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1

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

PubMed

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

Viladoms, Júlia; Fedor, Martha J

2012-11-09

2

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

3

New and General Nitrogen Heterocycle Synthesis: Use of Heteropoly Acids as a Heterogeneous Recyclable Catalyst  

Microsoft Academic Search

An efficient synthetic method of six- and five-member nitrogen heterocyclic compounds was developed. Nitrogen heterocyclic compounds were prepared by condensation of the ?-dicarbonyl compounds with the corresponding ?- or ?-amino alcohols, subsequent cyclization, and spontaneous aromatization in the presence of a catalytic amount of Keggin-type heteropoly acids under very mild conditions.

Rahim Hekmatshoar; Sodeh Sadjadi; Samaheh Sadjadi; Majid M. Heravi; Yahya S. Beheshtiha; Fatemeh F. Bamoharram

2010-01-01

4

Esterification of Fatty Acid by Zirconic Catalysts  

Microsoft Academic Search

Sulfated zirconia (SO4\\u000a 2?\\/ZrO2) was proved as an efficient catalyst for the esterification of fatty acids and alcohols, the alkyl esters of long chain fatty\\u000a acids are wildly used in industry and daily life. In this paper, the esterification of long chain fatty acid (both saturated\\u000a and unsaturated) with simple alcohol catalyzed by SZ catalyst was presented. It is found

Xiaoting Hu; Zheng Zhou; Defang Sun; Yuantao Wang; Zhibing Zhang

2009-01-01

5

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

2013-05-24

6

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

7

Dehydration of glycerol over niobia-supported silicotungstic acid catalysts.  

PubMed

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

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

2013-01-01

8

Catalyst and electrode research for phosphoric acid fuel cells  

Microsoft Academic Search

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

A. C. Antoine; R. B. King

1987-01-01

9

Catalyst and electrode research for phosphoric acid fuel cells  

NASA Astrophysics Data System (ADS)

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.

10

Modified zirconia solid acid catalysts for organic synthesis and transformations  

Microsoft Academic Search

A series of sulfate, molybdate and tungstate promoted ZrO2 catalysts were prepared by wet impregnation method. To incorporate these promoters to Zr(OH)4, sulfuric acid, ammonium heptamolybdate, and ammonium metatungstate were used as precursors, respectively. Further, a Pt promoted Mo-ZrO2 catalyst was also prepared separately by impregnating with hexachloroplatinic acid. The surface and bulk properties of various promoted ZrO2 catalysts were

Benjaram M. Reddy; Pavani M. Sreekanth; Vangala R. Reddy

2005-01-01

11

Hydrolysis of disaccharides over solid acid catalysts under green conditions  

Microsoft Academic Search

The hydrolysis of the three most important disaccharides: sucrose, maltose and cellobiose, has been comparatively studied in mild conditions (50–80°C) in water over several solid acid catalysts. Strong acidic resins (Amberlite A120 and A200), mixed oxides (silica-alumina and silica-zirconia), and niobium-containing solids (niobic acid, silica-niobia, and niobium phosphate) have been chosen as acid catalysts. The hydrolysis activity was studied in

Matteo Marzo; Antonella Gervasini; Paolo Carniti

12

Acetone condensation reaction on acid catalysts  

SciTech Connect

The condensation reaction of acetone on alumina and acid zeolites has been followed by FTIR. Under identical conditions, the reaction rate is faster on alumina, and the condensation goes beyond the formation of mesityl oxide. Zeolites without nonframework aluminum are poor catalysts. On HZSM-5 the reaction is about two orders of magnitude slower than on USY at 105 C. From these data, it appears that Lewis sites, even if they bound acetone less energetically than Broensted sites, are responsible for the activation of the molecule. On alumina, the reaction would take place between gas phase acetone and acetone adsorbed on Lewis sites. On zeolites with nonframework aluminum and, thus, with Lewis sites, the reaction would involve acetone molecules adsorbed on Broensted and Lewis sites, the activation occurring on the Lewis site.

Panov, A.G.; Fripiat, J.J. [Univ. of Wisconsin, Milwaukee, WI (United States)

1998-08-15

13

Hydrogen from formic acid decomposition over Pd and Au catalysts  

Microsoft Academic Search

Vapour phase decomposition of formic acid has been studied systematically over a range of catalysts: 1.0 and 10wt.% Pd\\/C, 0.8wt.% Au\\/C and 1.0wt.% Au\\/TiO2. The mean metal particle size of these materials was estimated by HRTEM and turnover frequencies were calculated using these data. The Au\\/C catalyst was the least active and the Pd\\/C catalysts were the most active for

Dmitri A. Bulushev; Sergey Beloshapkin; Julian R. H. Ross

2010-01-01

14

Single event microkinetics of hydrocarbon cracking on acid catalysts  

Microsoft Academic Search

Zeolite catalysts are the workhorses of oil refining indust ry. Main applications, among many others, are fluid catalytic cr acking, hy- drocracking and aromatics transformations. The use of zeolites for hydro- carbon conversions is based on their acid properties and their framework topology. This work aims at investigating the influence of th ese catalyst properties on the rates of the

Rhona Van Borm

15

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

16

Organometallic catalysts for primary phosphoric acid fuel cells  

Microsoft Academic Search

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

Fraser Walsh

1987-01-01

17

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 ...

18

Esterification of acidic oils over a versatile amorphous solid catalyst.  

PubMed

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

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

2009-01-01

19

Acetylation of glycerol to synthesize bioadditives over niobic acid supported tungstophosphoric acid catalysts  

Microsoft Academic Search

Acetylation of glycerol to yield mono, di and triacetin (acetylated glycerol) was carried over niobic acid supported tungstophosphoric acid (TPA) catalysts. The catalysts with varying TPA content were prepared and characterized by different techniques. The characterization results reveal the presence of well-dispersed Keggin ion on support. The results suggest that the glycerol conversion and selectivities depend on the acidity of

M. Balaraju; P. Nikhitha; K. Jagadeeswaraiah; K. Srilatha; P. S. Sai Prasad; N. Lingaiah

2010-01-01

20

Environmentally benign synthesis of h-phosphinic acids using a water-tolerant, recyclable polymer-supported catalyst.  

PubMed

[reaction: see text] A reusable polymer-supported hydrophosphinylation catalyst is described for the preparation of H-phosphinic acids. The polystyrene-based ligand is prepared in one step from commercially available compounds. The polymeric catalyst generally gives good yields for a variety of substrates and is water- and air-tolerant, although the scope of alkenes and alkynes which can be employed is somewhat narrower than with our original xantphos/Pd(2)dba(3) catalyst. PMID:15469354

Deprèle, Sylvine; Montchamp, Jean-Luc

2004-10-14

21

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

2011-12-09

22

Impacts of acid gases on mercury oxidation across SCR catalyst  

Microsoft Academic Search

A series of bench-scale experiments were completed to evaluate acid gases of HCl, SO2, and SO3 on mercury oxidation across a commercial selective catalytic reduction (SCR) catalyst. The SCR catalyst was placed in a simulated flue gas stream containing O2, CO2, H2O, NO, NO2, and NH3, and N2. HCl, SO2, and SO3 were added to the gas stream either separately

Ye Zhuang; Jason Laumb; Richard Liggett; Mike Holmes; John Pavlish

2007-01-01

23

Perfluorinated resinsulfonic acid--a catalyst for certain organic reactions  

SciTech Connect

The purpose of this work was to examine the possibility of using, as a catalyst in certain organic reactions, the perfluorinated resinsulfonic acid F-4SK in the H form, which is an analog of the perfluorinated resinsulfonic acid Nafion-H.

Etlis, V.S.; Beshenova, E.P.; Semenova, E.A.; Shomina, F.N.; Dreiman, N.A.; Balaev, G.A.

1986-09-10

24

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

25

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

26

Heteropoly compounds as catalysts for hydrogenation of propanoic acid  

Microsoft Academic Search

Bulk Keggin heteropoly acids (HPAs) H3+n[PMo12?nVnO40] (n=0–2) and their Cs+ salts catalyse the vapour-phase hydrogenation of propanoic acid at 350?°C and 1 bar H2 pressure, yielding propanal together with 3-pentanone and propane as the main products. Catalyst acidity (controlled by Cs substitution) has crucial effect on the reaction selectivity. As the Cs content increases, the selectivity to propanal passes a

H. Benaissa; P. N. Davey; Y. Z. Khimyak; I. V. Kozhevnikov

2008-01-01

27

Organometallic catalysts for primary phosphoric acid fuel cells  

NASA Astrophysics Data System (ADS)

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

1987-03-01

28

Process for the generation of α,β-unsaturated carboxylic acids and esters using niobium catalyst  

Microsoft Academic Search

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 α,β-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

M. R. Gogate; J. J. Spivey; J. R. Zoeller

1999-01-01

29

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

Microsoft Academic Search

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

Makarand Ratnakav Gogate; James Jerome Spivey; Joseph Robert Zoeller

1999-01-01

30

Hydrolysis of disaccharides over solid acid catalysts under green conditions.  

PubMed

The hydrolysis of the three most important disaccharides: sucrose, maltose and cellobiose, has been comparatively studied in mild conditions (50-80°C) in water over several solid acid catalysts. Strong acidic resins (Amberlite A120 and A200), mixed oxides (silica-alumina and silica-zirconia), and niobium-containing solids (niobic acid, silica-niobia, and niobium phosphate) have been chosen as acid catalysts. The hydrolysis activity was studied in a continuous reactor with fixed catalytic bed working in total recirculation mode. Rate constants and activation parameters of the hydrolysis reactions have been obtained and discussed comparing the reactivity of the ?-1,?-2-, ?-1,4-, and ?-1,4-glycosidic bonds of the employed disaccharides. The following order of reactivity was found: sucrose > maltose > cellobiose. The sulfonic acidic resins, as expected, gave complete sucrose conversion at 80°C and good conversions for cellobiose and maltose. Among the other catalysts, niobium phosphate provided the most interesting results toward the disaccharide hydrolysis, which are here presented for the first time. Relations between activity and surface acid properties are discussed. PMID:22127325

Marzo, Matteo; Gervasini, Antonella; Carniti, Paolo

2011-10-17

31

Acidity and reactivity of trifluoromethanesulfonic acid in liquid and solid acid catalysts  

Microsoft Academic Search

The acidic properties of CF3SO3H\\/SiO2 acid catalysts have been investigated by the protonation of weak bases (B) (B+H+?BH+) and the proton-transfer process from (H+A?) to (BH+A?) has been analysed by a thermodynamic procedure used to account the variation of the activity coefficient terms of the species involved. Acid–base systems with different substituted pyridines as back-titrating agents of BH+ (i.e. BH+?B)

Nunziata Clara Marziano; Lucio Ronchin; Claudio Tortato; Armando Zingales; Abdiqafar A Sheikh-Osman

2001-01-01

32

Cumene cracking on dodecatungstosilicic acid catalyst  

SciTech Connect

Cumene cracking on supported H{sub 4}SiW{sub 12}O{sub 40} was studied in the temperature range 150-244{degrees}C using a constant flow microreactor. In the initial periods of runs, besides the two predominant products benzene and propylene some less important amounts of C{sub 4}, C{sub 5}, and C{sub 6} hydrocarbons as well as toluene and ethylbenzene were obtained. Based on these results and separate experiments with propylene and benzene, a reaction pattern was proposed. The side products vanished after some 10-20 min of run time during which there was rapid deactivation of the catalyst and a decrease from an initially high conversion to 20-30% conversion depending on temperature. From the mass balance the amount of carbonaceous deposit was estimated and it was shown that the precursors for its formation are propylene and cumene. Arrhenius plots of the rate constants at a given coking degree indicate that below 170{degrees}C at low coking degree it is the surface reaction which is the rate controlling factor. Above this temperature the reaction is predominantly a diffusion controlled process. 23 refs., 11 figs., 1 tab.

Malecka, A. [Polish Academy of Sciences, Krakow (Poland)

1997-01-15

33

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

34

Efficient Dehydrogenation of Formic Acid Using an Iron Catalyst  

Microsoft Academic Search

Hydrogen is one of the essential reactants in the chemical industry, though its generation from renewable sources and storage in a safe and reversible manner remain challenging. Formic acid (HCO2H or FA) is a promising source and storage material in this respect. Here, we present a highly active iron catalyst system for the liberation of H2 from FA. Applying 0.005

Albert Boddien; Dörthe Mellmann; Felix Gärtner; Ralf Jackstell; Henrik Junge; Paul J. Dyson; Gábor Laurenczy; Ralf Ludwig; Matthias Beller

2011-01-01

35

Catalytic decomposition of formic acid on oxide catalysts  

Microsoft Academic Search

In our previous paper [M.A. Borowiak, M.H. Jamróz, R. Larsson, J. Mol. Catal. A: Chem., 139 (1999) 97], an impulse-oscillation model (IOM) was used for a time description of catalytic acts in the reactions of catalytic decomposition of formic acid on oxide catalysts for unimolecular mechanism. In this paper the bimolecular mechanism were modelled for the same reactions. The results

Marek A Borowiak; Micha? H Jamróz; Ragnar Larsson

2000-01-01

36

General expression for primary characterization of catalyst activity using TAP pulse response experiment  

Microsoft Academic Search

A general expression for primary catalyst characterization using TAP pulse response data has been obtained for porous and non-porous catalysts, and for one- and two-step irreversible catalytic reactions. Using this expression or the corresponding nomogram, the apparent kinetic parameter can be obtained.

G. S. Yablonsky; S. O. Shekhtman; P. Phanawadee; J. T. Gleaves

2001-01-01

37

A nanoparticle catalyst with superior activity for electrooxidation of formic acid  

Microsoft Academic Search

This paper reports the synthesis and characterization of a series of Pt-based nanoparticle catalysts with high activity for formic acid electrooxidation. The catalysts were prepared using spontaneous deposition to decorate platinum nanoparticles with controlled amounts of palladium and palladium\\/ruthenium. Among all the catalysts investigated, the Pt\\/Pd catalyst shows the best performance; the steady-state formic acid oxidation current is ca. 1mAcm?2

Piotr Waszczuk; Thomas M Barnard; Cynthia Rice; Richard I Masel; Andrzej Wieckowski

2002-01-01

38

BIFUNCTIONAL Nb\\/Ti-MCM-41 CATALYST IN OXIDATIVE ACIDIC REACTION OF CYCLOHEXENE TO DIOL  

Microsoft Academic Search

Bifunctional oxidative and acidic catalyst was prepared by incorporating titanium ion (Ti4+) and niobic acid in mesoporous molecular sieves MCM -41 structure. The catalyst is active both in oxidation, and acid-catalyzed reaction of olefin to diol. Nb\\/Ti-MCM -41 catalyst was prepared by first synthesizing Ti-MCM -41 by hydrothermal method, followed by subsequent impregnation of niobic acid (Nb) into Ti-MCM -41

Zainab Ramli; Mazidah Abdul Shukor; Didik Prasetyoko

39

New catalysts and new electrolytes for acid fuel cells  

NASA Astrophysics Data System (ADS)

Based on the characterization studies and the behavior of the model systems, it appears that the promotion effect of oxides of Ti, V, Zr, Ta and Cr is probably not truly catalytic. The most probable mechanisms are changes in physical properties of the Pt catalyst in the dry state which result in improved electrode performance due to two effects: (1) at Pt crystallite shape/morphology effort, where the base metal oxide acts to impede Pt crystallite size growth (b coalescence) but alloys surface diffusion to occur and equilibrium shapes to form during heat treatment; and (2) the oxide acts as a flux for improving the wetability of the catalyst when fabricated into a gas diffusion electrode, resulting in higher catalyst layer effectiveness. Both of these effects have been discussed in the literature, but not with respect to how additives or promoters might relate to such effects. Recent work has shown that use of concentrated trifluoromethane sulfonic acid (TFMSA) in place of concentrated phosphoric acid enhances the activity of standard Pt electrodes for oxygen reduction by 40 mV (which could improve the heat rate of first-generation fuel cells by 400 Btu/kWh).

Ross, P. N.; Appleby, A. J.

1985-02-01

40

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

2012-12-20

41

Catalytic reduction of U(VI) with formic acid in acid solutions on palladium catalysts  

Microsoft Academic Search

The kinetics of catalytic reduction of U(VI) with formic acid in H2SO4 solutions in the presence of Pd\\/SiO2 catalysts differing in the size of nanocrystallites of the active metal was studied. A decrease in the size of supported\\u000a Pd particles leads to a decrease in the specific activity of the catalyst, i.e., the catalytic centers located on large crystallites\\u000a exhibit

M. Yu. Boltoeva; V. P. Shilov; A. V. Anan’ev

2008-01-01

42

[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

43

Oxidation of glyoxal to glyoxylic acid by oxygen over V 2O 5\\/C catalyst  

Microsoft Academic Search

A novel vanadium oxide catalyst supported on active carbon was prepared by an incipient wetness impregnation method, and the precursor was obtained from oxalic acid aqueous solutions of NH4VO3. The catalyst was applied liquid phase oxidation of glyoxal to glyoxylic acid. It was found that V2O5\\/C catalyst exhibited obvious activity for glyoxal oxidation. Glyoxylic acid could be obtained without pH

Yu Lan Niu; Zheng Xu; Min Li; Rui Feng Li

2008-01-01

44

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

Microsoft Academic Search

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

Xuezheng Liang; Jianguo Yang

2009-01-01

45

Enantioselective hydrogenation of isophorone over Pd catalysts in the presence of(?)-dihydroapovincaminic acid ethyl ester  

Microsoft Academic Search

The enantioselective heterogeneous catalytic hydrogenation of isophorone in the presence of apovincaminic acid ethyl ester was investigated. Various Pd black catalysts differing in their preparation method were studied. The catalysts were characterized by different methods such as physical adsorption and chemisorption, SEM and XPS. An explanation was created for the different enantioselectivity of the catalysts being precipitated by different reducing

G Farkas; É S??pos; A Tungler; A Sárkány; J. L Figueiredo

2001-01-01

46

Sulfuric acid on silica-gel: an inexpensive catalyst for aromatic nitration  

Microsoft Academic Search

Solid acidic catalysts made of sulfuric acid supported on silica-gel and their application to the nitration of aromatics with nitric acid and isopropyl nitrate are described. Substrates with very different levels of activation were investigated. Methods to overcome the poisoning produced by water and to tune the catalyst activity according to the reactivity of the substrate are outlined.

Juan M Riego; Zeno Sedin; JoséM Zaldívar; Nunziata C Marziano; Claudio Tortato

1996-01-01

47

Decarboxylative coupling of heptanoic acid. Manganese, cerium and zirconium oxides as catalysts  

Microsoft Academic Search

A series of catalysts containing 20wt.% of Mn, Ce and Zr oxides deposited on Al2O3, SiO2 and TiO2 has been studied in ketonisation of heptanoic acid. The most pronounced effect of alumina support on catalysts activity has been noted. Manganese oxide catalysts have shown the highest activity. The dependence of the concentration of MnO2 active phase on catalyst activity has

M Gli?ski; J Kije?ski

2000-01-01

48

Deactivation of a solid acid hydrocarbon conversion catalyst  

SciTech Connect

The activity, selectivity and stability of catalyst are considered in designing and screening of a potential catalyst for chemical processes. Of these, stability (i.e., resistance to deactivation) is one of the most important aspects of the catalyst. Even though there are some chemical processes that utilize fast deactivating catalysts (such as FCC), catalysts with too short lifetimes do not usually become commercialized. The deactivated catalyst can sometimes be regenerated depending on the deactivation mechanism, but most often, is simply discarded. Even if regeneration of the catalyst is possible, the down time associated with removing and loading of the catalyst has such a large impact on the economics of the process that the use of fast deactivating but regenerable catalyst is often discouraged. Therefore, catalyst stability is important in determining whether a catalyst is used commercially or not. Lately, sulfated zirconia (SZ) has been attracting a lot of attention as a potential replacement for alkane isomerization and alkylation catalysts and as a part of a Fischer-Tropsch synthesis catalyst. One shortcoming of SZ catalysts for hydrocarbon conversion is the fast deactivation of the catalysts as usually seen during n-butane isomerization. Understanding the deactivation mechanism of SZ can aid in designing a more deactivation resistant SZ catalyst that can be utilized in other hydrocarbon processes. In this study, the authors report on the changes in the concentration of active sites on SZ with TOS during n-butane isomerization at 150 C.

Kim, S.Y.; Goodwin, J.G. Jr.

1999-07-01

49

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

50

Hydrogenation of lactic acid to propylene glycol over copper-containing catalysts  

Microsoft Academic Search

Catalytic properties of different copper-containing catalysts synthesized from different precursors were studied in the hydrogenation\\u000a of lactic acid at mild conditions. The most active catalyst was found to be chrysocolla-like copper hydroxysilicate with the\\u000a copper loading of about 50 at%. At the optimal reaction conditions (T = 473 K, WHSV = 0.08 h?1), 95% conversion of lactic acid over this catalyst and 65% selectivity to 1,2-propylene glycol

Mikhail N. Simonov; Irina L. Simakova; Valentin N. Parmon

2009-01-01

51

Catalytic wet air oxidation of butyric acid solutions using carbon-supported iridium catalysts  

Microsoft Academic Search

Aqueous solutions of butyric acid were treated by catalytic wet air oxidation using carbon-supported iridium catalysts in a stirred reactor. Under the operating conditions of 6.9bar of oxygen partial pressure and 200°C of temperature, conversions up to 52.9% after 2h were obtained depending on the type of catalyst used. The effects of butyric acid initial concentration, loading of catalyst, oxygen

H. T Gomes; J. L Figueiredo; J. L Faria

2002-01-01

52

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

Microsoft Academic Search

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

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

2004-01-01

53

New Non-noble Metal Anode Catalysts for Acid Fuel Cells  

Microsoft Academic Search

NOBLE metals have been found to be the most suitable materials as anode catalysts for hydrogen oxidation in low temperature fuel cells containing an acid electrolyte. The one exception is tungsten carbide1, which is the only compound to have shown catalytic activity and sufficient resistance against corrosion in acid media under anodic polarization to act as an anode catalyst. In

Harald Böhm

1970-01-01

54

Influence of Catalyst (Citric Acid) Concentration on the Physical Properties of TEOS Silica Aerogels  

Microsoft Academic Search

In the present paper, the experimental results on the influence of catalyst (citric acid) concentration on the physical properties of TEOS silica aerogels, are reported. The aerogels have been prepared by hydrolysis and polycondensation of tetraethoxysilane (TEOS) using citric acid (CTA) as a new catalyst followed by supercritical drying in an autoclave. In order to obtain the best quality silica

P. B. Wagh; A. Venkateswara Rao; D. Haranath

1997-01-01

55

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

2013-02-09

56

Shape Selective Solid Acid Catalysts Based on Tungstophosphoric Acid Supported on Mesoporous Silica  

SciTech Connect

Solid acid catalysts comprising up to 70wt% tungstophosphoric acid (PW) dispersed on three mesoporous silicas with uniform pore size distributions of 18 Angstrom, 30 Angstrom, and 100 Angstrom, as well as on amorphous silica were synthesized. The effects of support pore size and catalyst preparation procedures on the chemical and physical properties of the synthesized catalysts were characterized using 31P magic angle spinning NMR, in-situ X-ray diffraction, and N2 physisorption. It was observed that right pore size of catalyst supports is important for PW dispersion via solution impregnation method and PW is highly dispersed even at a 70wt% loading when the support pore size is greater or equal to 30 Angstrom. Acid neutralization of silica supports and utilization of non-hydrolyzing organic polar solvents such as methanol are required to retain the Keggin structure of PW during sample preparation. The thermal stability of PW is enhanced when it is supported on silica supports. In addition, mesoprous silica with 30 Angstrom uniform pores eexhibits improved PW stability to polar solvent leaching, probably as a result of steric hindrance of the silica support due to the compatible size between the pores of the silica support (30 Angstrom) and the cluster of PW (12 Angstrom).

Wang, Yong (BATTELLE (PACIFIC NW LAB)); Kim, Anthony Y. (BATTELLE (PACIFIC NW LAB)); Li, Xiaohong (BATTELLE (PACIFIC NW LAB)); Wang, Li-Qiong (BATTELLE (PACIFIC NW LAB)); Peden, Charles HF (BATTELLE (PACIFIC NW LAB)); Bunker, Bruce C. (BATTELLE (PACIFIC NW LAB)); Chunshan Song, Juan M. Garces and Yoshihiro Sugi

2000-02-01

57

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

Microsoft Academic Search

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

Ryan K. Zeidan; Mark E. Davis

2007-01-01

58

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

PubMed

Catalytic wet hydrogen peroxide oxidation of acid dye has been explored in this study. Manganese(III) complex of N,N'-ethylene bis(salicylidene-aminato) (salenH(2)) has been encapsulated in super cages of zeolite-Y by flexible ligand method. The catalyst has been characterized by FT-IR, XRD, TG/DTA and nitrogen adsorption studies. The effects of various parameters such as pH, catalyst and hydrogen peroxide concentration on the oxidation of dye were studied. The results indicate that after 20 min at 30 degrees C, 0.175 M H(2)O(2) and 3g/L catalyst, about 90% dye removal was obtained. These studies indicate that manganese-salen complex immobilized on zeolite framework can act as a good heterogeneous catalyst for removal of dye from wastewaters. PMID:16814465

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

2006-05-26

59

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

60

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

PubMed

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

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

2013-03-20

61

Efficient dehydrogenation of formic acid using an iron catalyst.  

PubMed

Hydrogen is one of the essential reactants in the chemical industry, though its generation from renewable sources and storage in a safe and reversible manner remain challenging. Formic acid (HCO(2)H or FA) is a promising source and storage material in this respect. Here, we present a highly active iron catalyst system for the liberation of H(2) from FA. Applying 0.005 mole percent of Fe(BF(4))(2)·6H(2)O and tris[(2-diphenylphosphino)ethyl]phosphine [P(CH(2)CH(2)PPh(2))(3), PP(3)] to a solution of FA in environmentally benign propylene carbonate, with no further additives or base, affords turnover frequencies up to 9425 per hour and a turnover number of more than 92,000 at 80°C. We used in situ nuclear magnetic resonance spectroscopy, kinetic studies, and density functional theory calculations to explain possible reaction mechanisms. PMID:21940890

Boddien, Albert; Mellmann, Dörthe; Gärtner, Felix; Jackstell, Ralf; Junge, Henrik; Dyson, Paul J; Laurenczy, Gábor; Ludwig, Ralf; Beller, Matthias

2011-09-23

62

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

63

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

64

Organometallic catalysts for primary phosphoric acid fuel cells: Final report, 1981-1985  

SciTech Connect

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 h in full cell at 160 to 200C in phosphoric acid (H3PO4), and was shown to provide stable performance.

Walsh, F.

1987-03-01

65

Selective Poisoning and Deactivation of Acid Sites on Sulfated Zirconia Catalysts for n-Butane Isomerization  

Microsoft Academic Search

Reaction kinetics measurements, selective poisoning, and microcalorimetry were used to study the activity, selectivity, and deactivation of acid sites on a sulfated zirconia catalyst forn-butane isomerization at 423 K. The sulfated zirconia catalyst has a distribution of acid site strengths, containing 50 ?mol\\/g of strong acid sites characterized by heats of ammonia adsorption from 125 to 165 kJ\\/mol. The strongest

G. Yaluris; R. B. Larson; J. M. Kobe; M. R. González; K. B. Fogash; J. A. Dumesic

1996-01-01

66

Synthesis of dioctyl phthalate using acid functionalized ionic liquid as catalyst  

Microsoft Academic Search

Dioctyl phthalate were synthesized by using acid functionalized ionic liquid as catalyst. The results indicated that HSO3-functionalized Brønsted acidic ionic liquids show better catalytic and reusable performance than non-functionalized ionic liquids or the combination of neutral ionic liquids and Brønsted acid. Under the optimum conditions, using 1-methyl-3-(3-sulfopropyl)-imidazolium hydrogen sulfate as catalyst, the conversion of phthalic anhydride was 98%. After easily

Hongliang Li; Shitao Yu; Fusheng Liu; Congxia Xie; Lu Li

2007-01-01

67

Hydrogenation process using noble metal catalysts promoted by liquid fluorine containing acids  

Microsoft Academic Search

A process for the hydrogenation of unsaturated hydrocarbon fractions is described which comprises dissolving said unsaturated hydrocarbon fraction in a liquid acid system, said liquid acid system being selected from the group consisting of liquid HF, other liquid Bronsted acid containing fluorine, fluorine containing Friedel-Crafts catalyst (such as BFâ, TaFâ) in liquid HF or other liquid fluorine containing Bronsted acid

Wristers

1978-01-01

68

Comparison of different heterogeneous catalysts and different alcohols for the esterification reaction of oleic acid  

Microsoft Academic Search

Oils with high amount of free fatty acid (FFA) are becoming one of the most promising alternatives to produced biodiesel; due, principally, to it low cost. However, because of the presence of FFA, the conventional basic homogenous catalyst should not be used with the aim to avoid the production of soaps.In this work, different catalysts, such as solid resins, zeolite

J. M. Marchetti; A. F. Errazu

2008-01-01

69

Niobic acid — a new heterogeneous catalyst for processes in petrochemical and organic syntheses  

NASA Astrophysics Data System (ADS)

Questions associated with the application of niobium compounds in catalysis are considered. Niobic acid Nb2O5.nH2O contains an appreciable amount of water, but its surface exhibits a high acidity — equivalent to the acidity of 70% sulfuric acid. This unusual solid acid manifests not only a high activity and sensitivity but also an appreciable stability as a catalyst in reactions in which water is present or is evolved (condensation, hydration, dehydration, and esterification). It may be used also as a catalyst in other reactions. The structure and properties of the surface of niobic acid are examined. The bibliography includes 54 references.

Chernyshkova, F. A.

1993-08-01

70

Syntheses of 5-hydroxymethylfurfural and levoglucosan by selective dehydration of glucose using solid acid and base catalysts  

Microsoft Academic Search

Selective dehydration of glucose, the most abundant monosaccharide, was examined using a solid acid catalyst individually or a combination of solid acid and base catalysts to form anhydroglucose (levoglucosan) or 5-hydroxymethylfurfural (HMF), respectively. Glucose was dehydrated to anhydroglucose by acid catalysis in polar aprotic solvents including N,N-dimethylformamide. Amberlyst-15, a strongly acidic ion-exchange resin, functioned as an efficient solid acid catalyst

Mika Ohara; Atsushi Takagaki; Shun Nishimura; Kohki Ebitani

2010-01-01

71

Platinum nanoparticles–manganese oxide nanorods as novel binary catalysts for formic acid oxidation  

Microsoft Academic Search

The current study proposes a novel binary catalyst system (composed of metal\\/metal oxide nanoparticles) as a promising electrocatalyst in formic acid oxidation. The electro-catalytic oxidation of formic acid is carried out with binary catalysts of Pt nanoparticles (nano-Pt) and manganese oxide nanorods (nano-MnOx) electrodeposited onto glassy carbon (GC) electrodes. Cyclic voltammetric (CV) measurements showed that unmodified GC and nano-MnOx\\/GC electrodes

Mohamed S. El-Deab

72

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

Microsoft Academic Search

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

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

1995-01-01

73

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

SciTech Connect

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 C and preferably from 250 to 350 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 liter/kg catalyst/h, and preferably from 100 to 1,000 liter/kg catalyst/h.

Gogate, M.R.; Spivey, J.J.; Zoeller, J.R.

1999-12-07

74

Highly efficient acid-treated cobalt catalyst for hydrogen generation from NaBH 4 hydrolysis  

Microsoft Academic Search

The effect of cobalt-based catalysts, i.e. CoCl2(20wt% Co)\\/Al2O3 treated by different acids, on NaBH4 hydrolysis was investigated. Five acids were used: oxalic acid, citric acid, acetic acid, sulfuric acid and hydrochloric acid. Two ways of acid treatment were considered: (i) ex-situ addition of acid to CoCl2(20wt% Co)\\/Al2O3 at room temperature and (ii) in-situ addition by mixing CoCl2, Al2O3 and acid

O. Akdim; U. B. Demirci; P. Miele

2009-01-01

75

Gas-phase decomposition of formic acid over Fe2O3 catalysts  

Microsoft Academic Search

Fe_2O_3 catalyst samples were used for the decomposition of formic acid, in the gas phase. These catalysts were produced by\\u000a calcination of Fe(NO_3)3 9H_2O for 5 h, in air, in the temperature range 200-600C. All catalysts were characterized by temperature-programmed\\u000a reduction (TPR) and X-ray diffraction (XRD). In addition, the surface area (SBET) of these samples as well as the acidity

S. A. Halawy; S. S. Al-Shihry; M. A. Mohamed

1997-01-01

76

Catalytic Ring Hydrogenation of Benzoic Acid with Supported Transition Metal Catalysts in scCO2  

PubMed Central

The ring hydrogenation of benzoic acid to cyclohexanecarboxylic acid over charcoal-supported transition metal catalysts in supercritical CO2 medium has been studied in the present work. The cyclohexanecarboxylic acid can be produced efficiently in supercritical CO2 at the low reaction temperature of 323 K. The presence of CO2 increases the reaction rate and several parameters have been discussed.

Wang, Hongjun; Zhao, Fengyu

2007-01-01

77

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

78

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

Microsoft Academic Search

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

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

2010-01-01

79

Study on the Condensation Reaction of preparing Vanillin from Guaiacol and Glyoxylic Acid by a novel Catalyst  

Microsoft Academic Search

As an intermediate for preparing vanillin derived from glyoxylic acid, 3-methoxy-4-hydroxymandelic acid (MHMA) was synthesized based on condensation of guaiacol with glyoxylic acid in the presence of a novel catalyst. The influence of the novel catalyst on the condensation reaction was investigated. The experimental results showed that the novel catalyst was suitable for the formation of 3-methoxy-4-hydroxymandelic acid from guaiacol

WEI Guo-feng; LIU Nai-qing

80

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

NASA Astrophysics Data System (ADS)

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

Faghihian, Hossein; Mohammadi, Mohammad Hadi

2013-01-01

81

Direct Alcohol Fuel Cells Using Solid Acid Electrolytes.  

National Technical Information Service (NTIS)

Direct alcohol fuel cells using solid acid electrolytes and internal reforming catalysts are disclosed. The fuel cell generally comprises an anode, a cathode, a solid acid electrolyte and an internal reforming catalyst. The internal reforming catalyst may...

S. M. Haile T. Uda

2005-01-01

82

Niobic acid — a new heterogeneous catalyst for processes in petrochemical and organic syntheses  

Microsoft Academic Search

Questions associated with the application of niobium compounds in catalysis are considered. Niobic acid Nb2O5.nH2O contains an appreciable amount of water, but its surface exhibits a high acidity — equivalent to the acidity of 70% sulfuric acid. This unusual solid acid manifests not only a high activity and sensitivity but also an appreciable stability as a catalyst in reactions in

F A Chernyshkova

1993-01-01

83

Niobic acid --- a new heterogeneous catalyst for processes in petrochemical and organic syntheses  

Microsoft Academic Search

Questions associated with the application of niobium compounds in catalysis are considered. Niobic acid Nb2O5.nH2O contains an appreciable amount of water, but its surface exhibits a high acidity --- equivalent to the acidity of 70% sulfuric acid. This unusual solid acid manifests not only a high activity and sensitivity but also an appreciable stability as a catalyst in reactions in

F. A. Chernyshkova

1993-01-01

84

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

2012-12-18

85

Chance and necessity in the selection of nucleic acid catalysts.  

PubMed

In Tom Stoppard's famous play [Rosencrantz and Guildenstern are Dead], the ill-fated heroes toss a coin 101 times. The first 100 times they do so the coin lands heads up. The chance of this happening is approximately 1 in 10(30), a sequence of events so rare that one might argue that it could only happen in such a delightful fiction. Similarly rare events, however, may underlie the origins of biological catalysis. What is the probability that an RNA, DNA, or protein molecule of a given random sequence will display a particular catalytic activity? The answer to this question determines whether a collection of such sequences, such as might result from prebiotic chemistry on the early earth, is extremely likely or unlikely to contain catalytically active molecules, and hence whether the origin of life itself is a virtually inevitable consequence of chemical laws or merely a bizarre fluke. The fact that a priori estimates of this probability, given by otherwise informed chemists and biologists, ranged from 10(-5) to 10(-50), inspired us to begin to address the question experimentally. As it turns out, the chance that a given random sequence RNA molecule will be able to catalyze an RNA polymerase-like phosphoryl transfer reaction is close to 1 in 10(13), rare enough, to be sure, but nevertheless in a range that is comfortably accessible by experiment. It is the purpose of this Account to describe the recent advances in combinatorial biochemistry that have made it possible for us to explore the abundance and diversity of catalysts existing in nucleic acid sequence space. PMID:11539421

Lorsch, J R; Szostak, J W

1996-02-01

86

One-step synthesis of a novel carbon-based strong acid catalyst through hydrothermal carbonization  

Microsoft Academic Search

\\u000a Abstract  A novel carbon-based strong acid catalyst was synthesized through the one-step hydrothermal carbonization of furaldehyde and\\u000a p-toluenesulfonic acid (PTSA) in aqueous solution at 180 °C for only 4 h. The novel carbon-based solid acid possessed high\\u000a acidity, and the catalytic activities were investigated by esterification and oxathioketalization. The results showed that\\u000a the novel catalyst demonstrated much greater activity than the traditional solid

Huiquan Xiao; Yingxue Guo; Xuezheng Liang; Chenze Qi

2010-01-01

87

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

2012-06-12

88

40 CFR 76.3 - General Acid Rain Program provisions.  

Code of Federal Regulations, 2010 CFR

... 2009-07-01 false General Acid Rain Program provisions. 76.3 Section... AIR PROGRAMS (CONTINUED) ACID RAIN NITROGEN OXIDES EMISSION REDUCTION PROGRAM § 76.3 General Acid Rain Program provisions. The...

2009-07-01

89

40 CFR 76.3 - General Acid Rain Program provisions.  

Code of Federal Regulations, 2010 CFR

... 2010-07-01 false General Acid Rain Program provisions. 76.3 Section... AIR PROGRAMS (CONTINUED) ACID RAIN NITROGEN OXIDES EMISSION REDUCTION PROGRAM § 76.3 General Acid Rain Program provisions. The...

2010-07-01

90

40 CFR 76.3 - General Acid Rain Program provisions.  

Code of Federal Regulations, 2013 CFR

... 2013-07-01 false General Acid Rain Program provisions. 76.3 Section... AIR PROGRAMS (CONTINUED) ACID RAIN NITROGEN OXIDES EMISSION REDUCTION PROGRAM § 76.3 General Acid Rain Program provisions. The...

2013-07-01

91

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

92

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

93

[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

94

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

SciTech Connect

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

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

2007-03-01

95

Carbon supported catalysts for oxygen reduction in acidic media prepared by thermolysis of Ru 3(CO) 12  

Microsoft Academic Search

Carbon supported catalysts for oxygen reduction in acidic media based on ruthenium and selenium have been prepared by thermolysis of Ru3(CO)12 in organic solvents. The mass specific activity of these catalysts is higher than that of the unsupported samples. The optimum loading of the supporting carbon with catalyst has been found to be about 10%; higher loadings lead to only

M Bron; P Bogdanoff; S Fiechter; M Hilgendorff; J Radnik; I Dorbandt; H Schulenburg; H Tributsch

2001-01-01

96

Evaluation of platinum-based catalysts for methanol electro-oxidation in phosphoric acid electrolyte  

Microsoft Academic Search

Carbon-supported catalysts of Pt, Pt\\/Ru, Pt\\/Ru\\/W, and Pt\\/Ru\\/Pd were evaluated for the electro-oxidation of methanol in phosphoric acid at 180 C. These catalysts were characterized using cyclic voltammetry and x-ray diffraction. Addition of Ru to a 0.5 mg\\/cm² Pt catalyst (1:1 atomic ratio) caused a large reduction in polarization. The open-circuit voltage was reduced by 100 mV and polarization at

Chunzhi He; H. R. Kunz; J. M. Fenton

1997-01-01

97

Manganese-Based Catalysts for the Catalytic Remediation of Phenolic Acids by Ozone  

Microsoft Academic Search

Manganese-based catalysts supported on Al2O3, TiO2, ZrO2 and CeO2 were tested for the catalytic ozonation of a simulated wastewater involving phenolic acids. Comparing the Mn-Ce catalysts preparation method, wetness impregnation and co-precipitation, the last one showed to be more active. Moreover, the increase of Mn\\/Ce molar proportion from 22\\/78 to 70\\/30 increased the ozonation efficiency. The catalysts stability in terms

Rui C. Martins; Rosa M. Quinta-Ferreira

2009-01-01

98

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

99

Lanthanide(III) complexes of aromatic sulfonic acids as catalysts for the nitration of toluene  

Microsoft Academic Search

Ytterbium(III) complexes of benzenesulfonic acid, Yb(BSA)3, p-toluenesulfonic acid, Yb(Tos)3, and 2-naphthalenesulfonic acid, Yb(NSA)3, were prepared and tested as possible catalyst for the nitration of toluene. With a loading of 5–10mol% of Yb(BSA)3 and Yb(NSA)3, a quantitative conversion of toluene to nitrotoluene was achieved within 5h, while Yb(Tos)3 was slightly less active and 77% of nitrated products were obtained. The catalysts

Tatjana N. Parac-Vogt; Karen Deleersnyder; Koen Binnemans

2004-01-01

100

Study of kinetic laws of dehydration of dimethylvinylcarbinol of phosphoric acid catalyst  

SciTech Connect

The dehydration of dimethylvinylcarbinol (DMVC) to isoprene on phosphoric acid catalyst at 60-90/sup 0/C and in the concentrations range of 40-60 wt. % of the acid was studied by the microreactioning gas-chromatographic method. The overall consumption constants of DMVC with time were determined, as well as consumption constants of DMVC k/sub 1q/, taking into account the absorption of the reagent on the catalysts. It was shown that the dehydration reaction is irreversible, is first order with respect to DMVC, and the equation log k/sub 1q/ + H/sub 0/ = const, where H/sub 0/ is the acidity function holds.

Malinskii, V.S.; Vinnik, M.I.

1987-04-01

101

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

Microsoft Academic Search

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

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

2004-01-01

102

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

103

The role of acid sites in cobalt zeolite catalysts for selective catalytic reduction of NO x  

Microsoft Academic Search

The role of the acidic support in ion-exchanged cobalt-zeolite, lean NOx catalysts has been determined by studying the individual steps in the selective reduction pathway. At a GHSV of 10,000 and\\u000a reaction temperatures below 400C, NO oxidation is not sufficiently rapid to obtain equilibrium over, for example, 1–4 wt%\\u000a Co-mordenite catalysts. The NO oxidation rate increases in the order H+Co2+

J. T. Miller; E. Glusker; R. Peddi; T. Zheng; J. R. Regalbuto

1998-01-01

104

Epa’s Catalyst Research Program: Environmental Impact of Sulfuric Acid Emissions  

Microsoft Academic Search

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 H2SO4, averaging 2.7 mg\\/mile for 49-state cars and 15 mg\\/mile for California cars. Research on measurement methodology for H2SO4 and other sulfate

Robert E. Lee Jr; F. Vandiver Duffield

1977-01-01

105

Novel Acidic Ionic Liquids as Efficient and Recyclable Catalysts for the Cyclotrimerization of Aldehydes  

Microsoft Academic Search

A mild, efficient, and eco-friendly procedure for cyclotrimerization of aldehydes was realized by using a series of novel Brönsted acidic ionic liquids (BAILs) consisting double –SO3H groups in cations as catalysts. High conversion of aldehydes and selectivity of trialkyl-1,3,5- trioxanes were achieved by using 1 mol% of BAILs. In addition, the catalyst system could be recycled and reused for at least

Heyuan Song; Jing Chen; Chungu Xia; Zhen Li

2011-01-01

106

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

Microsoft Academic Search

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

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

2009-01-01

107

MoVO-based catalysts for the oxidation of ethane to ethylene and acetic acid  

Microsoft Academic Search

The influence of niobium and\\/or palladium in MoV0.4Ox on both solid state chemistry and catalytic properties in the oxidation of ethane to acetic acid and ethylene is examined. Catalysts without molybdenum (VNb0.31Pd3e-4Ox) are also studied for comparison. The structural properties of the precursors and of the catalysts obtained by calcination of precursors at 350 and 400°C are studied by X-ray

Martial Roussel; Michel Bouchard; Khalid Karim; Saleh Al-Sayari; Elisabeth Bordes-Richard

2006-01-01

108

Synthesis of biodiesel from cottonseed oil and methanol using a carbon-based solid acid catalyst  

Microsoft Academic Search

A carbon-based solid acid catalyst was prepared by the sulfonation of carbonized vegetable oil asphalt and used to catalyze the transesterification of methanol with cottonseed oil. This catalyst was characterized by scanning electron microscopy\\/energy dispersive spectroscopy, BET surface area and pore size measurement, thermogravimetry analysis and Fourier transform infrared spectroscopy. The sulfonated multi-walled carbon nanotubes (s-MWCNTs) was also prepared and

Qing Shu; Qiang Zhang; Guanghui Xu; Zeeshan Nawaz; Dezheng Wang; Jinfu Wang

2009-01-01

109

Electrooxidation of formic acid on carbon supported Pt-Os catalyst  

Microsoft Academic Search

Pt-Os (3:1)\\/C catalyst was prepared through the route of thermal decomposition of metallic carbonyl cluster. TEM image showed Pt-Os nanoparticles were well dispersed on carbon substrate with an average particle size of 2.2±0.9nm. XRD pattern indicated Pt-Os has a face-centered cubic crystal structure. Characterized by cyclic voltammetry and chronoamperometry, Pt-Os (3:1)\\/C catalyst shows a superior electro-catalytic activity to formic acid

Wei Liu; Junjie Huang

2009-01-01

110

Supercritical n-butane isomerization on solid acid catalysts  

Microsoft Academic Search

n-Butane isomerization was investigated at the supercritical state in a flow type reactor. Sulfated zirconia (SZ), heteropolyacids (HPA) of the Keggin type H3PW12O40 (HPWO), H4SiW12O40 (HSiWO) supported on titania, H-mordenite (HM) were studied as catalysts at 488, 533 and 573K and 6.1, 11.0 and 13.8MPa, respectively. Gas-phase isomerization was carried out on the same catalysts for comparison. Rapid deactivation of

V. I Bogdan; T. A Klimenko; L. M Kustov; V. B Kazansky

2004-01-01

111

Sulfated Zirconia-Based Strong Solid-Acid Catalysts: Recent Progress  

Microsoft Academic Search

This review article deals with recent progress in the preparation of sulfated zirconia (SZ)-bassed, strong solid-acid catalysts, the characterization of their physicochemical properties and the evaluation of their catalytic performance in various promising applications. Strong emphasis was put on discussion of controversial issues such as the strength of acid sites, the nature of active sites, the reaction mechanism, and the

XUEMIN SONG; ABDELHAMID SAYARI

1996-01-01

112

Sulfonic acid functionalised ordered mesoporous materials as catalysts for fine chemical synthesis.  

PubMed

The synthesis of highly active acid catalysts supported on ordered mesoporous materials has eluded chemists until 1998, when Wim M. Van Rhijn et al. explored three different routes to tether sulfonic acid on mesoporous silica. This viewpoint sheds light on this landmark and explores its significant impact on material science and green catalysis. PMID:23990025

El Kadib, Abdelkrim; Finiels, Annie; Brunel, Daniel

2013-08-30

113

Sandstone acidizing design with a generalized model  

SciTech Connect

Acidizing of sandstones with HF/HCl mixtures is most frequently applied to remove near-wellbore damage, often in reservoirs with considerable vertical heterogeneity. A previously presented model for such processes in which an organic resin diverting agent was used has been extended to account for any type of particulate diverting agent and to allow for injection of multiple sequences of acid and diverting agent at either constant rates or constant bottomhole pressures (BHP's). When used to design treatments for a typical U.S. gulf coast reservoir, the model has shown that the optimal treatment strategy depends on both diverting-agent efficiency and the desired depth of live acid penetration and that relatively high injection rates appear advantageous for the conditions imposed by the model. A general model of diverting-agent behavior was developed from filtration theory. A single parameter, the specific cake resistance, is needed to model the diverting-agent behavior in the acidizing simulator. Calculation procedures to determine this parameter from laboratory tests of diverting agents were developed. These tests are either constant-rate, constant-pressure, or variable-rate and variable-pressure experiments; in each case, the specific cake resistance can be extracted from the experimental data. These procedures allow the efficiencies of various diverting agents to be compared on an equal basis. The sandstone acidizing model was used to design a treatment for a typical gulf coast sandstone reservoir. On the basis of an overall skin factor for the well, various assumptions were made about the distribution of formation damage around this multilayered completion. Treatment results were found to be fairly sensitive to the details of the damage distribution, suggesting that the skin factor alone may not be an adequate design parameter.

Taha, R.; Hill, A.D.; Sepehrnoori, K.

1989-02-01

114

PdBi\\/C and PtPb\\/C Bimetallic Catalysts for Direct Formic Acid Fuel Cells  

Microsoft Academic Search

An efficient methodology for comparing anode catalysts for direct formic acid fuel cells (DFAFCs) by employing a multi-anode, liquid-fed fuel cell is presented. PdBi\\/C bimetallic catalysts synthesized by co-depositing Pd and Bi on Vulcan XC-72 carbon black, as well as PtPb\\/C bimetallic catalysts synthesized by depositing Pb on a Pt\\/C catalyst, were systematically studied in a multi-anode DFAFC. The PdBi\\/C

Xingwen Yu; Peter G. Pickup

2009-01-01

115

Thermal stability of the active component of sulfuric acid catalysts  

Microsoft Academic Search

The authors study the melting point and thermal stability of the ternary system KâSOâ-KâSâOâ-VâOâ. The study was made by a thermogravimetric method. It is seen that higher potassium sulfate contents in the active component suppress the effects associated with the decomposition of the active component, and enhances the thermal stability of the catalyst.

V. M. Borisov; Yu. V. Azhikina; R. M. Stul

1987-01-01

116

Preparation of solid acid catalyst from glucose-starch mixture for biodiesel production.  

PubMed

The aim of this work is to study the catalyst prepared by glucose-starch mixture. Assessment experiments showed that solid acid behaved the highest esterification activity when glucose and corn powder were mixed at ratio of 1:1, carbonized at 400°C for 75 min and sulfonated with concentrated H(2)SO(4) (98%) at 150°C for 5 h. The catalyst was characterized by acid activity measurement, XPS, TEM and FT-IR. The results indicated that solid acid composed of CS(0.073)O(0.541) has both Lewis acid sites and Bronsted acid sites caused by SO(3)H and COOH. The conversions of oleic acid esterification and triolein transesterification are 96% and 60%, respectively. Catalyst for biodiesel production from waste cottonseed oil containing high free fatty acid (FFA 55.2 wt.%) afforded the methyl ester yield of about 90% after 12h. The catalyst deactivated gradually after recycles usage, but it could be regenerated by H(2)SO(4) treatment. PMID:21067915

Chen, Guo; Fang, Baishan

2010-10-25

117

Liquefaction of sawdust in 1-octanol using acidic ionic liquids as catalyst.  

PubMed

Acidic ionic liquids (AILs) as a novel catalyst in biomass liquefaction can accord with the demand of green chemistry and enhance the development of biomass thermal chemical conversion. A series of AILs containing HSO4- were synthesized by the imidazolium cation functionalization and applied to the Chinese fir sawdust liquefaction in 1-octanol in this paper. The experimental results showed that the liquefaction rate was gradually improved with the AILs acidity increasing, and reached 71.5% when 1-(4-sulfobutyl)-3-methylmidazolium hydrosulfate was used as catalyst with the 6:1 mass ratio of 1-octanol to sawdust at 423K after 60 min. Lignin, hemicellulose and cellulose were orderly desquamated, and then depolymerized and liquefied with the catalyst acidity increasing in the sawdust liquefaction process. The light oil was mainly composed of the octyl ether and the octyl ester compounds, suggesting that the solvent may play an important role in producing the high octane rating biofuel. PMID:23770997

Lu, Zexiang; Zheng, Huaiyu; Fan, Liwei; Liao, Yiqiang; Ding, Bingjing; Huang, Biao

2013-05-29

118

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

119

Reductive desorption of sulfuric acid formed on the carbon catalyst in flue gas desulfurization (FGD)  

Microsoft Academic Search

Reductive desorption of sulfuric acid formed on the carbon catalyst in flue gas desulfurization (FGD) by heating with hydrogen at 3: 200°C converted the acid to gas-phase sulfur dioxide with a significant loss of the acid to hydrogen sulfide and elemental sulfur. These side reactions were suppressed and the temperature required for SOâ recovery was reduced by impregnating the charcoal

S. Yoshizawa; A. Karagiri; K. Watanabe

1979-01-01

120

Vapour phase hydrogenation of olefins by formic acid over a Pd\\/C catalyst  

Microsoft Academic Search

It has been found that ethylene and propylene could be effectively hydrogenated by formic acid vapour over a Pd\\/carbon catalyst at low temperatures (<440K). Surface hydrogen formation from formic acid is the rate-determining step for this hydrogenation reaction. Interaction of this hydrogen with the olefins is then fast. The conversion of formic acid in the presence of either of the

Dmitri A. Bulushev; Julian R. H. Ross

2011-01-01

121

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

122

Ammonolysis of esters of hydroxybenzoic acids on a boron phosphate catalyst  

SciTech Connect

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

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

1987-09-10

123

Synthesis of substituted butenolides by the ring closing metathesis of two electron deficient olefins: a general route to the natural products of paraconic acids class  

Microsoft Academic Search

A variety of allyl acrylates possessing electron-withdrawing groups undergo RCM using the second generation Grubbs’ catalyst in the presence of a Lewis acid resulting in diverse butenolides in high isolated yields. This methodology provides a general route to the natural products of paraconic acids class, exemplified by a total synthesis of (±)-phaseolinic acid.

N. Selvakumar; P. Kalyan Kumar; K. Chandra Shekar Reddy; B. Chandra Chary

2007-01-01

124

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

Microsoft Academic Search

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

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

2008-01-01

125

Production of CO-Free H 2 by Formic Acid Decomposition over Mo 2 C\\/Carbon Catalysts  

Microsoft Academic Search

\\u000a Abstract  The vapor phase decomposition of formic acid was studied over supported Mo2C catalysts in a flow system. Mo2C deposited on silica is an effective catalyst for both the dehydrogenation of formic acid to yield H2 and CO2, and its dehydration to yield H2O and CO. The extent of the decomposition approached 100% at 623 K. Preparation of the Mo2C catalyst by

Ákos Koós; Frigyes Solymosi

2010-01-01

126

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

SciTech Connect

As a catalyst precursor, platinum sulfite acid (PSA) is easy to use and not relatively expensive, and is a potentially attractive precursor for many types of supported catalysts. The ultimate usefulness for many catalyst applications will depend on the extent that Pt can be dispersed and sulfur eliminated. To our knowledge, there exists no detailed characterization in the catalysis literature of PSA and the nanoparticulate Pt phases derived from it during catalyst pretreatment. To this end a series of supports including alumina, silica, magnesia, niobia, titania, magnesia and carbon were contacted with PSA solutions and subsequently analyzed with extended x-ray absorption fine structure (EXAFS) and x-ray absorption near edge structure (XANES) analysis, and x-ray photoelectron spectroscopy (XPS) to characterize the Pt species formed upon impregnation, calcination, and reduction. While all catalysts show retention of some S, reasonably small particle sizes with relatively little Pt-S can in some instances be produced using PSA. The amount of retained sulfur appears to decrease with decreasing surface acidity, although even the most acidic supports (niobia and silica) display some storage of S even while only Pt-O bands are observed after calcination or reoxidation. More sulfur was eliminated by high temperature calcinations followed by reduction in hydrogen, at the expense of increasing Pt particle size.

Regalbuto, J.R.; Ansel, O.; Miller, J.T. (BP Res. Cntr.); (UIC)

2010-11-12

127

Performance improvement in direct formic acid fuel cells (DFAFCs) using metal catalyst prepared by dual mode spraying  

Microsoft Academic Search

In the present study, we investigate performance of direct formic acid fuel cells (DFAFCs) consisting of membrane electrode assembly (MEA) prepared by three different catalyst coating methods – direct painting, air spraying and dual mode spraying. For the DFAFC single cell tests, palladium (Pd) and platinum (Pt) are used as anode and cathode catalyst, respectively, and four different formic acid

S. M. Baik; Jinsoo Kim; Jonghee Han; Yongchai Kwon

2011-01-01

128

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

SciTech Connect

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

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

1996-01-01

129

Conversion of furfuryl alcohol into ethyl levulinate using solid acid catalysts.  

PubMed

Furfural, a potential coproduct of levulinic acid, can be converted into levulinic acid via hydrogenation to furfuryl alcohol and subsequent ethanolysis to ethyl levulinate. The ethanolysis reaction is known to proceed in the presence of H(2)SO(4). We show here that several strongly acidic resins are comparably effective catalysts for this reaction. Optimal performance is achieved by balancing the number of acid sites with their accessibility in the resin. Acidic zeolites such as H-ZSM-5 also catalyze this reaction, although with a lower activity and a higher co-production of diethyl ether. PMID:19370740

Lange, Jean-Paul; van de Graaf, Wouter D; Haan, René J

2009-01-01

130

Efficiencies of acid catalysts in the hydrolysis of lignocellulosic ...  

Treesearch

Among sulfuric, oxalic and maleic acid treatments, the amount of xylose released as ... In subsequent fermentations with pretreated biomass, the ethanol ... decay fungi, corn as fuel, biomass fuel, bioconversion, biorefining, alcohol, xylose, acid  ...

131

Conversion of biomass into 5-hydroxymethylfurfural using solid acid catalyst  

Microsoft Academic Search

5-Hydroxymethylfurfural (HMF) was produced from monosaccharide (fructose and glucose), polysaccharide (inulin) and the Jerusalem artichoke juice by a simple one-pot reaction including hydrolysis and dehydration using solid acid under mild condition. Hydrated niobium pentoxide (Nb2O5·nH2O2NA, niobic acid; NA-p, Niobic acid treated with 1M phosphoric acid and calcinated at 573 K.2) after pretreatment showed high catalytic activities for dehydration of mono-

Fengli Yang; Qishun Liu; Xuefang Bai; Yuguang Du

2011-01-01

132

Optimising catalytic properties of supported sulfonic acid catalysts  

Microsoft Academic Search

Siliceous mesoporous molecular sieves (SBA-15) have been functionalised with propylsulfonic acid groups by both co-condensing 3-mercaptopropyltrimethoxysilane with the solid at the synthesis (sol–gel) stage and by grafting the same compound to pre-prepared SBA-15, followed, in both cases, by oxidation to sulfonic acid. The acidic and catalytic properties of the supported sulfonic acids prepared in the two ways have been compared,

P. F. Siril; N. R. Shiju; D. R. Brown; K. Wilson

2009-01-01

133

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

Microsoft Academic Search

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

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

2005-01-01

134

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

135

Active specie on vanadium-containing catalysts for the selective oxidation of ethane to acetic acid  

Microsoft Academic Search

Catalytic experiments on pure VPO phases and titania supported VPOx and VOx are presented for the selective oxidation of ethane to acetic acid. The effects of temperature, pressure, contact time and feed conditions are examined. The characterization of catalysts by several methods shows that different specie are present on titania according to the loading V\\/Ti. The correlation with catalytic results

L. Tessier; E. Bordes; M. Gubelmann-Bonneau

1995-01-01

136

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

137

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

138

Effects of deactivation and regeneration on the acidic function of commercial hydrocracking catalysts  

SciTech Connect

To determine the effects of deactivation and regeneration of the acidic function of a zeolite-containing hydrocracking catalyst, a series of fresh, commercially-deactivated, and regenerated catalysts were characterized using cumene transalkylation. Differential rate data obtained in a fixed-bed microreactor at a hydrogen or helium partial pressure of about 8.3 atm and temperatures ranging from 428 to 512/sup 0/K were extrapolated to zero time-on-stream to offset effects of catalyst deactivation during the experiments. These were classified into two categories such that the effects of unit cell size and wt% carbon on the cumene disproportionation activity could be assessed independently. As the unit cell size decreased, the adsorption equilibrium coefficient of the catalysts did not change, but the forward rate constant increased, went through a maximum, and decreased. The deactivation parameter on the other hand increased when the unit cell size decreased. At a constant unit cell size, the adsorption equilibrium coefficient of the regenerated catalysts did not change with wt% carbon, however, a linear relationship between the forward rate constant and wt% carbon was observed. This was attributed to the regeneration of the deactivated catalysts at highly diffusion-controlled conditions. At a constant unit cell size, the deactivated catalysts with high levels of coke (> 2 wt%) had similar activities. This was partially due to a reversible poison present on the surface of these deactivated catalysts. The decrease in the unit cell size during the deactivation and regeneration process was attributed to zeolite attack by water. In the regeneration process the water is formed as a byproduct of the coke oxidation reaction and, depending on the geometry of the bed, it can attack the zeolite framework.

Absil, R.P.L.

1984-01-01

139

A general kinetic approach to investigation of active-site availability in macromolecular catalysts.  

PubMed

A potentially general kinetic method for the investigation of active-site availability in preparations of macromolecular catalysts was developed. Three kinetic models were considered: (a) the conventional two-step model of enzyme catalysis, where the preparation contains only active catalyst (E(a)) and inert (i.e. non-binding, non-catalytic) material (E(i)); (b) an extension of the conventional model (a) involving only E(a) and E(i), but with non-productive binding to E(a) (in addition to productive binding); (c) a model in which the preparation contains also binding but non-catalytic material (E(b)), predicted to be present in polyclonal catalytic antibody preparations. The method involves comparing the parameters V(max) and K(m) obtained under catalytic conditions where substrate concentrations greatly exceed catalyst concentration with those (klim/obs, the limiting value of the first-order rate constant, k(obs), at saturating concentrations of catalyst; and Kapp/m) for single-turnover kinetics, in which the reverse situation obtains. The active-site contents of systems that adhere to model (a) or extensions that also lack E(b), such as the non-productive binding model (b), may be calculated using [E(a)](T)=V(max)/klim/obs. This was validated by showing that, for alpha-chymotrypsin, identical values of [E(a)](T) were obtained by the kinetic method using Suc-Ala-Ala-Pro-Phe-4-nitroanilide as substrate and the well-known 'all-or-none' spectroscopic assay using N-trans-cinnamoylimidazole as titrant. For systems that contain E(b), such as polyclonal catalytic antibody preparations, V(max)/klim/obs is more complex, but provides an upper limit to [E(a)](T). Use of the kinetic method to investigate PCA 271-22, a polyclonal catalytic antibody preparation obtained from the antiserum of sheep 271 in week 22 of the immunization protocol, established that [E(a)](T) is less than approx. 8% of [IgG], and probably less than approx. 1% of [IgG]. PMID:10657247

Resmini, M; Gul, S; Carter, S; Sonkaria, S; Topham, C M; Gallacher, G; Brocklehurst, K

2000-02-15

140

A general kinetic approach to investigation of active-site availability in macromolecular catalysts.  

PubMed Central

A potentially general kinetic method for the investigation of active-site availability in preparations of macromolecular catalysts was developed. Three kinetic models were considered: (a) the conventional two-step model of enzyme catalysis, where the preparation contains only active catalyst (E(a)) and inert (i.e. non-binding, non-catalytic) material (E(i)); (b) an extension of the conventional model (a) involving only E(a) and E(i), but with non-productive binding to E(a) (in addition to productive binding); (c) a model in which the preparation contains also binding but non-catalytic material (E(b)), predicted to be present in polyclonal catalytic antibody preparations. The method involves comparing the parameters V(max) and K(m) obtained under catalytic conditions where substrate concentrations greatly exceed catalyst concentration with those (klim/obs, the limiting value of the first-order rate constant, k(obs), at saturating concentrations of catalyst; and Kapp/m) for single-turnover kinetics, in which the reverse situation obtains. The active-site contents of systems that adhere to model (a) or extensions that also lack E(b), such as the non-productive binding model (b), may be calculated using [E(a)](T)=V(max)/klim/obs. This was validated by showing that, for alpha-chymotrypsin, identical values of [E(a)](T) were obtained by the kinetic method using Suc-Ala-Ala-Pro-Phe-4-nitroanilide as substrate and the well-known 'all-or-none' spectroscopic assay using N-trans-cinnamoylimidazole as titrant. For systems that contain E(b), such as polyclonal catalytic antibody preparations, V(max)/klim/obs is more complex, but provides an upper limit to [E(a)](T). Use of the kinetic method to investigate PCA 271-22, a polyclonal catalytic antibody preparation obtained from the antiserum of sheep 271 in week 22 of the immunization protocol, established that [E(a)](T) is less than approx. 8% of [IgG], and probably less than approx. 1% of [IgG].

Resmini, M; Gul, S; Carter, S; Sonkaria, S; Topham, C M; Gallacher, G; Brocklehurst, K

2000-01-01

141

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

Microsoft Academic Search

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

Varsha Brahmkhatri; Anjali Patel

2012-01-01

142

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

Microsoft Academic Search

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

Varsha Brahmkhatri; Anjali Patel

2011-01-01

143

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

Microsoft Academic Search

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

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

2007-01-01

144

Recyclable Lewis acid catalysts by tuning supercritical vs liquid carbon dioxide phases: lanthanide catalysts with tris(perfluorooctanesulfonyl)methide and bis(perfluorooctanesulfonyl)amide  

Microsoft Academic Search

Lanthanide tris(perfluorooctanesulfonyl)methide and bis(perfluorooctanesulfonyl)amide catalysts are shown to be continuously employed in supercritical carbon dioxide by changing supercritical vs. liquid carbon dioxide phases. The lanthanide complexes are thus extremely efficient Lewis acid catalysts even in supercritical carbon dioxide phase by virtue of the highly electron-withdrawing and solubilizing effect of tris(perfluorooctanesulfonyl)methide and bis(perfluorooctanesulfonyl)amide without any hydrocarbon spacer.

Joji Nishikido; Mayumi Kamishima; Hiroshi Matsuzawa; Koichi Mikami

2002-01-01

145

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

PubMed

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

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

2012-04-03

146

Study of kinetic laws of dehydration of dimethylvinylcarbinol of phosphoric acid catalyst  

Microsoft Academic Search

The dehydration of dimethylvinylcarbinol (DMVC) to isoprene on phosphoric acid catalyst at 60-90°C and in the concentrations range of 40-60 wt. % of the acid was studied by the microreactioning gas-chromatographic method. The overall consumption constants of DMVC with time were determined, as well as consumption constants of DMVC k\\/sub 1q\\/, taking into account the absorption of the reagent on

V. S. Malinskii; M. I. Vinnik

1987-01-01

147

Efficient and stable solid acid catalysts synthesized from sulfonation of swelling mesoporous polydivinylbenzenes  

Microsoft Academic Search

Efficient and stable solid acid catalysts, sulfonic groups functional swelling mesoporous polydivinylbenzenes (PDVB-x-SO3Hs), were synthesized from sulfonation of swelling mesoporous polydivinylbenzenes (PDVB-xs) by chlorosulfonic acid in CH2Cl2. Nitrogen adsorption–desorption isotherms showed that PDVB-x-SO3Hs have high surface area and abundant mesoporosity. Elemental analysis and acid–base titration techniques showed that PDVB-x-SO3Hs have high concentration of sulfonic groups. Esterifications of acetic acid with

Fujian Liu; Xiangju Meng; Yonglai Zhang; Limin Ren; Faisal Nawaz; Feng-Shou Xiao

2010-01-01

148

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

NASA Astrophysics Data System (ADS)

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

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

2010-11-01

149

Acid sites in sulfated and metal-promoted zirconium dioxide catalysts  

SciTech Connect

Unpromoted sulfated zirconia (SZ) and sulfated zirconia that was promoted with iron and manganese ions (FMSZ) have been tested as catalysts for the isomerization of n-butane to isobutane. FMSZ is the superior catalyst; its activity at 60{degrees}C is similar to that of SZ at 180{degrees}C. Both catalysts deactivate rapidly. FTIR analysis of adsorbed CO and acetonitrile reveals the presence of Lewis and Broensted sites in both catalysts. Acetonitrile is strongly adsorbed on FMSZ. Subsequent desorption is destructive; CO{sub 2}, SO{sub 2}, and O{sub 2} are formed, while temperature-programmed oxidation shows that no carbon-containing products are left on the surface. CO-FTIR reveals equal acidity, within experimental error, for the Lewis sites on SZ and FMSZ. Changes in proton NMR and FTIR parameters caused by adsorption of acetonitrile show that the acid strength of the Broensted sites of SZ and FMSZ is similar to that of the lower OH-frequency protons in HY, but weaker than that of the protons in HZSM-5. The results indicate that the remarkable activity of SZ and FMSZ is not caused by exceptionally strong acid sites, but by stabilization of the transition state complex at the surface. 34 refs., 8 figs., 2 tabs.

Adeeva, V.; Lei, G.D.; Schuenemann, V. [Northwestern Univ., Evanston, IL (United States)] [and others

1995-02-01

150

40 CFR 75.3 - General Acid Rain Program provisions.  

Code of Federal Regulations, 2013 CFR

...17 2013-07-01 2013-07-01 false General Acid Rain Program provisions. 75.3 Section 75.3 Protection...CONTINUOUS EMISSION MONITORING General § 75.3 General Acid Rain Program provisions. The provisions of part 72,...

2013-07-01

151

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

Microsoft Academic Search

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

Kasirajan Ramachandran; Pandian Sivakumar; Tamilarasan Suganya; Sahadevan Renganathan

2011-01-01

152

Vapor-phase nitration of benzene over solid acid catalysts (1): Nitration with nitric oxide (NO 2)  

Microsoft Academic Search

Vapor-phase nitration of benzene over acidic catalysts is expected to be a clean process with no sulfuric acid waste. We investigated this process over acidic catalysts utilizing nitric oxide (NO2) as a nitrating agent, and found that several mixed metal oxides, such as silica–alumina, zinc-oxide–titania, and tungsten-oxides–molybdenum-oxide, exhibited a fairly good activity. Among them, WO3–MoO3 is the most active, but

H. Sato; K. Hirose

1998-01-01

153

MCM-48 as a support for sulfonic acid catalysts  

Microsoft Academic Search

The ordered mesoporous silica, MCM-48, has been functionalised with sulfonic acid. Its physico-chemical properties have been compared with those of sulfonated MCM-41 and SBA-15. A higher catalytic activity for the functionalised MCM-48 in the alkylation of toluene with benzyl alcohol suggests that MCM-48 behaves as a better sulfonic acid support than MCM-41 and SBA-15. Ammonia adsorption calorimetric data shows that

M. Bandyopadhyay; N. R. Shiju; D. R. Brown

2010-01-01

154

Catalytic pyrolysis of cellulose in sulfolane with some acidic catalysts  

Microsoft Academic Search

Catalytic pyrolysis of cellulose in sulfolane (tetramethylene sulfone) with sulfuric acid or polyphosphoric acid gave levoglucosenone,\\u000a furfural, and 5-hydroxymethyl furfural (5-HMF) up to 42.2%, 26.9%, and 8.8% (as mol% yield based on the glucose unit), respectively.\\u000a Pyrolysis behaviors of the intermediates indicated the conversion pathways, and the conversion: levoglucosenone ? furfural\\u000a was found to require water. The control of the

Haruo Kawamoto; Shinya Saito; Wataru Hatanaka; Shiro Saka

2007-01-01

155

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

156

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

PubMed

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

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

2008-05-27

157

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

PubMed

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

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

2010-03-09

158

Thickness effects of a carbon-supported platinum catalyst layer on the electrochemical reduction of oxygen in sulfuric acid solution  

Microsoft Academic Search

The influence of the thickness of a carbon-supported platinum catalyst layer on the oxygen reduction reaction (orr) has been studied in sulfuric acid solution by means of a thin-film rotating disk electrode. Pronounced changes in the Pt utilization, electrode activity and the orr kinetics have been observed upon varying the catalyst layer thickness. The thicker film electrode exhibits a higher

Junhua Jiang; Baolian Yi

2005-01-01

159

Catalytic decomposition of formic acid on oxide catalysts—an impulse-oscillation model approach to the unimolecular mechanism  

Microsoft Academic Search

An impulse-oscillation model (IOM) was used for a time description of catalytic acts in the reactions of catalytic decomposition of formic acid on oxide catalysts. The results of computation using the model show that for the dehydrogenation reaction the most important modes are the OCO bending in bidentate adsorbed formate ion and OH stretching on the catalyst surface while for

Marek A Borowiak; Micha? H Jamróz; Ragnar Larsson

1999-01-01

160

Organometallic Catalysts for Primary Phosphoric Acid Fuel Cells.  

National Technical Information Service (NTIS)

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...

F. Walsh

1987-01-01

161

Effect of acidic and alkaline impurities on the activity of a low-temperature carbon monoxide conversion catalyst  

SciTech Connect

The results of a study of the dependence of the activity of low-temperature catalysts on the simultaneous presence of impurities of acidic and alkaline character are presented. The results of the study showed that poisioning of copper-containing catalysts by chlorine or sulfate ions cannot be prevented by adding alkali metal ions to the catalyst. However, with an increase in the concentration of the alkaline additives, the activity of the catalyst increases significantly at a temperature above 150/sup 0/C.

Sukhoruchkina, L.A.; Semenova, T.A.

1984-02-01

162

Cellulose Sulfuric Acid: Novel and Efficient Biodegradable and Recyclable Acid Catalyst for the Solid-State Synthesis of Thiadiazolo Benzimidazoles  

Microsoft Academic Search

An efficient method for the synthesis of 2-substituted benzimidazoles has been developed. In this method, benzo[c][1,2,5]thiadiazole-4,5-diamine was condensed with different aldehydes in the presence of cellulose sulfuric acid under solvent-free conditions by simple physical grinding of reactants using a mortar and pestle at room temperature. The methodology is mild, high-yielding, and green, and the catalyst could be easily recycled.

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

2011-01-01

163

Reduction of Np(V) with formic acid in acidic solutions in the presence of palladium catalysts  

Microsoft Academic Search

The kinetics of catalytic reduction of Np(V) with formic acid in HClO4 solutions in the presence of Pd\\/SiO2 catalysts differing in the Pd content and size of Pd nanocrystals was studied. The reaction is a structure-insenitive catalytic\\u000a process, i.e., the size effect is absent. An increase in the percentage of Pd on SiO2 leads to a decrease in the activity

M. Yu. Boltoeva; V. P. Shilov; A. V. Anan’ev

2008-01-01

164

Mesoporous silica containing sulfonic acid groups as catalysts for the alpha-pinene methoxylation  

Microsoft Academic Search

The methoxylation of a-pinene was studied over sulfonic acid-functionalized mesoporous silica (MCM-41, PMO) at 60°C. The support functionalization was achieved by the introduction of 3-(mercaptopropyl)trimethoxysilane onto the surface of these materials either by grafting or by co-condensation. The thiol groups were oxidized to SO3H by treatment with H2O2. All the catalysts were active in the studied reaction being the PMO-SO3H-g

José E. Castanheiro; Liliana Guerreiro; Isabel M. Fonseca; Ana M. Ramos; Joaquim Vital

2008-01-01

165

Absolute acidities and site specific properties of zeolite catalysts modelled by advanced computational chemistry technology  

Microsoft Academic Search

Hartree–Fock structure predictions are made for two crystallographically distinct Brønsted sites, O1H and O3H, of the zeolite catalyst H-faujasite. The structure optimisation adopted very large cluster models without symmetry (163 atoms; 2033 basis function) and applied the parallel TURBOMOLE code on a multi-processor compute server. The predicted acidity strength of the two sites, 1166±10 kJ\\/mol, is the same within chemical

Joachim Sauer; Uwe Eichler; Ulrich Meier; Ansgar Schäfer; Malte von Arnim; Reinhart Ahlrichs

1999-01-01

166

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

167

WO 3\\/C hybrid material as a highly active catalyst support for formic acid electrooxidation  

Microsoft Academic Search

The hybrid material based on WO3 and Vulcan XC-72R carbon has been used as the support of Pd nanocatalysts. The resultant Pd–WO3\\/C catalysts in a large range of WO3 content exhibit excellent catalytic activity and stability for formic acid electrooxidation. The great improvement in the catalytic performance is attributed to the uniform dispersion of Pd with less particle sizes on

Zhonghua Zhang; Yunjie Huang; Junjie Ge; Changpeng Liu; Tianhong Lu; Wei Xing

2008-01-01

168

Deuteriation of benzoic acid in the presence of homogeneous potassium tetrachloroplatinate(II) catalyst  

Microsoft Academic Search

The kinetic behavior of deuteriation of benzoic acid with D2O acidified with HCl in the presence of homogeneous K2PtCl4 catalyst has been investigated in the 100–130°C temperature interval. The quasiunimolecular H\\/D rate constants at 100 and 130°C corresponding to an exchange process in ortho positions of the substituted benzene ring hydrogens were determined by1H NMR integration signal. These same constants

M. Ka?ska; R. Ka?ski

1992-01-01

169

Fatty Acid Methyl Ester Synthesis over Fe 3+ -Vanadyl Phosphate Catalysts  

Microsoft Academic Search

A heterogeneous acid catalyst, Fe3+-vanadyl phosphate, prepared by the isomorphous substitution of some VO3+ groups in vanadyl phosphate with trivalent metal Fe3+, was found to be active for the transesterification of soybean oil with methanol. When the transesterification reaction was\\u000a carried out with a molar ratio of methanol to oil of 30:1, a reaction temperature of 473 K, a reaction time

Hui Li; Wenlei Xie

2008-01-01

170

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

171

A bifunctional palladium/acid solid catalyst performs the direct synthesis of cyclohexylanilines and dicyclohexylamines from nitrobenzenes.  

PubMed

Nitroderivatives are transformed to cyclohexylanilines at room temperature in good yields and selectivity via a hydrogenation-amine coupling cascade reaction using Pd nanoparticles on carbon as a catalyst and a Brönsted acid. PMID:23925659

Rubio-Marqués, Paula; Leyva-Pérez, Antonio; Corma, Avelino

2013-09-25

172

Mechanism of hydrodenitrogenation (Part 4) infrared spectroscopy of acidic molybdena catalysts. Fourth quarter report, July 1-September 30, 1990.  

National Technical Information Service (NTIS)

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 acidi...

R. Miranda

1990-01-01

173

Hydroaminations of unactivated alkenes with basic alkylamines: group 4 metal halide catalysts and Brønsted-acid organocatalysts.  

PubMed

Two distinct economical catalysts for intramolecular hydroaminations of electronically unactivated alkenes with basic amines are described, which are based on (a) group 4 metal halides under basic reaction conditions or (b) Brønsted-acid organocatalysts. PMID:17551648

Ackermann, Lutz; Kaspar, Ludwig T; Althammer, Andreas

2007-05-17

174

New Method of Determining Acid Base Strength Distribution and a New Acidity-Basicity Scale for Solid Catalysts: The Strongest Point, H (sub O).  

National Technical Information Service (NTIS)

The use of the strongest H (sub 0) as an acid-base scale is illustrated. It is concluded that the catalytic activity arises from carbonium ions for solid catalysts whose strongest point values are less than 2, from carbanions for solid catalysts whose str...

T. Yamanaka K. Tanabe

1988-01-01

175

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

176

Pd/C synthesized with citric acid: an efficient catalyst for hydrogen generation from formic acid/sodium formate.  

PubMed

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 H(2) mol(-1) catalyst h(-1), respectively, at room temperature. The present simple, low cost, but highly efficient CO-free hydrogen generation system at room temperature is believed to greatly promote the practical application of formic acid system on fuel cells. PMID:22953041

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

2012-08-23

177

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

NASA Astrophysics Data System (ADS)

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

2012-08-01

178

Comparison of sulfuric and hydrochloric acids as catalysts in hydrolysis of Kappaphycus alvarezii (cottonii).  

PubMed

In this study, hydrolysis of marine algal biomass Kappaphhycus alvarezii using two different acid catalysts was examined with the goal of identifying optimal reaction conditions for the formation of sugars and by-products. K. alvarezii were hydrolyzed by autoclave using sulfuric acid or hydrochloric acid as catalyst with different acid concentrations (0.1-1.0 M), substrate concentrations (1.0-13.5%), hydrolysis time (10-90 min) and hydrolysis temperatures (100-130 (°)C). A difference in galactose, glucose, reducing sugar and total sugar content was observed under the different hydrolysis conditions. Different by-product compounds such as 5-hydroxymethylfurfural and levulinic acid were also observed under the different reaction conditions. The optimal conditions for hydrolysis were achieved at a sulfuric acid concentration, temperature and reaction time of 0.2 M, 130 °C and 15 min, respectively. These results may provide useful information for the development of more efficient systems for biofuel production from marine biomass. PMID:21909670

Meinita, Maria Dyah Nur; Hong, Yong-Ki; Jeong, Gwi-Taek

2011-09-10

179

Aerobic oxidation of aqueous ethanol using heterogeneous gold catalysts: Efficient routes to acetic acid and ethyl acetate  

Microsoft Academic Search

The aerobic oxidation of aqueous ethanol to produce acetic acid and ethyl acetate was studied using heterogeneous gold catalysts. Comparing the performance of Au\\/MgAl2O4 and Au\\/TiO2 showed that these two catalysts exhibited similar performance in the reaction. By proper selection of the reaction conditions, yields of 90–95% of acetic acid could be achieved at moderate temperatures and pressures. Based on

Betina Jørgensen; Sofie Egholm Christiansen; Marie Louise Dahl Thomsen; Claus Hviid Christensen

2007-01-01

180

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

Microsoft Academic Search

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

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

2007-01-01

181

Dehydration of aliphatic alcohols on phosphoric acid catalyst with the addition of calcium phosphate  

SciTech Connect

The kinetic regularities of dehydration of sec- and tert-butyl alcohols on a catalyst consisting of a mixture of calcium phosphate and H/sub 3/PO/sub 4/, deposited on molten quartz were studied by pulsed gas chromatography. At an equal water vapor pressure in the system, the activity of a catalyst consisting of a pure H/sub 3/PO/sub 4/ is higher than that of a catalyst with the addition of a salt. The experimentally observed dehydration rate constants and those determined with the retention volumes taken into account were measured. Activation energies, rate constants, and the heat of dissolution of tert-butyl alcohol on calcium phosphate catalyst were determined in the range of 80-110/sup 0/C. The dehydration of sec-butyl alcohol was studied at 140/sup 0/C. It was found that in a liquid phase, the reaction rate constant is not very dependent on the salt/acid ratio.

Obraztsov, P.A.; Batalin, O.E.; Malinskii, V.S.; Shubenok, L.F.; Vinnik, M.I.

1986-12-01

182

Nanorod vanadatesulfuric acid as a novel, recyclable and heterogeneous catalyst for the one-pot synthesis of tetrahydrobenzopyrans.  

PubMed

Vanadatesulfuric acid (VSA), as a novel and heterogeneous nanorod catalyst, was used for an efficient synthesis of tetrahydrobenzo[b]pyrans using an aldehydes, 1,3-cyclohexanediones or beta-ketoester and malononitrile in C2H5OH/H2O mixture under reflux conditions. VSA is prepared via the reaction of sodium metavanadate and chlorosulfonic acid in high purity. The catalyst was characterized by FT-IR, XRD, TEM and EDAX analysis. Compared to the conventional method, this method consistently has the advantage of high yields, simple workup, short reaction times and reusability of the catalyst. PMID:23901523

Nasr-Esfahani, Masoud; Abdizadeh, Tooba

2013-07-01

183

Structural design and facile synthesis of a highly efficient catalyst for formic acid electrooxidation.  

PubMed

The pathway of formic acid electrooxidation strongly depends on the amount of three neighbouring Pt or Pd atoms in the surface of Pd- or Pt-based catalysts. Here, Pt decorated Pd/C nanoparticles (the optimal atomic ratio, Pd?:?Pt = 20?:?1) were designed and then synthesized through a facile galvanic replacement reaction where the amount of three neighbouring Pt or Pd atoms markedly decreased. As a result, discontinuous Pd and Pt atoms suppressed CO formation and exhibited unprecedented catalytic activity and stability toward formic acid electrooxidation while the cost was almost the same as that of Pd/C. PMID:21701741

Wang, Xiao-Ming; Wang, Ming-E; Zhou, Dan-Dan; Xia, Yong-Yao

2011-06-24

184

Characterization of the acid properties of tungsten/zirconia catalysts using adsorption microcalorimetry and n-pentane isomerization activity  

SciTech Connect

Ammonia adsorption microcalorimetry was conducted on various solid acid tungsten/zirconia catalysts prepared by different techniques. The calorimetric data were compared to catalytic test results using n-pentane isomerization as a measure of acid activity. The results show that (1) the co-precipitation method of making the tungsten/zirconia catalyst produces a greater number of acidic sites than impregnating tungsten on hydrous zirconia, resulting in a more active catalyst, and (2) the addition of small amounts of iron to the tungsten/zirconia catalyst increases the acid site strength as determined by ammonia adsorption and improves the paraffin isomerization activity. The calorimetry data indicate that the acid site strength of the tungsten/zirconia materials is similar to or slightly higher than that found in zeolites or sulfated zirconia and is comparable to sulfuric acid. However, the paraffin isomerization activity results suggest that the acid sites of the tungsten/zirconia catalyst should be about four orders of magnitude more active than that of zeolite {beta} on the basis of turnover frequency. Their experimental results indicate a lack of correlation between the heat of ammonia adsorption with catalytic activity. Comparisons of catalytic activity between materials based entirely on acid strength may not be valid, and kinetic probes would be more appropriate.

Vartuli, J.C.; Santiesteban, J.G.; Traverso, P.; Cardona-Martinez, N.; Chang, C.D.; Stevenson, S.A.

1999-10-01

185

Nucleic acid polymerases use a general acid for nucleotidyl transfer  

Microsoft Academic Search

Nucleic acid polymerases catalyze the formation of DNA or RNA from nucleoside-triphosphate precursors. Amino acid residues in the active site of polymerases are thought to contribute only indirectly to catalysis by serving as ligands for the two divalent cations that are required for activity or substrate binding. Two proton-transfer reactions are necessary for polymerase-catalyzed nucleotidyl transfer: deprotonation of the 3?-hydroxyl

Christian Castro; Eric D Smidansky; Jamie J Arnold; Kenneth R Maksimchuk; Ibrahim Moustafa; Akira Uchida; Matthias Götte; William Konigsberg; Craig E Cameron

2009-01-01

186

Recovery of iron oxides from acid mine drainage and their application as adsorbent or catalyst.  

PubMed

Iron oxide particles recovered from acid mine drainage represent a potential low-cost feedstock to replace reagent-grade chemicals in the production of goethite, ferrihydrite or magnetite with relatively high purity. Also, the properties of iron oxides recovered from acid mine drainage mean that they can be exploited as catalysts and/or adsorbents to remove azo dyes from aqueous solutions. The main aim of this study was to recover iron oxides with relatively high purity from acid mine drainage to act as a catalyst in the oxidation of dye through a Fenton-like mechanism or as an adsorbent to remove dyes from an aqueous solution. Iron oxides (goethite) were recovered from acid mine drainage through a sequential precipitation method. Thermal treatment at temperatures higher than 300 °C produces hematite through a decrease in the BET area and an increase in the point of zero charge. In the absence of hydrogen peroxide, the solids adsorbed the textile dye Procion Red H-E7B according to the Langmuir model, and the maximum amount adsorbed decreased as the temperature of the thermal treatment increased. The decomposition kinetics of hydrogen peroxide is dependent on the H(2)O(2) concentration and iron oxides dosage, but the second-order rate constant normalized to the BET surface area is similar to that for different iron oxides tested in this and others studies. These results indicate that acid mine drainage could be used as a source material for the production of iron oxide catalysts/adsorbents, with comparable quality to those produced using analytical-grade reagents. PMID:22820746

Flores, Rubia Gomes; Andersen, Silvia Layara Floriani; Maia, Leonardo Kenji Komay; José, Humberto Jorge; Moreira, Regina de Fatima Peralta Muniz

2012-07-20

187

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

188

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

189

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

190

New polystyrene sulfonic acid resin catalysts with enhanced acidic and catalytic properties  

Microsoft Academic Search

The effects of halogenation of polystyrene sulfonic acid resins on acidic and catalytic properties have been evaluated. Four polystyrene-co-divinylbenzene sulfonic acid resins from Rohm and Haas (Amberlyst 70, Amberlyst 15, Amberlyst 35 and Amberlyst 36) have been characterised in terms of their acidities (both strength and acid site concentrations) by ammonia adsorption flow microcalorimetry, their thermal and hydrothermal stabilities, and

P. F. Siril; H. E. Cross; D. R. Brown

2008-01-01

191

Factors Affecting the Relative Efficiency of General Acid Catalysis  

ERIC Educational Resources Information Center

|A simple framework for evaluating experimental kinetic data to provide support for Specific Acid Catalysis (SAC) and General Acid Catalysis (GAC) is described based on the factors affecting their relative efficiency. Observations reveal that increasing the SAC-to-GAC rate constant ratio reduces the effective pH range for GAC.|

Kwan, Eugene E.

2005-01-01

192

Factors Affecting the Relative Efficiency of General Acid Catalysis  

ERIC Educational Resources Information Center

A simple framework for evaluating experimental kinetic data to provide support for Specific Acid Catalysis (SAC) and General Acid Catalysis (GAC) is described based on the factors affecting their relative efficiency. Observations reveal that increasing the SAC-to-GAC rate constant ratio reduces the effective pH range for GAC.

Kwan, Eugene E.

2005-01-01

193

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

194

Enantioselective hydrogenation of isophorone with titania supported Pd catalysts modified by (?)-dihydroapovincaminic acid ethyl ester effect of the support and the reduction method  

Microsoft Academic Search

Enantioselective hydrogenation of isophorone was investigated over Pd\\/TiO2 catalysts in the presence of (?)-dihydroapovincaminic acid ethyl ester. The used supports were different in crystalline form and in surface area. The influence of the catalyst preparation method on the optical purity was studied. The catalysts were characterized by H2 adsorption and SEM.

É. S??pos; G. Farkas; A. Tungler; J. L. Figueiredo

2002-01-01

195

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

196

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

197

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

PubMed

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

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

2012-10-18

198

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); Lawrence, S. [Saginaw Valley State Univ., University Center, MI (United States)

1996-10-01

199

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

2013-03-05

200

Transition metal complexes — A new class of catalysts of interfacial alkylation for the asymmetrical synthesis of ?-amino acids  

Microsoft Academic Search

A new class of catalysts of interfacial asymmetrical alkylation is suggested for the synthesis of a-amino acids — positively charged complexes of the transition metals Cu(II), Ni(II), and Pd(II). These complexes consist of several fragments, by variation of which the structure of the catalysts can readily be modified. The complexes are chiral on account of (S)proline derivatives contained in them

V. I. Maleev; S. O. Videnskaya; M. B. Saporovskaya; V. A. Tsyryapkin; V. M. Belikov

1991-01-01

201

Use of functionalized PEG with 4-aminobenzoic acid stabilized platinum nanoparticles as an efficient catalyst for the hydrosilylation of alkenes.  

PubMed

A catalyst containing functionalized polyethylene glycol with 4-aminobenzoic acid (PEG-AMB) stabilized platinum nanoparticles has been synthesized and characterized, and its application in the hydrosilylation of alkenes investigated. It is shown that the functionalized PEG-stabilized Pt nanoparticles form a very efficient catalyst for the hydrosilylation of alkenes. The Pt nanoparticles can be fully immobilized in the PEG-AMB and recycled at least nine times without any obvious loss of catalytic activity. PMID:23295024

Bai, Ying; Zhang, Shufang; Deng, Yuan; Peng, Jiajian; Li, Jiayun; Hu, Yingqian; Li, Xiaonian; Lai, Guoqiao

2012-12-12

202

Catalytic conversion of canola oil to fuels and chemicals: roles of catalyst acidity, basicity and shape selectivity on product distribution  

Microsoft Academic Search

Studies were performed at atmospheric pressure in a fixed-bed microreactor at temperatures of 400 and 500°C over HZSM-5, silicalite, silica, silica-alumina, ?-alumina, calcium oxide and magnesium oxide catalysts to determine the various roles of catalyst acidity, basicity and shape selectivity on canola oil conversion and product distribution. Results showed that the initial decomposition of canola oil to long chain hydrocarbons

Raphael O. Idem; Sai P. R. Katikaneni; Narendra N. Bakhshi

1997-01-01

203

Chiral dendritic bis(oxazoline) copper(II) complexes as Lewis acid catalysts for enantioselective aldol reactions in aqueous media  

Microsoft Academic Search

A series of copper(II) complexes, with chiral bis(oxazoline) ligands disubstituted at the carbon atom linking the two oxazolines by Fréchet-type polyether dendrimers, have been designed and synthesized. These complexes were used as Lewis acid catalysts in enantioselective aldol reactions in aqueous media. Good yields and moderate enantioselectivities were achieved, which are comparable with those resulting from the corresponding smaller catalysts.

Bai-Yuan Yang; Xiao-Min Chen; Guo-Jun Deng; Yi-Li Zhang; Qing-Hua Fan

2003-01-01

204

MoV-based catalysts in ethane oxidation to acetic acid: Influence of additives on redox chemistry  

Microsoft Academic Search

The formation of acetic acid and\\/or ethylene by oxidation of ethane is strongly dependent on X additives or Y promotor added to MoVO-based catalysts. MoV0.4X0.12Y?Oz (X=Nb; Y=Pd; ?=10?4) catalysts were prepared by the slurry method and their structural properties were studied by in situ (redox conditions) XRD, Raman and XPS techniques. The reactivity during reduction and reoxidation was analysed by

M. Roussel; S. Barama; A. Löfberg; S. Al-Sayari; K. Karim; E. Bordes-Richard

2009-01-01

205

Effects of acidic treatments on the pore and surface properties of Ni catalyst supported on activated carbon  

Microsoft Academic Search

Activated carbon as catalyst support was treated with HCl, HNO3, and HF and the effects of acid treatments on the properties of the activated carbon support were studied by N2 adsorption, mass titration, temperature-programmed desorption (TPD), and X-ray photoelectron spectrometry (XPS). Ni catalysts supported on untreated and treated activated carbons were prepared, characterized and tested for the reforming reaction of

Shaobin Wang

1998-01-01

206

Microwave-accelerated energy-efficient esterification of free fatty acid with a heterogeneous catalyst.  

PubMed

This paper shows energy-efficiency of microwave-accelerated esterification of free fatty acid with a heterogeneous catalyst by net microwave power measurement. In the reaction condition of 5 wt% sulfated zirconia and 1:20 M ratio of oil to methanol at 60°C and atmospheric pressure, more than 90% conversion of the esterification was achieved in 20 min by microwave heating, while it took about 130 min by conventional heating. Electric energy consumption for the microwave heating in this accelerated esterification was only 67% of estimated minimum heat energy demand because of significantly reduced reaction time. PMID:21144741

Kim, Daeho; Choi, Jinju; Kim, Geun-Ju; Seol, Seung Kwon; Ha, Yun-Chul; Vijayan, M; Jung, Sunshin; Kim, Bo Hyun; Lee, Gun Dae; Park, Seong Soo

2010-11-21

207

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

SciTech Connect

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

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

2011-10-17

208

Absence of expected side-reactions in the dehydration reaction of fructose to HMF in water over niobic acid catalyst  

Microsoft Academic Search

The catalytic dehydration of fructose (FRU) to 5-hydroxymethylfurfural (HMF) usually runs with the formation of several side products. Among these, levulinic acid (LA) is often reported as the product of a consecutive reaction of HMF re-hydration. In this work, side reactions of the dehydration of FRU performed in very green conditions (water as solvent and niobic acid as solid catalyst)

Paolo Carniti; Antonella Gervasini; Matteo Marzo

2011-01-01

209

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

EPA Science Inventory

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

210

Transient response study of the formaldehyde oxidation to formic acid on V–Ti–O catalyst: FTIR and pulse study  

Microsoft Academic Search

The mechanism of the formaldehyde oxidation to formic acid on a V–Ti–O catalyst has been studied by pulse and spectrokinetic (in situ FTIR) methods. Bidentate symmetrical formates and asymmetric formates are observed by formaldehyde adsorption both in the presence and in the absence of dioxygen in the temperature range between 100 and 200°C. Formic acid may form by two parallel

Galina Ya. Popova; Tamara V. Andrushkevich; Yurii A. Chesalov; Valentin N. Parmon

2007-01-01

211

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

212

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

Microsoft Academic Search

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

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

2006-01-01

213

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

214

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

PubMed

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

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

2013-08-16

215

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 50wt.% of the holocellulose part of the lignocellulosic biomass. Moreover, 60wt.% 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

2013-08-23

216

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

PubMed Central

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

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

2013-01-01

217

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

218

Kinetic relationships in conversion of 3-methyl-1,3-butanediol on phosphoric acid catalyst with added sodium phosphate  

Microsoft Academic Search

By means of pulse chromatography on a phosphoric acid catalyst consisting of a mixture of phosphoric acid and sodium phosphates supported on quartz, a study has been made of the acid-catalyzed conversions of 3-methyl-1,3-butanediol (MBD) at 120-150°C. It has been established that the principal products are isoprene and isopropenylethyl alcohol; at long contact times, the alcohol is also dehydrated to

V. S. Malinskii; M. I. Vinnik

1988-01-01

219

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

220

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

221

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

PubMed

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

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

2011-05-06

222

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

PubMed

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

Xie, Wenlei; Yang, Dong

2011-08-09

223

Cooperative catalysis: combining an achiral metal catalyst with a chiral brønsted Acid enables highly enantioselective hydrogenation of imines.  

PubMed

Asymmetric hydrogenation of imines leads directly to chiral amines, one of the most important structural units in chemical products, from pharmaceuticals to materials. However, highly effective catalysts are rare. This article reveals that combining an achiral pentamethylcyclopentadienyl (Cp*)-iridium complex with a chiral phosphoric acid affords a catalyst that allows for highly enantioselective hydrogenation of imines derived from aryl ketones, as well as those derived from aliphatic ones, with ee values varying from 81 to 98?%. A range of achiral iridium complexes containing diamine ligands were examined, for which the ligands were shown to have a profound effect on the reaction rate, enantioselectivity and catalyst deactivation. The chiral phosphoric acid is no less important, inducing enantioselection in the hydrogenation. The induction occurs, however, at the expense of the reaction rate. PMID:24019056

Tang, Weijun; Johnston, Steven; Li, Chaoqun; Iggo, Jonathan A; Bacsa, John; Xiao, Jianliang

2013-09-09

224

A comparative study of solid carbon acid catalysts for the esterification of free fatty acids for biodiesel production. Evidence for the leaching of colloidal carbon.  

PubMed

The preparation of a variety of sulfonated carbons and their use in the esterification of oleic acid is reported. All sulfonated materials show some loss in activity associated with the leaching of active sites. Exhaustive leaching shows that a finite amount of activity is lost from the carbons in the form of colloids. Fully leached catalysts show no loss in activity upon recycling. The best catalysts; 1, 3, and 6; show initial TOFs of 0.07s(-1), 0.05s(-1), and 0.14s(-1), respectively. These compare favorably with literature values. Significantly, the leachate solutions obtained from catalysts 1, 3, and 6, also show excellent esterification activity. The results of TEM and catalyst poisoning experiments on the leachate solutions associate the catalytic activity of these solutions with carbon colloids. This mechanism for leaching active sites from sulfonated carbons is previously unrecognized. PMID:24021721

Deshmane, Chinmay A; Wright, Marcus W; Lachgar, Abdessadek; Rohlfing, Matthew; Liu, Zhening; Le, James; Hanson, Brian E

2013-08-20

225

A Skeletal Rearrangement Study of Labeled Butanes on a Solid Superacid Catalyst : Sulfuric-Acid Treated Zirconium-Oxide  

Microsoft Academic Search

The reactions of n-butane and isobutane have been studied in a flow system in the presence of hydrogen at 250°C using sulfuric acid treated zirconia as catalyst. The conversion of the butanes occurs with high selectivity in isomerization. The branched isomer reacts much faster than the linear one. The use of 13C labelled starting material and analysis of the isotope

F. Garin; L. Seyfried; P. Girard; G. Maire; A. Abdulsamad; J. Sommer

1995-01-01

226

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

Microsoft Academic Search

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

Min Xia; Yue-Dong Lu

2006-01-01

227

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

Microsoft Academic Search

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

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

2010-01-01

228

Niobic acid and niobium phosphate as highly acidic viable catalysts in aqueous medium: Fructose dehydration reaction  

Microsoft Academic Search

The catalytic properties of niobic acid (Nb2O5·nH2O) and niobium phosphate (NbOPO4) surfaces were studied in the reaction of fructose dehydration carried out in water. The reaction was performed in a continuous reactor at different temperatures 90–110°C and pressures (from 2 to 6bar). Superior activity and selectivity to 5-hydroxymethyl-2-furaldehyde (HMF) of niobium phosphate compared to niobic acid was observed. The initial

Paolo Carniti; Antonella Gervasini; Serena Biella; Aline Auroux

2006-01-01

229

Hydrotreating of coker light gas oil on Ti-HMS supported heteropolytungstic acid catalysts  

Microsoft Academic Search

Ti-HMS substrates were synthesized by using dodecylamine as structure-directing agents. A series of HPW\\/Ti-HMS catalysts with different Si\\/Ti ratios, promoted by Ni was prepared using Keggin-type heteropolyacids (H3PW12O40) as active phase precursors. These catalysts were compared with corresponding NiW\\/HMS catalysts prepared from the traditional precursors (ammonium metatungstate). Prepared supports and catalysts were characterized by small- and wide-angle XRD, N2 physisorption,

K. Soni; P. E. Boahene; K. Chandra Mouli; A. K. Dalai; J. Adjaye

2011-01-01

230

Organometallic catalysts for primary phosphoric acid fuel cells: Final report, 1981-1985  

Microsoft Academic Search

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 h in full cell at 160 to

Walsh

1987-01-01

231

Liquefaction of cellulose in the presence of phenol using p-toluene sulfonic acid as a catalyst  

Microsoft Academic Search

The kinetics of p-toluene sulfonic acid (PTSA)-catalyzed cellulose liquefaction in the presence of phenol were investigated at 130, 140 and 150°C. The resulting liquefied products were also analyzed to evaluate the effectiveness of PTSA as a catalyst during the phenol liquefaction. The liquefaction rate of PTSA was slightly lower than that of sulfuric acid (SA), which was used as a

Sung Phil Mun; Jeong Phil Jang

2009-01-01

232

Characterisation and acid properties of some modified combustion catalysts: Pt\\/alumina with barium and Pt\\/zirconia with yttrium  

Microsoft Academic Search

Platinum was deposited on alumina and zirconia, subjected or not to addition of barium or yttrium, respectively. Surface acidic properties were probed by ammonia adsorption followed by FT-IR spectroscopy and temperature-programmed desorption (TPD) using an original inductive set-up for fast heating of the sample.The Pt\\/alumina sample exhibits 0.34 acid site per nm2. The addition of barium (14.8wt%) to this catalyst

V. Labalme; B. Béguin; F. Gaillard; M. Primet

2000-01-01

233

Design of reflective tantala optical coatings using sol-gel chemistry with ethanoic acid catalyst and chelator  

Microsoft Academic Search

Sol-gel processing of Ta(OC2H5)5 to produce tantala highly reflective (HR) coating has been systematically studied in the absence of inorganic anions using an ethanoic acid catalyst in part using IR. In the presence of ethanoic acid, both hydrolysis and chelation co-exist, depending on the preparative parameters; most of the precursor was found to be converted into an amorphous chemically modified

Y. Sun; P. A. Sermon; M. S. W. Vong

1996-01-01

234

Decomposition of Carboxylic Acids in Water by O3, O3\\/H2O2, and O3\\/Catalyst  

Microsoft Academic Search

This paper studies the decomposition of formic, oxalic and maleic acids by O3, O3\\/catalyst, and O3\\/H2O2. The catalytic effect of Co, Ni, Cu, Mn, Zn, Cr, and Fe ions is investigated. The results showed that—Co and Mn have the highest catalytic activity for the decomposition of oxalic acid while the catalytic effect of the studied ions is insignificant on the

Ahmed A. Abd El-Raady; Tsuyoshi Nakajima

2005-01-01

235

SYNTHESIS OF ALKYL AND ARYLPHOSPHONIC ACID MONOESTERS BY DIRECT ESTERIFICATION OF DIBASIC PHOSPHONIC ACIDS IN THE PRESENCE OF AN ARSONIC ACID CATALYST  

Microsoft Academic Search

Partial hydrolysis of a diester, hydrolysis of the monochloro monoester, or alcoholysis of a phosphonic acid anhydride generally is used to prepare monoesters of alkyl- and arylphosphonic acids. Limited cases have been reported for the esterification of a dibasic phosphonic acid to yield the monoester, and none of these methods are as simple as the analogous method for preparing carboxylic

Michael D. Crenshaw

2004-01-01

236

Nano sulfated titania as solid acid catalyst in direct synthesis of fatty acid amides.  

PubMed

Nanosized sulfated titania was prepared by a sol-gel hydrothermal process. X-ray diffraction (XRD), transmission electron, and scanning electron micrographs (TEM and SEM), FT-IR specific surface area, and BET N(2) adsorption were employed to characterize the properties of the synthesized sulfated TiO(2). The results indicate that both anatase and rutile TiO(2) are obtainable. This prepared sulfated titania showed high catalytic activity in direct amidation of fatty acids as well as benzoic acids with various amines under solvent-free conditions. PMID:21405011

Hosseini-Sarvari, Mona; Sodagar, Esmat; Doroodmand, Mohammad Mahdi

2011-03-23

237

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

238

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

239

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

240

Relationship of generalized anxiety symptoms to urinary 5-hydroxyindoleacetic acid and vanillylmandelic acid  

Microsoft Academic Search

Urinary levels of the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) and the norepinephrine metabolite vanillylmandelic acid (VMA) were measured in 45 patients with generalized anxiety disorder. Multiple regression analysis demonstrated that the severity of several anxiety symptoms was predicted by levels of 5-HIAA and VMA. These data are consistent with the proposal that serotonin and norepinephrine may be involved in the

Michael J. Garvey; Russell Noyes; Catherine Woodman; Cindy Laukes

1995-01-01

241

Silica Sulfuric Acid, an Efficient and Recyclable Solid Acid Catalyst for the Synthesis of 4,4?-(Arylmethylene)bis (1H-pyrazol-5-ols)  

Microsoft Academic Search

Silica sulfuric acid (SSA) is employed as a recyclable catalyst for the condensation reaction of aromatic aldehydes with 3-methyl-l-phenyl-5-pyrazolone. This condensation reaction is performed in a mixture (1:1 v\\/v) of water–ethanol at 70 °C, giving 4,4?-alkylmethylene-bis(3-methyl-5-pyrazolones) in 75–93% yields.

Khodabakhsh Niknam; Salimeh Mirzaee

2011-01-01

242

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

Microsoft Academic Search

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

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

2008-01-01

243

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

2012-08-01

244

Pt, Pd and Au nanoparticles supported on a DNA-MMT hybrid: efficient catalysts for highly selective oxidation of primary alcohols to aldehydes, acids and esters.  

PubMed

Novel DNA-MMT hybrid supported metal nanoparticle catalysts, such as Pt/DNA-MMT, Pd/DNA-MMT, Au/DNA-MMT, were prepared for application in highly selective aerobic oxidation of primary alcohols to aldehydes, acids and esters, respectively. Taking advantage of the water-soluble reversibility of these catalysts, all the transformations could be performed smoothly in water and reuse of the catalysts has also been accomplished by a very simple phase separation process. PMID:23628847

Tang, Lin; Guo, Xuefeng; Li, Yunfeng; Zhang, Shuai; Zha, Zhenggen; Wang, Zhiyong

2013-06-01

245

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

SciTech Connect

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

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

1995-01-01

246

High activity of acid-treated quail eggshell catalysts in the transesterification of palm oil with methanol.  

PubMed

The transesterification of palm oil with methanol was investigated over calcium oxide catalysts prepared by calcining eggshells of quail and chicken. Compared to chicken eggshell, the palisade layer of quail eggshell had more closely dispersed micron-sized pores. Following treatment with 0.005M HCl solution for 2h to remove its dense cuticle layer and subsequent calcination above 800 degrees C, the quail eggshell had a large amount of strong basic sites and showed high catalytic activity comparable to that of potassium methoxide in the transesterification. The acid-treated, quail eggshell catalyst steadily maintained high conversions of over 98% during repeated fivefold usage at 65 degrees C with a reactant composed of methanol/oil (as mol)=12/1 and oil/catalyst (as g)=2/0.03. PMID:20621469

Cho, Yung Bok; Seo, Gon

2010-11-01

247

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

248

Nature of the acid sites of supported sulfate catalysts for the skeletal isomerization of n-pentenes  

SciTech Connect

The influence of the degree of dehydration of a sample of NiSO/sub 4//SiO/sub 2/ (7.3% Ni) on its activity in the skeletal isomerization of n-pentenes, the total acidity, and the ratio between the brnsted (B) and Lewis (L) sites, which was determined from the IR spectra of chemisorbed pyridine, has been studied. As the calcination temperature of the catalyst is increased from 150 to 300 degree C, the total acidity, as well as the B/L ratio, change only slightly, but they decrease sharply at higher calcination temperatures. It may be postulated that the decrease in the total acidity of the catalyst is due to the reduction of the number of B sites. The symbatic variation of the activity shows that the B sites are responsible for the occurrence of skeletal isomerization.

Isagulyants, G.V.; Gitis, K.M.; Kharson, M.S.; Kornyshev, V.N.

1985-10-01

249

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

2012-10-17

250

Brown algae hydrolysis in 1-n-butyl-3-methylimidazolium chloride with mineral acid catalyst system.  

PubMed

The amenability of three brown algal species, Sargassum fulvellum, Laminaria japonica and Undaria pinnatifida, to hydrolysis were investigated using the ionic liquid (IL), 1-n-butyl-3-methylimidazolium chloride ([BMIM]Cl). Compositional analyses of the brown algae reveal that sufficient amounts of sugars (15.5-29.4 wt.%) can be recovered. Results from hydrolysis experiments show that careful selection of the type of mineral acid as catalyst and control of acid loading could maximize the recovery of sugars. Optimal reaction time and temperature were determined from the kinetic studies on the sequential reducing sugar (TRS) formation and degradation. Optimal reaction times were determined based on the extent of furfurals formation as TRS degradation products. X-ray diffraction and environmental scanning electron microscopy confirmed the suitability of [BMIM]Cl as solvent for the hydrolysis of the three brown algae. Overall results show the potential of brown algae as renewable energy resources for the production of valuable chemicals and biofuels. PMID:22721878

Malihan, Lenny B; Nisola, Grace M; Chung, Wook-Jin

2012-05-26

251

Production of methacrylic acid by vapor-phase aldol condensation of propionic acid with formaldehyde over silica-supported metal phosphate catalysts  

Microsoft Academic Search

The vapor-phase aldol condensation of propionic acid (PA) with formaldehyde (HCHO) to form methacrylic acid (MAA) was performed with a PA\\/HCHO molar ratio of 2 using various silica-supported metal phosphate catalysts. In the absence of water, a silica-supported tin phosphate with Sn\\/Si\\/P atomic ratio of 1\\/8\\/2.3 showed the same level of performance as a silica-supported vanadium phosphate with V\\/Si\\/P atomic

Mamoru Ai; Hideyuki Fujihashi; Sanae Hosoi; Akiyo Yoshida

2003-01-01

252

Alkali Doping Heterogeneous Catalysts.  

National Technical Information Service (NTIS)

Alkali doping mechanisms were considered: catalytic action of the alkali; creation of basic centers; neutralization of acid centers; alteration of the electronic properties of the catalyst surface; remedies for catalyst preparation; influencing the physic...

W. D. Mross

1983-01-01

253

Kinetic relationships in conversion of 3-methyl-1,3-butanediol on phosphoric acid catalyst with added sodium phosphate  

SciTech Connect

By means of pulse chromatography on a phosphoric acid catalyst consisting of a mixture of phosphoric acid and sodium phosphates supported on quartz, a study has been made of the acid-catalyzed conversions of 3-methyl-1,3-butanediol (MBD) at 120-150/sup 0/C. It has been established that the principal products are isoprene and isopropenylethyl alcohol; at long contact times, the alcohol is also dehydrated to isoprene. It has been shown that the reaction of MBD conversion is irreversible and is first-order with respect to the reactant. Rate constants have been determined for individual stages of the process.

Malinskii, V.S.; Vinnik, M.I.

1988-01-01

254

Preparation of high energy fuel JP-10 by acidity-adjustable chloroaluminate ionic liquid catalyst  

Microsoft Academic Search

The isomerization of endo-tetrahydrodicyclopentadiene (endo-THDCPD) to its exo-isomer (JP-10) has been investigated by using chloroaluminate ionic liquids (ILs) as catalysts. The catalyst activity and selectivity could be optimized by varying the mole fraction of AlCl3 in the IL. Undesirable by-products derived from side-reactions such as skeletal rearrangement, alkylation, cracking, and dimerization could be minimized by appropriate catalyst design and adjustment

Ming-Yu Huang; Jung-Chung Wu; Fuh-Sheng Shieu; Jiang-Jen Lin

2011-01-01

255

Dehydration of aliphatic alcohols on phosphoric acid catalyst with the addition of calcium phosphate  

Microsoft Academic Search

The kinetic regularities of dehydration of sec- and tert-butyl alcohols on a catalyst consisting of a mixture of calcium phosphate and HâPOâ, deposited on molten quartz were studied by pulsed gas chromatography. At an equal water vapor pressure in the system, the activity of a catalyst consisting of a pure HâPOâ is higher than that of a catalyst with the

P. A. Obraztsov; O. E. Batalin; V. S. Malinskii; L. F. Shubenok; M. I. Vinnik

1986-01-01

256

High efficient electrocatalytic oxidation of formic acid on Pt\\/polyindoles composite catalysts  

Microsoft Academic Search

Four novel composite catalysts have been developed by the electrodeposition of Pt onto glassy carbon electrode (GCE) modified with polyindoles: polyindole, poly(5-methoxyindole), poly(5-nitroindole) and poly(5-cyanoindole). As-formed composite catalysts are characterized by SEM, XRD and electrochemical analysis. Compared with Pt nanoparticles, respectively, deposited on the bare GCE and on the GCE modified with polypyrrole, the four newly developed composite catalysts exhibit

Weiqiang Zhou; Yukou Du; Hongmei Zhang; Jingkun Xu; Ping Yang

2010-01-01

257

Heterogeneous liquid-phase hydration of isobutene by heteropoly acid–polymer composite film catalyst  

Microsoft Academic Search

H3PMo12O40-polymer composite film catalysts were prepared by blending these two materials using a methanol–chloroform mixture by a membrane\\u000a preparation technique. Polyphenylene oxide (PPO), polyethersulfone (PES) and polysulfone (PSF) were used as blending polymers.\\u000a A H3PMo12O40-PPO composite catalyst coated on Al2O3 was also prepared. These catalysts were used as heterogeneous catalysts for the liquid-phase tert-butanol (TBA) synthesis\\u000a from isobutene and water.

Seong Soo Lim; Yong Heon Kim; Gyo Ik Park; Wha Young Lee; In Kyu Song; Hyun Ki Youn

1999-01-01

258

Dynamic behavior of reaction intermediates on catalyst surfaces in the working state: Behavior of formate ion during the decomposition of formic acid on Ni\\/SiO 2 catalyst  

Microsoft Academic Search

The reactivity of the formate ions on Ni\\/SiO2 catalyst was examined during the course of the formic acid decomposition. It is of great interest to note that the reactivity was markedly increased by the presence of formic acid in the ambient gas compared to that at the same coverage under vacuum. It is accordingly suggested that the formate ion behaves

Keiko Takahashi; Etsuko Miyamoto; Kikuo Shoji; Kenzi Tamaru

1988-01-01

259

N -alkylation of aniline with ethanol over an industrial niobic acid catalyst – influence of water formation on kinetics and selectivity  

Microsoft Academic Search

The reaction of aniline with ethanol was carried out over an industrial niobic acid catalyst in a fixed bed reactor at atmospheric pressure and 220–260 °C. The main products, N-ethylaniline and N,N-diethylaniline were formed consecutively. A kinetic study including a model discrimination between several Hougen\\/Watson type rate equations led to an Eley\\/Rideal mechanism, where the reaction of gas phase aniline with

B. Frank; D. Habel; R. Schomäcker

2005-01-01

260

Photocatalytic degradation of Acid Red 1 dye using ZnO catalyst in the presence and absence of silver  

Microsoft Academic Search

The investigation of the degradation of Acid Red 1 (AR1) dye was carried out in an aqueous suspension photoreactor. Different parameters that affect the degradation of AR1 dye such as the presence and absence of a photocatalyst, light source, air, catalyst loading, initial substrate concentration were studied. The activity of Ag-doped ZnO prepared by photoreduction of Ag ion on ZnO

B. H. Hameed; U. G. Akpan; K. P. Wee

2011-01-01

261

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

PubMed Central

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

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

2013-01-01

262

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

Microsoft Academic Search

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

Hongyao Zeng; Hua Li; Huawu Shao

2009-01-01

263

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

264

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

Microsoft Academic Search

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

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

1993-01-01

265

Catalytic Reduction of Nitrate by Pd\\/SnO2 Catalyst Using Formic Acid as Reducing Agent  

Microsoft Academic Search

In current study, the Pd\\/SnO2 catalyst had been prepared successfully by using precipitation method and its characters were analyzed by XRD (X-ray diffraction), SEM (Transmission electron microscopy) and Specific surface area analyzer etc. The catalytic reduction of nitrate (100ppm) in deionized water was investigated in a batch reactor at room temperature and atmospheric pressure, with formic acid (FA) used as

Yibao Wu; Yongyou Hu; Jianhua Cheng; Yanni Guo

2010-01-01

266

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

267

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

Microsoft Academic Search

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

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

2003-01-01

268

Aluminum Chlorhydroxide-Phosphoric Acid Catalyst System for Flash Cure Treatments to Give Improved Durable-Press Properties in Cellulose-Containing Textiles.  

National Technical Information Service (NTIS)

In this patent application an aluminum chlorhydroxide-phosphoric acid catalyst system has been devised that is practical for treatments of cellulose-containing textile materials with formaldehyde and formaldehyde-amide adducts under flash curing condition...

R. M. H. Kullman R. M. Reinhardt

1976-01-01

269

Arenesulfonic acid functionalized mesoporous silica as a novel acid catalyst for the liquid phase Beckmann rearrangement of cyclohexanone oxime to ?-caprolactam  

Microsoft Academic Search

Beckmann rearrangement of cyclohexanone oxime to ?-caprolactam was performed in liquid phase for the first time on arenesulfonic acid-functionalized SBA-15 (SBA-ar-SO3H) mesoporous silica with different loadings of the acid. The catalysts were prepared via co-condensation of 2-(4-chlorosulfonylphenyl)ethyltrimethoxysilane (CSPTMS) and tetraethyl orthosilicate (TEOS) in the presence of Pluronic 123 (EO20PO70EO20) and characterized by XRD, N2 adsorption–desorption, TGA, EA and acid–base titration

Xueguang Wang; Chin-Chang Chen; Shih-Yuan Chen; Yun Mou; Soofin Cheng

2005-01-01

270

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

SciTech Connect

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

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

2008-03-15

271

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

PubMed Central

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

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

2013-01-01

272

Acidity and acid catalysis of polyatom-substituted H n PW 11 M 1 O 40 (M=V, Nb, Ta, and W) Keggin heteropolyacid catalysts  

Microsoft Academic Search

Acidity of polyatom-substituted H\\u000a n\\u000a PW11M1O40 (M=V, Nb, Ta, and W) Keggin heteropolyacids (HPAs) was measured by NH3-TPD experiments. Acidity decreased in the order of H3PW11W1O40>H4PW11V1O40>H4PW11Nb1O40>H4PW11Ta1O40. Vapor-phase dehydration of cyclohexanol was conducted as a model reaction to correlate the acidity with the acid catalysis\\u000a of HPA catalysts. Yield for cyclohexene (a product by acid catalysis) increased with increasing acidity of

Dong Ryul Park; Ung Gi Hong; Sun Ho Song; Jeong Gil Seo; Sung-Hyeon Baeck; Jin Suk Chung; In Kyu Song

2010-01-01

273

Production of middle distillate in a dual-bed reactor from synthesis gas through wax cracking: Effect of acid property of Pd-loaded solid acid catalysts on the wax conversion and middle distillate selectivity  

Microsoft Academic Search

Selective production of middle distillate (C10–C20) from synthesis gas (CO+H2) was carried out in a dual-bed reactor. Co-based catalysts were used in the first-bed reactor to produce wax (C21+) from synthesis gas, and Pd-loaded solid acid catalysts were used in the second-bed reactor to produce middle distillate from wax through hydrocracking. Co\\/TiO2 catalyst in the first-bed reactor produced more than

Kyung Min Cho; Sunyoung Park; Jeong Gil Seo; Min Hye Youn; Sung-Hyeon Baeck; Ki-Won Jun; Jin Suk Chung; In Kyu Song

2008-01-01

274

p-Hydroxybenzoic acid degradation by Fe\\/Pd-HNT catalysts with in situ generated hydrogen peroxide  

Microsoft Academic Search

Pd- and Fe\\/Pd-HNT were elaborated by successive ionic exchange and wet impregnation at room temperature of hydrogenotitanate nanotubes (HNT) nanomaterials. Hydrogen peroxide was generated in situ via reaction of oxygen and formic acid (FA) over Fe\\/Pd-HNT catalysts. A high p-hydroxybenzoic acid (p-HBz) mineralization was achieved (52%) using Fe\\/Pd-HNT\\/FA\\/O2\\/UV system compared to the simulated reaction using Fe\\/Pd-HNT\\/H2O2\\/UV system (34%). The rate

Asma Turki; Hafedh Kochkar; Gilles Berhault; Abdelhamid Ghorbel

2010-01-01

275

Catalytic wet-air oxidation of aqueous solutions of formic acid, acetic acid and phenol in a continuous-flow trickle-bed reactor over Ru\\/TiO 2 catalysts  

Microsoft Academic Search

Catalytic wet-air oxidation of aqueous solutions of formic acid, acetic acid and phenol was carried out in a trickle-bed reactor at T=328–523K and total pressures up to 50bar over various Ru\\/TiO2 catalysts. Complete oxidation of formic acid was obtained at mild operating conditions, and no catalyst deactivation occurred that could be attributed to the dissolution of active ingredient material. It

Albin Pintar; Jurka Batista; Tatjana Tišler

2008-01-01

276

Evaluating food fortification options: general principles revisited with folic acid.  

PubMed Central

OBJECTIVES. This article uses folic acid as an example to illustrate some of the complex issues and general principles that emerge when evaluating fortification of the food supply as one possible means to address a public health recommendation. METHODS. Distributions of current daily folate intakes from conventional foods and dietary supplements were estimated. Intakes that might result from fortification of cereal-grain products and ready-to-eat cereals at various levels for eight age-gender groups were also estimated by using the US Department of Agriculture's 1987-1988 Nationwide Food Consumption Survey. RESULTS. The results illustrate that fortification of the US food supply tends to increase folate intakes of consumers at the high end of the intake distribution curves in the general population to a greater extent than it affects consumers at the low end of the intake distribution curves in the target population. CONCLUSIONS. The effectiveness of food fortification options for a target population and the safety for the general population impose conflicting challenges that must be considered concurrently when making decisions about fortifying the US food supply. Images FIGURE 4 FIGURE 5

Crane, N T; Wilson, D B; Cook, D A; Lewis, C J; Yetley, E A; Rader, J I

1995-01-01

277

Catalytic reactions of formate. 3. Noble metal chlorides as catalyst precursors for formic acid reactions  

Microsoft Academic Search

Noble metal chlorides (‘RuCl3·xH2O’, ‘RhCl3·3H2O’, PdCl2 and ‘IrCl3·xH2O’) have been evaluated as catalyst precursors for the decomposition (HCO2H ? H2 + CO2), dehydration (HCO2H ? H2O + CO) and air oxidation (2HCO2H + O2 ? 2H2O + 2CO2) of 88% HCO2H at 75–80 °C. RhCl3 under these conditions is an active oxidation catalyst but not an active decomposition catalyst. However,

R. Bruce King; Allen D. King; Nripendra K. Bhattacharyya

1995-01-01

278

Niobium, catalyst repair kit  

Microsoft Academic Search

This paper reports that niobium oxides, when small amounts are added to known catalysts, enhance catalytic activity and selectivity and prolong catalyst life. Moreover, niobium oxides exhibit a pronounced effect as supports of metal or metal oxide catalysts. Recently we found that the surface acidity of hydrated niobium pentoxide, niobic acid (NbâOâ {center dot} nHâO), corresponds to the acidity of

Tanabe

1991-01-01

279

Glutamic acid 160 is the acid-base catalyst of ?-xylosidase from Bacillus stearothermophilus T-6: a family 39 glycoside hydrolase  

Microsoft Academic Search

A ?-xylosidase from Bacillus stearothermophilus T-6 was cloned, overexpressed in Escherichia coli and purified to homogeneity. Based on sequence alignment, the enzyme belongs to family 39 glycoside hydrolases, which itself forms part of the wider GH-A clan. The conserved Glu160 was proposed as the acid-base catalyst. An E160A mutant was constructed and subjected to steady state and pre-steady state kinetic

Tsafrir Bravman; Adva Mechaly; Smadar Shulami; Valery Belakhov; Timor Baasov; Gil Shoham; Yuval Shoham

2001-01-01

280

Catalysts and Processes for Formaldehyde-Free Durable Press Finishing of Cotton Textiles with Polycarboxylic Acids.  

National Technical Information Service (NTIS)

The invention relates to new esterification catalysts and esterification processes for crosslinking cellulose as a means of imparting wrinkle resistance and smooth drying properties to cellulosic textiles without the use of formaldehyde or derivatives tha...

C. M. Welch B. K. Andrews

1988-01-01

281

General Method for Determination of the Surface Composition in Bimetallic Nanoparticle Catalysts from the L Edge X-ray Absorption Near-Edge Spectra  

SciTech Connect

Bimetallic PtPd on silica nano-particle catalysts have been synthesized and their average structure determined by Pt L3 and Pd K-edge extended X-ray absorption finestructure (EXAFS) spectroscopy. The bimetallic structure is confirmed from elemental line scans by STEM for the individual 1-2 nm sized particles. A general method is described to determine the surface composition in bimetallic nanoparticles even when both metals adsorb, for example, CO. By measuring the change in the L3 X-ray absorption near-edge structure (XANES) spectra with and without CO in bimetallic particles and comparing these changes to those in monometallic particles of known size the fraction of surface atoms can be determined. The turnover rates (TOR) and neopentane hydrogenolysis and isomerization selectivities based on the surface composition suggest that the catalytic and spectroscopic properties are different from those in monometallic nano-particle catalysts. At the same neo-pentane conversion, the isomerization selectivity is higher for the PtPd catalyst while the TOR is lower than that of both Pt and Pd. As with the catalytic performance, the infrared spectra of adsorbed CO are not a linear combination of the spectra on monometallic catalysts. Density functional theory calculations indicate that the Pt-CO adsorption enthalpy increases while the Pd-CO bond energy decreases. The ability to determine the surface composition allows for a better understanding of the spectroscopic and catalytic properties of bimetallic nanoparticle catalysts.

Wu, Tiapin; Childers, David; Gomez, Carolina; Karim, Ayman M.; Schweitzer, Neil; Kropf, Arthur; Wang, Hui; Bolin, Trudy B.; Hu, Yongfeng; Kovarik, Libor; Meyer, Randall; Miller, Jeffrey T.

2012-10-31

282

Comparison of mesoporous solid acid catalysts in the production of DABCO by cyclization of ethanolamine  

Microsoft Academic Search

DABCO have been synthesized under vapor phase reaction conditions using ethanolamine in the presence of water over synthesized and characterized Zn–Al–MCM-41 and Al–MCM-41 as catalysts. On increasing the Si\\/(Zn+Al) ratios of Zn–Al–MCM-41 and Si\\/Al ratios of Al–MCM-41 catalysts from 75 to 380 and 21 to 104 respectively, the yield and selectivity of DABCO decreased. This may be due to the

Manickam Selvaraj; Byoung Ryul Min; Yong Gun Shul; Tai Gyu Lee

2004-01-01

283

Sulfated zirconia as a solid acid catalyst for the dehydration of fructose to 5-hydroxymethylfurfural  

Microsoft Academic Search

Sulfated zirconia was prepared by impregnation with H2SO4, and was characterized using BET surface area, XRD, TG–DTA and FT-IR techniques. The sulfated zirconia was evaluated as a catalyst for the dehydration of fructose to 5-hydroxymethylfurfural (5-HMF) by microwave heating. With sulfated zirconia catalyst, high fructose conversion of 93.6% with 5-HMF yield of 72.8% could be attained at 180°C for 20min

Xinhua Qi; Masaru Watanabe; Taku M. Aida; Richard L. Smith Jr.

2009-01-01

284

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

285

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

PubMed

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

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

2013-09-10

286

40 CFR 72.71 - Acceptance of State Acid Rain programs-general.  

Code of Federal Regulations, 2010 CFR

...2009-07-01 false Acceptance of State Acid Rain programs-general. 72.71 ...CONTINUED) PERMITS REGULATION Acid Rain Phase II Implementation § 72.71 Acceptance of State Acid Rain programsâgeneral. (a)...

2009-07-01

287

40 CFR 72.71 - Acceptance of State Acid Rain programs-general.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Acceptance of State Acid Rain programs-general. 72.71 ...CONTINUED) PERMITS REGULATION Acid Rain Phase II Implementation § 72.71 Acceptance of State Acid Rain programsâgeneral. (a)...

2010-07-01

288

40 CFR 72.71 - Acceptance of State Acid Rain programs-general.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Acceptance of State Acid Rain programs-general. 72.71 ...CONTINUED) PERMITS REGULATION Acid Rain Phase II Implementation § 72.71 Acceptance of State Acid Rain programsâgeneral. (a)...

2013-07-01

289

40 CFR 72.71 - Acceptance of State Acid Rain programs-general.  

Code of Federal Regulations, 2010 CFR

...2012-07-01 false Acceptance of State Acid Rain programs-general. 72.71 Section...PROGRAMS (CONTINUED) PERMITS REGULATION Acid Rain Phase II Implementation § 72.71 Acceptance of State Acid Rain programsâgeneral. (a)...

2012-07-01

290

Carbon-supported, selenium-modified ruthenium-molybdenum catalysts for oxygen reduction in acidic media.  

PubMed

The stability and oxygen reduction activity of two carbon-supported catalyst materials are reported. The catalysts, Se/Ru and Se/(Ru-Mo), were prepared by using a chemical reduction method. The catalyst nanoparticles were evenly dispersed onto globular amorphous carbon supports, and their average size was ca. 2.4 nm. Thermal treatment at 500 °C for 2 h in an inert argon atmosphere resulted in coarsening of the nanoparticles, and also in some decrease of their activity. A gradual reduction of activity was also observed for Se/Ru during potential-cycle experiments. However, the incorporation of small amounts of Mo into the Se/Ru catalysts considerably improved the stability of the catalyst against dissolution. The Mo-containing samples showed excellent oxygen reduction activities even after cycling the potential 1000 times between 0.7 and 0.9 V. Furthermore, they showed excellent fuel-cell behavior. The performance of the Se/Ru catalysts is greatly improved by the addition of small amounts of elemental Mo. Possible mechanisms responsible for the improvement of the activity are discussed. PMID:19554605

Guinel, Maxime J-F; Bonakdarpour, Arman; Wang, Biao; Babu, Panakkattu K; Ernst, Frank; Ramaswamy, Nagappan; Mukerjee, Sanjeev; Wieckowski, Andrzej

2009-06-24

291

A skeletal rearrangement study of labelled butanes on a solid superacid catalyst: Sulfuric acid treated zirconium oxide  

SciTech Connect

Under the pressure of the worldwide trend towards more severe environmental legislation the refining industry has started to produce cleaner fuels. The reactions of n-butane and isobutane have been studied in a flow system in the presence of hydrogen at 250{degrees}C using sulfuric acid treated zirconia as catalyst. The conversion of the butanes occurs with high selectivity in isomerization. The branched isomer reacts much faster than the linear one. The use of {sup 13}C labelled starting material and analysis of the isotopic distribution in the products show that the rearrangement is of intramolecular nature in accord with the superacidic properties of the catalyst. 26 refs., 3 figs., 4 tabs.

Garin, F.; Seyfried, L.; Girard, P.; Maire, G.; Abdulsamad, A.; Sommer, J. [Universite Louis Pasteur, Strasbourg (France)

1995-01-01

292

Valproic acid alleviates generalized hyperalgesia in mice with induced adenomyosis.  

PubMed

Emerging evidence suggests that adenomyosis, like endometriosis, may also be an epigenetic disease. In this study, we evaluated the effect of valproic acid (VPA) in ICR mice with adenomyosis, induced by neonatal dosing with tamoxifen. For all mice, we evaluated the bodyweight and the response to thermal stimuli by hotplate and tail-flick tests 4, 8, and 12 weeks after dosing, respectively, and then treated mice with low- and high-dose of VPA, progesterone (P4), P4 + VPA, or vehicle only. Three weeks after treatment, both bodyweight and thermal response tests were evaluated again before sacrifice, and the depth of myometrial infiltration was evaluated. We found that: (i) the induction of adenomyosis resulted in progressive generalized hyperalgesia as measured by hotplate and tail-flick tests, along with decreased bodyweight; (ii) treatment with VPA, P4, or a combination was efficacious in improving generalized hyperalgesia; and (iii) drug treatment appeared to reduce the myometrial infiltration, but the difference did not reach statistical significance. Thus, VPA seems to be a promising therapeutics for treating adenomyosis, as reported recently in some case series in humans. PMID:21651672

Liu, Xishi; Guo, Sun-Wei

2011-06-09

293

Atmospheric secondary aerosol formation by heterogeneous reactions of aldehydes in the presence of a sulfuric acid aerosol catalyst.  

PubMed

Particle growth by the heterogeneous reaction of aldehydes was evaluated in 0.5 m3 Teflon film bags under darkness in the presence of background seed aerosols. The aldehydes used were as follows: glyoxal, butanal, hexanal, octanal, and decanal. To study acid catalyst effects on aldehyde heterogeneous reactions, one of the Teflon bags was initially filled with seed aerosols composed of ammonium sulfate-aerosol acidified with sulfuric acid. These results were compared to particle growth reactions that contained only ammonium sulfate as a background seed aerosol. The gas-phase aldehydes were then added to the Teflon bags. In selected experiments, 1-decanol was also added to the Teflon bags with aldehydes to clarify particle growth via a heterogeneous hemiacetal/acetal formation in the presence/absence of an acid catalyst. The particle size distribution and growth were measured using a scanning mobility particle sizer (TSI-SMPS), and the results were applied to predicting aerosol growth and size distribution changes by condensation and heterogeneous reactions. Aerosols created from the heterogeneous reactions of aldehydes were collected directly on an ungreased zinc selenide (ZnSe) FTIR disk (25 mm in diameter) by impaction. The ZnSe disks were directly analyzed for product functional groups inthe aerosol phase using a Fourier transform infrared (FTIR) spectrometer with a deuterated triglycine sulfate (DTGS) detector. Aerosol growth by heterogeneous aldehyde reactions proceeds via a hydration, polymerization process, and hemiacetal/acetal formation from the reaction of aldehydes with alcohols. These aldehyde heterogeneous reactions were accelerated in the presence of an acid catalyst, H2SO4, and led to higher aerosol yields than when H2SO4 was not present in the seed aerosol. The FTIR spectra obtained from the growing aerosol, also illustrated aldehyde group transformation in the particle phase as a function of the heterogeneous reaction. It was concluded that aldehydes, which can be produced by atmospheric photochemical reactions, can significantly contribute on secondary aerosol formation through heterogeneous reactions in the presence of an acid catalyst. PMID:11775150

Jang, M; Kamens, R M

2001-12-15

294

Influence of the starting aluminum salt on the surface and acid properties of AlPO/sub 4/ catalysts precipitated with ammonium hydroxide  

SciTech Connect

In this paper, the influence of the starting aluminum salt (chloride, nitrate, or sulfate) and the pretreatment temperature (773-1273 K) on textural properties, crystal structure, and surface acidity of AlPO/sub 4/ (Al/P = 1) catalysts was studied in order to learn how preparation conditions affect catalyst activity in organocationic reactions. The catalysts were characterized using nitrogen adsorption, X-ray diffraction, infrared spectroscopy, and thermogravimetric analyses. The surface acid properties were determined using a dynamic method that consists of determining the AlPO/sub 4/'s catalytic activity in cyclohexene skeletal isomerization (CSI), a reaction that requires the presence of strong surface acid sites. Catalytic activity (as apparent rate constants), activation energies, and selectivities to 1-methylcyclopentene (1-MCP) were calculated in terms of Bassett-Habgood's kinetic model for first-order processes in which the surface reaction is the controlling step and the partial pressure of the reactant is low. Significant differences in structure, texture, surface acidity, and catalytic activity in CSI were found, showing that the aluminum starting salt plays an important role in the final properties of AlPO/sub 4/ (Al/P molar ratio = 1) catalysts. Thus, aluminum nitrate yielded material with higher surface area and low activity for CSI while aluminum sulfate resulted in higher surface acidity, and hence catalytic activity for CSI, although the sample is highly crystalline exhibiting low surface area. Aluminum chloride produces porous catalysts although they are less acidic.

Campelo, J.M.; Garcia, A.; Luna, D.; Marinas, J.M.

1988-05-01

295

Solid acids as catalysts for the conversion of D-xylose, xylan and lignocellulosics into furfural in ionic liquid.  

PubMed

With the aim to develop an ecologically viable catalytic pathway for furfural production without the use of inorganic acids, H3PW12O40, Amberlyst-5 and NKC-9 (macroporous styrene-based sulfonic acid resin) were used as catalysts for producing furfural from xylose, xylan and lignocellulosic biomass in [BMIM]Cl under microwave irradiation at atmospheric pressure. A surprisingly high furfural yield of 93.7% from xylan was obtained by H3PW12O40 at 160 °C in 10 min. The degradation of furfural affected by single addition of [BMIM]Cl and solid acids was also investigated. The IL could be easily recycled and reused with stable solvent capacity for multiple runs (5×) after the product furfural was extracted with ethyl acetate. PMID:23567725

Zhang, Luxin; Yu, Hongbing; Wang, Pan

2013-03-18

296

Hydrogen storage and delivery: immobilization of a highly active homogeneous catalyst for the decomposition of formic acid to hydrogen and carbon dioxide  

Microsoft Academic Search

The homogeneous catalytic system, based on water-soluble ruthenium(II)–TPPTS catalyst (TPPTS = meta-trisulfonated triphenylphosphine),\\u000a selectively decomposes HCOOH into H2 and CO2 in aqueous solution. Although this reaction results in only two gas products, heterogeneous catalysts could be advantageous\\u000a for recycling, especially for dilute formic acid solutions, or for mobile, portable applications. Several approaches have\\u000a been used to immobilize\\/solidify the homogeneous ruthenium–TPPTS catalyst based

Weijia Gan; Paul J. Dyson; Gábor Laurenczy

2009-01-01

297

Selective reduction of nitrogen monoxide by catalysts based on composites between solid acid and perovskite in the presence of excess oxygen  

Microsoft Academic Search

The influence of the acid property of solid acids on the selective reduction of nitrogen monoxide by catalyst composites from perovskite and solid acid materials was examined for the case of excess of oxygen by using the perovskite YFeO3 and the solid acids TiO2 and ZrO2. For comparison cordierite was likewise employed as support material. It is shown that the

G. Knell; P. Kessler; E. Plies

1996-01-01

298

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

299

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

2013-05-03

300

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

2010-12-30

301

Highly efficient and convenient Strecker reaction of carbonyl compounds and amines with TMSCN catalyzed by MCM-41 anchored sulfonic acid as a recoverable catalyst  

Microsoft Academic Search

MCM-41 anchored sulfonic acid (MCM-41–SO3H) was found to be a highly efficient and recoverable heterogeneous catalyst for the three-component Strecker reaction of aldehydes or ketones and diverse amines using trimethylsilyl cyanide (TMSCN) to afford the corresponding ?-amino nitriles under mild conditions in high to quantitative yields. The simple experimental procedure along with easy recovery and reusability of the catalyst has

Mohammad G. Dekamin; Zahra Mokhtari

302

Pd-modified Au on carbon as an effective and durable catalyst for the direct oxidation of HMF to 2,5-furandicarboxylic acid.  

PubMed

Mixed noblility: We show that the modification of a gold/carbon catalyst with platinum or palladium produces stable and recyclable catalysts for the selective oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA): the support and nanoparticle chemistry directly mediate the selective oxidation of terminal hydroxyl groups in bio-derived HMF. This finding is a significant advance over current conversion technology because of the technological importance of FDCA. PMID:23495091

Villa, Alberto; Schiavoni, Marco; Campisi, Sebastiano; Veith, Gabriel M; Prati, Laura

2013-03-11

303

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

PubMed Central

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

Nan, Guangming; Ren, Fang

2010-01-01

304

Silica Phosphoric Acid (SPA) as a Highly Active, Reusable, Heterogeneous Catalyst for the Synthesis of 2Amino\\/Anilino5ARYL1,3,4Thiadiazine Bromide Derivatives  

Microsoft Academic Search

Silica phosphoric acid has been found to be an efficient catalyst for the synthesis of 2-amino\\/anilino-5-aryl-1,3,4-thiadiazine bromide derivatives from the reaction of thiosemicarbazide and ?-bromoketones in acetonitrile at room temperature. The catalyst can be reused for four times without any significant loss of catalytic activity. The experimental procedure is simple, and the products are obtained in high yield.

Shahnaz Rostamizadeh; Ali Mohammad Amani; Nasrin Shadjou

2012-01-01

305

The effect of chiral solvent and various kinds of chiral organic salts on the asymmetric hydrogenation of methyl acetoacetate over an improved tartaric acid modified Raney nickel catalyst  

Microsoft Academic Search

The influence of the chiral ionic liquid (CIL) on the asymmetric hydrogenation of methyl acetoacetate (MAA) over an improved\\u000a tartaric acid-modified Raney nickel catalyst using it as reaction medium was investigated. At the same time, we also studied\\u000a the effect of up to eight chiral ionic salts, and ionic liquids on this reaction using these ionic salts as co-catalyst. Although

Chaofeng Wang; Yunfeng Zheng; Shunli Cai; Jiantai Ma; Rong Li

2008-01-01

306

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

PubMed

Sulfamic acid (NH(2)SO(3)H, SA) was used as an efficient, inexpensive, non-toxic and recyclable green catalyst for the ultrasound-assisted one-pot Mannich reaction of aldehydes with ketones and amines. This ultrasound protocol has advantages of high yield, mild condition, no environmental pollution, and simple work-up procedures. Most importantly, beta-aminocarbonyl compounds with ortho-substituted aromatic amines are obtained in acceptable to good yields by this methodology for the first time. PMID:19394889

Zeng, Hongyao; Li, Hua; Shao, Huawu

2009-03-27

307

Infrared study of the adsorption of formic acid on clean and Ca-promoted Pd\\/SiO 2 catalysts  

Microsoft Academic Search

The adsorption and decomposition of formic acid on a highly dispersed supported Pd\\/SiO2 catalyst (2wt.% Pd) prepared via ion exchange (IE) of [Pd(NH3)4]2+ in alkaline solution, together with two Ca-promoted preparations (Ca\\/Pd=2at.\\/at.) where calcium was added either to the prereduced Pd crystallites or to the diammine palladium complex, were studied by FTIR at 298–653K.On the support, HCOOH is mostly adsorbed

Griselda C Cabilla; Adrian L Bonivardi; Miguel A Baltanás

2003-01-01

308

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

309

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

Microsoft Academic Search

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

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

2012-01-01

310

Role of surface-oxygen binding energy and surface acidity in the oxidation of o-xylene on vanadium-molybdenum oxide catalysts  

Microsoft Academic Search

using a thermostated metering tap. The acidity was determined as described in [ 9], the indicator reaction being cumene cracking. The method is based on the fact that, as is known, the activity of solid cumene-cracking catalysts is proportional to their surface acidity, as determined by measuring the adsorption of organic bases (butylamine, pyridine, quinoline, etc.) and other methods. In

Yu. I. Pyatnitskii; G. I. Golodets; T. G. Skorbilina; O. K. Biryukovich

1978-01-01

311

Alkali metal salts and ammonium salts of Keggin-type heteropolyacids as solid acid catalysts for liquid-phase Friedel-Crafts reactions  

Microsoft Academic Search

The possibility of using a heteropolyacid salt as solid acid catalyst for liquid-phase Friedel-Crafts reactions was investigated through extensive examinations on various kinds of the salt prepared from different combinations of Keggin anions and their counter cations including ammonium ion. The catalytic behavior of the salt was discussed in relation to acidity, surface area, porosity, and thermal stability. Of the

Yusuke Izumi; Mayumi Ogawa; Kazuo Urabe

1995-01-01

312

Vanadium-molybdenum phosphates supported by TiO 2 -anatase as new catalysts for selective oxidation of ethane to acetic acid  

Microsoft Academic Search

Dispersion of vanadium and molybdenum phosphates on titanium oxide (anatase) below the monolayer gives good catalysts for direct oxidation of ethane to acetic acid. By comparison with the dispersion of only vanadium phosphate, the higher selectivity to acetic acid for vanadium and molybdenum phosphates has been explained by an interaction between molybdenum and vanadium as it can be deduced from

Magalie Roy; Michel Gubelmann-Bonneau; Hervé Ponceblanc; Jean-Claude Volta

1996-01-01

313

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

SciTech Connect

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

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

2011-10-18

314

Activation Energies for Carbon Acid/D2 Exchange Over a Solid Base Catalyst. Correlation with Gas Phase Acidities.  

National Technical Information Service (NTIS)

Thermally activated Magnesium oxide has been employed as a highly basic solid catalyst for carrying out CH/D2 exchange in hydrocarbons. A series of benzylic, aromatic, and alkane C-H bonds were studied. Reaction rates at various temperatures yielded activ...

M. Fazlul K. J. Klabunde

1988-01-01

315

Biodiesel production by free fatty acid esterification using Lanthanum (La3+) and HZSM-5 based catalysts.  

PubMed

In this work the use of the heterogeneous catalysts pure (LO) and sulfated (SLO) lanthanum oxide, pure HZSM-5 and SLO/HZSM-5 (HZSM-5 impregnated with sulfated lanthanum oxide (SO4(2-)/La2O3)) was evaluated. The structural characterization of the materials (BET) showed that the sulfation process led to a reduction of the SLO and SLO/HZSM-5 surface area values. FTIR showed bands characteristic of the materials and, FTIR-pyridine indicated the presence of strong Brønsted sites on the sulfated material. In the catalytic tests the temperature was the parameter that most influenced the reactions. The best reaction conditions were: 10% catalyst, 100°C temperature and 1:5 m(OA)/m(meOH) for LO, SLO, SLO/HZSM-5 and 10% catalyst, 100°C temperature and 1:20 m(OA)/m(meOH) for HZSM-5. Under these conditions the conversions were: 67% and 96%, for LO and SLO, respectively and 80% and 100%, for HZSM-5 and SLO/HZSM-5, respectively. All catalysts deactivated after the first use, but the deactivation of SLO/HZSM-5 was smaller. PMID:23428822

Vieira, Sara S; Magriotis, Zuy M; Santos, Nadiene A V; Saczk, Adelir A; Hori, Carla E; Arroyo, Pedro A

2013-01-29

316

[General pharmacology of T-3262, a new pyridonecarboxylic acid].  

PubMed

General pharmacological activities of (+/-)-7-(3-amino-1-pyrrolidinyl)-6-fluoro-1-(2,4-difluorophenyl)-1,4- dih ydro- 4-oxo-1,8-naphthyridine-3-carboxylic acid p-toluenesulfonate hydrate (T-3262), which is a new pyridonecarboxylic acid, were examined with the following results. 1. Central nervous system: T-3262 did not show any significant pharmacological effects at oral doses of 100-1,000 mg/kg but caused slow waves in spontaneous EEG in cats at intravenous doses of 10-30 mg/kg. 2. Respiratory and cardiovascular system: T-3262 produced little effect in normotensive rats and anesthetized rabbits at oral doses of 100-1,000 mg/kg and intravenous doses of 3-30 mg/kg, respectively. But T-3262 caused, dose-dependently, an increase of respiratory rate, hypotension, decrease of heart rate and changes in ECG patterns (elevation of T waves, slow amplitudes of QRS complexes and prolongation of RR interval, etc.) in anesthetized dogs at intravenous doses of 3-10 mg/kg. 3. Renal functions: T-3262 increased electrolyte excretions at oral doses of 300-1,000 mg/kg but did not affect PSP excretion in rats. 4. Autonomic nervous system and smooth muscle organs: T-3262 exerted slight inhibition of gastric output in rats and slight miosis in mice at an oral dose of 1,000 mg/kg. But T-3262 did not affect the contraction of nictitating membrane in anesthetized cats at intravenous doses of 1-30 mg/kg. T-3262 increased spontaneous motilities of isolated stomach, ileum and uterus, but decreased that of isolated colon at concentrations of 10(-5)-10(-4) g/ml. 5. Hematological examinations: T-3262 did not show any significant effects on bleeding time, blood coagulation, platelet aggregation and blood glucose level in rats at oral doses of 100-1,000 mg/kg. 6. Miscellaneous effects: T-3262 exerted slight inhibitions of gastric secretion and of carrageenin-induced hind paw edema in rats at a dose of 1,000 mg/kg administered intraduodenally and orally, respectively. T-3262 did not affect neuromuscular junction and bile secretion in rats at intravenous doses of 3-30 mg/kg and oral doses of 100-1,000 mg/kg, respectively. From these results, it can be assumed that T-3262 has a wide safety margin as an oral antibacterial agent. PMID:2769937

Hirai, S; Hiraiwa, T; Arai, H; Ono, S; Tanaka, K; Hashiba, K; Nakada, Y; Goden, K; Tanada, K; Maekawa, M

1989-04-01

317

Synthesis of phenoxy ethers of methyl lesquerolate over solid acid catalysts  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

318

Novel efficient mesoporous solid acid catalyst UDCaT-4: dehydration of 2-propanol and alkylation of mesitylene.  

PubMed

A novel mesoporous solid acid catalyst named UDCaT-4 was synthesized by incorporating superacidic centers of persulfated alumina and zirconia into highly ordered and well-defined hexagonal mesoporous silica. The catalyst is well characterized, and its properties are compared with those of bulk persulfated alumina and zirconia (PAZ) by FTIR spectroscopy, X-ray diffraction, Brunauer-Emmett-Teller surface area, pore size analysis, scanning electron microscopy, energy dispersive X-ray spectroscopy, and ammonia temperature-programmed desorption. UDCaT-4 is more acidic than PAZ. The dehydration processes of 2-propanol, diisopropyl ether, and n-propanol were studied independently including a mixture of n-propanol and 2-propanol to throw light on kinetics and mechanism. For alkylation of mesitylene with 2-propanol, UDCaT-4 exhibits superior catalytic activity in comparison with PAZ and also it shows remarkable stability toward coke formation. Kinetic interpretations of the observed rate data are presented for all reactions, and mechanistic models are developed. The results are novel. PMID:15595790

Yadav, Ganapati D; Murkute, Ambareesh D

2004-12-21

319

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

320

High-throughput reaction optimisation and activity screening of ferrocene-based Lewis acid-catalyst complexes by using continuous-flow reaction detection mass spectrometry.  

PubMed

Optimising synthetic conversions and assessing catalyst performance is a tedious and laborious endeavour. Herein, we present an automated alternative to the commonly applied sequential approaches that are used to increase catalyst discovery process efficiencies by increasing the number of entities that can be tested. This new approach combines conversion of the reactants and determination of product formation into a single comprehensive reaction detection system that can be operated with minimal catalyst and reactant consumption. With this approach, rudimentary reaction conditions can be quickly optimised and the same system can then be used to screen for the optimal homogenous catalyst in a selected solution-phase synthetic conversion. The system, which is composed of standard HPLC components, can be used to screen catalyst libraries at a repetition rate of five minutes and can be run unsupervised. The sensitive mass spectrometric detection that is implemented in the reaction detection methodology can be used for the simultaneous monitoring of reactants, catalysts and product ions. In the experiments, the three-component reaction that gives a substituted 2-imidazoline was optimised. Afterwards, the same method was used to assess a library of ferrocene-based Lewis acid catalysts for performance in the aforementioned conversion in six different solvents. We demonstrate the feasibility of using this methodology to directly compare the performance results obtained in different solvents by calibrating the solvent-specific MS responses. PMID:19551778

Martha, Cornelius T; Heemskerk, Anton; Hoogendoorn, Jan-Carel; Elders, Niels; Niessen, Wilfried M A; Orru, Romano V A; Irth, Hubertus

2009-07-27

321

Decomposition of oxalic acid on solid-phase catalysts in nitric acid solutions in the presence of hydrazine  

SciTech Connect

Decomposition of N{sub 2}H{sub 4} and H{sub 2}C{sub 2}O{sub 4} has been studied by titrimetric method in HNO{sub 3} solutions in the presence of Pt/SiO{sub 2} catalyst and BAU activated carbon. Under static conditions, the rate of N{sub 2}H{sub 4} decomposition in the presence of Pt/SiO{sub 2} increases monotonically with increasing temperature, Pt content, and amount of catalyst per unit volume of the solution. With increasing HNO{sub 3} concentration from 0.2 to 7 M, the N{sub 2}H{sub 4} decomposition rate peaks at 1-2 M. Decomposition of H{sub 2}C{sub 2}O{sub 4} begins only after N{sub 2}H{sub 4} is almost completely decomposed. When passing a mixture of H{sub 2}C{sub 2}O{sub 4} with N{sub 2}H{sub 4}through a column packed with catalyst, decomposition of H{sub 2}C{sub 2}O{sub 4} begins before complete disappearence of N{sub 2}H{sub 4}.

Krot, N.N.; Shilov, V.P.; Dzyubenko, V.I. [Institute of Physical Chemistry, Moscow (Russian Federation)] [and others

1995-01-01

322

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

Microsoft Academic Search

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

Khodabakhsh Niknam; Dariush Saberi

2009-01-01

323

Synthesis of fatty acid methyl ester from palm oil (Elaeis guineensis) with Ky(MgCa)2xO3 as heterogeneous catalyst.  

PubMed

Fatty acid methyl esters (FAME) were produced from palm oil using eggshell modified with magnesium and potassium nitrates to form a composite, low-cost heterogeneous catalyst for transesterification. The catalyst, prepared by the combination of impregnation/co-precipitation was calcined at 830 °C for 4 h. Transesterification was conducted at a constant temperature of 65 °C in a batch reactor. Design of experiment (DOE) was used to optimize the reaction parameters, and the conditions that gave highest yield of FAME (85.8%) was 5.35 wt.% catalyst loading at 4.5 h with 16:1 methanol/oil molar ratio. The results revealed that eggshell, a solid waste, can be utilized as low-cost catalyst after modification with magnesium and potassium nitrates for biodiesel production. PMID:21983406

Olutoye, M A; Lee, S C; Hameed, B H

2011-09-16

324

Pt-Ag catalysts as cathode material for oxygen-depolarized electrodes in hydrochloric acid electrolysis.  

PubMed

Pt-Ag nanoparticles were prepared on a glassy carbon (GC) surface by pulsed electrodeposition and tested using cyclic voltammetry and scanning electrochemical microscopy (SECM) with respect to their possible use as catalyst material for oxygen reduction in 400 mM HCl solution. For comparison, a Pt catalyst was investigated under similar conditions. The redox competition mode of scanning electrochemical microscopy (RC-SECM) was adapted to the specific conditions caused by the presence of Cl(-) ions and used to visualize the local catalytic activity of the Pt-Ag deposits. Similarly prepared Pt deposits were shown to dissolve underneath the SECM tip. Pt-Ag composites showed improved long-term stability toward oxygen reduction as compared with Pt even under multiple switching off to open-circuit potential in 400 mM HCl. PMID:20146448

Maljusch, Artjom; Nagaiah, Tharamani Chikka; Schwamborn, Stefanie; Bron, Michael; Schuhmann, Wolfgang

2010-03-01

325

Design and Performance of Rigid Nanosize Multimetallic Cartwheel Pincer Compounds as Lewis-Acid Catalysts  

Microsoft Academic Search

Novel strategies for the preparation of rigid cartwheel pincer metal complexes have been developed. The aromatic backbone of these materials ensures a high rigidity, which is expected to be important for a high retention when these multimetallic nanosize complexes are applied as homogeneous catalysts in a nanomembrane reactor. The ligand precursors C6[C6H3(CH2Y)2-3,5]6 (10, Y = NMe2; 11, Y = SPh;

G. van Koten; H. P. Dijkstra; M. D. Meijer; J. Patel; R. Kreiter; G. P. M. van Klink; M. H. Lutz; A. L. Spek; A. J. Canty

2001-01-01

326

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

Microsoft Academic Search

The understanding of the electrocatalytic activity of bimetallic nanoparticle catalysts requires the ability to precisely control the composition and phase properties. In this report, we describe a new strategy in the preparation of a series of carbon supported platinum–gold bimetallic nanoparticles with various bimetallic compositions which were loaded onto a carbon black support and subjected subsequently by thermal treatment (Pt100?mAum\\/C).

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

327

pH effects on catalytic ozonation of carboxylic acids with metal on metal oxides catalysts  

Microsoft Academic Search

Summary The pH influence on the catalytic ozonation of small carboxylic acids (succinic (SA), chloroacetic (CAA) and pyruvic (PA) acids) was studied and compared to ozonation alone. In the acidic systems, the conversion of these carboxylic acids and total organic carbon (TOC) during the catalytic ozonation is mainly due to the catalytic effect. Experiments on SA indicate that in the

Nathalie Karpel Vel Leitner; Hongxiang Fu

2005-01-01

328

General and selective C-3 alkylation of indoles with primary alcohols by a reusable pt nanocluster catalyst.  

PubMed

The platinum rule: Heterogeneous, additive-free C-3 selective alkylation of indoles by aliphatic and aromatic alcohols proceeded under transfer hydrogenation conditions with the reusable Pt/?-Al2 O3 catalyst (see scheme; TON=turnover number). PMID:24127322

Siddiki, S M A Hakim; Kon, Kenichi; Shimizu, Ken-Ichi

2013-09-20

329

Preparation and characterization of mesoporous N-doped and sulfuric acid treated anatase TiO2 catalysts and their photocatalytic activity under UV and Vis illumination  

NASA Astrophysics Data System (ADS)

Nitrogen-doped TiO2 catalysts were prepared by a precipitation method. The samples were calcined at 400 °C for 4 h in air. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), low temperature N2-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 (aBETS) 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 (?g,1=˜390 nm, ?g,2=˜510 nm). It was also established that surface treatment enhances the Vis-light absorption of the N-TiO2 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 TiO2 samples were more catalytically active than non-doped TiO2 catalysts.

Kun, Robert; Tarján, Sándor; Oszkó, Albert; Seemann, Torben; Zöllmer, Volker; Busse, Matthias; Dékány, Imre

2009-11-01

330

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

331

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

SciTech Connect

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

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

1992-09-01

332

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

2013-02-26

333

Design of novel catalyst imbedding heteropoly acids in polymer films: Catalytic activity for ethanol conversion  

Microsoft Academic Search

Membrane-like H3PMo12O40 or H5PMo10V2O40-imbedded polymer films were prepared by blending these materials using a chloroform-methanol mixture as solvent, and they were tested as catalysts for the ethanol conversion reaction in a continuous flow fixed-bed reactor. It was found that the chloroform-methanol mixture itself gave no influence on the catalytic activity of bulk H3PMo12O40 and H5PMo10V2O40. Polysulfone, polyethersulfone and polyphenylene oxide

Jong Koog Lee; In Kyu Song; Wha Young Lee

1997-01-01

334

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

335

Catalytic oxidation of acrolein to acrylic acid over a molybdenum-vanadium catalyst  

Microsoft Academic Search

By the method of gas chromatography it has been found that the adsorption of acrolein takes place without dissociation whereas acrylic acid is adsorbed dissociatively. The adsorption of water vapor proceeds also dissociatively and results in increasing the number of the Brönsted acid centers. The presence of water vapor has a positive effect on the desorption rate of acrylic acid

J. Tichý; J. Švachula; J. Machek; N. Ch. Allachverdova

1986-01-01

336

The reaction mechanism of C{sub 6} hydrocarbons over acid-base bifunctional catalysts, TiO{sub 2}-ZrO{sub 2}  

SciTech Connect

This study examined the relation between the acid-base properties of a binary oxide, TiO{sub 2}-ZrO{sub 2}, and the reaction behavior of various C{sub 6} hydrocarbons over this mixed oxide. Based on experimental results, both the strong acid sites and the strong base sites performed as cracking sites and could be poisoned by doping a small amount of K{sub 2}O and B{sub 2}O{sub 3}, respectively. It was demonstrated that the paired acid-base sites played most important roles on dehydrogenation of cyclohexane and cyclization of n-hexane and hexene. Both the yield and selectivity of benzene increased with the relative paired acid-base amount. The results of isomerization of 1-hexene showed that the yield of the molecular isomerization increased at the expense of the double bond migration as the relative acid/base ratio increased. The results also showed that 2-hexene had a much higher aromatization rate than 1-hexene over TiO{sub 2}-ZrO{sub 2} catalysts. A detailed reaction mechanism of the aromatization C{sub 6} hydrocarbons over an acid-base bifunctional catalyst is proposed, which was different from the mechanism of a conventional metal-acid bifunctional catalysts. 15 refs., 9 figs., 5 tabs.

Jingly Fung; Ikai Wang [National Tsing Hua Univ., Hsinchu (Taiwan, Province of China)

1996-11-01

337

MCM-41 anchored sulfonic acid (MCM-41-R-SO 3H): A mild, reusable and highly efficient heterogeneous catalyst for the Biginelli reaction  

Microsoft Academic Search

An efficient three-component synthesis of 3,4-dihydropyrimidinones using MCM-41 anchored sulfonic acid (MCM-41-R-SO3H) as a mild, heterogeneous catalyst for Biginelli reaction in CH3CN under reflux condition is described.

Gholam Hossein Mahdavinia; Hamid Sepehrian

2008-01-01

338

Influence of the acid–base properties of solid catalysts derived from hydrotalcite-like compounds on the condensation of formaldehyde and acetaldehyde  

Microsoft Academic Search

The vapor-phase aldol condensation of formaldehyde with acetaldehyde was studied using various oxide mixtures obtained in situ from hydrotalcite-like materials as catalysts. All samples exhibited catalytic activity, but the selectivity to both the aldol condensation and the acrolein formation is governed by the balance of acidic and basic properties. The oxides containing Mg and Al or Co and Al showed

Emil Dumitriu; Vasile Hulea; Carmen Chelaru; Cezar Catrinescu; Didier Tichit; Robert Durand

1999-01-01

339

An efficient, rapid and regioselective nuclear bromination of aromatics and heteroaromatics with NBS using sulfonic-acid-functionalized silica as a heterogeneous recyclable catalyst  

Microsoft Academic Search

A simple, efficient and rapid method has been developed for high-yielding regioselective nuclear monobromination of aromatic and heteroaromatic compounds using NBS in the presence of sulfonic-acid-functionalized silica at room temperature. The catalyst works under heterogeneous conditions and can be recycled.

Biswanath Das; Katta Venkateswarlu; Maddeboina Krishnaiah; Harish Holla

2006-01-01

340

Sulfamic acid: a novel and efficient catalyst for the synthesis of aryl-14 H-dibenzo[ a. j]xanthenes under conventional heating and microwave irradiation  

Microsoft Academic Search

A simple and convenient procedure for the synthesis of aryl-14H-dibenzo[a.j]xanthenes is described through a one-pot condensation of ?-naphthol with aryl aldehydes in the presence of sulfamic acid as the catalyst in a solvent-free media using both conventional heating and microwave irradiation.

B. Rajitha; B. Sunil Kumar; Y. Thirupathi Reddy; P. Narsimha Reddy; N. Sreenivasulu

2005-01-01

341

Sulfamic acid as a cost-effective and recyclable catalyst for liquid Beckmann rearrangement, a green process to produce amides from ketoximes without waste  

Microsoft Academic Search

Sulfamic acid (H2NSO3H) has been proved to be an efficient and green catalyst for liquid Beckmann rearrangement of ketoxime in dried acetonitrile. The use of basic neutralization agent has been avoided in this system due to its intrinsic zwitterionic property. Thus it is a green process for preparation of amide from ketoxime without producing any waste.

Bo Wang; Yanlong Gu; Cheng Luo; Tao Yang; Liming Yang; Jishuan Suo

2004-01-01

342

Catalyst-Free and Site-Specific One-Pot Dual Labeling of a Protein Directed by Two Genetically Incorporated Noncanonical Amino Acids  

PubMed Central

The genetic incorporation of one azide-containing and one keto-containing noncanonical amino acids into a protein at one amber and one ochre mutation sites respectively followed by their orthogonal reactions with one hydroxylamine-containing and one cyclooctyne-containing dyes allows highly efficient one-pot site-specific dual labeling of the protein in a catalyst-free fashion.

Wu, Bo; Wang, Zhiyong; Huang, Ying; Liu, Wenshe R.

2012-01-01

343

Tandem decarboxylative hydroformylation-hydrogenation reaction of ?,?-unsaturated carboxylic acids toward aliphatic alcohols under mild conditions employing a supramolecular catalyst system.  

PubMed

A new atom economic catalytic method for a highly chemoselective reduction of ?,?-unsaturated carboxylic acids to the corresponding saturated alcohols under mild reaction conditions, compatible with a wide range reactive functional groups, is reported. The new methodology consists of a novel tandem decarboxylative hydroformylation/aldehyde reduction sequence employing a unique supramolecular catalyst system. PMID:24022335

Diab, Lisa; Gellrich, Urs; Breit, Bernhard

2013-09-26

344

Building Blocks for Polyamide Nucleic Acids: Facile Synthesis Using Potassium Fluoride Doped Natural Phosphate as Basic Catalyst  

Microsoft Academic Search

Potassium fluoride doped natural phosphate, inexpensive and environmentally friendly catalyst, is shown to be an efficient basic catalyst for the N1\\/N9 alkylation of different nucleobases as synthons for PNAs.

A. Alahiane; M. Taourirte; A. Rochdi; N. Redwane; S. Sebti; J. W. Engels; H. B. Lazrek

2003-01-01

345

Effect of carbon support properties on enantioselective hydrogenation of isophorone over palladium catalysts modified with (?)-dihydroapovincaminic acid ethyl ester  

Microsoft Academic Search

The support-effect was investigated in the enantioselective hydrogenation of isophorone over Pd catalysts prepared on different carbon supports. Carbon supports with different specific surface area and activated carbons with different surface chemistry were used. The Pd catalysts, obtained by different reduction methods of the catalyst precursor, had different dispersion. The low dispersion was advantageous for the high enantioselectivity and the

Gabriella Farkas; László Heged?s; Antal Tungler; Tibor Máthé; José Lu??s Figueiredo; Magdalena Freitas

2000-01-01

346

A Sulfated ZrO2 Hollow Nanostructure as an Acid Catalyst in the Dehydration of Fructose to 5-Hydroxymethylfurfural.  

PubMed

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

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

2013-09-10

347

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

Microsoft Academic Search

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

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

2008-01-01

348

kinetics of the oxidation of b-picoline to nicotinic acid over vanadia-titania catalyst, 1. The network of the reaction and the effect of water  

Microsoft Academic Search

Over vanadia-titania catalysts, the oxidation of ?-picoline into nicotinic acid proceeds under a parallel-consecutive network.\\u000a Nicotinic acid is formed both directly from picoline and through pyridine-3-carbaldehyde as an intermediate. Products of total\\u000a oxidation and nitrile are formed on a parallel path from picoline, and on a consecutive path via overoxidation of partial\\u000a oxidation products. Introduction of water into the reaction

E. V. Ovchinnikova; T. V. Andrushkevich; L. A. Shadrina

2004-01-01

349

Chemical–physical characterization of Fe-doped, Keggin-type P\\/Mo polyoxometalates, catalysts for the selective oxidation of isobutane to methacrylic acid  

Microsoft Academic Search

Iron-doped, ammonium\\/potassium salts of 12-molybdophosphoric acid (Keggin-type polyoxometalates (POMs)) were prepared, characterized and tested as catalysts for the selective oxidation of isobutane to methacrylic acid. In samples calcined at 623K, iron was incorporated in the secondary framework of the polyoxometalate, replacing for ammonium up to a maximum amount of ?0.35 Fe atoms per Keggin unit. Iron was present as a

E Etienne; F Cavani; R Mezzogori; F Trifirò; G Calestani; L Gengembre; M Guelton

2003-01-01

350

Improved catalytic performance of Keggin-type polyoxometalates in the oxidation of isobutane to methacrylic acid under hydrocarbon-lean conditions using antimony-doped catalysts  

Microsoft Academic Search

Ammonium salt of 12-molybdophosphoric acid (NH4)3PMo12O40, having the Keggin structure (polyoxometalate, POM) was prepared and tested as heterogeneous catalyst for the selective oxidation of isobutane to methacrylic acid, under both hydrocarbon-rich and hydrocarbon-lean conditions. The same compound was doped with Sb3+ ions, in an amount corresponding to 0.23 Sb atom per Keggin unit. Doping with antimony caused a decrease in

F. Cavani; R. Mezzogori; A. Pigamo; F. Trifirò

2001-01-01

351

Effects of structural defects and acid–basic properties on the activity and selectivity of isopropanol decomposition on nanocrystallite sol–gel alumina catalyst  

Microsoft Academic Search

The surface acid–basic properties of sol–gel alumina catalysts were studied by Fourier transform infrared (FTIR) spectroscopy of pyridine adsorption and temperature-programmed desorption of CO2 and NH3. The number of acid and basic sites on the samples varied with the calcination temperatures of the samples. The populations of the three different aluminum ions—tetrahedral, pentacoordinated and octahedral, which were identified by the

J. A. Wang; X. Bokhimi; O. Novaro; T. López; F. Tzompantzi; R. Gómez; J. Navarrete; M. E. Llanos; E. López-Salinas

1999-01-01

352

Surface characterization and catalytic activity of sulfate-, molybdate- and tungstate-promoted Al 2O 3–ZrO 2 solid acid catalysts  

Microsoft Academic Search

Alumina–zirconia mixed oxide-supported sulfate-, molybdate- and tungstate-promoted solid acid catalysts were synthesized and characterized by various techniques. The Al–Zr hydroxide gel was obtained by a co-precipitation method from their corresponding nitrate salts by hydrolysis with aqueous ammonia. To the Al–Zr-hydrous mixed oxide support, aqueous solutions of sulfuric acid, ammonium heptamolybdate and ammonium metatungstate were added and the mixtures were refluxed

Benjaram M. Reddy; Pavani M. Sreekanth; Yusuke Yamada; Tetsuhiko Kobayashi

2005-01-01

353

Mineralization of clofibric acid by electrochemical advanced oxidation processes using a boron-doped diamond anode and Fe 2+ and UVA light as catalysts  

Microsoft Academic Search

This work shows that aqueous solutions of clofibric acid (2-(4-chlorophenoxy)-2-methylpropionic acid), the bioactive metabolite of various lipid-regulating drugs, up to saturation at pH 3.0 are efficiently and completely degraded by electrochemical advanced oxidation processes such as electro-Fenton and photoelectro-Fenton with Fe2+ and UVA light as catalysts using an undivided electrolytic cell with a boron-doped diamond (BDD) anode and an O2-diffusion

Ignasi Sirés; Francesc Centellas; José Antonio Garrido; Rosa María Rodríguez; Conchita Arias; Pere-Lluís Cabot; Enric Brillas

2007-01-01

354

Surface characterization of sulfate, molybdate, and tungstate promoted TiO 2-ZrO 2 solid acid catalysts by XPS and other techniques  

Microsoft Academic Search

Titania–zirconia binary oxide supported sulfate, molybdate, and tungstate promoted solid acid catalysts were prepared by suspending the hydrous mixed oxide support in aqueous solutions of sulfuric acid, ammonium heptamolybdate, and ammonium metatungstate. The suspensions were refluxed at 383K followed by evaporation of the water, drying and calcination at 1073K. The resulting materials were characterized by means of X-ray powder diffraction,

Benjaram M Reddy; Pavani M Sreekanth; Yusuke Yamada; Qiang Xu; Tetsuhiko Kobayashi

2002-01-01

355

In situ FTIR study of the kinetics of formic acid decomposition on V–Ti oxide catalyst under stationary and non-stationary conditions. Determination of kinetic constants  

Microsoft Academic Search

Decomposition of formic acid over V–Ti oxide catalyst under stationary and non-stationary conditions was studied by in situ IR spectroscopy at temperature range 50–150°C. The kinetic scheme was shown to include the steps of reverse adsorption of formic acid and formate decomposition to CO. The rate constants and activation energies were estimated according to the proposed kinetic model. The kinetic

E. A. Ivanov; G. Ya. Popova; Yu. A. Chesalov; T. V. Andrushkevich

2009-01-01

356

Direct oxidation of L-sorbose to 2-keto-L-gulonic acid with molecular oxygen on platinum- and palladium-based catalysts  

SciTech Connect

The selective oxidation of the C1 hydroxyl group of L-sorbose to a carboxylic group without protection of the four other hydroxyl functions was investigated. The reactions were performed in slightly alkaline aqueous solutions with molecular oxygen over various alumina- and carbon-supported Pt and Pd catalysts. Optimum reaction conditions were 50{degrees}C, pH 7.3, and a catalyst:reactant ratio of 1:4 (wt/wt). The lower the pH and the temperature, the higher the selectivity toward 2-keto-L-gluonic acid. Catalyst deactivation was also found to increase with lower pH and temperature. A 5 wt% Pt/alumina catalyst showed the best catalytic performance (67% selectivity at 58% conversion). Promotion with Bi or Pb had a detrimental effect on selectivity for 2-keto-L-gulonic acid. Electrochemical measurements indicated that the reaction occurs in a rather narrow potential range, which corresponds to a moderate oxygen coverage of Pt or Pd. Four types of catalyst deactivation processes were identified, based on XPS and ICP-AES analysis and on the in situ determination of the oxidation state by monitoring the catalyst potential during reaction. A significant chemical poisoning of the active noble metal sites occurred during the initial, destructive adsorption of L-sorbose and during the oxidation reaction. The successive contamination of active sites resulted in overoxidation (too high oxygen coverage of Pt or Pd). The partially oxidized promoters and noble metals were corroded and dissolved in the presence of 2-keto-L-gulonic acid, resulting in an irreversible deactivation. 66 refs., 11 figs., 2 tabs.

Broennimann, C.; Bodnar, Z.; Mallat, T.; Baiker, A. [Swiss Federal Institute of Technology, Zuerich (Switzerland); Hug, P. [Univ. of Zuerich (Switzerland)

1994-11-01

357

Niobium oxide based materials as catalysts for acidic and partial oxidation type reactions  

Microsoft Academic Search

Niobic acid, H8Nb6O19·xH2O, was synthesized and studied for its acidic features as a function of its dehydroxylation extent. It was observed to be strongly acidic, using NH3 adsorption calorimetry and isopropanol conversion reaction as probe techniques, and to be weakly acidic on its dehydrated form, Nb2O5. The mixed oxide Al2o3:Nb2o5in 1:1 molar ratio prepared from aluminum and niobium oxalates was

J. C. Védrine; G. Coudurier; A. Ouqour; P. G. Pries de Oliveira; J. C. Volta

1996-01-01

358

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

Microsoft Academic Search

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

Kazu Okumura; Katsuhiko Yamashita; Kazuhiro Yamada; Miki Niwa

2007-01-01

359

The generation of acid sites on the surfaces of binary metal oxide catalysts  

SciTech Connect

The generation of acid sites by the addition of dopant cations to the surfaces of metal oxides was studied through the use of pyridine adsorption, combined with gravimetric measurements, infrared spectroscopy and Mossbauer spectroscopy. Lewis acid sites were shown to be coordinately unsaturated cations on the surface. The existence of these Lewis acid sites can be estimated based on the coordination of the cations. The strength of the sites can be estimated using the electronegativity of the cations. The existence of Bronsted acid sites was shown to occur in special cases where a bridging hydroxyl group exists between two different cations on the surface. The existence of the Bronsted acid sites can be predicted with the bonding geometry and surface structure.

Connell, G.; Dumesic, J.A.

1986-01-01

360

Zn(1.2)H(0.6)PW(12)O(40) Nanotubes with double acid sites as heterogeneous catalysts for the production of biodiesel from waste cooking oil.  

PubMed

Out of the frying pan: A ZnPW nanotube catalyst containing Brønsted and Lewis double acid sites promotes the conversion of waste cooking oil into biodiesel. The catalytic activity of the ZnPW nanotubes is stable to the presence of free fatty acids or water in the feedstock. The high catalytic activity of the ZnPW nanotubes is attributed to the synergistic effect of Lewis acid sites and Brønsted acid sites.Zinc dodecatungstophosphate (Zn(1.2)H(0.6)PW(12)O(40); ZnPW) nanotubes, which feature Lewis acid and Brønsted acid sites, were prepared using cellulose fibers as templates. The structure, acid properties, and catalytic activity of the nanotubes as heterogeneous catalysts for biodiesel production were then studied in detail. The ZnPW nanocatalyst exhibited higher catalytic activities for the simultaneous esterification and transesterification of palmitic acid than the parent acid catalyst 12-tungstophosphoric acid (H(3)PW(12)O(40)). Moreover, the doubly acidic nanotubes led to markedly enhanced yields of methyl esters in the conversion of waste cooking oil (containing 26.89 wt % free fatty acids and 1 % moisture) to biodiesel. The catalyst could be recycled and reused with negligible loss in activity over five cycles. The ZnPW nanocatalyst is acid- and water-tolerant and is an environmentally benign heterogeneous catalyst for the production of biodiesel from low-quality feedstocks. PMID:19191363

Li, Jing; Wang, Xiaohong; Zhu, Weimin; Cao, Fenghua

2009-01-01

361

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

Microsoft Academic Search

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

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

1996-01-01

362

One-pot bio-synthesis: N-acetyl-d-neuraminic acid production by a powerful engineered whole-cell catalyst  

PubMed Central

Whole cell biocatalysis is an important tool for pharmaceutical intermediates synthesis, although it is hindered by some shortcomings, such as high cost and toxicity of inducer, mass transfer resistance caused by cell membrane and side reactions. Whole-cell catalysis using N-acetyl-d-glucosamine 2-epimerase (EC 5.1.3.8) and N-acetyl-d-neuraminic acid (Neu5Ac) aldolase (EC 4.1.3.3) is a promising approach for the production of Neu5Ac, a potential precursor of many anti-viral drugs. A powerful catalyst was developed by packaging the enzymes in an engineered bacterium and using a safe temperature-induced vector. Since the mass transfer resistance and the side reactions were substantially reduced, a high Neu5Ac amount (191?mM) was achieved. An efficient method was also presented, which allows one-pot synthesis of Neu5Ac with a safe and economic manner. The results highlight the promise of large-scale Neu5Ac synthesis and point at a potential of our approach as a general strategy to improve whole-cell biocatalysis.

Tao, Fei; Zhang, Yinan; Ma, Cuiqing; Xu, Ping

2011-01-01

363

Process of making supported catalyst  

DOEpatents

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

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

1992-01-01

364

Development of Ternary Alloy Cathode Catalysts for Phosphoric Acid Fuel Cells: Final Report.  

National Technical Information Service (NTIS)

The overall objective of the program was the identification development and incorporation of high activity platinum ternary alloys on corrosion resistant supports, for use in advanced phosphoric acid fuel cells. Two high activity ternary alloys, Pt-Cr-Ce ...

1988-01-01

365

Preparation and Evaluation of Advanced Catalysts for Phosphoric Acid Fuel Cells.  

National Technical Information Service (NTIS)

The platinum electrocatalysts were characterized for their crystallite sizes and the degree of dispersion on the carbon supports. One application of these electrocatalysts was for anodic oxidation of hydrogen in hot phosphoric acid fuel cells, coupled wit...

P. Stonehart J. Baris J. Hockmuth P. Pagliaro

1984-01-01

366

Biological role of the general control of amino acid biosynthesis in Saccharomyces cerevisiae.  

PubMed

The biological role of the "general control of amino acid biosynthesis" has been investigated by analyzing growth and enzyme levels in wild-type, bradytrophic, and nonderepressing mutant strains of Saccharomyces cerevisiae. Amino acid limitation was achieved by using either bradytrophic mutations or external amino acid imbalance. In the wild-type strain noncoordinate derepression of enzymes subject to the general control has been found. Derepressing factors were in the order of 2 to 4 in bradytrophic mutant strains grown under limiting conditions and only in the order of 1.5 to 2 under the influence of external amino acid imbalance. Nonderepressing mutations led to slower growth rates under conditions of amino acid limitation, and no derepression of enzymes under the general control was observed. The amino acid pools were found to be very similar in the wild type and in nonderepressing mutant strains under all conditions tested. Our results indicate that the general control affects all branched amino acid biosynthetic pathways, namely, those of the aromatic amino acids and the aspartate family, the pathways for the basic amino acids lysine, histidine, and arginine, and also the pathways of serine and valine biosyntheses. PMID:9279372

Niederberger, P; Miozzari, G; Hütter, R

1981-07-01

367

Biological role of the general control of amino acid biosynthesis in Saccharomyces cerevisiae.  

PubMed Central

The biological role of the "general control of amino acid biosynthesis" has been investigated by analyzing growth and enzyme levels in wild-type, bradytrophic, and nonderepressing mutant strains of Saccharomyces cerevisiae. Amino acid limitation was achieved by using either bradytrophic mutations or external amino acid imbalance. In the wild-type strain noncoordinate derepression of enzymes subject to the general control has been found. Derepressing factors were in the order of 2 to 4 in bradytrophic mutant strains grown under limiting conditions and only in the order of 1.5 to 2 under the influence of external amino acid imbalance. Nonderepressing mutations led to slower growth rates under conditions of amino acid limitation, and no derepression of enzymes under the general control was observed. The amino acid pools were found to be very similar in the wild type and in nonderepressing mutant strains under all conditions tested. Our results indicate that the general control affects all branched amino acid biosynthetic pathways, namely, those of the aromatic amino acids and the aspartate family, the pathways for the basic amino acids lysine, histidine, and arginine, and also the pathways of serine and valine biosyntheses.

Niederberger, P; Miozzari, G; Hutter, R

1981-01-01

368

Physical methods of nucleic acid transfer: general concepts and applications  

PubMed Central

Physical methods of gene (and/or drug) transfer need to combine two effects to deliver the therapeutic material into cells. The physical methods must induce reversible alterations in the plasma membrane to allow the direct passage of the molecules of interest into the cell cytosol. They must also bring the nucleic acids in contact with the permeabilized plasma membrane or facilitate access to the inside of the cell. These two effects can be achieved in one or more steps, depending upon the methods employed. In this review, we describe and compare several physical methods: biolistics, jet injection, hydrodynamic injection, ultrasound, magnetic field and electric pulse mediated gene transfer. We describe the physical mechanisms underlying these approaches and discuss the advantages and limitations of each approach as well as its potential application in research or in preclinical and clinical trials. We also provide conclusions, comparisons, and projections for future developments. While some of these methods are already in use in man, some are still under development or are used only within clinical trials for gene transfer. The possibilities offered by these methods are, however, not restricted to the transfer of genes and the complementary uses of these technologies are also discussed. As these methods of gene transfer may bypass some of the side effects linked to viral or biochemical approaches, they may find their place in specific clinical applications in the future. This article is part of a themed section on Vector Design and Drug Delivery. For a list of all articles in this section see the end of this paper, or visit: http://www3.interscience.wiley.com/journal/121548564/issueyear?year=2009

Villemejane, Julien; Mir, Lluis M

2009-01-01

369

Organosilanesulfonic acid-functionalized Zr-TMS catalysts: Synthesis, characterization and catalytic applications in condensation reactions  

Microsoft Academic Search

Organosilanesulfonic acid (–Si–R3S–R4SO3H, OSA)-functionalized mesoporous Zr-TMS (Zr-TMS–Si–R3S–R4SO3H, Zr-TMS–OSA) was synthesized either by post-synthetic modification of Zr-TMS (zirconia-based transition metal oxide mesoporous molecular sieves) with 3-mercaptopropyltrimethoxysilane (3-MPTS) and further with 1,4-butanesultone (1,4-BS) or by in situ one-pot synthesis procedure. A number of physico-chemical characterization techniques have been used to show that the organosilanesulfonic acid groups were anchored on to the walls

M. Chidambaram; C. Venkatesan; A. P. Singh

2006-01-01

370

Niobium, catalyst repair kit  

SciTech Connect

This paper reports that niobium oxides, when small amounts are added to known catalysts, enhance catalytic activity and selectivity and prolong catalyst life. Moreover, niobium oxides exhibit a pronounced effect as supports of metal or metal oxide catalysts. Recently we found that the surface acidity of hydrated niobium pentoxide, niobic acid (Nb{sub 2}O{sub 5} {center dot} nH{sub 2}O), corresponds to the acidity of 70% sulfuric acid and exhibits high catalytic activity, selectivity, and stability for acid-catalyzed reactions in which water molecules participate. Although there are few differences in electronegativity and ionic radius between niobium and its neighbors in the periodic table, it is interesting that the promoter effect, support effect, and acidic nature of niobium compounds are quite different from those of compounds of the surrounding elements. Here we review what's known of niobium compounds from the viewpoint of their pronounced catalytic behavior.

Tanabe, K.

1991-10-01

371

Selective Oxidation of Isobutane to Methacrylic Acid over Supported V-Mo-P Based Composite Oxide Catalysts  

Microsoft Academic Search

Heteropolyacid, the most popular catalyst for the direct oxidation of isobutane, exhibits high catalytic activity, poor thermal stability and a short lifetime. Therefore, the catalyst requires further research to improve its performance. Catalysts composed of mixed oxides (V2O5, P2O5, or MoO3) sup- ported on silica were prepared by the sol-gel method to catalyze the reaction. Results of XRD, IR, and

Feifei Sun; Yunfeng Geng; Shunhe Zhong

372

Sulfated Ce x Zr 1? x O 2 solid acid catalyst for solvent free synthesis of coumarins  

Microsoft Academic Search

A novel SO42?\\/CexZr1?xO2 catalyst has been employed for Pechmann condensation of phenols under solvent-free conditions. Catalyst loads as low as 10wt.% could be used leading to high yields with activated phenols at an oil bath temperature of 393K. To make the catalyst, Ce–Zr–hydroxide gel was prepared by a coprecipitation method and SO42? ions were deposited by treating the gel with

Benjaram M. Reddy; Meghshyam K. Patil; Pandian Lakshmanan

2006-01-01

373

Hydrogenation of Vegetable Oils with Minimum trans and Saturated Fatty Acid Formation Over a New Generation of Pd-catalyst  

Microsoft Academic Search

Hydrogenation of sunflower and canola oils over a novel Pd-supported catalyst (pore size of 6.8 nm and BET specific surface\\u000a area of 837 m2\\/g) was investigated and compared to commercial nickel catalyst. The formulated catalyst with Pd-loading of 1 wt%, supported\\u000a on structured silica material was active and selective for the hydrogenation of sunflower and canola oils under mild process\\u000a conditions. For both

Khaled Belkacemi; Amira Boulmerka; Joseph Arul; Safia Hamoudi

2006-01-01

374

Fatty-acid-modified enzymes as enantioselective catalysts in microaqueous organic media  

Microsoft Academic Search

Highly active lipase and protease complexes were prepared by non-covalent modification with stearic acid. The protein content and yield of the modified enzyme complexes depended on the enzymes' source. The increase in the transesterification activity of the modified enzymes was 15 fold for Candida rugosa lipase and porcine pancreatic lipase, with preservation of the enantioselectivity. Pseudomonas sp. lipase which showed

Ayelet Fishman; Sobhi Basheer; Shimon Shatzmiller; Uri Cogan

1998-01-01

375

Ionic liquid-regulated sulfamic acid: chemoselective catalyst for the transesterification of ?-ketoesters  

Microsoft Academic Search

1-Propyl-3-methylimidazolium chloride ([C3MIm]Cl) ionic liquid and sulfamic acid (NH2SO3H), as a synergetic catalytic medium, were used for the transesterification of acetoacetate with alcohols of different structures. It shows the good ability for the chemoselective transesterificatin of ?-ketoesters and maintains its catalytic activity in the reuse.

Wang Bo; Yang Li Ming; Suo Ji Shuan

2003-01-01

376

Formic Acid Dehydrogenation on Au-Based Catalysts at Near-Ambient Temperatures  

Microsoft Academic Search

Formic acid (HCOOH) is a convenient hydrogen carrier in fuel cells designed for portable use. Recent studies have shown that HCOOH decomposition is catalyzed with Ru-based complexes in the aqueous phase at near-ambient temperatures. HCOOH decomposition reactions are used frequently to probe the effects of alloying and cluster size and of geometric and electronic factors in catalysis. These studies have

Manuel Ojeda; Enrique Iglesia

2008-01-01

377

General Acid Catalysis: A Flexible Experiment, Adaptable to Student Ability and Various Teaching Approaches.  

ERIC Educational Resources Information Center

|The acid-catalyzed hydrolysis of N-vinyl pyrrolidone provides a simple spectrophotometric kinetic experiment to introduce general acid catalysis, solvent isotope effects, and other aspects of ionic reactions in solution in advanced courses. The Bronsted equation and concept of linear free-energy changes is also covered. (SK)|

Bulmer, R. S.; And Others

1981-01-01

378

H-gallosilicate (MFI) propane aromatization catalyst: Influence of Si/Ga ratio on acidity, activity and deactivation due to coking  

SciTech Connect

Influence of bulk Si/Ga ratio of H-gallosilicate (MFI) on its degalliation (during calcination for removal of template and deammoniation of NH{sub 4} form), acidity/acid strength distribution (measured by stepwise thermal desorption and chemisorption of pyridine at 50-400{degrees}C using GC techniques and also by acid catalyzed model reactions viz. iso-octane cracking and toluene disproportionation) and initial activity/product selectivity and catalyst deactivation in propane aromatization (at 550{degrees}C) has been investigated. Framework Si/Ga ratio was measured by {sup 29}Si MAS NMR. Information on the external acid sites is obtained by isooctane cracking. The influence of poisoning of strong acid sites (by pyridine) on acid catalyzed model reactions and the effect of deactivation on the product distribution in the propane aromatization have also been studied. 21 refs., 19 figs., 3 tabs.

Choudhary, V.R.; Kinage, A.K.; Sivadinarayana, C. [National Chemical Lab., Pune (India)] [and others

1996-01-01

379

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

Microsoft Academic Search

The increase in the residue content resulting from polycondensation would be adverse to the utilization of lignocellulose\\u000a and to the quality of products obtained from liquefied lignocellulosic material. The yield of the residue formed from liquefaction\\u000a and the mechanism of polycondensation were reported mainly by Lin, Yamada and Kobayashi. The major products of cellulosic\\u000a liquefaction are levulinic acid and hydroxymethylfurfural

Min Niu; Guang-jie Zhao; Mehmet Hakki Alma

2011-01-01

380

Evaluation and design of heteropolycompound catalysts for the selective oxidation of isobutane into methacrylic acid  

Microsoft Academic Search

Chemical modifications of the 12-phosphomolybdic acid by substitution of a Mo atom by a V in the so-called Keggin primary structure and\\/or by introduction of counter-cations (NH4+, Cs+) in the secondary structure were studied. The effects of the proportion of ammonium salt in cesium–ammonium salts mixtures and of different preparation methods were also investigated. Concurrently to characterization analyses, the kinetic

M. Sultan; S. Paul; M. Fournier; D. Vanhove

2004-01-01

381

Benzylic substitution of gramines with boronic acids and rhodium or iridium catalysts.  

PubMed

Gramine-MeI salts were useful starting materials for the synthesis of 3-benzyl- and 3-allylindoles by the 1,4-addition of boronic acids to the C=C-C=N linkages generated in situ under Rh(I)-catalysis. On the other hand, under Ir(I) catalysis, the reaction of gramines with indoles was used to produce nonsymmetrical diindolylmethanes. [reaction: see text] PMID:17305348

de la Herran, Gabriela; Segura, Amaya; Csákÿ, Aurelio G

2007-02-17

382

Oxidation of ethane to ethylene and acetic acid by MoVNbO catalysts  

Microsoft Academic Search

The influence of niobium on the physicochemical properties of the MoVO system and on its catalytic properties in the oxidation of ethane to ethylene and acetic acid is examined. Solids based on MoV0.4Ox and MoV0.4Nb0.12Oy composition and calcined at 350 or 400°C were studied by X-ray diffraction, and by laser Raman and X-ray photoelectron spectroscopies. Their reactivity during reduction and

M. Roussel; M. Bouchard; E. Bordes-Richard; K. Karim; S. Al-Sayari

2005-01-01

383

Degradation of 2, 4-D acid using Mn 2+ as catalyst under UV irradiation  

Microsoft Academic Search

In this paper, the oxidative degradation of 2, 4-dichlorophenoxyacetic acid (2, 4-D) using Mn2+\\/H2O2 reagent under UV irradiation was studied. The results show that 2, 4-D was degraded more completely in Mn2+\\/H2O2 solution than traditional Fenton solutions. The effects of the concentration of Mn2+, H2O2 and pH were also investigated. And under the optimal condition of $$\\u000ac_{Mn^{2 + }

Yingping Huang; Xiangling Liu; Yanfen Fang; Qi Wang; Kingtong Lau

2009-01-01

384

Using phosphomolybdic acid (H 3PMo 12O 40) to efficiently enhance the electrocatalytic activity and CO-tolerance of platinum nanoparticles supported on multi-walled carbon nanotubes catalyst in acidic medium  

Microsoft Academic Search

A simple approach is reported for utilizing phosphomolybdic acid, H3PMo12O40, (HPMo) to enhance the electrocatalytic activity and carbon monoxide (CO) tolerance of platinum electrocatalysts supported on multi-walled carbon nanotubes (MWCNTs) in acidic medium. Pt\\/MWCNTs catalyst is prepared by the ethylene glycol reduction method, and then physically mixed with HPMo for electrochemical characterizations in terms of alcohol and CO electro-oxidation using

Xun Guo; Dao-Jun Guo; Jian-She Wang; Xin-Ping Qiu; Li-Quan Chen; Wen-Tao Zhu

2010-01-01

385

Oxidation of ?-picoline to nicotinic acid over V 2O 5-TiO 2 catalyst: Kinetic studies and reaction mechanism  

Microsoft Academic Search

Kinetic model of ?-picoline oxidation to nicotinic acid over V2O5-TiO2 catalyst in the temperature range 270–300°C was elaborated on the base of the experimental data obtained in a differential reactor. Reaction mechanism was studied by in situ FTIR method. Kinetic parameters of the reaction rates were evaluated. The model gives satisfactory agreement between predicted and experimental results over a wide

E. V. Ovchinnikova; T. V. Andrushkevich; G. Ya. Popova; V. D. Meshcheryakov; V. A. Chumachenko

2009-01-01

386

The dispersion of Keggin-type P\\/Mo polyoxometalates inside silica gel, and the preparation of catalysts for the oxidation of isobutane to methacrolein and methacrylic acid  

Microsoft Academic Search

Keggin-type P\\/Mo polyoxometalates (POM) were dispersed in a high-surface-area silica gel by means of a co-gelation procedure, in order to prepare catalysts for the gas-phase oxidation of isobutane to methacrolein and methacrylic acid. The aim was the dilution of the active phase, in order to favor the dispersion of the considerable reaction heat and limit the oxidative degradation of the

N. Ballarini; F. Candiracci; F. Cavani; H. Degrand; J.-L. Dubois; G. Lucarelli; M. Margotti; A. Patinet; A. Pigamo; F. Trifirò

2007-01-01

387

Synthesis of 1- tert-butoxy-2-propanol (PGTBE) from propylene glycol and isobutene in a packed trickle-bed reactor on acid catalysts  

Microsoft Academic Search

1-tert-Butoxy-2-propanol has been synthesized from propylene glycol and isobutene over two solid acid catalysts, montmorillonite and Amberlyst 15, in a packed trickle-bed reactor operating under different experimental conditions, and its antiknock properties as an oxygenate gasoline additive have been evaluated. The reaction on Amberlyst 15 fitted first-order kinetics for isobutene (k?=0.37 h?1) for a molar ratio propylene glycol to isobutene

R Alcántara; L Canoira; C Fernández-Mart??n; M. J Franco; J. I Martinez-Silva; A Navarro

2000-01-01

388

Transesterification of cyclohexyl acrylate with n-butanol and 2-ethylhexanol: acid-treated clay, ion exchange resins and tetrabutyl titanate as catalysts  

Microsoft Academic Search

Transesterification of cyclohexyl acrylate with n-butanol and 2-ethylhexanol was studied in a batch reactor using an acid-treated clay, ion exchange resins and tetrabutyl titanate as catalysts. The effect of various parameters on the conversion of cyclohexyl acrylate and towards the selectivity of cyclohexanol were studied to optimise the reaction conditions. The transesterified esters (n-butyl acrylate and 2-ethylhexyl acrylate) were separated

Basudeb Saha; Michael Streat

1999-01-01

389

Silica supported perchloric acid (HClO 4–SiO 2): an efficient and recyclable heterogeneous catalyst for the one-pot synthesis of amidoalkyl naphthols  

Microsoft Academic Search

An efficient and direct protocol for the preparation of amidoalkyl naphthols employing a multi-component and one-pot condensation reaction of 2-naphthol, aromatic aldehydes, and acetonitrile or acetamide in the presence of silica supported perchloric acid under solvent, solvent-free, and microwave irradiation conditions is described. The present protocol with HClO4–SiO2 catalyst is superior to the recently reported catalytic methods. It is noteworthy

Hamid Reza Shaterian; Hossein Yarahmadi; Majid Ghashang

2008-01-01

390

Brønsted acidic ionic liquid as an efficient and reusable catalyst for one-pot synthesis of 1-amidoalkyl 2-naphthols under solvent-free conditions  

Microsoft Academic Search

A mild and efficient method has been developed for the preparation of amidoalkyl naphthols from condensation of aldehydes with amides or urea and 2-naphthol in the presence of a catalytic amount of Brønsted acidic ionic liquid ([TEBSA][HSO4]) under thermal solvent-free conditions. High yields, short reaction time, easy work-up and reusability of the catalyst are advantages of this procedure.

Abdol R. Hajipour; Yosof Ghayeb; Nafisehsadat Sheikhan; Arnold E. Ruoho

2009-01-01

391

[BPy]HSO4 Acidic Ionic Liquid as a Novel, Efficient, and Environmentally Benign Catalyst for Synthesis of 1,5?Benzodiazepines under Mild Conditions  

Microsoft Academic Search

A novel and simple ionic liquid methodology for the synthesis of 1,5?benzodiazepines is described. 1?Butylpyridinium hydrogen sulphate ([BPy]HSO4), an acidic room?temperature ionic liquid, as a novel and efficient catalyst, was synthesized and used in the preparation of a series of 1,5?benzodiazepine derivatives by the reaction of o?phenylenediamine with chalcones under mild conditions. This method is easy, efficient, environmentally friendly, economical,

Yuying Du; Fuli Tian; Wenzhi Zhao

2006-01-01

392

Formation of PtRu alloy nanoparticle catalyst by radiolytic process assisted by addition of dl -tartaric acid and its enhanced methanol oxidation activity  

Microsoft Academic Search

PtRu nanoparticle catalysts with 2-nm size supported on carbon were synthesized by a radiolytic process, assisted with the\\u000a addition of dl-tartaric acid. Gradual alloying with the addition was confirmed by structural analyses with techniques of the X-ray diffraction\\u000a and the X-ray absorption fine structure. Their methanol oxidation activities evaluated by the linear sweep voltammetry were\\u000a higher than that of the

Satoru Kageyama; Satoshi Seino; Takashi Nakagawa; Hiroaki Nitani; Koji Ueno; Hideo Daimon; Takao A. Yamamoto

393

Formic acid adsorption and decomposition on TiO 2(1 1 0) and on Pd\\/TiO 2(1 1 0) model catalysts  

Microsoft Academic Search

The reaction of formic acid with TiO2(110)-(1×1) and with model catalysts with Pd nanoparticles on that oxide has been investigated using a molecular beam reactor. On the oxide surface only the dehydration reaction is seen, and it proceeds at steady state with a very high reaction probability above 500 K. There is no evidence for a dehydrogenation pathway. However, when

Michael Bowker; Peter Stone; Roger Bennett; Neil Perkins

2002-01-01

394

Combination of best promoter and micellar catalyst for more than kilo-fold rate acceleration in favor of chromic acid oxidation of d-galactose to d-galactonic acid in aqueous media at room temperature.  

PubMed

Picolinic acid, 2,2'-bipyridine and 1,10-phenanthroline promoted Cr(VI) oxidation of d-galactose to d-galactonic acid in three representative aqueous micellar media has been studied. The anionic surfactant (SDS) accelerated the rate of reaction while the cationic surfactant (CPC) and neutral surfactant (TX-100) retarded the reaction rate. Combination of bipy and SDS is the best choice for chromic acid oxidation of d-galactose to d-galactonic acid in aqueous media although 1,10-phenanthroline is best promoter in absence of micellar catalyst. PMID:23978739

Saha, Rumpa; Ghosh, Aniruddha; Sar, Pintu; Saha, Indrajit; Ghosh, Sumanta K; Mukherjee, Kakali; Saha, Bidyut

2013-08-07

395

Improved catalysts and method  

SciTech Connect

An improved catalyst and method for the oxyhydrochlorination of methane is disclosed. The catalyst includes a pyrogenic porous support on which is layered as active material, cobalt chloride in major proportion, and minor proportions of an alkali metal chloride and of a rare earth chloride. On contact of the catalyst with a gas flow of methane, HCl and oxygen, more than 60% of the methane is converted and of that converted more than 40% occurs as monochloromethane. Advantageously, the monochloromethane can be used to produce gasoline boiling range hydrocarbons with the recycle of HCl for further reaction. This catalyst is also of value for the production of formic acid as are analogous catalysts with lead, silver or nickel chlorides substituted for the cobalt chloride. 8 figs., 3 tabs.

Taylor, C.E.; Noceti, R.P.

1990-12-31

396

[Catalytic application of synthesizing n-butyl acrylate by a new type nanometer complex heteropoly acid catalyst H3PW12O40/SiO2].  

PubMed

A new nanometer complex heteropoly acid with Keggin structure, H3PW12O40/SiO2, were prepared by sol-gel method, and were characterized with IR, UV, XRD and TEM techniques. By means of this nanometer catalytic materials, the optimum conditions of the n-butyl acrylate synthesis have been studied. The results show that the complex heteropoly acid H3PW12O40/SiO2 nanoparticles have the mean grain size of 40 nm and they are typical amorphous. A strong chemical interaction exists between H3PW12O40 and silica surface. The nanoparticles have high catalytic activity for synthesizing n-butyl acrylate. The optimum catalytic conditions are as follows: the mole ratio of acrylic acid and n-butyl alcohol is 1:1.2, the reaction temperature is approximately 90-96 degrees C, and the catalyst quantity in the reaction is 10% of the acid mass. The conversion proportion is 94.37% and product yield 91.2% in 5 h. Apparently, the unique structure of the Keggin anions and surface acid center and the high specific surface area and the pseudoliquid phase of H3PW12O40/SiO2 play an important role in the esterification reactions with the acid catalyst. PMID:15760024

Zhou, Li-qun; Liu, Shi-zhong; Sun, Ju-tang

2004-10-01

397

Platinum-decorated Au porous nanotubes as highly efficient catalysts for formic acid electro-oxidation.  

PubMed

Au porous nanotubes (PNTs) were synthesized by a templating technique that involves the chemical synthesis of Ag nanowire precursors, electroless surface modification with Au, and selective etching. A subsequent galvanic replacement reaction between [PtCl(6)](2-) and residual Ag generates Pt-decorated Au porous nanotubes (Pt/Au PNTs), which represents a new type of self-sustained high surface area electrocatalysts with ultra-low Pt loading. Structural characterizations with scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray powder diffraction (XRD) reveal a novel nanoarchitecture with multimodal open porosity and excellent structural continuity and integrity. Cyclic voltammetry (CV) demonstrates that these Pt/Au PNTs possess very high electrocatalytic activity toward formic acid oxidation with enhanced tolerance to CO poisoning. PMID:20166117

Gu, Xiaohu; Cong, Xiao; Ding, Yi

2010-03-15

398

Metallic organophosphates as catalysts in asymmetric synthesis: a return journey.  

PubMed

This perspective article provides a general overview of the most relevant topics in the applications of chiral metallic organophosphates. A brief introduction along with a historic comparative profile of the BINOL and phosphoric acid analogues are given. Next, a selection of the most outstanding uses of the catalysts according to the employed metal is presented. PMID:22569751

Parra, Alejandro; Reboredo, Silvia; Martín Castro, Ana M; Alemán, José

2012-05-09

399

Al and Ga-promoted WO 3\\/ZrO 2 strong solid acid catalysts and their catalytic activities in n-butane isomerization  

Microsoft Academic Search

A series of Al- and Ga-promoted tungstated zirconia strong solid acid catalysts were prepared. The effect of Al2O3 and Ga2O3 on the structural, acidic and redox features of WO3\\/ZrO2 (WZ) has been characterized by means of X-ray powder diffraction (XRD), N2 adsorption (BET), UV–visible diffuse reflectance spectra (UV–vis), infrared spectra (IR), NH3 temperature-programmed desorption (NH3-TPD) and H2 temperature-programmed reduction (H2-TPR).

Xiao-Rong Chen; Chang-Lin Chen; Nan-Ping Xu; Chung-Yuan Mou

2004-01-01

400

Improved zeolitic isocracking catalysts  

SciTech Connect

Chevron Research Company introduced the first low pressure, low temperature catalytic hydrocracking process--ISOCRACKING--in 1959. Within the last four years, Chevron has developed and commercialized three new zeolitic ISOCRACKING catalysts. ICR 209 is Chevron`s latest noble metal ISOCRACKING catalyst. It offers improved liquid yield stability, longer life, and superior polynuclear aromatics control compared to its predecessor. ICR 209`s high hydrogenation activity generates the highest yields of superior quality jet fuel of any zeolitic ISOCRACKING catalyst. The second new ISOCRACKING catalyst, ICR 208, is a base metal catalyst which combines high liquid selectivity and high light naphtha octane in hydrocrackers operating for maximum naphtha production. ICR 210 is another new base metal catalyst which offers higher liquid yields and longer life than ICR 208 by virtue of a higher hydrogenation-to-acidity ratio. Both ICR 208 and ICR 210 have been formulated to provide higher liquid yield throughout the cycle and longer cycle length than conventional base metal/zeolite catalysts. This paper will discuss the pilot plant and commercial performances of these new ISOCRACKING catalysts.

Dahlberg, A.J.; Habib, M.M.; Moore, R.O. [Chevron Research and Technology Co., Richmond, CA (United States); Law, D.V. [Chevron International Oil Co., San Francisco, CA (United States); Convery, L.J. [ABB Lummus Crest, Bloomfield, NJ (United States)

1995-09-01

401

Reactivation of hydroformylation catalysts  

SciTech Connect

A process is described for improving the catalytic activity of a partially deactivated solubilized rhodium-tertiary organophosphine complex hydroformylation catalyst, which comprises (1) mixing under non-hydroformylating conditions, a organic liquid medium containing said solubilized partially deactivated complex catalyst, with propargyl alcohol and a carboxylic acid of the formula RCOOH wherein R represents hydrogen or an alkyl or aryl radical to obtain a treated solubilized rhodium-tertiary organophosphine complex product solution; and (2) removing from said product solution, the carboxylic acid employed in Step (1) to obtain a rhodium-tertiary organophosphine complex hydroformylation catalyst that is more catalytically active than said partially deactivated rhodium-tertiary organophosphine complex hydroformylation catalyst starting material of Step (1).

Babin, J.E.; Bryant, D.R.; Harrison, A.M.; Miller, D.J.

1993-08-17

402

Formic Acid Dehydrogenation on Au-Based Catalysts at Near-Ambient Temperatures  

SciTech Connect

Formic acid (HCOOH) is a convenient hydrogen carrier in fuel cells designed for portable use. Recent studies have shown that HCOOH decomposition is catalyzed with Ru-based complexes in the aqueous phase at near-ambient temperatures. HCOOH decomposition reactions are used frequently to probe the effects of alloying and cluster size and of geometric and electronic factors in catalysis. These studies have concluded that Pt is the most active metal for HCOOH decomposition, at least as large crystallites and extended surfaces. The identity and oxidation state of surface metal atoms influence the relative rates of dehydrogenation (HCOOH {yields} H{sub 2} + CO{sub 2}) and dehydration (HCOOH {yields} H{sub 2}O + CO) routes, a selectivity requirement for the synthesis of CO-free H{sub 2} streams for low-temperature fuel cells. Group Ib and Group VIII noble metals catalyze dehydrogenation selectively, while base metals and metal oxides catalyze both routes, either directly or indirectly via subsequent water-gas shift (WGS) reactions.

Ojeda, Manuel; Iglesia, Enrique

2008-11-24

403

Enantioselective liquid-liquid extractions of underivatized general amino acids with a chiral ketone extractant.  

PubMed

The chiral ketone (S)-3 shows high kinetic enantioselectivities toward the L form for general underivatized amino acids with hydrophobic side chains and a high thermodynamic enantioselectivity toward the D form for cysteine with its -SH polar side chain when used as an extractant in enantioselective liquid-liquid extractions in the presence of Aliquat 336. Consecutive extractions by imine formation and hydrolysis increase the enantiopurity of the amino acid, as both of these reactions are L-form-selective. PMID:23317343

Huang, Haofei; Nandhakumar, Raju; Choi, Misun; Su, Zhishan; Kim, Kwan Mook

2013-02-05

404

General acid-base catalysis in the mechanism of a hepatitis delta virus ribozyme.  

PubMed

Many protein enzymes use general acid-base catalysis as a way to increase reaction rates. The amino acid histidine is optimized for this function because it has a pK(a) (where K(a) is the acid dissociation constant) near physiological pH. The RNA enzyme (ribozyme) from hepatitis delta virus catalyzes self-cleavage of a phosphodiester bond. Reactivity-pH profiles in monovalent or divalent cations, as well as distance to the leaving-group oxygen, implicate cytosine 75 (C75) of the ribozyme as the general acid and ribozyme-bound hydrated metal hydroxide as the general base in the self-cleavage reaction. Moreover, C75 has a pK(a) perturbed to neutrality, making it "histidine-like." Anticooperative interaction is observed between protonated C75 and a metal ion, which serves to modulate the pK(a) of C75. General acid-base catalysis expands the catalytic repertoire of RNA and may provide improved rate acceleration. PMID:10688799

Nakano, S; Chadalavada, D M; Bevilacqua, P C

2000-02-25

405

A new selective route to 5-hydroxymethylfurfural from furfural and furfural derivatives over microporous solid acidic catalysts  

Microsoft Academic Search

Hydroxymethylation of furfural and its 1,3 dithiolane derivative with aqueous formaldehyde was performed in a batch mode in the presence of dealuminated mordenites as catalysts, at 363 K. Starting from furfural, the selectivity to 5-hydroxymethylfurfural is about 30% whatever the catalysts. However, the selectivity can rise up to 50% if an organic co-solvent is used for simultaneous extraction of 5-hydroxymethylfurfural

Jérôme Lecomte; Annie Finiels; Claude Moreau

1999-01-01

406

Occurrence of the general control of amino acid biosynthesis in yeasts.  

PubMed

The response of three amino acid biosynthetic enzymes, threonine dehydratase, tyrosine aminotransferase and saccharopine dehydrogenase, to conditions of histidine, tryptophan or lysine limitation was investigated in 15 yeast species. The activities of all these enzymes increased about two- to fourfold as a result of action of the general control of amino acid biosynthesis in Brettanomyces anomalus, Candida maltosa, Hansenula polymorpha, Rhodosporidium toruloides, Saccharomyces cerevisiae and Yarrowia lipolytica. No evidence for the existence of the general control was found in Candida brumptii, Candida utilis, Hansenula anomala, Hansenula henricii, Kluyveromyces marxianus, Pichia guilliermondii, Saccharomycopsis capsularis, Trichosporon adeninovorans and Trigonopsis variabilis. PMID:2338623

Bode, R; Schüssler, K; Schmidt, H; Hammer, T; Birnbaum, D

1990-01-01

407

Combinatorial catalyst discovery.  

PubMed

There have been recent attempts to use the principles of combinatorial chemistry and high-throughput screening strategies for catalyst identification. With the technology available that allows the synthesis of large libraries, scientists of varied backgrounds have implemented screening efforts to identify active and selective catalysts. Within this context, several techniques have come to light in the past year: infrared thermography is used to identify optimal catalysts by monitoring the change in temperature for exothermic reactions; fluorescence and colored-dye assays, a familiar tool to biologists, is being applied to the identification of catalysts that exhibit the highest activity. Whereas none of these screening methods provide a general solution to the problem of screening large combinatorial libraries (there is likely to be no general solution), each advance represents an important intellectual and technological step forward. PMID:10359716

Kuntz, K W; Snapper, M L; Hoveyda, A H

1999-06-01

408

Ascorbic Acid as a Standard for Iodometric Titrations. An Analytical Experiment for General Chemistry  

NASA Astrophysics Data System (ADS)

Ascorbic acid is suggested as the weighable compound for the standardization of iodine solutions in an analytical experiment in general chemistry. The experiment involves an iodometric titration in which iodine reacts with ascorbic acid, oxidizing it to dehydroascorbic acid. The redox titration endpoint is determined by the first iodine excess that is complexed with starch, giving a deep blue-violet color. The results of the titration of iodine solution using ascorbic acid as a calibration standard were compared with the results acquired by the classic method using a standardized solution of sodium thiosulfate. The standardization of the iodine solution using ascorbic acid was accurate and precise, with the advantages of saving time and avoiding mistakes due to solution preparation. The colorless ascorbic acid solution gives a very clear and sharp titration end point with starch. It was shown by thermogravimetric analysis that ascorbic acid can be dried at 393 K for 2 h without decomposition. This experiment allows general chemistry students to perform an iodometric titration during a single laboratory period, determining with precision the content of vitamin C in pharmaceutical formulations.

Silva, Cesar R.; Simoni, Jose A.; Collins, Carol H.; Volpe, Pedro L. O.

1999-10-01

409

Awake craniotomy induces fewer changes in the plasma amino acid profile than craniotomy under general anesthesia.  

PubMed

In this prospective, observational, 2-armed study, we compared the plasma amino acid profiles of patients undergoing awake craniotomy to those undergoing craniotomy under general anesthesia. Both experimental groups were also compared with a healthy, age-matched and sex-matched reference group not undergoing surgery. It is our intention to investigate whether plasma amino acid levels provide information about physical and emotional stress, as well as pain during awake craniotomy versus craniotomy under general anesthesia. Both experimental groups received preoperative, perioperative, and postoperative dexamethasone. The plasma levels of 20 amino acids were determined preoperative, perioperative, and postoperatively in all groups and were correlated with subjective markers for pain, stress, and anxiety. In both craniotomy groups, preoperative levels of tryptophan and valine were significantly decreased whereas glutamate, alanine, and arginine were significantly increased relative to the reference group. Throughout time, tryptophan levels were significantly lower in the general anesthesia group versus the awake craniotomy group. The general anesthesia group had a significantly higher phenylalanine/tyrosine ratio, which may suggest higher oxidative stress, than the awake group throughout time. Between experimental groups, a significant increase in large neutral amino acids was found postoperatively in awake craniotomy patients, pain was also less and recovery was faster. A significant difference in mean hospitalization time was also found, with awake craniotomy patients leaving after 4.53+/-2.12 days and general anesthesia patients after 6.17+/-1.62 days; P=0.012. This study demonstrates that awake craniotomy is likely to be physically and emotionally less stressful than general anesthesia and that amino acid profiling holds promise for monitoring postoperative pain and recovery. PMID:19295387

Hol, Jaap W; Klimek, Markus; van der Heide-Mulder, Marieke; Stronks, Dirk; Vincent, Arnoud J; Klein, Jan; Zijlstra, Freek J; Fekkes, Durk

2009-04-01

410

Generalization of morphine and lysergic acid diethylamide (LSD) stimulus properties to narcotic analgesics  

Microsoft Academic Search

The present investigation sought to determine whether the stimulus properties of morphine and lysergic acid diethylamide (LSD) would generalize to several narcotic analgesics which vary in their subjective effects. Morphine and saline served as discriminative stimuli for one group of rats in a 2-lever discrimination task. LSD and saline were discriminative stimuli for a second group. Depression of one lever

I. D. Hirschhorn; J. A. Rosecrans

1976-01-01

411

Amino Acid Complementarity: A Biochemical Exemplar of Stoichiometry for General and Health Sciences Chemistry  

ERIC Educational Resources Information Center

The standard introduction to stoichiometry and simple exemplars can motivate students to learn the stoichiometric studies and the condensation reaction that occurs between amino acids to form the peptide bond. This topic can be integrated into general chemistry courses as an alternative to inclusion of a separate biochemistry course that could be…

Vitz, Ed

2005-01-01

412

General aspect of catalytic hydrogenation and isomerization reactions on oxide catalyst. Characteristics of the reactions via ionic and nonionic intermediates  

SciTech Connect

An analysis of new and available data, mostly published by Tanaka and Okuhara, on the hydrogenation of alkenes and conjugated dienes and the hydrogen-deuterium exchange on the oxides of cadmium, magnesium, zinc, cobalt, chromium, thorium, zirconium, and lanthanum, and on molybdenum disulfide suggested that the partial hydrogenation of conjugated dienes catalyzed by cadmium and magnesium oxide proceeds by a mechanism which is similar to that of diene hydrogenation on supported alkali metals or on alkali metal hydride and involves allyl carbanion intermediates. The same ionic mechanism apparently also occurs in the double-bond migration of n-alkenes on cadmium oxide, and the isomerization catalyzed by molybdenum disulfide. The nonionic reaction mechanism via o-alkyl and o- or m-allyl intermediates apparently proceeds on active sites of a definite structure, i.e., a specific degree of coordination, but the ionic mechanism seems to depend only on the acidity or basicity of the sites. The nonspecific nature of the site for the ionic mechanism may result in high resistance to poisoning.

Tanaka, K.; Okuhara, T.

1980-09-01

413

Catalytic ketonization over oxide catalysts  

Microsoft Academic Search

Carboxylic acids were selectively reduced to aldehydes when their mixture with formic acid in the form of vapour had been passed over solid catalyst. The activities of 20?wt.% MO2\\/A catalysts, where M?=?Mn, Ce or Zr and A?=?Al2O3 have been studied in the mentioned reaction at the temperature range of 573–723?K. Hexanoic acid and its branched monomethyl and dimethyl isomers were

M. Gli?ski; A. Kozio?; D. ?omot; Z. Kaszkur

2007-01-01

414

Correlation between the infrared band frequency of the silanol bending vibration in TiO sub 2 -SiO sub 2 catalysts and activity for acid catalysis  

SciTech Connect

It is well known that the surface acidity of a metal oxide is improved with the incorporation of another metal oxide to form a binary oxide. Thus, recently many kinds of mixed oxides were reported to show catalytic activity for particular reactions. Titania-silica mixed oxides are interesting materials. The combination of TiO{sub 2} and SiO{sub 2} generated very strong acid sites and showed high catalytic activity and selectivity for the amination of phenol with ammonia to produce aniline. In this paper the authors report the correlation between the band frequency of the silanol bending vibration in TiO{sub 2}-SiO{sub 2} catalysts and acid catalytic activity. For this purpose, the 2-propanol dehydration and cumene dealkylation were used as test reactions.

Sohn, J.R.; Jang, H.J. (Kyungpook National Univ., Taegu (Korea))

1991-12-01

415

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

416

Efficient conversion of furfuryl alcohol into alkyl levulinates catalyzed by an organic-inorganic hybrid solid acid catalyst.  

PubMed

A clean, facile, and environment-friendly catalytic method has been developed for the conversion of furfuryl alcohol into alkyl levulinates making use of the novel solid catalyst methylimidazolebutylsulfate phosphotungstate ([MIMBS]?PW??O??). The solid catalyst is an organic-inorganic hybrid material, which consists of an organic cation and an inorganic anion. A study for optimizing the reaction conditions such as the reaction time, the temperature and the catalyst loading has been performed. Under optimal conditions, a high n-butyl levulinate yield of up to 93?% is obtained. Furthermore, the kinetics of the reaction pathways and the mechanism for the alcoholysis of furfuryl alcohol are discussed. This method is environmentally benign and economical for the conversion of biomass-based derivatives into fine chemicals. PMID:21226220

Zhang, Zehui; Dong, Kun; Zhao, Zongbao Kent

2011-01-17

417

Combined Effects of Sb-Doping and of Preparation via Lacunary Precursor for P\\/Mo-Based, Keggin-Type Polyoxometalates, Catalysts for the Selective Oxidation of Isobutane to Methacrylic Acid  

Microsoft Academic Search

Catalysts for the selective oxidation of isobutane to methacrylic acid, based on ammonium salts of phosphorus\\/molybdenum Keggin-type polyoxometalates, were prepared by precipitation of a lacunary precursor at pH 4.0, and by calcination of the precipitate at 350 °C in air. The thermal treatment led to the transformation of the lacunary polyoxometalate into (NH4)3PMo12 O40. This procedure yielded a catalyst that

F. Cavani; R. Mezzogori; A. Pigamo; F. Trifirò

2003-01-01

418

The support effect on propane combustion over platinum catalyst: control of the oxidation-resistance of platinum by the acid strength of support materials  

Microsoft Academic Search

The support effect on the low temperature propane combustion over supported platinum catalyst was studied by using a series of metal oxides as support materials: MgO, La2O3, ZrO2, Al2O3, SiO2, SiO2–Al2O3, and SO42?–ZrO2. The catalytic activity varied with the support materials, and the platinum supported on more acidic support material showed higher activity. The support effect on the oxidation state

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

2002-01-01

419

Vapor phase oxidation of benzoic acid to phenol over a novel catalyst system consisting of NiO and NiFe{sub 2}O{sub 4}  

SciTech Connect

NiO and Fe{sub 2}O{sub 3} were found to show the catalytic activities for the vapor phase oxidation of benzoic acid to form phenol. Furthermore, the enhancement of the activity and phenol selectivity were achieved by combined Ni and Fe components prepared by precipitation. The calcination temperature and the atomic ratio of Ni to Fe were found to be important for the enhancement of activity. The homogeneous distribution profile of NiO and NiFe{sub 2}O{sub 4} on the surface and in the bulk of the catalyst is essential for the optimization of phenol formation. 32 refs., 7 figs., 4 tabs.

Miki, Jun; Asanuma, Minoru; Tachibana, Yakudo [NKK Corporation, Kawasaki (Japan)] [and others

1995-02-01

420

Telechelic polyesters of ethane diol and adipic or sebacic acid by means of bismuth carboxylates as non-toxic catalysts  

Microsoft Academic Search

Dimethyladipate or dimethylsebacate were polycondensed with an excess of 1,2-ethane diol in bulk using two different temperature\\/time programs. Bismuth(III)n-hexanoate (BiHex3), tin(II)2-ethylhexanoate (SnOct2) and titanium tetrabutoxide were used as catalysts. Only the bismuth catalyst yielded clean telechelic polyesters having two ethylene glycol endgroups. With SnOct2 cyclic oligoesters were obtained as byproducts. Ti(OBu)4 yielded OH-terminated linear chains containing large amounts of diethylene

Hans R. Kricheldorf; Gesa Behnken; Gert Schwarz

2005-01-01

421

Convenient synthesis of unsymmetrical organochalcogenides using organoboronic acids with dichalcogenides via cleavage of the S-S, Se-Se, or Te-Te bond by a copper catalyst.  

PubMed

This article describes the methodology for a copper-catalyzed preparation of numerous monochalcogenides from dichalcogenides with organoboronic acids. Unsymmetrical diorgano-monosulfides, selenides, and tellurides can be synthesized by the coupling of dichalcogenides with aryl- or alkylboronic acids using a copper catalyst in air. The present reaction can take advantage of both organochalcogenide groups on dichalcogenide. PMID:17288374

Taniguchi, Nobukazu

2007-02-16

422

Sulfamic acid as an efficient and recyclable catalyst for the ring opening of epoxides with amines and anilines: An easy synthesis of ?-amino alcohols under solvent-free conditions  

Microsoft Academic Search

Application of sulfamic acid as an efficient and green catalyst for the ring opening of epoxides by aliphatic and aromatic amines under solvent-free conditions is described. In this process the use of basic neutralization agent was not required due to the intrinsic zwitterionic property of sulfamic acid. The salient features of this methodology are cheaper process, easy availability of the

Ahmed Kamal; B. Rajendra Prasad; A. Malla Reddy; M. Naseer A. Khan

2007-01-01

423

Acid-base chemistry of the blood--a general model.  

PubMed

This paper describes a general model of acid-base chemistry of the blood which can be used to simulate physiological perturbation of acid-base chemistry on addition or removal of any buffer acid or base. In particular, it is shown how this model can be used to estimate the concentrations of buffer acid or base. In particular, it is shown how this model can be used to estimate the concentrations of buffer acids and bases when blood is equilibrated to a new pCO2, when hydrogen ions H+ are added to the blood, or when two pools of blood with different concentrations of buffer acids and bases are mixed. The ability of the model to represent the addition or removal of any acid or base is a significant increase in functionality above the Siggaard-Andersen nomogram which is limited to simulating the effects of equilibrating the blood to a new pCO2. When used to represent the situation where blood is equilibrated at a new pCO2 the model enables calculation of the amount CO2 removed during equilibration, a further increase in functionality above the Siggaard-Andersen nomogram. In two experimental situations, equilibrating blood to a new pCO2 and addition of H+ ions, the model predictions are shown to be consistent with existing experimental data in the form of the Siggaard-Andersen nomogram. PMID:8894395

Rees, S E; Andreassen, S; Hovorka, R; Summers, R; Carson, E R

1996-10-01

424

H 3 PO 4 - and H 2 SO 4 -treated niobic acid as heterogeneous catalyst for methyl ester production  

Microsoft Academic Search

The activity of solid niobic acid treated with sulfuric acid and with phosphoric acid was tested in the catalytic esterification\\u000a of oleic acid and in transesterification of soybean oil with methanol. X-ray diffraction studies revealed niobic acid treated\\u000a with sulfuric acid to be an amorphous solid, while niobic acid treated with phosphoric acid presented a crystalline phase,\\u000a probably due to

Mendelssolm K. de Pietre; Luiz C. P. Almeida; Richard Landers; Rita C. G. Vinhas; Fernando J. Luna

2010-01-01

425

Engelhard acquires German catalyst maker  

SciTech Connect

Engelhard will acquire the precious- and base-metal catalyst businesses of Doduco GmbH & Co. (Pforzheim, Germany), a privately held supplier of catalysts to the chemical and pharmaceutical industries. {open_quotes}This is an excellent product expansion for us, one that we believe can be leveraged throughout Europe and, later, globally,{close_quotes} says James A. Martin, group v.p., president, and general manager of Engelhard`s chemical catalysts group.

NONE

1996-10-16

426

General acid-base catalysis mediated by nucleobases in the hairpin ribozyme  

PubMed Central

The catalytic mechanism by which the hairpin ribozyme accelerates cleavage or ligation of the phosphodiester backbone of RNA has been incompletely understood. There is experimental evidence for an important role for an adenine (A38) and a guanine (G8), and it has been proposed that these act in general acid-base catalysis. In this work we show that a large reduction in cleavage rate on substitution of A38 by purine (A38P) can be reversed by replacement of the 5?-oxygen atom at the scissile phosphate by sulfur (5?-PS), which is a much better leaving group. This is consistent with A38 acting as the general acid in the unmodified ribozyme. The rate of cleavage of the 5?-PS substrate by the A38P ribozyme increases with pH log-linearly, indicative of a requirement for a deprotonated base with a relatively high pKa. On substitution of G8 by diaminopurine, the 5?-PS substrate cleavage rate at first increases with pH and then remains at a plateau, exhibiting an apparent pKa consistent with this nucleotide acting in general base catalysis. Alternative explanations for the pH dependence of hairpin ribozyme reactivity are discussed, from which we conclude that general acid-base catalysis by A38 and G8 is the simplest and most probable explanation consistent with all the experimental data.

Kath-Schorr, Stephanie; Wilson, Timothy J.; Li, Nan-Sheng; Lu, Jun; Piccirilli, Joseph A.; Lilley, David M. J.

2012-01-01

427

Catalyst development for coal liquefaction. Interim report, July--September 1976  

Microsoft Academic Search

This program is directed toward the development of improved catalysts for coal liquefaction. It consists of the following tasks: catalyst formulation and preparation; catalyst characterization; catalyst screening; and reactor modification for fixed bed evaluation. Catalyst formulations will focus on the areas of support acidity, pore-volume, and pore-size distribution, hydrothermal stability and nature of the active component. Catalyst screening will be

Hindin

1976-01-01

428

Vapor-phase synthesis of ethyl tert -butyl ether on heteropoly acid-polymer composite film catalysts  

Microsoft Academic Search

H3PMo12O40-polysulfone and H3PMo12O40-polyphenylene oxide composite film catalysts were prepared by a membrane preparation technique. They showed the higher catalytic activities than H3PMo12O40 in the vapor-phase synthesis of ethyl tert-butyl ether.

Gyo Ik Park; Seong Soo Lim; In Kyu Song; Wha Young Lee

2002-01-01

429

Catalyst pretreatment for olefin hydration  

SciTech Connect

This patent describes an improvement in the process for the production of diisopropyl ether or isopropanol by hydration of feedstock containing propene, which comprises contacting the propene feedstock and water in a hydration zone with porous solid metal oxide acidic olefin hydration catalyst under olefins hydration conditions. The improvement comprises: pretreating the porous solid catalyst prior to contacting with the propene feedstock with a wetting agent containing at least one polar aliphatic oxygenated hydrocarbon to substantially wet the solid catalyst and sorb the wetting agent into pores of the solid catalyst.

Child, J.E.; Choi, B.C.; Ragonese, F.P.

1991-04-30

430

pKa Modulation of the Acid/Base Catalyst within GH32 and GH68: A Role in Substrate/Inhibitor Specificity?  

PubMed Central

Glycoside hydrolases of families 32 (GH32) and 68 (GH68) belong to clan GH-J, containing hydrolytic enzymes (sucrose/fructans as donor substrates) and fructosyltransferases (sucrose/fructans as donor and acceptor substrates). In GH32 members, some of the sugar substrates can also function as inhibitors, this regulatory aspect further adding to the complexity in enzyme functionalities within this family. Although 3D structural information becomes increasingly available within this clan and huge progress has been made on structure-function relationships, it is not clear why some sugars bind as inhibitors without being catalyzed. Conserved aspartate and glutamate residues are well known to act as nucleophile and acid/bases within this clan. Based on the available 3D structures of enzymes and enzyme-ligand complexes as well as docking simulations, we calculated the pKa of the acid-base before and after substrate binding. The obtained results strongly suggest that most GH-J members show an acid-base catalyst that is not sufficiently protonated before ligand entrance, while the acid-base can be fully protonated when a substrate, but not an inhibitor, enters the catalytic pocket. This provides a new mechanistic insight aiming at understanding the complex substrate and inhibitor specificities observed within the GH-J clan. Moreover, besides the effect of substrate entrance on its own, we strongly suggest that a highly conserved arginine residue (in the RDP motif) rather than the previously proposed Tyr motif (not conserved) provides the proton to increase the pKa of the acid-base catalyst.

Yuan, Shuguang; Le Roy, Katrien; Venken, Tom; Lammens, Willem; Van den Ende, Wim; De Maeyer, Marc

2012-01-01

431

Reuse of sewage sludge as a catalyst in ozonation--efficiency for the removal of oxalic acid and the control of bromate formation.  

PubMed

Sewage derived sludge is produced with an annual amount increase of 2% all over the world and it is an urgent issue to be addressed by human being. In the present study, sludge was converted into sludge-based catalyst (SBC) with ZnCl2 as activation agent and characterized by several methods (e.g., scanning electron microscope, X-ray photoelectron spectroscope and Fourier transform infrared spectroscope). Then it was used as a catalyst to enhance the removal of refractory organic matter, oxalic acid, and to control the formation of bromate (BrO3-) in bench semi-continuous ozonation experiments. The effects of various operating parameters on the control of BrO3- formation were investigated. Furthermore, the mechanism for the enhancement of organic matter removal and the control of BrO3- formation was discussed as well. Results indicate that the combination of SBC with ozone shows a strong synergistic effect, resulting in a notable improvement on oxalic acid removal. A crucial surface reaction mechanism for the enhancement of organic matter removal is proposed on the basis of negative effect of higher pH and no inhibition effect of tert-butanol. The control for BrO3- formation was demonstrated and the reason for its control in the process of O3/SBC is the combined effect of SBC reductive properties, ozone exposure decrease and hydrogen peroxide concentration increase. PMID:23021317

Wen, Gang; Pan, Zhi-Hui; Ma, Jun; Liu, Zheng-Qian; Zhao, Lei; Li, Jun-Jing

2012-09-16

432

Superior performance of metal-organic frameworks over zeolites as solid acid catalysts in the Prins reaction: green synthesis of nopol.  

PubMed

The catalytic performance of a set of metal-organic frameworks [CuBTC, FeBTC, MIL-100(Fe), MIL-100(Cr), ZIF-8, MIL-53(Al)] was investigated in the Prins condensation of ?-pinene with formaldehyde and compared with the catalytic behavior of conventional aluminosilicate zeolites BEA and FAU and titanosilicate zeolite MFI (TS-1). The activity of the investigated metal-organic frameworks (MOFs) increased with the increasing concentration of accessible Lewis acid sites in the order ZIF-8acid sites of zeolites BEA and FAU, which showed significantly lower selectivity to the target nopol than the MOFs. Its high activity, the preservation of its structure and active sites, and the possibility to use it in at least three catalytic cycles without loss of activity make MIL-100 (Fe) the best performing catalyst of the series for the Prins condensation of ?-pinene and paraformaldehyde. Our report exemplifies the advantages of MOFs over zeolites as solid catalysts in liquid-phase reactions for the production of fine chemicals. PMID:23592600

Opanasenko, Maksym; Dhakshinamoorthy, Amarajothi; Hwang, Young Kyu; Chang, Jong-San; Garcia, Hermenegildo; ?ejka, Ji?í

2013-04-16

433

Electron-withdrawing trifluoromethyl groups in combination with hydrogen bonds in polyols: Brønsted acids, hydrogen-bond catalysts, and anion receptors.  

PubMed

Electron-withdrawing trifluoromethyl groups were characterized in combination with hydrogen-bond interactions in three polyols (i.e., CF3CH(OH)CH2CH(OH)CF3, 1; (CF3)2C(OH)C(OH)(CF3)2, 2; ((CF3)2C(OH)CH2)2CHOH, 3) by pKa measurements in DMSO and H2O, negative ion photoelectron spectroscopy and binding constant determinations with Cl(-). Their catalytic behavior in several reactions were also examined and compared to a Brønsted acid (HOAc) and a commonly employed thiourea ((3,5-(CF3)2C6H3NH)2CS). The combination of inductive stabilization and hydrogen bonds was found to afford potent acids which are effective catalysts. It also appears that hydrogen bonds can transmit the inductive effect over distance even in an aqueous environment, and this has far reaching implications. PMID:23725455

Shokri, Alireza; Wang, Xue-Bin; Kass, Steven R

2013-06-12

434

Electrochemical oxidation of esters of ethane-1,1,2,2-tetracarboxylic acid in the presence of electron carrier catalysts  

Microsoft Academic Search

1.Electrochemical oxidation of esters of ethane-1,1,2,2-tetracarboxylic acid in the presence of hydrohalic acid salts in acetonitrile leads to esters of ethylenetetracarboxylic acid; in alcohols not only an oxidative dehydrogenation takes place, but also esters of 1-alkoxyethane-1,1,2,2-tetracarboxylic acid are formed.2.When the reaction is carried out in methanol, the yield of the ester of ethylenetetracarboxylic acid and the ester of 1-methoxyethane-1,1,2,2-tetracarboxylic acid

M. N. Élinson; S. K. Fedukovich; G. I. Nikishin

1988-01-01

435

Mechanistic characterization of the HDV genomic ribozyme: solvent isotope effects and proton inventories in the absence of divalent metal ions support C75 as the general acid.  

PubMed

The hepatitis delta virus (HDV) ribozyme uses the nucleobase C75 and a hydrated Mg(2+) ion as the general acid-base catalysts in phosphodiester bond cleavage at physiological salt. A mechanistic framework has been advanced that involves one Mg(2+)-independent and two Mg(2+)-dependent channels. The rate-pH profile for wild-type (WT) ribozyme in the Mg(2+)-free channel is inverted relative to the fully Mg(2+)-dependent channel, with each having a near-neutral pKa. Inversion of the rate-pH profile was used as the crux of a mechanistic argument that C75 serves as general acid both in the presence and absence of Mg(2+). However, subsequent studies on a double mutant (DM) ribozyme suggested that the pKa observed for WT in the absence of Mg(2+) arises from ionization of C41, a structural nucleobase. To investigate this further, we acquired rate-pH/pD profiles and proton inventories for WT and DM in the absence of Mg(2+). Corrections were made for effects of ionic strength on hydrogen ion activity and pH meter readings. Results are accommodated by a model wherein the Mg(2+)-free pKa observed for WT arises from ionization of C75, and DM reactivity is compromised by protonation of C41. The Brønsted base appears to be water or hydroxide ion depending on pH. The observed pKa's are related to salt-dependent pH titrations of a model oligonucleotide, as well as electrostatic calculations, which support the local environment for C75 in the absence of Mg(2+) being similar to that in the presence of Mg(2+) and impervious to bulk ions. Accordingly, the catalytic role of C75 as the general acid does not appear to depend on divalent ions or the identity of the Brønsted base. PMID:18842044

Cerrone-Szakal, Andrea L; Siegfried, Nathan A; Bevilacqua, Philip C

2008-10-09

436

Catalyst aging procedure simulates FCC conditions  

SciTech Connect

A hydrothermal deactivation procedure, using varied catalyst sample steaming times, has been developed to better simulate the distribution of near-fresh and moderately and severely deactivated catalyst particles in equilibrium fluid catalytic cracking (FCC) catalysts. Better simulation of the actual equilibrium catalyst results in better pilot plant simulation of actual operations, and better indications of commercial product distribution and quality. Comparison of hydrothermal deactivation procedures has shown that conventional aging of catalyst samples, that generally hydrothermally age fresh catalyst for a defined period of time, does not simulate commercial operations as well.

Keyworth, D.A.; Turner, W.J.; Reid, T.A.

1988-03-14

437

Catalyst of a metal heteropoly acid salt that is insoluble in a polar solvent on a non-metallic porous support and method of making  

DOEpatents

The present invention includes a catalyst having (a) a non-metallic support having a plurality of pores; (b) a metal heteropoly acid salt that is insoluble in a polar solvent on the non-metallic support; wherein at least a portion of the metal heteropoly acid salt is dispersed within said plurality of pores. The present invention also includes a method of depositing a metal heteropoly acid salt that is insoluble in a polar solvent onto a non-metallic support having a plurality of pores. The method has the steps of: (a) obtaining a first solution containing a first precursor of a metal salt cation; (b) obtaining a second solution containing a second precursor of a heteropoly acid anion in a solvent having a limited dissolution potential for said first precursor; (c) impregnating the non-metallic support with the first precursor forming a first precursor deposit within the plurality of pores, forming a first precursor impregnated support; (d) heating said first precursor impregnated support forming a bonded first precursor impregnated support; (e) impregnating the second precursor that reacts with the precursor deposit and forms the metal heteropoly acid salt.

Wang, Yong [Richland, WA; Peden, Charles H. F. [West Richland, WA; Choi, Saemin [Richland, WA

2002-10-29

438

Bimetallic Catalysts.  

ERIC Educational Resources Information Center

|Chemical reaction rates can be controlled by varying composition of miniscule clusters of metal atoms. These bimetallic catalysts have had major impact on petroleum refining, where work has involved heterogeneous catalysis (reacting molecules in a phase separate from catalyst.) Experimentation involving hydrocarbon reactions, catalytic…

Sinfelt, John H.

1985-01-01

439

Bimetallic Catalysts.  

ERIC Educational Resources Information Center

Chemical reaction rates can be controlled by varying composition of miniscule clusters of metal atoms. These bimetallic catalysts have had major impact on petroleum refining, where work has involved heterogeneous catalysis (reacting molecules in a phase separate from catalyst.) Experimentation involving hydrocarbon reactions, catalytic…

Sinfelt, John H.

1985-01-01

440

Enhancement of alkylation catalysts for improved supercritical fluid regeneration  

DOEpatents

A method of modifying an alkylation catalyst to reduce the formation of condensed hydrocarbon species thereon. The method comprises providing an alkylation catalyst comprising a plurality of active sites. The plurality of active sites on the alkylation catalyst may include a plurality of weakly acidic active sites, intermediate acidity active sites, and strongly acidic active sites. A base is adsorbed to a portion of the plurality of active sites, such as the strongly acidic active sites, selectively poisoning the strongly acidic active sites. A method of modifying the alkylation catalyst by providing an alkylation catalyst comprising a pore size distribution that sterically constrains formation of the condensed hydrocarbon species on the alkylation catalyst or by synthesizing the alkylation catalyst to comprise a decreased number of strongly acidic active sites is also disclosed, as is a method of improving a regeneration efficiency of the alkylation catalyst.

Ginosar, Daniel M. (Idaho Falls, ID); Petkovic, Lucia M. (Idaho Falls, ID)

2010-12-28

441

A General, Efficient and Functional-Group-Tolerant Catalyst System for the Palladium-Catalyzed Thioetherification of Aryl Bromides and Iodides  

PubMed Central

The cross-coupling reaction of aryl bromides and iodides with aliphatic and aromatic thiols catalyzed by palladium complexes of the bisphosphine ligand CyPF-tBu (1) is reported. Reactions occur in excellent yields, broad scope, high tolerance of functional groups and with turnover numbers that exceed those of previous catalysts by two or three orders of magnitude. These couplings of bromo- and iodoarenes are more efficient than the corresponding reactions of chloroarenes and could be conducted with less catalyst loading and/or milder reaction conditions. Consequently, limitations regarding scope and functional group tolerance previously reported in the coupling of aryl chlorides are now overcome.

Fernandez-Rodriguez, Manuel A.; Hartwig, John F.

2010-01-01

442

Fatty acid-based polyurethane films for wound dressing applications.  

PubMed

Fatty acid-based polyurethane films were prepared for use as potential wound dressing material. The polymerization reaction was carried out with or without catalyst. Polymer films were prepared by casting-evaporation technique with or without crosslink-catalyst. The film prepared from uncatalyzed reaction product with crosslink-catalyst gave slightly higher crosslink density. The mechanical tests showed that, the increase in the tensile strength and decrease in the elongation at break is due to the increase in the degree of crosslinking. All films were flexible, and resisted to acid solution. The films prepared without crosslink-catalyst were more hydrophilic, absorbed more water. The highest permeability values were generally obtained for the films prepared without crosslink catalyst. Both the direct contact method and the MMT test were applied for determination of cytotoxicity of polymer films and the polyurethane film prepared from uncatalyzed reaction product without crosslink-catalyst showed better biocompatibility property, closest to the commercial product, Opsite. PMID:18839285

Gultekin, Guncem; Atalay-Oral, Cigdem; Erkal, Sibel; Sahin, Fikret; Karastova, Djursun; Tantekin-Ersolmaz, S Birgul; Guner, F Seniha

2008-10-07

443

Oriented and selective enzyme immobilization on functionalized silica carrier using the cationic binding module Z basic2: design of a heterogeneous D-amino acid oxidase catalyst on porous glass.  

PubMed

D-amino acid oxidase from Trigonopsis variabilis (TvDAO) is applied in industry for the synthesis of pharmaceutical intermediates. Because free TvDAO is extremely sensitive to exposure to gas-liquid interfaces, biocatalytic processing is usually performed with enzyme immobilizates that offer enhanced stability under bubble aeration. We herein present an "Immobilization by Design" approach that exploits engineered charge complementarity between enzyme and carrier to optimize key features of the immobilization of TvDAO. A fusion protein between TvDAO and the positively charged module Z(basic2) was generated, and a corresponding oppositely charged carrier was obtained by derivatization of mesoporous glass with 3-(trihydroxysilyl)-1-propane-sulfonic acid. Using 250 mM NaCl for charge screening at pH 7.0, the Z(basic2) fusion of TvDAO was immobilized directly from E. coli cell extract with almost absolute selectivity and full retention of catalytic effectiveness of the isolated enzyme in solution. Attachment of the homodimeric enzyme to the carrier was quasi-permanent in low-salt buffer but fully reversible upon elution with 5 M NaCl. Immobilized TvDAO was not sensitive to bubble aeration and received substantial (? tenfold) stabilization of the activity at 45°C as compared to free enzyme, suggesting immobilization via multisubunit oriented interaction of enzyme with the insoluble carrier. The Z(basic2) enzyme immobilizate was demonstrated to serve as re-usable heterogeneous catalyst for D-amino acid oxidation. Z(basic2) -mediated binding on a sulfonic acid group-containing glass carrier constitutes a generally useful strategy of enzyme immobilization that supports transition from case-specific empirical development to rational design. PMID:22249953

Bolivar, Juan M; Nidetzky, Bernd

2012-01-17

444

A general method for the synthesis of monodisperse hollow inorganic-organic hybrid microspheres with interior functionalized poly(methacrylic acid) shells.  

PubMed

Hollow inorganic-organic hybrid microspheres, such as silica, titania, and zirconia, with interior poly(methacrylic acid) (PMAA) functionalized shell were synthesized by a general method containing a two-stage reaction. The hollow inorganic shell-layer with interior polymeric component was formed over the PMAA template during the second-stage controlled hydrolysis of inorganic precursors together with disintegration of PMAA cores and adhering to the interior wall of the silica during the drying process due to the capillary force as well as the competitive hydrogen bond interaction. In this process, PMAA microspheres were prepared by distillation precipitation polymerization of methacrylic acid (MAA) in acetonitrile as the first-stage reaction. The present work elaborately investigated the effects of the reaction conditions, including the amount of the tetraethyl orthosilicate (TEOS) precursors and the amount of ammonium hydroxide catalyst on the morphology and structure of the resultant hollow composite microspheres, which were characterized by transmission electron microscopy (TEM), Fourier-transform infrared spectra (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption-desorption. PMID:22218343

Liu, Bin; Yan, Enwei; Zhang, Xu; Yang, Xinlin; Bai, Feng

2011-12-19

445

Carbon nanotube-supported gold nanoparticles as efficient catalysts for selective oxidation of cellobiose into gluconic acid in aqueous medium.  

PubMed

Gold nanoparticles loaded on nitric acid-pretreated carbon nanotubes are efficient for the selective oxidation of cellobiose by molecular oxygen to gluconic acid in aqueous medium without pH control; a gluconic acid yield of 80% has been obtained at 145 degrees C. PMID:19921022

Tan, Xuesong; Deng, Weiping; Liu, Mi; Zhang, Qinghong; Wang, Ye

2009-10-14

446

Determination of crude protein in animal feed, forage, grain, and oilseeds by using block digestion with a copper catalyst and steam distillation into boric acid: collaborative study.  

PubMed

A collaborative study was conducted to evaluate the repeatability and reproducibility of an extension of AOAC Official Method 991.20, Nitrogen (Crude) in Milk, to animal feed, forage (plant tissue), grain, and oilseed materials. Test portions are digested in an aluminum block at 420 degrees C in sulfuric acid with potassium sulfate and a copper catalyst. Digests are cooled and diluted, and concentrated sodium hydroxide is added to neutralize the acid and make the digest basic; the liberated ammonia is distilled by using steam distillation. The liberated ammonia is trapped in a weak boric acid solution and titrated with a stronger standardized acid, hydrochloric acid; colorimetric endpoint detection is used. Fourteen blind samples were sent to 13 collaborators in the United States, Denmark, Sweden, Germany, and the United Kingdom. Recoveries of nitrogen from lysine, tryptophan, and acetanilide were 86.8, 98.8, and 100.1%, respectively. The within-laboratory relative standard deviation (RSDr, repeatability) ranged from 0.40 to 2.38% for crude protein. The among-laboratories (including within-) relative standard deviation (RSD(R), reproducibility) ranged from 0.44 to 2.38%. It is recommended that the method be adopted First Action by AOAC INTERNATIONAL. A lower concentration (1% H3BO3) of trapping solution was compared with the concentration specified in the original protocol (4% H3BO3) and was found comparable for use in an automatic titration system in which titration begins automatically as soon as distillation starts. The Study Directors recommend that 1% H3BO3 as an optional alternative to 4% boric acid trapping solution be allowed for automatic titrators that titrate throughout the distillation. PMID:11990013

Thiex, Nancy J; Manson, Harold; Andersson, Shirley; Persson, Jan-Ake

447

o-Benzenedisulfonimide and its chiral derivative as Brønsted acids catalysts for one-pot three-component Strecker reaction. Synthetic and mechanistic aspects.  

PubMed

o-Benzenedisulfonimide (OBS) has efficiently catalysed the one-pot three-component reaction of ketones and aromatic amines with trimethylsilyl cyanide (TMSCN) giving the corresponding ?-amino nitriles in excellent yields (23 examples; average yield 85%). Reaction conditions were very simple, green and efficient. Theoretical calculations have allowed us to explain the mechanism of this reaction which has been found to take place in two phases; the first consists of the nucleophilic addition of the aniline to the ketone and the subsequent dehydration to an imine; the second one consists of the formal addition of cyanide anion to the protonated imine. OBS acts in all steps of this mechanism. Without an acid catalyst, the reaction mechanism is more simple but barriers are sensibly higher. A chiral derivative of OBS was also used and gave fairly good results. PMID:22527016

Barbero, Margherita; Cadamuro, Silvano; Dughera, Stefano; Ghigo, Giovanni

2012-04-24

448

Synthesis of 3,4-Dihydropyrimidin-2(1H)-Ones and Their Corresponding 2(1H)Thiones Using Trichloroacetic Acid as a Catalyst under Solvent-Free Conditions  

PubMed Central

Trichloroacetic acid was found to be a convenient catalyst for the synthesis of 3,4-dihydropyrimidin-2-(1H)-ones and their corresponding 2(1H)-thiones through a one-pot three-component reaction of aldehydes, alkyl acetoacetate, and urea or thiourea at 70°C under solvent-free conditions.

Karimi-Jaberi, Zahed; Moaddeli, Mohammad Sadegh

2012-01-01

449

Methanation Catalysts.  

National Technical Information Service (NTIS)

Although all the Group VIII metals are catalytically active in the hydrogenation of carbon monoxide to form methane ('methanation'), nickel, despite extensive investigations of alternative materials, remains the favored catalyst for the reaction by virtue...

G. H. Watson

1980-01-01

450

Methanation Catalysts.  

National Technical Information Service (NTIS)

Although all the Group VIII metals are catalytically active in the hydrogenation of carbon monoxide to form methane (methanation), nickel, despite extensive investigations of alternative materials, remains the favored catalyst for the reaction by virtue o...

G. H. Watson

1980-01-01

451

Metal chelate catalysts for fuel cells  

NASA Astrophysics Data System (ADS)

Various modified forms of several organometallic chelate compounds were synthesized and tested for their activity and stability as oxygen reduction electrocatalysts in sulfuric acid electrolyte. The most active catalysts found were cobalt tetraazaannulene (CoTAA), iron phthalocyanine (FePc) and cobalt tetraphenylporphyrin (CoTPP). However, these catalysts have limited stability in strong acids.

Darby, R.; Yamana, M.; Dhar, H.; White, R.

1982-10-01

452

Metal chelate catalysts for fuel cells  

Microsoft Academic Search

Various modified forms of several organometallic chelate compounds were synthesized and tested for their activity and stability as oxygen reduction electrocatalysts in sulfuric acid electrolyte. The most active catalysts found were cobalt tetraazaannulene (CoTAA), iron phthalocyanine (FePc) and cobalt tetraphenylporphyrin (CoTPP). However, these catalysts have limited stability in strong acids.

R. Darby; M. Yamana; H. Dhar; R. White

1982-01-01

453

FRETmatrix: a general methodology for the simulation and analysis of FRET in nucleic acids  

PubMed Central

Förster resonance energy transfer (FRET) is a technique commonly used to unravel the structure and conformational changes of biomolecules being vital for all living organisms. Typically, FRET is performed using dyes attached externally to nucleic acids through a linker that complicates quantitative interpretation of experiments because of dye diffusion and reorientation. Here, we report a versatile, general methodology for the simulation and analysis of FRET in nucleic acids, and demonstrate its particular power for modelling FRET between probes possessing limited diffusional and rotational freedom, such as our recently developed nucleobase analogue FRET pairs (base–base FRET). These probes are positioned inside the DNA/RNA structures as a replacement for one of the natural bases, thus, providing unique control of their position and orientation and the advantage of reporting from inside sites of interest. In demonstration studies, not requiring molecular dynamics modelling, we obtain previously inaccessible insight into the orientation and nanosecond dynamics of the bases inside double-stranded DNA, and we reconstruct high resolution 3D structures of kinked DNA. The reported methodology is accompanied by a freely available software package, FRETmatrix, for the design and analysis of FRET in nucleic acid containing systems.

Preus, S?ren; Kilsa, Kristine; Miannay, Francois-Alexandre; Albinsson, Bo; Wilhelmsson, L. Marcus

2013-01-01

454

A Catalyst System for Polyurethane Propellants.  

National Technical Information Service (NTIS)

The patent application relates to a two component catalyst system for use in promoting the cure of polyurethane propellants, composed of zinc oxide as the first component and either acetylacetone, linoleic acid, alpha-bromotetradecanoic acid or p-toluensu...

A. E. Oberth

1976-01-01

455

Synthesis of methacrylic acid by selective oxidation of isobutane, catalysed by Keggin-type polyoxometalates: relationship between catalytic performance, reaction conditions and chemical–physical features of the catalyst  

Microsoft Academic Search

The ammonium salt of 12-molybdophosphoric acid, (NH4)3PMo12O40 (polyoxometalate, POM), having the Keggin-type structure was prepared and tested as a heterogeneous catalyst for the selective oxidation of isobutane to methacrylic acid. This reaction might represent an alternative to the current industrial process for methyl methacrylate production, the acetone–cyanohydrin process, which is characterized by a no longer acceptable environmental impact. The POM

Fabrizio Cavani; Roberto Mezzogori; Anne Pigamo; Ferruccio Trifirò

2000-01-01

456

Results of catalyst testing using iron-based catalysts  

SciTech Connect

As coal liquefaction catalysts, iron-based products are generally inferior to the more expensive molybdenum, cobalt, or nickel-based materials. However, the lower costs of production and recovery (or in the case of some iron catalysts, non-recovery) give the iron-based materials a potential economic advantage over the more efficient precious and semi-precious metal catalysts for this application. Recent research has shown that a number of different iron-containing materials can be successfully utilized as coal liquefaction catalysts or as catalyst. Pyrrhotite (Fe[sub 1-x]S) or a similar iron-sulfide phase is commonly believed to be the active catalyst in coal liquefaction and model compound pyrolysis reactions, although no specific phase has been yet been isolated as the actual catalyst species. The active iron-containing catalyst is usually generated in situ from an iron-oxide precursor and an elemental sulfur source under reducing conditions in the reactor vessel. Most research has concentrated on the use of common iron-oxide phases such as hematite or goethite (and their derivatives) as the iron-bearing precursor, or on non-specific iron materials produced by the reaction of various iron salts and compounds in the coal or liquefaction reactor. To our knowledge there has been no systematic effort to determine the optimum iron-containing precursor phase for producing active coal liquefaction catalysts, despite the fact that there are over ten iron-(hydroxy)oxide phases which can be easily synthesized in the laboratory. We have undertaken a systematic study to identify the most active iron-oxide catalyst precursor phases, the co-catalysts, and the coal pretreatments which will provide optimum yields in coal liquefaction processes.

Linehan, J.C.; Darab, J.G.; Matson, D.W.

1993-03-01

457

Results of catalyst testing using iron-based catalysts  

SciTech Connect

As coal liquefaction catalysts, iron-based products are generally inferior to the more expensive molybdenum, cobalt, or nickel-based materials. However, the lower costs of production and recovery (or in the case of some iron catalysts, non-recovery) give the iron-based materials a potential economic advantage over the more efficient precious and semi-precious metal catalysts for this application. Recent research has shown that a number of different iron-containing materials can be successfully utilized as coal liquefaction catalysts or as catalyst. Pyrrhotite (Fe{sub 1-x}S) or a similar iron-sulfide phase is commonly believed to be the active catalyst in coal liquefaction and model compound pyrolysis reactions, although no specific phase has been yet been isolated as the actual catalyst species. The active iron-containing catalyst is usually generated in situ from an iron-oxide precursor and an elemental sulfur source under reducing conditions in the reactor vessel. Most research has concentrated on the use of common iron-oxide phases such as hematite or goethite (and their derivatives) as the iron-bearing precursor, or on non-specific iron materials produced by the reaction of various iron salts and compounds in the coal or liquefaction reactor. To our knowledge there has been no systematic effort to determine the optimum iron-containing precursor phase for producing active coal liquefaction catalysts, despite the fact that there are over ten iron-(hydroxy)oxide phases which can be easily synthesized in the laboratory. We have undertaken a systematic study to identify the most active iron-oxide catalyst precursor phases, the co-catalysts, and the coal pretreatments which will provide optimum yields in coal liquefaction processes.

Linehan, J.C.; Darab, J.G.; Matson, D.W.

1993-03-01

458

Sequential hydrodistension and intravesical instillation of hyaluronic acid under general anaesthesia for treatment of refractory interstitial cystitis: a pilot study  

Microsoft Academic Search

Pilot study looking at the combination of general anaesthetic hydrodistension and intravesical hyaluronic acid for treatment\\u000a of refractory interstitial cystitis. Twenty-three treatment refractory patients were recruited with an average age 53.4 years.\\u000a All underwent general anaesthetic cystoscopy, hydrodistension and instillation of hyaluronic acid (40 mg\\/50 ml). The bladder\\u000a was then subsequently drained with the patient awake. Two initial treatments were carried out a

Imran Ahmad; Nalagatla Sarath Krishna; Robert N. Meddings

2008-01-01

459

ZrO 2 –SiO 2 Mixed Oxides Xerogel and Aerogel as Solid Acid Catalysts for Solvent Free Isomerization of ?-Pinene and Dehydration of 4Methyl2Pentanol  

Microsoft Academic Search

\\u000a Abstract  Sulfated and non-sulfated ZrO2–SiO2 mixed oxide xerogel and aerogel samples having varied Zr\\/Si molar ratio were evaluated as solid acid catalysts for the isomerization\\u000a of ?-pinene and dehydration of 4-methyl-2-pentanol. Sulfation resulted into enhancement in the catalytic activity of both\\u000a xerogel and aerogel samples towards the studied reactions. For example, sulfated catalysts showed 86–98% conversion of ?-pinene\\u000a and 8–35% conversion

Kalpesh B. Sidhpuria; Beena Tyagi; Raksh V. Jasra

2011-01-01

460

Catalytic conversion of glucose to 5-hydroxymethylfurfural over SO 4 2?\\/ZrO 2 and SO 4 2?\\/ZrO 2–Al 2O 3 solid acid catalysts  

Microsoft Academic Search

SO42?\\/ZrO2 and SO42?\\/ZrO2–Al2O3 catalysts were prepared by impregnation of Zr(OH)4 and Zr(OH)4–Al(OH)3 with ethylene dichloride solution of chlorosulfonic acid, and characterized by ICP-AES, BET, XRD, NH3-TPD, CO2-TPD and FTIR of adsorbed pyridine. The catalysts were used in the catalytic conversion of glucose to 5-hydroxymethylfurfural. An optimized 5-hydroxymethylfurfural yield of 47.6% was obtained within 4h at 403K over SO42?\\/ZrO2–Al2O3 with Zr–Al

Hongpeng Yan; Yu Yang; Dongmei Tong; Xi Xiang; Changwei Hu

2009-01-01

461

Preparation and characterization of core–shell structured catalysts using Pt x Pd y as active shell and nano-sized Ru as core for potential direct formic acid fuel cell application  

Microsoft Academic Search

Carbon-supported core–shell structured Ru@PtxPdy\\/C catalysts with PtxPdy as shell and nano-sized Ru as core are prepared by a successive reduction procedure. The catalysts are extensively characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The formic acid oxidation activity of Ru@PtxPdy\\/C varies with the varying Pt:Pd atomic ratio. The peak oxidation potential on Ru@Pt1Pd2\\/C shifts

Haili Gao; Shijun Liao; Jianhuang Zeng; Yichun Xie; Dai Dang

2011-01-01

462

Assessing the acid strength of solid acid catalysts with the use of linear free energy relationship: H\\/D exchange with substituted benzene derivatives  

Microsoft Academic Search

The acid strength of solid acid materials can be assessed using the linear free energy relationship, applying the Hammett–Brown equation (logkX\\/kH=??+) for the H\\/D exchange with substituted benzenes. The magnitude of the ? varies for different solid acid materials (Amberlyst-15, zeolite HUSY, K-10 montmorillonite, and niobic acid) and is associated with the degree of proton transfer in the transition state.

Valter L. C. Gonçalves; Rogério C. Rodrigues; Rodolfo Lorençato; Claudio J. A. Mota

2007-01-01

463

An efficient procedure for protection of carbonyls catalyzed by sulfamic acid  

Microsoft Academic Search

Sulfamic acid (H2NSO3H) has been used as an efficient and recyclable catalyst for acetalization and ketalization between carbonyl compounds and diols. This system is reasonably general and can be applied to converting several carbonyl compounds to the corresponding acetals and ketals using neopentyl glycol and other diols as protection reagents. The use of an inexpensive, green and stable catalyst, convenient

Bo Wang; Yanlong Gu; Guoyong Song; Tao Yang; Liming Yang; Jishuan Suo

2005-01-01

464

Catalytic activity in individual cracking catalyst particles imaged throughout different life stages by selective staining.  

PubMed

Fluid catalytic cracking (FCC) is the major conversion process used in oil refineries to produce valuable hydrocarbons from crude oil fractions. Because the demand for oil-based products is ever increasing, research has been ongoing to improve the performance of FCC catalyst particles, which are complex mixtures of zeolite and binder materials. Unfortunately, there is limited insight into the distribution and activity of individual zeolitic domains at different life stages. Here we introduce a staining method to visualize the structure of zeolite particulates and other FCC components. Brønsted acidity maps have been constructed at the single particle level from fluorescence microscopy images. By applying a statistical methodology to a series of catalysts deactivated via industrial protocols, a correlation is established between Brønsted acidity and cracking activity. The generally applicable method has clear potential for catalyst diagnostics, as it determines intra- and interparticle Brønsted acidity distributions for industrial FCC materials. PMID:22024882

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

2011-09-18

465

A general solution for unstable boronic acids: slow-release cross-coupling from air-stable MIDA boronates.  

PubMed

Many boronic acids, including 2-heterocyclic, vinyl, and cyclopropyl derivatives, are inherently unstable, which can limit their benchtop storage and/or efficient cross-coupling. We herein report the first general solution to this problem: in situ slow release of unstable boronic acids from the corresponding air-stable MIDA boronates. This remarkably general approach has transformed all three classes of these unstable boronic acids into shelf-stable and highly effective building blocks for cross-coupling with a wide range of aryl and heteroaryl chlorides. PMID:19405470

Knapp, David M; Gillis, Eric P; Burke, Martin D

2009-05-27

466

Poly(4-vinylpyridine) supported acidic ionic liquid: A novel solid catalyst for the efficient synthesis of 2,3-dihydroquinazolin-4(1H)-ones under ultrasonic irradiation.  

PubMed

A novel poly(4-vinylpyridine) supported acidic ionic liquid catalyst was synthesized by the reaction of 4-vinylpyridine with 1,3-propanesultone, followed by the polymerization and the addition of the heteropolyacid. Due to the combination of polymer features and ionic liquid, it acted as a heterogeneous catalyst to effectively catalyze the cyclocondensation reaction of anthranilamide with aldehydes under ultrasonic irradiation and afforded the corresponding 2,3-dihydro-4(1H)-quinazolinones compounds in good to excellent yields. In addition, the catalyst could be easily recovered by the filtration and reused six times without significant loss of catalytic activity. More importantly, the use of ultrasonic irradiation can obviously accelerate the reaction. PMID:23751459

Wang, Junke; Zong, Yingxiao; Fu, Rugang; Niu, Yuying; Yue, Guoren; Quan, Zhengjun; Wang, Xicun; Pan, Yi

2013-05-29

467

Evaluation of the acid-base surface properties of several oxides and supported metal catalysts by means of model reactions  

Microsoft Academic Search

Acid-base properties of oxides (Al2O3, SiO2, ZrO2, CeO2, MgO, SiO2?Al2O3 and CeO2?Al2O3) were investigated by means of model reactions: 3,3-dimethylbut-1-ene isomerization (33DMB1), methylene cyclohexane isomerization (MECH), cyclohexanol conversion (CHOL) and CO2 chemisorption at room temperature. The effect of acid (Cl?, SO2?4) and basic (K+) promoters on certain oxides (Al2O3, ZrO2) was also studied. Surface acidity was evaluated by means of

Dominique Martin; Daniel Duprez

1997-01-01

468

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.

1999-08-01

469

Reforming catalyst  

SciTech Connect

This patent describes a catalyst useful for reforming a naphtha feed at high severity reforming conditions. It comprises the metals, platinum, rhenium and iridium on a refractory porous inorganic oxide support, the support consisting essentially of alumina, wherein the concentration by weight of each of the metals platinum and rhenium is at least 0.1 percent and iridium at least 0.15 percent and at least one of the metals is present in a concentration of at least 0.3 percent, and the sum-total; concentration of the metals is greater than 0.9 percent, and wherein each catalyst particle contains all three of the metals platinum, rhenium and iridium. This patent also describes this composition wherein the catalyst contains from about 0.1 percent to about 3 percent of a halogen and from about 0.05 percent to about 0.02 percent sulfur.

Baird, W.C. Jr.; Swan, G.A.

1991-11-19

470

One-pot synthesis of tryptophols with mesoporous MCM-41 silica catalyst functionalized with sulfonic acid groups  

Microsoft Academic Search

Mesoporous MCM-41 silica functionalized with sulfonic acid groups (SO3H-MCM-41) was prepared through the condensation of MCM-41 with benzyl alcohol followed with sulfonation, which was characterized by XRD, FT-IR and nitrogen adsorption analyses. One-pot Fischer indole synthesis of tryptophols under the catalysis of SO3H-MCM-41 was reported with phenylhydrazine hydrochlorides and 2,3-dihydrofuran. The acidity and amount of sulfur loading were surveyed and

Xiaoyan Sheng; Jianrong Gao; Liang Han; Yixia Jia; Weijian Sheng

2011-01-01

471

Effect of sulfation methods on TiO 2–SiO 2 sol–gel catalyst acidity  

Microsoft Academic Search

A series of x TiO2–SiO2 (x=1.7, 4.0 and 6.7wt.% TiO2) binary mixed oxides was prepared by a sol–gel method in acidic and basic conditions. In order to upgrade the acidic properties of the obtained solids, their sulfation was carried out in three different ways: (1) by in situ (H2SO4 was admixed with the gel), (2) impregnating the dried solids with

T López; P Bosch; F Tzompantzi; R Gómez; J Navarrete; E López-Salinas; M. E Llanos

2000-01-01

472

Acid zeolites as catalysts in organic reactions. Chemoselective Friedel-Crafts alkylation of benzene and toluene with cinnamyl alcohol  

Microsoft Academic Search

Alkylation of benzene and toluene with cinnamyl alcohol has been carried out in the presence of a series of acid Y faujasites with three levels of Na+-to-H+ exchange (HY-21, HY-50 and HY-100) and with different framework Si-to-Al ratio (HY-D1, HY-D2 and HY-D3). This system provides a good example of the possibilities of tunable acidity in zeolites to control a chemical

Elvira Armengol; Avelino Corma; Hermenegildo García; Primo Jaime

1995-01-01

473

The identification of the acid–base catalyst of ?-arabinofuranosidase from Geobacillus stearothermophilus T-6, a family 51 glycoside hydrolase  

Microsoft Academic Search

The ?-L-arabinofuranosidase from Geobacillus stearothermophilus T-6 (AbfA T-6) belongs to the retaining family 51 glycoside hydrolases. The conserved Glu175 was proposed to be the acid–base catalytic residue. AbfA T-6 exhibits residual activity towards aryl ?-D-xylopyranosides. This phenomenon was used to examine the catalytic properties of the putative acid–base mutant E175A. Data from kinetic experiments, pH profiles, azide rescue, and the

Dalia Shallom; Valery Belakhov; Dmitry Solomon; Sara Gilead-Gropper; Timor Baasov; Gil Shoham; Yuval Shoham

2002-01-01

474

Efficient combination of promoter and catalyst for chromic acid oxidation of propan-2-ol to acetone in aqueous acid media at room temperature.  

PubMed

Oxidation of propan-2-ol to acetone was carried out in aqueous media at room temperature. The effect of promoter (PA, bpy, phen), micellar catalyst (SDS, CPC, TX-100) and their combination has been studied. The reactions were performed under the condition [Propan-2-ol]T?[Cr(VI)]T at 30°C. Then kobs and half life of all the reaction were determined to identify which promoter and which combination are the most effective for this oxidation. Among the promoters phen accelerates the reaction most in aqueous media. In absence of promoters anionic surfactant SDS increases the rate more effectively than neutral surfactant TX-100. CPC retards the rate in comparison to aqueous media. The rate of the oxidation is highest in presence of the combination of bpy and SDS. PMID:23123236

Mukherjee, Kakali; Saha, Rumpa; Ghosh, Aniruddha; Ghosh, Sumanta K; Saha, Bidyut

2012-10-12

475

Necessary conditions for entanglement catalysts  

SciTech Connect

Given a pure state transformation {psi}{yields}{phi} restricted to entanglement-assisted local operations with classical communication, we determine a lower bound for the dimension of a catalyst allowing that transformation. Our bound is stated in terms of the generalized concurrence monotones (the usual concurrence of two qubits is one such monotone). We further provide tools for deriving further conditions upon catalysts of pure state transformations.

Sanders, Yuval Rishu; Gour, Gilad [Department of Mathematics and Statistics and Institute for Quantum Information Science, University of Calgary, 2500 University Drive NW, Calgary, Alberta, T2N 1N4 (Canada)

2009-05-15

476

Ferrite Catalyst.  

National Technical Information Service (NTIS)

According to this invention, a catalyst consisting of a spinel-type ferrite and having an apparent density of 3.0 g/cm exp 3 can be produced by sintering a mixture of lamellar alpha -Fe sub 2 O sub 3 and other metal oxides. Partly because of the use of a ...

K. Kugimiya Y. Terada

1983-01-01

477

Cracking catalyst  

Microsoft Academic Search

A metal combustion promoter is introduced to the circulating inventory of catalyst in a catalytic cracking unit as a mixture of particles rich in metal with particles free of metal such that the net concentration of metal in the mixture is about 1 to 10 ppm. According to a preferred embodiment the particles rich in metal contain about 50 ppm

Chester

1980-01-01

478

General Acid\\/Base Catalysis in the Active Site of Escherichia coli Thioredoxin †  

Microsoft Academic Search

Enzymic catalysts of thiol:disulfide oxidoreduction contain two cysteine residues in their active sites. Another common residue is an aspartate (or glutamate), the role of which has been unclear. Escherichia coli thioredoxin (Trx) is the best characterized thiol:disulfide oxidoreductase, and in Trx these three active-site residues are Cys32, Cys35, and Asp26. Structural analyses had indicated that the carboxylate of Asp26 is