pyr complex (from crystallographic studies). The dependence of the adduct reaction on chloride concentration indicates the presence of dead-end inhibitor complexes of E X H X Cl and E X H X NAD X Cl. Chloride also accelerates the decomposition of the adduct in the complex E X H X NAD--Pyr by binding to this complex. PMID:6477888

Burgner, J W; Ray, W J

1984-07-31

431

Bio-inspired amino acid oxidation by a non-heme iron catalyst.  

PubMed

This study reports the kinetics and mechanism of Fe(III)-catalyzed oxidative decarboxylation and deamination of a series of acyclic (?-aminoisobutyric acid, ?-(methylamino)isobutyric acid, alanine, norvaline, and 2-aminobutyric acid) and cyclic (1-aminocyclopropane-1-carboxylic acid, 1-amino-1-cyclobutanecarboxylic acid, 1-aminocyclopentanecarboxylic acid, and 1-aminocyclohexanecarboxylicacid) amino acids using hydrogen peroxide, t-butyl hydroperoxide, iodosylbenzene, m-chloroperbenzoic acid, and peroxomonosulphate as oxidant in 75% DMF-25% water solvent mixture. Model complex [Fe(IV)O(SALEN)](•+) (SALENH2: N,N'-bis(salicylidene)ethylenediamine) was generated by the reaction of Fe(III)(SALEN)Cl and H2O2 in CH3CN at 278 K as reported earlier. This method provided us high-valent oxoiron species, stable enough to ensure the direct observation of the reaction with amino acids. PMID:23528571

Góger, Szabina; Bogáth, Dóra; Baráth, Gábor; Simaan, A Jalila; Speier, Gábor; Kaizer, József

2013-06-01

432

Unusual catalysts from molasses: synthesis, properties and application in obtaining biofuels from algae.  

PubMed

Acid catalysts were prepared by sulfonation of carbon materials obtained from the pyrolysis of sugar beet molasses, a cheap, viscous byproduct in the processing of sugar beets into sugar. Conditions for the pyrolysis of molasses (temperature and time) influenced catalyst performance; the best combination came from pyrolysis at low temperature (420 °C) for a relatively long time (8-15 h), which ensured better stability of the final material. The most effective molasses catalyst was highly active in the esterification of fatty acids with methanol (100 % yield after 3 h) and more active than common solid acidic catalysts in the transesterification of vegetable oils with 25-75 wt % of acid content (55-96 % yield after 8 h). A tandem process using a solid acid molasses catalyst and potassium hydroxide in methanol was developed to de-acidificate and transesterificate algal oils from Chlamydomonas reinhardtii, Nannochloropsis gaditana, and Phaeodactylum tricornutum, which contain high amounts of free fatty acids. The amount of catalyst required for the de-acidification step was influenced by the chemical composition of the algal oil, thus operational conditions were determined not only in relation to free fatty acids content in the oil, but according to the composition of the lipid extract of each algal species. PMID:22678658

Samorì, Chiara; Torri, Cristian; Fabbri, Daniele; Falini, Giuseppe; Faraloni, Cecilia; Galletti, Paola; Spera, Silvia; Tagliavini, Emilio; Torzillo, Giuseppe

2012-08-01

433

Functional gel-type resin based palladium catalysts: The role of polymer properties in the hydrogenation of the C C bond of maleic and fumaric acids, the isomers of dicarboxylic acids  

Microsoft Academic Search

Functional gel-type resins (OFP) composed of 2-hydroxyethyl methacrylate (HEMA, 20mol%), styrene (60–77mol%) and diethylene glycol dimethacrylate, the crosslinking reagent (DEGDMA, 3–20mol%) are used as supports for palladium catalysts (0.25–2wt% Pd). The influence of polymer mass expansion on the activity of Pd\\/OFP catalysts in the hydrogenation of cis- and trans-isomers of unsaturated dicarboxylic acids, maleic (MA) and fumaric (FA), is examined.

A. Drelinkiewicz; A. Knapik; A. Waksmundzka-Góra; A. Bukowska; W. Bukowski; J. Noworól

2008-01-01

434

Selective oxidation of propane to acrylic acid on K-doped MoVSbO catalysts: catalyst characterization and catalytic performance  

Microsoft Academic Search

K-doped MoVSb mixed oxides catalysts have been prepared by impregnation of a MoVSbO mixed oxide (previously prepared by hydrothermal synthesis) with an aqueous solution of potassium nitrate, characterized by XRD, SEM-EDX, EPR, XPS, XANES, and FTIR of adsorbed NH3, and tested in the selective oxidation of propane and propylene in the 593–693 K temperature range. The undoped MoVSbO catalysts presented

T. Blasco; P. Botella; P. Concepción; J. M. López Nieto; A. Martinez-Arias; C. Prieto

2004-01-01

435

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 (40kHz, 300W) 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

436

Acid strength of solids probed by catalytic isobutane conversion  

Microsoft Academic Search

The literature is controversial on whether sulfated zirconia (SZ) is “just” as strong acid as H-zeolites, or a strong superacid. Spectroscopic studies of adsorbed probe molecules concluded that SZ is not a superacid, whereas acidity measurements based on Hammett indicators, alkane transformations and the 1\\/2% isobutane conversion test [B. Umansky, J. Engelhardt, W.K. Hall, J. Catal. 127 (1991) 128; D.

Dan Fraenkel; Nicholas R. Jentzsch; Christopher A. Starr; Pandurang V. Nikrad

2010-01-01

437

Synthesis of fatty acid methyl ester from crude jatropha (Jatropha curcas Linnaeus) oil using aluminium oxide modified Mg-Zn heterogeneous catalyst.  

PubMed

The synthesis of fatty acid methyl esters (FAME) as a substitute to petroleum diesel was investigated in this study from crude jatropha oil (CJO), a non-edible, low-cost alternative feedstock, using aluminium modified heterogeneous basic oxide (Mg-Zn) catalyst. The transesterification reaction with methanol to methyl esters yielded 94% in 6h with methanol-oil ratio of 11:1, catalyst loading of 8.68 wt.% at 182°C and the properties of CJO fuel produced were determine and found to be comparable to the standards according to ASTM. In the range of experimental parameters investigated, it showed that the catalyst is selective to production of methyl esters from oil with high free fatty acid (FFA) and water content of 7.23% and 3.28%, respectively in a single stage process. Thus, jatropha oil is a promising feedstock for methyl ester production and large scale cultivation will help to reduce the product cost. PMID:21486692

Olutoye, M A; Hameed, B H

2011-06-01

438

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.

2010-01-01

439

Preparation and characterization of mesoporous N-doped and sulfuric acid treated anatase TiO{sub 2} catalysts and their photocatalytic activity under UV and Vis illumination  

SciTech Connect

Nitrogen-doped TiO{sub 2} catalysts were prepared by a precipitation method. The samples were calcined at 400 deg. C for 4 h in air. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), low temperature N{sub 2}-adsorption was used for structural characterization and UV-diffuse reflectance (UV-DR) was applied to investigate the optical properties of the as-prepared samples. It was found that microporous N-doped catalysts have solely anatase crystalline structure. Acidic treatment of the calcined samples was performed using sulfuric acid agitation. The crystalline structure remained unchanged due to surface treatment, while the porosity and the surface areas (a{sub BET}{sup S}) were decreased dramatically. Optical characterization of the doped catalysts showed that they could be excited by visible light photons in the 400-500 nm wavelength range (lambda{sub g,1}={approx}390 nm, lambda{sub g,2}={approx}510 nm). It was also established that surface treatment enhances the Vis-light absorption of the N-TiO{sub 2} powders. Finally the catalysts were tested in the photocatalytic degradation of phenol in aqueous suspensions. Two different light sources were used; one of them was a UV-rich high pressure Hg-lamp, while the other was a tubular visible light source. We found that using visible light illumination N-doped, acid treated TiO{sub 2} samples were more catalytically active than non-doped TiO{sub 2} catalysts. - Graphical abstract: The effect of the acid treatment on the visible-light-driven photocatalytic activity of the N-doped, anatase TiO{sub 2} catalysts.

Kun, Robert [Supramolecular and Nanostructured Materials Research Group of the Hungarian Academy of Sciences, University of Szeged, Aradi vt. 1, H-6720 Szeged (Hungary); Tarjan, Sandor [Department of Colloid Chemistry, University of Szeged, Aradi vt. 1, H-6720 Szeged (Hungary); Oszko, Albert [Department of Solid State and Radiochemistry, University of Szeged, Aradi vt. 1, H-6720 Szeged (Hungary); Seemann, Torben; Zoellmer, Volker; Busse, Matthias [Fraunhofer Institute for Manufacturing Technology and Applied Materials Research, IFAM, Wienerstrasse 12, 28359 Bremen (Germany); Dekany, Imre, E-mail: i.dekany@chem.u-szeged.h [Supramolecular and Nanostructured Materials Research Group of the Hungarian Academy of Sciences, University of Szeged, Aradi vt. 1, H-6720 Szeged (Hungary); Department of Colloid Chemistry, University of Szeged, Aradi vt. 1, H-6720 Szeged (Hungary)

2009-11-15

440

Simultaneous formation of nitrogen and sulfur-doped transition metal catalysts for oxygen reduction reaction through pyrolyzing carbon-supported copper phthalocyanine tetrasulfonic acid tetrasodium salt  

NASA Astrophysics Data System (ADS)

In this work, we report a spontaneous formation of copper (Cu-N-S/C) catalysts containing both nitrogen (N) and sulfur (S) elements using a one-step pyrolysis of carbon supported copper phthalocyanine tetrasulfonic acid tetrasodium salt (CuTSPc/C). The obtained catalysts exhibit high catalytic activities for oxygen reduction reaction (ORR) in alkaline media. Through electrochemical measurements and physical characterizations, several observations are reached as follows: (1) different pyrolysis temperatures can result in different catalyst structures and performances, and the optimum pyrolysis temperature is found to be 700 °C; (2) the electron transfer number of the ORR process catalyzed by the unpyrolyzed catalyst is about 2.5, after the pyrolysis, this number is increased to 3.5, indicating that the pyrolysis process can change the ORR pathway from a 2-electron transfer dominated process to a 4-electron transfer dominated one; (3) increasing catalyst loading from 40 ?g cm-2 to 505 ?g cm-2 can effectively improve the catalytic ORR activity, under which the percentage of H2O2 produced decreases sharply from 39.5% to 7.8%; and (4) the Cu ion can bond on pyridinic-N, graphite-N and C-Sn-C to form Cu-N-S/C catalyst active sites, which play the key role in the ORR activity.

Qing, Xin; Shi, Jingjing; Ma, Chengyu; Fan, Mengyang; Bai, Zhengyu; Chen, Zhongwei; Qiao, Jinli; Zhang, Jiujun

2014-11-01