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1

Polypyrrole based strong acid catalyst for acetalization  

NASA Astrophysics Data System (ADS)

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

Liang, Xuezheng; Cheng, Yuxiao; Qi, Chenze

2011-09-01

2

Carbocations as Lewis acid catalysts in Diels-Alder and Michael addition reactions.  

PubMed

In general, Lewis acid catalysts are metal-based compounds that owe their reactivity to a low-lying empty orbital. However, one potential Lewis acid that has received negligible attention as a catalyst is the carbocation. We have demonstrated the potential of the carbocation as a highly powerful Lewis acid catalyst for organic reactions. The stable and easily available triphenylmethyl (trityl) cation was found to be a highly efficient catalyst for the Diels-Alder reaction for a range of substrates. Catalyst loadings as low as 500?ppm, excellent yields, and good endo/exo selectivities were achieved. Furthermore, by changing the electronic properties of the substituents on the tritylium ion, the Lewis acidity of the catalyst could be tuned to control the outcome of the reaction. The ability of this carbocation as a Lewis acid catalyst was also further extended to the Michael reaction. PMID:24375806

Bah, Juho; Franzén, Johan

2014-01-20

3

A QM/MM study of Kemptide phosphorylation catalyzed by protein kinase A. The role of Asp166 as a general acid/base catalyst.  

PubMed

In this work a theoretical study of the ?-phosphoryl group transfer from ATP to Ser17 of the synthetic substrate Kemptide (LRRASLG) in protein kinase A (PKA) has been carried out with a solvated model of the PKA-Mg2ATP-Kemptide system based on the X-ray crystallographic structure. We have used high levels (B3LYP/MM and MP2/MM) of theory to determine the overall reaction paths of the so-called concerted loose mechanism trying to clarify some aspects of that mechanism still under debate. Our calculations demonstrate for the first time in a complete model of the ternary system the viability of the final step of the catalytic mechanism in which the protonation of the phosphokemptide product by Asp166 takes place. Asp166 is a base catalyst that abstracts the H?Ser17 of Kemptide thus facilitating the phosphoryl transfer, but it also acts as an acid catalyst by donating the proton just accepted from Ser17 to the O2?ATP atom of the phosphoryl group. PMID:25535906

Pérez-Gallegos, Ayax; Garcia-Viloca, Mireia; González-Lafont, Àngels; Lluch, José M

2015-02-01

4

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

5

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

PubMed

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

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

2015-03-01

6

Cyclobutane amino acids and peptidomimetics, parallel catalyst screening for aziridination.  

E-print Network

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

Li, Shih-ming

2012-01-01

7

Acid monolayer functionalized iron oxide nanoparticle catalysts  

NASA Astrophysics Data System (ADS)

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

Ikenberry, Myles

8

Catalyst and electrode research for phosphoric acid fuel cells  

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

9

The Effect of Supercritical Fluids on Solid Acid Catalyst Alkylation  

SciTech Connect

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

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

2002-05-01

10

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 ...

11

Surface acidity and degree of carburization of modified silver catalysts  

SciTech Connect

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

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

1993-11-10

12

Method for producing iron-based acid catalysts  

SciTech Connect

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

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

1998-04-01

13

Method for isomerizing olefins using acidic composite catalysts  

SciTech Connect

This patent describes a method for isomerizing olefins comprising the steps of contacting at least one olefin with a catalyst composite comprising a perfluorinated-polymersulfonic acid and an anion-stabilizing agent and recovering the isomerized olefins.

Farcasiu, D.

1987-06-09

14

Solid acid catalysts: Stain and shine  

NASA Astrophysics Data System (ADS)

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

Chen, Peng

2011-11-01

15

Enantioselective Iodolactonization of Disubstituted Olefinic Acids Using a Bifunctional Catalyst  

PubMed Central

The enantioselective iodolactonizations of a series of diversely-substituted olefinic carboxylic acids are promoted by a BINOL-derived, bifunctional catalyst. Reactions involving 5-alkyl- and 5-aryl-4(Z)-pentenoic acids and 6-alkyl- and 6-aryl-5(Z)-hexenoic acids provide the corresponding ?- and ?-lactones having stereogenic C–I bonds in excellent yields and >97:3 er. Significantly, this represents the first organocatalyst that promotes both bromo- and iodolactonization with high enantioselectivities. The potential of this catalyst to induce kinetic resolutions of racemic unsaturated acids is also demonstrated. PMID:23199100

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

2012-01-01

16

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

PubMed

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

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

2012-01-23

17

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

18

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

PubMed Central

We report an approach to the high-throughput screening of asymmetric oxidation catalysts. The strategy is based on application of the one-bead-one-compound library approach, wherein each of our catalyst candidates is based on a peptide scaffold. For this purpose we rely on a recently developed catalytic cycle that employs an acid-peracid shuttle. In order to implement our approach, we developed a compatible linker and demonstrated that the library format is amenable to screening and sequencing of catalysts employing partial Edman degradation and MALDI mass spectrometry analysis. The system was applied to the discovery (and re-discovery) of catalysts for the enantioselective oxidation of a cyclohexene derivative. The system is now poised for application to unprecedented substrate classes for asymmetric oxidation reactions. PMID:21417485

Lichtor, Phillip A.; Miller, Scott J.

2011-01-01

19

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

PubMed

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

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

2014-07-23

20

Organometallic catalysts for primary phosphoric acid fuel cells  

NASA Technical Reports Server (NTRS)

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

Walsh, Fraser

1987-01-01

21

Functionalized carbon nanofibers as solid-acid catalysts for transesterification.  

PubMed

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

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

2013-09-01

22

Replacement of liquid HâSOâ and HF with solid acid catalysts: A study of mixed metal phosphates as solid acid catalysts  

Microsoft Academic Search

The primary purpose of this LDRD was to identify and optimize materials as solid acid catalysts for the replacement of environmentally hazardous liquid acids such as HâSOâ and HF which are used as catalysts in both the petroleum and chemical industries. Liquid acids have significant safety, environmental and engineering difficulties associated with their use in process chemistry. Special equipment\\/materials need

N. B. Jackson; T. M. Nenoff; S. G. Thoma; S. D. Kohler

1997-01-01

23

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

Microsoft Academic Search

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

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

2001-01-01

24

Acid activated montmorillonite as catalysts in methyl esterification reactions of lauric acid.  

PubMed

The catalytic activity of acid activated montmorillonite in the esterification of free fatty acids (FFA) is reported. Standard Montmorillonite (MMT) type STx-1 provided by the Clay Mineral Society repository was activated using phosphoric, nitric and sulphuric acids under different conditions and the resulting materials were characterized and evaluated as catalysts in the methyl esterification of lauric acid. Blank reactions carried out in the absence of any added catalyst presented conversions of 32.64, 69.79 and 79.23%, for alcohol:lauric acid molar ratios of 60:1, 12:1 and 6:1, respectively. In the presence of the untreated clay and using molar ratios of 12:1 and 6:1 with 12% of catalyst, conversions of 70.92 and 82.30% were obtained, respectively. For the acid activated clays, conversions up to 93.08% of lauric acid to methyl laurate were obtained, much higher than those observed for the thermal conversion or using untreated montmorillonite. Relative good correlations were observed between the catalytic activity and the development of acid sites and textural properties of the resulting materials. Therefore, a simple acid activation was able to improve the catalytic activity and produce clay catalysts that are environmental friendly, cost effective, noncorrosive and reusable. PMID:22975784

Zatta, Leandro; Ramos, Luiz Pereira; Wypych, Fernando

2012-01-01

25

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

PubMed

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

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

2013-02-01

26

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

NASA Technical Reports Server (NTRS)

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

Mcalister, A. J.

1981-01-01

27

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

NASA Technical Reports Server (NTRS)

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

Mcalister, A. J.

1980-01-01

28

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

NASA Technical Reports Server (NTRS)

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

Mcalister, A. J.

1981-01-01

29

Prompt gamma activation analysis of solid acid catalysts  

SciTech Connect

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

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

1994-12-31

30

Cathode catalysts for primary phosphoric acid fuel cells  

NASA Technical Reports Server (NTRS)

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

1981-01-01

31

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

Microsoft Academic Search

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

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

2009-01-01

32

Different solid acid catalysts influence on properties and chemical composition change of upgrading bio-oil  

Microsoft Academic Search

Several solid acid catalysts are prepared and compared in upgrading bio-oil using ethanol and acetic acid as raw materials through the catalytic esterification reaction model. The SO42?\\/SiO2–TiO2 catalyst in the optimum experimental conditions achieved higher catalytic activity. The bio-oil was stabilized by ester reaction over SO42?\\/SiO2–TiO2 catalyst in the conditioned experiment with lowered dynamic viscosity and enhanced fluidity, which was

Min Song; Zhaoping Zhong; Jiajia Dai

2010-01-01

33

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

34

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

PubMed

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

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

2013-04-01

35

Acidity studies of fluid catalytic cracking catalysts by microcalorimetry and infrared spectroscopy  

Microsoft Academic Search

The acidic properties of a USY-based fluid catalytic cracking catalyst steamed at various severities and amorphous silica-alumina were investigated by microcalorimetry and infrared spectroscopy using pyridine adsorption at 473 K. Microcalorimetric measurements of the differential heat of pyridine adsorption versus adsorbate coverage revealed a heterogeneous acid site distribution for the catalysts. Besides showing the expected progressive decrease in the number

D. Chen; S. Sharma; J. A. Dumesic; N. Cardona Martinez; V. A. Bell; G. D. Hodge; R. J. Madon

1992-01-01

36

Generalization of ACID Properties Brahim Medjahed  

E-print Network

Generalization of ACID Properties Brahim Medjahed Department of Computer & Information Science; Extended Transaction Models DEFINITION ACID (Atomicity, Consistency, Isolation, and Durability) is a set of properties that guarantee the reliability of database transactions [2]. ACID properties were initially

Medjahed, Brahim

37

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

NASA Astrophysics Data System (ADS)

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

Manna, Joydev; Roy, Binayak; Sharma, Pratibha

2015-02-01

38

n-hydrocarbons conversions over metal-modified solid acid catalysts  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

39

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

Microsoft Academic Search

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

H Sato; K Nagai; H Yoshioka; Y Nagaoka

1999-01-01

40

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

41

Fe-pillared clay as a Fenton-type heterogeneous catalyst for cinnamic acid degradation.  

PubMed

Fe-pillared montmorillonite has been used as a Fenton-type heterogeneous catalyst for the removal of cinnamic acid in water. The influences of the cinnamic acid, catalyst and H2O2 concentrations and pH on the removal rate of cinnamic acid have been studied. The results show that the efficiency of Fe-pillared montmorillonite is higher than that of the Fe ions in the homogeneous phase, and less sensitive to pH. PMID:16546315

Tabet, Djamel; Saidi, Mohamed; Houari, Mohamed; Pichat, Pierre; Khalaf, Hussein

2006-09-01

42

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

PubMed

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

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

2014-08-01

43

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

PubMed

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

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

2014-07-30

44

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.

2012-07-19

45

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

PubMed

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

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

2012-04-17

46

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

NASA Astrophysics Data System (ADS)

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

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

2011-10-01

47

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

PubMed

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

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

2014-10-27

48

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

PubMed

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

Kibsgaard, Jakob; Jaramillo, Thomas F

2014-12-22

49

Effects of Phosphoric Acid Concentration on Platinum Catalyst and Phosphoric Acid Hydrogen Pump Performance  

NASA Astrophysics Data System (ADS)

This work involves the study of the operational performance of phosphoric acid based electrochemical hydrogen pumps with a polybenzimidazole (PBI) electrolytic membrane. During characterization of these devices, the power consumption was found to be highly sensitive to the water vapor pressure in the supply gas stream which in turn affects the phosphoric acid concentration. The power requirement was 30 times higher when the supply gas stream was not humidified than when the supply gas stream was humidified. Upon testing of electrochemical hydrogen pumps over a range of supply gas water vapor pressures from 150 to 0.8 mmHg, it was found that the effective platinum catalyst area decreases as phosphoric acid concentration increases in response to declining supply gas vapor pressure. It was hypothesized that the decline in the effective platinum catalyst area was caused by the adsorption of a species from the electrolyte that increases in concentration with phosphoric acid concentration. Polyphosphoric acid species were such a species which increased in concentration as phosphoric acid concentration increased and as a result were hypothesized to be the species adsorbing on the platinum catalyst. Additional testing was conducted in an electrochemical half cell in which the effect of phosphoric acid concentration on the platinum surface area at a single electrode interface could be studied. Impedance spectroscopy and cyclic voltammetry (CV) testing was used to measure changes in exchange current and platinum surface area following the exposure of the electrode to electrolyte. Platinum surface coverage estimates from CV measurements were 60-87% at a phosphoric acid concentration of 76 wt% P2O5 (105 wt% H3PO 4) and near 100% coverage at 83.3 wt% P2O5 (115 wt% H3PO4). The exchange current for hydrogen oxidation and reduction on platinum decreased by a factor of 25 for 76 wt% P2O 5 and a factor of 1000 for 83.3 wt% P2O5 phosphoric acid concentration within 36 hours. A similar dependence of platinum surface coverage and exchange current on phosphoric acid concentration was observed during hydrogen pump testing over a range of supply gas vapor pressures. This work indicates that platinum catalyst activity declines sharply above a phosphoric acid concentration of 72.4 wt% P2O5 (100 wt% H3PO4) which causes a significant increase in hydrogen pump power consumption. To reduce power consumption, the hydrogen gas supplied to the hydrogen pump requires humidification to a vapor pressure of at least 55 mmHg. The addition of humidification to the supply gas stream adds complexity to a system incorporating a phosphoric acid hydrogen pump. The need to add humidification equipment to reduce phosphoric acid hydrogen pump power consumption may have a significant impact when such devices are applied to hydrogen separation applications including hydrogen recovery from industrial exhaust streams and for emerging alternative energy applications.

Buelte, Steve

50

Surface acidity and basicity: General concepts  

Microsoft Academic Search

A very general definition of acids and basis, following both Brønsted and Lewis theories, is the starting point to introduce the concept of the acid and basic strength of surface sites. The surface of an oxide is described as a bidimensional organization of acid–base pair (AB), whose strength can be measured by probe molecules. It is shown that in order

Adriano Zecchina; Carlo Lamberti; Silvia Bordiga

1998-01-01

51

Bifunctional organic polymeric catalysts with a tunable acid-base distance and framework flexibility.  

PubMed

Acid-base bifunctional organic polymeric catalysts were synthesized with tunable structures. we demonstrated two synthesis approaches for structural fine-tune. In the first case, the framework flexibility was tuned by changing the ratio of rigid blocks to flexible blocks within the polymer framework. In the second case, we precisely adjusted the acid-base distance by distributing basic monomers to be adjacent to acidic monomers, and by changing the chain length of acidic monomers. In a standard test reaction for the aldol condensation of 4-nitrobenzaldehyde with acetone, the catalysts showed good reusability upon recycling and maintained relatively high conversion percentage. PMID:25267260

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

2014-01-01

52

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

53

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

54

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

PubMed

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

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

2012-08-01

55

Chance and necessity in the selection of nucleic acid catalysts  

NASA Technical Reports Server (NTRS)

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

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

1996-01-01

56

Cyclobutane amino acids and peptidomimetics, parallel catalyst screening for aziridination  

E-print Network

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

Li, Shih-ming

2012-06-07

57

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

NASA Astrophysics Data System (ADS)

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

Kackley, Nancy; Kosek, John A.

1989-09-01

58

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

59

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

60

Amino acid derived Cu(II) compounds as catalysts for asymmetric oxidative coupling of 2-naphthol.  

PubMed

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

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

2014-12-23

61

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

E-print Network

Acid Catalyst Functionalization for the Production of Biodiesel Elliot James Nash University of British was functionalized by contacting the biochar with fuming sulfuric acid, either by direct contact (BC-A-LS), vapour Ecological Economic Development Studies (SEEDS) Student Report Investigation of Solid Acid Catalyst

62

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

PubMed

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

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

2014-12-28

63

Highly efficient tetradentate ruthenium catalyst for ester reduction: especially for hydrogenation of Fatty Acid esters.  

PubMed

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

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

2015-02-01

64

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

65

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

DOEpatents

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

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

1999-01-01

66

Continuous chemoselective methylation of functionalized amines and diols with supercritical methanol over solid acid and acid-base bifunctional catalysts.  

PubMed

The selective N-methylation of bifunctionalized amines with supercritical methanol (scCH(3)OH) promoted by the conventional solid acids (H-mordenite, beta-zeolite, amorphous silica-alumina) and acid-base bifunctional catalysts (Cs-P-Si mixed oxide and gamma-alumina) was investigated in a continuous-flow, fixed-bed reactor. The use of scCH(3)OH in the reaction of 2-aminoethanol with methanol (amine/CH(3)OH = 1/10.8) over the solid catalysts led to a significant improvement in the chemoselectivity of the N-methylation. Among the catalysts examined, the Cs-P-Si mixed oxide provided the most efficient catalyst performance in terms of selectivity and reactivity at 300 degrees C and 8.2 MPa; the N-methylation selectivity in the products reaching up to 94% at 86% conversion. The present selective methylation was successfully applied to the synthesis of N-methylated amino alcohols and diamines as well as O-methylated ethylene glycol. Noticeably, ethoxyethylamine was less reactive, suggesting that the hydroxy group of the amino alcohols is a crucial structural factor in determining high reactivity and selectivity, possibly because of the tethering effect of another terminus, a hydroxo group, to the catalyst surface. The magic-angle-spinning NMR spectroscopy and X-ray diffraction analysis of the Cs-P-Si mixed oxide catalyst revealed that the acidic and basic sites originate from P(2)O(5)/SiO(2) and Cs/SiO(2), respectively, and the weak acid-base paired sites are attributed to three kinds of cesium phosphates on SiO(2). The weak acid-base sites on the catalyst surface might be responsible for the selective dehydrative methylation. PMID:15186176

Oku, Tomoharu; Arita, Yoshitaka; Tsuneki, Hideaki; Ikariya, Takao

2004-06-16

67

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

SciTech Connect

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

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

2012-11-15

68

Oxidation catalyst  

DOEpatents

The present invention generally relates to catalyst systems and methods for oxidation of carbon monoxide. The invention involves catalyst compositions which may be advantageously altered by, for example, modification of the catalyst surface to enhance catalyst performance. Catalyst systems of the present invention may be capable of performing the oxidation of carbon monoxide at relatively lower temperatures (e.g., 200 K and below) and at relatively higher reaction rates than known catalysts. Additionally, catalyst systems disclosed herein may be substantially lower in cost than current commercial catalysts. Such catalyst systems may be useful in, for example, catalytic converters, fuel cells, sensors, and the like.

Ceyer, Sylvia T. (Cambridge, MA); Lahr, David L. (Cambridge, MA)

2010-11-09

69

Acid properties of solid acid catalysts characterized by solid-state 31P NMR of adsorbed phosphorous probe molecules.  

PubMed

A brief review is presented on acidity characterization of solid acid catalysts by means of solid-state phosphor-31 magic-angle-spinning nuclear magnetic resonance ((31)P MAS NMR) spectroscopy using phosphor-containing molecules as probes. It is emphasized that such a simple approach using (31)P MAS NMR of adsorbed phosphorous probe molecules, namely trimethylphosphine (TMP) and trialkylphosphine oxides (R(3)PO), represents a unique technique in providing detailed qualitative and quantitative features, viz. type, strength, distribution, and concentration of acid sites in solid acid catalysts. In particular, it will be shown that when applied with a proper choice of probe molecules with varied sizes and results obtained from elemental analysis, the amounts and locations (intracrystalline vs. extracrystalline) of different types (Brønsted vs. Lewis) of acid sites may be determined. In addition, by incorporating the NMR results with that obtained from theoretical density functional theory (DFT) calculations, correlations between the (31)P chemical shifts (?(31)P) and acidic strengths of Brønsted and Lewis acid sites may also be derived, facilitating a suitable acidity scale for solid acid catalysts. PMID:21785784

Zheng, Anmin; Huang, Shing-Jong; Liu, Shang-Bin; Deng, Feng

2011-09-01

70

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

71

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

PubMed Central

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

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

2007-01-01

72

Effect of nickel on the acidity and hydrodesulfurization (HDS) activity of supported molybdate catalysts  

SciTech Connect

The effect of nickel on the acidity and hydrodesulfurization (HDS) activity of supported molybdate catalysts, i.e., 12% MoO/sub 3//Al/sub 2/O/sub 3/ and 3% NiO/13% MoO/sub 3//Al/sub 2/O/sub 3/ prepared by impregnating ..gamma..-Al/sub 2/O/sub 3/ with aqueous ammonium molybdate and nickel nitrate and calcining the samples at 500/sup 0/C, was studied by comparing total and irreversible ammonia adsorption on pure support and nickel-promoted and unpromoted MoO/sub 3/ catalysts at 50/sup 0/-300/sup 0/C and 50-630 mm Hg NH/sub 3/, determining strength distribution of acid sites on the catalyst surface by titration of color indicators with n-butylamine and measuring the catalyst activity in thiophene HDS in a continuous flow reactor at 400/sup 0/C, 1 atm, and 45:1 hydrogen/thiophene molar ratio. Incorporation of MoO/sub 3/ increased both the over-all and the strong acidity of alumina. Promotion of MoO/sub 3//Al/sub 2/O/sub 3/ with NiO further increased the over-all acidity but reduced the concentration of strong acidic sites (pKa less than or equal to -2.4) in favor of intermediate-strength (pKa +2 to +5) sites. The Ni-promoted catalyst had a lower initial HDS activity but a considerably higher steady-state activity than MoO/sub 3//Al/sub 2/O/sub 3/. Apparently thiophene HDS occurs both on strong Broensted (MoO/sub 3/) and Lewis (MoS/sub 2/) acid sites typical of fresh, unpromoted and aged, promoted catalysts, respectively.

Laine, J.; Brito, J.; Yunes, S.

1980-01-01

73

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

PubMed

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

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

2010-06-15

74

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

75

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

76

Homogeneous and Supported Niobium Catalysts as Lewis Acid and Radical Catalysts  

SciTech Connect

The synthesis of tetrachlorotetraphenylcyclopentadienyl group 5 metal complexes has been accomplished through two routes, one a salt metathesis with lithiumtetraphenylcyclopentadiende and the other, reaction with trimethyltintetraphenylcyclopentadiene. The reactants and products have been characterized by {sup 1}H and {sup 13}C({sup 1}H) NMR spectroscopy. The niobium complex promotes the silylcyanation of butyraldehyde. The grafting of metal complexes to silica gel surfaces has been accomplished using tetrakisdimethylamidozirconium as the metal precursor. The most homogeneous binding as determined by CP-MAS {sup 13}C NMR and infrared spectroscopy was obtained with drying at 500 C at 3 mtorr vacuum. The remaining amido groups can be replaced by reaction with alcohols to generate surface bound metal alkoxides. These bound catalysts promote silylcyanation of aryl aldehydes and can be reused three times with no loss of activity.

Wayne Tikkanen

2006-12-31

77

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

PubMed

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

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

2014-12-14

78

The behavior of palladium catalysts in direct formic acid fuel cells  

NASA Astrophysics Data System (ADS)

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

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

79

Hydrothermal conversion of cellulose into lactic acid with nickel catalyst  

Microsoft Academic Search

Utilization of biomass has become a major topic of research around the world. One promising aspect of utilization is production\\u000a of lactic acid from carbohydrate biomass. Our previous study showed that lactic acid can be formed from glucose and cellulose\\u000a by alkaline hydrothermal reactions, but the yield of lactic acid was low, particular for cellulose. In this study, an efficient

Feng-Wen Wang; Zhi-Bao Huo; Yuan-Qing Wang; Fang-Ming Jin

2011-01-01

80

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

81

40 CFR 76.3 - General Acid Rain Program provisions.  

Code of Federal Regulations, 2011 CFR

... 2011-07-01 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...

2011-07-01

82

40 CFR 76.3 - General Acid Rain Program provisions.  

Code of Federal Regulations, 2012 CFR

... 2012-07-01 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...

2012-07-01

83

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

84

40 CFR 76.3 - General Acid Rain Program provisions.  

... 2014-07-01 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...

2014-07-01

85

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

PubMed

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

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

2014-06-01

86

Characterization of the Acid Properties of Tungsten\\/Zirconia Catalysts Using Adsorption Microcalorimetry and n-Pentane Isomerization Activity  

Microsoft Academic Search

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

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

1999-01-01

87

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

PubMed

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

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

2014-05-01

88

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

PubMed

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

Nedumaran, D; Pandurangan, A

2014-04-01

89

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

90

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

91

Effect of deactivation and reactivation of palladium anode catalyst on performance of direct formic acid fuel cell (DFAFC)  

Microsoft Academic Search

In the present study, degradation and recovery in cell performance of direct formic acid fuel cells (DFAFCs) are investigated. For DFAFC tests, palladium (Pd) and platinum (Pt) are used as anode and cathode catalysts, respectively, and are applied to a Nafion membrane by catalyst-coated membrane (CCM) spraying. As multiple repeated DFAFC operations are performed, the cell performance of DFAFC is

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

2011-01-01

92

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

PubMed

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

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

2012-09-01

93

Characterization of acidic properties of microporous and mesoporous zeolite catalysts using TGA and DSC  

SciTech Connect

Thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) were applied for characterizing the acidic properties of microporous and mesoporous zeolite catalysts through temperature-programmed desorption (TPD) of n-butylamine (n-BA) as a base probe molecule. A flow system was designed with heating and evacuation capability for preparing the n-BA adsorbed sample. In the TGA, n-BA desorption at different temperatures represents the interaction with surface acidic sites of different strength. The acid sites corresponding to base desorption at 100-240{degrees}C, 240-340{degrees}C, and 340-500{degrees}C, were classified as weak, intermediate, and strong acid sites, respectively. DSC indicates the endothermic nature of the differential thermogravimetric peaks (observed from TGA) in the above temperature regimes, consuming the TPD data. The microporous zeolites examined include three proton-form mordenites, three proton-form and metal-ion exchanged Y-zeolites, and four noble metal catalysts supported on mordenite and Y-zeolite. Four mesoporous zeolites were synthesized and examined by the same TPD method. Both the total acidity (mmol/g) and acid strength distribution depend on the zeolite VAX, Si/Al ratio, and metal loading. Ni and La ion-exchange decreased the strong acid sites. Pt and Pd loading on an HY decreased the strong acid sites but their loading on an H-mordenite had little effect on its strong acid sites. Mesoporous zeolites showed lower acidity and lower fraction of strong acid sites compared to HY and H-mordenites. However, the acidity of mesoporous zeolites strongly depends on the aluminum source compounds used in the hydrothermal synthesis of the zeolites.

Song, Chunshan; Lai, Wei-Chuan; Schmitz, A.D. [Pennsylvania State Univ., University Park, PA (United States)] [and others

1996-12-31

94

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

PubMed

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

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

2007-07-15

95

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

PubMed Central

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

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

2012-01-01

96

Geminal Brønsted Acid Ionic Liquids as Catalysts for the Mannich Reaction in Water  

PubMed Central

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

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

2014-01-01

97

Efficient disproportionation of formic acid to methanol using molecular ruthenium catalysts.  

PubMed

The disproportionation of formic acid to methanol was unveiled in 2013 using iridium catalysts. Although attractive, this transformation suffers from very low yields; methanol was produced in less than 2% yield, because the competitive dehydrogenation of formic acid (to CO2 and H2) is favored. We report herein the efficient and selective conversion of HCOOH to methanol in 50% yield, utilizing ruthenium(II) phosphine complexes under mild conditions. Experimental and theoretical (DFT) results show that different convergent pathways are involved in the production of methanol, depending on the nature of the catalyst. Reaction intermediates have been isolated and fully characterized and the reaction chemistry of the resulting ruthenium complexes has been studied. PMID:25088282

Savourey, Solène; Lefèvre, Guillaume; Berthet, Jean-Claude; Thuéry, Pierre; Genre, Caroline; Cantat, Thibault

2014-09-22

98

Characterization of acidic properties of microporous and mesoporous zeolite catalysts using TGA and DSC  

SciTech Connect

Thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) were applied for characterizing the acidic properties of microporous and mesoporous zeolite catalysts through temperature-programmed desorption (TPD) of n-butylamine (n-BA). A flow system was designed with heating and evacuation capability for preparing the n-BA adsorbed sample. The sample was then transferred to TGA (or DSC) apparatus. n-BA desorption conducted on TGA at different temperatures represents the interaction with surface acidic sites of different strength. BAse desorption at 100-240{degrees}C, 240-340{degrees}C, and 340-500{degrees}C, was classified as weak, intramediate, and strong acid sites, respectively. DSC indicates the endothermic nature of the differential thermogravimetric peaks (observed from TGA) in the above temperature regimes, confirming the TPD data. The microporous zeolites examined include three proton-form mordenites, three proton-form and metal-ion exchanged Y-zeolites, and four noble metal catalysts supported on mordenite and Y-zeolite. Four mesoporous zeolites were synthesized and examined by the same TPD method. Both the total acidity (mmol/g) and acid strength distribution depend on the zeolite type. Si/Al ratio, and metal loading. Ni and La ion-exchange decreased the strong acid sites. Pt and Pd loading on an HY decreased the strong acid sites but their loading on an H-mordenite had little effect on its strong acid sites. Mesoporous zeolites showed lower acidity and lower fraction of strong acid sites compared to HY and H-mordenites. However, the acidity of mesoporous zeolites strongly depends on the aluminum source compounds used in the hydrothermal synthesis of the zeolites.

Song, Chunshan; Lai, Wei-Chuan; Schmitz, A.D.; Reddy, K.M. [Pennsylvania State Univ., University Park, PA (United States)] [and others

1996-10-01

99

Conversion of biomass into 5-hydroxymethylfurfural using solid acid catalyst.  

PubMed

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 (Nb(2)O(5)·nH(2)O(2)) after pretreatment showed high catalytic activities for dehydration of mono- and polysaccharide to HMF at 433 K in water-2-butanol (2:3 v/v) biphasic system, giving high HMF yield of 89% and 54% from fructose and inulin, respectively. The HMF yield was up to 74% and 65% when inulin and Jerusalem artichoke juice were hydrolyzed by exoinulinase. The solid acid made the process environment-friendly and energy-efficient to convert carbohydrates into bio-fuels and platform chemicals. PMID:21036606

Yang, Fengli; Liu, Qishun; Bai, Xuefang; Du, Yuguang

2011-02-01

100

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

Microsoft Academic Search

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

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

101

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

Microsoft Academic Search

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

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

2011-01-01

102

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

Microsoft Academic Search

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

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

2006-01-01

103

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

104

Polymerization of Lactic Acid by MAGHNITE-H+ a Non-Toxic Montmorillonite Clay Catalyst  

NASA Astrophysics Data System (ADS)

The development of synthetic biodegradable polymers, such as poly(lactic acid), is particularly important for constructing medical devices, controlled drug release matrix, including scaffolds and sutures, and has attracted growing interest in the biomedical field. Here, we report a novel approach to preparing poly (D, L-lactic acid) (PDLA) as a biodegradable polymer. We investigated in detail the reaction conditions for the simple direct polycondensation of D, L-lactic acid, including the reaction times, temperatures, and catalyst. The molecular weight of synthesized PDLA is dependent on both the reaction temperature, amount of catalyst and time. The optimum reaction condition to obtain PDLA by direct polycondensation using Maghnite-H+[1,2], a proton exchanged Montmorillonite clay, as catalyst was thus determined to be 120 °C, 5% amount of Maghnite-H+ for 28 h with a molecular weight of 7970. The method for PDLA synthesis established here will facilitate production of PDLA of various molecular weights, which may have a potential utility as biomaterials.

Harrane, A.; Belaouedj, M. A.; Meghabar, R.; Belbachir, M.

2008-08-01

105

Ursodeoxycholic acid induced generalized fixed drug eruption.  

PubMed

Fixed drug eruption (FDE) is a rare form of drug allergies that recur at the same cutaneous or mucosal site in every usage of drug. Single or multiple round, sharply demarcated and dusky red plaques appear soon after drug exposure. Ursodeoxycholic acid (UDCA: 3?,7?-dihydroxy-5?-cholanic acid) is used for the treatment of cholestatic liver diseases. Some side effects may be observed, such as diarrhea, dyspepsia, pruritus and headaches. We encountered only three cases of lichenoid reaction regarding the use of UDCA among previous studies. In this article, we reported a generalized FDE case related to UDCA intake in a 59-year-old male patient with cholestasis for the first time in the literature. PMID:24147950

Ozkol, Hatice Uce; Calka, Omer; Dulger, Ahmet Cumhur; Bulut, Gulay

2014-09-01

106

Catalysis Letters 51 (1998) 1522 15 The role of acid sites in cobalt zeolite catalysts for selective  

E-print Network

Catalysis Letters 51 (1998) 15­22 15 The role of acid sites in cobalt zeolite catalysts Received 13 August 1997; accepted 9 January 1998 The role of the acidic support in ion-exchanged cobalt-zeolite acidic zeolites [4,10,15­17], such as ZSM-5 and morden- ite, the role of zeolite remains unclear [3

Regalbuto, John R.

107

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

PubMed

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

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

2014-09-01

108

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

PubMed

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

Rafiee, Ezzat; Rahpeima, Nasibeh; Eavani, Sara

2014-01-01

109

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

110

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

PubMed

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

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

2010-01-01

111

Nickel recovery from spent Raneynickel catalyst through dilute sulfuric acid leaching and soda ash precipitation.  

PubMed

Pharmaceutical industry makes extensive use of Raneynickel catalyst for various organic drug intermediates/end products. Spent catalysts contain environmentally critical and economically valuable metals. In the present study, a simple hydrometallurgical process using dilute sulfuric acid leaching was described for the recovery of nickel from spent Raneynickel catalyst. Recovery of nickel varied with acid concentration and time, whereas temperature had negligible effect. Increase of S/L ratio to 30% (w/v) showed marginal effect on nickel (90%) recovery, whereas Al recovery decreased drastically to approximately 20%. Under the optimum conditions of leaching viz: 12 vol.% H(2)SO(4), 30 degrees C, 20% solid to liquid (S/L) ratio and 120 min reaction time, it was possible to recover 98.6% Ni along with 39.2% Al. Leach liquor [pH 0.7] containing 85.0 g/L Ni and 3.25 g/L Al was adjusted to pH 5.4 with 30 wt.% alkali for quantitative aluminum removal. Nickel loss was about 2% during this Al removal step. Nickel from the purified leach liquor was recovered as nickel carbonate by adding required amount of Na(2)CO(3). The purity of NiCO(3) product was found to be 100% with a Ni content of 48.6%. Na(2)SO(4) was recovered as a by-product with a purity of 99%. Complete process is presented. PMID:20018448

Lee, Jin Young; Rao, S Venkateswara; Kumar, B Nagaphani; Kang, Dong Jun; Reddy, B Ramachandra

2010-04-15

112

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

PubMed

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

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

2014-09-01

113

Degradation of Fe/N/C catalysts upon high polarization in acid medium.  

PubMed

A comprehensive study of the degradation of a highly active Fe/N/C catalyst in acid medium is reported. An accelerated aging protocol was applied in the temperature range of 20 to 80 °C. From fundamental rotating-disc electrode studies and polymer electrolyte membrane fuel cell investigations combined with identical-location electron microscopy and Mößbauer spectroscopy at various stages of degradation, important insights into the structural and chemical changes of the catalyst were obtained. Most importantly, the degradation is strongly enhanced at elevated temperature, which is correlated to (i) increased carbon-corrosion rate and (ii) parallel non-preferential dissolution of the FeNx-based active sites. The degradation not only leads to a decreased ORR kinetics over time but also induces significant charge- and mass-transport resistances due to the collapse of the electrode structure. PMID:25070913

Goellner, Vincent; Baldizzone, Claudio; Schuppert, Anna; Sougrati, Moulay Tahar; Mayrhofer, Karl; Jaouen, Frédéric

2014-09-14

114

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

PubMed

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

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

2010-02-22

115

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

PubMed

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

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

2014-04-01

116

Metal amides as the simplest acid/base catalysts for stereoselective carbon-carbon bond-forming reactions.  

PubMed

In this paper, new possibilities for metal amides are described. Although typical metal amides are recognized as strong stoichiometric bases for deprotonation of inert or less acidic hydrogen atoms, transition-metal amides, namely silver and copper amides, show interesting abilities as one of the simplest acid/base catalysts in stereoselective carbon-carbon bond-forming reactions. PMID:23775980

Yamashita, Yasuhiro; Kobayashi, Sh?

2013-07-15

117

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...

118

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

119

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

120

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

PubMed

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

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

2013-05-01

121

Chiral salen–metal complexes as novel catalysts for the asymmetric synthesis of ?-amino acids under phase transfer catalysis conditions  

Microsoft Academic Search

Chiral salen–metal complexes have been tested as catalysts for the C-alkylation of Schiff's bases of alanine and glycine esters with alkyl bromides under phase-transfer conditions (solid sodium hydroxide, toluene, ambient temperature, 1–10mol% of the catalyst). The best catalyst, which was derived from a Cu(II) complex of (1R, 2R or 1S,2S)-[N,N?-bis(2?-hydroxybenzylidene)]-1,2-diaminocyclohexane, gave ?-amino and ?-methyl-?-amino acids with enantiomeric excesses of 70–96%.

Yuri N Belokon; Michael North; Tatiana D Churkina; Nikolai S Ikonnikov; Victor I Maleev

2001-01-01

122

Rhodium Containing Magnetic Nanoparticles: Effective Catalysts for Hydrogenation and the 1,4Addition of Boronic Acids  

Microsoft Academic Search

New efficient rhodium catalysts supported on superparamagnetic iron oxide nanoparticles (NPs) have been prepared using a novel\\u000a method involving sulfonated triphenylphosphine ligands. They successfully promote the hydrogenation of olefins as well as\\u000a the addition of arylboronic acids to dimethyl itaconate (ItMe2) in water for up to 10 recycles. The catalysts were stable towards leaching of the metal complexes and were

Urszula Laska; Christopher G. Frost; Pawel K. Plucinski; Gareth J. Price

2008-01-01

123

Increase of reformate yield by using polyacrylic acid as template in preparation of Pt\\/Re naphtha reforming catalysts  

Microsoft Academic Search

The need for naphtha reforming to produce high quality reformate for gasoline blend stocks with increased yield has become more urgent due to dwindling crude oil reserves and stringent air pollution regulations. Reforming catalysts prepared using polyacrylic acid (PAA) as a metal ion template exhibited 1.4–2.4% improvement in reformate yield and 1.0–2.0wt% lower aromatic production compared to commercially available catalysts

Changkun Liu; Qing Zhu; Zhihua Wu; Zhenhua Zhou; Gaurang Bhargava; Sukesh Parasher; Michael Rueter; Bing Zhou; Jingguang G. Chen

2010-01-01

124

Ring-opening polymerization of lactides catalyzed by natural amino-acid based zinc catalysts.  

PubMed

A series of chiral NNO-tridentate Schiff base ligands derived from natural amino acids were reacted with zinc(bis-trimethylsilylamide)(2) to provide metal complexes which have been fully characterized. One of these derivatives was further reacted with p-fluorophenol to yield a phenoxide complex. X-ray crystallographic studies reveal the zinc Schiff base amide complexes to be monomeric, whereas, the p-fluorophenolate complex was shown to be dimeric with bridging phenoxide ligands. All zinc complexes were shown to be very effective catalysts for the ring-opening polymerization (ROP) of lactides at ambient temperature, producing polymers with controlled and narrow molecular weight distributions. These enantiomerically pure zinc complexes did not show selectivity toward either L- or D-lactide, that is, k(D(obsd))/k(L(obsd)) approximately = 1. However, steric substituents on the Schiff base ligands exhibited moderate to excellent stereocontrol for the ROP of rac-lactide. Heterotactic polylactides were produced from rac-lactide with P(r) values ranging from 0.68 to 0.89, depending on the catalyst employed and the reaction temperature. The reactivities of the various catalysts were greatly affected by substituents on the Schiff base ligands, with sterically bulky substituents being rate enhancing. PMID:20121063

Darensbourg, Donald J; Karroonnirun, Osit

2010-03-01

125

Efficient cluster-based catalysts for asymmetric hydrogenation of ?-unsaturated carboxylic acids.  

PubMed

The new clusters [H(4)Ru(4)(CO)(10)(?-1,2-P-P)], [H(4)Ru(4)(CO)(10) (1,1-P-P)] and [H(4)Ru(4)(CO)(11)(P-P)] (P-P=chiral diphosphine of the ferrocene-based Josiphos or Walphos ligand families) have been synthesised and characterised. The crystal and molecular structures of eleven clusters reveal that the coordination modes of the diphosphine in the [H(4)Ru(4)(CO)(10)(?-1,2-P-P)] clusters are different for the Josiphos and the Walphos ligands. The Josiphos ligands bridge a metal-metal bond of the ruthenium tetrahedron in the "conventional" manner, that is, with both phosphine moieties coordinated in equatorial positions relative to a triangular face of the tetrahedron, whereas the phosphine moieties of the Walphos ligands coordinate in one axial and one equatorial position. The differences in the ligand size and the coordination mode between the two types of ligands appear to be reflected in a relative propensity for isomerisation; in solution, the [H(4)Ru(4)(CO)(10)(1,1-Walphos)] clusters isomerise to the corresponding [H(4)Ru(4)(CO)(10)(?-1,2-Walphos)] clusters, whereas the Josiphos-containing clusters show no tendency to isomerisation in solution. The clusters have been tested as catalysts for asymmetric hydrogenation of four prochiral ?-unsaturated carboxylic acids and the prochiral methyl ester (E)-methyl 2-methylbut-2-enoate. High conversion rates (>94%) and selectivities of product formation were observed for almost all catalysts/catalyst precursors. The observed enantioselectivities were low or nonexistent for the Josiphos-containing clusters and catalyst (cluster) recovery was low, suggesting that cluster fragmentation takes place. On the other hand, excellent conversion rates (99-100%), product selectivities (99-100% in most cases) and good enantioselectivities, reaching 90% enantiomeric excess (ee) in certain cases, were observed for the Walphos-containing clusters, and the clusters could be recovered in good yield after completed catalysis. Results from high-pressure NMR and IR studies, catalyst poisoning tests and comparison of catalytic properties of two [H(4)Ru(4)(CO)(10)(?-1,2-P-P)] clusters (P-P=Walphos ligands) with the analogous mononuclear catalysts [Ru(P-P)(carboxylato)(2)] suggest that these clusters may be the active catalytic species, or direct precursors of an active catalytic cluster species. PMID:22890820

Moberg, Viktor; Duquesne, Robin; Contaldi, Simone; Röhrs, Oliver; Nachtigall, Jonny; Damoense, Llewellyn; Hutton, Alan T; Green, Michael; Monari, Magda; Santelia, Daniela; Haukka, Matti; Nordlander, Ebbe

2012-09-24

126

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

127

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

128

Methanetrisulfonic Acid: A Highly Efficient Strongly Acidic Catalyst for Wagner-Meerwein Rearrangement, Friedel-Crafts Alkylation and Acylation Reactions. Examples from Vitamin E Synthesis  

Microsoft Academic Search

Methanetrisulfonic acid had been prepared for the first time over 140 years ago, but it was used only scarcely in chemical transformations. In the course of our activities dealing with key-steps of industrial syntheses of vitamins, e.g. economically important vitamin E (acetate), we found that methanetrisulfonic acid is an extremely effective catalyst in a variety of reactions. Examples of its

Werner Bonrath; Fabrice Aquino; Alois Haas; Simone Hoppmann; Thomas Netscher; Francesco Pace; Horst Pauling

2009-01-01

129

40 CFR 75.3 - General Acid Rain Program provisions.  

Code of Federal Regulations, 2012 CFR

...17 2012-07-01 2012-07-01 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,...

2012-07-01

130

40 CFR 75.3 - General Acid Rain Program provisions.  

Code of Federal Regulations, 2010 CFR

...16 2010-07-01 2010-07-01 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,...

2010-07-01

131

40 CFR 75.3 - General Acid Rain Program provisions.  

...17 2014-07-01 2014-07-01 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,...

2014-07-01

132

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

133

40 CFR 75.3 - General Acid Rain Program provisions.  

Code of Federal Regulations, 2011 CFR

...16 2011-07-01 2011-07-01 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,...

2011-07-01

134

Cellulose sulfuric acid as a bio-supported and recyclable solid acid catalyst for the one-pot three-component synthesis of ?-amino nitriles  

Microsoft Academic Search

?-Amino nitriles are synthesized by a one-pot three-component condensation reaction of amines, aldehydes and trimethylsilylcyanide in the presence of a catalytic amount of cellulose sulfuric acid as a bio-supported catalyst, in excellent yields with short reaction times at ambient temperature. The reaction work-up is simple and the catalyst can be easily separated from the product and reused in subsequent reactions.

Ahmad Shaabani; Ali Maleki

2007-01-01

135

Xanthan sulfuric acid: A new and efficient bio-supported solid acid catalyst for the synthesis of ?-amino nitriles by condensation of carbonyl compounds, amines, and trimethylsilylcyanide  

Microsoft Academic Search

In this work, ?-amino nitriles are synthesized by a three-component one-pot condensation reaction of aldehydes or ketones, amines and trimethylsilylcyanide in the presence of a catalytic amount of xanthan sulfuric acid as a new bio-supported catalyst, in excellent yields with short reaction times at ambient temperature. The xanthan as the base of the catalyst was produced biologically from a native

Ahmad Shaabani; Ali Maleki; Mohammad Reza Soudi; Hamid Mofakham

2009-01-01

136

Cellulose sulfuric acid as a biodegradable and recoverable solid acid catalyst for one pot synthesis of substituted pyrroles under solvent-free conditions at room temperature  

Microsoft Academic Search

A new and efficient method for the preparation of N-substituted pyrroles from one-pot condensation reaction of 2,5-hexandione with amines and diamines in the presence of cellulose sulfuric acid (CSA) as a bio-supported catalyst at room temperature under solvent-free conditions is presented. This new protocol has the advantages of easy availability, stability, reusability and eco-friendly of the catalyst, high to excellent

Ali Rahmatpour

2011-01-01

137

Enhanced performance of the catalytic conversion of allyl alcohol to 3-hydroxypropionic acid using bimetallic gold catalysts.  

PubMed

One of the strategic building blocks in organic synthesis is 3-hydroxypropionic acid, which is particularly important for the manufacture of high performance polymers. However, to date, despite many attempts using both biological and chemical routes, no large scale effective process for manufacturing 3-hydroxypropionic acid has been developed. One potentially useful starting point is from allyl alcohol, as this can be obtained in principle from the dehydration of glycerol, thereby presenting a bio-renewable green pathway to this important building block. The catalytic transformation of allyl alcohol to 3-hydroxypropionic acid presents interesting challenges in catalyst design, particularly with respect to the control of selectivity among the products that can be expected, as acrylic acid, acrolein and glyceric acid can also be formed. In this paper, we present a novel eco-sustainable catalytic pathway leading to 3-hydroxypropionic acid, which highlights the outstanding potential of gold-based and bimetallic catalysts in the aerobic oxidation of allyl alcohol. PMID:22455056

Falletta, Ermelinda; Della Pina, Cristina; Rossi, Michele; He, Qian; Kiely, Christopher J; Hutchings, Graham J

2011-01-01

138

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

139

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

140

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

141

Metal recovery from spent hydrodesulfurization catalysts using a combined acid-leaching and electrolysis process.  

PubMed

This study focuses on recovering valuable metals from spent hydrodesulfurization (HDS) catalysts using a combined acid-leaching and fluidized-bed electrolysis process. The electrolytic cell was equipped with a glass bead medium, an iridium oxide mesh anode, and a stainless steel plate cathode. An acid solution consisting of concentrated HNO3/H2SO4/HCl with a volume ratio of 2:1:1 was found to be better than the other tested solution (HNO3/H2SO4=1:1) to leach the metals. For the three-acid mixture, the best solid/liquid ratio and leaching time were 40 g/L and 1 h, respectively, at 70 degrees C; under this condition, the leaching yields of target metals (Mo, Ni, and V) in the 1st stage of leaching reached 90, 99, and 99%, respectively, much higher than those in the 2nd/3rd/4th stages. When this acid leachate was electrolyzed for 2 h at 2 A constant current (current density=approximately 35.7 mA/cm2), a stable cell voltage of 5 V was observed. The electrolytic recoveries of Mo, Ni, and V were approximately 15, 61, and 66%, respectively, but extending the electrolysis time from 2 to 4 h did not increase the recoveries. For this operation, the total recoveries (leaching yieldxelectrolytic recovery) of Mo, Ni, and V were approximately 14, 60, and 65%, respectively. PMID:18060691

Lai, Yi-Chieh; Lee, Wen-Jhy; Huang, Kuo-Lin; Wu, Chung-Mou

2008-06-15

142

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

PubMed

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

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

2014-12-01

143

Atypical fatty acids appearing during technological treatments. General sur-  

E-print Network

Atypical fatty acids appearing during technological treatments. General sur- vey concerning rue Sully, BV 1540, 21034 Dijon) Fatty acids may be submitted to some changes during technological treatments. A correlation of the fragility of these fatty acids with the number of ethylenic bonds

Paris-Sud XI, Université de

144

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

PubMed

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

Hamasaka, Go; Uozumi, Yasuhiro

2014-12-01

145

Graphene nanosheets-polypyrrole hybrid material as a highly active catalyst support for formic acid electro-oxidation  

E-print Network

Graphene nanosheets-polypyrrole hybrid material as a highly active catalyst support for formic acid. Therefore, the synthesis of hybrid materials consisting of reduced graphene oxide (RGO) with PPy matrix A novel electrode material based on graphene oxide (GO)-polypyrrole (PPy) composites was synthesized

Gao, Hongjun

146

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

PubMed

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

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

2014-12-01

147

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

Microsoft Academic Search

Thermochemical cycles consist of a series of chemical reactions to produce hydrogen from water at lower temperatures than by direct thermal decomposition. All the sulfur-based cycles for water splitting employ the sulfuric acid decomposition reaction. This work reports the studies performed on 1wt% Pt\\/TiO2 (rutile) catalysts submitted to flowing concentrated sulfuric acid at 1123K and atmospheric pressure for different times

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

2008-01-01

148

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

PubMed

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

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

2013-01-30

149

On the Acid-Base Mechanism for Ruthenium Water Oxidation Catalysts  

E-print Network

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

Wang, Lee-Ping

150

Xanthan Sulfuric Acid: A New and Efficient Bio-Supported Solid Acid Catalyst for the Synthesis of 3,4-Dihydropyrimidin-2(1H)-Ones  

Microsoft Academic Search

Xanthan sulfuric acid (XSA) is employed as a recyclable catalyst for the synthesis of 3,4-dihydropyrimidin-2(1H)-ones. These syntheses were performed via a one-pot three-component condensation of aldehydes, amines, and urea\\/thiourea under Solvent-free conditions.

B. Suresh Kuarm; J. Venu Madhav; S. Vijaya Laxmi; B. Rajitha

2011-01-01

151

Characterization of Lewis acidity of cation-exchanged montmorillonite K-10 clay as effective heterogeneous catalyst for acetylation of alcohol  

Microsoft Academic Search

Catalytic activity of 14 types of metal ion-exchanged montmorillonite K-10 clay (Mn+-mont) is tested for the acetylation of cyclohexanol with acetic anhydride at room temperature. The activity increases with an increase in the charge\\/radius ratio of exchanged cation. The activity of Fe3+-mont is the highest and is higher than those of other Fe3+ catalysts, FeCl3·6H2O and FeCl3\\/SiO2, conventional acid catalysts,

Ken-ichi Shimizu; Tomoya Higuchi; Emi Takasugi; Tsuyoshi Hatamachi; Tatsuya Kodama; Atsushi Satsuma

2008-01-01

152

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

PubMed

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

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

2011-10-01

153

Palladium(0) nanoclusters stabilized by poly(4-styrenesulfonic acid-co-maleic acid) as an effective catalyst for Suzuki–Miyaura cross-coupling reactions in water  

Microsoft Academic Search

Palladium(0) nanoclusters stabilized by poly(4-styrenesulfonic acid-co-maleic acid), PSSA-co-MA, were generated in situ during the hydrolysis of ammonia–borane (AB) from the reduction of potassium tetrachloropalladate(II) in aqueous solution at room temperature. They were isolated from the reaction solution and characterized by UV–visible electronic absorption spectroscopy, TEM, SAED and XRD techniques. The PSSA-co-MA stabilized palladium(0) nanoclusters were used as catalyst in Suzuki–Miyaura

Önder Metin; Feyyaz Durap; Murat Aydemir; Saim Özkar

2011-01-01

154

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

PubMed

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

Díaz, L; Borges, M E

2012-08-15

155

Multielement crystalline and pseudocrystalline oxides as efficient catalysts for the direct transformation of glycerol into acrylic Acid.  

PubMed

Glycerol surplus from biodiesel synthesis still represents a major problem in the biofuel production chain. Meanwhile, those in the acrylic acid market are looking for new processes that are able to offer viable alternatives to propylene-based production. Therefore, acrylic acid synthesis from glycerol could be an effective solution to both issues. Among the viable routes, one-pot synthesis theoretically represents the most efficient process, but it is also highly challenging from the catalyst design standpoint. A new class of complex W?Mo?V mixed-oxide catalysts, which are strongly related to the hexagonal tungsten bronze structure, able to directly convert glycerol into acrylic acid with yields of up to 51?% are reported. PMID:25488515

Chieregato, Alessandro; Soriano, M Dolores; García-González, Ester; Puglia, Giuseppe; Basile, Francesco; Concepción, Patricia; Bandinelli, Claudia; López Nieto, José M; Cavani, Fabrizio

2015-01-01

156

Influence of the starting aluminum salt on the surface and acid properties of AlPOâ catalysts precipitated with ammonium hydroxide  

Microsoft Academic Search

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 AlPOâ (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,

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

1988-01-01

157

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

PubMed

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

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

2012-11-01

158

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

2012-08-01

159

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

PubMed

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

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

2015-03-01

160

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

161

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

162

MIL-101-SO3H: a highly efficient Brønsted acid catalyst for heterogeneous alcoholysis of epoxides under ambient conditions.  

PubMed

For the first time, a ?100% sulfonic acid functionalized metal-organic framework (MOF), MIL-101-SO3H, with giant pores has been prepared by a hydrothermal process followed by a facile postsynthetic HCl treatment strategy. The replete readily accessible Lewis acidic and especially Brønsted acidic sites distributed throughout the framework as well as high stability endow the resultant MOF exceptionally high efficiency and recyclability, which surpass all other MOF-based catalysts, for the ring opening of epoxides with alcohols (especially, methanol) as nucleophiles under ambient conditions. PMID:25291973

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

2014-11-10

163

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

164

Oxyhydrochlorination catalyst  

DOEpatents

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

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

1992-01-01

165

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

PubMed Central

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

MURAHASHI, Shun-Ichi

2011-01-01

166

Facile and Promising Method for Michael Addition of Indole and Pyrrole to Electron-Deficient trans-?-Nitroolefins Catalyzed by a Hydrogen Bond Donor Catalyst Feist's Acid and Preliminary Study of Antimicrobial Activity  

PubMed Central

The importance of cooperative hydrogen-bonding effects has been demonstrated using novel 3-methylenecyclopropane-1,2-dicarboxylic acid (Feist's acid (FA)) as hydrogen bond donor catalysts for the addition of indole and pyrrole to trans-?-nitrostyrene derivatives. Because of the hydrogen bond donor (HBD) ability, Feist's acid (FA) has been introduced as a new class of hydrogen bond donor catalysts for the activation of nitroolefin towards nucleophilic substitution reaction. It has effectively catalyzed the Michael addition of indoles and pyrrole to ?-nitroolefins under optimum reaction condition to furnish the corresponding Michael adducts in good to excellent yields (up to 98%). The method is general, atom-economical, convenient, and eco-friendly and could provide excellent yields and regioselectivities. Some newly synthesized compounds were for examined in vitro antimicrobial activity and their preliminary results are reported. PMID:24574906

Al Majid, Abdullah M. A.; Islam, Mohammad Shahidul; Barakat, Assem; Al-Agamy, Mohamed H. M.; Naushad, Mu.

2014-01-01

167

Facile and promising method for michael addition of indole and pyrrole to electron-deficient trans-?-nitroolefins catalyzed by a hydrogen bond donor catalyst Feist's acid and preliminary study of antimicrobial activity.  

PubMed

The importance of cooperative hydrogen-bonding effects has been demonstrated using novel 3-methylenecyclopropane-1,2-dicarboxylic acid (Feist's acid (FA)) as hydrogen bond donor catalysts for the addition of indole and pyrrole to trans-?-nitrostyrene derivatives. Because of the hydrogen bond donor (HBD) ability, Feist's acid (FA) has been introduced as a new class of hydrogen bond donor catalysts for the activation of nitroolefin towards nucleophilic substitution reaction. It has effectively catalyzed the Michael addition of indoles and pyrrole to ?-nitroolefins under optimum reaction condition to furnish the corresponding Michael adducts in good to excellent yields (up to 98%). The method is general, atom-economical, convenient, and eco-friendly and could provide excellent yields and regioselectivities. Some newly synthesized compounds were for examined in vitro antimicrobial activity and their preliminary results are reported. PMID:24574906

Al Majid, Abdullah M A; Islam, Mohammad Shahidul; Barakat, Assem; Al-Agamy, Mohamed H M; Naushad, Mu

2014-01-01

168

Deactivation and acidity deterioration of a SiO[sub 2]/Al[sub 2]O[sub 3] catalyst in the isomerization of cis-butene  

SciTech Connect

The evolution of acidity of a SiO[sub 2]/Al[sub 2]O[sub 3] catalyst in the isomerization of cis-butene has been studied. The catalyst deactivation takes place by blockage of active sites by slightly evolved coke, which is partially soluble in dichloromethane and pyridine and is slightly aromatic. The blockage of active sites has no incidence on the porous structure and on the catalyst surface area. By combining the results for the catalyst in different deactivation states, corresponding to calorimetric and thermogravimetric measurements of tert-butylamine desorption at a programmed temperature, the evolution of the average value of acidity strength has been determined. In addition, from tert-butylamine adsorption measurements at 200C, the evolution of surface acidity strength distribution has been attained. The fast deactivation of very strong acidic sites is concluded.

Gayubo, A.G.; Arandes, J.M.; Aguayo, A.T.; Olazar, M.; Bilbao, J. (Univ. del Pais Vasco, Bilbao (Spain))

1993-04-01

169

Novel catalyst-support interaction for direct formic acid fuel cell anodes: Pd electrodeposition on surface-modified graphite felt  

Microsoft Academic Search

The electrodeposition of Pd on graphite felt (GF, thickness ~3 mm in uncompressed state) was studied and the resulting catalyst\\u000a was compared with Pt-Ru\\/GF for the electro-oxidation of formic acid. A micellar solution composed of the non-ionic surfactant\\u000a Triton X-102 and an aqueous phase containing PdCl2 were utilized for the galvanostatic electrodeposition of Pd nanoparticles. The presence of the surfactant during

Tommy T. Cheng; El?d L. Gyenge

2009-01-01

170

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

PubMed Central

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

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

2013-01-01

171

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

PubMed

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

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

2015-03-01

172

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

PubMed

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

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

2010-01-01

173

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

174

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

PubMed Central

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

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

2013-01-01

175

The p K a of the General Acid\\/Base Carboxyl Group of a Glycosidase Cycles during Catalysis:  A 13 C-NMR Study of Bacillus circulans Xylanase †  

Microsoft Academic Search

The 20 kDa xylanase from Bacillus circulans carries out hydrolysis of xylan via a two-step mechanism involving a covalent glycosyl-enzyme intermediate. In this double-displacement reaction, Glu78 functions as a nucleophile to form the intermediate, while Glu172 acts as a general acid catalyst during glycosylation, protonating the departing aglycone, and then as a general base during deglycosylation, deprotonating the attacking water.

Lawrence P. McIntosh; Greg Hand; Philip E. Johnson; Manish D. Joshi; Michael Körner; Leigh A. Plesniak; Lothar Ziser; Warren W. Wakarchuk; Stephen G. Withers

1996-01-01

176

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

NASA Astrophysics Data System (ADS)

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

Sadanandan, Manoj; Bhaskaran, Beena

2014-08-01

177

Cellulose sulfuric acid as a bio-supported and recyclable solid acid catalyst for the one-pot synthesis of 2,4,5-triarylimidazoles under microwave irradiation  

Microsoft Academic Search

A simple, rapid, and highly efficient method has been attempted for the three-component condensation of benzil\\/benzoin, aldehydes, and ammonium acetate under microwave irradiation in the presence of a catalytic amount of bio-supported cellulose sulfuric acid under solvent-free conditions to afford the 2,4,5-triarylimidazole derivatives. The catalyst is easily prepared, inexpensive, separated simply by filtration, gives excellent yield of products with shorter

Kiran F. Shelke; Suryakant B. Sapkal; Gopal K. Kakade; Bapurao B. Shingate; Murlidhar S. Shingare

2010-01-01

178

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

PubMed

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

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

2011-01-01

179

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

PubMed Central

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

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

2013-01-01

180

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

PubMed

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

Daud, N K; Hameed, B H

2010-04-15

181

Study of temperature-programmed desorption of tert-butylamine to measure the surface acidity of solid catalysts  

SciTech Connect

In this paper, the technique of temperature-programmed desorption of tert-butylamine is described to measure the surface acidity of solid catalysts. The use of this base has advantages over the use of ammonia, pyridine, and n-butylamine. The desorption measurement is carried out by two methods, gas chromatography and thermogravimetry, and the advised conditions are described for both methods. Catalysts of SiO{sub 2}/Al{sub 2}O{sub 3}, bifunctionals of Ni-SiO{sub 2}/Al{sub 2}O{sub 3}, and a commercial cracking zeolite have been studied. A comparison of the desorption results with those of the other acidity measurement techniques (such as titration with n-butylamine in the liquid phase and kinetic measurement of isomerization of n-butenes as the test reaction) allows the acidity measured with tert-butylamine desorption to be classified as strong, corresponding to the active sites in most of the reactions among the hydrocarbon compounds catalyzed by acids.

Aguayo, A.T.; Arandes, J.M.; Olazar, M.; Bilbao, J. (Dept. de Ingenieria Quimica, Univ. del Pais, Vasco. Apartado 655, 48080 Bilbao (ES))

1991-08-01

182

Comparative study of CoFeNx/C catalyst obtained by pyrolysis of hemin and cobalt porphyrin for catalytic oxygen reduction in alkaline and acidic electrolytes  

NASA Astrophysics Data System (ADS)

Comparative studies of the oxygen reduction kinetics and mechanisms of CoFeNx/C catalysts have been conducted with rotating disk electrode (RDE) and rotating ring-disk electrode (RRDE) in aqueous acid and alkaline solutions, as well as acidic and alkaline polymer electrolytes. The CoFeNx/C catalysts in this study were obtained by the pyrolysis of hemin and a cobalt porphyrin. In an alkaline electrolyte, a larger electron transfer coefficient (0.63) was obtained in comparison to that in an acidic electrolyte (0.44), signifying a lower free energy barrier for oxygen reduction. The kinetic rate constant (2.69 × 10-2 cm s-1) for catalytic oxygen reduction in alkaline solution at 0.6 V (versus RHE) is almost 4 times larger than that in acidic solution (7.3 × 10-3 cm s-1). A synergetic catalytic mechanism is proposed. The overall reduction is a 4-electron reduction of oxygen. The obtained CoFeNx/C catalyst was further evaluated as a cathode catalyst in single fuel cells with acidic, neutral and alkaline electrolyte membranes. The order of the single cell performances either for power density or for stability is acidic > neutral > alkaline. The different behaviors of the CoFeNx/C catalyst in half cell and single cell are discussed.

Jiang, Rongzhong; Chu, Deryn

2014-01-01

183

Xanthan Sulfuric Acid: An Efficient Bio-Supported and Recyclable Solid Acid Catalyst for the Synthesis of 4,4-(Arylmethylene)bis(1 h-Pyrazol-5-ols)  

Microsoft Academic Search

A simple and efficient method has been developed for the synthesis of 4,4-(arylmethylene)bis(1H-pyrazol-5-ols) by the condensation reaction between substituted aldehydes, and 1-phenyl-3-methylpyrazol-5-one in the presence of Xanthan sulfuric acid (XSA) as a solid acid catalyst. This method is simple, cost effective, requires short reaction times, yields are excellent with high purity and the catalyst could be easily recycled.

B. Suresh Kuarm; B. Rajitha

2012-01-01

184

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

Code of Federal Regulations, 2012 CFR

...2012-07-01 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 programs—general. (a)...

2012-07-01

185

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

...2014-07-01 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 programs—general. (a)...

2014-07-01

186

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 programs—general. (a)...

2010-07-01

187

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 programs—general. (a)...

2013-07-01

188

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

Code of Federal Regulations, 2011 CFR

...2011-07-01 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 programs—general. (a)...

2011-07-01

189

Lewis acid catalyzed reactions of chiral imidazolidinones and oxazolidinones: insights on the role of the catalyst.  

PubMed

The mechanism proposed by Evans to justify the selectivity obtained in Lewis acid catalyzed Diels-Alder reactions of cyclopentadiene with acyloxazolidinones has been generalized and used in the rationalization of selectivities obtained in many other systems. However, we recently proposed an alternative mechanism, on the basis of open-chain mono- and bicomplexes, that avoids the need for chelates and explains the selectivity obtained by Evans. In this manuscript we apply our proposal to the catalyzed conjugated addition of amines to acylimidazolidinones, reported by Cardillo, and we clearly show that aluminum chelates are not involved in the reaction, as they induce no selectivity, while Cardillo observed high experimental selectivities. Our data equally show that bicomplexes with carbonyl parallel orientation, proposed by Cardillo to justify the experimental selectivity with nonchelating Lewis acids, indeed induce the opposite selectivity and have also to be dismissed. On the other hand, our mechanistic proposal allows for the full rationalization of the data obtained by Cardillo with aluminum, boron, or zinc Lewis acids and supports our previous proposal on DA cycloadditions of dienes to Evans chiral auxiliary derivatives. PMID:21786834

Duarte, Filipe J S; Bakalova, Snezhana M; Cabrita, Eurico J; Santos, A Gil

2011-09-01

190

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

191

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

2013-04-01

192

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

PubMed

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

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

2013-08-15

193

Amine functionalized K10 montmorillonite: a solid acid-base catalyst for the Knoevenagel condensation reaction.  

PubMed

Different amine functionalized K10 montmorillonites were hydrothermally fabricated by a simple method of treatment of the neat clay with different amine solutions and used as heterogeneous catalysts towards the Knoevenagel condensation reaction. Catalytic results show that the di-amine functionalized K10 montmorillonite exhibits high efficacy for promoting this reaction at room temperature and in the absence of a solvent. The solid catalyst was characterized using a variety of different techniques; including Fourier transform infrared spectroscopy (FT-IR), nitrogen physisorption measurements, (29)Si CP MAS NMR spectroscopy, NH3-temperature programmed desorption (NH3-TPD), X-ray powder diffraction (XRD), and field emission scanning electron microscopy (FESEM). The catalyst could be recycled and reused for several runs without any loss of inherent catalytic activity. PMID:23400041

Varadwaj, G Bishwa Bidita; Rana, Surjyakanta; Parida, K M

2013-04-14

194

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

Microsoft Academic Search

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

Rachid Tahir; Rachid Nazih

2001-01-01

195

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

2013-04-01

196

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

PubMed

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

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

2008-12-30

197

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

PubMed Central

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

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

2014-01-01

198

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

199

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

PubMed

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

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

2014-09-01

200

Polystyrene-bound Mn(T4PyP): a highly efficient and reusable catalyst for biomimetic oxidative decarboxylation of carboxylic acids with sodium periodate.  

PubMed

In this report, highly efficient oxidative decarboxylation of carboxylic acids with sodium periodate catalyzed by a supported manganese(III) porphyrin is described. In the presence of manganese(III) tetra(4-pyridyl)porphyrin supported on cross-linked chloromethylated polystyrene, [Mn(T4PyP)-CMP], as catalyst, carboxylic acids were converted to their corresponding carbonyl compounds via oxidative decarboxylation with sodium periodate using imidazole as axial ligand. The oxidation of anti-inflammatory drugs such Indomethacin and Ibuprofen was carried out successfully and the decarboxylated products were obtained. This catalyst can be reused several times without loss of its catalytic activity in the oxidation reactions. PMID:19359183

Moghadam, Majid; Tangestaninejad, Shahram; Mirkhani, Valiollah; Mohammadpoor-Baltork, Iraj; Sirjanian, Narges; Parand, Somayeh

2009-05-01

201

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

202

Effects of potassium addition on the acidity and reducibility of chromia\\/alumina dehydrogenation catalysts  

Microsoft Academic Search

Dehydrogenation catalysts based on chromia supported on ?-alumina, containing about 6wt.% of chromium and increasing amounts of potassium (up to 1.8wt.%), were prepared and characterised by means of several techniques, such as N2 adsorption at 77K, X-ray powder diffraction (XRPD), UV-Vis diffuse reflectance spectroscopy (DRS), electron paramagnetic resonance (EPR), temperature programmed reduction (TPR), microcalorimetry and chemical analyses. The catalytic behaviour

E. Rombi; M. G. Cutrufello; V. Solinas; S. De Rossi; G. Ferraris; A. Pistone

2003-01-01

203

PERFORMANCE OF ACIDIC MCM-LIKE ALUMINOSILICATE CATALYSTS IN PYROLYSIS OF POLYPROPYLENE  

Microsoft Academic Search

Mesoporous aluminosilicate catalysts having different Al\\/Si ratios were synthesized following a hydrothermal synthesis route and using different aluminum sources, such as aluminum nitrate and aluminum isopropoxide. These mesoporous materials have high surface areas, in the range of 520–1001 m\\/g, and exhibit Type IV nitrogen adsorption isotherms. EDS and Al MAS NMR results showed that aluminum was incorporated more effectively into the

Zeynep Obali; Naime Asli Sezgi; Timur Do?u

2008-01-01

204

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

205

Bio-inspired amino acid oxidation by a non-heme iron catalyst.  

PubMed

This study reports the kinetics and mechanism of Fe(III)-catalyzed oxidative decarboxylation and deamination of a series of acyclic (?-aminoisobutyric acid, ?-(methylamino)isobutyric acid, alanine, norvaline, and 2-aminobutyric acid) and cyclic (1-aminocyclopropane-1-carboxylic acid, 1-amino-1-cyclobutanecarboxylic acid, 1-aminocyclopentanecarboxylic acid, and 1-aminocyclohexanecarboxylicacid) amino acids using hydrogen peroxide, t-butyl hydroperoxide, iodosylbenzene, m-chloroperbenzoic acid, and peroxomonosulphate as oxidant in 75% DMF-25% water solvent mixture. Model complex [Fe(IV)O(SALEN)](•+) (SALENH2: N,N'-bis(salicylidene)ethylenediamine) was generated by the reaction of Fe(III)(SALEN)Cl and H2O2 in CH3CN at 278 K as reported earlier. This method provided us high-valent oxoiron species, stable enough to ensure the direct observation of the reaction with amino acids. PMID:23528571

Góger, Szabina; Bogáth, Dóra; Baráth, Gábor; Simaan, A Jalila; Speier, Gábor; Kaizer, József

2013-06-01

206

Transport activity-dependent intracellular sorting of the yeast general amino acid permease  

E-print Network

Intracellular trafficking of the general amino acid permease, Gap1p, of Saccharomyces cerevisiae is regulated by amino acid abundance. When amino acids are scarce Gap1p is sorted to the plasma membrane, whereas when amino ...

Cain, Natalie Elaine

207

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

208

Non-platinum group metal oxgyen reduction catalysts and their mechanism in both acid and alkaline media: The effect of the catalyst precursor and the ionomer on oxygen reduction  

NASA Astrophysics Data System (ADS)

Non-platinum catalysts are an attractive strategy for lowering the cost of fuel cells, but much more development is needed in order to replace platinum, especially at the cathode where oxygen is reduced. Research groups worldwide have donated material for a study in which precursor structure to catalyst activity correlations are made. The donated samples have been divided into three classes based on their precursor; macrocyclic chelates, small molecule, and polymeric precursors. The precursor is one activity-dictating factor among many, but it is one of the most influential. It was found that macrocyclic chelates on average produced the most active catalysts, having the highest limiting, diffusion-limited, kinetic, and exchange current densities, as well as the lowest overpotentials and H2O2 production. This suggests that the M-N4 atomic structure of the precursor remains largely static throughout heat treatment, as the M-Nx motif is the accepted active site conformation. The other classes were somewhat less active, but the breadth of precursor materials that range in structure and functionality, as well as low associated costs, make them attractive precursor materials. Careful precursor selection based on this analysis was applied to a new generation of catalyst derived from iron salt and 4-aminoantipyrine. An extensive investigation of the reduction of oxygen on the material performed in both acid and alkaline media, and it was found that reduction follows a two-step pathway. While the peroxide reducing step is also very fast, the first step is so rapid that, even at low active site density, the material is almost as active as platinum if all diffusion limitations are removed. In addition to bottom-up catalyst design, the catalyst:ionomer complex, by which catalyst is incorporated into the membrane electrode assembly, also affects reductive kinetics. A series of novel anionically conductive ionomers have been evaluated using a well-described cyanamide derived catalyst, and the ionomeric influence on activity was mechanistically evaluated. It was found that the water-uptake percentage of the ionomer and the ion exchange capacity has a major role in catalyzing the reaction. The ionomer content of the complex must balance ionic and electrical charge transfer, as well as manage a certain degree of hydration at the active site. In order for a catalyst to perform optimally in an operational fuel cell, design considerations must be addressed at the precursor, support, synthesis, morphological, and ionomer-complexing levels. If any level of design is neglected, catalytic performance will be sacrificed.

Robson, Michael H.

209

Vanadium Recovery by Leaching in Spent Catalysts for Sulfuric Acid Production Recuperação do Vanádio Contido em Catalisadores Gastos na Produção de Ácido Sulfúrico  

Microsoft Academic Search

Sulfuric acid plants often need catalyst replacement in order to cope with process improvements, removal of broken pellets, dust and moisture damaged particles. This removed material can not be discarded because has high amounts of vanadium. According to the Brazilian Environmental Authority this material must be stored under specified conditions. This situation requires large storing areas potentially useful for other

JOSÉ LUÍS MAGNANI; GEORGE CURY KACHAN; NEWTON LIBANIO FERREIRA

210

Polystyrene-bound Mn(T4PyP): A highly efficient and reusable catalyst for biomimetic oxidative decarboxylation of carboxylic acids with sodium periodate  

Microsoft Academic Search

In this report, highly efficient oxidative decarboxylation of carboxylic acids with sodium periodate catalyzed by a supported manganese(III) porphyrin is described. In the presence of manganese(III) tetra(4-pyridyl)porphyrin supported on cross-linked chloromethylated polystyrene, [Mn(T4PyP)-CMP], as catalyst, carboxylic acids were converted to their corresponding carbonyl compounds via oxidative decarboxylation with sodium periodate using imidazole as axial ligand. The oxidation of anti-inflammatory drugs

Majid Moghadam; Shahram Tangestaninejad; Valiollah Mirkhani; Iraj Mohammadpoor-baltork; Narges Sirjanian; Somayeh Parand

2009-01-01

211

Synthesis of tetrahydroisoquinolines and isochromans via Pictet–Spengler reactions catalyzed by Brønsted acid–surfactant-combined catalyst in aqueous media  

Microsoft Academic Search

Perfluorooctanesulfonic acid (PFOSA), Brønsted acid–surfactant-combined catalyst, efficiently catalyzes the Pictet–Spengler reactions of ?-arylethyl carbamate derivatives with aldehydes in water. The present reaction is accelerated by the addition of 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP). PFOSA in HFIP–water (10v\\/v%) is also successfully applied to the oxa-Pictet–Spengler reactions of ?-arylethyl alcohol compounds.

Akio Saito; Masaki Takayama; Aru Yamazaki; Junko Numaguchi; Yuji Hanzawa

2007-01-01

212

Reduction of high content of free fatty acid in sludge palm oil via acid catalyst for biodiesel production  

Microsoft Academic Search

In this study, sulphuric acid (H2SO4) was used in the pretreatment of sludge palm oil for biodiesel production by an esterification process, followed by the basic catalyzed transesterification process. The purpose of the pretreatment process was to reduce the free fatty acids (FFA) content from high content FFA (>23%) of sludge palm oil (SPO) to a minimum level for biodiesel

Adeeb Hayyan; Mohamed E. S. Mirghani; Nassereldeen A. Kabbashi; Noor Irma Nazashida Mohd Hakimi; Yosri Mohd Siran; Shawaluddin Tahiruddin

2011-01-01

213

6- endo-dig Cyclization of heteroarylesters to alkynes promoted by Lewis acid catalyst in the presence of Brønsted acid  

Microsoft Academic Search

We report a regiocontrolled 6-endo-dig cyclization of 2-(2-arylethynyl)heteroaryl esters occurred under Brønsted acidic conditions and in the presence of a catalytic amount of Lewis acids such as Cu(OTf)2, AuCl3, or (CF3CO2)Ag. A variety of heterocyclic lactones are readily prepared in excellent yields.

Malik Hellal; Jean-Jacques Bourguignon; Frédéric J.-J. Bihel

2008-01-01

214

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

NASA Astrophysics Data System (ADS)

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

Qian, Huayu; Huang, Huajie; Wang, Xin

2015-02-01

215

Design of an effective bifunctional catalyst organotriphosphonic acid-functionalized ferric alginate (ATMP-FA) and optimization by Box-Behnken model for biodiesel esterification synthesis of oleic acid over ATMP-FA.  

PubMed

Biodiesel production has become an intense research area because of rapidly depleting energy reserves and increasing petroleum prices together with environmental concerns. This paper focused on the optimization of the catalytic performance in the esterification reaction of oleic acid for biodiesel production over the bifunctional catalyst organotriphosphonic acid-functionalized ferric alginate ATMP-FA. The reaction parameters including catalyst amount, ethanol to oleic acid molar ratio and reaction temperature have been optimized by response surface methodology (RSM) using the Box-Behnken model. It was found that the reaction temperature was the most significant factor, and the best conversion ratio of oleic acid could reach 93.17% under the reaction conditions with 9.53% of catalyst amount and 8.62:1 of ethanol to oleic acid molar ratio at 91.0°C. The research results show that two catalytic species could work cooperatively to promote the esterification reaction, and the bifunctional ATMP-FA is a potential catalyst for biodiesel production. PMID:25310862

Liu, Wei; Yin, Ping; Liu, Xiguang; Qu, Rongjun

2014-12-01

216

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

PubMed

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

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

2013-12-21

217

Structural and electrochemical characterization of carbon supported Pt-Pr catalysts for direct ethanol fuel cells prepared using a modified formic acid method in a CO atmosphere.  

PubMed

Pt-Pr/C electrocatalysts were prepared using a modified formic acid method, and their activity for carbon monoxide and ethanol oxidation was compared to Pt/C. No appreciable alloy formation was detected by XRD analysis. By TEM measurements it was found that Pt particle size increases with an increasing Pr content in the catalysts and with decreasing metal precursor addition time. XPS measurements indicated Pt segregation on the catalyst surface and the presence of Pr2O3 and PrO2 oxides. The addition of Pr increased the electro-catalytic activity of Pt for both CO and CH3CH2OH oxidation. The enhanced activity of Pt-Pr/C catalysts was ascribed to both an electronic effect, caused by the presence of Pr2O3, and the bi-functional mechanism, caused by the presence of PrO2. PMID:23752757

Corradini, Patricia Gon; Antolini, Ermete; Perez, Joelma

2013-07-28

218

Monomeric metal aqua complexes in the interlayer space of montmorillonites as strong Lewis acid catalysts for heterogeneous carbon-carbon bond-forming reactions.  

PubMed

Montmorillonite-enwrapped copper and scandium catalysts (Cu(2+)- and Sc(3+)-monts) were easily prepared by treating Na(+)-mont with the aqueous solution of the copper nitrate and scandium triflate, respectively. The resulting Cu(2+)- and Sc(3+)-monts showed outstanding catalytic activities for a variety of carbon-carbon bond-forming reactions, such as the Michael reaction, the Sakurai-Hosomi allylation, and the Diels-Alder reaction, under solvent-free or aqueous conditions. The remarkable activity of the mont catalysts is attributable to the negatively charged silicate layers that are capable of stabilizing metal cations. Furthermore, these catalysts were reusable without any appreciable loss in activity and selectivity. The Cu(2+)-mont-catalyzed Michael reaction proceeds via a ternary complex in which both the 1,3-dicarbonyl compound and the enone are coordinated to a Lewis acid Cu(2+) center. PMID:15551316

Kawabata, Tomonori; Kato, Masaki; Mizugaki, Tomoo; Ebitani, Kohki; Kaneda, Kiyotomi

2004-12-17

219

Silica sulfuric acid: a reusable solid catalyst for one pot synthesis of densely substituted pyrrole-fused isocoumarins under solvent-free conditions  

PubMed Central

Summary A convenient and efficient methodology for the synthesis of densely substituted pyrrole-fused isocoumarins, which employs solid-supported silica sulfuric acid (SSA) as catalyst, has been developed. When the mixture of ninhydrin adducts of acetylacetone/ethyl acetoacetate and primary amines was heated on the solid surface of SSA under solvent-free conditions, the pyrrole-fused isocoumarins were formed in good yields. This synthetic method has several advantages such as the employment of solvent-free reaction conditions without the use of any toxic reagents and metal catalysts, the ease of product isolation, the use of a recyclable catalyst, the low cost, the easy availability of the starting materials, and the excellent yields of products. PMID:24367398

Pathak, Sudipta; Debnath, Kamalesh

2013-01-01

220

An NMR study of acid sites on chlorided alumina catalysts using trimethylphosphine as a probe  

Microsoft Academic Search

The MAS-NMR spectra of adsorbed trimethylphosphine (TMP) were used to determine the concentration of Brønsted and Lewis acid sites on pure and chlorinated?-Al2O3 samples. Chlorination with CHCl3,CCl4 or AlCl3 promoted the formation of Brønsted acid centers, which are characterized by the protonated adduct of TMP. This adduct has a31P chemical shift of ca. -3.8 ppm and a JP-H scalar coupling

Hong Sang; Hon Yue Chu; Jack H. Lunsford

1994-01-01

221

3D-nanoarchitectured Pd/Ni catalysts prepared by atomic layer deposition for the electrooxidation of formic acid.  

PubMed

Three-dimensionally (3D) nanoarchitectured palladium/nickel (Pd/Ni) catalysts, which were prepared by atomic layer deposition (ALD) on high-aspect-ratio nanoporous alumina templates are investigated with regard to the electrooxidation of formic acid in an acidic medium (0.5 M H2SO4). Both deposition processes, Ni and Pd, with various mass content ratios have been continuously monitored by using a quartz crystal microbalance. The morphology of the Pd/Ni systems has been studied by electron microscopy and shows a homogeneous deposition of granularly structured Pd onto the Ni substrate. X-ray diffraction analysis performed on Ni and NiO substrates revealed an amorphous structure, while the Pd coating crystallized into a fcc lattice with a preferential orientation along the [220]-direction. Surface chemistry analysis by X-ray photoelectron spectroscopy showed both metallic and oxide contributions for the Ni and Pd deposits. Cyclic voltammetry of the Pd/Ni nanocatalysts revealed that the electrooxidation of HCOOH proceeds through the direct dehydrogenation mechanism with the formation of active intermediates. High catalytic activities are measured for low masses of Pd coatings that were generated by a low number of ALD cycles, probably because of the cluster size effect, electronic interactions between Pd and Ni, or diffusion effects. PMID:24605281

Assaud, Loïc; Monyoncho, Evans; Pitzschel, Kristina; Allagui, Anis; Petit, Matthieu; Hanbücken, Margrit; Baranova, Elena A; Santinacci, Lionel

2014-01-01

222

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. PMID:22355659

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

2011-01-01

223

Identification of the Gene at the pmg Locus, Encoding System II, the General Amino Acid  

E-print Network

Identification of the Gene at the pmg Locus, Encoding System II, the General Amino Acid Transporter of the gene at the pmg locus, encoding system II, the general amino acid transporter in Neurospora crassa a deficiency in a transport system for a broad range of amino acids. We have isolated a gene that encodes

Bowman, Barry

224

Oxidative Degradation of Different Chlorinated Phenoxyalkanoic Acid Herbicides by a Hybrid ZrO2 Gel-Derived Catalyst without Light Irradiation.  

PubMed

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

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

2015-01-14

225

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

PubMed

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

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

2006-05-01

226

Catalyst Alloys Processing  

NASA Astrophysics Data System (ADS)

Catalysts are one of the key materials used for diamond formation at high pressures. Several such catalyst products have been developed and applied in China and around the world. The catalyst alloy most widely used in China is Ni70Mn25Co5 developed at Changsha Research Institute of Mining and Metallurgy. In this article, detailed techniques for manufacturing such a typical catalyst alloy will be reviewed. The characteristics of the alloy will be described. Detailed processing of the alloy will be presented, including remelting and casting, hot rolling, annealing, surface treatment, cold rolling, blanking, finishing, packaging, and waste treatment. An example use of the catalyst alloy will also be given. Industrial experience shows that for the catalyst alloy products, a vacuum induction remelt furnace can be used for remelting, a metal mold can be used for casting, hot and cold rolling can be used for forming, and acid pickling can be used for metal surface cleaning.

Tan, Xincai

2014-10-01

227

General Analytical Procedure for Determination of Acidity Parameters of Weak Acids and Bases  

PubMed Central

The paper presents a new convenient, inexpensive, and reagent-saving general methodology for the determination of pKa values for components of the mixture of diverse chemical classes weak organic acids and bases in water solution, without the need to separate individual analytes. The data obtained from simple pH-metric microtitrations are numerically processed into reliable pKa values for each component of the mixture. Excellent agreement has been obtained between the determined pKa values and the reference literature data for compounds studied.

Pilarski, Bogus?aw; Kaliszan, Roman; Wyrzykowski, Dariusz; M?odzianowski, Janusz; Bali?ska, Agata

2015-01-01

228

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

229

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  

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

230

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

2013-12-01

231

Transport activity dependent regulation of the yeast general amino acid permease  

E-print Network

The general amino acid permease Gap1p of Saccharomyces cerevisiae scavenges amino acids from the extracellular medium for use as nitrogen sources in starvation conditions. Because unlimited uptake of both naturally occurring ...

Cain, Natalie E. (Natalie Elaine)

2011-01-01

232

Supported 12-tungstophosphoricacid: A recoverable solid acid catalyst for liquid phase Friedel–Crafts alkylation of phenol  

Microsoft Academic Search

Friedel–Crafts alkylation reactions such as tert-butylation, iso-propylation and sec-butylation of phenol have been carried out over 12-tungstophosphoricacid supported onto neutral alumina under mild conditions by varying different parameters. The supported catalysts were characterized by various physicochemical techniques such as FT-IR, TGA, and XPS analysis. The catalyst shows significantly high conversion and selectivity towards the important products. The catalysts were efficiently

Nikunj Bhatt; Anjali Patel

2011-01-01

233

Effects of metal ions on the hydrolysis of bamboo biomass in 1-butyl-3-methylimidazolium chloride with dilute acid as catalyst.  

PubMed

In this study, the effects of six metal ions including Na+, K+, Mg2+, Ca2+, Cu2+ and Fe3+ on hydrolysis of bamboo biomass by diluted hydrochloride acid (HCl) in ionic liquid [C4mim]Cl under mild conditions was investigated. These metal ions as co-catalysts exhibited significant effects on accelerating the hydrolysis process and improving the yield of total reducing sugar compared to single diluted hydrochloride acid hydrolysis in [C4mim]Cl at the same conditions. The most effective ion was Cu2+ and the total reducing sugar yield of 67.1% was achieved at 100 °C with CuCl2 as co-catalyst after 4-h reaction. The total reducing sugar yield was increased by about 7% and the reaction time was decreased by 3 h. The kinetic model was also investigated to give an insight into the mechanism of hydrolysis process. PMID:25444883

Wang, Nan; Zhang, Jie; Wang, Honghui; Li, Qiang; Wei, Sun'an; Wang, Dan

2014-12-01

234

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

PubMed

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

Salavati-Niasari, Masoud; Javidi, Jaber

2012-11-01

235

Preparation and evaluation of advanced catalysts for phosphoric acid fuel cells  

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

236

Catalyst-free tandem Michael addition/decarboxylation of (thio)coumarin-3-carboxylic acids with indoles: facile synthesis of indole-3-substituted 3,4-dihydro(thio)coumarins.  

PubMed

The tandem Michael addition/decarboxylation of (thio)coumarin-3-carboxylic acids with indoles has been developed and the biologically important indole-3-substituted dihydrocoumarins were obtained in good to excellent yields under catalyst-free conditions. PMID:24589942

Shao, Zhuzhou; Xu, Lubin; Wang, Liang; Wei, Hongtao; Xiao, Jian

2014-04-14

237

One-pot synthesis of dihydropyrimidones using silica-supported heteropoly acid as an efficient and reusable catalyst: Improved protocol conditions for the Biginelli reaction  

Microsoft Academic Search

An efficient synthesis of 3,4-dihydropyrimidinones or thiones (DHPMs) is described, using silica-supported heteropoly acid H3PW12O40\\/SiO2 (PW\\/SiO2) for the first time as the catalyst from an aldehyde, ?-keto ester and urea or thiourea in acetonitrile. Compared to the classical Biginelli reaction conditions, this method consistently has the advantage of excellent yields, mild reaction conditions, ease of workup, survival of different functional

Ezzat Rafiee; Fomaida Shahbazi

2006-01-01

238

Perfluorosulfonic acid membrane catalysts for optical sensing of anhydrides in the gas phase.  

PubMed

Continuous, on-site monitoring of personal exposure levels to occupational chemical hazards in ambient air is a long-standing analytical challenge. Such monitoring is required to institute appropriate health measures but is often limited by the time delays associated with batch air sampling and the need for off-site instrumental analyses. In this work, we report on the first attempt to use the catalytic properties of perfluorosulfonic acid (PSA) membranes to obtain a rapid, selective, and highly sensitive optical response to trimellitic anhydride (TMA) in the gas phase for portable sensor device application. TMA is used as starting material for various organic products and is recognized to be an extremely toxic agent by the National Institute for Occupational Safety and Health (NIOSH). Resorcinol dye is shown to become immobilized in PSA membranes and diffusionally constrain an orange brown product that results from acid-catalyzed reaction with more rapidly diffusing TMA molecules. FTIR, UV/vis, reaction selectivity to TMA versus trimellitic acid (TMLA), and homogeneous synthesis are used to infer 5,7- dihydroxyanthraquinone-2-carboxylic acid as the acylation product of the reaction. The color response has a sensitivity to at least 3 parts per billion (ppb) TMA exposure and, in addition to TMLA, excludes maleic anhydride (MA) and phthalic anhydride (PA). Solvent extraction at long times is used to determine that the resorcinol extinction coefficient in 1100 EW PSA membrane has a value of 1210 m(2)/g at 271.01 nm versus a value of 2010 m(2)/g at 275.22 nm in 50 vol% ethanol/water solution. The hypsochromic wavelength shift and reduced extinction coefficient suggest that the polar perfluorosulfonic acid groups in the membrane provide the thermodynamic driving force for diffusion and immobilization. At a resorcinol concentration of 0.376 g/L in the membrane, a partition coefficient of nearly unity is obtained between the membrane and solution concentrations and a maximum conversion rate of one ambient TMA molecule for every two membrane-immobilized resorcinol molecules is observed in 15 min. PMID:20560534

Ayyadurai, Subasri M; Worrall, Adam D; Bernstein, Jonathan A; Angelopoulos, Anastasios P

2010-07-15

239

Preparation and characterization of hydrophobic TiO(2) pillared clay: the effect of acid hydrolysis catalyst and doped Pt amount on photocatalytic activity.  

PubMed

Titanium hydrate sols were prepared using different acid hydrolysis catalysts, i.e., acetic acid and hydrochloric acid. The platinum-doped TiO(2) sol-gels were also synthesized by adding K(2)PtCl(6) into the titanium hydrate sols. The hydrophobic montmorillonite clay, treated with organic cationic surfactant, i.e., hexadecyltrimethylammonium bromide, was used as a template to prepare TiO(2) pillared photocatalyst with the above sols. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDX) were employed to characterize the resulting photocatalysts. The adsorption performance and photoactivity of prepared pillared clays were studied by using methyl orange as a model organic pollutant. The preliminary results indicated that the hydrophobic TiO(2) pillared clay prepared with acetic acid as the acid hydrolysis catalysts possessed higher photocatalytic activity than that with hydrochloric acid. Due to the excellent sedimentation property of the clay, the resulting pillared photocatalyst is easily recovered and reused in the postrun treatment. Also the doping of platinum into the hydrophobic photocatalyst can increase the photocatalytic activity significantly. PMID:18279880

Ding, Xuejun; An, Taicheng; Li, Guiying; Zhang, Shanqing; Chen, Jiaxin; Yuan, Jianmei; Zhao, Huijun; Chen, Hui; Sheng, Guoying; Fu, Jiamo

2008-04-15

240

Positive selection of general amino acid permease mutants in Saccharomyces cerevisiae.  

PubMed Central

It was found that D-stereoisomers of natural amino acids inhibit the growth of Saccharomyces cerevisiae cells. Kinetic and genetic evidence showed that d-amino acids enter the cell by the general amino acid permease. Two classes of S. cerevisiae mutants resistant to d-amino acids were isolated. One class of mutants appeared to be defective in the general amino acid permease specified by the gene gap. In the second class, the activity of general amino acid permease was affected by ammonium ions. Mutants of the second class were isolated in a yeast strain with the general amino acid permease insensitive to the presence of ammonium ions in culture media. The mutation affecting the permease, amc, occurred in a locus unlinked to gap. PMID:1089636

Rytka, J

1975-01-01

241

Iron oxide nanoparticles immobilized to mesoporous NH2-SiO2 spheres by sulfonic acid functionalization as highly efficient catalysts  

NASA Astrophysics Data System (ADS)

A novel SiO2 nanosphere was synthesized by the post-synthetic grafting of sulfonic acid groups on to anionic-surfactant-templated mesoporous NH2-silica (AMAS). This one-pot post-functionalization strategy allowed more metal ions to be homogeneously anchored into the channel of the meso-SiO2 nanosphere. After hydrothermal and calcination treatment, the in situ growth of ?-Fe2O3 on sulfonic acid-functionalized mesoporous NH2-SiO2 (SA-AMAS) exhibited much higher activity in the visible-light assisted Fenton reaction at neutral pH than that for AMAS or meso-SiO2 nanospheres. By analysis, the grafted sulfonic acid group can not only enhance the acid strength of the catalyst, but can also bring more orbital-overlapping between the active sites (FeII and FeIII) and the surface peroxide species, to facilitate the decomposition of H2O2 to hydroxyl radical. The present results provide opportunities for developing heterogeneous catalysts with high-performance in the field of green chemistry and environmental remediation.A novel SiO2 nanosphere was synthesized by the post-synthetic grafting of sulfonic acid groups on to anionic-surfactant-templated mesoporous NH2-silica (AMAS). This one-pot post-functionalization strategy allowed more metal ions to be homogeneously anchored into the channel of the meso-SiO2 nanosphere. After hydrothermal and calcination treatment, the in situ growth of ?-Fe2O3 on sulfonic acid-functionalized mesoporous NH2-SiO2 (SA-AMAS) exhibited much higher activity in the visible-light assisted Fenton reaction at neutral pH than that for AMAS or meso-SiO2 nanospheres. By analysis, the grafted sulfonic acid group can not only enhance the acid strength of the catalyst, but can also bring more orbital-overlapping between the active sites (FeII and FeIII) and the surface peroxide species, to facilitate the decomposition of H2O2 to hydroxyl radical. The present results provide opportunities for developing heterogeneous catalysts with high-performance in the field of green chemistry and environmental remediation. Electronic supplementary information (ESI) available: BET surface area and textural data, degradation results, FTIR spectra, TEM images, and element analysis. See DOI: 10.1039/c4nr05884d

Zhang, Guoliang; Qin, Lei; Wu, Yujiao; Xu, Zehai; Guo, Xinwen

2014-12-01

242

An improved general amino-acid replacement matrix Si Quang LE & Olivier GASCUEL*  

E-print Network

1/36 An improved general amino-acid replacement matrix Si Quang LE & Olivier GASCUEL* Méthodes et manuscript, published in "Molecular Biology and Evolution 25, 7 (2008) 1307-1320" #12;2/36 Abstract Amino-acid://atgc.lirmm.fr/LG. Keywords: amino-acid substitutions; replacement matrices; JTT ; WAG ; maximum-likelihood estimations

Paris-Sud XI, Université de

243

A General Model for Amino Acid Interaction Omar GACI and Stefan BALEV  

E-print Network

A General Model for Amino Acid Interaction Networks Omar GACI and Stefan BALEV Abstract are the protein's amino acids and whose edges are the interactions between them. Using a graph theory approach, we's amino acids which form chemical bonds. In this paper we identify some of the properties of the network

Boyer, Edmond

244

An Improved General Amino Acid Replacement Matrix Si Quang Le and Olivier Gascuel  

E-print Network

An Improved General Amino Acid Replacement Matrix Si Quang Le and Olivier Gascuel Me´thodes et Algorithmes pour la Bioinformatique, LIRMM, CNRS, Universite´ Montpellier II, Montpellier, France Amino acid implementation can be downloaded from http:// atgc.lirmm.fr/LG. Introduction Amino acid replacement matrices

Paris-Sud XI, Université de

245

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

246

EFFECTS OF LEWIS ACID CATALYSTS ON THE HYDROGENATION AND CRACKING OF TWO-RING AROMATIC AND HYDROAROMATIC STRUCTURES RELATED TO COAL  

SciTech Connect

An investigation was carried out of the hydrogenation and cracking of two-ring aromatic and hydroaromatic compounds catalyzed by ZnCl{sub 2} and AlCl{sub 3}. The rates of both processes are strongly affected by the Bronsted acidity of the active catalyst [e.g., H{sup +}(MX{sub n}Y){sup -}] and the Bronsted basicity of the aromatic portions of the reactant, the latter characteristic being enhanced by either methyl or hydroxyl substitution. The source of hydrogen used for hydrogenation depends on the choice of catalyst. In the presence of AlCl{sub 3}, Scholl condensation of aromatic nuclei serves as the principle source of hydrogen. Molecular hydrogen is used exclusively, though, when hydrogenation is catalyzed by ZnCl{sub 2}. The formation of reaction products and the trends in reactant reactivity are discussed on the basis of carbonium ion mechanisms.

Salim, Sadie S.; Bell, Alexis T.

1980-11-01

247

Iron oxide nanoparticles immobilized to mesoporous NH2-SiO2 spheres by sulfonic acid functionalization as highly efficient catalysts.  

PubMed

A novel SiO2 nanosphere was synthesized by the post-synthetic grafting of sulfonic acid groups on to anionic-surfactant-templated mesoporous NH2-silica (AMAS). This one-pot post-functionalization strategy allowed more metal ions to be homogeneously anchored into the channel of the meso-SiO2 nanosphere. After hydrothermal and calcination treatment, the in situ growth of ?-Fe2O3 on sulfonic acid-functionalized mesoporous NH2-SiO2 (SA-AMAS) exhibited much higher activity in the visible-light assisted Fenton reaction at neutral pH than that for AMAS or meso-SiO2 nanospheres. By analysis, the grafted sulfonic acid group can not only enhance the acid strength of the catalyst, but can also bring more orbital-overlapping between the active sites (Fe(II) and Fe(III)) and the surface peroxide species, to facilitate the decomposition of H2O2 to hydroxyl radical. The present results provide opportunities for developing heterogeneous catalysts with high-performance in the field of green chemistry and environmental remediation. PMID:25482204

Zhang, Guoliang; Qin, Lei; Wu, Yujiao; Xu, Zehai; Guo, Xinwen

2015-01-21

248

Amino acids regulate the transcription, internal sorting, and intrinsic activity of the general amino acid permease (GAP1) in S. cerevisiae  

E-print Network

The high capacity general amino acid permease in Saccharomyces cerevisiae (GAP1) is regulated such that it actively imports amino acids into the cell from the extracellular medium only when internal amino acid levels are ...

Risinger, April L. (April Lynn)

2007-01-01

249

Amino acid/KI as multi-functional synergistic catalysts for cyclic carbonate synthesis from CO2 under mild reaction conditions: a DFT corroborated study.  

PubMed

Naturally occurring amino acids were identified as efficient co-catalysts for the alkali metal halide-mediated synthesis of cyclic carbonates from carbon dioxide and epoxides under mild, solvent free reaction conditions. The binary system of histidine/potassium iodide gave an appreciable turnover number of 535 for propylene oxide in 3 h. Detailed studies evaluating a variety of amino acids revealed that the basic amino acids afforded better conversion rates. The formation of a seven membered ring involving the zwitterionic ends of the amino acid, the metal halide, and the epoxide was considered to accelerate the catalysis rate. Density functional theory calculations were performed for the first time on amino acid co-catalyzed cycloaddition to provide further evidence for this hypothesis. The iodide ions of the alkali metal halide displayed excellent synergism with the hydrogen bonding groups of the amino acids in the production of cyclic carbonates, whereas bromide and chloride anions functioned less efficiently. The utilization of amino acids to enhance the catalytic activity of the cheap and eco-friendly alkali metal halides for cyclic carbonate synthesis represents a cost-effective, greener route towards the chemical fixation of carbon dioxide. PMID:24270098

Roshan, Kuruppathparambil Roshith; Kathalikkattil, Amal Cherian; Tharun, Jose; Kim, Dong Woo; Won, Yong Sun; Park, Dae Won

2014-02-01

250

Regeneration of three-way automobile catalysts using biodegradable metal chelating agent--S, S-ethylenediamine disuccinic acid (S, S-EDDS).  

PubMed

Regeneration of the activity of three-way catalytic converters (TWCs) was tested for the first time using a biodegradable metal chelating agent (S, S-ethylenediamine disuccinic acid (S, S-EDDS). The efficiency of this novel environmentally friendly solvent in removing various contaminants such as P, Zn, Pb, Cu and S from commercial aged three-way catalysts, and improving their catalytic performance towards CO and NO pollutants removal has been investigated. Four samples of catalysts from the front and rear inlets of two different TWCs with different mileages and aged under completely different driving conditions were investigated. The catalysts were characterized using various techniques, such as X-ray diffraction (XRD), Scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) surface area measurements (N(2) adsorption at 77 K). Quantitative ICP-MS analyses and SEM-EDS studies show the removal of Zn, P and Pb. SEM-EDS images obtained at low magnification (50 ?m) showed considerable differences in the surface morphology and composition after washing with S, S-EDDS. However, XRD studies indicated neither little to no removal of major contaminant compound phases nor major structural changes due to washing. Correspondingly, little or no enhancement in BET surface area was observed between the used and washed samples. Light-off curves show that the regeneration procedure employed can effectively improve the catalytic performance towards NO pollutant. PMID:21177030

Subramanian, B; Christou, S Y; Efstathiou, A M; Namboodiri, V; Dionysiou, D D

2011-02-28

251

Solar active fire clay based hetero-Fenton catalyst over a wide pH range for degradation of Acid Violet 7.  

PubMed

Fe(III) immobilized fire clay (Fe-FC) was prepared using ferric nitrate by solid state dispersion method and this hetero-Fenton catalyst was applied for the degradation of Acid Violet 7 (AV 7) under natural sunlight. The 26% ferric nitrate loaded fire clay was found to be most efficient. The experimental conditions such as solution pH, H2O2 concentration for efficient degradation of AV 7 have been determined. Unlike Fenton catalyst, Fe-FC is photoactive over a wide pH range of 3-7. This catalyst was found to be stable and reusable. The GC-MS analysis of experimental solutions during irradiation revealed the formation of 2,8-diaminonaphthalene-1,3,6-triol, 8-aminonaphthalene-1,2,3,6-tetrol, 2-aminonaphthalene-1,3,6,8-tetrol and 2-aminobenzene-1,3-diol/5-aminonbenzene-1,3-diol/ 2-aminobenzene-1,4-diol as intermediates. The 26% ferric nitrate loaded fire clay was characterized by XRD, ICP-AES, BET surface area, FT-IR, SEM-EDS and UV-DRS studies. PMID:22655369

Muthuvel, Inbasekaran; Krishnakumar, Balu; Swaminathan, Meenakshisundaram

2012-01-01

252

Kinetic resolution of racemic 2-hydroxy-?-butyrolactones by asymmetric esterification using diphenylacetic acid with pivalic anhydride and a chiral acyl-transfer catalyst.  

PubMed

Various optically active 2-hydroxy-?-butyrolactone derivatives are produced via the kinetic resolution of racemic 2-hydroxy-?-butyrolactones with diphenylacetic acid using pivalic anhydride and (R)-benzotetramisole ((R)-BTM), a chiral acyl-transfer catalyst. Importantly, the substrate scope of this novel protocol is fairly broad (12 examples, s-value; up to over 1000). In addition, we succeeded in disclosing the reaction mechanism to afford high enantioselectivity using theoretical calculations and expounded on the substituent effects at the C-3 positions in 2-hydroxylactones. PMID:23461674

Nakata, Kenya; Gotoh, Kouya; Ono, Keisuke; Futami, Kengo; Shiina, Isamu

2013-03-15

253

pKa Modulation of the Acid/Base Catalyst within GH32 and GH68: A Role in Substrate/Inhibitor Specificity?  

PubMed Central

Glycoside hydrolases of families 32 (GH32) and 68 (GH68) belong to clan GH-J, containing hydrolytic enzymes (sucrose/fructans as donor substrates) and fructosyltransferases (sucrose/fructans as donor and acceptor substrates). In GH32 members, some of the sugar substrates can also function as inhibitors, this regulatory aspect further adding to the complexity in enzyme functionalities within this family. Although 3D structural information becomes increasingly available within this clan and huge progress has been made on structure-function relationships, it is not clear why some sugars bind as inhibitors without being catalyzed. Conserved aspartate and glutamate residues are well known to act as nucleophile and acid/bases within this clan. Based on the available 3D structures of enzymes and enzyme-ligand complexes as well as docking simulations, we calculated the pKa of the acid-base before and after substrate binding. The obtained results strongly suggest that most GH-J members show an acid-base catalyst that is not sufficiently protonated before ligand entrance, while the acid-base can be fully protonated when a substrate, but not an inhibitor, enters the catalytic pocket. This provides a new mechanistic insight aiming at understanding the complex substrate and inhibitor specificities observed within the GH-J clan. Moreover, besides the effect of substrate entrance on its own, we strongly suggest that a highly conserved arginine residue (in the RDP motif) rather than the previously proposed Tyr motif (not conserved) provides the proton to increase the pKa of the acid-base catalyst. PMID:22662155

Yuan, Shuguang; Le Roy, Katrien; Venken, Tom; Lammens, Willem; Van den Ende, Wim; De Maeyer, Marc

2012-01-01

254

pH-dependent release of trace elements including platinum group elements (PGEs) from gasoline and diesel catalysts  

NASA Astrophysics Data System (ADS)

The release of trace metals and platinum group elements (PGEs) from automobile exhaust catalysts represents a remarkable source of higly dispersed environmental contamination. Especially, PGEs have shown increasing research interest due to their possible bioaccessibility. In our research, we focused on leaching behaviour of trace metals from gasoline and diesel automobile catalysts. While catalysts for gasoline engines contain a mixture of Pt-Pd-Rh or Pd-Rh, catalysts for diesel engines are composed only of Pt. We used dust from two crushed gasoline and two crushed diesel catalysts (new and aged). The dust of gasoline catalysts contains significant concentrations of Pt (700 mg.kg-1), Pd (11 000 mg.kg-1) and Rh (700 mg.kg-1). And the dust of diesel catalysts are composed of Pt (3 900 mg.kg-1) and they contains negligible amounts of Pd dan Rh (< 0.5 mg.kg-1, < 0.1 mg.kg-1, respectively). To evaluate leaching of trace metals from dust we used pH-stat leaching test according to the European standard CEN/TS 14997. The concentrations of cations: PGEs (Pt, Pd a Rh), K, Na, Ca, Mg, Al, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb, La and Ce were determined by inductively coupled plasma mass spectrometry (ICP-MS) and atomic absorption spectrometry (AAS), and anions: F-, Cl-, SO42- and NO3- by high-performance liquid chromatography. Although the dusts from catalysts were relatively stable to acid/base influence, the leaching of trace metals from catalysts showed a dependence on pH. Generally, the highest concentrations were released under acidic conditions. The leaching of PGEs was higher for Pt in diesel catalysts and for Pd and Rh in gasoline catalysts. The highest concentrations of Zn and Pb were observed in old catalysts. The rare earth metals were released more from gasoline catalysts. Catalysts particles represent health risk especially with respect to their PGEs contents.

Sucha, Veronika; Mihaljevic, Martin; Ettler, Vojtech; Strnad, Ladislav

2014-05-01

255

Epoxidation catalyst and process  

DOEpatents

Disclosed herein is a catalytic method of converting alkenes to epoxides. This method generally includes reacting alkenes with oxygen in the presence of a specific silver catalyst under conditions suitable to produce a yield of the epoxides. The specific silver catalyst is a silver nanocrystal having a plurality of surface planes, a substantial portion of which is defined by Miller indices of (100). The reaction is performed by charging a suitable reactor with this silver catalyst and then feeding the reactants to the reactor under conditions to carry out the reaction. The reaction may be performed in batch, or as a continuous process that employs a recycle of any unreacted alkenes. The specific silver catalyst has unexpectedly high selectivity for epoxide products. Consequently, this general method (and its various embodiments) will result in extraordinarily high epoxide yields heretofore unattainable.

Linic, Suljo (Ann Arbor, MI); Christopher, Phillip (Ann Arbor, MI)

2010-10-26

256

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

257

Catalysts and method  

DOEpatents

An improved catlayst and method for the oxyhydrochlorination of methane is disclosed. The catalyst includes a pyrogenic porous support on which is layered as active material, cobalt chloride in major proportion, and minor proportions of an alkali metal chloride and of a rare earth chloride. On contact of the catalyst with a gas flow of methane, HC1 and oxygen, more than 60% of the methane is converted and of that converted more than 40% occurs as monochloromethane. Advantageously, the monochloromethane can be used to produce gasoline boiling range hydrocarbons with the recycle of HCl for further reaction. This catalyst is also of value for the production of formic acid as are analogous catalysts with lead, silver or nickel chlorides substituted for the cobalt chloride.

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

1991-01-01

258

Reuse of sewage sludge as a catalyst in ozonation--efficiency for the removal of oxalic acid and the control of bromate formation.  

PubMed

Sewage derived sludge is produced with an annual amount increase of 2% all over the world and it is an urgent issue to be addressed by human being. In the present study, sludge was converted into sludge-based catalyst (SBC) with ZnCl2 as activation agent and characterized by several methods (e.g., scanning electron microscope, X-ray photoelectron spectroscope and Fourier transform infrared spectroscope). Then it was used as a catalyst to enhance the removal of refractory organic matter, oxalic acid, and to control the formation of bromate (BrO3-) in bench semi-continuous ozonation experiments. The effects of various operating parameters on the control of BrO3- formation were investigated. Furthermore, the mechanism for the enhancement of organic matter removal and the control of BrO3- formation was discussed as well. Results indicate that the combination of SBC with ozone shows a strong synergistic effect, resulting in a notable improvement on oxalic acid removal. A crucial surface reaction mechanism for the enhancement of organic matter removal is proposed on the basis of negative effect of higher pH and no inhibition effect of tert-butanol. The control for BrO3- formation was demonstrated and the reason for its control in the process of O3/SBC is the combined effect of SBC reductive properties, ozone exposure decrease and hydrogen peroxide concentration increase. PMID:23021317

Wen, Gang; Pan, Zhi-Hui; Ma, Jun; Liu, Zheng-Qian; Zhao, Lei; Li, Jun-Jing

2012-11-15

259

Phosphomolybdic and phosphotungstic acids as efficient catalysts for the synthesis of bridged 1,2,4,5-tetraoxanes from ?-diketones and hydrogen peroxide.  

PubMed

Phosphomolybdic acid (PMA) and phosphotungstic acid (PTA) efficiently catalyze the addition of H2O2 to ?-diketones to form bridged 1,2,4,5-tetraoxanes. These reactions are not accompanied by the formation of monocyclic peroxides containing hydroxy and hydroperoxide groups or polymeric peroxides. The use of these catalysts made it possible to obtain bridged tetraoxanes from easily oxidizable benzoylacetone derivatives and ?-unsubstituted ?-diketones. The syntheses are scaled up to ten grams. The resulting peroxides can be easily isolated from the reaction mixture by column chromatography. The yield of tetraoxanes depends on the structure of ?-diketone and varies from 12 to 83%. NMR monitoring of two bridged 1,2,4,5-tetraoxanes synthesis was carried out. PMID:23446630

Terent'ev, Alexander O; Yaremenko, Ivan A; Vil', Vera A; Moiseev, Igor K; Kon'kov, Sergey A; Dembitsky, Valery M; Levitsky, Dmitri O; Nikishin, Gennady I

2013-04-28

260

Electron-Withdrawing Trifluoromethyl Groups in Combination with Hydrogen Bonds in Polyols: Brønsted Acids, Hydrogen-Bond Catalysts, and Anion Receptors  

SciTech Connect

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)3C6H3NH)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.

Shokri, Alireza; Wang, Xue B.; Kass, Steven R.

2013-06-26

261

Brönsted and Lewis acidity of the BF3/gamma-Al2O3 alkylation catalyst as revealed by solid-state NMR spectroscopy and DFT quantum chemical calculations.  

PubMed

Multinuclear solid-state NMR techniques and DFT quantum chemical calculations were employed to investigate the detailed structure of acid sites on the BF3/gamma-Al2O3 alkylation catalyst. The NMR experiment results indicate that gaseous BF3 is able to react with the hydroxyl groups present on the surface of gamma-Al2O3, leading to the formation of new Brönsted and Lewis acid sites. The 1H/11B and 1H/27Al TRAPDOR (TRAnsfer of Population in DOuble Resonance) experiments suggest that the 3.7 ppm signal in 1H NMR spectra of the BF3/gamma-Al2O3 catalyst is due to a bridging B-OH-Al group that acts as a Brönsted acid site of the catalyst. On the other hand, a Lewis acid site on the surface of the catalysts, as revealed by 31P MAS and 31P/27Al TRAPDOR NMR of adsorbed trimethylphosphine, is associated with three-coordinate -OBF2 species. 13C NMR of adsorbed 2-13C-acetone indicates that the Brönsted acid strength of the catalyst is slightly stronger than that of zeolite HZSM-5 but still weaker than that of 100% H2SO4, which is in good agreement with theoretical prediction. In addition, DFT calculations also reveal the detailed structure of various acid sites formed on the BF3/gamma-Al2O3 catalyst and the interaction of probe molecules with these sites. PMID:16852633

Yang, Jun; Zheng, Anmin; Zhang, Mingjin; Luo, Qing; Yue, Yong; Ye, Chaohui; Lu, Xin; Deng, Feng

2005-07-14

262

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

263

Bioleaching of spent fluid catalytic cracking catalyst using Aspergillus niger  

Microsoft Academic Search

The use of the fungus Aspergillus niger for the bioleaching of heavy metals from spent catalyst was investigated, with fluid catalytic cracking (FCC) catalyst as a model. Bioleaching was examined in batch cultures with the spent catalysts at various pulp densities (1–12%). Chemical leaching was also performed using mineral acids (sulphuric and nitric acids) and organic acids (citric, oxalic and

Khin Moh Moh Aung; Yen-Peng Ting

2005-01-01

264

Bioleaching of spent fluid catalytic cracking catalyst using Aspergillus niger.  

PubMed

The use of the fungus Aspergillus niger for the bioleaching of heavy metals from spent catalyst was investigated, with fluid catalytic cracking (FCC) catalyst as a model. Bioleaching was examined in batch cultures with the spent catalysts at various pulp densities (1-12%). Chemical leaching was also performed using mineral acids (sulphuric and nitric acids) and organic acids (citric, oxalic and gluconic acids), as well as a mixture of organic acids at the same concentrations as that biogenically produced. It was shown that bioleaching realised higher metal extraction than chemical leaching, with A. niger mobilizing Ni (9%), Fe (23%), Al (30%), V (36%) and Sb (64%) at 1% pulp density. Extraction efficiency generally decreased with increased pulp density. Compared with abiotic controls, bioleaching gave rise to higher metal extractions than leaching using fresh medium and cell-free spent medium. pH decreased during bioleaching, but remained relatively constant in both leaching using fresh medium and cell-free spent medium, thus indicating that the fungus played a role in effecting metal extraction from the spent catalyst. PMID:15664080

Aung, Khin Moh Moh; Ting, Yen-Peng

2005-03-16

265

Incorporating Amino Acid Esters into Catalysts for Hydrogen Oxidation: Steric and Electronic Effects and the Role of Water as a Base  

SciTech Connect

Four derivatives of a hydrogen oxidation catalyst, [Ni(PCy2NBn-R2)]2+ (Cy=cyclohexyl, Bn=benzyl, R= OMe, COOMe, CO-Alanine-methyl ester or CO-Phenylalanine-methyl ester), have been prepared to investigate steric and electronic effects on catalysis. Each complex was characterized spectroscopically and electrochemically, and thermodynamic data were determined. Crystal structures are also reported for the -OMe and -COOMe derivatives. All four catalysts were found to be active for H2 oxidation. The methyl ester (R = COOMe) and amino acid ester containing complexes (R = CO-Alanine-methyl ester or CO-Phenylalanine-methyl ester) had slower rates (4 s-1) than that of the parent complex (10 s-1), in which R = H, consistent with the lower amine pKa’s and less favorable ?GH2’s found for these electron-withdrawing substituents. Dynamic processes for the amino acid ester containing complexes were also investigated and found not to hinder catalysis. The electron-donating methoxy ether derivative (R = OMe) was prepared to compare electronic effects and has a similar catalytic rate as the parent complex. In the course of these studies, it was found that water could act as a weak base for H2 oxidation, although catalytic turnover requires a significantly higher potential and utilizes a different sequence of catalytic steps than when using a base with a higher pKa. Importantly, these catalysts provide a foundation upon which larger peptides can be attached to [Ni(PCy2NBn2)2]2+ hydrogen oxidation catalysts in order to more fully investigate and implement the effects of the outer-coordination sphere. This work was funded by the DOE Office of Science Early Career Research Program through the Office of Basic Energy Sciences (SL and WJS), by the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences (JR), and by the US DOE Basic Energy Sciences, Chemical Sciences, Geoscience and Biosciences Division (AMA, AJ). Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

Lense, Sheri; Ho, Ming-Hsun; Chen, Shentan; Jain, Avijita; Raugei, Simone; Linehan, John C.; Roberts, John A.; Appel, Aaron M.; Shaw, Wendy J.

2012-10-08

266

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 PMID:19154421

Villemejane, Julien; Mir, Lluis M

2009-01-01

267

Natural DNA-modified graphene/Pd nanoparticles as highly active catalyst for formic acid electro-oxidation and for the Suzuki reaction.  

PubMed

Natural DNA has been considered as a building block for developing novel functional materials. It is abundant, renewable, and biodegradable and has a well-defined structure and conformation with many unique features, which are difficult to find in other polymers. Herein, calf thymus DNA modified graphene/Pd nanoparticle (DNA-G-Pd) hybrid materials are constructed for the first time using DNA as a mediator, and the prepared DNA-G-Pd hybrid shows high catalytic activity for fuel cell formic acid electro-oxidation and for organic Suzuki reaction. The main advantages of using DNA are not only because the aromatic nucleobases in DNA can interact through ?-? stacking with graphene basal surface but also because they can chelate Pd via dative bonding in such defined sites along the DNA lattice. Our results indicate that isolated, homogeneous, and ultrafine spherical Pd nanoparticles are densely in situ decorated on DNA-modified graphene surfaces with high stability and dispersibility. The prepared DNA-G-Pd hybrid has much greater activity and durability for formic acid electro-oxidation than the commercial Pd/C catalyst and polyvinylpyrrolidone-mediated graphene/Pd nanoparticle (PVP-G-Pd) hybrid used for direct formic acid fuel cells (DFAFCs). Besides, the DNA-G-Pd hybrid can also be an efficient and recyclable catalyst for the organic Suzuki reaction in aqueous solution under aerobic conditions without any preactivation. Since DNA can chelate various transition metal cations, this proof-of-concept protocol provides the possibility for the tailored design of other novel catalytic materials based on graphene with full exploitation of their properties. PMID:22973944

Qu, Konggang; Wu, Li; Ren, Jinsong; Qu, Xiaogang

2012-09-26

268

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

269

Molecular water oxidation catalyst  

DOEpatents

A dimeric composition of the formula: ##STR1## wherein L', L", L'", and L"" are each a bidentate ligand having at least one functional substituent, the ligand selected from bipyridine, phenanthroline, 2-phenylpyridine, bipyrimidine, and bipyrazyl and the functional substituent selected from carboxylic acid, ester, amide, halogenide, anhydride, acyl ketone, alkyl ketone, acid chloride, sulfonic acid, phosphonic acid, and nitro and nitroso groups. An electrochemical oxidation process for the production of the above functionally substituted bidentate ligand diaqua oxo-bridged ruthenium dimers and their use as water oxidation catalysts is described.

Gratzel, Michael (St. Sulpice, CH); Munavalli, Shekhar (Bel Air, MD); Pern, Fu-Jann (Lakewood, CO); Frank, Arthur J. (Lakewood, CO)

1993-01-01

270

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. PMID:24052844

Karimi-Jaberi, Zahed; Moaddeli, Mohammad Sadegh

2012-01-01

271

Melamine trisulfonic acid: A new, efficient and recyclable catalyst for the synthesis of 3,4-dihydropyrimidin-2(1 H)-ones\\/thiones in the absence of solvent  

Microsoft Academic Search

Melamine trisulfonic acid (MTSA) can be used as an efficient and recyclable catalyst for the promotion of the synthesis of 3,4-dihydropyrimidin-2(1H)-ones\\/thiones (DHPMs) in the absence of solvent. All reactions were performed at 80°C in good to high yields.

Farhad Shirini; Mohammad Ali Zolfigol; Jalal Albadi

2011-01-01

272

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

273

On the equilibrium nature of thermodesorption processes. TPD-NH3 studies of surface acidity of Ni/MgO-Al2O3 catalysts.  

PubMed

This article deals with a quantitative analysis of thermodesorption spectra of ammonia: a technique commonly applied to study the surface acidity of solids. The method used for determination of adsorption energy distributions of ammonia is the same as that published recently for the case of hydrogen thermodesorption (Panczyk, T.; et al. Langmuir 2005, 21, 7311). The developed theoretical expression describing the thermodesorption process is based on the statistical rate theory (SRT) and its analysis leads to the conclusion that majority of thermodesorption processes, carried out under flow conditions, are in fact quasi-equilibrium ones. Similar conclusion has already been drawn by some authors applying the classical absolute rate theory (ART) for analysis of thermodesorption data. This conclusion has important practical consequences. Namely, it greatly simplifies the quantitative analysis of thermodesorption processes since there is no need to use any kinetic approaches to that purpose. The quantitative analysis of thermodesorption spectra can thus be based on commonly accepted relations following from equilibrium thermodynamics. It is worth noting that in quasiequilibrium conditions either the SRT or the ART lead to this same expression with only a slightly different meaning of some constants. Thus, in quasiequilibrium conditions there is no need to decide which theoretical approach should be applied. As an illustration, the ammonia thermodesorption spectra from the modified nickel catalysts are analyzed. The catalysts were prepared by the coprecipitation method and differ by the amount of MgO and NiO, whereas the amount of Al(2)O(3) is constant and equals 30%. It was stated that the presence of MgO reduces the number of acid centers corresponding to high values of ammonia adsorption energy. PMID:16831004

Panczyk, Tomasz; Gac, Wojciech; Panczyk, Monika; Borowiecki, Tadeusz; Rudzinski, Wladyslaw

2006-07-18

274

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

275

The conversion of CO2 and CH4 to acetic acid over the Au-exchanged ZSM-5 catalyst: a density functional theory study.  

PubMed

The direct conversion of methane and carbon dioxide to acetic acid is one of the most challenging research topics. Using the density functional theory (M06-L) the study reveals the catalytic activity of the Au(I)-ZSM-5 zeolite in this reaction. The Au(I)-ZSM-5 is represented by a 34T quantum cluster model. The activation of the C-H bond over the Au-ZSM-5 zeolite would readily take place via the homolytic ?-bond activation with an energy barrier of 10.5 kcal mol(-1), and subsequent proton transfer from the Au cation to the zeolitic oxygen, yielding the stable methyl-gold complex adsorbed on the zeolite Brønsted acid. The conversion of CO(2) on this bi-functional catalyst involves the Brønsted acid site playing a role in the protonation of CO(2) and the methyl-gold complex acting as a methylating agent. The activation energy of 52.9 kcal mol(-1) is predicted. PMID:22903398

Panjan, Wasinee; Sirijaraensre, Jakkapan; Warakulwit, Chompunuch; Pantu, Piboon; Limtrakul, Jumras

2012-12-28

276

Oxidative degradation of 2,4,6-trichlorophenol and pentachlorophenol in contaminated soil suspensions using a supramolecular catalyst of 5,10,15,20-tetrakis (p-hydroxyphenyl)porphine-iron(III) bound to humic acid via formaldehyde polycondensation.  

PubMed

A supramolecular catalyst consisting of 5,10,15,20-tetrakis(p-hydroxyphenyl)porphine-iron(III) (FeTPP(OH)(4)) bound to humic acid (HA) was synthesized via formaldehyde polycondensation. The catalytic system, which included the synthesized catalyst (resol) and an oxygen donor (KHSO(5)), was applied to the oxidative degradation of 2,4,6-trichlorophenol (TrCP) and pentachlorophenol (PCP) in contaminated soil suspensions. The optimal conditions (catalyst, KHSO(5) and substrate concentrations) were investigated. In both FeTPP(OH)(4) and resol catalytic systems, more than 95% of TrCP (100 microM) and PCP (25 microM) degraded at pH 4, [catalyst] 20 microM and [KHSO(5)] 1 mM. When initial concentrations of TrCP and PCP were increased to [TrCP](0) 200 micro M and [PCP](0) 50 micro M, the percent degradation of the CPs and the levels of dechlorination in the resol catalytic system were significantly greater than the values obtained using the FeTPP(OH)(4) system. These results show that the synthesized resol catalyst effectively enhances oxidative degradation of TrCP and PCP in contaminated soil suspensions. The resol catalysts adsorbed to contaminated soils were at levels that were significantly greater than those of FeTPP(OH)(4). Therefore, the enhanced degradation of CPs by resol catalysts can be attributed to the interactions between adsorbed CPs on the soil surface and the catalytic center of the resol catalysts. PMID:19847698

Fukushima, Masami; Shigematsu, Satoko; Nagao, Seiya

2009-09-01

277

Preparation of fibrous titania oxynitride - carbon catalyst and oxygen reduction reaction analysis in both acidic and alkaline media  

NASA Astrophysics Data System (ADS)

A fibrous catalyst of titania oxynitride and carbon is prepared and its catalytic behavior in the oxygen reduction reaction (ORR) are investigated in both HClO4 and KOH aqueous solutions. TiO2 particles are successfully deposited on activated carbon fibers by a liquid phase deposition technique using (NH4)2TiF6 and H3BO3. The catalyst obtained after subsequent ammonia nitridation at 1273 K had a fibrous structure with TiOxNy and TiN components. Interestingly, the product demonstrates catalytic activity for the ORR in not only HClO4 but also KOH aqueous solution. The onset potential in HClO4 solution is assumed to be moderate, at 0.85 V; on the other hand, that in KOH solution is relatively high at 0.95 V. Furthermore, it is considered from the Tafel plot analysis of the KOH solution result that the ORR mechanism follows a peroxide intermediate pathway and the rate-determining step would be a one-electron-transfer reaction to oxygen molecules adsorbed on the active site.

Kinumoto, Taro; Sou, Yoshinori; Ono, Kohei; Matsuoka, Miki; Arai, Yasuhiko; Tsumura, Tomoki; Toyoda, Masahiro

2015-01-01

278

Method of performing sugar dehydration and catalyst treatment  

DOEpatents

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

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

2010-06-01

279

Composite catalyst for hydrocarbon conversion reactions  

SciTech Connect

A catalyst composite is described comprising a perfluorinated-polymersulfonic acid and an ion-stabilizing agent selected from the group consisting of C/sub 2/-C/sub 6/ fluorinated carboxylic acids and alcohols.

Farocasiu, D.

1986-04-29

280

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

281

Synthesis and characterization of ternary Pt-Ni-M/C (M=Cu, Fe, Ce, Mo, W) nano-catalysts for low temperature fuel cells  

NASA Astrophysics Data System (ADS)

Ternary metal catalysts were synthesized by impregnation method. The mixture of metal solutions was reduced slowly under inert atmosphere and the reduced metals were deposited on the Vulcan Carbon(VC). Tungsten, molybdenum, cerium, iron and copper were added to specified amounts of platinum and nickel. Addition of nickel generally improves catalytic activity of platinum. The XRD of the catalysts was done and the crystallite size and other parameters were calculated. Crystallite sizes were in the range of 5 to 16 nm. Electrochemical surface areas of the catalysts were determined by cyclic voltammetry (CV) in acidic media and are compared. Electro oxidation of methanol on the catalysts was done and peak potential, peak current, mass activity of the catalysts were calculated and are compared. These parameters were determined in acidic and basic media. It was found that mass activity increased significantly in basic media. Rate constants for the electro oxidation of methanol were also calculated in acidic and basic media and are compared and discussed. Rate constants were generally higher in basic media. Ternary catalysts showed improved catalytic activity than the binary catalyst. Nano alloying improved the catalytic activity and stability of the ternary catalysts.

Ahmed, Riaz; Jamil, Rabia; Shahid Ansari, Muhammad

2014-06-01

282

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

283

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

284

Nucleobase-mediated general acid-base catalysis in the Varkud satellite ribozyme.  

PubMed

Existing evidence suggests that the Varkud satellite (VS) ribozyme accelerates the cleavage of a specific phosphodiester bond using general acid-base catalysis. The key functionalities are the nucleobases of adenine 756 in helix VI of the ribozyme, and guanine 638 in the substrate stem loop. This results in a bell-shaped dependence of reaction rate on pH, corresponding to groups with pK(a) = 5.2 and 8.4. However, it is not possible from those data to determine which nucleobase is the acid, and which the base. We have therefore made substrates in which the 5' oxygen of the scissile phosphate is replaced by sulfur. This labilizes the leaving group, removing the requirement for general acid catalysis. This substitution restores full activity to the highly impaired A756G ribozyme, consistent with general acid catalysis by A756 in the unmodified ribozyme. The pH dependence of the cleavage of the phosphorothiolate-modified substrates is consistent with general base catalysis by nucleobase at position 638. We conclude that cleavage of the substrate by the VS ribozyme is catalyzed by deprotonation of the 2'-O nucleophile by G638 and protonation of the 5'-O leaving group by A756. PMID:20547881

Wilson, Timothy J; Li, Nan-Sheng; Lu, Jun; Frederiksen, John K; Piccirilli, Joseph A; Lilley, David M J

2010-06-29

285

DNA-based hybrid catalysts for asymmetric organic synthesis.  

PubMed

Stereoselective hybrid systems based on metal-assisted catalysis with a chiral biomacromolecule form an attractive research area for the synthesis of enantiomerically pure compounds. Although various methods are available for this purpose, most rely on the use of enzymes, proteins, or RNA. The application of DNA-based hybrid catalysts for enantioselective synthesis emerged only a few years ago. DNA-based hybrid catalysts have been self-assembled from DNA and a metal complex with a specific ligand through supramolecular or covalent anchoring strategies and have demonstrated high stereoselectivity and rate enhancement in Lewis acid catalyzed reactions, such as Diels-Alder, Michael addition, and Friedel-Crafts reactions. For these reactions, cheap and commercially available salmon testes DNA has generally been used. In this Minireview, we summarize recent developments in the area of asymmetric catalysis with DNA-based hybrid catalysts. PMID:20455226

Park, Soyoung; Sugiyama, Hiroshi

2010-05-25

286

A new sol-gel synthesis of 45S5 bioactive glass using an organic acid as catalyst.  

PubMed

In this paper a new sol-gel approach was explored for the synthesis of the 45S5 bioactive glass. We demonstrate that citric acid can be used instead of the usual nitric acid to catalyze the sol-gel reactions. The substitution of nitric acid by citric acid allows to reduce strongly the concentration of the acid solution necessary to catalyze the hydrolysis of silicon and phosphorus alkoxides. Two sol-gel powders with chemical compositions very close to that of the 45S5 were obtained by using either a 2M nitric acid solution or either a 5mM citric acid solution. These powders were characterized and compared to the commercial Bioglass®. The surface properties of the two bioglass powders were assessed by scanning electron microscopy (SEM) and by Brunauer-Emmett-Teller method (BET). The Fourier transformed infrared spectroscopy (FTIR) and the X-ray diffraction (XRD) revealed a partial crystallization associated to the formation of crystalline phases on the two sol-gel powders. The in vitro bioactivity was then studied at the key times during the first hours of immersion into acellular Simulated Body Fluid (SBF). After 4h immersion into SBF we clearly demonstrate that the bioactivity level of the two sol-gel powders is similar and much higher than that of the commercial Bioglass®. This bioactivity improvement is associated to the increase of the porosity and the specific surface area of the powders synthesized by the sol-gel process. Moreover, the nitric acid is efficiently substituted by the citric acid to catalyze the sol-gel reactions without alteration of the bioactivity of the 45S5 bioactive glass. PMID:25492213

Faure, J; Drevet, R; Lemelle, A; Ben Jaber, N; Tara, A; El Btaouri, H; Benhayoune, H

2015-02-01

287

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

288

General method for calculation of hydrogen-ion concentration in multicomponent acid-base mixtures.  

PubMed

A generalized method for the rapid evaluation of complicated ionic equilibria in terms of the hydrogen-ion concentration was developed. The method was based on the derivation of a single general equation that could be used to evaluate any mixture. A tableau method also was developed which allowed calculation of the numerical solution to the general equation without computer analysis or graphical or intuitive approximations. Examples illustrating the utility of the method are presented. These examples include a mixture of barbital, citric acid, boric acid, monobasic sodium phosphate, and sodium hydroxide. Calculated hydrogen-ion concentrations showed good agreement with experimental values for simple and complex solutions. The major advantages of the method are its simplicity and the obtainment of numerical solutions without initial approximations in the calculations. However, activity corrections are not included in the calculations. PMID:7400932

Ventura, D A; Ando, H Y

1980-08-01

289

Bio-inspired amino acid oxidation by a non-heme iron catalyst modeling the action of 1-aminocyclopropane-1-carboxylic acid oxidase.  

PubMed

In this communication we describe the first example of a biomimetic mononuclear iron complex, [Fe(III)(Salen)Cl] (Salen = N,N'-bis(salicylidene)-ethylenediaminato), that highly selectively and efficiently catalyzes the oxidation of 1-aminocyclopropane-1-carboxylic acid (ACCH), ?-aminoisobutyric acid (AIBH), and alanine (ALAH) to ethylene or the corresponding carbonyl compounds, mimicking the action of the non-heme iron enzyme 1-aminocyclopropane-1-carboxylic acid oxidase (ACCO). PMID:20830340

Baráth, Gábor; Kaizer, József; Pap, József Sándor; Speier, Gábor; El Bakkali-Taheri, Nadia; Simaan, A Jalila

2010-10-21

290

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

E-print Network

ABSTRACT The influence of niobium on the physicochemical properties of the Mo-V-O system and on its that the most efficient formula was Mo0.73V0.18Nb0.9Oy. Acetic acid was formed at high pressure only. Analysis catalytic properties in the oxidation of ethane to ethylene and acetic acid is examined. Solids based on Mo

Paris-Sud XI, Université de

291

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

292

No catalyst addition and highly efficient dissociation of H2O for the reduction of CO2 to formic acid with Mn.  

PubMed

The "greenhouse effect" caused by the increasing atmospheric CO2 level is becoming extremely serious, and thus, the reduction of CO2 emissions has become an extensive, urgent, and long-term task. The dissociation of water for CO2 reduction with solar energy is regarded as one of the most promising methods for the sustainable development of the environment and energy. However, a high solar-to-fuel efficiency keeps a great challenge. In this work, the first observation of a highly effective, highly selective, and robust system of dissociating water for the reduction of carbon dioxide (CO2) into formic acid with metallic manganese (Mn) is reported. A considerably high formic acid yield of more than 75% on a carbon basis from NaHCO3 was achieved with 98% selectivity in the presence of simple commercially available Mn powder without the addition of any catalyst, and the proposed process is exothermic. Thus, this study may provide a promising method for the highly efficient dissociation of water for CO2 reduction by combining solar-driven thermochemistry with the reduction of MnO into Mn. PMID:24787746

Lyu, Lingyun; Zeng, Xu; Yun, Jun; Wei, Feng; Jin, Fangming

2014-05-20

293

Photo-oxidation catalysts  

SciTech Connect

Photo-oxidation catalysts and methods for cleaning a metal-based catalyst are disclosed. An exemplary catalyst system implementing a photo-oxidation catalyst may comprise a metal-based catalyst, and a photo-oxidation catalyst for cleaning the metal-based catalyst in the presence of light. The exposure to light enables the photo-oxidation catalyst to substantially oxidize absorbed contaminants and reduce accumulation of the contaminants on the metal-based catalyst. Applications are also disclosed.

Pitts, J. Roland (Lakewood, CO); Liu, Ping (Irvine, CA); Smith, R. Davis (Golden, CO)

2009-07-14

294

Catalytic activity in individual cracking catalyst particles imaged throughout different life stages by selective staining  

NASA Astrophysics Data System (ADS)

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.

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

2011-11-01

295

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

2011-11-01

296

Chemo-Enzymatic Synthesis of Each Enantiomer of Orthogonally-Protected 4,4-Difluoroglutamic Acid – A Candidate Monomer for Chiral Brønsted-Acid Peptide-Based Catalysts  

PubMed Central

We have accomplished an asymmetric synthesis of each enantiomer of 4,4-difluoroglutamic acid. This ?-amino acid has been of interest in medicinal chemistry circles. Key features of the synthesis include highly scalable procedures, a Reformatsky-based coupling reaction, and straightforward functional group manipulations to make the parent amino acid. Enantioenrichment derives from an enzymatic resolution of the synthetic material. Conversion of the optically enriched compounds to orthogonally protected forms allows selective formation of peptide bonds. 4,4- Difluoroglutamic acid, in a suitably protected form, is also shown to exhibit enhanced catalytic activity in both an oxidation reaction and a reduction reaction, in comparison to the analogous glutamic acid derivative. PMID:22039908

Li, Yang

2011-01-01

297

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. PMID:22958171

Kath-Schorr, Stephanie; Wilson, Timothy J.; Li, Nan-Sheng; Lu, Jun; Piccirilli, Joseph A.; Lilley, David M. J.

2012-01-01

298

General acid-base catalysis mediated by nucleobases in the hairpin ribozyme.  

PubMed

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 pK(a). 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 pK(a) 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. PMID:22958171

Kath-Schorr, Stephanie; Wilson, Timothy J; Li, Nan-Sheng; Lu, Jun; Piccirilli, Joseph A; Lilley, David M J

2012-10-10

299

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

2013-01-15

300

Efficient combination of promoter and catalyst for chromic acid oxidation of propan-2-ol to acetone in aqueous acid media at room temperature  

NASA Astrophysics Data System (ADS)

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.

Mukherjee, Kakali; Saha, Rumpa; Ghosh, Aniruddha; Ghosh, Sumanta K.; Saha, Bidyut

2013-01-01

301

Catalyst for selective conversion of synthesis gas and method of making the catalyst  

DOEpatents

A Fischer-Tropsch (F-T) catalyst, a method of making the catalyst and an F-T process utilizing the catalyst by which synthesis gas, particularly carbon-monoxide rich synthesis gas is selectively converted to higher hydrocarbons of relatively narrow carbon number range. In general, the selective and notably stable catalyst, consists of an inert carrier first treated with a Group IV B metal compound (such as zirconium or titanium), preferably an alkoxide compound, and subsequently treated with an organic compound of an F-T metal catalyst, such as cobalt, iron or ruthenium carbonyl. Reactions with air and water and calcination are specifically avoided in the catalyst preparation procedure.

Dyer, Paul N. (Allentown, PA); Pierantozzi, Ronald (Macungie, PA)

1986-01-01

302

Supported fischer-tropsch catalyst and method of making the catalyst  

DOEpatents

A Fischer-Tropsch catalyst and a method of making the catalyst for a Fischer-Tropsch process utilizing the catalyst by which synthesis gas, particularly carbon-monoxide rich synthesis gas, is selectively converted to higher hydrocarbons of relatively narrow carbon number range is disclosed. In general, the selective and notably stable catalyst, consist of an inert carrier first treated with a Group IV B metal compound (such as zirconium or titanium), preferably an alkoxide compound, and subsequently treated with an organic compound of a Fischer-Tropsch metal catalyst, such as cobalt, iron or ruthenium carbonyl. Reactions with air and water and calcination are specifically avoided in the catalyst preparation procedure.

Dyer, Paul N. (Allentown, PA); Pierantozzi, Ronald (Orefield, PA); Withers, Howard P. (Douglassville, PA)

1987-01-01

303

TiO2 and Al2O3 promoted Pt/C nanocomposites as low temperature fuel cell catalysts for electro oxidation of methanol in acidic media  

NASA Astrophysics Data System (ADS)

Carbon corrosion and platinum dissolution are the two major catalyst layer degradation problems in polymer electrolyte membrane fuel cells (PEMFC). Ceramic addition can reduce the corrosion of carbon and increase the stability of catalysts. Pt/TiO2, Pt/TiO2-C, Pt/Al2O3 and Pt/Al2O3-C catalysts were synthesized and characterized. Electrochemical surface area of Pt/TiO2-C and Pt/Al2O3-C nanocomposite catalysts was much higher than the Pt/TiO2 and Pt/Al2O3 catalysts. Peak current, specific activity and mass activity of the catalysts was also determined by cyclic voltammetry and were much higher for the carbon nanocomposites. Exchange current densities were determined from Tafel plots. Heterogeneous rates of reaction of electro oxidation of methanol were determined for all the catalysts and were substantially higher for titania catalysts as compared to alumina added catalysts. Mass activity of Pt/TiO2-C was much higher than mass activity of Pt/Al2O3-C. Stability studies showed that addition of ceramics have increased the catalytic activity and durability of the catalysts considerably.

Naeem, Rabia; Ahmed, Riaz; Shahid Ansari, Muhammad

2014-06-01

304

A General, Highly Enantioselective Method for the Synthesis of D and L r-Amino Acids and Allylic Amines  

E-print Network

A General, Highly Enantioselective Method for the Synthesis of D and L r-Amino Acids and Allylic of amino acids is a subject of intense interest in the field of asymmetric catalysis. Traditionally. In this paper, we report on a different approach to amino acids based on an expeditious route to enantiopure

Walsh, Patrick J.

305

Theoretical predictions of 31p NMR chemical shift threshold of trimethylphosphine oxide absorbed on solid acid catalysts.  

PubMed

The 31P NMR chemical shifts of adsorbed trimethylphosphine oxide (TMPO) and the configurations of the corresponding TMPOH+ complexes on Brønsted acid sites with varying acid strengths in modeled zeolites have been predicted theoretically by means of density functional theory (DFT) quantum chemical calculations. The configuration of each TMPOH+ complex was optimized at the PW91/DNP level based on an 8T cluster model, whereas the 31P chemical shifts were calculated with the gauge including atomic orbital (GIAO) approach at both the HF/TZVP and MP2/TZVP levels. A linear correlation between the 31P chemical shift of adsorbed TMPO and the proton affinity of the solid acids was observed, and a threshold for superacidity (86 ppm) was determined. This threshold for superacidity was also confirmed by comparative investigations on other superacid systems, such as carborane acid and heteropolyoxometalate H3PW12O40. In conjunction with the strong correlation between the MP2 and the HF 31P isotropic shifts, the 8T cluster model was extended to more sophisticated models (up to 72T) that are not readily tractable at the GIAO-MP2 level, and a 31P chemical shift of 86 ppm was determined for TMPO adsorbed on zeolite H-ZSM-5, which is in good agreement with the NMR experimental data. PMID:18358024

Zheng, Anmin; Zhang, Hailu; Lu, Xin; Liu, Shang-Bin; Deng, Feng

2008-04-17

306

Generation of ricinoleic acid from castor oil using the lipase from ground oat ( Avena sativa L.) seeds as a catalyst  

Microsoft Academic Search

Summary The lipase found in oat seeds acts upon castor oil in organic solvent, yielding approximately 90% ricinoleic acid. Initial velocity is a poor predictor of the time required for complete lipolysis except at low oil concentrations. Equations were developed to estimate kinetic parameters necessary to accurately predict the degree of lipolysis.

George J. Piazza; Harold M. Farrell

1991-01-01

307

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

Microsoft Academic Search

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

Ebrahim Paimozd; Ali Ghasemi; Abdolhamid Jafari; Hassan Sheikh

2008-01-01

308

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

PubMed

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

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

2014-11-21

309

Amino acid modified Ni catalyst exhibits reversible H2 oxidation/production over a broad pH range at elevated temperatures  

SciTech Connect

Hydrogenases interconvert H2 and protons at high rates and with high energy efficiencies, providing inspiration for the development of molecular catalysts. Studies designed to determine how the protein scaffold can influence a catalytically active site has led to the synthesis of amino acid derivatives, [Ni(PCy2NAmino acid2)2]2+ (CyAA), of [Ni(PR2NR'2)2]2+ complexes. It is shown that these CyAA derivatives can catalyze fully reversible H2 production/oxidation, a feature reminiscent of enzymes. The reversibility is achieved in acidic aqueous solutions, 0.25% H2/Ar, and elevated temperatures (tested up to 348 K) for the glycine (CyGly), arginine (CyArg), and arginine methyl ester (CyArgOMe) derivatives. As expected for a reversible process, the activity is dependent upon H2 and proton concentration. CyArg is significantly faster in both directions than the other two derivatives (~300 s-1 H2 production and 20 s-1 H2 oxidation; pH=1, 348 K). The significantly slower rates for CyArgOMe (35 s-1 production and 7 s-1 oxidation) compared to CyArg suggests an important role for the COOH group during catalysis. That CyArg is faster than CyGly (3 s-1 production and 4 s-1 oxidation under the same conditions) suggests that the additional structural features imparted by the guanidinium groups facilitate fast and reversible H2 addition/release. These observations demonstrate that appended, outer coordination sphere amino acids work in synergy with the active site and can play an equally important role for synthetic molecular electrocatalysts as the protein scaffold does for redox active enzymes. This work was funded by the Office of Science Early Career Research Program through the US DOE, BES (AD, WJS), and the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the US DOE, BES (DLD, JASR). PNNL is operated by Battelle for the US DOE.

Dutta, Arnab; DuBois, Daniel L.; Roberts, John A.; Shaw, Wendy J.

2014-11-18

310

Catalysts for a cleaner environment  

SciTech Connect

Pollution-abatement catalysts remain a challenging area for process development. That`s because the pollutants themselves often poison the catalysts, and the new catalytic processes are now required to capture pollutants from very dilute waste streams. A case in point in the US is how severely low-level emissions of halogenated hydrocarbons are regulated through Title III regulations on toxic compounds. While common oxidation catalysts may be quite effective at eliminating most VOC [volatile organic compound] emissions, the presence of halogenated hydrocarbons can adversely affect catalyst performance. Only recently have catalysts become available that will be effective at oxidizing the halogenated hydrocarbons. The items described below illustrate the variety and scope of recently introduced catalysts that have proved themselves by increasing yields and reducing emissions. The offerings include catalysts for: improving yield in the production of acrylic acid, ammonia, styrene, phthalic anhydride and alcohol; reducing the sulfur and aromatic content of fuels; curtailing byproduct production in fluid-catalytic cracking units; oxidizing emissions of chlorinated hydrocarbons; and reducing NOx in combustion gas using hydrogen or carbon monoxide.

NONE

1995-09-01

311

The electron is a catalyst  

NASA Astrophysics Data System (ADS)

The electron is an efficient catalyst for conducting various types of radical cascade reaction that proceed by way of radical and radical ion intermediates. But because electrons are omnipresent, catalysis by electrons often passes unnoticed. In this Review, a simple analogy between acid/base catalysis and redox catalysis is presented. Conceptually, the electron is a catalyst in much the same way that a proton is a catalyst. The 'electron is a catalyst' paradigm unifies mechanistically an assortment of synthetic transformations that otherwise have little or no apparent relationship. Diverse radical cascades, including unimolecular radical substitution reactions (SRN1-type chemistry), base-promoted homolytic aromatic substitutions (BHAS), radical Heck-type reactions, radical cross-dehydrogenative couplings (CDC), direct arene trifluoromethylations and radical alkoxycarbonylations, can all be viewed as electron-catalysed reactions.

Studer, Armido; Curran, Dennis P.

2014-09-01

312

Catalyst activator  

DOEpatents

A catalyst activator particularly adapted for use in the activation of metal complexes of metals of Group 3-10 for polymerization of ethylenically unsaturated polymerizable monomers, especially olefins, comprising two Group 13 metal or metalloid atoms and a ligand structure including at least one bridging group connecting ligands on the two Group 13 metal or metalloid atoms.

McAdon, Mark H. (Midland, MI); Nickias, Peter N. (Midland, MI); Marks, Tobin J. (Evanston, IL); Schwartz, David J. (Lake Jackson, TX)

2001-01-01

313

Recovery of PT\\/RH from car exhaust catalysts  

Microsoft Academic Search

In order to recover platinum, rhodium and other precious metals from catalysts employed in internal combustion engine exhaust systems, the used or unused catalysts, preferably in crushed, powdered or broken form, are reacted with an acidic medium having oxidizing properties to leach out the precious metals. The acidic medium may be an acid containing or oxidizing agent or an oxidizing

C. W. Bradford; S. G. Baldwin

1976-01-01

314

Process for Making a Noble Metal on Tin Oxide Catalyst  

NASA Technical Reports Server (NTRS)

To produce a noble metal-on-metal oxide catalyst on an inert, high-surface-area support material (that functions as a catalyst at approximately room temperature using chloride-free reagents), for use in a carbon dioxide laser, requires two steps: First, a commercially available, inert, high-surface-area support material (silica spheres) is coated with a thin layer of metal oxide, a monolayer equivalent. Very beneficial results have been obtained using nitric acid as an oxidizing agent because it leaves no residue. It is also helpful if the spheres are first deaerated by boiling in water to allow the entire surface to be coated. A metal, such as tin, is then dissolved in the oxidizing agent/support material mixture to yield, in the case of tin, metastannic acid. Although tin has proven especially beneficial for use in a closed-cycle CO2 laser, in general any metal with two valence states, such as most transition metals and antimony, may be used. The metastannic acid will be adsorbed onto the high-surface-area spheres, coating them. Any excess oxidizing agent is then evaporated, and the resulting metastannic acid-coated spheres are dried and calcined, whereby the metastannic acid becomes tin(IV) oxide. The second step is accomplished by preparing an aqueous mixture of the tin(IV) oxide-coated spheres, and a soluble, chloride-free salt of at least one catalyst metal. The catalyst metal may be selected from the group consisting of platinum, palladium, ruthenium, gold, and rhodium, or other platinum group metals. Extremely beneficial results have been obtained using chloride-free salts of platinum, palladium, or a combination thereof, such as tetraammineplatinum (II) hydroxide ([Pt(NH3)4] (OH)2), or tetraammine palladium nitrate ([Pd(NH3)4](NO3)2).

Davis, Patricia; Miller, Irvin; Upchurch, Billy

2010-01-01

315

Binary ferrihydrite catalysts  

DOEpatents

A method of preparing a catalyst precursor comprises dissolving an iron salt and a salt of an oxoanion forming agent, in water so that a solution of the iron salt and oxoanion forming agent salt has a ratio of oxoanion/Fe of between 0.0001:1 to 0.5:1. Next is increasing the pH of the solution to 10 by adding a strong base followed by collecting of precipitate having a binary ferrihydrite structure. A binary ferrihydrite catalyst precursor is also prepared by dissolving an iron salt in water. The solution is brought to a pH of substantially 10 to obtain ferrihydrite precipitate. The precipitate is then filtered and washed with distilled water and subsequently admixed with a hydroxy carboxylic acid solution. The admixture is mixed/agitated and the binary ferrihydrite precipitate is then filtered and recovered.

Huffman, Gerald P. (Lexington, KY); Zhao, Jianmin (Lexington, KY); Feng, Zhen (Lexington, KY)

1996-01-01

316

Binary ferrihydrite catalysts  

DOEpatents

A method of preparing a catalyst precursor comprises dissolving an iron salt and a salt of an oxoanion forming agent, in water so that a solution of the iron salt and oxoanion forming agent salt has a ratio of oxoanion/Fe of between 0.0001:1 to 0.5:1. Next is increasing the pH of the solution to 10 by adding a strong base followed by collecting of precipitate having a binary ferrihydrite structure. A binary ferrihydrite catalyst precursor is also prepared by dissolving an iron salt in water. The solution is brought to a pH of substantially 10 to obtain ferrihydrite precipitate. The precipitate is then filtered and washed with distilled water and subsequently admixed with a hydroxy carboxylic acid solution. The admixture is mixed/agitated and the binary ferrihydrite precipitate is then filtered and recovered. 3 figs.

Huffman, G.P.; Zhao, J.; Feng, Z.

1996-12-03

317

Bioleaching of nickel from equilibrium fluid catalytic cracking catalysts  

Microsoft Academic Search

Summary This study investigates the possibility of reusing metal-contaminated equilibrium fluid catalytic cracking (FCC) catalyst after bioleaching. Leaching with Aspergillus niger culture was found to be more effective in the mobilization of nickel from the catalyst particles compared to chemical leaching with citric acid. Bioleaching achieved 32% nickel removal whereas chemical leaching achieved only 21% nickel removal from catalyst particles.

Oguz Bayraktar

2005-01-01

318

Hydrogenation of cottonseed oil with nickel, palladium and platinum catalysts  

Technology Transfer Automated Retrieval System (TEKTRAN)

A number of commercial catalysts have been used to study hydrogenation of cottonseed oil, with the goal of minimizing trans fatty acid (TFA) content. Despite the different temperatures used, catalyst levels, and reaction times, the data from each catalyst type fall on the same curve when the TFA le...

319

Resin catalysts and method of preparation  

DOEpatents

Heat stabilized catalyst compositions are prepared from nuclear sulfonic acid, for example, macroporous crosslinked polyvinyl aromatic compounds containing sulfonic acid groups are neutralized with a metal of Al, Fe, Zn, Cu, Ni, ions or mixtures and alkali, alkaline earth metals or ammonium ions by contacting the resin containing the sulfonic acid with aqueous solutions of the metals salts and alkali, alkaline earth metal or ammonium salts. The catalysts have at least 50% of the sulfonic acid groups neutralized with metal ions and the balance of the sulfonic acid groups neutralized with alkali, alkaline earth ions or ammonium ions.

Smith, Jr., Lawrence A. (P.O. Box 34687, Houston, TX 77243)

1986-01-01

320

Supported phosphate and carbonate salts for heterogeneous catalysis of triglycerides to fatty acid methyl esters  

NASA Astrophysics Data System (ADS)

Fatty acid methyl esters made from vegetable oil, or biodiesel, have been identified as a substitute for diesel derived from crude oil. Biodiesel is currently made using a homogeneous base catalyst to perform the transesterification of triglycerides with methanol to generate fatty acid methyl esters (FAME). The use of a homogeneous catalyst necessitates additional purification of the product and byproducts before sale, and the catalyst is consumed and discarded. The development of a heterogeneous basic catalyst for the production of FAME is desirable. Tribasic phosphate salts and dibasic carbonate salts are active for the production of FAME but generally operate as homogeneous catalysts. Supporting these phosphate and carbonate salts on mesoporous MCM-41, microporous silica gel, and nonporous a-alumina proved successful to greater or lesser degrees depending on the identity of the support and pretreatment of the support. Although these salts were supported and were active for the production of FAME from canola oil, they proved to be operating as homogeneous catalysts due to leaching of the active species off the surface of the support. Further investigation of the active species present in the tribasic phosphate catalysts identified the active support as orthophosphate, and NMR studies revealed the phosphorus to be present as orthophosphate and diphosphate in varying proportions in each catalyst. Evaluation of the acid-washing support pretreatment process revealed that the exposure of the support to acid plays a large role in the development of activity on the surface of the catalyst, but manipulation of these parameters did not prevent leaching of the active site off the surface of the catalyst. Alternate methods of support pretreatment were no more effective in preventing leaching. Tribasic phosphate supported on silica gel is not effective as a heterogeneous catalyst for FAME production from triglycerides because of the lack of stability of the phosphate on the support. The support is not stable under the reaction conditions, and alternatives should be explored to develop a heterogeneous base catalyst for the production of FAME.

Britton, Stephanie Lynne

321

Lewis Acid Organocatalysts  

NASA Astrophysics Data System (ADS)

The term Lewis acid catalysts generally refers to metal salts like aluminium chloride, titanium chloride and zinc chloride. Their application in asymmetric catalysis can be achieved by the addition of enantiopure ligands to these salts. However, not only metal centers can function as Lewis acids. Compounds containing carbenium, silyl or phosphonium cations display Lewis acid catalytic activity. In addition, hypervalent compounds based on phosphorus and silicon, inherit Lewis acidity. Furthermore, ionic liquids, organic salts with a melting point below 100 °C, have revealed the ability to catalyze a range of reactions either in substoichiometric amount or, if used as the reaction medium, in stoichiometric or even larger quantities. The ionic liquids can often be efficiently recovered. The catalytic activity of the ionic liquid is explained by the Lewis acidic nature of their cations. This review covers the survey of known classes of metal-free Lewis acids and their application in catalysis.

Sereda, Oksana; Tabassum, Sobia; Wilhelm, René

322

Lewis acid catalyst free synthesis of benzimidazoles and of formamidines in 1,1,1,3,3,3-hexafluoro-2-propanol  

Microsoft Academic Search

A simple, inexpensive, environmentally friendly and efficient route for the synthesis of benzimidazole and formamidine derivatives by the reaction of O-phenylenediamines or amines with orthoesters using hexafluoroisopropanol as a solvent\\/catalyst is described.

Samad Khaksar; Akbar Heydari; Mahmood Tajbakhsh; Seyed Mohammad Vahdat

323

Cascading of fluid cracking catalysts  

Microsoft Academic Search

A process is described for conversion of hydrocarbon feedstocks by cascading a cracking catalyst containing zeolite in an acidic matrix from one hydrocarbon processing unit to another, wherein there are at least three different interconnected hydrocarbon processing units comprising a first unit having a regeneration zone and a riser zone, a second unit having having a regeneration zone and a

S. M. Kovach; C. B. Miller

1986-01-01

324

Biodiesel production using heterogenous catalyst  

Technology Transfer Automated Retrieval System (TEKTRAN)

The current transesterification of triacylglycerides (TAG) to produce biodiesel is based on the homogenous catalyst method using strong base such as hydroxides or methoxides. However, this method results in a number of problems: (1) acid pre-treatment is required of feedstocks high in free fatty ac...

325

PseAAC-General: fast building various modes of general form of Chou's pseudo-amino acid composition for large-scale protein datasets.  

PubMed

The general form pseudo-amino acid composition (PseAAC) has been widely used to represent protein sequences in predicting protein structural and functional attributes. We developed the program PseAAC-General to generate various different modes of Chou's general PseAAC, such as the gene ontology mode, the functional domain mode, and the sequential evolution mode. This program allows the users to define their own desired modes. In every mode, 544 physicochemical properties of the amino acids are available for choosing. The computing efficiency is at least 100 times that of existing programs, which makes it able to facilitate the extensive studies on proteins and peptides. The PseAAC-General is freely available via SourceForge. It runs on both Linux and Windows. PMID:24577312

Du, Pufeng; Gu, Shuwang; Jiao, Yasen

2014-01-01

326

Identification of a potential general acid/base in the reversible phosphoryl transfer reactions catalyzed by tyrosine recombinases: Flp H305.  

PubMed

Flp provides a unique opportunity to apply the tools of chemical biology to phosphoryl transfer reactions. Flp and other tyrosine recombinases catalyze site-specific DNA rearrangements via a phosphotyrosine intermediate. Unlike most related enzymes, Flp's nucleophilic tyrosine derives from a different protomer than the remainder of its active site. Because the tyrosine can be supplied exogenously, nonnatural synthetic analogs can be used. Here we examine the catalytic role of Flp's conserved H305. DNA cleavage was studied using a peptide containing either tyrosine (pKa congruent with 10) or 3-fluoro-tyrosine (pKa congruent with 8.4). Religation was studied using DNA substrates with 3'-phospho-cresol (pKa congruent with 10) or 3'-para-nitro-phenol (pKa congruent with 7.1). In both cases, the tyrosine analog with the lower pKa specifically restored the activity of an H305 mutant. These results provide experimental evidence that this conserved histidine functions as a general acid/base catalyst in tyrosine recombinases. PMID:17317566

Whiteson, Katrine L; Chen, Yu; Chopra, Neeraj; Raymond, Amy C; Rice, Phoebe A

2007-02-01

327

Catalyst regeneration process including metal contaminants removal  

DOEpatents

Spent catalysts removed from a catalytic hydrogenation process for hydrocarbon feedstocks, and containing undesired metals contaminants deposits, are regenerated. Following solvent washing to remove process oils, the catalyst is treated either with chemicals which form sulfate or oxysulfate compounds with the metals contaminants, or with acids which remove the metal contaminants, such as 5-50 W % sulfuric acid in aqueous solution and 0-10 W % ammonium ion solutions to substantially remove the metals deposits. The acid treating occurs within the temperature range of 60.degree.-250.degree. F. for 5-120 minutes at substantially atmospheric pressure. Carbon deposits are removed from the treated catalyst by carbon burnoff at 800.degree.-900.degree. F. temperature, using 1-6 V % oxygen in an inert gas mixture, after which the regenerated catalyst can be effectively reused in the catalytic process.

Ganguli, Partha S. (Lawrenceville, NJ)

1984-01-01

328

Catalyst inventory control in an ebullated bed process  

SciTech Connect

This patent describes an improved method of maintaining a selected weight of catalyst in a reactor in a continuous process for treating a fluent hydrocarbon feedstock with a hydrogen-containing gas at elevated catalytic reaction temperatures and pressures in the presence of a bed of particulate solid catalyst. The process comprises introducing the hydrogen-containing gas and feedstock into the lower end of a generally vertical catalyst containing reaction vessel at sufficient velocity whereby the catalyst is placed in random motion within the fluent hydrocarbon. The catalyst bed is expanded to a volume greater than its static volume. The mixture of feedstock, gas and catalyst constitutes a turbulent zone from which zone aged catalyst is removed and fresh catalyst is added. The upper portion of the turbulent zone is defined by an interface with a substantially catalyst depleted zone from which zone hydrocarbon is removed.

Chan, T.Y.; Strickland, J.C.

1990-02-20

329

Therapeutic effects of docosahexaenoic acid ethyl ester in patients with generalized peroxisomal disorders.  

PubMed

Generalized peroxisomal disorders are severe congenital diseases that involve the central nervous system, leading to severe psychomotor retardation, retinopathy, liver disease, and early death. In these disorders, peroxisomes are not normally formed and their enzymes are deficient. Characteristically, plasmalogen synthesis and beta-oxidation of very-long-chain fatty acids (VLCFAs) are affected. We found that patients with generalized peroxisomal disorders have a profound brain deficiency of docosahexaenoic acid (DHA; 22:6n-3) and low DHA concentrations in all tissues and the blood. Given the fundamental role of DHA in neuronal and retinal membranes, a DHA deficiency of this magnitude might be pathogenic. Thus, we studied the possible therapeutic effect of normalizing DHA concentrations in patients with peroxisomal disorders. We chose the DHA ethyl ester (DHA-EE) because of its high degree of purity at daily oral doses of 100-500 mg. This article summarizes the results of treatment of 13 patients with DHA-EE, with some follow-up evidence of clinical improvement. Supplementation with DHA-EE normalized blood DHA values within a few weeks. Plasmalogen concentrations increased in erythrocytes in most patients and after DHA concentrations were normalized, amounts of VLCFAs decreased in plasma. Liver enzymes returned almost to normal in most cases. From a clinical viewpoint, most patients showed improvement in vision, liver function, muscle tone, and social contact. In 3 patients, normalization of brain myelin was detected by magnetic resonance imaging. In 3 others, myelination improved. In a seventh patient, myelination is progressing at a normal rate. These results suggest a fundamental role of DHA in the pathogenesis of Zellweger syndrome. DHA therapy is thus strongly recommended, not only to alleviate symptoms in patients with life-threatening diseases, but also to clarify remaining questions regarding the role of DHA in health and disease. PMID:10618001

Martínez, M; Vázquez, E; García-Silva, M T; Manzanares, J; Bertran, J M; Castelló, F; Mougan, I

2000-01-01

330

Remarkable effect of bimetallic nanocluster catalysts for aerobic oxidation of alcohols: combining metals changes the activities and the reaction pathways to aldehydes/carboxylic acids or esters.  

PubMed

Selective oxidation of alcohols catalyzed by novel carbon-stabilized polymer-incarcerated bimetallic nanocluster catalysts using molecular oxygen has been developed. The reactivity and the selectivity were strongly dependent on the combination of metals and solvent systems; aldehydes and ketones were obtained by the gold/platinum catalyst in benzotrifluoride, and esters were formed by the gold/palladium catalyst in methanol. To the best of our knowledge, this is the first example that the reaction pathway has been changed dramatically in gold catalysis by combining with a second metal. The differences in the activity and the selectivity are considered to be derived from the difference in the structure of the bimetallic clusters. PMID:20931964

Kaizuka, Kosuke; Miyamura, Hiroyuki; Kobayashi, Sh?

2010-11-01

331

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

PubMed

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

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

2014-02-01

332

Resid FCC catalyst technology: Today and the future  

SciTech Connect

Fluid cracking catalyst can be designed with properties to resist the poisoning effects of contaminant metals like Ni and V. Catalyst supports can be designed so that they interact strongly with Ni and reduce its tendency to catalyze undesirable dehydrogenation reactions. This interaction can be verified by oxygen chemisorption analysis of laboratory steamed or equilibrium catalysts. Grace Davision catalysts based on this technology have gained wide commercial acceptance. Vanadium poisons cracking catalyst due to formation of vanadic acid in the commercial FCC regenerator, which attacks the zeolite. Basic compounds (e.g., alkaline earth oxides and lanthanides) can be used to trap vanadium and protect the zeolite. These traps can be incorporated into a cracking catalyst (integral catalyst approach) or formed into a separate particle (additive approach). This paper discusses the development of both technologies. New laboratory techniques that realistically assess catalyst metals tolerance are also described.

Rajagopalan, K.R.; Cheng, W.C.; Suarez, W.; Wear, C.C. (Grace Davison, Columbia, MD (United States))

1993-01-01

333

Mercury-free dissolution of aluminum-clad fuel in nitric acid  

Microsoft Academic Search

It is the purpose of this invention to provide a continuous optimum process for the dissolution of aluminum, without the use of a mercury catalyst. Ile invention generally stated is: a process for dissolution of aluminum comprising: preparing a mixture of nitric acid`and fluoboric acid in a makeup vessel or individual reagents in separate vessels; placing an aluminum element in

J. D. Christian; P. A. Anderson

1993-01-01

334

GOASVM: A Subcellular Location Predictor by Incorporating Term-Frequency Gene Ontology into the General Form of Chou's Pseudo Amino Acid Composition  

E-print Network

into the General Form of Chou's Pseudo Amino Acid Composition Shibiao Wana , Man-Wai Maka, , Sun-Yuan Kungb a frequencies and distant homologs to represent a protein in the general form of Chou's pseudo amino acid only uses the amino-acid sequences of query proteins as input. They can be further classified

Mak, Man-Wai

335

Fluid cracking catalyst demetallization  

Microsoft Academic Search

The author discusses how his company has successfully operated its fluid catalyst demetallization and reactivation plant with high and low metals catalysts since April 1988. The recycled demetallized catalyst has proven stable in commercial FCC operations and has resulted in a reduction in fresh catalyst use.

Elvin

1989-01-01

336

Activity of vanadium catalysts for sulfuric acid production, promoted with Na, K, Rb, Cs, and Mg compounds, at various pressures of sulfur oxides  

Microsoft Academic Search

The activities of vanadium catalysts promoted with Na, K, Rb, Cs, and Mg sulfates (ratio Me:V = 4) were studied in conditions of low (up to 1 kPa) and high (up to 70 kPa) partial pressures of sulfur oxides at 693 and 758 K. The authors report results of reaction kinetic studies.

S. V. Ivanenko; R. R. Dzhoraev

1995-01-01

337

Continuous-flow hydration–condensation reaction: Synthesis of ?,?-unsaturated ketones from alkynes and aldehydes by using a heterogeneous solid acid catalyst  

PubMed Central

Summary A simple, practical and efficient continuous-flow hydration–condensation protocol was developed for the synthesis of ?,?-unsaturated ketones starting from alkynes and aldehydes by employing a heterogeneous catalyst in a flow microwave. The procedure presents a straightforward and convenient access to valuable differently substituted chalcones and can be applied on multigram scale. PMID:22238547

Bootwicha, Teerawut; Baars, Hannah; Sugiono, Erli

2011-01-01

338

Brønsted Acidic Ionic Liquid: An Efficient and Reusable Catalyst for the Synthesis of 3,4?Dihydropyrimidin?2(1H)?ones  

Microsoft Academic Search

A novel ionic liquid, 3?carboxymethyl?1?methylimidazolium bisulfate (CMImHSO4), was synthesized and used as a recyclable catalyst for the Biginelli reaction under solvent?free conditions. High yields of various substituted 3,4?dihydropyrimidin?2(1H)?ones (or thiones) were obtained. The ionic liquid can be recovered and recycled easily without loss of activity.

Renwei Zheng; Xiaoxia Wang; Hui Xu; Jingxing Du

2006-01-01

339

Catalysts for conversion of syngas to liquid motor fuels  

DOEpatents

Synthesis gas comprising carbon monoxide and hydrogen is converted to C.sub.5.sup.+ hydrocarbons suitable for use as liquid motor fuels by contact with a dual catalyst composition capable of ensuring the production of only relatively minor amounts of heavy products boiling beyond the diesel oil range. The catalyst composition, having desirable stability during continuous production operation, employs a Fischer-Tropsch catalyst, together with a co-catalyst/support component. The latter component is a steam-stabilized zeolite Y catalyst of hydrophobic character, desirably in acid-extracted form.

Rabo, Jule A. (Armonk, NY); Coughlin, Peter K. (Yorktown Heights, NY)

1987-01-01

340

Long-Life Catalyst  

NASA Technical Reports Server (NTRS)

STC Catalysts, Inc. (SCi) manufactures a noble metal reducible oxide catalyst consisting primarily of platinum and tin dioxide deposited on a ceramic substrate. It is an ambient temperature oxidation catalyst that was developed primarily for Carbon Dioxide Lasers.The catalyst was developed by the NASA Langley Research Center for the Laser Atmospheric Wind Sounder Program (LAWS) which was intended to measure wind velocity on a global basis. There are a number of NASA owned patents covering various aspects of the catalyst.

1999-01-01

341

Circulating Levels of Fatty Acid-Binding Protein Family and Metabolic Phenotype in the General Population  

PubMed Central

Objective Fatty acid-binding proteins (FABPs) are a family of 14-15-kDa proteins, and some FABPs have been to be used as biomarkers of tissue injury by leak from cells. However, recent studies have shown that FABPs can be secreted from cells into circulation. Here we examined determinants and roles of circulating FABPs in a general population. Methods From the database of the Tanno-Sobetsu Study, a study with a population-based cohort design, data in 2011 for 296 subjects on no medication were retrieved, and FABP1?5 in their serum samples were assayed. Results Level of FABP4, but not the other isoforms, showed a gender difference, being higher in females than in males. Levels of all FABPs were negatively correlated with estimated glomerular filtration rate (eGFR), but a distinct pattern of correlation with other clinical parameters was observed for each FABP isoform; significant correlates were alanine aminotransferase (ALT), blood pressure (BP), and brain natriuretic peptide (BNP) for FABP1, none besides eGFR for FABP2, age, BP, and BNP for FABP3, age, waist circumference (WC), BP, BNP, lipid variables, high-sensitivity C-reactive protein (hsCRP), and HOMA-R for FABP4, and age, WC, BP, ALT, BNP, and HOMA-R for FABP5. FABP4 is the most strongly related to metabolic markers among FABPs. In a multivariate regression analysis, FABP4 level was an independent predictor of HOMA-R after adjustment of age, gender, WC, BP, HDL cholesterol, and hsCRP. Conclusions Each FABP isoform level showed a distinct pattern of correlation with clinical parameters, although levels of all FABPs were negatively determined by renal function. Circulating FABP4 appears to be a useful biomarker for detecting pre-clinical stage of metabolic syndrome, especially insulin resistance, in the general population. PMID:24278421

Watanabe, Yuki; Hoshina, Kyoko; Fuseya, Takahiro; Mita, Tomohiro; Okazaki, Yusuke; Koyama, Masayuki; Tanaka, Marenao; Akasaka, Hiroshi; Ohnishi, Hirofumi; Yoshida, Hideaki; Saitoh, Shigeyuki; Miura, Tetsuji

2013-01-01

342

Synthesis and Understanding of Novel Catalysts  

SciTech Connect

The research took advantage of our capabilities to perform in-situ and operando Raman spectroscopy on complex systems along with our developing expertise in the synthesis of uniform, supported metal oxide materials to investigate relationships between the catalytically active oxide composition, atomic structure, and support and the corresponding chemical and catalytic properties. The project was organized into two efforts: 1) Synthesis of novel catalyst materials by atomic layer deposition (ALD). 2) Spectroscopic and chemical investigations of coke formation and catalyst deactivation. ALD synthesis was combined with conventional physical characterization, Raman spectroscopy, and probe molecule chemisorption to study the effect of supported metal oxide composition and atomic structure on acid-base and catalytic properties. Operando Raman spectroscopy studies of olefin polymerization leading to coke formation and catalyst deactivation clarified the mechanism of coke formation by acid catalysts.

Stair, Peter C. [Northwestern University] [Northwestern University

2013-07-09

343

Multistage fcc catalyst stripping  

SciTech Connect

This patent describes a fluid catalytic cracking process for cracking hydrocarbons. It comprises: cofeeding active hot solid zeolite cracking catalyst and crackable hydrocarbon feed to a cracking zone; cracking the feed to hydrocarbon products while depositing coke on the catalyst to evolve spent catalyst; disengaging the spent catalyst from the hydrocarbon products; flowing the spent catalyst to a regeneration zone; passing an oxygen-containing gas upwardly through the regeneration zone at sufficient velocity to fluidize the catalyst contained within the regeneration zone; retaining the catalyst in the regeneration zone at elevated temperature for a time sufficient to effect exothermic oxidative regeneration of the catalyst by burning the coke deposited thereon, thereby heating and reactivating the catalyst; providing a catalyst stripping zone comprising three superimposed stages, the stages comprising an upper mixing stage, a central dehydrogenation/stripping stage, and a lower steam stripping stage; mixing spent catalyst with regenerated catalyst in the upper mixing stage of the catalyst stripping zone; retaining the mixture within the upper mixing stage at elevated temperature for a period of time sufficient to effect desorption of cracked products from the spent catalyst; flowing the catalyst mixture downwardly to the central dehydrogenation/stripping stage.

Sapre, A.V.

1991-10-22

344

Composite catalyst for hydrocarbon conversion reactions  

SciTech Connect

This patent describes a process for the alkylation or aromatic hydrocarbons by olefins which comprises contacting the aromatic and the olefin in the presence of a catalyst composite. The composite comprises a perfluorinated polymersulfonic acid and an ion stabilizing agent selected from the group consisting of C/sub 2/-C/sub 6/ fluorinated carboxylic acids and alcohols.

Farcasiu, D.

1987-06-16

345

Ascorbic acid participates in a general mechanism for concerted glucose transport inhibition and lactate transport stimulation  

Microsoft Academic Search

In this paper, we present a novel function for ascorbic acid. Ascorbic acid is an important water-soluble antioxidant and\\u000a cofactor in various enzyme systems. We have previously demonstrated that an increase in neuronal intracellular ascorbic acid\\u000a is able to inhibit glucose transport in cortical and hippocampal neurons. Because of the presence of sodium-dependent vitamin\\u000a C transporters, ascorbic acid is highly

Maite A. Castro; Constanza Angulo; Sebastián Brauchi; Francisco Nualart; Ilona I. Concha

2008-01-01

346

Acid deposition in Maryland: a report to the Governor and General Assembly (1986). Annual report  

SciTech Connect

The Power Plant Research Program coordinates Maryland's acid-deposition research and reports research results annually. The report evaluates several major topic areas including transport and chemistry of acid deposition, its potential impacts on the State's streams and fish, possible impacts on terrestrial resources such as crops and forests and on materials, the ability of energy-conservation programs to reduce emissions of acid-forming pollutants, and mitigation techniques for neutralizing acid waters.

Not Available

1987-01-01

347

The surface architecture of an FCC catalyst  

SciTech Connect

From the beginning, refiners realized that small changes in catalyst composition and structure could have important effects on a catalyst's performance. An increase of 1% in the efficiency of oil conversion to liquid fuel is estimated to result in a savings of more than 22 million barrels of oil each year. Catalyst manufacturers are continuously seeking new materials and characterization tools that can help them gain the technological advantage necessary to survive and prosper in a highly competitive energy market. Atomic force microscopy (AFM), as developed by Binnig and co-workers, promises to be another powerful tool for studying the topology of catalysts because it is capable of imaging surfaces with atomic resolution. In fact, cracking in fluid cracking catalysis (FCC) is believed to occur mainly on the catalyst's top 10--15 [mu]m; therefore AFM could be particularly useful in characterizing the architecture of the surface pore structure that is available to gas oil cracking. The cracking catalyst the authors used in this study (GRZ-1) was obtained from Davison. The catalyst contains an estimated 35% rare earth exchanged zeolite Y, 50% kaolin, and 15% binder. Examination of the topography of an FCC catalyst using AFM reveals the presence of a unique surface architecturing gas oil cracking can be attributed mainly to the strong Lewis-type acidity of the alumina pillars between its montmorillonite-like layers.

Occelli, M.L. (Georgia Inst. of Tech., Atlanta, GA (United States)); Gould, S.A.C. (Claremont Coll., CA (United States))

1994-05-01

348

Support effects studied on model supported catalysts  

SciTech Connect

Composition and structure of oxide support materials can change the catalytic behavior of metal and oxide catalysts. Model catalysts are being studied in which the active phase is deposited on flat oxide substrates, with emphasis on metals catalysis for automotive emissions control and acidity in supported oxides. Research is reported in the following areas: particle-size effects, support effects on ZnO and zirconia, support effects on ceria, supported oxides, and low energy ion scattering (no results in the latter).

Gorte, R.J.

1993-02-01

349

A general approach to quantification of hydroxycinnamic acid derivatives and flavones, flavonols, and their glycosides by UV spectrophotometry  

Technology Transfer Automated Retrieval System (TEKTRAN)

A general method was developed for the quantification of hydroxycinnamic acid derivatives and flavones, flavonols, and their glycosides based on the UV molar relative response factors (MRRF) of the standards. Each of these phenolic compounds contains a cinnamoyl structure and has a maximum absorban...

350

Versatile reactivity of Pd-catalysts: mechanistic features of the mono-N-protected amino acid ligand and cesium-halide base in Pd-catalyzed C-H bond functionalization.  

PubMed

The widely used C-H functionalization strategies and some complexities in the Pd-catalyzed chemical transformations were analyzed. It was emphasized that in the course of catalysis various Pd-intermediates (including nano-scale Pd-clusters) could act as active catalysts. However, both identification of these catalytically active species and determination of factors controlling the overall catalytic process require more comprehensive and multi-disciplinary approaches. Recent joint computational and experimental approaches were instrumental in: (1) demonstrating that the addition of Pd(OAc)2 as a catalyst precursor to RSeH and RSH reagents forms the [Pd(SeR)2]n and [Pd(SR)2]n clusters, respectively, which show an unprecedented ability for selective synthesis of Markovnikov-type products starting with a mixture of reagents RSH/RSeH and acetylenic hydrocarbons; (2) predicting a valid mechanism of the amino acid ligand-assisted Pd(II)-catalyzed C-H activation that is shown to proceed via the formation of the catalytically active Pd(II) intermediate with a bidentately coordinated dianionic amino acid ligand; (3) demonstrating that the amino acid ligand plays crucial roles in the ligand-assisted Pd(II)-catalyzed C-H activation by acting as: (a) a weakly coordinating ligand to stabilize the desirable Pd(II)-precatalyst, (b) a soft proton donor and a bidentately coordinated dianionic ligand in the catalytically active Pd(II) intermediate, and (c) a proton acceptor accelerating the C-H deprotonation via the CMD mechanism; and (4) revealing the roles of the CsF base (and "cesium effect") in the Pd(0)/PCy3-catalyzed intermolecular arylation of the terminal ?-C(sp(3))-H bond of aryl amide and predicting the unprecedented "Cs2-I-F cluster" assisted mechanism for this reaction. PMID:24626313

Musaev, Djamaladdin G; Figg, Travis M; Kaledin, Alexey L

2014-07-21

351

A 1.9 Å Crystal Structure of the HDV Ribozyme Precleavage Suggests both Lewis Acid and General Acid Mechanisms Contribute to Phosphodiester Cleavage  

Microsoft Academic Search

The hepatitis delta virus (HDV) ribozyme and HDV-like ribozymes are self-cleaving RNAs found throughout all kingdoms of life. These RNAs fold into a double-nested pseudoknot structure and cleave RNA, yielding 2,3-cyclic phosphate and 5-hydroxyl termini. The active site nucleotide C75 has a pK{sub a} shifted >2 pH units toward neutrality and has been implicated as a general acid\\/base in the

Jui-Hui Chen; Rieko Yajima; Durga M. Chadalavada; Elaine Chase; Philip C. Bevilacqua; Barbara L. Golden

2010-01-01

352

iNitro-Tyr: Prediction of Nitrotyrosine Sites in Proteins with General Pseudo Amino Acid Composition  

PubMed Central

Nitrotyrosine is one of the post-translational modifications (PTMs) in proteins that occurs when their tyrosine residue is nitrated. Compared with healthy people, a remarkably increased level of nitrotyrosine is detected in those suffering from rheumatoid arthritis, septic shock, and coeliac disease. Given an uncharacterized protein sequence that contains many tyrosine residues, which one of them can be nitrated and which one cannot? This is a challenging problem, not only directly related to in-depth understanding the PTM’s mechanism but also to the nitrotyrosine-based drug development. Particularly, with the avalanche of protein sequences generated in the postgenomic age, it is highly desired to develop a high throughput tool in this regard. Here, a new predictor called “iNitro-Tyr” was developed by incorporating the position-specific dipeptide propensity into the general pseudo amino acid composition for discriminating the nitrotyrosine sites from non-nitrotyrosine sites in proteins. It was demonstrated via the rigorous jackknife tests that the new predictor not only can yield higher success rate but also is much more stable and less noisy. A web-server for iNitro-Tyr is accessible to the public at http://app.aporc.org/iNitro-Tyr/. For the convenience of most experimental scientists, we have further provided a protocol of step-by-step guide, by which users can easily get their desired results without the need to follow the complicated mathematics that were presented in this paper just for the integrity of its development process. It has not escaped our notice that the approach presented here can be also used to deal with the other PTM sites in proteins. PMID:25121969

Xu, Yan; Wen, Xin; Wen, Li-Shu; Wu, Ling-Yun; Deng, Nai-Yang; Chou, Kuo-Chen

2014-01-01

353

Effect of sodium impregnation on catalyst performance when hydrotreating a coal-derived liquid  

SciTech Connect

A commercial Ni-Mo/alumina catalyst was loaded with percentage quantities of sodium and tested for activity and activity maintenance while hydrotreating a coal-derived distillate under high severity conditions. The original catalyst exhibited a large high-temperature peak during the temperature-programmed desorption of tert-butylamine. This peak, which is an indicator of catalyst acidity, was reduced and ultimately eliminated by impregnating the catalyst with increasing amounts of sodium. At 5 wt % Na/sub 2/O, no acid peak remained. The sodium loadings had little effect on activity or activity maintenance for hydrogen uptake or specific gravity reduction as compared to the original catalyst. The hydrodenitrogenation activity was reduced, however. Activity maintenance for both the original catalyst and the sodium-treated catalyst was excellent, so it was not possible to observe an effect of sodium addition on activity decline. The sodium-loaded catalyst was coked to a lesser extent than the original catalyst.

Baker, J.R.; Mc Cormick, R.L.; Haynes, H.W. Jr.

1987-09-01

354

Reproductive Factors and Serum Uric Acid Levels in Females from the General Population: The KORA F4 Study  

PubMed Central

Objective Hyperuricemia is associated with an increased risk of metabolic and cardiovascular diseases. There are pronounced sex differences in the levels of uric acid. It is largely unknown whether or not reproductive parameters which induce hormonal changes are responsible for this. We examined if there are associations between reproductive parameters and uric acid levels in a female population-based sample. Methods In this cross-sectional analysis, data of 1530 women aged 32 to 81 years participating in the KORA F4 study, conducted between 2006 and 2008 in Southern Germany were used. Reproductive parameters were obtained by standardized interviews. Uric acid levels were tested by the uricase method. The whole study sample and stratified in pre- and postmenopausal women was analyzed. Results Menopausal status and earlier age at menarche were associated with higher serum uric acid levels (age-adjusted: p-values 0.003, <0.001 respectively; after multivariable adjustment, including BMI: p-values 0.002, 0.036). A history of oral contraceptive use showed an association with uric acid levels only after multivariable adjustment (p-value 0.009). Hot flushes showed an association with uric acid levels only after age-adjustment (p-value 0.038), but lost significance after adding other confounders. Other reproductive factors, including parity, current or ever use of hormone replacement therapy, current use of oral contraceptives, hysterectomy, bilateral oophorectomy, or depressive mood related to menopausal transition were not associated with uric acid levels. Conclusions Postmenopausal status, earlier age at menarche and a history of oral contraceptive use were independently associated with higher serum uric acid concentrations in women from the general population. Further studies, especially longitudinal population-based studies investigating the relationship of female reproductive parameters with uric acid levels are necessary to confirm our findings. PMID:22427861

Stöckl, Doris; Döring, Angela; Thorand, Barbara; Heier, Margit; Belcredi, Petra; Meisinger, Christa

2012-01-01

355

Process and catalyst for carbonylating olefins  

DOEpatents

Disclosed is an improved catalyst system and process for preparing aliphatic carbonyl compounds such as aliphatic carboxylic acids, alkyl esters of aliphatic carboxylic acids and anhydrides of aliphatic carboxylic acids by carbonylating olefins in the presence of a catalyst system comprising (1) a first component selected from at least one Group 6 metal, i.e., chromium, molybdenum, and/or tungsten and (2) a second component selected from at least one of certain halides and tertiary and quaternary compounds of a Group 15 element, i.e., nitrogen, phosphorus and/or arsenic, and (3) as a third component, a polar, aprotic solvent. The process employing the improved catalyst system is carried out under carbonylating conditions of pressure and temperature discussed herein. The process constitutes and improvement over known processes since it can be carried out at moderate carbonylation conditions without the necessity of using an expensive noble metal catalyst, volatile, toxic materials such as nickel tetracarbonyl, formic acid or a formate ester. Further, the addition of a polar, aprotic solvent to the catalyst system significantly increases, or accelerates, the rate at which the carbonylation takes place.

Zoeller, Joseph Robert (Kingsport, TN)

1998-06-02

356

Apparatus and method for regenerating coked fluid cracking catalyst  

Microsoft Academic Search

This patent describes a continuous counterflow two-stage method for regenrating hot coked FCC catalyst discharged from a FCC reactor, each of which stages produces a distinct flue gas. The FCC catalyst comprising an acidic cracking component and a SO\\/sub chi\\/-transfer agent. The method comprises as concurrent steps: passing the hot coked catalyst and first-stage fluidizing gas containing all of the

T. Y. Yan; G. J. Green

1989-01-01

357

The Definition of Generalized Helicoidal Parameters and of Axis Curvature for Irregular Nucleic Acids  

Microsoft Academic Search

An algorithm is presented which solves the problem of obtaining a rigorous helicoidal description of an irregular nucleic acid segment. Central to this approach is the definition of a function describing simultaneously the curvature of the nucleic acid segment in question and the corresponding stepwise variation of helicoidal parameters along the segment. Minimisation of this function leads to an optimal

Richard Lavery; Heinz Sklenar

1988-01-01

358

Lewis Base Catalysts 6: Carbene Catalysts  

PubMed Central

The use of N-heterocyclic carbenes as catalysts for organic transformations has received increased attention in the past 10 years. A discussion of catalyst development and nucleophilic characteristics precedes a description of recent advancements and new reactions using N-heterocyclic carbenes in catalysis. PMID:21494949

Moore, Jennifer L.

2013-01-01

359

SCR Catalyst Management  

Microsoft Academic Search

Selective Catalytic Reduction, SCR, is recognized worldwide as the most effective control technology of Nitrogen Oxides or NOx. SCR catalyst is applied to utility boilers and combustion turbines when substantial NOx reduction of 50% to 95% is required. SCR system capabilities and performance requirements, as well as SCR catalyst deactivation rates, are vital to forecasting when SCR catalyst layers should

Scott Rutherford; T. R. Stobert; George Wensell

2009-01-01

360

Catalyst deoiling process  

Microsoft Academic Search

A deoiling process is described comprising the steps of: removing a slurry of spent catalyst and oil from an ebullated bed reactor; transporting the slurry of spent catalyst and oil from the reactor to a vessel; cooling the slurry of spent catalyst and oil in the vessel to a temperature below the flash point of the oil; conveying the cooled

C. B. Olson; R. T. Plichta; D. W. Coyne

1987-01-01

361

Hydrocarbon conversion with hot and cooled regenerated catalyst in series  

SciTech Connect

This patent describes a heat balanced hydrocarbon conversion process wherein a hydrocarbon feed is converted to lower boiling products in a reactor by contacting the same at elevated temperatures with hot fluid cracking catalyst comprising a zeolite containing acid sites to form the lower boiling products. The resulting spent cracking catalyst containing coke from the reactor is separated from reaction products and stripped of volatile hydrocarbons in a stripping zone to provide stripped solid fluid cracking catalyst and the stripped catalyst is regenerated with an oxygen-containing gas in a regeneration zone to provide hot freshly regenerated fluid cracking catalyst which is returned to the reactor. The improvement comprises cooling a portion of the hot freshly regenerated fluid cracking catalyst to provide a cooled portion of regenerated fluid cracking catalyst, and a hot portion of regenerated fluid cracking catalyst, and contacting the cooled portion of regenerated fluid cracking catalyst with the hydrocarbon feed in the reactor downstream of contacting the hydrocarbon feed in the reactor with the hot portion of regenerated fluid cracking catalyst, thereby increasing the ratio of fluid cracking catalyst to the hydrocarbon feed.

Bartholic, D.B.; Barger, D.F.

1988-02-09

362

Generalized convulsion resulted in hyperammonemia during treatment with tranexamic acid for hemoptysis  

Microsoft Academic Search

Background  Tranexamic acid is commonly used to treat various kinds of bleeding disorders. It has been shown to cause severe convulsions\\u000a in animal experiments.\\u000a \\u000a \\u000a \\u000a Aims  We report a patient who experienced a single convulsive seizure that resulted in transient hyperammonemia during treatment\\u000a with tranexamic acid.\\u000a \\u000a \\u000a \\u000a Case report  A 68-year-old man was admitted and received tranexamic acid for persistent hemoptysis. After 5 days of admission,

C.-S. Wang; C.-J. Yang; S.-C. Chen; H.-C. Chen; M.-S. Huang

363

Engineering catalyst microenvironments for metal-catalyzed hydrogenation of biologically derived platform chemicals.  

PubMed

It is shown that microenvironments formed around catalytically active sites mitigate catalyst deactivation by biogenic impurities that are present during the production of biorenewable chemicals from biologically derived species. Palladium and ruthenium catalysts are inhibited by the presence of sulfur-containing amino acids; however, these supported metal catalysts are stabilized by overcoating with poly(vinyl alcohol) (PVA), which creates a microenvironment unfavorable for biogenic impurities. Moreover, deactivation of Pd catalysts by carbon deposition from the decomposition of highly reactive species is suppressed by the formation of bimetallic PdAu nanoparticles. Thus, a PVA-overcoated PdAu catalyst was an order of magnitude more stable than a simple Pd catalyst in the hydrogenation of triacetic acid lactone, which is the first step in the production of biobased sorbic acid. A PVA-overcoated Ru catalyst showed a similar improvement in stability during lactic acid hydrogenation to propylene glycol in the presence of methionine. PMID:25196504

Schwartz, Thomas J; Johnson, Robert L; Cardenas, Javier; Okerlund, Adam; Da Silva, Nancy A; Schmidt-Rohr, Klaus; Dumesic, James A

2014-11-17

364

The General Applicability of in Situ Transesterification for the Production of Fatty Acid Esters from a Variety of Feedstocks  

Microsoft Academic Search

We previously described a method for fatty acid methyl ester (FAME) production wherein acylglycerol transesterification was\\u000a achieved by reacting flaked full fat soybeans with alkaline methanol to create a product that met ASTM specifications for\\u000a biodiesel. In the present work we explore the general applicability of this approach, termed in situ transesterification,\\u000a to feedstocks other than soybeans. Materials investigated were

Michael J. Haas; Karen M. Scott; Thomas A. Foglia; William N. Marmer

2007-01-01

365

Hydrocarbon conversion with hot and cooled regenerated catalyst in series  

Microsoft Academic Search

This patent describes a heat balanced hydrocarbon conversion process wherein a hydrocarbon feed is converted to lower boiling products in a reactor by contacting the same at elevated temperatures with hot fluid cracking catalyst comprising a zeolite containing acid sites to form the lower boiling products. The resulting spent cracking catalyst containing coke from the reactor is separated from reaction

D. B. Bartholic; D. F. Barger

1988-01-01

366

Cerium-containing catalysts for converting ethanol into ethylene  

NASA Astrophysics Data System (ADS)

Ce/?-Al2O3 and CeLa/?-Al2O3 catalysts are studied via electron microscopy and temperature-programmed desorption of ammonia. Their activity in the dehydration of ethanol is investigated. Doping Ce/?-Al2O3 catalyst with lanthanum is shown to increase its dispersion and the number of active acid sites, thereby improving its activity.

Dosumov, K.; Ergazieva, G. E.; Churina, D. Kh.; Tel'baeva, M. M.

2014-10-01

367

Cobalt Fischer-Tropsch catalysts having improved selectivity  

DOEpatents

A cobalt Fischer-Tropsch catalyst having an improved steam treated, acid extracted LZ-210 support is taught. The new catalyst system demonstrates improved product selectivity at Fischer-Tropsch reaction conditions evidenced by lower methane production, higher C.sub.5.sup.+ yield and increased olefin production.

Miller, James G. (Pearl River, NY); Rabo, Jule A. (Armonk, NY)

1989-01-01

368

TRANSESTERIFICATION OF TRIACYLGLYCEROLS OVER CALCIUM OXIDE AS HETEROGENEOUS CATALYST  

Microsoft Academic Search

The use of a heterogeneous catalyst for transesterification of triacylglycerols (TAG) to methyl esters of fatty acids (FAME) by methanol enables its simple isolation from the reaction mixture and yields glycerol (G) of a good quality. Calcium oxide appears to be a promising heterogeneous catalyst. The paper presents the results of transesterification obtained from two samples containing CaO from two

Jozef Lengyel

369

Combination of best promoter and micellar catalyst for chromic acid oxidation of 1-butanol to 1-butanal in aqueous media at room temperature.  

PubMed

In aqueous acidic media, picolinic acid, 2,2'-bipyridine and 1,10-phenanthroline promoted Cr(VI) oxidation of 1-butanol produces 1-butanal. 1-butanal is separated from mixture by fractional distillation. The anionic surfactant (SDS) and neutral surfactant (TX-100) accelerate the process while the cationic surfactant (CPC) retards the reaction. Combination of bipy and SDS is the best choice for chromic acid oxidation of 1-butanol to 1-butanal in aqueous media. PMID:24468985

Saha, Rumpa; Ghosh, Aniruddha; Saha, Bidyut

2014-04-24

370

Catalyst by Design  

SciTech Connect

The development of new catalytic materials is still dominated by trial and error methods. Although it has been successful, the empirical development of catalytic materials is time consuming and expensive with no guarantee of success. In our laboratories, we are developing a comprehensive catalysts by design that involves state-of-the-art first principle density functional theory calculations, experimental design of catalyst sites, and sub- ngstr m resolution imaging with an aberration-corrected electron microscope to characterize the microstructure. In this chapter, we focus on supported platinum cluster catalyst systems which are one of the most important industrial catalysts and attempt to demonstrate the feasibility of the catalyst by design concept.

Narula, Chaitanya Kumar [ORNL] [ORNL; DeBusk, Melanie Moses [ORNL] [ORNL

2014-01-01

371

Novel multimetallic hydroisomerization catalysts  

SciTech Connect

Recent work in this laboratory with supported multimetallic catalysts has resulted in the discovery of a class of catalysts with unique selectivity and activity for the hydroisomerization of 1-butene, as well as the hydrogenation of butadiene. Specifically, it was found that catalysts particles are composed of three metallic components, one from the third row of the periodic table, one from the first row of rare earths, and a platinum group metal, have higher activity and are far more selective for 1-butene isomerization than any single metal catalyst, including commercial catalysts widely used for selective hydrogenation. 19 refs., 3 figs., 2 tabs.

Not Available

1994-04-01

372

Synthesis and structure of hydroxyl acids of general structure 7,7-alkenyl/alkynyl-5-hydroxymethyl-6-oxabicyclo[3.2.1]octane-1-carboxylic acid.  

PubMed

The open-ended hollow tubular structure formed by inclusion of water molecules in the packing of the hydroxyl acid 1 (R1 = CH2OH, R2 = ethyl groups) led to the synthesis and structural study of their unsaturated analogues. In this article we report on a general and practical large-scale synthesis of hydroxyl acids that possess alkenyl and alkynyl appendages. Substitution of the ethyl groups in 1 with unsaturated two-carbon appendages has a different effect on the molecular structure and on the hydrogen-bonding pattern. No variation has been induced by substitution of only one ethyl group with a vinyl one, although the substitution of both ethyl groups with vinyl or acetylene appendages has the greatest effect on the molecular structure and results in different hydrogen-bonding motifs. PMID:16438532

Pérez-Hernández, Natalia; Febles, Martín; Pérez, Cirilo; Pérez, Ricardo; Rodríguez, Matías L; Foces-Foces, Concepción; Martín, Julio D

2006-02-01

373

A general chelate-assisted co-assembly to metallic nanoparticles-incorporated ordered mesoporous carbon catalysts for Fischer-Tropsch synthesis.  

PubMed

The organization of different nano objects with tunable sizes, morphologies, and functions into integrated nanostructures is critical to the development of novel nanosystems that display high performances in sensing, catalysis, and so on. Herein, using acetylacetone as a chelating agent, phenolic resol as a carbon source, metal nitrates as metal sources, and amphiphilic copolymers as a template, we demonstrate a chelate-assisted multicomponent coassembly method to synthesize ordered mesoporous carbon with uniform metal-containing nanoparticles. The obtained nanocomposites have a 2-D hexagonally arranged pore structure, uniform pore size (~4.0 nm), high surface area (~500 m(2)/g), moderate pore volume (~0.30 cm(3)/g), uniform and highly dispersed Fe(2)O(3) nanoparticles, and constant Fe(2)O(3) contents around 10 wt %. By adjusting acetylacetone amount, the size of Fe(2)O(3) nanoparticles is readily tunable from 8.3 to 22.1 nm. More importantly, it is found that the metal-containing nanoparticles are partially embedded in the carbon framework with the remaining part exposed in the mesopore channels. This unique semiexposure structure not only provides an excellent confinement effect and exposed surface for catalysis but also helps to tightly trap the nanoparticles and prevent aggregating during catalysis. Fischer-Tropsch synthesis results show that as the size of iron nanoparticles decreases, the mesoporous Fe-carbon nanocomposites exhibit significantly improved catalytic performances with C(5+) selectivity up to 68%, much better than any reported promoter-free Fe-based catalysts due to the unique semiexposure morphology of metal-containing nanoparticles confined in the mesoporous carbon matrix. PMID:23020275

Sun, Zhenkun; Sun, Bo; Qiao, Minghua; Wei, Jing; Yue, Qin; Wang, Chun; Deng, Yonghui; Kaliaguine, Serge; Zhao, Dongyuan

2012-10-24

374

The Gap1 general amino acid permease acts as an amino acid sensor for activation of protein kinase A targets in the yeast Saccharomyces cerevisiae.  

PubMed

Addition of a nitrogen source to yeast (Saccharomyces cerevisiae) cells starved for nitrogen on a glucose-containing medium triggers activation of protein kinase A (PKA) targets through a pathway that requires for sustained activation both a fermentable carbon source and a complete growth medium (fermentable growth medium induced or FGM pathway). Trehalase is activated, trehalose and glycogen content as well as heat resistance drop rapidly, STRE-controlled genes are repressed, and ribosomal protein genes are induced. We show that the rapid effect of amino acids on these targets specifically requires the general amino acid permease Gap1. In the gap1Delta strain, transport of high concentrations of l-citrulline occurs at a high rate but without activation of trehalase. Metabolism of the amino acids is not required. Point mutants in Gap1 with reduced or deficient transport also showed reduced or deficient signalling. However, two mutations, S391A and S397A, were identified with a differential effect on transport and signalling for l-glutamate and l-citrulline. Specific truncations of the C-terminus of Gap1 (e.g. last 14 or 26 amino acids) did not reduce transport activity but caused the same phenotype as in strains with constitutively high PKA activity also during growth with ammonium as sole nitrogen source. The overactive PKA phenotype was abolished by mutations in the Tpk1 or Tpk2 catalytic subunits. We conclude that Gap1 acts as an amino acid sensor for rapid activation of the FGM signalling pathway which controls the PKA targets, that transport through Gap1 is connected to signalling and that specific truncations of the C-terminus result in permanently activating Gap1 alleles. PMID:14617151

Donaton, Monica C V; Holsbeeks, Inge; Lagatie, Ole; Van Zeebroeck, Griet; Crauwels, Marion; Winderickx, Joris; Thevelein, Johan M

2003-11-01

375

Catalyst patterning for nanowire devices  

NASA Technical Reports Server (NTRS)

Nanowire devices may be provided that are based on carbon nanotubes or single-crystal semiconductor nanowires. The nanowire devices may be formed on a substrate. Catalyst sites may be formed on the substrate. The catalyst sites may be formed using lithography, thin metal layers that form individual catalyst sites when heated, collapsible porous catalyst-filled microscopic spheres, microscopic spheres that serve as masks for catalyst deposition, electrochemical deposition techniques, and catalyst inks. Nanowires may be grown from the catalyst sites.

Li, Jun (Inventor); Cassell, Alan M. (Inventor); Han, Jie (Inventor)

2004-01-01

376

Heterogenization of Homogeneous Catalysts: the Effect of the Support  

SciTech Connect

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

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

1999-06-29

377

Textured catalysts and methods of making textured catalysts  

DOEpatents

A textured catalyst having a hydrothermally-stable support, a metal oxide and a catalyst component is described. Methods of conducting aqueous phase reactions that are catalyzed by a textured catalyst are also described. The invention also provides methods of making textured catalysts and methods of making chemical products using a textured catalyst.

Werpy, Todd (West Richland, WA); Frye, Jr., John G. (Richland, WA); Wang, Yong (Richland, WA); Zacher, Alan H. (Kennewick, WA)

2007-03-06

378

Development of Novel Supported Gold Catalysts: A Materials Perspective  

SciTech Connect

Since Haruta et al. discovered that small gold nanoparticles finely dispersed on certain metal oxide supports can exhibit surprisingly high activity in CO oxidation below room temperature, heterogeneous catalysis by supported gold nanoparticles has attracted tremendous attention. The majority of publications deal with the preparation and characterization of conventional gold catalysts (e.g., Au/TiO{sub 2}), the use of gold catalysts in various catalytic reactions, as well as elucidation of the nature of the active sites and reaction mechanisms. In this overview, we highlight the development of novel supported gold catalysts from a materials perspective. Examples, mostly from those reported by our group, are given concerning the development of simple gold catalysts with single metal-support interfaces and heterostructured gold catalysts with complicated interfacial structures. Catalysts in the first category include active Au/SiO{sub 2} and Au/metal phosphate catalysts, and those in the second category include catalysts prepared by pre-modification of supports before loading gold, by post-modification of supported gold catalysts, or by simultaneous dispersion of gold and an inorganic component onto a support. CO oxidation has generally been employed as a probe reaction to screen the activities of these catalysts. These novel gold catalysts not only provide possibilities for applied catalysis, but also furnish grounds for fundamental research.

Dai, Sheng [ORNL; Ma, Zhen [ORNL

2011-01-01

379

Enhancing P-xylene selectivity during m-xylene transformation using mildly pre-coked ZSM-5 catalyst  

E-print Network

Enhancing P-xylene selectivity during m-xylene transformation using mildly pre- coked ZSM-5 fresh and pre-coked H- ZSM-5 catalyst in a riser simulator over the temperature range of 350-500o C of the catalyst. While, the fresh catalyst generally gave higher m-xylene conversion, the pre-coked catalyst

Al-Khattaf, Sulaiman

380

ESTIMATION OF PHOSPHATE ESTER HYDROLYSIS RATE CONSTANTS. II. ACID AND GENERAL BASE CATALYZED HYDROLYSIS  

EPA Science Inventory

SPARC (SPARC Performs Automated Reasoning in Chemistry) chemical reactivity models were extended to calculate acid and neutral hydrolysis rate constants of phosphate esters in water. The rate is calculated from the energy difference between the initial and transition states of a ...

381

Generalized Data Correlations for Extinguishment Times and Acid Concentrations in Fire Tests with Fluorinated Suppression Agents  

Microsoft Academic Search

Correlations have been developed to predict the extinguishment time and peak hydrofluoric acid concentration for fires suppressed with heptatluoropropane (FM-200), trifluoromethane (FE-13), and perfluorobutane (CEA-410), as well as bromotnfluoromethane (Halon 1301). The extinguishment time correlations are ofthe form t, \\/ td = f, (Q*, C \\/ C,) where t, is the extinguishment time, td is the discharge time, Q' is

Robert Zalosh; Scott Heyworth

382

Use of aluminum phosphate as the dehydration catalyst in single step dimethyl ether process  

DOEpatents

The present invention pertains to a process for the coproduction of methanol and dimethyl ether (DME) directly from a synthesis gas in a single step (hereafter, the "single step DME process"). In this process, the synthesis gas comprising hydrogen and carbon oxides is contacted with a dual catalyst system comprising a physical mixture of a methanol synthesis catalyst and a methanol dehydration catalyst. The present invention is an improvement to this process for providing an active and stable catalyst system. The improvement comprises the use of an aluminum phosphate based catalyst as the methanol dehydration catalyst. Due to its moderate acidity, such a catalyst avoids the coke formation and catalyst interaction problems associated with the conventional dual catalyst systems taught for the single step DME process.

Peng, Xiang-Dong (Allentown, PA); Parris, Gene E. (Coopersburg, PA); Toseland, Bernard A. (Allentown, PA); Battavio, Paula J. (Allentown, PA)

1998-01-01

383

Method for regeneration and activity improvement of syngas conversion catalyst  

DOEpatents

A method is disclosed for the treatment of single particle iron-containing syngas (synthes.s gas) conversion catalysts comprising iron, a crystalline acidic aluminosilicate zeolite having a silica to alumina ratio of at least 12, a pore size greater than about 5 Angstrom units and a constraint index of about 1-12 and a matrix. The catalyst does not contain promoters and the treatment is applicable to either the regeneration of said spent single particle iron-containing catalyst or for the initial activation of fresh catalyst. The treatment involves air oxidation, hydrogen reduction, followed by a second air oxidation and contact of the iron-containing single particle catalyst with syngas prior to its use for the catalytic conversion of said syngas. The single particle iron-containing catalysts are prepared from a water insoluble organic iron compound.

Lucki, Stanley J. (Runnemede, NJ); Brennan, James A. (Cherry Hill, NJ)

1980-01-01

384

Treatment of spent catalyst from the nitrogenous fertilizer industry--a review of the available methods of regeneration, recovery and disposal.  

PubMed

Disposal of spent catalyst is a problem as it falls under the category of hazardous industrial waste. The recovery of metals from these catalysts is an important economic aspect as most of these catalysts are supported, usually on alumina/silica with varying percent of metal; metal concentration could vary from 2.5 to 20%. Metals like Ni, Mo, Co, Rh, Pt, Pd, etc., are widely used as a catalyst in chemical and petrochemical industries and fertilizer industries. They are generally supported on porous materials like alumina and silica through precipitation or impregnation processes. Many workers have adapted pyrometallurgy and Hydrometallurgy process for recovery of precious metals. Many workers have studied the recovery of nickel from a spent catalyst in an ammonia plant by leaching it in sulphuric acid solution (Hydrometallurgy). Ninety-nine percent of the nickel was recovered as nickel sulphate when the catalyst, having a particle size of 0.09 mm was dissolved in an 80% sulphuric acid solution for 50 min in at 70 degrees C. Many researcher have studied the extraction of metals from spent catalyst by roasting-extraction method (Pyrometallurgy). Chelating agents are the most effective extractants, which can be introduced in the soil washing fluid to enhance heavy metal extraction from contaminated soils. The advantages of chelating agents in soil cleanup include high efficiency of metal extraction, high thermodynamic stabilities of the metal complexes formed, good solubilities of the metal complexes, and low adsorption of the chelating agents on soils, But very few workers have attempted chelating agent to extract metals from spent catalyst. PMID:19286315

Singh, Bina

2009-08-15

385

Noncovalently supported heterogeneous chiral amine catalysts for asymmetric direct aldol and Michael addition reactions.  

PubMed

A new strategy for the immobilization of asymmetric organocatalysts by combining polystyrene (PS)/sulfonic acids and chiral amines in situ through acid-base interactions is presented. The PS/sulfonic acids play a dual role as catalyst anchors and modulators for activity and stereoselectivity. Different types of polymeric sulfonic acids were examined and 1% divinylbenzene (DVB) cross-linked PS/sulfonic acid 1 e with a medium loading of sulfonic acid moieties was found to be the optimal support. Furthermore, the noncovalency of this system allows combinatorial screening of optimal catalysts for the targeted reactions. In this regard, highly efficient and enantioselective heterogeneous catalysts were identified for the asymmetric direct aldol and Michael addition reactions. The catalysts could be easily recovered by filtration and reused for six cycles with similar stereoselectivity but slightly decreased activity. Significantly, the deactivated catalysts could be regenerated following an acidic washing/amine recharging procedure. PMID:18000996

Luo, Sanzhong; Li, Jiuyuan; Zhang, Long; Xu, Hui; Cheng, Jin-Pei

2008-01-01

386

A 1.9 Å Crystal Structure of the HDV Ribozyme Precleavage Suggests both Lewis Acid and General Acid Mechanisms Contribute to Phosphodiester Cleavage  

SciTech Connect

The hepatitis delta virus (HDV) ribozyme and HDV-like ribozymes are self-cleaving RNAs found throughout all kingdoms of life. These RNAs fold into a double-nested pseudoknot structure and cleave RNA, yielding 2{prime},3{prime}-cyclic phosphate and 5{prime}-hydroxyl termini. The active site nucleotide C75 has a pK{sub a} shifted >2 pH units toward neutrality and has been implicated as a general acid/base in the cleavage reaction. An active site Mg{sup 2+} ion that helps activate the 2{prime}-hydroxyl for nucleophilic attack has been characterized biochemically; however, this ion has not been visualized in any previous structures. To create a snapshot of the ribozyme in a state poised for catalysis, we have crystallized and determined the structure of the HDV ribozyme bound to an inhibitor RNA containing a deoxynucleotide at the cleavage site. This structure includes the wild-type C75 nucleotide and Mg{sup 2+} ions, both of which are required for maximal ribozyme activity. This structure suggests that the position of C75 does not change during the cleavage reaction. A partially hydrated Mg{sup 2+} ion is also found within the active site where it interacts with a newly resolved G {center_dot} U reverse wobble. Although the inhibitor exhibits crystallographic disorder, we modeled the ribozyme-substrate complex using the conformation of the inhibitor strand observed in the hammerhead ribozyme. This model suggests that the pro-RP oxygen of the scissile phosphate and the 2{prime}-hydroxyl nucleophile are inner-sphere ligands to the active site Mg{sup 2+} ion. Thus, the HDV ribozyme may use a combination of metal ion Lewis acid and nucleobase general acid strategies to effect RNA cleavage.

Chen, Jui-Hui; Yajima, Rieko; Chadalavada, Durga M.; Chase, Elaine; Bevilacqua, Philip C.; Golden, Barbara L. (Purdue); (Penn)

2010-11-01

387

The identification of the acid^base catalyst of K-arabinofuranosidase from Geobacillus stearothermophilus T-6, a family 51 glycoside hydrolase  

Microsoft Academic Search

The K K-L-arabinofuranosidase from Geobacillus stearo- thermophilus 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 L L-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

Dalia Shallom; Valery Belakhov; Dmitry Solomon; Sara Gilead-Gropper; Timor Baasov; Gil Shoham; Yuval Shoham

388

Methods of making textured catalysts  

DOEpatents

A textured catalyst having a hydrothermally-stable support, a metal oxide and a catalyst component is described. Methods of conducting aqueous phase reactions that are catalyzed by a textured catalyst are also described. The invention also provides methods of making textured catalysts and methods of making chemical products using a textured catalyst.

Werpy, Todd (West Richland, WA); Frye, Jr., John G. (Richland, WA); Wang, Yong (Richland, WA); Zacher, Alan H. (Kennewick, WA)

2010-08-17

389

Characteristics of Polyaniline Cobalt Supported Catalysts for Epoxidation Reactions  

PubMed Central

A study of polyaniline (PANI) doping with various cobalt compounds, that is, cobalt(II) chloride, cobalt(II) acetate, and cobalt(II) salen, is presented. The catalysts were prepared by depositing cobalt compounds onto the polymer surface. PANI powders containing cobalt ions were obtained by one- or two-step method suspending PANI in the following acetonitrile/acetic acid solution or acetonitrile and then acetic acid solution. Moreover different ratios of Co(II)?:?PANI were studied. Catalysts obtained with both methods and at all ratios were investigated using various techniques including AAS and XPS spectroscopy. The optimum conditions for preparation of PANI/Co catalysts were established. Catalytic activity of polyaniline cobalt(II) supported catalysts was tested in dec-1-ene epoxidation with molecular oxygen at room temperature. The relationship between the amount of cobalt species, measured with both AAS and XPS techniques, and the activity of PANI-Co catalysts has been established. PMID:24701183

Kowalski, Grzegorz; Pielichowski, Jan; Grzesik, Miros?aw

2014-01-01

390

Hydrous oxide ion-exchange compound catalysts  

DOEpatents

A catalytic material of improved activity which comprises a hydrous, alkali metal or alkaline earth metal or quaternary ammonium titanate, zirconate, niobate, or tantalate, in which the metal or ammonium cations have been exchange with a catalytically effective quantity of a catalyst metal, and which has been subsequently treated with a solution of a Bronsted acid.

Dosch, Robert G. (Albuquerque, NM); Stephens, Howard P. (Albuquerque, NM)

1990-01-01

391

Epoxidation of Methyl Oleate using Heterogeneous Catalyst  

Technology Transfer Automated Retrieval System (TEKTRAN)

In this work we studied the catalytic activity of commercial alumina, and laboratory synthesized alumina doped with Lewis acid metals, in the epoxidation of methyl oleate with aqueous hydrogen peroxide. It was observed that the reaction yields increased when the amount of catalyst, the quantity of ...

392

Catalyst deoiling process  

SciTech Connect

A deoiling process is described comprising the steps of: removing a slurry of spent catalyst and oil from an ebullated bed reactor; transporting the slurry of spent catalyst and oil from the reactor to a vessel; cooling the slurry of spent catalyst and oil in the vessel to a temperature below the flash point of the oil; conveying the cooled slurry at an upward angle of inclination in a screw conveyor in a spiral flow pattern while countercurrently draining oil from the slurry to substantially separate the oil from the spent catalyst; and discharging the spent catalyst from the screw conveyor into a bin after the oil has been substantially separated from the spent catalyst.

Olson, C.B.; Plichta, R.T.; Coyne, D.W.

1987-04-28

393

A new procedure for the destructuring of vegetable matter at atmospheric pressure by a catalyst\\/solvent system of formic acid\\/acetic acid.Applied to the pulping of triticale straw  

Microsoft Academic Search

The selective separation of cellulose, hemicelluloses and lignin of triticale straw is achieved, at atmospheric pressure, using a mixture of formic acid\\/acetic acid\\/water. The chemical and mechanical characteristics of the obtained pulp are good. The majority of the silica derivatives are retained in the pulp because of the acidic cooking conditions. The cooking agents are easily recyclable without combustion of

Hoang Quoc Lam; Yves Le Bigot; Michel Delmas; Gérard Avignon

2001-01-01

394

Structure of yeast regulatory gene LEU3 and evidence that LEU3 itself is under general amino acid control.  

PubMed Central

Determination of the nucleotide sequence of a DNA region from Saccharomyces cerevisiae previously shown to contain the LEU3 gene revealed one long open reading frame (ORF) whose 887 codons predict the existence of a protein with a molecular mass of 100,162 daltons. The codon bias index of 0.02 suggests that LEU3 encodes a low-abundance protein. The predicted amino acid sequence contains a stretch of 31 residues near the N-terminus that is rich in cysteines and basic amino acids and shows strong homology to similar regions in five other regulatory proteins of lower eukaryotes. Additional regions with a predominance of basic amino acids are present adjacent to the cysteine-rich region. A stretch of 20 residues, 19 of which are glu or asp, is found in the carboxy terminal quarter of the protein. The 5' flanking region of LEU3 contains a TATA box 111 bp upstream from the beginning of the long ORF and two transcription initiation elements (5'TCAA3') 58 and 48 bp upstream from the ORF. The 3' flanking region shows a tripartite potential termination-polyadenylation signal. The predicted 5' and 3' ends of the transcript are in very good agreement with the previously determined size of the LEU3 message. Analysis of a LEU3'-'lacZ translational fusion suggests that the LEU3 gene, whose product is involved in the specific regulation of the leucine and possibly the isoleucine-valine pathways, is itself under general amino acid control. Consistent with this observation is the finding that the 5' flanking region of LEU3 contains two perfect copies of the general control target sequence 5'TGACTC3'. PMID:3299266

Zhou, K; Brisco, P R; Hinkkanen, A E; Kohlhaw, G B

1987-01-01

395

Catalyst inventory control in an ebullated bed process  

SciTech Connect

A method of maintaining a selected weight of catalyst in a reactor in a continuous process for treating a fluid hydrocarbon feedstock with a hydrogen-containing gas at elevated catalytic reaction temperatures and pressures in the presence of a bed of particulate solid catalyst is described, said process comprising introducing the hydrogen-containing gas and feedstock into the lower end of a generally vertical catalyst containing reaction vessel at sufficient velocity whereby the catalyst is placed in random motion within the fluid hydrocarbon whereby the catalyst bed is expanded to a volume greater than its static volume, wherein the mixture of feedstock, gas and catalyst constitutes a turbulent zone from which zone aged catalyst is removed and fresh catalyst is added, the upper portion of which turbulent zone is defined by an interface with a substantially catalyst depleted zone from which zone hydrocracked hydrocarbon is removed, wherein the improvement comprises: 1. determining an interface height (H2) from a point adjacent the bottom of the bed (h0) to a point corresponding to the interface (h2), 2. determining an effective bed height (H1) from h0 to an intermediate fixed point (h1) in the bed adjacent the interface, and 3. determining a reactor height (H3) from a point adjacent the catalyst depleted zone top (h3) to h0, 4. measuring a first differential pressure (DP1) between h0 and h1, 5. measuring a second differential pressure (DP2) between the point adjacent the catalyst depleted zone top (h3) and h1, 6. determining a value for a catalyst inventory characterization factor (Wc) in accordance with the formula given in this patent, 7. removing aged catalyst, thereby changing the value of Wc, and 8. adding fresh catalyst in an amount to return to said value of Wc.

Nelson, G.V.; Nongbri, G.

1993-06-01

396

Liquefaction with microencapsulated catalysts  

DOEpatents

A method of dispersing a liquefaction catalyst within coal or other carbonaceous solids involves providing a suspension in oil of microcapsules containing the catalyst. An aqueous solution of a catalytic metal salt is emulsified in the water-immiscible oil and the resulting minute droplets microencapsulated in polymeric shells by interfacial polycondensation. The catalyst is subsequently blended and dispersed throughout the powdered carbonaceous material to be liquefied. At liquefaction temperatures the polymeric microcapsules are destroyed and the catalyst converted to minute crystallites in intimate contact with the carbonaceous material.

Weller, Sol W. (Williamsville, NY)

1985-01-01

397

Synthesis of 3- and 6-sulfonylindoles from ortho-alkynyl-N-sulfonylanilines by the use of Lewis acidic transition-metal catalysts.  

PubMed

Gold-catalyzed reactions of ortho-alkynyl-N-sulfonylanilines produced the corresponding 3-sulfonylindoles in good to high yields. For example, the reaction of N-mesyl-N-methyl-2-(1-pentynyl)aniline, N-mesyl-N-methyl-2-(phenylethynyl)-aniline, and 2-ethynyl-N-mesyl-N-methylaniline in the presence of 10 mol % of AuBr3 in toluene at 80 degrees C gave 3-mesyl-1-methyl-2-propylindole, 3-mesyl-1-methyl-2-phenylindole, and 3-mesyl-1-methylindole in 95, 92, and 71% yield, respectively. Furthermore, we found that the reactions of 2-alkynyl-6-methoxy-N-sulfonyl-anilines in the presence of indium catalyst (InBr3) afforded the corresponding 6-sulfonylindoles as the major product in good yields. For example, the reaction of 6-methoxy-N-methyl-2-(1-pentynyl)-N-tosylaniline in the presence of 5 mol % of InBr3 in toluene at 80 degrees C gave an 87:13 mixture of 7-methoxy-1-methyl-2-propyl-6-tosylindole and 7-methoxy-1-methyl-2-propyl-3-tosylindole in 95% yield. Most probably, the gold-catalyzed reactions of ortho-alkynyl-N-sulfonylanilines proceed through a [1,3] sulfonyl migration, whereas the indium-catalyzed cyclizations of 2-alkynyl-6-methoxy-N-sulfonylanilines, which produce 6-sulfonylindoles, proceed by an unprecedented [1,7] sulfonyl migration. PMID:18046686

Nakamura, Itaru; Yamagishi, Uichiro; Song, Dschun; Konta, Sayaka; Yamamoto, Yoshinori

2008-02-01

398

Integration of General Amino Acid Control and Target of Rapamycin (TOR) Regulatory Pathways in Nitrogen Assimilation in Yeast*  

PubMed Central

Two important nutrient-sensing and regulatory pathways, the general amino acid control (GAAC) and the target of rapamycin (TOR), participate in the control of yeast growth and metabolism during changes in nutrient availability. Amino acid starvation activates the GAAC through Gcn2p phosphorylation of translation factor eIF2 and preferential translation of GCN4, a transcription activator. TOR senses nitrogen availability and regulates transcription factors such as Gln3p. We used microarray analyses to address the integration of the GAAC and TOR pathways in directing the yeast transcriptome during amino acid starvation and rapamycin treatment. We found that GAAC is a major effector of the TOR pathway, with Gcn4p and Gln3p each inducing a similar number of genes during rapamycin treatment. Although Gcn4p activates a common core of 57 genes, the GAAC directs significant variations in the transcriptome during different stresses. In addition to inducing amino acid biosynthetic genes, Gcn4p in conjunction with Gln3p activates genes required for the assimilation of secondary nitrogen sources such as ?-aminobutyric acid (GABA). Gcn2p activation upon shifting to secondary nitrogen sources is suggested to occur by means of a dual mechanism. First, Gcn2p is induced by the release of TOR repression through a mechanism involving Sit4p protein phosphatase. Second, this eIF2 kinase is activated by select uncharged tRNAs, which were shown to accumulate during the shift to the GABA medium. This study highlights the mechanisms by which the GAAC and TOR pathways are integrated to recognize changing nitrogen availability and direct the transcriptome for optimal growth adaptation. PMID:20233714

Staschke, Kirk A.; Dey, Souvik; Zaborske, John M.; Palam, Lakshmi Reddy; McClintick, Jeanette N.; Pan, Tao; Edenberg, Howard J.; Wek, Ronald C.

2010-01-01

399

Integration of general amino acid control and target of rapamycin (TOR) regulatory pathways in nitrogen assimilation in yeast.  

PubMed

Two important nutrient-sensing and regulatory pathways, the general amino acid control (GAAC) and the target of rapamycin (TOR), participate in the control of yeast growth and metabolism during changes in nutrient availability. Amino acid starvation activates the GAAC through Gcn2p phosphorylation of translation factor eIF2 and preferential translation of GCN4, a transcription activator. TOR senses nitrogen availability and regulates transcription factors such as Gln3p. We used microarray analyses to address the integration of the GAAC and TOR pathways in directing the yeast transcriptome during amino acid starvation and rapamycin treatment. We found that GAAC is a major effector of the TOR pathway, with Gcn4p and Gln3p each inducing a similar number of genes during rapamycin treatment. Although Gcn4p activates a common core of 57 genes, the GAAC directs significant variations in the transcriptome during different stresses. In addition to inducing amino acid biosynthetic genes, Gcn4p in conjunction with Gln3p activates genes required for the assimilation of secondary nitrogen sources such as gamma-aminobutyric acid (GABA). Gcn2p activation upon shifting to secondary nitrogen sources is suggested to occur by means of a dual mechanism. First, Gcn2p is induced by the release of TOR repression through a mechanism involving Sit4p protein phosphatase. Second, this eIF2 kinase is activated by select uncharged tRNAs, which were shown to accumulate during the shift to the GABA medium. This study highlights the mechanisms by which the GAAC and TOR pathways are integrated to recognize changing nitrogen availability and direct the transcriptome for optimal growth adaptation. PMID:20233714

Staschke, Kirk A; Dey, Souvik; Zaborske, John M; Palam, Lakshmi Reddy; McClintick, Jeanette N; Pan, Tao; Edenberg, Howard J; Wek, Ronald C

2010-05-28

400

Palladium-Catalyzed ?-Arylation of Arylketones at Low Catalyst Loadings.  

PubMed

A general catalytic protocol for the ?-arylation of aryl ketones has been developed. It involves the use of a preformed, bench-stable Pd-N-heterocyclic carbene pre-catalyst bearing IHept as an ancillary ligand, and allows the coupling of various functionalized coupling partners at very low catalyst loading. Careful choice of the solvent/base system was crucial to obtain optimum catalyst performance. The pre-catalyst was also successfully tested in the synthesis of an industrially relevant compound. PMID:25414140

Marelli, Enrico; Corpet, Martin; Davies, Sian R; Nolan, Steven P

2014-12-22

401

Regeneration of Three-Way Automobile Catalysts using Biodegradable Metal Chelating Agent ? S, S-Ethylenediamine Disuccinic Acid (S, S-EDDS)  

EPA Science Inventory

Regeneration of the activity of three-way catalytic converters (TWCs) was tested for the first time using a biodegradable metal chelating agent (S, S. Ethylenediamine disuccinic acid (S, S-EDDS). The efficiency of this novel environmentally friendly solvent in removing various c...

402

A general method of protein purification for recombinant unstructured non-acidic proteins.  

PubMed

Typical late embryogenesis abundant (LEA) proteins accumulate in response to water deficit imposed by the environment or by plant developmental programs. Because of their physicochemical properties, they can be considered as hydrophilins and as a paradigm of intrinsically unstructured proteins (IUPs) in plants. To study their biophysical and biochemical characteristics large quantities of highly purified protein are required. In this work, we report a fast and simple purification method for non-acidic recombinant LEA proteins that does not need the addition of tags and that preserves their in vitro protective activity. The method is based on the enrichment of the protein of interest by boiling the bacterial protein extract, followed by a differential precipitation with trichloroacetic acid (TCA). Using this procedure we have obtained highly pure recombinant LEA proteins of groups 1, 3, and 4 and one recombinant bacterial hydrophilin. This protocol will facilitate the purification of this type of IUPs, and could be particularly useful in proteomic projects/analyses. PMID:21712091

Campos, Francisco; Guillén, Gabriel; Reyes, José L; Covarrubias, Alejandra A

2011-11-01

403

Method for producing iron-based catalysts  

DOEpatents

A method for preparing an acid catalyst having a long shelf-life is provided comprising doping crystalline iron oxides with lattice-compatible metals and heating the now-doped oxide with halogen compounds at elevated temperatures. The invention also provides for a catalyst comprising an iron oxide particle having a predetermined lattice structure, one or more metal dopants for said iron oxide, said dopants having an ionic radius compatible with said lattice structure; and a halogen bound with the iron and the metal dopants on the surface of the particle.

Farcasiu, Malvina (Pittsburgh, PA); Kaufman, Phillip B. (Library, PA); Diehl, J. Rodney (Pittsburgh, PA); Kathrein, Hendrik (McMurray, PA)

1999-01-01

404

Nanostructured catalyst supports  

DOEpatents

The present invention relates to SiC nanostructures, including SiC nanopowder, SiC nanowires, and composites of SiC nanopowder and nanowires, which can be used as catalyst supports in membrane electrode assemblies and in fuel cells. The present invention also relates to composite catalyst supports comprising nanopowder and one or more inorganic nanowires for a membrane electrode assembly.

Zhu, Yimin; Goldman, Jay L.; Qian, Baixin; Stefan, Ionel C.

2012-10-02

405

Fischer-Tropsch Catalysts  

NASA Technical Reports Server (NTRS)

Catalyst compositions and methods for F-T synthesis which exhibit high CO conversion with minor levels (preferably less than 35% and more preferably less than 5%) or no measurable carbon dioxide generation. F-T active catalysts are prepared by reduction of certain oxygen deficient mixed metal oxides.

White, James H. (Inventor); Taylor, Jesse W. (Inventor)

2008-01-01

406

General approach to reversing ketol-acid reductoisomerase cofactor dependence from NADPH to NADH  

PubMed Central

To date, efforts to switch the cofactor specificity of oxidoreductases from nicotinamide adenine dinucleotide phosphate (NADPH) to nicotinamide adenine dinucleotide (NADH) have been made on a case-by-case basis with varying degrees of success. Here we present a straightforward recipe for altering the cofactor specificity of a class of NADPH-dependent oxidoreductases, the ketol-acid reductoisomerases (KARIs). Combining previous results for an engineered NADH-dependent variant of Escherichia coli KARI with available KARI crystal structures and a comprehensive KARI-sequence alignment, we identified key cofactor specificity determinants and used this information to construct five KARIs with reversed cofactor preference. Additional directed evolution generated two enzymes having NADH-dependent catalytic efficiencies that are greater than the wild-type enzymes with NADPH. High-resolution structures of a wild-type/variant pair reveal the molecular basis of the cofactor switch. PMID:23776225

Brinkmann-Chen, Sabine; Flock, Tilman; Cahn, Jackson K. B.; Snow, Christopher D.; Brustad, Eric M.; McIntosh, John A.; Meinhold, Peter; Zhang, Liang; Arnold, Frances H.

2013-01-01

407

The use of imidazolium ionic liquid/copper complex as novel and green catalyst for chemiluminescent detection of folic acid by Mn-doped ZnS nanocrystals  

NASA Astrophysics Data System (ADS)

A novel chemiluminescence (CL) method using water-soluble Mn-doped ZnS quantum dots (QDs) as CL emitter is proposed for the chemiluminometric determination of folic acid in pharmaceutical formulation. Water-soluble Mn-doped ZnS QDs were synthesized by using L-cysteine as stabilizer in aqueous solutions. The nanoparticles were structurally and optically characterized by X-ray powder diffraction (XRD), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), UV-Vis absorption spectroscopy and photoluminescence (PL) emission spectroscopy. The CL of ZnS QDs induced by directly chemical oxidation and its ionic liquid-sensitized effect in aqueous solution were then investigated. It was found that oxidants, especially hydrogen peroxide, could directly oxidize ZnS QDs to produce weak CL emission in basic conditions. In the presence of 1,3-dipropylimidazolium bromide/copper a drastic light emission enhancement is observed, related to a strong interaction between Cu2+ and the imidazolium ring. Therefore, a new CL analysis system was developed for the determination of folic acid. Under the optimum conditions, there is a good linear relationship between the relative CL intensity and the concentration of folic acid in the range of 1 × 10-9-1 × 10-6 M of folic acid with a correlation coefficient (R2) of 0.9991. The limit of detection of this system was found to be 1 × 10-10 M. This method is not only simple, sensitive and low cost, but also reliable for practical applications.

Azizi, Seyed Naser; Shakeri, Parmis; Chaichi, Mohammad Javad; Bekhradnia, Ahmadreza; Taghavi, Mehdi; Ghaemy, Mousa

2014-03-01

408

The use of imidazolium ionic liquid/copper complex as novel and green catalyst for chemiluminescent detection of folic acid by Mn-doped ZnS nanocrystals.  

PubMed

A novel chemiluminescence (CL) method using water-soluble Mn-doped ZnS quantum dots (QDs) as CL emitter is proposed for the chemiluminometric determination of folic acid in pharmaceutical formulation. Water-soluble Mn-doped ZnS QDs were synthesized by using L-cysteine as stabilizer in aqueous solutions. The nanoparticles were structurally and optically characterized by X-ray powder diffraction (XRD), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), UV-Vis absorption spectroscopy and photoluminescence (PL) emission spectroscopy. The CL of ZnS QDs induced by directly chemical oxidation and its ionic liquid-sensitized effect in aqueous solution were then investigated. It was found that oxidants, especially hydrogen peroxide, could directly oxidize ZnS QDs to produce weak CL emission in basic conditions. In the presence of 1,3-dipropylimidazolium bromide/copper a drastic light emission enhancement is observed, related to a strong interaction between Cu(2+) and the imidazolium ring. Therefore, a new CL analysis system was developed for the determination of folic acid. Under the optimum conditions, there is a good linear relationship between the relative CL intensity and the concentration of folic acid in the range of 1×10(-9)-1×10(-)(6) M of folic acid with a correlation coefficient (R(2)) of 0.9991. The limit of detection of this system was found to be 1×10(-)(10) M. This method is not only simple, sensitive and low cost, but also reliable for practical applications. PMID:24322762

Azizi, Seyed Naser; Shakeri, Parmis; Chaichi, Mohammad Javad; Bekhradnia, Ahmadreza; Taghavi, Mehdi; Ghaemy, Mousa

2014-03-25

409

Spectroscopic monitoring of photocatalytic degradation of the insecticide acetamiprid and its degradation product 6-chloronicotinic acid on TiO2 catalyst  

Microsoft Academic Search

Two spectroscopic methods, H NMR and FTIR, were developed for the monitoring of the photocatalytic degradation of acetamiprid, a widely used pyridine-based neonicotinoid insecticide, in UV-irradiated aqueous suspensions of O2\\/TiO2. The H NMR method allowed also the identification of the intermediates such as 6-chloronicotinic and formic acids, as well as separate monitoring of the kinetics of degradation of acyclic and

Valéria Guzsvány; Ljiljana Raji?; Branislav Jovi?; Dejan Or?i?; János Csanádi; Sanja Lazi?; Biljana Abramovi?

2012-01-01

410

Hybrid porous tin(IV) phosphonate: an efficient catalyst for adipic acid synthesis and a very good adsorbent for CO2 uptake.  

PubMed

A new porous organic-inorganic hybrid tin phosphonate material has been synthesized hydrothermally, which shows a Brunauer-Emmett-Teller surface area of 723 m(2) g(-1) and it adsorbs 4.8 mmol g(-1) CO(2) at 273 K and 5 bar pressure. The material also shows remarkable catalytic activity in one-pot liquid phase oxidation of cyclohexanone to adipic acid under eco-friendly conditions. PMID:22627502

Dutta, Arghya; Pramanik, Malay; Patra, Astam K; Nandi, Mahasweta; Uyama, Hiroshi; Bhaumik, Asim

2012-07-01

411

Suitable combination of promoter and micellar catalyst for kilo fold rate acceleration on benzaldehyde to benzoic acid conversion in aqueous media at room temperature: a kinetic approach.  

PubMed

The kinetics of oxidation of benzaldehyde by chromic acid in aqueous and aqueous surfactant (sodium dodecyl sulfate, SDS, alkyl phenyl polyethylene glycol, Triton X-100 and N-cetylpyridinium chloride, CPC) media have been investigated in the presence of promoter at 303 K. The pseudo-first-order rate constants (kobs) were determined from a logarithmic plot of absorbance as a function time. The rate constants were found to increase with introduction of heteroaromatic nitrogen base promoters such as Picolinic acid (PA), 2,2'-bipyridine (bipy) and 1,10-phenanthroline (phen). The product benzoic acid has been characterized by conventional melting point experiment, NMR, HRMS and FTIR spectral analysis. The mechanism of both unpromoted and promoted reaction path has been proposed for the reaction. In presence of the anionic surfactant SDS, cationic surfactant CPC and neutral surfactant TX-100 the reaction can undergo simultaneously in both aqueous and micellar phase with an enhanced rate of oxidation in the micellar phase. Both SDS and TX-100 produce normal micellar effect whereas CPC produce reverse micellar effect in the presence of benzaldehyde. The observed net enhancement of rate effects has been explained by considering the hydrophobic and electrostatic interaction between the surfactants and reactants. SDS and bipy combination is the suitable one for benzaldehyde oxidation. PMID:23501718

Ghosh, Aniruddha; Saha, Rumpa; Ghosh, Sumanta K; Mukherjee, Kakali; Saha, Bidyut

2013-05-15

412

Suitable combination of promoter and micellar catalyst for kilo fold rate acceleration on benzaldehyde to benzoic acid conversion in aqueous media at room temperature: A kinetic approach  

NASA Astrophysics Data System (ADS)

The kinetics of oxidation of benzaldehyde by chromic acid in aqueous and aqueous surfactant (sodium dodecyl sulfate, SDS, alkyl phenyl polyethylene glycol, Triton X-100 and N-cetylpyridinium chloride, CPC) media have been investigated in the presence of promoter at 303 K. The pseudo-first-order rate constants (kobs) were determined from a logarithmic plot of absorbance as a function time. The rate constants were found to increase with introduction of heteroaromatic nitrogen base promoters such as Picolinic acid (PA), 2,2'-bipyridine (bipy) and 1,10-phenanthroline (phen). The product benzoic acid has been characterized by conventional melting point experiment, NMR, HRMS and FTIR spectral analysis. The mechanism of both unpromoted and promoted reaction path has been proposed for the reaction. In presence of the anionic surfactant SDS, cationic surfactant CPC and neutral surfactant TX-100 the reaction can undergo simultaneously in both aqueous and micellar phase with an enhanced rate of oxidation in the micellar phase. Both SDS and TX-100 produce normal micellar effect whereas CPC produce reverse micellar effect in the presence of benzaldehyde. The observed net enhancement of rate effects has been explained by considering the hydrophobic and electrostatic interaction between the surfactants and reactants. SDS and bipy combination is the suitable one for benzaldehyde oxidation.

Ghosh, Aniruddha; Saha, Rumpa; Ghosh, Sumanta K.; Mukherjee, Kakali; Saha, Bidyut

2013-05-01

413

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

Microsoft Academic Search

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

J. Weitkamp; Y. Traa

1999-01-01

414

Structures of bacterial polynucleotide kinase in a Michaelis complex with GTP•Mg2+ and 5?-OH oligonucleotide and a product complex with GDP•Mg2+ and 5?-PO4 oligonucleotide reveal a mechanism of general acid-base catalysis and the determinants of phosphoacceptor recognition  

PubMed Central

Clostridium thermocellum polynucleotide kinase (CthPnk), the 5? end-healing module of a bacterial RNA repair system, catalyzes reversible phosphoryl transfer from an NTP donor to a 5?-OH polynucleotide acceptor. Here we report the crystal structures of CthPnk-D38N in a Michaelis complex with GTP•Mg2+ and a 5?-OH oligonucleotide and a product complex with GDP•Mg2+ and a 5?-PO4 oligonucleotide. The O5? nucleophile is situated 3.0 Å from the GTP ? phosphorus in the Michaelis complex, where it is coordinated by Asn38 and is apical to the bridging ? phosphate oxygen of the GDP leaving group. In the product complex, the transferred phosphate has undergone stereochemical inversion and Asn38 coordinates the 5?-bridging phosphate oxygen of the oligonucleotide. The D38N enzyme is poised for catalysis, but cannot execute because it lacks Asp38—hereby implicated as the essential general base catalyst that abstracts a proton from the 5?-OH during the kinase reaction. Asp38 serves as a general acid catalyst during the ‘reverse kinase’ reaction by donating a proton to the O5? leaving group of the 5?-PO4 strand. The acceptor strand binding mode of CthPnk is distinct from that of bacteriophage T4 Pnk. PMID:24150947

Das, Ushati; Wang, Li Kai; Smith, Paul; Jacewicz, Agata; Shuman, Stewart

2014-01-01

415

Single-wall carbon nanotubes synthesized using organic additives to Co Mo catalysts supported on nanoporous MgO  

Microsoft Academic Search

Carbon nanotubes (CNTs) were synthesized by catalytic decomposition of 20% methane in hydrogen over Co-Mo\\/MgO catalysts at 1000 °C. The catalysts were prepared by a modified sol-gel method, using sorbitol, ethylenediamine tetraacetic acid (EDTA), tartaric acid and citric acid as organic additives. The specific surface area (SSA) of the catalysts changes with the organic additives in the order of sorbitol

A. M. Rashidi; M. M. Akbarnejad; A. A. Khodadadi; Y. Mortazavi; Ali Ahmadpourd

2007-01-01

416

Effect of aluminum oxide on the properties of Cu-Mo catalyst in the oxidative dehydrogenation of butene-1 to butadiene  

Microsoft Academic Search

Copper molybdate catalysts show catalytic activity for the oxidative dehydrogenation of butene-1, giving butadiene and carbon dioxide as main products, but not for its isomerization to butene-2. The isomerization reaction is catalysed at the centers of acidic nature; thus, aluminum oxide and aluminum molybdate catalysts having such acidic properties may be active catalysts for the conversion of butene-1 to butene-2.

P. N. Tiwari; T. G. Alkhazov; K. U. Adzamov; A. K. Khanmamedova

1989-01-01

417

Probing the Active Site of MIO-dependent Aminomutases, Key Catalysts in the Biosynthesis of amino Acids Incorporated in Secondary Metabolites  

SciTech Connect

The tyrosine aminomutase SgTAM produces (S)-{beta}-tyrosine from L-tyrosine in the biosynthesis of the enediyne antitumor antibiotic C-1027. This conversion is promoted by the methylideneimidazole-5-one (MIO) prosthetic group. MIO was first identified in the homologous family of ammonia lyases, which deaminate aromatic amino acids to form {alpha},{beta}-unsaturated carboxylates. Studies of substrate specificity have been described for lyases but there have been limited reports in altering the substrate specificity of aminomutases. Furthermore, it remains unclear as to what structural properties are responsible for catalyzing the presumed readdition of the amino group into the {alpha},{beta}-unsaturated intermediates to form {beta}-amino acids. Attempts to elucidate specificity and mechanistic determinants of SgTAM have also proved to be difficult as it is recalcitrant to perturbations to the active site via mutagenesis. An X-ray cocrystal structure of the SgTAM mutant of the catalytic base with L-tyrosine verified important substrate binding residues as well as the enzymatic base. Further mutagenesis revealed that removal of these crucial interactions renders the enzyme inactive. Proposed structural determinants for mutase activity probed via mutagenesis, time-point assays and X-ray crystallography revealed a complicated role for these residues in maintaining key quaternary structure properties that aid in catalysis.

Cooke, H.; Bruner, S

2010-01-01

418

Sc2(pydc)2 unit based 1D, 2D and 3D metal-organic frameworks as heterogeneous Lewis acid catalysts for cyanosilylation.  

PubMed

Three scandium metal-organic frameworks (Sc-MOFs), [Sc(pydc)(Hpydc)(H2O)]·H2O (), [Sc2(pydc)3(H2O)4]·5H2O () and [Sc(pydc)(H2O)(NO3)] () with similar Sc2(pydc)2 building unit were prepared by using 2,3-pyridinedicarboxylic acid (H2pydc) ligand under hydrothermal conditions. Compound exhibits a ladder-shaped chain with Sc2(pydc)2 units, which further construct a supramolecular characteristic with water molecules via hydrogen bond. Compound features a waved layer made up of pydc(2-) ligands and two types of crystallographically different Sc(iii) ions, among which Sc2 and pydc(2-) ligands constructed the Sc2(pydc)2 units. In compound , left and right helixes were alternately linked by the Sc2(pydc)2 units forming a hexagonal network with nbo-a topology. All the prepared compounds present effective heterogeneous Lewis acid catalytic functionality for the cyanosilylation of aldehyde. PMID:25489766

Cao, Yu; Zhu, Ziqian; Xu, Jianing; Wang, Li; Sun, Jiayin; Chen, Xiaobo; Fan, Yong

2014-12-23

419

Waste shells of mollusk and egg as biodiesel production catalysts.  

PubMed

The solid oxide catalysts derived from waste shells of egg, golden apple snail, and meretrix venus were employed to produce biodiesel from transesterification of palm olein oil. The shell materials were calcined in air at 800 degrees C with optimum time of 2-4h to transform calcium species in the shells into active CaO catalysts. All catalysts showed the high biodiesel production activity over 90% fatty acid methyl ester (FAME) in 2h, whilst the eggshell-derived catalyst showed comparable activity to the one derived from commercial CaCO(3). The catalytic activity was in accordance with the surface area of and the Ca content in the catalysts. PMID:20079632

Viriya-Empikul, N; Krasae, P; Puttasawat, B; Yoosuk, B; Chollacoop, N; Faungnawakij, K

2010-05-01

420

Oxidation of Benzaldehyde to Benzoic Acid  

Microsoft Academic Search

Benzaldehyde was oxidized to benzoic acid using Na2WO4·2H2O as a catalyst. Different factors, such as different acidic additives, the reaction time, the amount of catalyst, and hydrogen peroxide dosage, on the isolated yield of benzoic acid were investigated. The effects of surfactants on yield of benzoic acid were also discussed in the acid-free system. The results indicated that both acidic

Hongyan Yan; Chunsheng Liu; Genxiang Luo

2005-01-01

421

Study on methane conversion to synthesis gas over nano Pt/MgO catalysts III. Influence of the precursors on the physico-chemical properties of the catalysts  

NASA Astrophysics Data System (ADS)

Using different precursors, two series of nano Pt/MgO catalysts (Pt-II and Pt-IV, respectively) loaded with Pt in a wide range from 0.1 wt% to 2.2 wt% were prepared by using wet impregnation methods. The physico-chemical properties of catalysts were characterized by using BET, XRD, TPD-CO2, and other techniques. The results revealed that the precursor and content of Pt, especially the acid/base properties of the precursor solution, had a big influence on the structure, and surface properties of the catalysts. The loaded Pt is in metallic state in all the catalysts calcined at 1073 K. The Pt-II catalysts had larger surface areas and relatively narrow pore size distribution range. The MgO crystals in the calcined Pt-II-3 catalyst had more regular structure than that in the calcined Pt-IV-3 catalyst.

Yang, Min; Papp, Helmut

2009-09-01

422

Preliminary studies of platinum dissolution from a spent industrial catalyst  

Microsoft Academic Search

A spent PtNiO\\/Al2O3 industrial catalyst was examined with respect to Pt recovery. Aluminum chloride solutions, with low concentrations of nitric acid as an oxidant, were used instead of “aqua regia”. The effect of aluminum chloride and nitric acid concentrations on the yield of platinum dissolution was studied. The substitution of hydrochloric acid by aluminum chloride, with low nitric acid concentration,

T. N. Angelidis; E. Skouraki

1996-01-01

423

The selection reaction of homogeneous catalyst in soy-epoxide hydroxylation  

NASA Astrophysics Data System (ADS)

Hydroxylation reaction of soy-epoxide has resulted soy-polyol; a prepolymeric material for polyurethane. The conversion and selectivity of soy-epoxide butanol based to hydroxylation was found higher than soy-ethylene glycol (EG) based. These reactions were performed by sulfur acid which commonly known as homogeneous catalyst. Conversion and selectivity of homogeneous catalyst compared to bentonite; a heteregeneous catalyst was lower as in fact the mixtures were more viscous. The catalysis were significantly effected to cell morphology. Foams were conducted by heterogeneous catalyst resulted an irregular form of windows while homogeneous catalyst are more ordered.

Elvistia Firdaus, Flora

2014-04-01

424

Catalyst Activity Comparison of Alcohols over Zeolites  

SciTech Connect

Alcohol transformation to transportation fuel range hydrocarbon on HZSM-5 (SiO2 / Al2O3 = 30) catalyst was studied at 360oC and 300psig. Product distributions and catalyst life were compared using methanol, ethanol, 1-propanol or 1-butanol as a feed. The catalyst life for 1-propanol and 1-butanol was more than double compared to that for methanol and ethanol. For all the alcohols studied, the product distributions (classified to paraffin, olefin, napthene, aromatic and naphthalene compounds) varied with time on stream (TOS). At 24 hours TOS, liquid product from 1-propanol and 1-butanol transformation primarily contains higher olefin compounds. The alcohol transformation process to higher hydrocarbon involves a complex set of reaction pathways such as dehydration, oligomerization, dehydrocyclization, and hydrogenation. Compared to ethylene generated from methanol and ethanol, oligomerization of propylene and butylene has a lower activation energy and can readily take place on weaker acidic sites. On the other hand, dehydrocyclization of propylene and butylene to form the cyclic compounds requires the sits with stronger acid strength. Combination of the above mentioned reasons are the primary reasons for olefin rich product generated in the later stage of the time on stream and for the extended catalyst life time for 1 propanol and 1 butanol compared to methanol and ethanol conversion over HZSM-5.

Ramasamy, Karthikeyan K.; Wang, Yong

2013-01-01

425

Catalyst for microelectromechanical systems microreactors  

DOEpatents

A microreactor comprising a silicon wafer, a multiplicity of microchannels in the silicon wafer, and a catalyst coating the microchannels. In one embodiment the catalyst coating the microchannels comprises a nanostructured material. In another embodiment the catalyst coating the microchannels comprises an aerogel. In another embodiment the catalyst coating the microchannels comprises a solgel. In another embodiment the catalyst coating the microchannels comprises carbon nanotubes.

Morse, Jeffrey D. (Martinez, CA); Sopchak, David A. (Livermore, CA); Upadhye, Ravindra S. (Pleasanton, CA); Reynolds, John G. (San Ramon, CA); Satcher, Joseph H. (Patterson, CA); Gash, Alex E. (Brentwood, CA)

2011-11-15

426

Catalyst: Information on Computers in Psychology  

NSDL National Science Digital Library

Catalyst serves as a current awareness resource for information about computers in psychology. The site features full-text scholarly and general interest articles on recent psychological research related to information technology, covering such topics as cyberpsychology, online counseling, human-computer interaction, online behavior, Internet addiction, technology in education, and much more. The site also points users to other Web-based research publications, educational technology resources, and psychology-related software. Catalyst is produced by Victoria Point, an educational multimedia company founded by Richard Davis of Boston University.

427

Toward molecular catalysts by computer.  

PubMed

Conspectus Rational design of molecular catalysts requires a systematic approach to designing ligands with specific functionality and precisely tailored electronic and steric properties. It then becomes possible to devise computer protocols to design catalysts by computer. In this Account, we first review how thermodynamic properties such as redox potentials (E°), acidity constants (pKa), and hydride donor abilities (?GH(-)) form the basis for a framework for the systematic design of molecular catalysts for reactions that are critical for a secure energy future. We illustrate this for hydrogen evolution and oxidation, oxygen reduction, and CO conversion, and we give references to other instances where it has been successfully applied. The framework is amenable to quantum-chemical calculations and conducive to predictions by computer. We review how density functional theory allows the determination and prediction of these thermodynamic properties within an accuracy relevant to experimentalists (?0.06 eV for redox potentials, ?1 pKa unit for pKa values, and 1-2 kcal/mol for hydricities). Computation yielded correlations among thermodynamic properties as they reflect the electron population in the d shell of the metal center, thus substantiating empirical correlations used by experimentalists. These correlations point to the key role of redox potentials and other properties (pKa of the parent aminium for the proton-relay-based catalysts designed in our laboratory) that are easily accessible experimentally or computationally in reducing the parameter space for design. These properties suffice to fully determine free energies maps and profiles associated with catalytic cycles, i.e., the relative energies of intermediates. Their prediction puts us in a position to distinguish a priori between desirable and undesirable pathways and mechanisms. Efficient catalysts have flat free energy profiles that avoid high activation barriers due to low- and high-energy intermediates. The criterion of a flat energy profile can be mathematically resolved in a functional in the reduced parameter space that can be efficaciously calculated by means of the correlation expressions. Optimization of the functional permits the prediction by computer of design points for optimum catalysts. Specifically, the optimization yields the values of the thermodynamic properties for efficient (high rate and low overpotential) catalysts. We are on the verge of design of molecular electrocatalysts by computer. Future efforts must focus on identifying actual ligands that possess these properties. We believe that this can also be achieved through computation, using Taft-like relationships linking molecular composition and structure with electron-donating ability and steric effects. We note also that the approach adopted here of using free energy maps to decipher catalytic pathways and mechanisms does not account for kinetic barriers associated with elementary steps along the catalytic pathway, which may make thermodynamically accessible intermediates kinetically inaccessible. Such an extension of the approach will require further computations that, however, can take advantage of Polanyi-like linear free energy relationships linking activation barriers and reaction free energies. PMID:25574854

Raugei, Simone; DuBois, Daniel L; Rousseau, Roger; Chen, Shentan; Ho, Ming-Hsun; Bullock, R Morris; Dupuis, Michel

2015-02-17

428

Catalyst system comprising a first catalyst system tethered to a supported catalyst  

DOEpatents

The present invention provides new catalyst formats which comprise a supported catalyst tethered to a second and different catalyst by a suitable tethering ligand. A preferred system comprises a heterogeneous supported metal catalyst tethered to a homogeneous catalyst. This combination of homogeneous and heterogeneous catalysts has a sufficient lifetime and unusually high catalytic activity in arene hydrogenations, and potentially many other reactions as well, including, but not limited to hydroformylation, hydrosilication, olefin oxidation, isomerization, hydrocyanidation, olefin metathesis, olefin polymerization, carbonylation, enantioselective catalysis and photoduplication. These catalysts are easily separated from the products, and can be reused repeatedly, making these systems very economical. 2 figs.

Angelici, R.J.; Gao, H.

1998-08-04

429

Catalyst system comprising a first catalyst system tethered to a supported catalyst  

DOEpatents

The present invention provides new catalyst formats which comprise a supported catalyst tethered to a second and different catalyst by a suitable tethering ligand. A preferred system comprises a heterogeneous supported metal catalyst tethered to a homogeneous catalyst. This combination of homogeneous and heterogeneous catalysts has a sufficient lifetime and unusually high catalytic activity in arene hydrogenations, and potentially many other reactions as well, including, but not limited to hydroformylation, hydrosilation, olefin oxidation, isomerization, hydrocyanation, olefin metathesis, olefin polymerization, carbonylation, enantioselective catalysis and photoduplication. These catalysts are easily separated from the products, and can be reused repeatedly, making these systems very economical.

Angelici, Robert J. (Ames, IA); Gao, Hanrong (Ames, IA)

1998-08-04

430

Bimetallic Cobalt Based Catalysts  

Microsoft Academic Search

Highly dispersed, oxide- or zeolite-supported bimetallic catalysts are widely used in the catalytic industry, such as in catalytic reforming, nitrogen industry and gas-to-liquid technology. The paper highlights the nano-sized Co-based bimetallic system in terms of correlation between structure and reactivity\\/selectivity promoted by the second metal. Opposite to the bulk alloys nano-sized bimetallic catalysts are extremely sensitive to the structure, morphology,

László Guczi; Goran Boskovic; Ern? Kiss

2010-01-01

431

Crystalline titanate catalyst supports  

DOEpatents

A series of new crystalline titanates (CT) are shown to have considerable potential as catalyst supports. For Pd supported catalyst, the catalytic activity for pyrene hydrogenation was substantially different depending on the type of CT, and one was substantially more active than Pd on hydrous titanium oxide (HTO). For 1-hexene hydrogenation the activities of the new CTs were approximately the same as for the hydrous metal oxide supports.

Anthony, R.G.; Dosch, R.G.

1993-01-05

432

Crystalline titanate catalyst supports  

DOEpatents

A series of new crystalline titanates (CT) are shown to have considerable potential as catalyst supports. For Pd supported catalyst, the catalytic activity for pyrene hydrogenation was substantially different depending on the type of CT, and one was substantially more active than Pd on hydrous titanium oxide (HTO). For 1-hexene hydrogenation the activities of the new CTs were approximately the same as for the hydrous metal oxide supports.

Anthony, Rayford G. (Bryan, TX); Dosch, Robert G. (Albuquerque, NM)

1993-01-01

433

Plasmatron-catalyst system  

DOEpatents

A plasmatron-catalyst system. The system generates hydrogen-rich gas and comprises a plasmatron and at least one catalyst for receiving an output from the plasmatron to produce hydrogen-rich gas. In a preferred embodiment, the plasmatron receives as an input air, fuel and water/steam for use in the reforming process. The system increases the hydrogen yield and decreases the amount of carbon monoxide.

Bromberg, Leslie (Sharon, MA); Cohn, Daniel R. (Chestnut Hill, MA); Rabinovich, Alexander (Swampscott, MA); Alexeev, Nikolai (Moscow, RU)

2007-10-09

434

How Catalysts Work  

NSDL National Science Digital Library

This demonstration, presented by the National Nanotechnology Infrastructure Network, exposes students to the functionality of catalysts on a nanoscale. This lesson is "a great way to introduce or review reactants, catalysts, and adsorption, desorption, and diffusion. Use this demonstration after the Surface Area-to-Volume Ratio of Nanoparticles lab." A Teacher Preparation Guide, Student Guides, and Next Generation Manufacturing Standards for this lesson are included. 

435

Studies of Heterogeneous Catalyst Selectivity and Stability for Biorefining Applications  

NASA Astrophysics Data System (ADS)

The conversion of raw resources into value-added end products has long underlain the importance of catalysts in economic and scientific development. In particular, the development of selective and stable heterogeneous catalysts is a challenge that continues to grow in importance as environmental, sociological, and economic concerns have motivated an interest in sustainability and the use of renewable raw materials. Within this context, biomass has been identified as the only realistic source of renewable carbon for the foreseeable future. The development of processes to utilize biomass feedstocks will require breakthroughs in fundamental understanding and practical solutions to the challenges related to selectivity and stability of the catalysts employed. Selectivity is addressed on multiple fronts. First, the selectivity for C-O bond scission reactions of a bifunctional, bimetallic RhRe/C catalyst is investigated. Using multiple techniques, the origin of Bronsted acidity in the catalyst and the role of pretreatment on the activity, selectivity, and stability are explored. In addition, reaction kinetics experiments and kinetic modeling are utilized to understand the role of chemical functional group (i.e. carboxylic acid versus formate ester) in determining the decarbonylation versus decarboxylation selectivity over a Pd/C catalyst. Finally, kinetic studies over Pd/C and Cu/gamma-Al2O3 were performed so that that may be paired with density functional theory calculations and microkinetic modeling to elucidate the elementary reaction mechanism, identify the active site, and provide a basis for future rational catalyst design. Next, the issue of catalyst stability, important in the high-temperature, liquid-phase conditions of biomass processing, is examined, and a method for stabilizing the base-metal nanoparticles of a Cu/gamma-Al2O 3 catalyst using atomic layer deposition (ALD) is developed. This advancement may facilitate the development of biorefining by enabling the replacement of precious-metal catalysts (e.g. Pd, Pt, etc.) with less expensive, but previously unstable, base-metal catalysts. Using myriad techniques, the mechanisms of catalyst deactivation and stabilization of the nanoparticles by the ALD overcoat are elucidated. Finally, the use of ALD unlocks the potential for novel catalysts architectures, and the ability to physically and chemically tune the properties of the overcoat is examined with the goals of reducing catalyst deactivation and introducing bifunctional activity.

O'Neill, Brandon J.

436

Report of 1,000 Hour Catalyst Longevity Evaluation  

SciTech Connect

This report presents the results of a 1,000 hour, high-pressure, catalyst longevity test for the decomposition of concentrated sulfuric acid. The reaction is used for both the sulfur-iodine (S-I) cycle and hybrid sulfur cycle. By the time of the delivery date of April 17, 2009, for project milestone no. 2NIN07TC050114, the 1% Pt/TiO2 catalyst had been in the reaction environment for 658 hours. During the first 480 hours of testing, the catalyst activity provided stable, near-equilibrium yields of 46.8% SO2 and 22.8% O2. However, product yields declined at sample exposure times >480 hours. At 658 hours of operation, catalyst activity (based on oxygen yield) declined to 57% relative to the stable period of catalyst activity. Thus, as of April 17, this catalyst did not provide the desired stability level of <10% degradation per 1,000 hours. The experiment was terminated on April 27, after 792 hours, when a fitting failed and the catalyst was displaced from the reactor such that the sample could not be recovered. Oxygen conversion at the end of the experiment was 12.5% and declining, suggesting that at that point, catalyst activity had decreased to 54% of the initial level.

Daniel M. Ginosar

2009-06-01

437

Synthesis of carbon nanotubes and nanotube forests on copper catalyst  

NASA Astrophysics Data System (ADS)

The growth of carbon nanotubes on bulk copper is studied. We show for the first time, that super growth chemical vapor deposition method can be successfully applied for preparation of nanotubes on copper catalyst, and the presence of hydrogen is necessary. Next, different methods of copper surface activation are studied, to improve catalyst efficiency. Among them, applied for the first time for copper catalyst in nanotubes synthesis, sulfuric acid activation is the most promising. Among tested samples the surface modified for 10 min is the most active, causing the growth of vertically aligned carbon nanotube forests. Obtained results have potential importance in application of nanotubes and copper in electronic chips and nanodevices.

Kruszka, Bartosz; Terzyk, Artur P.; Wi?niewski, Marek; Gauden, Piotr A.; Szybowicz, Miros?aw

2014-09-01

438

Selective transfer semihydrogenation of alkynes with nanoporous gold catalysts.  

PubMed

A facile, highly chemo- and stereoselective transfer semihydrogenation of alkynes to Z-olefins has been achieved by use of unsupported nanoporous gold (AuNPore) as a heterogeneous catalyst together with formic acid as a hydrogen donor. A variety of terminal/internal and aromatic/aliphatic alkynes were reduced to the corresponding alkenes in high chemical yields with good functional-group tolerance. The catalyst is robust enough to be reused without leaching. PMID:25521623

Wagh, Yogesh S; Asao, Naoki

2015-01-16

439

Support effects studied on model supported catalysts. Progress report  

SciTech Connect

Composition and structure of oxide support materials can change the catalytic behavior of metal and oxide catalysts. Model catalysts are being studied in which the active phase is deposited on flat oxide substrates, with emphasis on metals catalysis for automotive emissions control and acidity in supported oxides. Research is reported in the following areas: particle-size effects, support effects on ZnO and zirconia, support effects on ceria, supported oxides, and low energy ion scattering (no results in the latter).

Gorte, R.J.

1993-02-01

440

Jumping-Catalyst Dynamics in Nanowire Growth  

NASA Astrophysics Data System (ADS)

Nanowire growth is generally considered a steady-state process, but oscillatory phenomena are known to often play a fundamental role. Here we identify a natural sequence of distinct growth modes, in two of which the catalyst droplet jumps periodically on and off a crystal facet. The oscillatory modes result from a mismatch between catalyst size and wire diameter; they enable growth of straight smooth-sided wires even when the droplet is too small to span the wire tip. Jumping-catalyst growth modes are seen both in computer simulations of vapor-liquid-solid growth, and in movies of Si nanowire growth obtained by in situ microscopy. Our simulations also provide new insight into nanowire kinking.

Schwarz, K. W.; Tersoff, J.; Kodambaka, S.; Ross, F. M.

2014-08-01

441

Directed Evolution of Stereoselective Hybrid Catalysts  

NASA Astrophysics Data System (ADS)

Whereas the directed evolution of stereoselective enzymes provides a useful tool in asymmetric catalysis, generality cannot be claimed because enzymes as catalysts are restricted to a limited set of reaction types. Therefore, a new concept has been proposed, namely directed evolution of hybrid catalysts in which proteins serve as hosts for anchoring ligand/transition metal entities. Accordingly, appropriate genetic mutagenesis methods are applied to the gene of a given protein host, providing after expression a library of mutant proteins. These are purified and a ligand/transition metal anchored site-specifically. Following en masse ee-screening, the best hit is identified, and the corresponding mutant gene is used as a template for another round of mutagenesis, expression, purification, bioconjugation, and screening. This allows for a Darwinian optimization of transition metal catalysts.

Reetz, Manfred T.

442

New catalysts for the indirect liquefaction of coal. Quarterly technical report, November 1, 1982January 31, 1983  

Microsoft Academic Search

Some ZSM-5 supported ruthenium (Ru\\/ZSM-5) catalysts have been prepared and characterized. The catalysts were prepared from Ruâ(CO)ââ and the acid form of ZSM-5 by the extraction procedure. Characterization of the catalysts has been achieved by using infrared spectroscopy, x-ray powder diffractometry, x-ray photoelectron spectroscopy, ion-scattering spectrometry and chemisorption. The chemical composition of the catalysts has been identified. It was determined

Melson

1983-01-01

443

Water-soluble poly(4-styrenesulfonic acid- co-maleic acid) stabilized ruthenium(0) and palladium(0) nanoclusters as highly active catalysts in hydrogen generation from the hydrolysis of ammonia–borane  

Microsoft Academic Search

Water-soluble poly(4-styrenesulfonic acid-co-maleic acid), PSSA-co-MA, stabilized ruthenium(0) and palladium(0) nanoclusters were for the first time prepared in situ from the reduction of ruthenium(III) chloride and potassium tetrachloropalladate(II), respectively, by ammonia–borane during its hydrolysis at room temperature. PSSA-co-MA stabilized ruthenium(0) and palladium(0) nanoclusters having average particle size of 1.9±0.5 and 3.5±1.6nm, respectively, were isolated from the reaction solution and characterized by

Önder Metin; ?ule ?ahin; Saim Özkar

2009-01-01

444

Characterization of three-way automotive catalysts  

SciTech Connect

The CRADA between Delphi Automotive Systems (Delphi; formerly General Motors - AC Delco, Systems) and Lockheed Martin Energy Research (LMER) on automotive catalysts was completed at the end of FY96, after a ten month, no-cost extension. The CRADA was aimed at improved performance and lifetime of noble metal based three-way-catalysts (TWC), which are the primary catalytic system for automotive emission control systems. While these TWC can meet the currently required emission standards, higher than optimum noble metal loadings are often required to meet lifetime requirements. In addition, more stringent emission standards will be imposed in the near future, demanding improved performance and service life from these catalysts. Understanding the changes of TWC conversion efficiency with ageing is a critical need in improving these catalysts. Initially in a fresh catalyst, the active material is often distributed on a very fine scale, approaching single atoms or small atomic clusters. As such, a wide range of analytical techniques have been employed to provide high spatial resolution characterization of the evolving state of the catalytic material.

Kenik, E.A.; More, K.L. [Oak Ridge National Lab., TN (United States); LaBarge, W. [Delphi Automotive Systems, Flint, MI (United States)] [and others

1997-04-01

445

Modified 8-ring zeolites as catalysts  

SciTech Connect

A catalyst composition is described for conversion of methanol and/or dimethylether and ammonia to dimethylamine, comprising at least one modified acidic zeolite selected from the group consisting of chabazite erionite, ZK-5, and rho, the zeolite having been modified by treatment with one or more compounds containing at least one element selected from the group consisting of silicon, aluminum, phosphorus, and boron, to deposit substantially on the external surfaces thereof at least 0.5 weight percent of the element.

Bergna, H.E.; Corbin, D.R.; Sonnichsen, G.C.

1988-06-21

446

Deactivation and poisoning of fuel cell catalysts  

SciTech Connect

The deactivation and poisoning phenomena reviewed are: the poisoning of anode (fuel electrode) catalyst by carbon monoxide and hydrogen sulfide; the deactivation of the cathode (air electrode) catalyst by sintering; and the deactivation of the cathode by corrosion of the support. The anode catalyst is Pt supported on a conductive, high area carbon black, usually at a loading of 10 w/o. This catalyst is tolerant to some level of carbon monoxide or hydrogen sulfide or both in combination, the level depending on temperature and pressure. Carbon monoxide poisoning has been studied extensively, including detailed adsorption studies at various temperatures and pressures. Predictive models have been developed that effectively predict anode tolerance to carbon monoxide. Much less is known about hydrogen sulfide poisoning. Typical tolerance levels are 2% CO, and 10 ppM H/sub 2/S. The cathode catalyst is typically Pt supported on a graphitic carbon black, usually a furnace black heat-treated to 2700/sup 0/C. The Pt loading is typically 10 w/o, and the dispersion (or percent exposed) as-prepared is typically 30%. The loss of dispersion in use depends on the operational parameters, most especially the cathode potential history, i.e. higher potentials cause more rapid decrease in dispersion. The mechanism of loss of dispersion is not well known. The graphitic carbon support corrodes at a finite rate that is also potential dependent. Support corrosion causes thickening of the eletrolyte film between the gas pores and the catalyst particles, which in turn causes increased diffusional resistance and performance loss. In addition, support corrosion may also cause loss of Pt into the separator. Support corrosion appears to be the life limiting factor for phosphoric acid fuel cells.

Ross, P.N. Jr.

1985-06-01

447

A high-performance direct transmethylation method for total fatty acids assessment in biological and foodstuff samples.  

PubMed

Isolation is the main bottleneck in the analysis of fatty acids in biological samples and foods. In the last few decades some methods described direct derivatization procedures bypassing these steps. They involve the utilization of methanolic HCL or BF3 as catalysts, but several evidences from previous works suggest these reagents are unstable, lead to the formation of artifacts and alter the distribution of specific compounds as hydroxy fatty acids or CLA. However, the main issue is that they are excellent esterification reagents but poor in transterification, being not suitable for the analysis of all lipid classes and leading to erroneous composition quantitations. The present research work is a comprehensive comparison of six general methylation protocols using base, acid or base/acid catalysts plus a proposed method in the analysis of total fatty acids in lipid standards mixtures, foodstuff and biological samples. The addition of aprotic solvents to the reaction mixture to avoid alterations was also tested. Results confirmed that procedures solely involving acid catalyst resulted in incomplete derivatizations and alteration of the fatty acid profile, partially corrected by addition of the aprotic solvent. The proposed method combining sodium methoxyde and sulfuric acid showed absence of alteration of the FAME profile and the best values for response factors (short chain fatty acids to PUFA), accuracy in the determination of total cholesterol and derivatization performance, thus showing a high reliability in the determination of the total fatty acid composition in biological samples and foods. PMID:25059195

Castro-Gómez, Pilar; Fontecha, Javier; Rodríguez-Alcalá, Luis M

2014-10-01

448

General characteristics of Pinus spp. Seed fatty acid compositions, and importance of ?5-olefinic acids in the taxonomy and phylogeny of the genus  

Microsoft Academic Search

The ?5-unsaturated polymethylene-interrupted fatty acid (?5-UPIFA) contents and profiles of gymnosperm seeds are useful chemometric\\u000a data for the taxonomy and phylogeny of that division, and these acids may also have some biomedical or nutritional applications.\\u000a We recapitulate here all data available on pine (Pinus; the largest genus in the family Pinaceae) seed fatty acid (SFA) compositions, including 28 unpublished compositions.

Robert L. Wolff; Frédérique Pédrono; Elodie Pasquier; Anne M. Marpeau

2000-01-01

449

Water removal by reactive stripping for a solid-acid catalyzed esterification in a monolithic reactor  

Microsoft Academic Search

Solid-acid catalysts are attractive replacements for processes using conventional homogeneous catalysts. In the esterification of an alcohol with a carboxylic acid, however, the side product water strongly inhibits the activity of a solid-acid catalyst. Since an esterification is an equilibrium limited reaction, full conversion is not possible unless one of the products is removed. A novel reactor type, utilizing a

T. A. Nijhuis; A. E. W. Beers; F. Kapteijn; J. A. Moulijn

2002-01-01

450

Supported organoiridium catalysts for alkane dehydrogenation  

DOEpatents

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

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

2013-09-03

451

Thermodynamic and kinetic aspects of surface acidity. Progress report, July 1, 1994--June 30, 1995  

SciTech Connect

Catalytic cracking of isobutane and 2-methyl-hexane over various USY-zeolite catalysts was studied. A kinetic model was developed for isobutane cracking over calcined and steamed Y-zeolite catalysts. Catalyst steaming leads to decreased Bronsted acidity. The studies of catalyst acid and basic properties were broadened to include alumina-supported metal oxides and a sulfated zirconia catalyst (isomerization of normal butane).

Dumesic, J.A.

1995-06-01

452

Low Temperature Oxidation Catalyst  

NASA Technical Reports Server (NTRS)

One day soon homeowners everywhere may be protected from deadly carbon monoxide fumes, thanks to a device invented at NASA Langley Research Center in Hampton, Va. It uses a new class of low-temperature oxidation catalysts to convert carbon monoxide to non-toxic carbon dioxide at room temperature. It can also remove formaldehyde from the air. The catalysts initially were developed for research involving carbon dioxide lasers. Industry already has shown an interest. Rochester Gas and Electric Co., of Rochester, N.Y., has an agreement with NASA Langley to develop a product for habitable spaces such as homes, cars and aircraft. The Mantic Corp., of Salt Lake City, Utah, plans to use them in breathing apparatus, such as firefighter masks. The catalysts also have applications as trace-gas detectors, and in cold-engine emission control. To work, the catalysts - tin oxide and platinum - are applied to a surface. Air passing over the surface reacts with the catalysts, transforming carbon monoxide and formaldehyde. The device requires no energy for operation, doesn't need to be plugged in, has no moving parts and lasts a long time.

1995-01-01

453

Reforming using erionite catalysts  

SciTech Connect

The advantage of reforming on erionite catalysts is a product with high octane numbers and low amounts of aromatics. This advantage seems to be slight at reaction pressures lower than 25 bar. But it is possible to compensate for the influence of pressure by varying the erionite content within the catalyst and the reaction temperature. When reforming on Pt/Al[sub 2]O[sub 3] catalysts, the following reactions take place: dehydrocyclization of paraffins to naphthenes, dehydrogenation of naphthenes to aromatics, isomerication of normal paraffins remains in the product, lowering its octane number. By using a Ni/H-erionite catalyst, the octane rating can be increased by 3 to 7 numbers through selective hydrocracking of n-alkanes in the reformate. Erionite catalysts favor shape-selective hydrocracking of normal paraffins and the formation of cyclopentane derivatives lowering the content of aromatics during reforming reactions. Reducing the reaction pressure decreases hydrocracking activity and cyclopentane formation. These results can be interpreted in terms of thermodynamic restrictions and deactivation.

Liers, J.; Meusinger, J.; Moesch, A. (Univ. of Leipzig (Germany)); Reschetilowski, W. (Karl Winnacker Inst. of DECHEMA, Frankfurt (Germany))

1993-08-01

454

Improved and selective platinum recovery from spent ?-alumina supported catalysts using pretreated anionic ion exchange resin  

Microsoft Academic Search

Improved and selective recovery of platinum from a spent dehydrogenation platinum ?-alumina supported catalyst using a strong basic ion exchange resin is reported. Platinum and other precious metal group (PMG) complexes are leached using concentrated hydrochloric acid along with about 0.20vol.% nitric acid as an oxidizing agent from de-coked and crushed spent catalyst. Effects of hydrochloric acid concentration, time, and

K. Shams; F. Goodarzi

2006-01-01

455

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

SciTech Connect

The objectives of our work are: (i) to create solid catalysts with active sites that can function in a cooperative manner to enhance reactivity and selectivity, and (ii) to prepare solid catalysts that can perform multiple reactions in a network that in some cases would not be possible in solution due to the incompatibilities of the various catalytic entities (for example an acid and a base). We carried out e