Sample records for general acid catalyst

  1. Arginine as a General Acid Catalyst in Serine Recombinase-mediated DNA Cleavage*

    PubMed Central

    Keenholtz, Ross A.; Mouw, Kent W.; Boocock, Martin R.; Li, Nan-Sheng; Piccirilli, Joseph A.; Rice, Phoebe A.

    2013-01-01

    Members of the serine family of site-specific DNA recombinases use an unusual constellation of amino acids to catalyze the formation and resolution of a covalent protein-DNA intermediate. A recent high resolution structure of the catalytic domain of Sin, a particularly well characterized family member, provided a detailed view of the catalytic site. To determine how the enzyme might protonate and stabilize the 3?O leaving group in the strand cleavage reaction, we examined how replacing this oxygen with a sulfur affected the cleavage rate by WT and mutant enzymes. To facilitate direct comparison of the cleavage rates, key experiments used suicide substrates that prevented religation after cleavage. The catalytic defect associated with mutation of one of six highly conserved arginine residues, Arg-69 in Sin, was partially rescued by a 3? phosphorothiolate substrate. We conclude that Arg-69 has an important role in stabilizing the 3?O leaving group and is the prime candidate for the general acid that protonates the 3?O, in good agreement with the position it occupies in the high resolution structure of the active site of Sin. PMID:23970547

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

    PubMed Central

    Basch, Corey H.; Song, Ye-Geun; Watson, Mary P.

    2014-01-01

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

  3. Formic acid fuel cells and catalysts

    DOEpatents

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

    2010-06-22

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

  4. Catalysts for direct formic acid fuel cells

    NASA Astrophysics Data System (ADS)

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

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

  5. Industrial application of solid acid–base catalysts

    Microsoft Academic Search

    Kozo Tanabe; Wolfgang F. Hölderich

    1999-01-01

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

  6. Catalyst and electrode research for phosphoric acid fuel cells

    Microsoft Academic Search

    A. C. Antoine; R. B. King

    1987-01-01

    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

  7. Modified zirconia solid acid catalysts for organic synthesis and transformations

    Microsoft Academic Search

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

    2005-01-01

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

  8. Organometallic catalysts for primary phosphoric acid fuel cells

    Microsoft Academic Search

    Fraser Walsh

    1987-01-01

    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

  9. 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 ...

  10. Surface acidity and degree of carburization of modified silver catalysts

    SciTech Connect

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

    1993-11-10

    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.

  11. Carbon-supported Pd–Ir catalyst as anodic catalyst in direct formic acid fuel cell

    Microsoft Academic Search

    Xin Wang; Yawen Tang; Ying Gao; Tianhong Lu

    2008-01-01

    It was reported for the first time that the electrocatalytic activity of the Carbon-supported Pd–Ir (Pd–Ir\\/C) catalyst with the suitable atomic ratio of Pd and Ir for the oxidation of formic acid in the direct formic acid fuel cell (DFAFC) is better than that of the Carbon-supported Pd (Pd\\/C) catalyst, although Ir has no electrocatalytic activity for the oxidation of

  12. Evolution of Enzymatic Activities in the Enolase Superfamily: Identification of the General Acid Catalyst in theActive Site of D-Glucarate Dehydratase from

    E-print Network

    Rayment, Ivan

    Catalyst in theActive Site of D-Glucarate Dehydratase from Escherichia coli, Andrew M. Gulick,§,| Brian K, Illinois 61801 ReceiVed April 11, 2001; ReVised Manuscript ReceiVed June 15, 2001 ABSTRACT: D-Glucarate of both D-glucarate and L-idarate to form 5-keto-4-deoxy-D-glucarate (KDG). Previous mutagenesis

  13. A carbon-supported PdP catalyst as the anodic catalyst in a direct formic acid fuel cell

    Microsoft Academic Search

    Lingling Zhang; Yawen Tang; Jianchun Bao; Tianhong Lu; Cun Li

    2006-01-01

    In this paper, it is reported for the first time that a carbon-supported Pd-P (Pd-P\\/C) catalyst for the anodic catalyst in the direct formic acid fuel cell (DFAFC) can be prepared. The Pd-P\\/C catalyst shows that its electrocatalytic activity and especially its stability for the oxidation of formic acid are much higher than that of a Pd\\/C catalyst. Therefore, the

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

    PubMed

    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

    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

  15. Esterification of formic acid, acrylic acid and methacrylic acid with cyclohexene in batch and distillation column reactors: ion-exchange resins as catalysts

    Microsoft Academic Search

    Basudeb Saha; Man Mohan Sharma

    1996-01-01

    Esterification of formic acid, acrylic acid and methacrylic acid with cyclohexene was carried out in the presence of cation-exchange resins as catalysts. Effect of various parameters, e.g. speed of agitation, catalyst particle size, catalyst loading, types of catalyst, temperature, mole ratio of the reactants, was studied to optimise the reaction conditions. The reaction of formic acid, with different concentrations in

  16. Solid acid catalysts for hydrolyzing oligosaccharides derived from corn fiber

    Microsoft Academic Search

    Young Mi Kim

    2005-01-01

    Pretreatment of lignocellulosic biomass is a key step in the fuel ethanol production process. Liquid hot water pretreatment of plant biomass produces a liquid stream with dissolved oligosaccharides which are usually converted to fermentable sugars by enzymatic hydrolysis. The goals of this study are to use a solid acid catalyst, instead of liquid mineral acids or enzymes, to understand the

  17. Acid-base properties of titanium-antimony oxides catalysts

    SciTech Connect

    Zenkovets, G.A.; Paukshtis, E.A.; Tarasova, D.V.; Yurchenko, E.N.

    1982-06-01

    The acid-base properties of titanium-antimony oxide catalysts were studied by the methods of back titration and ir spectroscopy. The interrelationship between the acid-base and catalytic properties in the oxidative ammonolysis of propylene was discussed. 3 figures, 1 table.

  18. Hydrolysis of oligosaccharides over solid acid catalysts: a review.

    PubMed

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

    2014-04-01

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

  19. Formic acid oxidation by carbon-supported palladium catalysts in direct formic acid fuel cell

    Microsoft Academic Search

    Jae Ho Choi; Soon Young Noh; Sam Duck Han; Soo Kyung Yoon; Chang-Soo Lee; Taek-Sung Hwang; Young Woo Rhee

    2008-01-01

    The oxidation of formic acid by the palladium catalysts supported on carbon with high surface area was investigated. Pd\\/C\\u000a catalysts were prepared by using the impregnation method. 30 wt% and 50 wt% Pd\\/C catalysts had a high BET surface area of\\u000a 123.7 m2\\/g and 89.9 m2\\/g, respectively. The fuel cell performance was investigated by changing various parameters such as anode

  20. Corrosion-resistant catalyst supports for phosphoric acid fuel cells

    SciTech Connect

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

    1990-01-01

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

  1. Role of solid acid catalysts in bio diesel production.

    PubMed

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

    2009-07-01

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

  2. High activity of Pd–WO 3\\/C catalyst as anodic catalyst for direct formic acid fuel cell

    Microsoft Academic Search

    Ligang Feng; Liang Yan; Zhiming Cui; Changpeng Liu; Wei Xing

    2011-01-01

    Pd nanoparticles supported on the WO3\\/C hybrid are prepared by a two-step procedure and the catalysts are studied for the electrooxidation of formic acid. For the purpose of comparison, phosphotungstic acid (PWA) and sodium tungstate are used as the precursor of WO3. Both the Pd–WO3\\/C catalysts have much higher catalytic activity for the electrooxidation of formic acid than the Pd\\/C

  3. Polymerization of ?-pinene using Lewis acidic ionic liquid as catalyst

    Microsoft Academic Search

    Shiwei Liu; Congxia Xie; Shitao Yu; Fusheng Liu

    2009-01-01

    Polymerization of ?-pinene was investigated in the presence of various Lewis acidic ILs. The results showed that ILs 1-n-butyl-3-methylimidazolium chloroaluminate-[C4mim]Cl-AlCl3, especially molar fraction of AlCl3x=0.67, indicated excellent catalytic performance for the polymerization of ?-pinene. It is also found that the product was easily separated from reaction mixture and the IL catalyst was of good reusability. Hence, a clean and environmentally

  4. Pb and Sb modified Pt\\/C catalysts for direct formic acid fuel cells

    Microsoft Academic Search

    Xingwen Yu; Peter G. Pickup

    2010-01-01

    PtPb\\/C and PtSb\\/C bi-metallic catalysts were synthesized by chemical deposition of Pb or Sb on a commercial 40% Pt\\/C catalyst. The performances of catalysts with a range of compositions were compared in a multi-anode direct formic acid fuel cell in order to optimize compositions and evaluate the statistical significance of differences between catalysts. The catalytic activity for formic acid oxidation

  5. High activity of Pd-WO3/C catalyst as anodic catalyst for direct formic acid fuel cell

    NASA Astrophysics Data System (ADS)

    Feng, Ligang; Yan, Liang; Cui, Zhiming; Liu, Changpeng; Xing, Wei

    2011-03-01

    Pd nanoparticles supported on the WO3/C hybrid are prepared by a two-step procedure and the catalysts are studied for the electrooxidation of formic acid. For the purpose of comparison, phosphotungstic acid (PWA) and sodium tungstate are used as the precursor of WO3. Both the Pd-WO3/C catalysts have much higher catalytic activity for the electrooxidation of formic acid than the Pd/C catalyst. The Pd-WO3/C catalyst prepared from PWA shows the best catalytic activity and stability for formic acid oxidation; it also shows the maximum power density of approximately 7.6 mW cm-2 when tested with a small single passive fuel cell. The increase of electrocatalytic activity and stability is ascribed to the interaction between the Pd and WO3, which promotes the oxidation of formic acid in the direct pathway. The precursors used for the preparation of the WO3/C hybrid support have a great effect on the performance of the Pd-WO3/C catalyst. The WO3/C hybrid support prepared from PWA is beneficial to the dispersion of Pd nanoparticles, and the catalyst has potential application for direct formic acid fuel cell.

  6. Preparation method of an ultrafine carbon supported Pd catalyst as an anodic catalyst in a direct formic acid fuel cell

    Microsoft Academic Search

    Lingling Zhang; Tianhong Lu; Jianchun Bao; Yawen Tang; Cun Li

    2006-01-01

    It was reported for the first time that the carbon supported Pd (Pd\\/C) catalyst was prepared in the aqueous solution with NH4F and H3BO3. The average size and the relative crystallinity of the Pd particles in the Pd\\/C catalyst prepared with this method are much lower than that of the Pd\\/C catalyst prepared with general reduction method because PdCl2 can

  7. An experimental comparison of transesterification process with different alcohols using acid catalysts

    Microsoft Academic Search

    N. Saravanan; Sukumar Puhan; G. Nagarajan; N. Vedaraman

    2010-01-01

    Vegetable oils and animal fats in their raw form have high viscosities that makes them unsuitable as fuels for diesel engines. Transesterification is one of the well-known processes by which fats and oils are converted into biodiesel. The reaction often makes use of acid\\/base catalyst. If the material possesses high free fatty acid then acid catalyst gives better results. In

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

    Microsoft Academic Search

    Yusaku Sakata; Akinori Muto

    1999-01-01

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

  9. Improvement of electrocatalytic performance of carbon supported Pd anodic catalyst in direct formic acid fuel cell by ethylenediamine-tetramethylene phosphonic acid

    NASA Astrophysics Data System (ADS)

    Lu, Liang; Li, Huanzhi; Hong, Yujie; Luo, Yafen; Tang, Yawen; Lu, Tianhong

    2012-07-01

    The direct formic acid fuel cell (DFAFC) has two major shortcomings that limit its lifespan and performance: (i) the poor electrocatalytic stability of the carbon supported Pd (Pd/C) catalyst for the oxidation of formic acid and (ii) rapid decomposition of formic acid over the Pd/C catalyst. To solve the problems, the Pd/C catalyst is modified with ethylenediamine-tetramethylene phosphonic acid (EDTMP). The resulting catalyst is designated as Pd/C-E catalyst. It is found that the Pd/C-E catalyst can inhibit the decomposition of formic acid and promote the oxidation of formic acid through the direct pathway. Consistently, the Pd/C-E catalyst is significantly protected from CO poisoning. As compared to the Pd/C catalyst, the electrocatalytic performance of the Pd/C-E catalyst is significantly superior. These results provide the first proof of the concept that DFAFC can be significantly improved by Pd/C-E catalyst.

  10. Evaluation of direct formic acid fuel cells with catalyst layers coated by electrospray

    Microsoft Academic Search

    Yongchai Kwon; Seungmin Baek; Byungwan Kwon; Jinsoo Kim; Jonghee Han

    2010-01-01

    We investigated cell performance and performed phenomenological analyses of direct formic acid fuel cells (DFAFCs) incorporating\\u000a anode (palladium) and cathode (platinum) catalysts prepared using a new electrospray coating technique. To optimize the design\\u000a of the DFAFC, we examined the cell performance by the Pd catalyst loading and formic acid feed rate. Of Pd catalyst loaded\\u000a samples, 3 mg\\/cm2 sample showed

  11. Carbon supported PtBi catalysts for direct formic acid fuel cells

    Microsoft Academic Search

    Xingwen Yu; Peter G. Pickup

    2011-01-01

    Carbon supported PtBi bimetallic catalysts (PtBi\\/C) prepared by depositing Bi on a commercial Pt\\/C catalyst and by codeposition of Pt and Bi have been compared for formic acid oxidation in a multi-anode direct formic acid fuel cell. Both types of catalyst gave much higher cell performances than the Pt\\/C, with only low amounts of Bi (Pt to Bi mole ratios

  12. Deactivation resistant PdSb\\/C catalysts for direct formic acid fuel cells

    Microsoft Academic Search

    Xingwen Yu; Peter G. Pickup

    2010-01-01

    Formic acid oxidation at novel carbon supported PdSb alloy catalysts has been studied in a multi-anode direct formic acid fuel cell with supporting mechanistic studies in a conventional electrochemical cell. The optimized PdSb\\/C catalysts show better high voltage and long term performances than a comparable commercial Pd\\/C catalyst and much better resistance to poisoning (deactivation). Electrochemical stripping voltammograms show that

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

    Microsoft Academic Search

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

    2009-01-01

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

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

    Microsoft Academic Search

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

    2009-01-01

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

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

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

    Microsoft Academic Search

    Karen Wilson; James H. Clark

    2000-01-01

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

  17. Hydrogenation of succinic acid to ?-butyrolactone (GBL) over palladium catalyst supported on alumina xerogel: Effect of acid density of the catalyst

    Microsoft Academic Search

    Ung Gi Hong; Sunhwan Hwang; Jeong Gil Seo; Joongwon Lee; In Kyu Song

    2011-01-01

    Mesoporous alumina xerogel (AX) supports prepared by a sol–gel method were calcined at various temperatures to control their acid property. Palladium catalysts supported on mesoporous alumina xerogel (Pd\\/AX) were then prepared by an impregnation method. The Pd\\/AX catalysts were characterized by XRD, BET, NH3-TPD, N2 adsorption–desorption isotherm, and H2 chemisorption analyses. Liquid-phase hydrogenation of succinic acid to ?-butyrolactone (GBL) over

  18. Bismuth-promoted palladium catalysts for the selective oxidation of glyoxal into glyoxalic acid

    Microsoft Academic Search

    F Alardin; P Ruiz; B Delmon; M Devillers

    2001-01-01

    The incorporation of bismuth in carbon-supported Pd-based catalysts is shown to increase significantly the catalytic activity in the selective oxidation of glyoxal into glyoxalic acid. Main side products are glycolic acid resulting from Cannizzaro dismutation and oxalic acid, generated by further oxidation of glyoxalic acid. Catalysts characterized by different Bi\\/Pd ratios (with Pd+Bi=10wt.%) were prepared according to various experimental procedures

  19. Acidity and catalytic activity of zeolite catalysts bound with silica and alumina

    E-print Network

    Wu, Xianchun

    2004-09-30

    -framework alumina in zeolites to form a new protonic acid. SiO2-bound catalysts have less strong acidity, Bronsted acidity and Lewis acidity than the zeolite powder. Also, the strength of strong acid sites of the zeolites is reduced when silica is embedded...

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

    PubMed

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

    2013-04-01

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

  1. The behavior of palladium catalysts in direct formic acid fuel cells

    Microsoft Academic Search

    Yimin Zhu; Zakia Khan; R. I. Masel

    2005-01-01

    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?230mWcm?2 at relatively high voltages of 0.40?0.50V

  2. Novel Pd–Pb\\/C bimetallic catalysts for direct formic acid fuel cells

    Microsoft Academic Search

    Xingwen Yu; Peter G. Pickup

    2009-01-01

    Novel carbon supported bimetallic palladium–lead (Pd–Pb\\/C) anode catalysts have been prepared for use in direct formic acid fuel cells (DFAFC). Comparative studies, with a Pd\\/C catalyst, of performances, deactivation, and reactivation were performed in a multi-anode DFAFC. These Pd–Pb\\/C catalysts were found to be more resistant to deactivation in the DFAFC than Pd\\/C and to consistently show better long-term performances.

  3. The selective sorption of solvents on sulphonic acid polymer catalyst in binary mixtures

    Microsoft Academic Search

    Johanna Lilja; Elena Murzina; Henrik Grénman; Hanna Vainio; Tapio Salmi; Dmitry Yu. Murzin

    2005-01-01

    The sorption behaviour of a polymer-supported sulphonic acid catalyst, Smopex-101, was studied in different solvent mixtures at 60 and 70°C. The physical characteristics of the catalyst were investigated. Six catalysts with activities, ranging from 2.1 to 3.6mmol\\/g, various degrees of cross-linking, 0%, 0.5%, 2% and 4% divinylbenzene as well as dimensions (lengths and diameters) were studied. The analyses of the

  4. Chiral Brønsted Acid as a True Catalyst: Asymmetric Mukaiyama Aldol and Hosomi-Sakurai Allylation Reactions.

    PubMed

    Sai, Masahiro; Yamamoto, Hisashi

    2015-06-10

    Highly diastereo- and enantioselective Mukaiyama aldol reaction catalyzed by a new chiral Brønsted acid, N-(perfluorooctanesulfonyl)thiophosphoramide, is described. The perfluorooctyl substituent on the sulfonyl group of the catalyst plays an essential role in the stereoselection. The catalyst also allows the asymmetric Hosomi-Sakurai allylation, which has been considerably challenging due to the low reactivity of allylsilanes. (29)Si and (31)P NMR monitoring reveals the characteristic feature of the thiophosphoramide catalyst, acting as a strong Brønsted acid even in the presence of excess silyl nucleophiles, which cannot be found in other related phosphoric acid analogues. PMID:26017677

  5. Effects of Nafion loading in anode catalyst inks on the miniature direct formic acid fuel cell

    Microsoft Academic Search

    Robert D. Morgan; John L. Haan; Richard I. Masel

    2010-01-01

    Nafion, within the anode and cathode catalyst layers, plays a large role in the performance of fuel cells, especially during the operation of the direct formic acid fuel cell (DFAFC). Nafion affects the proton transfer in the catalyst layers of the fuel cell, and studies presented here show the effects of three different Nafion loadings, 10wt.%, 30wt.% and 50wt.%. Short

  6. Performance of the direct formic acid fuel cell with electrochemically modified palladium–antimony anode catalyst

    Microsoft Academic Search

    John L. Haan; Kristin M. Stafford; Robert D. Morgan; Richard I. Masel

    2010-01-01

    Previous work has shown that palladium catalysts are quite active for formic acid electrooxidation, but the catalysts need to be periodically regenerated to remove a CO impurity from the surface. The objective of this paper is to determine whether antimony additions could suppress the CO formation under fuel cell conditions. We find that antimony doubles the rate of reaction in

  7. Nuclear magnetic resonance studies on the acidity of zeolites and related catalysts

    Microsoft Academic Search

    H. Pfeifer; D. Freude; M. Hunger

    1985-01-01

    A review is given on the possibilities of the various nuclear magnetic resonance techniques which have been applied up till now to study quantitatively the acidity of zeolites and related catalysts. From the intensity of the wide line proton magnetic resonance signal of unloaded catalysts, the total concentration of protons can be determined. A loading of the samples with (deuterated)

  8. Performance characterization of direct formic acid fuel cell using porous carbon-supported palladium anode catalysts

    Microsoft Academic Search

    Sam Duck Han; Jae Ho Choi; Soon Young Noh; Soo Kyung Yoon; Young Woo Rhee

    2009-01-01

    Palladium particles supported on porous carbon of 20 and 50 nm pore diameters were prepared and applied to the direct formic\\u000a acid fuel cell (DFAFC). Four different anode catalysts with Pd loading of 30 and 50 wt% were synthesized by using impregnation\\u000a method and the cell performance was investigated with changing experimental variables such as anode catalyst loading, formic\\u000a acid

  9. Catalysts

    NSDL National Science Digital Library

    2012-07-19

    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.

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

    PubMed

    Kibsgaard, Jakob; Jaramillo, Thomas F

    2014-12-22

    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

  11. Transition metal sulfide hydrogen evolution catalysts for hydrobromic acid electrolysis.

    PubMed

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

    2013-01-01

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

  12. Chance and necessity in the selection of nucleic acid catalysts

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

    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.

  13. 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...

  14. Surface acidity and basicity: General concepts

    Microsoft Academic Search

    Adriano Zecchina; Carlo Lamberti; Silvia Bordiga

    1998-01-01

    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

  15. Study of carbon-supported Au catalyst as the cathodic catalyst in a direct formic acid fuel cell prepared using a polyvinyl alcohol protection method

    Microsoft Academic Search

    Wei Chen; Yawen Tang; Jianchun Bao; Ying Gao; Changpeng Liu; Wei Xing; Tianhong Lu

    2007-01-01

    In this paper, it is reported for the first time that a carbon-supported Au (Au\\/C) catalyst for the cathodic catalyst in a direct formic acid fuel cell (DFAFC) was prepared using a polyvinyl alcohol (PVA) protection method. The results indicated that for oxygen reduction, the electrocatalytic activity of the Au\\/C catalyst prepared with the PVA protection method is much better

  16. 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

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

    1997-01-01

    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

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

    DOEpatents

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

    1999-01-01

    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.

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

    Microsoft Academic Search

    A. Mikolajczuk; A. Borodzinski; P. Kedzierzawski; L. Stobinski; B. Mierzwa; R. Dziura

    2011-01-01

    A new carbon black supported palladium catalyst for direct formic acid fuel cell applications has been prepared and characterized by X-ray diffraction. Bi-modal distribution of Pd crystallite sizes was observed. The average Pd size for crystallites in small size and large size ranges were about 2.7nm and 11.2nm, respectively. The initial activity of the catalyst in the oxidation of formic

  19. Carbon supported ruthenium chalcogenide as cathode catalyst in a microfluidic formic acid fuel cell

    Microsoft Academic Search

    A. S. Gago; D. Morales-Acosta; L. G. Arriaga; N. Alonso-Vante

    2011-01-01

    This work reports the electrochemical measurements of 20wt.% RuxSey\\/C for oxygen reduction reaction (ORR) in presence of different concentration of HCOOH and its use as cathode catalyst in a microfluidic formic acid fuel cell (?FAFC). The results were compared to those obtained with commercial Pt\\/C. Half-cell electrochemical measurements showed that the chalcogenide catalyst has a high tolerance and selectivity towards

  20. Preparation of Pt-Pd catalysts for direct formic acid fuel cell and their characteristics

    Microsoft Academic Search

    Ki Ho Kim; Jae-Keun Yu; Hyo Song Lee; Jae Ho Choi; Soon Young Noh; Soo Kyung Yoon; Chang-Soo Lee; Taek-Sung Hwang; Young Woo Rhee

    2007-01-01

    Pt-Pd catalysts were prepared by using the spontaneous deposition method and their characteristics were analyzed in a direct\\u000a formic acid fuel cell (DFAFC). Effects of calcination temperature and atmosphere on the cell performance were investigated.\\u000a The calcination temperatures were 300, 400 and 500 °C and the calcination atmospheres were air and nitrogen. The fuel cell\\u000a with the catalyst calcined at

  1. Carbon supported platinum–gold alloy catalyst for direct formic acid fuel cells

    Microsoft Academic Search

    J. B. Xu; T. S. Zhao; Z. X. Liang

    2008-01-01

    The Pt–Au nanoparticles with 1:1 atomic ratio supported on carbon powder were prepared by the co-reduction method using N,N-dimethylformamide coordinated Pt–Au complex as a precursor. Cyclic voltammetry results demonstrated that the PtAu\\/C catalyst exhibited a higher activity for the formic acid oxidation reaction than did the commercial Pt\\/C catalyst, reflected by its lower onset potential and higher peak current. The

  2. Catalytic ozonation of phenolic acids over a Mn–Ce–O catalyst

    Microsoft Academic Search

    Rui C. Martins; Rosa M. Quinta-Ferreira

    2009-01-01

    Catalytic ozonation of a simulated phenolic wastewater composed by six acids: syringic, vanillic, 3,4,5-trimethoxybenzoic, veratric, protocatechuic and 4-hydroxybenzoic normally present in olive mill wastewaters was studied over a Mn–Ce–O laboratorial catalyst under different operating conditions. A high improvement in total organic carbon (TOC) degradation was observed even when low catalyst concentrations were used when compared with single ozonation. The influence

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

    SciTech Connect

    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

    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.

  4. Stability of mechanical properties of vanadium catalysts for sulfuric acid manufacture in a humid atmosphere

    SciTech Connect

    Manaeva, L.N.; Malikman, V.I.; Dobkina, E.I.; Mukhlenov, I.P.

    1982-01-10

    Experience of the industrial use of catalysts in sulfuric acid manufacture shows that as the result of saturation with moisture the catalyst grains may lose strength and disintegrate during use. However, this question has not been examined experimentally and the mechanism of the effect has not been studied. Fresh catalyst may come into contact with atmospheric moisture during storage, and used catalyst as the result of uncontrolled leakages during stoppages and recharging of the catalytic converters. In the course of normal operation water vapor enters the catalytic converters together with sulfuric acid mist with the gas stream if the latter has not been adequately dried. The purpose of the present work was to study the mechanical stability, in a humid atmosphere, of industrial sulfuric acid catalysts: granulated SVD (5 mm in diameter) and SVS rings (8 x 8 x 2.5 mm). The catalysts were studied both in the fresh state and after use in a laboratory catalytic apparatus of the flow type.

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

    Microsoft Academic Search

    Xingwen Yu; Peter G. Pickup

    2009-01-01

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

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

    PubMed Central

    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

    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%.

  7. Oxidation catalyst

    DOEpatents

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

    2010-11-09

    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.

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

    SciTech Connect

    Boszormenyi, I.

    1991-05-01

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

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

    SciTech Connect

    Boszormenyi, I.

    1991-05-01

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

  10. Electrocatalytic properties of Pd/C catalyst for formic acid electrooxidation promoted by europium oxide

    NASA Astrophysics Data System (ADS)

    Feng, Ligang; Yao, Shikui; Zhao, Xiao; Yan, Liang; Liu, Changpeng; Xing, Wei

    2012-01-01

    It is found that the electrocatalytic activity and stability of Pd/C nanocatalyst for formic acid electrooxidation are enhanced by the introduction of EuOx. The morphology, composition and electrocatalytic properties of the PdEuOx/C catalyst are investigated by the transmission electronmicroscopy, energy dispersive X-ray analysis, X-ray diffraction, the linear sweep voltammetry and chronoamperometry, respectively. The EDX results confirm the existence of EuOx in the PdEuOx/C catalysts. The XRD results indicate that the Pd is in the state of face-centered cubic phase structure. The linear sweeping voltammetry and chronoamperometry measurements show that the current of formic acid electrooxidation on the PdEuOx/C catalyst is ca. 2.5 times and 9 times as high as that of the home-made Pd/C catalyst, respectively; moreover, the performances are also much higher than the commercial Pd/C catalyst. The high performances can be attributed to the larger electrochemical surface area and the electronic effect of the EuOx in the PdEuOx/C catalyst.

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

    Microsoft Academic Search

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

    2011-01-01

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

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

    E-print Network

    Regalbuto, John R.

    1998-01-01

    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, lean NOx catalysts has been determined by studying the individual steps in the selective reduction

  13. Codeposited PtSb/C catalysts for direct formic acid fuel cells

    NASA Astrophysics Data System (ADS)

    Yu, Xingwen; Pickup, Peter G.

    2011-10-01

    Carbon supported PtSb catalysts were synthesized by codeposition of platinum and antimony on Vulcan® carbon black. X-ray diffraction (XRD) analysis revealed that the Sb was alloyed with the Pt while XPS indicated that a large fraction of the Sb was in an oxidized state, with only partial alloying. The performances of catalysts with a range of compositions were compared in a multi-anode direct formic acid fuel cell (DFAFC). A 0.29 mol fraction of Sb was found to provide the best performance with a maximum specific power output of 280 W g-1 Pt. CO stripping results indicated that the addition of Sb at this optimum level greatly suppressed both CO adsorption and H adsorption/desorption, as well as promoting oxidative stripping of CO. The results are compared with those for previously studied catalysts prepared by the reductive deposition of Sb on a carbon supported Pt catalyst.

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

    PubMed

    Neelakandeswari, N; Karvembu, R; Dharmaraj, N

    2013-04-01

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

  15. Preparation and application of zirconium sulfate supported on SAPO-34 molecular sieve as solid acid catalyst for esterification

    SciTech Connect

    Xu, Dongyan, E-mail: xdy0156@sina.com; Ma, Hong; Cheng, Fei

    2014-05-01

    Graphical abstract: - Highlights: • SAPO-34 supported zirconium sulfate solid acid catalyst was prepared. • Esterification of acetic acid with ethanol can be catalyzed by ZS/SAPO-34. • The hydration of ZS is vital to the acidic property and catalytic performance. • The ZS/SAPO-34 catalyst treated at 200 °C shows good reusability. - Abstract: Zirconium sulfate (ZS) was supported on SAPO-34 molecular sieve by using an incipient wetness impregnation method with zirconium sulfate as the precursor. The as-prepared catalysts were used as solid acid catalyst for esterification reaction of acetic acid with ethanol. The influence of calcination temperature on the acidic property, catalytic activity, and reusability of ZS/SAPO-34 catalysts were mainly investigated. FT-IR, SEM, EDS and TG analysis have been carried out to demonstrate the characteristics of ZS/SAPO-34 catalysts. It was found that the 30 wt%ZS/SAPO-34 catalysts display the property of superacid irrespective of calcination temperature. The ZS/SAPO-34 catalyst treated at 200 °C can enhance the interaction between the supported ZS and SAPO-34 and keep the catalyst remaining substantially active after several reaction cycles. However, further increasing calcination temperature will cause the transfer of ZS from hydrate to anhydrous phase, and thus the decrease of activity.

  16. Catalyst-free direct decarboxylative coupling of ?-keto acids with thiols: a facile access to thioesters.

    PubMed

    Yan, Kelu; Yang, Daoshan; Wei, Wei; Zhao, Jing; Shuai, Yuanyuan; Tian, Laijin; Wang, Hua

    2015-07-14

    A novel, efficient, and catalyst-free strategy has been initially developed for the construction of thioesters via the direct radical oxidative decarboxylation of ?-keto acids with thiols, and the corresponding target products were obtained in moderate to good yields. It offers an alternative approach for the synthesis of useful diverse thioesters. PMID:26058949

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Our objective was to compare 1.09 M methanolic HCl to 14% BF3 in methanol as catalysts for direct transesterification of fatty acids in freeze-dried forage samples. Samples included blue grama (Bouteloua gracilis), fringed sage (Artemisia frigida), western wheatgrass (Pascopyrum smithii), needle-an...

  18. Oxidizing of ferulic acid with the use of polyoxometalates as catalysts

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

    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.

  19. An in situ Fourier transform infrared study of formic acid adsorption on a polycrystalline silver catalyst

    Microsoft Academic Search

    G. J. Millar; J. B. Metson; G. A. Bowmaker; R. P. Cooney

    1994-01-01

    Infrared spectra are reported for the adsorption of formic acid on a polycrystalline silver catalyst after various degrees of oxidation. Three distinct chemisorbed species were identified, two of which corresponded to adsorbed formate on Ag(110) and Ag(111) crystal planes and the other to adsorbed formate on a silver site modified by the presence of subsurface oxygen. Moreover, it was discovered

  20. Screening of PdM and PtM catalysts in a multi-anode direct formic acid fuel cell

    Microsoft Academic Search

    Xingwen Yu; Peter G. Pickup

    2011-01-01

    Direct formic acid fuel cells (DFAFC) currently employ either Pt-based or Pd-based anode catalysts for oxidation of formic\\u000a acid. However, improvements are needed in either the activity of Pt-based catalysts or the stability of Pd-based catalysts.\\u000a In this study, a number of carbon-supported Pt-based and Pd-based catalysts, were prepared by co-depositing PdM (M = Bi, Mo,\\u000a or V) on Vulcan® XC-72 carbon

  1. Acylation of different amino derivatives with fatty acids on UL-MFI-type catalysts

    Microsoft Academic Search

    Mariana Musteata; Vasile Musteata; Alina Dinu; Mihaela Florea; Vinh-Thang Hoang; Do Trong-On; Serge Kaliaguine; Vasile I. Parvulescu

    2007-01-01

    Acylation of different amino derivatives (ethanol amine, diethanol amine, N-aminoethylpiperazine) was carried out under green conditions with oleic acid or tail oil fatty acids. The experiments were carried out using as heterogeneous catalysts mesoporous Al-Meso and UL-ZSM-5 with Si\\/Al ratios between 100 and 20, in the range of the tempera- tures 80-180 °C without any solvent or in octane or

  2. Synthesis of polylactic acid by direct polycondensation under vacuum without catalysts, solvents and initiators

    Microsoft Academic Search

    Feerzet Achmad; Kenji Yamane; Shi Quan; Takao Kokugan

    2009-01-01

    In order to reduce the production cost of polylactic acid (PLA), l-lactic acid was polymerized by direct polycondensation (DP) under vacuum without catalysts, solvents and initiators. Experiments were conducted at polymerization temperatures (Tp) of 150–250°C. The maximum PLA molecular weight obtained was 90kDa at 200°C after 89h under vacuum. Above 200°C, PLA is thermally degraded by specific scission. The DP

  3. Performance degradation of direct formic acid fuel cell incorporating a Pd anode catalyst

    NASA Astrophysics Data System (ADS)

    Jung, Won Suk; Han, Jonghee; Yoon, Sung Pil; Nam, Suk Woo; Lim, Tae-Hoon; Hong, Seong-Ahn

    2011-05-01

    Electrochemical and physical analysis is employed to verify the performance degradation mechanism in direct formic acid fuel cells (DFAFCs). The power density of a single cell measured at 200 mA cm-2 decreases by 40% after 11 h of operation. The performance of the single cell is partly recovered however, by a reactivation process. Various analytical methods such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electrochemical impedance spectroscopy (EIS) are used to investigate the mechanism of performance degradation. The analytical results show that the electrolyte membranes in the DFAFC are stable for 11 h of operation after the reactivation process. The major factors causing performance degradation in the DFAFC are an increment in the anode charge-transfer resistance and a growth in the particle size of the Pd anode catalyst. The anode charge-transfer resistance, confirmed by EIS, increases with operation time and is due to poisoning of the catalyst surface. Although it is not clear what chemical species poisons the catalyst surface, the catalyst surface is cleaned by the reactivation process. Performance losses caused by surface poisoning are completely recovered by the reactivation process. Increase in catalyst size induces a reduction in active surface area, and the performance loss caused by the growth in catalyst size cannot be recovered by the reactivation process.

  4. The behavior of palladium catalysts in direct formic acid fuel cells

    NASA Astrophysics Data System (ADS)

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

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2011-07-01

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

  6. Surface component distribution in a vanadium-molybdenum oxide catalyst for making acrylic acid from acrolein

    SciTech Connect

    Zazhigalov, V.A.; Kholyavenko, K.M.

    1986-11-01

    A scanning electron microscope and microprobe analyzer have been used to examine the surfaces of vanadium-molybdenum catalysts on aerosil. It is found that the phase VMo/sub 3/O/sub 11/ is formed, which is dispersed on the SiO/sub 2/. MoO/sub 3/ crystals of various shapes occur at the surface of the dispersed phase. It is suggested that this catalyst is highly active in oxidizing acrolein to acrylic acid because of the presence of VMo/sub 3/O/sub 11/.

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

    SciTech Connect

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

    1996-12-31

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

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

    PubMed

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

    2013-07-01

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

  9. Characterization and application of electrodeposited Pt, Pt\\/Pd, and Pd catalyst structures for direct formic acid micro fuel cells

    Microsoft Academic Search

    R. S. Jayashree; J. S. Spendelow; J. Yeom; C. Rastogi; M. A. Shannon; P. J. A. Kenis

    2005-01-01

    In this work, we study the preparation, structural characterization, and electrocatalytic analysis of robust Pt and Pd-containing catalyst structures for silicon-based formic acid micro fuel cells. The catalyst structures studied were prepared and incorporated into the silicon fuel cells by a post CMOS-compatible process of electrodeposition, as opposed to the more common introduction of nanoparticle-based catalyst by ink painting. Robust,

  10. Fe x C–C hybrid material as a support for Pt anode catalyst in direct formic acid fuel cell

    Microsoft Academic Search

    Xiao-Ming Wang; Yong-Yao Xia

    2009-01-01

    FexC–C hybrid material as a support for Pt anode catalyst in direct formic acid fuel cell was investigated for the first time. The resultant Pt\\/FexC–C catalysts were prepared by using a simple reduction reaction to load Pt on FexC–C hybrid material, which was synthesized through the carbonization of sucrose and Fe(NO3)3. It was found that the Pt\\/FexC–C catalysts exhibited excellent

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

    E-print Network

    Li, Shih-ming

    1996-01-01

    of the hydantoin intermediate under basic conditions or of the o(- 2,28-30 cyano compounds with acidic conditions resulted in the formation of a mixture of amino acids. The pure cis- and trans- isomers obtained by these methods were isolated by recrystallization... was acidified with 50% sulfuric acid, extracted again with ether (8 x 25 mL). The ether extracts were washed with water, dried over MgSO4, and concentrated. Recrystallization from ether give the title compound as colorless crystal. Yield: mp: 11. 5 g (31...

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

    NASA Astrophysics Data System (ADS)

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

    2011-05-01

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

  13. Catalytic pyrolysis of cellulose in sulfolane with some acidic catalysts

    Microsoft Academic Search

    Haruo Kawamoto; Shinya Saito; Wataru Hatanaka; Shiro Saka

    2007-01-01

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

  14. Iron type catalysts for the ozonation of oxalic acid in water

    Microsoft Academic Search

    Fernando J. Beltrán; Francisco J. Rivas; R. Montero-de-Espinosa

    2005-01-01

    Two iron catalysts (Fe(III) and Fe2O3\\/Al2O3) have been used in the ozonation of oxalic acid in water at pH 2.5. Percentage removals of oxalic acid were 1.8%, 7% and 30% corresponding to the non-catalytic, homogeneous (Fe(III)) and heterogeneous (Fe2O3\\/Al2O3) catalytic ozonations, respectively. Catalytic oxalic acid ozonation leads in all cases to total mineralization. The mechanism of ozonation likely develops through

  15. 40 CFR 76.3 - General Acid Rain Program provisions.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 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...

  16. 40 CFR 76.3 - General Acid Rain Program provisions.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 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...

  17. 40 CFR 76.3 - General Acid Rain Program provisions.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 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...

  18. 40 CFR 76.3 - General Acid Rain Program provisions.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 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...

  19. 40 CFR 76.3 - General Acid Rain Program provisions.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 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...

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

    Microsoft Academic Search

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

    2011-01-01

    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

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

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

    PubMed Central

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

    2014-01-01

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

  3. Relationship between the structure of Ru\\/CeO 2 catalysts and their activity in the catalytic ozonation of succinic acid aqueous solutions

    Microsoft Academic Search

    F Delanoë; B Acedo; N Karpel Vel Leitner; B Legube

    2001-01-01

    Two Ru\\/CeO2 catalysts were used for the study of the catalytic ozonation of aqueous solutions of succinic acid (SA). These catalysts were prepared either by impregnation (I) or by acid exchange (AE). The objectives were (1) to determine the efficiency towards the oxidation of the organic molecule in relation to the catalysts characterization, and (2) to examine the modifications of

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

    PubMed

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

    2012-01-01

    A highly efficient hydrogen generation from formic acid/sodium formate aqueous solution catalyzed by in situ synthesized Pd/C with citric acid has been successfully achieved at room temperature. Interestingly, the presence of citric acid during the formation and growth of the Pd nanoparticles on carbon can drastically enhance the catalytic property of the resulted Pd/C, on which the conversion and turnover frequency for decomposition of formic acid/sodium formate system can reach the highest values ever reported of 85% within 160 min and 64 mol H(2) mol(-1) catalyst h(-1), respectively, at room temperature. The present simple, low cost, but highly efficient CO-free hydrogen generation system at room temperature is believed to greatly promote the practical application of formic acid system on fuel cells. PMID:22953041

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

    PubMed Central

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

    2012-01-01

    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

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

    NASA Astrophysics Data System (ADS)

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

    2012-08-01

    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.

  7. Composites of manganese oxide with carbon materials as catalysts for the ozonation of oxalic acid.

    PubMed

    Orge, C A; Órfão, J J M; Pereira, M F R

    2012-04-30

    Manganese oxide and manganese oxide-carbon composites were prepared and tested as catalysts for the removal of oxalic acid by ozonation. Their performances were compared with the parent carbon material (activated carbon or carbon xerogel) used to prepare the composites. Oxalic acid degradation by carbon materials is slower than that attained with manganese oxide or manganese oxide-carbon composites. A complete degradation after 90 and 45 min of reaction was obtained for carbon materials and for the catalysts containing manganese, respectively. The ozonation in the presence of the prepared composites are supposed to occur mainly by surface reactions, following a direct oxidation mechanism by molecular ozone and/or surface oxygenated radicals. PMID:22341747

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

    Microsoft Academic Search

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

    2006-01-01

    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

  9. Effect of temperature, oxidant and catalyst loading on the performance of direct formic acid fuel cell

    Microsoft Academic Search

    Jeong Soo Kim; Jae Keun Yu; Hyo Song Lee; Jin Yong Kim; Young Chun Kim; Jong Hee Han; In Hwan Oh; Young Woo Rhee

    2005-01-01

    We investigated the effect of temperature, oxidant and catalyst loading on the performance of direct formic acid fuel cell\\u000a (DFAFC). When oxidant was changed from air to oxygen, the power density was increased to 17.3 mW\\/ cm2 at 25 ‡C. The power density of DFAFC operated with oxygen showed a maximum value of 40.04 mW\\/cm2 with the temperature rise from

  10. Poisoning and regeneration of Pd catalyst in direct formic acid fuel cell

    Microsoft Academic Search

    Yi Zhou; Jianguo Liu; Jilei Ye; Zhigang Zou; Jinhua Ye; Jun Gu; Tao Yu; Aidong Yang

    2010-01-01

    Palladium catalyst poisoned in the anode of direct formic acid fuel cell (DFAFC) during constant current discharging can be fully regenerated by a non-electrochemical method, i.e. just switching pure water to DFAFC for 1h. Electrochemical impedance spectrum of DFAFC during the discharging and regeneration were recorded and analyzed. No much difference could be found for the high-frequency resistance of DFAFC

  11. Performance increase of microfluidic formic acid fuel cell using Pd\\/MWCNTs as catalyst

    Microsoft Academic Search

    D. Morales-Acosta; Luis A. Godinez; L. G. Arriaga

    2010-01-01

    This paper shows that the combination of an O2 saturated acidic fluid setup (O2-setup) and a composite of Pd nanoparticles supported on multiwalled-carbon nanotubes (Pd\\/MWCNTs) as anode catalyst material, results in the improvement of microfluidic fuel cell performance. Microfluidic fuel cells were constructed and evaluated at low HCOOH concentrations (0.1 and 0.5M) using Pd\\/V XC-72 and Pd\\/MWCNTs as anode and

  12. Activation of C 2–C 4 alkanes over acid and bifunctional zeolite catalysts

    Microsoft Academic Search

    G. Caeiro; R. H. Carvalho; X. Wang; M. A. N. D. A. Lemos; F. Lemos; M. Guisnet; F. Ramôa Ribeiro

    2006-01-01

    This review paper presents the significant advances which were made in the last decade in the understanding of the transformation over acid and bifunctional zeolite catalysts of the cheap and readily available C2–C4 alkanes into more valuable products: mechanism of activation, reaction scheme, nature of the active sites. Both the transformations of pure alkanes: n-butane isomerization, C2–C4 alkane aromatization and

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

    Microsoft Academic Search

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

    2011-01-01

    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

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

    PubMed

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

    2015-03-01

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

  15. Memory effect-enhanced catalytic ozonation of aqueous phenol and oxalic acid over supported Cu catalysts derived from hydrotalcite

    Microsoft Academic Search

    Masato Shiraga; Tomonori Kawabata; Dalin Li; Tetsuya Shishido; Kenji Komaguchi; Tsuneji Sano; Katsuomi Takehira

    2006-01-01

    Mg\\/Al supported metal (Fe, Co, Ni and Cu) oxide catalysts were prepared by co-precipitation of hydrotalcite-like clay materials as precursors, calcined, and used for the ozonation reaction of phenol and oxalic acid. The reaction was carried out using the catalyst and aqueous solution of phenol or oxalic acid in an O3\\/O2 mixed gas-flow at 20 °C. In the ozonation of phenol,

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

    PubMed

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

    2011-02-01

    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

  17. Liquefaction of municipal waste plastics in VGO over acidic and non-acidic catalysts

    Microsoft Academic Search

    Selhan Karagöz; Tamer Karayildirim; Suat Uçar; Mithat Yuksel; Jale Yanik

    2003-01-01

    Co-processing of municipal waste plastics (MWP) with vacuum gas oil (VGO) over HZSM-5, DHC-8 (commercial silica–alumina catalyst) and cobalt loaded active carbon catalyst has been comparatively studied. Co-processing experiments were carried out under hydrogen atmosphere at temperatures between 425 and 450°C. The composition, sulphur and chlorine amount of liquid products were determined. The product distribution and the composition of liquids

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

    SciTech Connect

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

    1997-02-01

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

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

    PubMed

    Nasr-Esfahani, Masoud; Abdizadeh, Tooba

    2013-07-01

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

  20. Acid-Base Mechanism for Ruthenium-Based Water Oxidation Catalysts

    SciTech Connect

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

    2010-05-17

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

  1. Influence of bi modification of pt anode catalyst in direct formic acid fuel cells.

    PubMed

    Kang, Sungjin; Lee, Jaeyoung; Lee, Jae Kwang; Chung, Seung-Young; Tak, Yongsug

    2006-04-13

    The influence of Bi modification of Pt anode catalyst on the performance of direct formic acid fuel cells was investigated. Compared with the unmodified Pt anode, the Bi modified Pt (PtBi(m)) electrode prepared by under-potential deposition (UPD) caused faster electrocatalytic oxidation of formic acid at the same value of the overpotential, and thus, PtBi(m) resulted in an increase in the power performance of direct formic acid fuel cells. Electrochemical impedance spectra helped to explain the difference of performance between the unmodified Pt and Bi modified Pt electrodes. Solution conductivity and dehydration phenomena occurring in highly concentrated formic acid solutions can also explain the higher power performance of PtBi(m). PMID:16599497

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

    PubMed

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

    2014-09-01

    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

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

    PubMed

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

    2015-02-01

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

  4. Catalyst for NO x removal in nitric-acid plant gaseous effluents

    NASA Astrophysics Data System (ADS)

    Avila, P.; Barthelemy, C.; Bahamonde, A.; Blanco, J.

    The behaviour of a V 2O 5?WO 3?TiO 2 phosphorated catalyst, in the Selective Catalytic Reduction (SCR) of equimolar NO + NO 2 mixtures, is studied in order to analyse the possibility of its industrial utilization for the treatment of nitric-acid plant stack gases. With this new catalyst, an NO x conversion higher than 90% molar can be achieved, the ammonia concentration at the exit gas being lower than that required to form ammonium salts, throughout the temperature range of commercial interest: 250-450°C, at a relatively high space velocity (GHSV ? 40000 h -1 NC). The effect of several operating variables such as oxygen concentration and NO 2/NO molar ratio in the feed is also discussed.

  5. Conversion of polar and non-polar algae oil lipids to fatty acid methyl esters with solid acid catalysts - A model compound study.

    PubMed

    Asikainen, Martta; Munter, Tony; Linnekoski, Juha

    2015-09-01

    Bio-based fuels are becoming more and more important due to the depleting fossil resources. The production of biodiesel from algae oil is challenging compared to terrestrial vegetable oils, as algae oil consists of polar fatty acids, such as phospholipids and glycolipids, as well as non-polar triglycerides and free fatty acids common in vegetable oils. It is shown that a single sulphonated solid acid catalyst can perform the esterification and transesterification reactions of both polar and non-polar lipids. In mild reaction conditions (60-70°C) Nafion NR50 catalyst produces methyl palmitate (FAME) from the palmitic acid derivatives of di-, and tri-glyceride, free fatty acid, and phospholipid with over 80% yields, with the glycolipid derivative giving nearly 40% yields of FAME. These results demonstrate how the polar and non-polar lipid derivatives of algal oil can be utilised as feedstocks for biodiesel production with a single catalyst in one reaction step. PMID:26004380

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

    SciTech Connect

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

    2007-07-03

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

  7. Promoting effect of vanadium ions on the anodic Pd\\/C catalyst for direct formic acid fuel cell application

    Microsoft Academic Search

    Junjie Ge; Xiumei Chen; Changpeng Liu; Tianhong Lu; Jianhui Liao; Liang Liang; Wei Xing

    2010-01-01

    In order to improve the catalytic activity and stability of the anodic Pd catalyst for a direct formic acid fuel cell, vanadium ions in very low concentration were introduced to the electrolyte. It was discovered that the electrooxidation of formic acid could be promoted greatly by addition of trace amount of vanadium ions. A much greater enhancement in catalytic stability

  8. Sulfated Carbon Quantum Dots as Efficient Visible-Light Switchable Acid Catalysts for Room-Temperature Ring-Opening Reactions.

    PubMed

    Li, Haitao; Sun, Chenghua; Ali, Muataz; Zhou, Fengling; Zhang, Xinyi; MacFarlane, Douglas R

    2015-07-13

    Acid catalytic processes play a classic and important role in modern organic synthesis. How well the acid can be controlled often plays the key role in the controllable synthesis of the products with high conversion yield and selectivity. The preparation of a novel, photo-switchable solid-acid catalyst based on carbon quantum dots is described. The carbon quantum dots are decorated with small amounts of hydrogensulfate groups and thus exhibit a photogenerated acidity that produces a highly efficient acid catalysis of the ring opening of epoxides with methanol and other primary alcohols. This reversible, light-switchable acidity is shown to be due to photoexcitation and charge separation in the carbon quantum dots, which create an electron withdrawing effect from the acidic groups. The catalyst is easily separated by filtration, and we demonstrate multiple cycles of its recovery and reuse. PMID:26032183

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

    SciTech Connect

    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

    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.

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

    SciTech Connect

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

    1996-10-01

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

  11. The drastic effect of platinum on carbon-supported ruthenium-tin catalysts used for hydrogenation reactions of carboxylic acids

    Microsoft Academic Search

    Yoshinori Hara; Kouetsu Endou

    2003-01-01

    The incorporation of platinum on bimetallic ruthenium-tin catalysts supported on active carbon has profound effects on the catalytic behavior. The reaction rate was accelerated nearly three times compared with that of the bimetallic system for the hydrogenation of 1,4-cyclohexanedicarboxylic acid (CHDA). Moreover, it turned out that Pt can completely prevent Sn, one component of the catalyst, from dissolving into the

  12. PdCo supported on multiwalled carbon nanotubes as an anode catalyst in a microfluidic formic acid fuel cell

    Microsoft Academic Search

    D. Morales-Acosta; M. D. Morales-Acosta; L. A. Godinez; L. Álvarez-Contreras; S. M. Duron-Torres; J. Ledesma-García; L. G. Arriaga

    2011-01-01

    This work reports the synthesis of Pd-based alloys of Co and their evaluation as anode materials in a microfluidic formic acid fuel cell (?FAFC). The catalysts were prepared using the impregnation method followed by thermal treatment. The synthesized catalysts contain 22wt.% Pd on multiwalled carbon nanotubes (Pd\\/MWCNT) and its alloys with two Co atomic percent in the sample with 4

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

    Microsoft Academic Search

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

    2009-01-01

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

  14. Electrooxidation of methanol on mixed catalysts based on platinum and organic metal complexes in acidic media

    Microsoft Academic Search

    Tatsuhiro Okada; Naoko Arimura; Chisato Ono; Makoto Yuasa

    2005-01-01

    New electro-catalysts were developed based on platinum and organic metal complexes for methanol oxidation reaction (MOR) in acidic media. As complexes nitrogen containing ligands such as N,N?-bis(salicylidene)ethylenediamine (salen), N,N?-bis(salicylidene)phenylenediamine (salophen), N,N?-mono-8-quinolyl-o-phenylenediamine (mqph) and N,N?-bis(anthranilidene)ethylenediamine (anthen), coordinated to V, Mn, Fe, Co, Ni, Cu, Mo, Pd and Sn were synthesized and tested. Mixture of platinum tetraammine complex with one of the

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

    PubMed

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

    2013-03-13

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

  16. Modification of phosphomolybdic acid and its compounds. Catalysts for the selective oxidation of methylacrolein to methacrylic acid. II. Systems modified by ammonium, vanadium, and zinc ions

    Microsoft Academic Search

    I. N. Staroverova; M. Yu. Kutyrev; B. V. Rozentuller

    1986-01-01

    X-ray diffraction and IR and ESR spectroscopy were used to study the structure of modified oxide catalysts for the selective oxidation of methylacrolein containing molybdenum, phosphorus, ammonium, vanadium, and zinc ions. (NHâ)PMoââOâânHâO is formed after roasting at 320degreeC upon using phosphomolybdic acid and ammonium carbonate or ammonium paramolybdate and ammonium phosphate. The introduction of vanadium and zinc during catalyst preparation

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

    PubMed

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

    2014-10-01

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

  18. An effective Pd-Ni(2)P/C anode catalyst for direct formic acid fuel cells.

    PubMed

    Chang, Jinfa; Feng, Ligang; Liu, Changpeng; Xing, Wei; Hu, Xile

    2014-01-01

    The direct formic acid fuel cell is an emerging energy conversion device for which palladium is considered as the state-of-the-art anode catalyst. In this communication, we show that the activity and stability of palladium for formic acid oxidation can be significantly enhanced using nickel phosphide (Ni(2)P) nanoparticles as a cocatalyst. X-ray photoelectron spectroscopy (XPS) reveals a strong electronic interaction between Ni(2)P and Pd. A direct formic acid fuel cell incorporating the best Pd–Ni(2)P anode catalyst exhibits a power density of 550 mWcm(-2), which is 3.5 times of that of an analogous device using a commercial Pd anode catalyst. PMID:24511636

  19. Biomass into chemicals: aerobic oxidation of 5-hydroxymethyl-2-furfural into 2,5-furandicarboxylic acid with gold nanoparticle catalysts.

    PubMed

    Casanova, Onofre; Iborra, Sara; Corma, Avelino

    2009-01-01

    5-hydroxymethyl-2-furfural is selectively converted into 2,5-furandicarboxylic acid (99 mol % yield) in water, under mild conditions (65-130 degrees C, 10 bar air) with gold nanoparticles supported on nanoparticulate ceria (Au-CeO(2)) and on titania (Au-TiO(2)); the former being more active and selective. A reaction mechanism is established and the rate-limiting step of the reaction is the alcohol oxidation of 5-hydroxymethyl-2-furancarboxylic acid into 2,5-furandicarboxylic acid. The effects of pressure, temperature, substrate-to-catalyst ratio, and amount of base are studied to find the most suitable reaction conditions. The absence of metal leaching is verified by chemical analysis of the reaction solution and by confirming that the reaction does not occur after catalyst removal by filtration in hot water. Substrate degradation is strongly diminished and the catalyst life increased by performing the reaction in two temperature steps. PMID:19760702

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

    PubMed

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

    2013-11-01

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

  1. The active component of vanadium-molybdenum catalysts for the oxidation of acrolein to acrylic acid

    SciTech Connect

    Andrushkevich, T.V.; Kuznetsova, T.G.

    1986-12-01

    The catalytic properties of the vanadium-molybdenum oxide system were investigated in the oxidation of acrolein to acrylic acid. The active component of the catalyst is the compound VMo/sub 3/O/sub 11/, the maximum amount of which is observed at a content of 7-15 mole% V/sub 2/O/sub 4/. The compound VMo/sub 3/O/sub 11/ is formed in the thermodecomposition of silicomolybdovanadium heteropoly acids or isopoly compounds, reduced with respect to vanadium, and contains V/sup 4 +/ and Mo/sup 6 +/. The optimum treatment for the formation of this compound is treatment in the reaction mixture at 400 degrees C.

  2. Iron type catalysts for the ozonation of oxalic acid in water.

    PubMed

    Beltrán, Fernando J; Rivas, Francisco J; Montero-de-Espinosa, R

    2005-09-01

    Two iron catalysts (Fe(III) and Fe2O3/Al2O3) have been used in the ozonation of oxalic acid in water at pH 2.5. Percentage removals of oxalic acid were 1.8%, 7% and 30% corresponding to the non-catalytic, homogeneous (Fe(III)) and heterogeneous (Fe2O3/Al2O3) catalytic ozonations, respectively. Catalytic oxalic acid ozonation leads in all cases to total mineralization. The mechanism of ozonation likely develops through formation of iron-oxalate complexes that further react with ozone without the participation of hydroxyl radicals. Because of the stringent acidic conditions, some metal leaching has been observed and quantified in the heterogeneous process. In the homogeneous catalysis, the kinetics was found to be first order with respect to ozone and oxalic acid while for the heterogeneous catalysis, the kinetic order depends on the concentration of ozone in the gas fed. Thus, at ozone concentrations lower than 30 mg L(-1), the heterogeneous ozonation is between first and zero order with respect to both ozone and oxalic acid while at higher ozone gas concentrations, the kinetics was found to be first and zero order with respect to oxalic acid and ozone, respectively. This kinetics is supported through an Eley-Rideal mechanism that involves a surface reaction between non-adsorbed ozone and adsorbed oxalic acid. Apparent activation energies of the homogeneous and heterogeneous catalytic ozonations were found to be 18.2 and 13.6 kcal mol(-1), respectively. PMID:16095660

  3. 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)

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

    2014-10-01

    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.

  4. 40 CFR 75.3 - General Acid Rain Program provisions.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...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,...

  5. 40 CFR 75.3 - General Acid Rain Program provisions.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...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,...

  6. 40 CFR 75.3 - General Acid Rain Program provisions.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...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,...

  7. 40 CFR 75.3 - General Acid Rain Program provisions.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...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,...

  8. 40 CFR 75.3 - General Acid Rain Program provisions.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...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,...

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

    SciTech Connect

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

    2007-06-01

    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.

  10. Preparation and characterization of a composite hydrogel with graphene oxide as an acid catalyst.

    PubMed

    Jiang, Ting; Sui, Zhu-Yin; Yang, Quan-Sheng; Zhang, Xuetong; Han, Bao-Hang

    2015-04-28

    In this study, a facile method for synthesizing a novel graphene oxide/pyrrole-formaldehyde (GOP-1) composite hydrogel was developed via in situ polymerization of pyrrole and formaldehyde in the presence of graphene oxide sheets without any additional catalyst. During the polymerization, graphene oxide can act as a two-dimensional template to regulate the aggregation state of polymer and as an acid catalyst to accelerate the reaction rate of pyrrole and formaldehyde. The morphology and microstructure were investigated by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction, respectively. The chemical properties were analyzed via X-ray photoelectron spectroscopy, infrared spectroscopy, and Raman spectroscopy. The freeze-dried GOP-1 composite hydrogel exhibited a large specific surface area, high nitrogen content, and three-dimensional network structure. Based on the above features, the freeze-dried GOP-1 composite hydrogel used as a gas adsorbent showed a high carbon dioxide uptake capacity at 1.0 bar and 273 K (11.1 wt%), in sharp contrast to that of graphene oxide (7.4 wt%). Furthermore, the as-prepared composite hydrogel may possess attractive potential in the fields of electrode material, tissue engineering, and water treatment. PMID:25760407

  11. Gas chromatographic analysis of free fatty acids and glycerides of milk fat using tetramethylammonium hydroxide as catalyste

    Microsoft Academic Search

    I. Martínez-Castro; L. Alonso; M. Juárez

    1986-01-01

    Summary  Tetramethylammonium hydroxide in methanol has been proposed as a catalyst for preparing methyl esters of both free fatty acids and glycerides of fats. Nevertheless, procedures normally recognized as suitable can be inadequate when the fat under study contains noticeable amounts of low relative molecular mass esters. The method using tetramethylammonium hydroxide has been examined and modified in order to analyze

  12. Passive micro tubular direct formic acid fuel cells (DFAFCs) with chemically assembled Pd anode nano-catalysts on polymer electrolytes

    Microsoft Academic Search

    H. Qiao; H. Shiroishi; T. Okada

    2007-01-01

    Wet-chemical assembling process has been developed for the formation of the anode electrocatalyst layers of a micro tubular direct formic acid fuel cell. By using this method, a porous layer of Pd nano-catalyst was bonded onto the inner surface of a tubular polymer electrolyte membrane by chemical reduction of Pd complex impregnated in the membrane. The performance characteristics as a

  13. Addition reactions of thiophenol to ?,?-unsaturated carbonyl compounds using organic acid radical basic anion-exchange resins as catalysts

    Microsoft Academic Search

    Mingxia Li; Jinxia Huang; Wanxuan Zhang

    2001-01-01

    A series of organic acid radical basic anion-exchange resins were prepared from strongly basic quarternary ammonium I type anion-exchange resins, using as the catalysts in addition reactions of thiophenol to ?,?-unsaturated carbonyl compounds. The catalytic activity are influenced by exchange capacity, reaction temperature, solvent and molecular structure.

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

    Microsoft Academic Search

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

    2003-01-01

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

  15. Enhanced electrochemical oxidation of Acid Red 3R wastewater with iron phosphomolybdate supported catalyst.

    PubMed

    Wang, Li; Yue, Lin; Shi, Feng; Guo, Jianbo; Yang, Jingliang; Lian, Jing; Luo, Xiao; Guo, Yankai

    2015-01-01

    Electrochemical oxidation of Acid Red 3R (AR3R) was investigated with the new catalyst of iron phosphomolybdate (FePMo12) supported on modified molecular sieves type 4 Å (4A) as packing materials in the reactor. The results of the Fourier transform infrared spectroscopy and X-ray diffraction indicated that the heteropolyanion had a Keggin structure. The optimal conditions for decolorization of simulated AR3R wastewater were as follows: current density 35 mA/cm(2), initial pH 4.0, airflow 0.08 m(3)/hour and inter-electrode distance 3.0 cm. With the addition of NaCl to the system, the decolorization efficiency increased. But Na2SO4 had a negative effect on the decolorization efficiency, which was attributed to the negative salt effect. The degradation mechanisms of AR3R were also discussed in detail. PMID:25812093

  16. An in situ Fourier transform infrared study of formic acid adsorption on a polycrystalline silver catalyst

    SciTech Connect

    Millar, G.J.; Metson, J.B.; Bowmaker, G.A.; Cooney, R.P. (Univ. of Auckland (New Zealand))

    1994-06-01

    Infrared spectra are reported for the adsorption of formic acid on a polycrystalline silver catalyst after various degrees of oxidation. Three distinct chemisorbed species were identified, two of which corresponded to adsorbed formate on Ag(110) and Ag(111) crystal planes and the other to adsorbed formate on a silver site modified by the presence of subsurface oxygen. Moreover, it was discovered that subsurface oxygen species were primarily located in the vicinity of grain boundary defects. Desorption profiles suggested that coadsorbed oxygen moieties could destabilize chemisorbed formate. Because of the invariance in infrared band positions associated with formate species, regardless of whether or not neighbouring atomic oxygen species were present, a kinetic stabilization mechanism is proposed. The pivotal role of subsurface oxygen species (found in the region of grain boundaries) in the mechanism for the selective oxidation of methanol to formaldehyde is discussed. 59 refs., 13 figs.

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

    PubMed

    Díaz, L; Borges, M E

    2012-08-15

    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

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

    Microsoft Academic Search

    Walsh

    1987-01-01

    Cathode improvement, both in performance and cost, available through the use of a class of organometallic cathode catalysts, the tetraazaannulenes (TAAs), was investigated. A new mixed catalyst was identified which provides improved cathode performance without the need for the use of a noble metal. This mixed catalyst was tested under load for 1000 h in full cell at 160 to

  19. Effect of Nafion ionomer and catalyst in cathode layers for the direct formic acid fuel cell with complex capacitance analysis on the ionic resistance

    Microsoft Academic Search

    Sunhyung Kim; Jonghee Han; Yongchai Kwon; Kug-Seung Lee; Tae-Hoon Lim; Suk Woo Nam; Jong Hyun Jang

    2011-01-01

    Using platinum (Pt) black and carbon-supported Pt (Pt\\/C) as cathode catalysts, membrane-electrode assemblies (MEAs) were fabricated with various Nafion ionomer content, and their direct formic acid fuel cell (DFAFC) performances were investigated. In MEAs incorporating Pt black catalysts, the current density at 0.6V was highest at ionomer\\/catalyst volume ratio of 1.0, which was consistent with the electrochemical active area (EAS)

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

    SciTech Connect

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

    1993-01-01

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

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

    PubMed Central

    2010-01-01

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

  2. Folic acid in general medicine and dermatology.

    PubMed

    Gisondi, Paolo; Fantuzzi, Francesca; Malerba, Mario; Girolomoni, Giampiero

    2007-01-01

    Folic acid is a vitamin B essential for the integrity and function of DNA. Relative deficiency of folic acid may occur in conditions such as pregnancy and hyperproliferative or chronic inflammatory disorders. Folic acid supplementation has been proven to be beneficial in the prevention of neural tube defects and in limiting methotrexate side effects, and may reduce the risk of colorectal cancer. Folate is a critical vitamin in determining plasma homocysteine levels, which in turn is a major risk factor for cardiovascular diseases. The results of large clinical trials with dietary supplementation of folic acid, vitamin B12 and vitamin B6 have shown that this homocysteine-lowering therapy is effective in the secondary prevention of non-fatal strokes, but had no effect in the prevention of fatal cardiovascular diseases. Hyperhomocysteinemia has also been reported in age-related neurological conditions with cognitive impairment (e.g. dementia), and psychiatric disorders such as depression. Elevated homocysteine levels are frequent in patients with chronic immune-mediated disorders including rheumatoid arthritis, systemic lupus erythematosus, chronic plaque psoriasis and psoriatic arthritis, which have in common a tendency to an accelerated atherosclerosis leading to increased deaths from cardiovascular events. Folic acid supplementation appears as a reasonable therapeutic option in patients affected by chronic inflammatory skin diseases, such as moderate to severe psoriasis; in particular, those with concomitant hyperhomocysteinemia, low plasma folate and additional cardiovascular risk factors. PMID:17538801

  3. Bimetallic Bi–Pt, Ru–Pt and Ru–Pd and trimetallic catalysts for the selective oxidation of glyoxal into glyoxalic acid in aqueous phase

    Microsoft Academic Search

    Aurore Deffernez; Sophie Hermans; Michel Devillers

    2005-01-01

    Various bi- and trimetallic associations have been tested as catalysts for the selective oxidation of glyoxal into glyoxalic acid in aqueous phase. All catalysts were supported on carbon and consisted of a noble metal (Pd or Pt) in association with a second (or third) metal acting as promoter (Ru or Bi). Out of all the possible combinations, some families of

  4. PEG-SO3H as Soluble Acidic Polymeric Catalyst for Regioselective Ring Opening of Epoxides: A High-Efficient Synthetic Approach to ?-Hydroxy Thiocyanates

    Microsoft Academic Search

    Ali Reza Kiasat; Mehdi Fallah Mehrjardi

    2008-01-01

    Poly(ethylene glycol)–bound sulfonic acid, PEG-SO3H, was developed as an environmentally friendly and efficient homogeneous polymeric catalyst in organic synthesis. This polymeric phase-transfer catalyst catalyzed the regioselective ring opening of epoxides by thiocyanate ion to give thiocyanohydrins as key intermediates in agricultural and pharmaceutical chemistry in high yields.

  5. 5790 J. Am. Chem. SOC.1987, 109, 5790-5800 Concerted General Base and Bifunctional General Acid

    E-print Network

    Cox, Michael M.

    5790 J. Am. Chem. SOC.1987, 109, 5790-5800 Concerted General Base and Bifunctional General Acid with pyrazole is catalyzed by general bases and by bifunctional general acids. The Br~lnstedplot for general of a significant lifetime for T'. Catalysis is observed with buffer acids when the acid is bifunctional. The rate

  6. Modification of phosphomolybdic acid and its compounds. Catalysts for the selective oxidation of methylacrolein to methacrylic acid. II. Systems modified by ammonium, vanadium, and zinc ions

    SciTech Connect

    Staroverova, I.N.; Kutyrev, M.Yu.; Rozentuller, B.V.

    1986-12-01

    X-ray diffraction and IR and ESR spectroscopy were used to study the structure of modified oxide catalysts for the selective oxidation of methylacrolein containing molybdenum, phosphorus, ammonium, vanadium, and zinc ions. (NH/sub 4/)PMo/sub 12/O/sub 40/nH/sub 2/O is formed after roasting at 320degreeC upon using phosphomolybdic acid and ammonium carbonate or ammonium paramolybdate and ammonium phosphate. The introduction of vanadium and zinc during catalyst preparation in the former case does not lead to the formation of new compounds and the activity of the starting system increases slightly. In the latter method, it becomes possible to activate the catalyst due to the formation, on one hand, of a two-phase system and, on the other, by insertion of vanadium ions into the heteropoly anion structure.

  7. New entries in Lewis acid-Lewis base bifunctional asymmetric catalyst: catalytic enantioselective Reissert reaction of pyridine derivatives.

    PubMed

    Ichikawa, Eiko; Suzuki, Masato; Yabu, Kazuo; Albert, Matthias; Kanai, Motomu; Shibasaki, Masakatsu

    2004-09-29

    The first catalytic enantioselective Reissert reaction of pyridine derivatives that affords products with excellent regio- and enantioselectivity is described. The key for success is the development of new Lewis acid-Lewis base bifunctional asymmetric catalysts containing an aluminum as a Lewis acid and sulfoxides or phosphine sulfides as a Lewis base. These reactions are useful for the synthesis of a variety of chiral piperidine subunits, and catalytic enantioselective formal synthesis of CP-293,019, a selective D4 receptor antagonist, was achieved. Preliminary mechanistic studies indicated that both sulfoxides and phosphine sulfides can activate TMSCN as a Lewis base. In addition, the sulfoxides with appropriate stereochemistry might stabilize a highly enantioselective bimetallic complex (a presumed active catalyst) through internal coordination to aluminum. PMID:15382912

  8. Attrition resistance and catalytic performance of spray-dried SAPO-34 catalyst for MTO process: Effect of catalyst phase and acidic solution

    Microsoft Academic Search

    Min Kim; Ho-Jeong Chae; Tae-Wan Kim; Kwang-Eun Jeong; Chul-Ung Kim; Soon-Yong Jeong

    2011-01-01

    SAPO-34 is the most well-known catalyst for MTO (methanol to olefins) reaction because of its good selectivity to light olefins. However, SAPO-34 catalyst is rapidly deactivated by coke, and thus it should be used in circulating fluidized bed (CFB) reactors so that the deactivated catalyst can be continuously regenerated. To apply a catalyst into a CFB reactor, strong mechanical strength

  9. Model Reaction for the in-Situ Characterization of the Hydrogenating and Acid Properties of Industrial Hydrocracking Catalysts

    Microsoft Academic Search

    M. Guisnet; C. Thomazeau; J. L. Lemberton; S. Mignard

    1995-01-01

    A kinetic study of o-xylene transformation was carried out on a sulfided NiMo on Y zeolite catalyst during the hydrocracking of a model compound (n-heptane) under the following conditions of the process: high hydrogen pressure (5.7 MPa), presence of nitrogen and sulfur-containing compounds. o-Xylene inhibits n-heptane transformation, which can be explained by a competition for the adsorption on the acid

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

    Microsoft Academic Search

    Tommy T. Cheng; El?d L. Gyenge

    2009-01-01

    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

  11. Hollow core\\/mesoporous shell carbon as a highly efficient catalyst support in direct formic acid fuel cell

    Microsoft Academic Search

    Baizeng Fang; Minsik Kim; Jong-Sung Yu

    2008-01-01

    Spherical carbon capsules with a hollow macroporous core of ca. 260nm and a ca. 40nm thick mesoporous shell were explored for the first time as an anode catalyst support in direct formic acid fuel cell (DFAFC). Hollow core\\/mesoporous shell carbon (HCMSC) possesses fantastic structural characteristics such as uniform particle size, well-developed three-dimensionally interconnected bimodal porosity, and large specific surface area

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

    Microsoft Academic Search

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

    2004-01-01

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

  13. Acid zeolites as catalysts in organic reactions. Friedel-Crafts reaction of 2-alkylfurans with 3-substituted allylic alcohols

    Microsoft Academic Search

    Felipe Algarra; Avelino Corma; Hermenegildo García; Jaime Primo

    1995-01-01

    Methyl 3-(2-furyl) propanoate (1) and 3-(2-furyl) propyl acetate (3) can be conveniently alkylated with high conversion and selectivity by cinnamyl and crotyl alcohols in the liquid phase at moderate temperatures using acid zeolites of medium and large pore size as heterogeneous catalysts. ZSM-5 zeolite exhibited the highest turnover number for the heteroaromatic alkylation. This reaction was found to be totally

  14. Effects of Pt\\/C, Pd\\/C and PdPt\\/C anode catalysts on the performance and stability of air breathing direct formic acid fuel cells

    Microsoft Academic Search

    Ping Hong; Fan Luo; Shijun Liao; Jianhuang Zeng

    2011-01-01

    Pt\\/C, Pd\\/C and PdPt\\/C catalysts are potential anodic candidates for electro-oxidation of formic acid. In this work we designed a miniature air breathing direct formic acid fuel cell, in which gold plated printed circuit boards are used as end plates and current collectors, and evaluated the effects of anode catalysts on open circuit voltage, power density and long-term discharging stability

  15. Deactivation\\/reactivation of a Pd\\/C catalyst in a direct formic acid fuel cell (DFAFC): Use of array membrane electrode assemblies

    Microsoft Academic Search

    Xingwen Yu; Peter G. Pickup

    2009-01-01

    Palladium-based catalysts exhibit high activity for formic acid oxidation, but their catalytic activity decreases quite rapidly under direct formic acid fuel cell (DFAFC) operating conditions. This paper presents a systematic study of the deactivation and electrochemical reactivation of a carbon supported palladium catalyst (Pd\\/C) employing anode arrays in a DFAFC. Deactivation of Pd\\/C is caused by the electro-oxidation of the

  16. Hydrothermal microwave valorization of eucalyptus using acidic ionic liquid as catalyst toward a green biorefinery scenario.

    PubMed

    Xu, Ji-Kun; Chen, Jing-Huan; Sun, Run-Cang

    2015-10-01

    The application of the acidic ionic liquid (IL), 1-butyl-3-methylimidazolium hydrogensulfate ([bmim]HSO4), as a catalyst in the hydrothermal microwave treatment (HMT) and green upgradation of eucalyptus biomass has been investigated. The process was carried out in a microwave reactor system at different temperatures (140-200°C) and evaluated for severities. The xylooligosaccharides (XOS, refers to a DP of 2-6) yield up to 5.04% (w/w) of the initial biomass and 26.72% (w/w) of xylan were achieved. Higher temperature resulted in lower molecular weight product, and enhanced the concentration of monosaccharides and byproducts. The morphology and structure of the solid residues were performed using an array of techniques, such as SEM, XRD, FTIR, BET surface area, and CP/MAS (13)C NMR, by which the increase of crystallinity, the destruction of surface structure, and the changes in functional groups and compositions were studied after the pretreatment, thus significantly enhancing the enzymatic hydrolysis. PMID:26119053

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    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.

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

    SciTech Connect

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

    2011-02-04

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

  19. Hydrogenation of Succinic Acid to ?-Butyrolactone (GBL) Over Palladium-Alumina Composite Catalyst Prepared by a Single-Step Sol–Gel Method

    Microsoft Academic Search

    Ung Gi Hong; Joongwon Lee; Sunhwan Hwang; In Kyu Song

    2011-01-01

    \\u000a Abstract  Mesoporous palladium-alumina (Pd-A) composite catalysts prepared by a single-step sol–gel method were calcined at various\\u000a temperatures to control palladium surface area and acidity. The Pd-A catalysts were characterized by XRD, BET, N2 adsorption–desorption isotherm, H2 chemisorption, 27Al MAS NMR, NH3-TPD, and HR-TEM analyses. Liquid-phase hydrogenation of succinic acid to ?-butyrolactone (GBL) was carried out over Pd-A\\u000a catalyst in a batch

  20. Suitable catalysts for hydroisomerization of long-chain normal paraffins

    Microsoft Academic Search

    H. Deldari

    2005-01-01

    Nowadays, isomerization of normal paraffins plays an important role in the petroleum industry. Isomerization reactions generally take place over bifunctional metal\\/acid catalysts. The suitable catalysts for hydroisomerization of long chain n-paraffins are reviewed in this paper. An ideal catalyst for this purpose should provide a high yield of isomerization and should have shape-selectivity to react only with n-paraffins. To achieve

  1. A general route to hollow mesoporous rare-earth silicate nanospheres as a catalyst support.

    PubMed

    Jin, Renxi; Yang, Yang; Zou, Yongcun; Liu, Xianchun; Xing, Yan

    2014-02-17

    Hollow mesoporous structures have recently aroused intense research interest owing to their unique structural features. Herein, an effective and precisely controlled synthesis of hollow rare-earth silicate spheres with mesoporous shells is reported for the first time, produced by a simple hydrothermal method, using silica spheres as the silica precursors. The as-prepared hollow rare-earth silicate spheres have large specific surface area, high pore volume, and controllable structure parameters. The results demonstrate that the selection of the chelating reagent plays critical roles in forming the hollow mesoporous structures. In addition, a simple and low-energy-consuming approach to synthesize highly stable and dispersive gold nanoparticle-yttrium silicate (AuNPs/YSiO) hollow nanocomposites has also been developed. The reduction of 4-nitrophenol with AuNPs/YSiO hollow nanocomposites as the catalyst has clearly demonstrated that the hollow rare-earth silicate spheres are good carriers for Au nanoparticles. This strategy can be extended as a general approach to prepare multifunctional yolk-shell structures with diverse compositions and morphologies simply by replacing silica spheres with silica-coated nanocomposites. PMID:24449457

  2. Codeposited PtSb\\/C catalysts for direct formic acid fuel cells

    Microsoft Academic Search

    Xingwen Yu; Peter G. Pickup

    2011-01-01

    Carbon supported PtSb catalysts were synthesized by codeposition of platinum and antimony on Vulcan® carbon black. X-ray diffraction (XRD) analysis revealed that the Sb was alloyed with the Pt while XPS indicated that a large fraction of the Sb was in an oxidized state, with only partial alloying. The performances of catalysts with a range of compositions were compared in

  3. Transesterification of triacetin with methanol on solid acid and base catalysts

    Microsoft Academic Search

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

    2005-01-01

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

  4. Further work on sodium montmorillonite as catalyst for the polymerization of activated amino acids

    NASA Technical Reports Server (NTRS)

    Eirich, F. R.; Paecht-Horowitz, M.

    1986-01-01

    When the polycondensation of amino acid acylates was catalyzed with Na-montmorillonite, the polypeptides were consistently found to exhibit a distribution of discrete molecular weights, for as yet undiscovered reasons. One possible explanation was connected to the stepwise mode of monomer addition. New experiments have eliminated this possibility, so that there is the general assumption that this discreteness is the result of a preference of shorter oligomers to add to others of the same length, a feature that could be attributed to some structure of the platelet aggregates of the montmorillonite. The production of optical stereoisomers is anticipated when D,L-amino acids are polymerized on montmorillonite. Having used an optically active surface, the essence of the results lies not only in the occurrence of optically active oligomers and polymers, but also in the fact that the latter exhibit the same molecular weight characteristics as the D,L-polymers. Preparatory to work contemplated on a parallel synthesis of amino acid and nucleotide oligomers, studies were continued on the co-adsorption of amino acids, nucleotides, and amino acid-nucleotides on montmorillonite.

  5. 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)

    Jiang, Rongzhong; Chu, Deryn

    2014-01-01

    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.

  6. Nanostructured Pt\\/C and Pd\\/C catalysts for direct formic acid fuel cells

    Microsoft Academic Search

    Zhaolin Liu; Liang Hong; Mun Pun Tham; Tze Han Lim; Huixin Jiang

    2006-01-01

    Platinum (Pt) and palladium (Pd) nanoparticles supported on Vulcan XC-72 carbon are prepared by a microwave-assisted polyol process. The catalysts are characterized by transmission electron microscopy and X-ray diffraction analysis. The average particle size of Pt and Pd nanoparticles, which are uniformly dispersed on carbon, is 4 and 5nm, respectively. The Pt\\/C and Pd\\/C catalysts exhibit four diffraction peaks that

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

    NASA Astrophysics Data System (ADS)

    Golobostanfard, Mohammad Reza; Abdizadeh, Hossein

    2013-03-01

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

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

    SciTech Connect

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

    2011-10-18

    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.

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

    PubMed

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

    2011-02-01

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

  10. Benzene selectivity in competitive arene hydrogenation: effects of single-site catalyst···acidic oxide surface binding geometry.

    PubMed

    Gu, Weixing; Stalzer, Madelyn Marie; Nicholas, Christopher P; Bhattacharyya, Alak; Motta, Alessandro; Gallagher, James R; Zhang, Guanghui; Miller, Jeffrey T; Kobayashi, Takeshi; Pruski, Marek; Delferro, Massimiliano; Marks, Tobin J

    2015-06-01

    Organozirconium complexes are chemisorbed on Brønsted acidic sulfated ZrO2 (ZrS), sulfated Al2O3 (AlS), and ZrO2-WO3 (ZrW). Under mild conditions (25 °C, 1 atm H2), the supported Cp*ZrMe3, Cp*ZrBz3, and Cp*ZrPh3 catalysts are very active for benzene hydrogenation with activities declining with decreasing acidity, ZrS ? AlS ? ZrW, arguing that more Brønsted acidic oxides (those having weaker corresponding conjugate bases) yield stronger surface organometallic electrophiles and for this reason have higher benzene hydrogenation activity. Benzene selective hydrogenation, a potential approach for carcinogenic benzene removal from gasoline, is probed using benzene/toluene mixtures, and selectivities for benzene hydrogenation vary with catalyst as ZrBz3(+)/ZrS(-), 83% > Cp*ZrMe2(+)/ZrS(-), 80% > Cp*ZrBz2(+)/ZrS(-), 67% > Cp*ZrPh2(+)/ZrS(-), 57%. For Cp*ZrBz2(+)/ZrS(-), which displays the highest benzene hydrogenation activity with moderate selectivity in benzene/toluene mixtures. Other benzene/arene mixtures are examined, and benzene selectivities vary with arene as mesitylene, 99%, > ethylbenzene, 86% > toluene, 67%. Structural and computational studies by solid-state NMR spectroscopy, XAS, and periodic DFT methods applied to supported Cp*ZrMe3 and Cp*ZrBz3 indicate that larger Zr···surface distances are present in more sterically encumbered Cp*ZrBz2(+)/AlS(-) vs Cp*ZrMe2(+)/AlS(-). The combined XAS, solid state NMR, and DFT data argue that the bulky catalyst benzyl groups expand the "cationic" metal center-anionic sulfated oxide surface distances, and this separation/weakened ion-pairing enables the activation/insertion of more sterically encumbered arenes and influences hydrogenation rates and selectivity patterns. PMID:25884397

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

    NASA Astrophysics Data System (ADS)

    Mohammad, Mujahid; Nishimura, Shun; Ebitani, Kohki

    2015-02-01

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

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

    PubMed

    Murahashi, Shun-Ichi

    2011-01-01

    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. (Communicated by Ryoji Noyori, M.J.A.). PMID:21558760

  13. A mixed NCP pincer palladacycle as catalyst precursor for the coupling of aryl halides with aryl boronic acids

    Microsoft Academic Search

    Gilber R. Rosa; Clarissa H. Rosa; Frank Rominger; Jairton Dupont; Adriano L. Monteiro

    2006-01-01

    The reaction of phosphinite Me2NCH2CC(CH2)2OP(i-Pr)2 (2) with Li2PdCl4 in methanol at room temperature affords the air and water stable mixed pincer palladacycle (Me2NCH2(Cl)CC(CH2)2OP(i-Pr)2-?N?C?P)PdCl (3) whose structure has been ascertained by means of an X-ray diffraction study. This pincer palladacycle is a highly efficient catalyst precursor for the coupling of aryl boronic acids and aryl chlorides. Both electron-rich and -poor aryl

  14. Synthesis of carbon supported palladium nanoparticles catalyst using a facile homogeneous precipitation-reduction reaction method for formic acid electrooxidation

    NASA Astrophysics Data System (ADS)

    Ma, Juan; Ji, Yigang; Sun, Hanjun; Chen, Yu; Tang, Yawen; Lu, Tianhong; Zheng, Junwei

    2011-10-01

    A highly dispersed and ultrafine carbon supported Pd nanoparticles (Pd/C) catalyst is synthesized by a facile homogeneous precipitation-reduction reaction method. Under the appropriate pH conditions, [PdCl 4] 2- species in PdCl 2 solution are slowly transformed into the insoluble palladium oxide hydrate (PdO·H 2O) precipitation by heat treatment due to a slow hydrolysis reaction, which results in the generation of carbon supported PdO·H 2O nanoparticles (PdO·H 2O/C) sample with the high dispersion and small particle size. Consequently, a highly dispersed and ultrafine Pd/C catalyst can be synthesized by PdO·H 2O ? Pd 0 in situ reduction reaction path in the presence of NaBH 4. As a result, the resulting Pd/C catalyst possesses a significantly electrocatalytic performance for formic acid electrooxidation, which is attributed to the uniformly sized and highly dispersed nanostructure.

  15. Photocatalytic oxidation technology for humic acid removal using a nano-structured TiO2/Fe2O3 catalyst.

    PubMed

    Qiao, S; Sun, D D; Tay, J H; Easton, C

    2003-01-01

    A novel TiO2 coated haematite photocatalyst was prepared and used for removal of colored humic acids from wastewater in an UV bubble photocatalytic reactor. XRD analysis confirmed that nano-size anatase crystals of TiO2 were formed after calcination at 480 degrees C. SEM results revealed that nano-size particles of TiO2 were uniformly coated on the surface of Fe2O3 to form a bulk of nano-structured photocatalyst Fe2O3/TiO2. The porous catalyst had a BET surface area of 168 m2/g. Both the color and total organic carbon (TOC) conversion versus the residence time were measured at various conditions. The effects of pH value, catalyst loaded, initial humic acid concentration and reaction temperature on conversion were monitored. The experimental results proved that the photocatalytic oxidation process was not temperature sensitive and the optimum catalyst loading was found to be 0.4 g/l. Degradation and decolorization of humic acids have higher efficiency in acidic medium and at low initial humic acid concentration. The new catalyst was effective in removing TOC at 61.58% and color400 at 93.25% at 180 minutes illumination time and for 20 mg/l neutral humic acid aqueous solution. The kinetic analysis showed thatthe rate of photocatalytic degradation of humic acids obeyed the first order reaction kinetics. PMID:12578197

  16. A General Model and Solution Algorithm for Cathode Catalyst Layer of PEM Fuel Cells

    Microsoft Academic Search

    N. Khajeh; M. J. Kermani

    A mechanistic model according to the multi domain approach for the cathode catalyst layer (CL) in PEM fuel cells is derived based on Nernst-Plank equation for the flux of species and Faraday's law to relate the flux of charged species to the current density. The rate of the electrochemical reaction is given by the Butler- Volmer equation. Potential drop in

  17. 40 CFR 72.71 - Acceptance of State Acid Rain programs-general.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...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)...

  18. 40 CFR 72.71 - Acceptance of State Acid Rain programs-general.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...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)...

  19. 40 CFR 72.71 - Acceptance of State Acid Rain programs-general.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...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)...

  20. 40 CFR 72.71 - Acceptance of State Acid Rain programs-general.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...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)...

  1. 40 CFR 72.71 - Acceptance of State Acid Rain programs-general.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...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)...

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    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.

  3. Development of acidity on sol-gel prepared TiO{sub 2}-SiO{sub 2} catalysts

    SciTech Connect

    Calvino, J.J.; Cauqui, M.A.; Gatica, J.M.; Perez, J.A.; Rodriguez-Izquierdo, J.M. [Univ. de Cadiz, Puerto Real (Spain)

    1994-12-31

    Three different TiO{sub 2}-SiO{sub 2} gels (Xerogel, Carbogel and Aerogel) are more active acid catalysts than other reference samples used here. As deduced from FTIR, XRD and XANES studies, the structural properties of these gels are quite different to each other, thus revealing the strong influence of the drying treatment. It is found that the degree of Si-O-Ti linking and the surface acidity follows the same trend (X > C > A). The authors conclude that supercritical drying at 600 K and 190 bars can induce Ti leaching followed by redeposition in the narrower pores of the gel. These effects modify both the textural and surface chemical properties of the resulting material.

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

    PubMed Central

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

    2014-01-01

    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

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

    SciTech Connect

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

    2014-06-01

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

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

    PubMed

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

    2013-04-01

    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

  7. Electro-oxidation of methanol on platinum-organic metal complex mixed catalysts in acidic media.

    PubMed

    Okada, T; Suzuki, Y; Hirose, T; Toda, T; Ozawa, T

    2001-12-01

    Novel mixed catalysts systems have been developed using a platinum tetraammine complex with a cobalt or nickel quinolyldiamine complex supported on graphite powder and heart treated at 600 degrees C in argon atmosphere, for the methanol oxidation reaction in direct methanol fuel cells. PMID:12240030

  8. Acidity and catalytic activity of zeolite catalysts bound with silica and alumina 

    E-print Network

    Wu, Xianchun

    2004-09-30

    . Micropore surface area and micropore volume are reduced by about 19% and 18%, respectively, indicating some micropores of ZSM-5 are blocked on binding with silica. SiO2-bound ZSM-5 catalysts have less catalytic activity for butane transformation (cracking...

  9. Heteropoly Acids as Heterogeneous and Reusable Catalyst for ?-Thiocyanation of Ketones

    Microsoft Academic Search

    Atul C. Chaskar; Arun A. Yadav; Bhushan P. Langi; Anita Murugappan; Chetan Shah

    2010-01-01

    Simple, efficient, and mild method for ?-thiocyanation of ketones in presence of heteropolyacid has been developed. This methodology offered ?-oxothiocyanates in good to excellent yields at room temperature in a highly selective manner. The catalyst could be efficiently recovered from the reaction and reused.

  10. The n-butyl amine TPD measurement of Brönsted acidity for solid catalysts by simultaneous TG/DTG-DTA

    NASA Astrophysics Data System (ADS)

    Sasca, V.; Avram, Livia; Verdes, Orsina; Popa, A.

    2010-06-01

    The method for Brönsted acidity measurement based on TPD of alkyl amines desorption by gas-chromatography or thermogravimetry was adapted for simultaneous TG/DTG-DTA analysis. The acidity measurements were focused on the 12-tungstophosphoric acid (H 3PW 12O 40) and its salts, especially with Cesium since these posses the highest Brönsted acidity and they are among the most interesting catalysts. The n-butyl amine (NBA) desorption takes place in three steps for Cs xH 3- xPW 12O 40, x = 0-2, and four steps for the Cs 2.5H 0.5PW 12O 40. The steps of desorption correspond to the release of NBA molecules in stages, as NBA or butene molecules resulted from the Hofmann elimination reaction and NH 3 + H 2O formed by decomposition of ammonium salt. The quantities of desorption products, C 4H 8 and NH 3 + H 2O, corresponding to the stages with the maximum desorption rates at 400-420 °C, respectively 560-600 °C, are in the stoichiometric ratio with the Brönsted acidity.

  11. Synthetic Method for 2,2'-Disubstituted Fluorinated Binaphthyl Derivatives and Application as Chiral Source in Design of Chiral Mono-Phosphoric Acid Catalyst.

    PubMed

    Momiyama, Norie; Okamoto, Hiroshi; Shimizu, Masahiro; Terada, Masahiro

    2015-08-01

    A practical synthetic method for 2,2'-disubstituted fluorinated binaphthyl derivatives was achieved using magnesium bis(2,2,6,6-tetramethylpiperamide) [Mg(TMP)2 ], prepared from LiTMP (2 equiv) and MgBr2 (1 equiv), which allows for access to a variety of fluorinated binaphthyl compounds. The utility of the fluorinated binaphthyl backbone was evaluated in F10 BINOL derived chiral mono-phosphoric acid (R)- as the chiral Brønsted acid catalyst. The catalyst (R)- performs exceptionally well in the catalytic enantioselective imino-ene reaction, demonstrating the potential of a fluorinated binaphthyl framework. Chirality 27:464-475, 2015. © 2015 Wiley Periodicals, Inc. PMID:25665035

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

    PubMed Central

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

    2014-01-01

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

  13. General economic evaluation of the use of quaternary ammonium salts as catalysts in industrial applications

    SciTech Connect

    Zaldman, B.; Neumann, R.; Sasson, Y.

    1985-09-01

    The use of quaternary ammonium salts (Quats) as phase-transfer catalysts is analyzed from a technological and economic point of view. The limiting price for Quats is determined by establishing a qualitative relationship between technical parameters and economic factors. Specific examples show that the present price of Quats limits their commercial use to the area of high-priced commodities and specialty chemicals. Quats may be used i commodity manufacture provided they are produced on a larger scale. A simulation of such a large-scale production of a representative Quat (tetrabutylammonium bromide) has been made and its consequences are discussed.

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

    PubMed

    Diab, Lisa; Gellrich, Urs; Breit, Bernhard

    2013-10-28

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

  15. Synthesis and characterization of triflic acid-functionalized mesoporous Zr-TMS catalysts: heterogenization of CF 3SO 3H over Zr-TMS and its catalytic activity

    Microsoft Academic Search

    M. Chidambaram; D. Curulla-Ferre; A. P. Singh; B. G. Anderson

    2003-01-01

    Triflic acid-functionalized Zr-TMS (zirconium oxide with a mesostructured framework; TMS, transition metal oxide mesoporous molecular sieves) catalysts have been synthesized by functionalizing triflic acid onto the walls of Zr-TMS via post synthesis method. The synthesized materials were characterized by powder XRD, N2-sorption, FT-IR spectroscopy, elemental analysis, solid-state 13C CP and DD\\/MAS NMR spectroscopy, FT-Raman analysis, NH3-TPD, SEM, TEM, TG-DTA, and

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

    Microsoft Academic Search

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

    2002-01-01

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

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

    Microsoft Academic Search

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

    2005-01-01

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

  18. Stable and catalytically active iron porphyrin-based porous organic polymer: Activity as both a redox and Lewis acid catalyst

    PubMed Central

    Oveisi, Ali R.; Zhang, Kainan; Khorramabadi-zad, Ahmad; Farha, Omar K.; Hupp, Joseph T.

    2015-01-01

    A new porphyrin-based porous organic polymer (POP) with BET surface area ranging from 780 to 880?m2/g was synthesized in free-base form via the reaction of meso-tetrakis(pentafluorophenyl) porphyrin and a rigid trigonal building block, hexahydroxytriphenylene. The material was then metallated with Fe(III) imparting activity for Lewis acid catalysis (regioselective methanolysis ring-opening of styrene oxide), oxidative cyclization catalysis (conversion of bis(2-hydroxy-1-naphthyl)methanes to the corresponding spirodienone), and a tandem catalytic processes: an in situ oxidation-cyclic aminal formation-oxidation sequence, which selectively converts benzyl alcohol to 2-phenyl-quinazolin-4(3H)-one. Notably, the catalyst is readily recoverable and reusable, with little loss in catalytic activity. PMID:26177563

  19. Stable and catalytically active iron porphyrin-based porous organic polymer: Activity as both a redox and Lewis acid catalyst.

    PubMed

    Oveisi, Ali R; Zhang, Kainan; Khorramabadi-Zad, Ahmad; Farha, Omar K; Hupp, Joseph T

    2015-01-01

    A new porphyrin-based porous organic polymer (POP) with BET surface area ranging from 780 to 880?m(2)/g was synthesized in free-base form via the reaction of meso-tetrakis(pentafluorophenyl) porphyrin and a rigid trigonal building block, hexahydroxytriphenylene. The material was then metallated with Fe(III) imparting activity for Lewis acid catalysis (regioselective methanolysis ring-opening of styrene oxide), oxidative cyclization catalysis (conversion of bis(2-hydroxy-1-naphthyl)methanes to the corresponding spirodienone), and a tandem catalytic processes: an in situ oxidation-cyclic aminal formation-oxidation sequence, which selectively converts benzyl alcohol to 2-phenyl-quinazolin-4(3H)-one. Notably, the catalyst is readily recoverable and reusable, with little loss in catalytic activity. PMID:26177563

  20. A one-pot method for the selective conversion of hemicellulose from crop waste into C5 sugars and furfural by using solid acid catalysts.

    PubMed

    Sahu, Ramakanta; Dhepe, Paresh Laxmikant

    2012-04-01

    We present a solid-acid catalyzed one-pot method for the selective conversion of solid hemicellulose without its separation from other lignocellulosic components, such as cellulose and lignin. The reactions were carried out in aqueous and biphasic media to yield xylose, arabinose, and furfural. To overcome the drawbacks posed by mineral acid methods in converting hemicelllulose, we used heterogeneous catalysts that work at neutral pH. In a batch reactor, these heterogeneous catalysts, such as solid acids (zeolites, clays, metal oxides etc.), resulted in >90 % conversion of hemicellulose. It has been shown that the selectivity for the products can be tuned by changing the reaction conditions, for example, a reaction carried out in water at 170 °C for 1 h with HBeta (Si/Al=19) and HUSY (Si/Al=15) catalysts gave yields of 62 and 56 % for xylose and arabinose, respectively. With increased reaction time (6 h) and in presence of only water, HUSY resulted in yields of 30 % xylose + arabinose and 18 % furfural. However, in a biphasic reaction system (water + p-xylene, 170 °C, 6 h) yields of 56 % furfural with 17 % xylose+arabinose could be achieved. It was shown that with the addition of organic solvent the furfural yield could be increased from 18 to 56 %. Under optimized reaction conditions, >90 % carbon balance was observed. The study revealed that catalysts were recyclable with a 20 % drop in activity for each subsequent run. It was observed that temperature, pressure, reaction time, substrate to catalyst ratio, solvent, and so forth had an effect on product formation. The catalysts were characterized by means of X-ray diffraction, temperature-programmed desorption of NH(3), inductively coupled plasma spectroscopy, elemental analysis, and solid-state NMR ((29)Si, (27)Al) spectroscopy techniques. PMID:22411884

  1. Recent advances in secondary ion mass spectrometry of solid acid catalysts: large zeolite crystals under bombardment.

    PubMed

    Hofmann, Jan P; Rohnke, Marcus; Weckhuysen, Bert M

    2014-03-28

    This Perspective aims to inform the heterogeneous catalysis and materials science community about the recent advances in Time-of-Flight-Secondary Ion Mass Spectrometry (ToF-SIMS) to characterize catalytic solids by taking large model H-ZSM-5 zeolite crystals as a showcase system. SIMS-based techniques have been explored in the 1980-1990's to study porous catalyst materials but, due to their limited spectral and spatiotemporal resolution, there was no real major breakthrough at that time. The technical advancements in SIMS instruments, namely improved ion gun design and new mass analyser concepts, nowadays allow for a much more detailed analysis of surface species relevant to catalytic action. Imaging with high mass and lateral resolution, determination of fragment ion patterns, novel sputter ion concepts as well as new mass analysers (e.g. ToF, FTICR) are just a few novelties, which will lead to new fundamental insight from SIMS analysis of heterogeneous catalysts. The Perspective article ends with an outlook on instrumental innovations and their potential use for catalytic systems other than zeolite crystals. PMID:24522877

  2. Direct synthesis of H 2O 2 from H 2 and O 2 over Pd\\/H-beta catalyst in an aqueous acidic medium: Influence of halide ions present in the catalyst or reaction medium on H 2O 2 formation

    Microsoft Academic Search

    Chanchal Samanta; Vasant R. Choudhary

    2007-01-01

    The influence of different halide ions present in the catalyst or reaction medium on the performance of Pd\\/H-beta catalyst in the direct H2O2 synthesis in an aqueous acidic (0.03M H3PO4) reaction medium at 27°C and atmospheric pressure has been thoroughly investigated. The results showed a strong influence of both the bulk Pd oxidation state in the catalyst and the halide

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

    PubMed

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

    2014-01-01

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

  4. Selective Oxidation of 1,6-Hexanediol to 6-Hydroxycaproic Acid over Reusable Hydrotalcite-Supported Au-Pd Bimetallic Catalysts.

    PubMed

    Tuteja, Jaya; Nishimura, Shun; Choudhary, Hemant; Ebitani, Kohki

    2015-06-01

    Selective oxidation of 1,6-hexanediol into 6-hydroxycaproic acid was achieved over hydrotalcite-supported Au-Pd bimetallic nanoparticles as heterogeneous catalyst using aqueous H2 O2 . N,N-dimethyldodecylamine N-oxide (DDAO) was used as an efficient capping agent. Spectroscopic analyses by UV/Vis, TEM, XPS, and X-ray absorption spectroscopy suggested that interactions between gold and palladium atoms are responsible for the high activity of the reusable Au40 Pd60 -DDAO/HT catalyst. PMID:25990616

  5. 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

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

    2014-12-01

    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

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

    NASA Astrophysics Data System (ADS)

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

    2009-11-01

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

  7. Direct synthesis of H 2O 2 from H 2 and O 2 and decomposition\\/hydrogenation of H 2O 2 in an aqueous acidic medium over halide-modified Pd\\/Al 2O 3 catalysts

    Microsoft Academic Search

    Chanchal Samanta; Vasant R. Choudhary

    2007-01-01

    Direct synthesis of H2O2 from its elements was carried out in an acidic aqueous reaction medium over halide-modified oxidized and reduced Pd\\/Al2O3 catalysts under very mild conditions (at 27°C and atmospheric pressure). The halide ions were introduced into the catalyst by incorporating halide ions into supported Pd\\/?-Al2O3 catalyst or via depositing halide ions on the support (?-Al2O3) prior to Pd

  8. Hydrogen production from steam reforming of ethanol with nano-Ni\\/SiO 2 catalysts prepared at different Ni to citric acid ratios using a sol–gel method

    Microsoft Academic Search

    Chunfei Wu; Paul T. Williams

    2011-01-01

    Steam reforming of ethanol to produce hydrogen was carried out using a two-stage reaction system with several nano-Ni\\/SiO2 catalysts prepared at different citric acid (CA) contents using the sol–gel process. The fresh (non-calcined and calcined) catalysts and the reacted catalysts were analysed using surface area and pore size analysis, Fourier-transform infrared (FTIR) spectroscopy, thermo-gravimetry analysis (TGA), scanning electron microscopy (SEM)

  9. 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

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

    2013-07-28

    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

  10. Carbon fiber cloth supported Au nano-textile fabrics as an efficient catalyst for hydrogen peroxide electroreduction in acid medium

    NASA Astrophysics Data System (ADS)

    Yang, Fan; Cheng, Kui; Wang, Guiling; Cao, Dianxue

    2015-09-01

    The size-controlled hierarchical textile-like Au nanostructures supported carbon fiber cloth (Au NTs/CFC) is successfully fabricated through a simple low-cost electrochemical route. The electrodes are characterised by scanning electron microscopy equipped with an energy dispersive X-ray spectrometer, transmission electron microscopy and X-ray diffractometer. Without any conducting carbons and polymer binders, the 3D electrode with unique structure is directly used as the electrocatalyst for H2O2 reduction in acid solution and the catalytic performance is evaluated by voltammetry and chronoamperometry. The Au NTs/CFC electrode exhibits much higher catalytic activity and remarkably improved utilization of Au than Au nanoparticles (Au NPs/CFC) prepared by the same method owing to its unique structure. In the solution of 3.0 mol L-1 H2SO4 + 0.1 mol L-1 H2O2, with the reduction potential of 0 V, the current of -0.72 A cm-2 mg-1 can be obtained on Au NTs/CFC electrode and only a current of -0.09 A cm-2 mg-1 can be achieved on Au NPs/CFC electrode. All these results reveal that the novel Au NTs/CFC electrode exhibits excellent catalytic performance and superior stability for H2O2 electroreduction in acid medium, benefitting from the unique 3D structure which can ensure high utilization of catalyst.

  11. 3D-nanoarchitectured Pd/Ni catalysts prepared by atomic layer deposition for the electrooxidation of formic acid.

    PubMed

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

    2014-01-01

    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

  12. Perrhenic acid as catalyst for hydrosilylation of aldehydes and ketones and dehydrogenative silylation of alcohols

    Microsoft Academic Search

    Patr?´cia M. Reis; Beatriz Royo

    2007-01-01

    Hydrosilylation of aldehydes and ketones with dimethylphenylsilane was catalyzed by perrhenic acid, HReO4, to give silylated ethers in good yields. These hydrosilylation reactions appear to be radical processes, since they were inhibited in the presence of 5,5-dimethyl-4,5-dihydro-3H-pyrrole-N-oxide (DMPO) and Ph2NH, two well-known radical scavengers. Perrhenic acid also catalyzes the dehydrogenative silylation of alcohols in neat conditions at 25°C. It is

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

    Microsoft Academic Search

    Beyhan Erdem; Ali Kara

    2011-01-01

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

  14. Synthesis of Waste Cooking Oil Based Biodiesel via Ferric-Manganese Promoted Molybdenum Oxide / Zirconia Nanoparticle Solid acid Catalyst: Influence of Ferric and Manganese Dopants.

    PubMed

    Alhassan, Fatah H; Rashid, Umer; Taufiq-Yap, Yun Hin

    2015-05-01

    The utilization of ferric-manganese promoted molybdenum oxide/zirconia (Fe-Mn- MoO3/ZrO2) (FMMZ) solid acid catalyst for production of biodiesel was demonstrated. FMMZ is produced through impregnation reaction followed by calcination at 600°C for 3 h. The characterization of FMMZ had been done using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA), temperature programmed desorption of NH3 (TPD-NH3), transmission electron microscopy(TEM) and Brunner-Emmett-Teller (BET) surface area measurement. The effect of waste cooking oil methyl esters (WCOME's) yield on the reactions variables such as reaction temperature, catalyst loading, molar ratio of methanol/oil and reusability were also assessed. The catalyst was used to convert the waste cooking oil into corresponding methyl esters (95.6%±0.15) within 5 h at 200? reaction temperature, 600 rpm stirring speed, 1:25 molar ratio of oil to alcohol and 4% w/w catalyst loading. The reported catalyst was successfully recycled in six connective experiments without loss in activity. Moreover, the fuel properties of WCOME's were also reported using ASTM D 6751 methods. PMID:25843280

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

    PubMed Central

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

    2014-01-01

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

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

    PubMed

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

    2006-05-01

    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

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

    PubMed

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

    2014-01-01

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

  18. KAl(SO4)2·12H2O as a Recyclable Lewis Acid Catalyst for Synthesis of Some Amidoalkyl Naphthols Under Solvent-Free Conditions

    Microsoft Academic Search

    Hossein A. Oskooie; Majid M. Heravi; Narges Karimi; Akram Amouchi; Golnaz Kohansal

    2011-01-01

    A general and practical one-pot synthesis of amidoalkyl naphthols derivatives using KAl(SO4)2·12H2O as catalyst is described. This method provides several advantages such as short reaction times, high yields and simple workup procedure.

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

    SciTech Connect

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

    2012-10-31

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

  20. 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...

  1. Catalyst Alloys Processing

    NASA Astrophysics Data System (ADS)

    Tan, Xincai

    2014-10-01

    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.

  2. Process of making supported catalyst

    DOEpatents

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

    1992-01-01

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

  3. Graphite-supported perchloric acid (HClO4-C): an efficient and recyclable heterogeneous catalyst for the one-pot synthesis of amidoalkyl naphthols.

    PubMed

    Lei, Zhen-Kai; Xiao, Li; Lu, Xiao-Quan; Huang, He; Liu, Chen-Jiang

    2013-01-01

    An efficient and direct protocol for the preparation of amidoalkylnaphthols employing a multi-component, one-pot condensation reaction of 2-naphthol, aromatic aldehydes and acetamide or benzamide in the presence of graphite supported perchloric acid under solvent-free conditions is described. The thermal solvent-free procedure offers advantages such as simple work-up, shorter reaction times and higher product yields, and the catalyst exhibited remarkable reactivity and can be recycled. PMID:23358323

  4. Effect of the structural characteristics of binary Pt-Ru and ternary Pt-Ru-M fuel cell catalysts on the activity of ethanol electrooxidation in acid medium.

    PubMed

    Antolini, Ermete

    2013-06-01

    In view of their possible use as anode materials in acid direct ethanol fuel cells, the electrocatalytic activity of Pt-Ru and Pt-Ru-M catalysts for ethanol oxidation has been investigated. This minireview examines the effects of the structural characteristics of Pt-Ru, such as the degree of alloying and Ru oxidation state, on the electrocatalytic activity for ethanol oxidation. PMID:23650220

  5. Preparation and evaluation of advanced catalysts for phosphoric acid fuel cells

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

    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.

  6. ZnO/carbon nano composite: Effective catalyst for the photo degradation of Acid Blue 113

    NASA Astrophysics Data System (ADS)

    Sunitha, S.; Rao, A. Nageswara; Karthikeyan, J.; Krithiga, T.

    2013-06-01

    Zinc oxide carbon composite (ZnO/C) was synthesized by self - propagating solution combustion method. This method enabled the addition of carbon insitu to the metal oxide. The composite synthesized were characterised by XRD, SEM and BET analysis. This composite was used for the removal of organic pollutants such as the dye Acid blue 113 by UV irradiation performed in a batch reactor. The influence of various experimental parameters such as the initial concentration of the dye, Concentration of the photocatalyst and the pH on the photo catalytic degradation under UV irradiation was studied. It has been observed that the degradation of the dye to be more pronounced in neutral medium. The degradation of acid blue 113 was found to increase with ZnO/C composites loading and decreases with decrease in concentration of the composite.

  7. Preparation and evaluation of advanced catalysts for phosphoric acid fuel cells

    NASA Astrophysics Data System (ADS)

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

    1984-06-01

    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.

  8. Green chemistry: Biodiesel made with sugar catalyst

    Microsoft Academic Search

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

    2005-01-01

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

  9. Study on Preparation Process of Lubrication from 1-Decene with Acidic Ionic Liquid Catalyst

    Microsoft Academic Search

    H. Ding; B. Y. Zhang; J. Liu

    2009-01-01

    Poly-alpha-olefin (PAO) was researched over acidic ionic liquid catalyzed the oligomerization of 1-decene. Ionic liquid used was 1-butyl-3-methyl imidazolium as a cation and aluminum chloride as an anion, which could effectively catalyze oligomerization and had a higher selectivity. The optimum process conditions for the synthesis of PAO were that the reaction temperature was 160°C, the reaction time was 3 h,

  10. A Gold-Nickel Alloy as Anodic Catalyst in a Direct Formic Acid Fuel Cell

    Microsoft Academic Search

    Zhang Lijuan; Tian Ruili; Hu Pu; Ma Yuru; Xia Dingguo

    2010-01-01

    Gold-nickel alloy was synthesized by arc-melted process. The electro-oxidation of formic acid of Au-Ni alloy was investigated at room temperature by cyclic voltammetry and chronoamperometry. The results were compared with those at a polycrystalline gold electrode surface. It is found that Au-Ni alloy is catalytically more active than pure gold according to the comparison of the main peak potential and

  11. Mo oxide modified catalysts for direct methanol, formaldehydeand formic acid fuel cells

    Microsoft Academic Search

    Chaojie Song; Mohammad Khanfar; Peter G. Pickup

    2006-01-01

    Pt black and PtRu black fuel cell anodes have been modified with Mo oxide and evaluated in direct methanol, formaldehyde and\\u000a formic acid fuel cells. Mo oxide deposition by reductive electrodeposition from sodium molybdate or by spraying of the fuel\\u000a cell anode with aqueous sodium molybdate resulted in similar performance gains in formaldehyde cells. At current densities\\u000a below ca. 20 mA cm?2,

  12. Performance degradation of direct formic acid fuel cell incorporating a Pd anode catalyst

    Microsoft Academic Search

    Won Suk Jung; Jonghee Han; Sung Pil Yoon; Suk Woo Nam; Tae-Hoon Lim; Seong-Ahn Hong

    2011-01-01

    Electrochemical and physical analysis is employed to verify the performance degradation mechanism in direct formic acid fuel cells (DFAFCs). The power density of a single cell measured at 200mAcm?2 decreases by 40% after 11h of operation. The performance of the single cell is partly recovered however, by a reactivation process. Various analytical methods such as scanning electron microscopy (SEM), transmission

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

    Microsoft Academic Search

    Sandra Abad; Jozef Nahalka; Gabriele Bergler; S Alison Arnold; Robert Speight; Ian Fotheringham; Bernd Nidetzky; Anton Glieder

    2010-01-01

    BACKGROUND: Trigonopsis variabilis D-amino acid oxidase (TvDAO) is a well characterized enzyme used for cephalosporin C conversion on industrial scale. However, the demands on the enzyme with respect to activity, operational stability and costs also vary with the field of application. Processes that use the soluble enzyme suffer from fast inactivation of TvDAO while immobilized oxidase preparations raise issues related

  14. Mechanism of Glucose Isomerization Using a Solid Lewis Acid Catalyst in Water

    SciTech Connect

    Roman-Leshkov, Yuriy; Moliner, Manuel; Labinger, J A; Davis, Mark E.

    2010-01-01

    {sup 1}H and {sup 13}C?NMR spectroscopy on isotopically labeled glucose reveals that in the presence of tin-containing zeolite Sn-Beta, the isomerization reaction of glucose in water proceeds by way of an intramolecular hydride shift rather than proton transfer. This is the first mechanistic demonstration of Sn-Beta acting as a Lewis acid in a purely aqueous environment.

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

    PubMed

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

    2010-07-15

    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

  16. Hydrogenation of succinic acid to ?-butyrolactone (GBL) over ruthenium catalyst supported on surfactant-templated mesoporous carbon

    Microsoft Academic Search

    Ung Gi Hong; Hai Woong Park; Joongwon Lee; Sunhwan Hwang; In Kyu Song

    Mesoporous carbon support (denoted as STC) was prepared by a surfactant-templating method for use as a support for ruthenium catalyst. For comparison, porous carbon (denoted as TC), spherical carbon (denoted as SC), and microporous carbon (denoted as DC) supports were also prepared by a templating method, hydrothermal method, and direct carbonization method, respectively. Ruthenium catalysts supported on carbon supports (Ru\\/C)

  17. Highly active carbon supported palladium catalysts decorated by a trace amount of platinum by an in-situ galvanic displacement reaction for formic acid oxidation

    NASA Astrophysics Data System (ADS)

    Li, Zuopeng; Li, Muwu; Han, Mingjia; Wu, Xin; Guo, Yong; Zeng, Jianhuang; Li, Yuexia; Liao, Shijun

    2015-03-01

    Aimed at reducing platinum usage and improved catalytic activity for formic acid oxidation, a series of Pt decorated Pd/C catalysts are prepared by an in-situ galvanic displacement reaction between freshly prepared Pd/C ink and H2PtCl6 in an aqueous solution. The catalysts with 4 nm particle sizes and 20 wt.% loadings have been characterized by transmission electron microscopy, thermogravimetric analysis and X-ray photoelectron spectroscopy (XPS). The electrochemical evaluations by cyclic voltammetry are conducted to test out the CO tolerance and catalytic activities. In addition to XPS analysis, a theoretical calculation has been attempted the first time to find out the surface Pd/Pt molar ratios. The decay rate of the catalysts has been evaluated by the percentage of the forward/backward peak current retained using the value at the 20th cycle divided by that in the first cycle. Compared with a Pd/C benchmark, all Pt decorated Pd/C register enhanced activity while the cost remains virtually unchanged. The optimized catalyst is found to have a Pd/Pt molar ratio of 75:1 but with 2.5 times activity relative to that of Pd/C.

  18. Nickel-catalyzed cross-coupling of functionalized difluoromethyl bromides and chlorides with aryl boronic acids: a general method for difluoroalkylated arenes.

    PubMed

    Xiao, Yu-Lan; Guo, Wen-Hao; He, Guo-Zhen; Pan, Qiang; Zhang, Xingang

    2014-09-01

    Transition-metal-catalyzed difluoroalkylation of aromatics remains challenging despite the importance of difluoroalkylated arenes in medicinal chemistry. Herein, the first successful example of nickel-catalyzed difluoroalkylation of aryl boronic acids is described. The reaction allows access to a variety of functionalized difluoromethyl bromides and chlorides, and paves the way to highly cost-efficient synthesis of a wide range of difluoroalkylated arenes. The notable features of this protocol are its high generality, excellent functional-group compatibility, low-cost nickel-catalyst, and practicality for gram-scale production, thus providing a facile method for applications in drug discovery and development. PMID:25044391

  19. Development of ternary alloy cathode catalysts for phosphoric acid fuel cells: Final report

    SciTech Connect

    Jalan, V.; Kosek, J.; Giner, J.; Taylor, E. J.; Anderson, E.; Bianchi, V.; Brooks, C.; Cahill, K.; Cropley, C.; Desai, M.; Frost, D.; Morriseau, B.; Paul, B.; Poirier, J.; Rousseau, M.; Swette, L.; Waterhouse, R.

    1988-11-01

    The overall objective of the program was the identification development and incorporation of high activity platinum ternary alloys on corrosion resistant supports, for use in advanced phosphoric acid fuel cells. Two high activity ternary alloys, Pr-Cr-Ce and Pt-Ni-Co, both supported on Vulcan XC-72, were identified during the course of the program. The Pr-Ni-Co system was selected for optimization, including preparation and evaluation on corrosion resistant supports such as 2700/degree/C heat-treated Vulcan XC-72 and 2700/degree/ heat-treated Black Pearls 2000. A series of tests identified optimum metal ratios, heat-treatment temperatures and heat-treatment atmospheres for the Pr-Ni-Co system. During characterization testing, it was discovered that approximately 50% of the nickel and cobalt present in the starting material could be removed, subsequent to alloy formation, without degrading performance. Extremely stable full cell performance was observed for the Pt-Ni-Co system during a 10,000 hour atmosphere pressure life test. Several theories are proposed to explain the enhancement in activity due to alloy formation. Recommendations are made for future research in this area. 62 refs., 23 figs., 27 tabs.

  20. Kinetics of Mo, Ni, V and Al leaching from a spent hydrodesulphurization catalyst in a solution containing oxalic acid and hydrogen peroxide.

    PubMed

    Szymczycha-Madeja, Anna

    2011-02-28

    The kinetics of molybdenum, nickel, vanadium and aluminium leaching from a spent hydrodesulphurization catalyst in a solution containing oxalic acid and hydrogen peroxide was investigated. The effects of temperature and particle size were examined. In addition, the reaction mechanism for the dissolution of the spent catalyst was discussed. The results of the kinetic analysis for various experimental conditions indicated that the reaction rate of leaching process is controlled by chemical reaction at the particle surface. The values of the activation energies of 31±2, 36±4, 30±4 and 57±3 kJ mol(-1) for Mo, Ni, V and Al, respectively, are characteristic for mechanism controlled by chemical reaction. PMID:21167639

  1. Improved catalysts and method

    SciTech Connect

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

    1990-12-31

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

  2. Improved molecular weight control in ring-opening metathesis polymerization (ROMP) reactions with ru-based olefin metathesis catalysts using N donors and acid: a kinetic and mechanistic investigation.

    PubMed

    Dunbar, Miles A; Balof, Shawna L; LaBeaud, Lawrence J; Yu, Bing; Lowe, Andrew B; Valente, Edward J; Schanz, Hans-Jörg

    2009-11-16

    The effect of the addition of H(3)PO(4) on the ROMP activity of cyclooctene (COE) with first- [Cl(2)(PCy(3))(2)Ru=CHPh] and second-generation [(H(2)IMes)Cl(2)(PCy(3))Ru=CHPh] Grubbs' catalysts 1 and 4 (Cy=cyclohexyl, Ph=phenyl, Mes=2,4,6-trimethylphenyl (mesityl)), their inhibited mixtures with 1-methylimidazole (MIM), as well as their isolated bis-N,N'-dimethylaminopyridine (DMAP) derivatives [Cl(2)(PCy(3))(DMAP)(2)Ru=CHPh)] (5 b) and [Cl(2)(H(2)IMes)(DMAP)(2)Ru=CHPh] (7 b) (DMAP=dimethylaminopyridine), a novel catalyst, has been investigated. The studies include the determination of their initiation rates, as well as a determination of the molecular weights and molecular weight distributions of the polymers obtained with these catalysts and catalyst mixtures from the exo-7-oxanorbornene derivative 11. The structure of catalyst 7 b was confirmed by means of X-ray diffraction. All N-donor-bearing catalysts or N-donor-containing catalyst mixtures not only exhibited elevated activity in the presence of acid, but also increased initiation rates. Using the reversible inhibition/activation protocol with MIM and H(3)PO(4) enabled us to conduct controlled ROMP with catalyst 4 producing the isolated exo-7-oxanorbornene-based polymer 12 with predetermined molecular weights and narrow molecular weight distributions. This effect was based on fast and efficient catalyst initiation in contrast to the parent catalyst 4. Hexacoordinate complex 5 b also experienced a dramatic increase in initiation rates upon acid-addition and the ROMP reactions became well-controlled in contrast to the acid-free reaction. In contrast, complex 7 b performs well-controlled ROMP in the absence of acid, whereas the polymerization of the same monomer becomes less controlled in the presence of H(3)PO(4). The closer evaluation of catalysts 5 b and 7 b demonstrated that their initiation rates exhibit a linear dependency on the substrate concentration in contrast to catalysts 1 and 4. As a consequence, their initiation rates are determined by an associative step, not a dissociative step as seen for catalysts 1 and 4. A feasible associative metathesis initiation mechanism is proposed. PMID:19821457

  3. Reactivation of hydroformylation catalysts

    SciTech Connect

    Babin, J.E.; Bryant, D.R.; Harrison, A.M.; Miller, D.J.

    1993-08-17

    A process is described for improving the catalytic activity of a partially deactivated solubilized rhodium-tertiary organophosphine complex hydroformylation catalyst, which comprises (1) mixing under non-hydroformylating conditions, a organic liquid medium containing said solubilized partially deactivated complex catalyst, with propargyl alcohol and a carboxylic acid of the formula RCOOH wherein R represents hydrogen or an alkyl or aryl radical to obtain a treated solubilized rhodium-tertiary organophosphine complex product solution; and (2) removing from said product solution, the carboxylic acid employed in Step (1) to obtain a rhodium-tertiary organophosphine complex hydroformylation catalyst that is more catalytically active than said partially deactivated rhodium-tertiary organophosphine complex hydroformylation catalyst starting material of Step (1).

  4. Immobilized bisdiazaphospholane catalysts for asymmetric hydroformylation.

    PubMed

    Adint, Tyler T; Landis, Clark R

    2014-06-01

    Condensation reactions of enantiopure bis-3,4-diazaphospholanes (BDPs) that are functionalized with carboxylic acids enable covalent attachment to bead and silica supports. Exposure of tethered BDPs to the hydroformylation catalyst precursor, Rh(acac)(CO)2, yields catalysts for immobilized asymmetric hydroformylation (iAHF) of prochiral alkenes. Compared with homogeneous catalysts, catalysts immobilized on Tentagel resins exhibit similarly high regioselectivity and enantioselectivity. When corrected for apparent catalyst loading, the activity of the immobilized catalysts approaches that of the homogeneous analogues. Excellent recyclability with trace levels of rhodium leaching are observed in batch and flow reactor conditions. Silica-bound catalysts exhibit poorer enantioselectivities. PMID:24742285

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

    PubMed

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

    2014-02-01

    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

  6. The effect of metal ions as co-catalysts on acidic ionic liquid catalyzed single-step saccharification of corn stover in water.

    PubMed

    Wiredu, Bernard; Amarasekara, Ananda S

    2015-08-01

    The effects of adding Cr(3+), Mn(2+), Fe(3+), Co(2+) Ni(2+), Cu(2+), Zn(2+) and La(3+) chlorides as co-catalysts to 1-(1-propylsulfonic)-3-methylimidazolium chloride acidic ionic liquid catalyzed saccharification of corn stover in aqueous medium was studied at 140-170°C, by measuring the total reducing sugar (TRS) and glucose yields. The samples with Mn(2+), Fe(3+), Co(2+) as co-catalysts produced higher TRS yields compared to the sample without the metal ions. The Mn(2+) produced the highest catalytic effect enhancements and produced TRS yields of 68.0%, 72.9%, 90.2% and 87.9% at 140, 150, 160 and 170°C respectively; whereas the corn stover samples without the Mn(2+) produced TRS yields of 42.9%, 52.3%, 54.4% and 53.5% at the same four temperatures. At higher temperatures of 160 and 170°C, all metal ions studied produced significant enhancements in glucose yields, except Cr(3+). The addition of La(3+) as a co-catalyst produced the highest glucose yield improvement. PMID:25911191

  7. Selective aerobic oxidation of 5-HMF into 2,5-furandicarboxylic acid with Pt catalysts supported on TiO2 - and ZrO2 -based supports.

    PubMed

    Ait Rass, Hicham; Essayem, Nadine; Besson, Michèle

    2015-04-13

    Pt catalysts prepared over different metallic oxide supports were investigated in the oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) in alkaline aqueous solutions with air, to examine the combined effect of the support and base addition. The base (nature and amount) played a significant role in the degradation or oxidation of HMF. Increasing amounts of the weak NaHCO3 base improved significantly the overall catalytic activity of Pt/TiO2 and Pt/ZrO2 by accelerating the oxidation steps, especially for the aldehyde group. This was highlighted by a proposed kinetic model that gave very good concentration-time fittings. Moreover, the promotion of the catalyst with bismuth yielded a Pt?Bi/TiO2 catalytic system with improved activity and stability. Y2 O3 ? and La2 O3 ?ZrO2 -supported catalysts exhibited lower activity than Pt/ZrO2 , which suggests no cooperative effect of the weakly basic properties introduced and the homogeneous base. Quantitative oxidation of HMF (0.1?M) and high yields of FDCA (>99?%) were obtained in less than 5?h by using an HMF/Pt molar ratio of 100 and Na2 CO3 as a weak base over Pt?Bi/TiO2 (Bi/Pt=0.22). PMID:25736596

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

    PubMed

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

    2011-02-28

    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

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

    PubMed Central

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

    2012-01-01

    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

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

    PubMed

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

    2013-10-18

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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.

  12. Heterogeneous base catalysts for edible palm and non-edible Jatropha-based biodiesel production

    PubMed Central

    2014-01-01

    Background Transesterification catalyzed by solid base catalyst is a brilliant technology for the noble process featuring the fast reaction under mild reacting condition in biodiesel production. Heterogeneous base catalysts are generally more reactive than solid acid catalysts which require extreme operating condition for high conversion and biodiesel yield. In the present study, synthesis of biodiesel was studied by using edible (palm) or non-edible (Jatropha) feedstock catalyzed by heterogeneous base catalysts such as supported alkali metal (NaOH/Al2O3), alkaline-earth metal oxide (MgO, CaO and SrO) and mixed metal oxides catalysts (CaMgO and CaZnO). Results The chemical characteristic, textural properties, basicity profile and leaching test of synthesized catalysts were studied by using X-ray diffraction, BET measurement, TPD-CO2 and ICP-AES analysis, respectively. Transesterification activity of solid base catalysts showed that?>?90% of palm biodiesel and?>?80% of Jatropha biodiesel yield under 3 wt.% of catalyst, 3 h reaction time, methanol to oil ratio of 15:1 under 65°C. This indicated that other than physicochemical characteristic of catalysts; different types of natural oil greatly influence the catalytic reaction due to the presence of free fatty acids (FFAs). Conclusions Among the solid base catalysts, calcium based mixed metal oxides catalysts with binary metal system (CaMgO and CaZnO) showed capability to maintain the transesterification activity for 3 continuous runs at?~?80% yield. These catalysts render high durability characteristic in transesterification with low active metal leaching for several cycles. PMID:24812574

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

    SciTech Connect

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

    2013-06-26

    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.

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

    PubMed

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

    2012-11-15

    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

  15. 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

    Wang. Yong (Richland, WA); Peden. Charles H. F. (West Richland, WA); Choi. Saemin (Richland, WA)

    2004-11-09

    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.

  16. Effects of iron-tetrasulfophthalocyanine on the catalytic activities of Pt\\/C, PtRu\\/C, and Pd\\/C catalysts in a multi-anode direct formic acid fuel cell

    Microsoft Academic Search

    Xingwen Yu; Peter G. Pickup

    2010-01-01

    This paper reports a systematic study of the effects of a promoter, iron-tetrasulfophthalocyanine (FeTSPc), on the catalytic\\u000a activities of carbon supported Pt, PtRu, and Pd catalysts (Pt\\/C, PtRu\\/C, and Pd\\/C) for formic acid oxidation. A multi-anode\\u000a direct formic acid fuel cell (DFAFC) was used to compare the effects on each catalyst of adding FeTSPc to the fuel stream.\\u000a The FeTSPc

  17. Catalyst for Decomposition of Nitrogen Oxides

    NASA Technical Reports Server (NTRS)

    Schryer, David R. (Inventor); Jordan, Jeffrey D. (Inventor); Akyurtlu, Ates (Inventor); Akyurtlu, Jale (Inventor)

    2015-01-01

    This invention relates generally to a platinized tin oxide-based catalyst. It relates particularly to an improved platinized tin oxide-based catalyst able to decompose nitric oxide to nitrogen and oxygen without the necessity of a reducing gas.

  18. Pore structure modification of diatomite as sulfuric acid catalyst support by high energy electron beam irradiation and hydrothermal treatment

    NASA Astrophysics Data System (ADS)

    Li, Chong; Zhang, Guilong; Wang, Min; Chen, Jianfeng; Cai, Dongqing; Wu, Zhengyan

    2014-08-01

    High energy electron beam (HEEB) irradiation and hydrothermal treatment (HT), were applied in order to remove the impurities and enlarge the pore size of diatomite, making diatomite more suitable to be a catalyst support. The results demonstrated that, through thermal, charge, impact and etching effects, HEEB irradiation could make the impurities in the pores of diatomite loose and remove some of them. Then HT could remove rest of them from the pores and contribute significantly to the modification of the pore size distribution of diatomite due to thermal expansion, water swelling and thermolysis effects. Moreover, the pore structure modification improved the properties (BET (Brunauer-Emmett-Teller) specific surface area, bulk density and pore volume) of diatomite and the catalytic efficiency of the catalyst prepared from the treated diatomite.

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

    PubMed

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

    2012-09-26

    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

  20. Etherification of 5-hydroxymethyl-2-furfural (HMF) with ethanol to biodiesel components using mesoporous solid acidic catalysts

    Microsoft Academic Search

    P. Lanzafame; D. M. Temi; S. Perathoner; G. Centi; A. Macario; A. Aloise; G. Giordano

    2011-01-01

    The etherification of 5-hydroxymethyl-2-furfural (HMF) with ethanol is studied over a series of mesoporous silica catalysts (Al-MCM-41 materials with different Si\\/Al ratio, and zirconia or sulfated zirconia supported over SBA-15) and compared with the behavior of H2SO4 and Amberlyst®15. The observed reaction products were 5-(ethoxymethyl)furan-2-carbaldehyde (EMF), 1,1-dietoxy ethane (DE) and ethyl 4-oxopentanoate (EOP). The selectivity to EMF and EOP is

  1. Active sites in working bifunctional GaH-TON aromatization catalysts: kinetic evaluation.

    PubMed

    Lukyanov, Dmitry B; Vazhnova, Tanya

    2006-09-21

    The conversion of light alkanes to high value aromatics proceeds with a high selectivity over bifunctional, gallium (Ga) containing zeolite catalysts. It is generally agreed that Ga sites are involved in dehydrogenation reaction steps and that the zeolite acid sites catalyze cracking, oligomerization, and cyclization reactions. However, understanding of the precise roles of the acid and Ga sites in the reaction mechanisms is significantly hampered since the number of these sites in working catalysts is not known. This paper describes a kinetic approach to evaluation of the acid and Ga active sites in working Ga containing TON zeolite catalysts that relies on the analysis of the rates of formation of the primary products of a n-butane aromatization reaction. Our results show that the rate of ethane formation at low n-butane conversions can be used as a quantitative estimate of acidity in working bifunctional zeolite catalysts and demonstrate, for the first time, a significant decrease in the number of Brønsted acid sites in the Ga containing catalysts under reaction conditions: around 47 and 79% for the catalysts with Ga loading of 1.5 and 2.5 wt %, respectively. We conclude that the reduction in acidity is associated with the formation of catalytically active Ga(+) ions and obtain estimates for the number and steady-state turnover activity of the acid and Ga active sites in n-butane transformation. We anticipate that our work will facilitate understanding of the precise roles of the acid and Ga sites in the mechanisms of alkane aromatization and, as a far-reaching implication, will prompt wider use of detailed kinetic studies for the evaluation of active sites in working catalysts. PMID:16970474

  2. Oriented and selective enzyme immobilization on functionalized silica carrier using the cationic binding module Z basic2: design of a heterogeneous D-amino acid oxidase catalyst on porous glass.

    PubMed

    Bolivar, Juan M; Nidetzky, Bernd

    2012-06-01

    D-amino acid oxidase from Trigonopsis variabilis (TvDAO) is applied in industry for the synthesis of pharmaceutical intermediates. Because free TvDAO is extremely sensitive to exposure to gas-liquid interfaces, biocatalytic processing is usually performed with enzyme immobilizates that offer enhanced stability under bubble aeration. We herein present an "Immobilization by Design" approach that exploits engineered charge complementarity between enzyme and carrier to optimize key features of the immobilization of TvDAO. A fusion protein between TvDAO and the positively charged module Z(basic2) was generated, and a corresponding oppositely charged carrier was obtained by derivatization of mesoporous glass with 3-(trihydroxysilyl)-1-propane-sulfonic acid. Using 250 mM NaCl for charge screening at pH 7.0, the Z(basic2) fusion of TvDAO was immobilized directly from E. coli cell extract with almost absolute selectivity and full retention of catalytic effectiveness of the isolated enzyme in solution. Attachment of the homodimeric enzyme to the carrier was quasi-permanent in low-salt buffer but fully reversible upon elution with 5 M NaCl. Immobilized TvDAO was not sensitive to bubble aeration and received substantial (? tenfold) stabilization of the activity at 45°C as compared to free enzyme, suggesting immobilization via multisubunit oriented interaction of enzyme with the insoluble carrier. The Z(basic2) enzyme immobilizate was demonstrated to serve as re-usable heterogeneous catalyst for D-amino acid oxidation. Z(basic2) -mediated binding on a sulfonic acid group-containing glass carrier constitutes a generally useful strategy of enzyme immobilization that supports transition from case-specific empirical development to rational design. PMID:22249953

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

    Microsoft Academic Search

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

    2011-01-01

    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 ¹N NMR, static ²H 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

  4. Presynaptic GABA Band ?-hydroxybutyric acid-mediated mechanisms in generalized absence seizures

    Microsoft Academic Search

    O. C. Snead

    1996-01-01

    ?-Hydroxybutyric acid (GHB) is a naturally occurring compound which has the ability to induce generalized absence seizures when given to animals. This effect of GHB may be blocked by either GHB or GABAB receptor antagonists. We sought to test the hypothesis that pre-synaptic GHB- and GABAB-mediated mechanisms in thalamus and cortex are operative in the GHB model of generalized absence

  5. Silica supported perchloric acid (HClO 4–SiO 2): A highly efficient and reusable catalyst for the protection of hydroxyl groups using HMDS under mild and ambient conditions

    Microsoft Academic Search

    Hamid Reza Shaterian; Fahimeh Shahrekipoor; Majid Ghashang

    2007-01-01

    Various alcohols, phenols, naphthols, and oximes were effectively converted into their corresponding trimethylsilyl ethers with hexamethyldisilazane in the presence of solid silica supported perchloric acid under very mild conditions at room temperature with short reaction time in good to excellent yields. The notable advantages of this protocol are: work up procedure is easy and the catalyst can be recovered by

  6. Heterogeneous catalyst for alcohol oxycarbonylation to dialkyl oxalates

    SciTech Connect

    Gaffney, A.M.; Leonard, J.J.; Sofranko, J.A.; Sun, H.N.

    1987-04-01

    Historically, the first major process for commercial ethylene glycol production from synthesis gas was the acid-catalyzed carbonylation of formaldehyde to glycolic acid. The acid was then hydrogenated to the desired product. Due to major corrosion problems and the relative inexpensiveness of ethylene, this process was abandoned in favor of the ethylene oxide route. There has been recent research activity in this formaldehyde carbonylation process, but again strongly acidic conditions are employed. The similar route of formaldehyde hydroformylation to glycoaldehyde followed by hydrogenation is also attracting attention. Considerable progress has been made in the direct formation of ethylene glycol from synthesis gas. The reaction discussed in this paper is another variant of the synthesis-gas-based routes of ethylene glycol. Dialkyl oxalate esters can be formed from the oxidative carbonylation of carbon monoxide and an alcohol. The dialkyl oxalate ester can then be hydrogenated to yield ethylene glycol. This route offers the advantages of milder reaction conditions and higher selectivities to the desired product. The reaction is generally catalyzed by platinum group metals, notably palladium, in conjunction with a co-oxidant. Phosphorous and titanium promoted palladium-vanadium oxide catalysts were found to be especially effective for alcohol oxycarbonylation. These catalysts were investigated because of the similarities in active catalysts for the oxidative carbonylation process and catalyst systems for the Wacker reaction, involving the oxidation of ethylene to acetaldehyde. This paper discusses how a similar system affects the oxidative carbonylation of alcohols to alkyl oxalates.

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

    PubMed

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

    2012-12-28

    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

  8. In situ FTIR investigation of acetic acid electrooxidation on carbon supported Pt-Sn based trimetallic catalysts: Influence of the nature of the third metal

    NASA Astrophysics Data System (ADS)

    Beyhan, Seden; Léger, Jean-Michel; Kad?rgan, Figen

    2014-12-01

    The effect of adding a third metal (Ni, Co, Pd, Rh) to Pt-Sn/C catalyst has been investigated for the adsorption and oxidation of acetic acid in acidic medium using in situ Fourier transform infrared (FTIR) spectroscopy. The results showed that the decomposition of acetic acid on the surface leads to the formation of different intermediate species and products such as acetate, acetyl, carbonate, CO and CO2. The reaction pathway of CO2 production proceeds via the formation of acetyl or carbonate through surface acetate species. It has been found that the selectivity of the acetate was enhanced by the addition of any third metal. However, the presence of Pd or Co increases the relative intensity of IR band for CO2. This is probably due to success in facilitating of the Csbnd C bond cleavage of acetyl. On the other hand, the conversion of acetate to carbonate is strongly affected by the adsorbed water, as is evident from the pronounced changes in the OH stretching region with the presence of Pd or Ni.

  9. Metal chelate catalysts for fuel cells

    NASA Astrophysics Data System (ADS)

    Darby, R.; Yamana, M.; Dhar, H.; White, R.

    1982-10-01

    Various modified forms of several organometallic chelate compounds were synthesized and tested for their activity and stability as oxygen reduction electrocatalysts in sulfuric acid electrolyte. The most active catalysts found were cobalt tetraazaannulene (CoTAA), iron phthalocyanine (FePc) and cobalt tetraphenylporphyrin (CoTPP). However, these catalysts have limited stability in strong acids.

  10. Metal chelate catalysts for fuel cells

    Microsoft Academic Search

    R. Darby; M. Yamana; H. Dhar; R. White

    1982-01-01

    Various modified forms of several organometallic chelate compounds were synthesized and tested for their activity and stability as oxygen reduction electrocatalysts in sulfuric acid electrolyte. The most active catalysts found were cobalt tetraazaannulene (CoTAA), iron phthalocyanine (FePc) and cobalt tetraphenylporphyrin (CoTPP). However, these catalysts have limited stability in strong acids.

  11. Hydrodewaxing with mixed zeolite catalysts

    SciTech Connect

    Chester, A.W.; McHale, W.D.; Yen, J.H.

    1986-03-11

    A process is described for catalytically dewaxing a hydrocarbon lubricating oil feedstock comprising contacting the feedstock with a dewaxing catalyst, the dewaxing catalyst comprising, in combination: (a) a zeolite catalyst having a Constraint Index not less than 1, (b) an acidic catalytic material selected from the group consisting of Mordenite, TEA Mordenite, Dealuminized Y, Ultrastable Y, Rare Earth Y, amorphous silica-alumina chlorinated alumina, ZSM-4 and ZSM-20, and (c) a hydrogenation component, and recovering a dewaxed product. A process is also described for catalytically dewaxing a hydrocarbon lubricating oil feedstock comprising contacting the feedstock with a dewaxing catalyst, the dewaxing catalyst comprising, in combinations: (a) a first zeolite catalyst selected from the group consisting of ZSM-5, ZMS-11, ZSM-12, ZSM-22, ZSM-23, ZSM-34, ZSM-35, ZSM-38, ZSM-48, TMA Offretite and Erionite, (b) a second catalyst selected from the group consisting of ZSM-12, ZSM-22, ZSM-38 and ZSM-48, the second zeolite catalyst being different from the first zeolite catalyst, and (c) a hydrogenation component, and recovering a dewaxed product.

  12. Preparation and characterization of core–shell structured catalysts using Pt x Pd y as active shell and nano-sized Ru as core for potential direct formic acid fuel cell application

    Microsoft Academic Search

    Haili Gao; Shijun Liao; Jianhuang Zeng; Yichun Xie; Dai Dang

    2011-01-01

    Carbon-supported core–shell structured Ru@PtxPdy\\/C catalysts with PtxPdy as shell and nano-sized Ru as core are prepared by a successive reduction procedure. The catalysts are extensively characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The formic acid oxidation activity of Ru@PtxPdy\\/C varies with the varying Pt:Pd atomic ratio. The peak oxidation potential on Ru@Pt1Pd2\\/C shifts

  13. Characterization and catalytic activity of differently pretreated Pd\\/Al 2O 3 catalysts: the role of acid sites and of palladium–alumina interactions

    Microsoft Academic Search

    M. Skotak; Z. Karpi?ski; W. Juszczyk; J. Pielaszek; L. K?pi?ski; D. V. Kazachkin; V. I. Kovalchuk; J. L. d'Itri

    2004-01-01

    The effect of catalyst pretreatment on the performance of chlorine-free ?-alumina-supported palladium catalysts with metal loadings in the range of 0.3 to 2.77 wt% has been investigated in the hydroconversion of n-hexane (nH) and 2,2-dimethylbutane (22DMB) at 290?°C and atmospheric pressure. The catalyst properties were modified by varying the catalyst pretreatment: low-temperature reduction (LTR) at 300?°C; high-temperature reduction (HTR) at

  14. Ascorbic Acid as a Standard for Iodometric Titrations. An Analytical Experiment for General Chemistry

    NASA Astrophysics Data System (ADS)

    Silva, Cesar R.; Simoni, Jose A.; Collins, Carol H.; Volpe, Pedro L. O.

    1999-10-01

    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.

  15. Activity of Pt anode catalyst modified by underpotential deposited Pb in a direct formic acid fuel cell

    Microsoft Academic Search

    Sunghyun Uhm; Sung Taik Chung; Jaeyoung Lee

    2007-01-01

    We characterized the electrocatalytic activity of platinum electrode modified by underpotential deposited lead (PtPbupd) for a formic acid (HCOOH) oxidation and investigated the influence on the power performance of direct formic acid fuel cells (DFAFC). Based on the electrochemical analysis using cyclic voltammetry and chronoamperometry, PtPbupd electrode modified by underpotential deposition (UPD) exhibited significantly enhanced catalytic activity for HCOOH oxidation

  16. CATALYSTS NHI Thermochemical Systems FY 2009 Year-End Report

    Microsoft Academic Search

    Daniel M. Ginosar

    2009-01-01

    Fiscal Year 2009 work in the Catalysts project focused on advanced catalysts for the decomposition of sulfuric acid, a reaction common to both the Sulfur-Iodine (S-I) cycle and the Hybrid Sulfur cycle. Prior years effort in this project has found that although platinum supported on titanium oxide will be an acceptable catalyst for sulfuric acid decomposition in the integrated laboratory

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

    PubMed

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

    2010-10-21

    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

  18. Catalytic performance of Fe3O4-CoO/Al2O3 catalyst in ozonation of 2-(2,4-dichlorophenoxy)propionic acid, nitrobenzene and oxalic acid in water.

    PubMed

    Tong, Shaoping; Shi, Rui; Zhang, Hua; Ma, Chunan

    2010-01-01

    Fe3O4-CoO/Al2O3 catalyst was prepared by incipient wetness impregnation using Fe(NO3)3 x 9H2O and Co(NO3)2 x 6H2O as the precursors, and its catalytic performance was investigated in ozonation of 2-(2,4-dichlorophenoxy)propionic acid (2,4-DP), nitrobenzene and oxalic acid. The experimental results indicated that Fe3O4-CoO/Al2O3 catalyst enabled an interesting improvement of ozonation efficiency during the degradation of each organic pollutant, and the Fe3O4-CoO/Al2O3 catalytic ozonation system followed a radical-type mechanism. The kinetics of ozonation alone and Fe3O4-CoO/Al2O3 catalytic ozonation of three organic pollutants in aqueous solution were discussed under the mere consideration of direct ozone reaction and OH radical reaction to well investigate its performance. In the catalytic ozonation of 2,4-DP, the apparent reaction rate constants (k) were determined to be 1.456 x 10(-2) min(-1) for ozonation alone and 4.740 x 10(-2) min(-1) for O3/Fe3O4-CoO/Al203. And O3/Fe3O4-CoO/Al2O3 had a larger R(ct) (6.614 x 10(-9)) calculated by the relative method than O3 did (1.800 x 10(-9)), showing O3/Fe3O4-CoO/Al2O3 generated more hydroxyl radical. Similar results were also obtained in the catalytic ozonation of nitrobenzene and oxalic acid. The above results demonstrated that the catalytic performance of Fe3O4-CoO/Al2O3 in ozonation of studied organic substance was universal to a certain degree. PMID:21235195

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

    PubMed Central

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

    2014-01-01

    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 have led to the synthesis of amino acid derivatives of [Ni(P2RN2R?)2]2+ complexes, [Ni(P2CyN2Amino?acid)2]2+ (CyAA). It is shown that these CyAA derivatives can catalyze fully reversible H2 production/oxidation at rates approaching those of hydrogenase enzymes. The reversibility is achieved in acidic aqueous solutions (pH = 0–6), 1 atm 25% H2/Ar, and elevated temperatures (tested from 298 to 348 K) for the glycine (CyGly), arginine (CyArg), and arginine methyl ester (CyArgOMe) derivatives. As expected for a reversible process, the catalytic activity is dependent upon H2 and proton concentrations. CyArg is significantly faster in both directions (?300 s?1 H2 production and 20 s?1 H2 oxidation; pH = 1, 348 K, 1 atm 25% H2/Ar) than the other two derivatives. The slower turnover frequencies for CyArgOMe (35 s?1 production and 7 s?1 oxidation under the same conditions) compared with 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) suggests that the additional structural features imparted by the guanidinium groups facilitate fast and reversible H2 addition/release. These observations demonstrate that outer coordination sphere amino acids work in synergy with the active site and can play an important role for synthetic molecular electrocatalysts, as has been observed for the protein scaffold of redox active enzymes. PMID:25368196

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

    SciTech Connect

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

    1999-08-01

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

  1. Naturally occurring alkaline amino acids function as efficient catalysts on Knoevenagel condensation at physiological pH: a mechanistic elucidation.

    PubMed

    Li, Weina; Fedosov, Sergey; Tan, Tianwei; Xu, Xuebing; Guo, Zheng

    2014-05-01

    To maintain biological functions, thousands of different reactions take place in human body at physiological pH (7.0) and mild conditions, which is associated with health and disease. Therefore, to examine the catalytic function of the intrinsically occurring molecules, such as amino acids at neutral pH, is of fundamental interests. Natural basic ?-amino acid of L-lysine, L-arginine, and L-histidine neutralized to physiological pH as salts were investigated for their ability to catalyze Knoevenagel condensation of benzaldehyde and ethyl cyanoacetate. Compared with their free base forms, although neutralized alkaline amino acid salts reduced the catalytic activity markedly, they were still capable to perform an efficient catalysis at physiological pH as porcine pancreatic lipase (PPL), one of the best enzymes that catalyze Knoevenagel condensation. In agreement with the fact that the three basic amino acids were well neutralized, stronger basic amino acid Arg and Lys showed more obvious variation in NH bend peak from the FTIR spectroscopy study. Study of ethanol/water system and quantitative kinetic analysis suggested that the microenvironment in the vicinity of amino acid salts and protonability/deprotonability of the amine moiety may determine their catalytic activity and mechanism. The kinetic study of best approximation suggested that the random binding might be the most probable catalytic mechanism for the neutralized alkaline amino acid salt-catalyzed Knoevenagel condensation. PMID:24682854

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

    PubMed

    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

    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

  3. Bifunctional TiO2 Catalysts for Efficient Cr(VI) Photoreduction Under Solar Light Irradiation Without Addition of Acids

    NASA Astrophysics Data System (ADS)

    Shi, Fu-cheng; Wang, Wen-dong; Huang, Wei-xin

    2012-04-01

    Bifunctional TiO2 photocatalysts co-doped with nitrogen and sulfur were prepared by the controlled thermal decomposition of ammonium titanyl sulfate precursor. They have both photocatalytic activity and Brønsted acidity, and thus are active in the photoreduction of Cr(VI) under solar light irradiation without the addition of acids. The activity is superior to that of Degussa P25 in the acidified suspension at the same pH adjusted by H2SO4.

  4. 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

    Li, Yang

    2011-01-01

    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

  5. 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)

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

    2014-06-01

    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.

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

    Microsoft Academic Search

    George J. Piazza; Harold M. Farrell

    1991-01-01

    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.

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

    DOEpatents

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

    1986-01-01

    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.

  8. omega-Amino acid:pyruvate transaminase from Alcaligenes denitrificans Y2k-2: a new catalyst for kinetic resolution of beta-amino acids and amines.

    PubMed

    Yun, Hyungdon; Lim, Seongyop; Cho, Byung-Kwan; Kim, Byung-Gee

    2004-04-01

    Alcaligenes denitrificans Y2k-2 was obtained by selective enrichment followed by screening from soil samples, which showed omega-amino acid:pyruvate transaminase activity, to kinetically resolve aliphatic beta-amino acid, and the corresponding structural gene (aptA) was cloned. The gene was functionally expressed in Escherichia coli BL21 by using an isopropyl-beta-D-thiogalactopyranoside (IPTG)-inducible pET expression system (9.6 U/mg), and the recombinant AptA was purified to show a specific activity of 77.2 U/mg for L-beta-amino-n-butyric acid (L-beta-ABA). The enzyme converts various beta-amino acids and amines to the corresponding beta-keto acids and ketones by using pyruvate as an amine acceptor. The apparent K(m) and V(max) for L-beta-ABA were 56 mM and 500 U/mg, respectively, in the presence of 10 mM pyruvate. In the presence of 10 mM L-beta-ABA, the apparent K(m) and V(max) for pyruvate were 11 mM and 370 U/mg, respectively. The enzyme exhibits high stereoselectivity (E > 80) in the kinetic resolution of 50 mM D,L-beta-ABA, producing optically pure D-beta-ABA (99% enantiomeric excess) with 53% conversion. PMID:15066855

  9. Influence of nature\\/concentration of halide promoters and oxidation state on the direct oxidation of H 2 to H 2O 2 over Pd\\/ZrO 2 catalysts in aqueous acidic medium

    Microsoft Academic Search

    V. R. Choudhary; C. Samanta; T. V. Choudhary

    2007-01-01

    The nature\\/concentration of halide promoters and influence of the Pd oxidation state on the promoted reaction system has been investigated on the direct H2O2 process over a 2.5wt.% Pd\\/ZrO2 catalyst in an aqueous acidic reaction medium. The oxidation state of Pd had a profound influence on the H2O2 synthesis process. Interestingly, the nature of the halide determined the magnitude\\/type of

  10. The new esterification catalysts and the nature of reactions proceeding at esterification of synthetic naphthenic acids in their presence

    Microsoft Academic Search

    A. H. Azizov; G. I. Amanullayeva; R. V. Aliyeva; B. M. Aliyev; N. R. Bektashi

    2011-01-01

    There have been synthesized the novel sulfocationites on the basis of graft copolymers of polystyrene with oligostyrene, and their metal-polymer composites based on the titanium-containing compound with the grafted ionic-liquid type ligands. Esterifacation reaction of synthetic naphthen acid (SNA) fraction with heptyl alcohol as a model reaction has been investigated in the presence of the novel sulfocationites and Ti-containing metal-polymer

  11. Influence of Au contents of AuPt anode catalyst on the performance of direct formic acid fuel cell

    Microsoft Academic Search

    Jae Kwang Lee; Jaeyoung Lee; Jonghee Han; Tae-Hoon Lim; Yung-Eun Sung; Yongsug Tak

    2008-01-01

    We reported that various compositions of AuPt nanoparticles synthesized as an anode material for formic acid fuel cell were investigated. Its surface characteristics were systematically analyzed using XRD and TEM and anodic electrocatalytic activity was studied using a linear sweep voltammetry technique in 0.5M H2SO4+1M HCOOH. In addition, the voltage–current curve and power density of home-made AuPt-based membrane–electrode-assembly (MEA) and

  12. Mathematical Modeling of the Poly(lactic acid) Ring-Opening Polymerization using Stannous Octoate as a Catalyst

    Microsoft Academic Search

    Rajeev Mehta; Vineet Kumar; S. N. Upadhyay

    2007-01-01

    A novel and simple mathematical model to get the polymerization rate constants for the ring-opening polymerization of poly(lactic acid) is described. The model permits evaluation of the degree of polymerization versus monomer-to-initiator ratio curves. The predicted results are compared with the reported experimental data. The value of rate constants for initiation, propagation, and different modes of termination, are also obtained.

  13. Preparation of fatty acid methyl esters for gas-chromatographic analysis of lipids in biological materials

    Microsoft Academic Search

    Ke-Shun Liu

    1994-01-01

    Theoretically, preparation of fatty acid methyl esters (FAMEs) deals with reversible chemical reactions in a complex system.\\u000a Methodologically, there are numerous ways, generally characterized by the type of catalysts used and steps involved. Although\\u000a there are more than a half dozen common catalysts, the majority fall into either acidic (HCl, H2SO4 and BF3) or alkaline types (NaOCH3, KOH and NaOH),

  14. Synthesis of ferromagnetic nanoparticles, formic acid oxidation catalyst nanocomposites, and late-transition metal-boride intermetallics by unique synthetic methods and single-source precursors

    NASA Astrophysics Data System (ADS)

    Wellons, Matthew S.

    The design, synthesis, and characterization of magnetic alloy nanoparticles, supported formic acid oxidation catalysts, and superhard intermetallic composites are presented. Ferromagnetic equatomic alloy nanoparticles of FePt, FePd, and CoPt were synthesized utilizing single-source heteronuclear organometallic precursors supported on an inert water-soluble matrix. Direct conversion of the precursor-support composite to supported ferromagnetic nanoparticles occurs under elevated temperatures and reducing conditions with metal-ion reduction and minimal nanoparticle coalescence. Nanoparticles were easily extracted from the support by addition of water and characterized in structure and magnetic properties. Palladium and platinum based nanoparticles were synthesized with microwave-based and chemical metal-ion reduction strategies, respectively, and tested for catalytic performance in a direct formic acid fuel cell (DFAFC). A study of palladium carbide nanocomposites with various carbonaceous supports was conducted and demonstrated strong activity comparable to commercially available palladium black, but poor catalytic longevity. Platinum-lead alloy nanocomposites synthesized with chemical reduction and supported on Vulcan carbon demonstrated strong activity, excellent catalytic longevity, and were subsequently incorporated into a prototype DFAFC. A new method for the synthesis of superhard ceramics on polymer substrates called Confined Plasma Chemical Deposition (CPCD) was developed. The CPCD method utilizes a tuned Free Electron Laser to selectively decompose the single-source precursor, Re(CO)4(B3H8), in a plasma-like state resulting in the superhard intermetallic ReB2 deposited on polymer substrates. Extension of this method to the synthesis of other hard of superhard ceramics; WB4, RuB2, and B4C was demonstrated. These three areas of research show new synthetic methods and novel materials of technological importance, resulting in a substantial advance in their respective fields.

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

    SciTech Connect

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

    2014-11-18

    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.

  16. Fundamental studies of hydrogen chemisorption on supported monometallic and bimetallic catalysts using microcalorimetry

    SciTech Connect

    Narayan, R.L.

    1997-06-24

    Highly dispersed transition metal catalysts are used in numerous commercial processes such as hydrocarbon conversions. For example, the use of Pt supported on acidic alumina or silica-alumina for reforming of naphtha in the production of gasoline is well known. Another use of supported catalysts is in automobile emission control where supported Pt-Rh bimetallic catalysts are used. Supported Ru can be used in Fischer-Tropsch synthesis for the production of higher hydrocarbons from synthesis gas. While many of these catalyst systems have been in commercial operation for several decades there is still a lack of consensus regarding the exact role of the catalyst on a molecular level. In particular, little is known about the mechanisms operating on the catalyst surface at the high pressure and high temperature conditions typically used in commercial operations. This report contains the general introduction and conclusions and an appendix containing the operating instructions for a microcalorimeter. Three chapters have been processed separately. They are: the effect of K on the kinetics and thermodynamics of hydrogen adsorption on Ru/SiO{sub 2}; hydrogen adsorption states on silica supported Ru-Ag and Ru-Cu bimetallic catalysts investigated via microcalorimetry; a comparative study of hydrogen chemisorption on silica supported Ru, Rh, and Pt.

  17. Aromatization of n-heptane over H-AlMFI, Ga\\/H-AlMFI, H-GaMFI and H-GaAlMFI zeolite catalysts: influence of zeolitic acidity and non-framework gallium

    Microsoft Academic Search

    V. R Choudhary; S. A. R Mulla; S Banerjee

    2003-01-01

    Influence of zeolite acidity (strong acid sites measured in terms of the pyridine chemisorbed at 400 °C) and non-framework Ga-species present in the zeolite channels on the conversion (total and to aromatics) and selectivity in the aromatization of n-heptane at 500 °C over the H-AlMFI (H-ZSM-5), Ga\\/ H-AlMFI, H-GaMFI and H-GaAlMFI zeolite catalysts (GHSV=3400 and 13,600 h?1) has been investigated.

  18. General Roles of Abscisic and Jasmonic Acids in Gene Activation as a Result of Mechanical Wounding

    Microsoft Academic Search

    Thomas Hildmann; Marcus Ebneth; Hugo Peiia-Cortth; Jose J. Sánchez-Serrano; Lothar Willmitzer; Salomti Prat

    1992-01-01

    Exogenous application of abscisic acid (ABA) has been shown to induce a systemic pattern of proteinase inhibitor II (pin2) mRNA accumulation identical to that induced by mechanical wounding. Evidence is presented that the ABA-specific response is not restricted to pin2 genes but appears to,be part of a general reaction to wound stress. Four other wound- induced, ABAresponsive genes that encode

  19. Selective staining of Brønsted acidity in zeolite ZSM-5-based catalyst extrudates using thiophene as a probe.

    PubMed

    Whiting, Gareth T; Meirer, Florian; Valencia, Diego; Mertens, Machteld M; Bons, Anton-Jan; Weiss, Brian M; Stevens, Paul A; de Smit, Emiel; Weckhuysen, Bert M

    2014-10-21

    Optical absorption and confocal fluorescence micro-spectroscopy were applied to investigate Brønsted acidity in millimetre-sized extrudates of Na(H)-ZSM-5 and SiO2 with varying ZSM-5 content. Partially (residual Na present) and fully proton-exchanged extrudates were employed, using thiophene oligomerization as a probe reaction. Time-resolved in situ optical absorption spectra and time dependent DFT calculations revealed several initial reaction pathways during the oligomerization reaction. In particular, it was found that protonated thiophene monomers reacted by either oligomerization (via reaction with un-reacted thiophene monomers) or ring-opening, depending on the Brønsted acid site density in each sample. Moreover, fully-exchanged extrudates not only have significantly higher reactivity than partially-exchanged samples, but they also favour the formation of ring-opening products, that are not formed on the partially-exchanged samples. Confocal fluorescence microscopy was employed to visualise non-invasively in 3D, the heterogeneity and homogeneity of thiophene oligomers on partially- and fully-exchanged extrudates, respectively. Furthermore, it was observed that extrudates with high binder content produce a higher relative amount of conjugated species, related with a higher quantity of available monomer in the binder, which is able to react further with intermediates adsorbed on active sites. Moreover, these conjugated species appear to form near the external surface of ZSM-5 crystals/agglomerates. PMID:25188580

  20. Clays as selective catalysts in organic synthesis

    Microsoft Academic Search

    John M. Adams; Keith Martin; Richard W. McCabe

    1987-01-01

    Suitably modified smectite clays can be very selective catalysts for a wide range of organic reactions. While it has long been known that such materials can act as Bronsted and Lewis acids, it has been shown recently that they are also effective Diels-Alder catalysts. A selection of illustrative reactions is given which emphasises their wide range of use, their selectivity,

  1. The electron is a catalyst

    NASA Astrophysics Data System (ADS)

    Studer, Armido; Curran, Dennis P.

    2014-09-01

    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.

  2. Asymmetric Synthesis of 1,3-Butadienyl-2-carbinols by the Homoallenylboration of Aldehydes with a Chiral Phosphoric Acid Catalyst.

    PubMed

    Huang, Yiyong; Yang, Xing; Lv, Zongchao; Cai, Chen; Kai, Cheng; Pei, Yong; Feng, Yu

    2015-06-15

    Asymmetric C(sp)?C(sp(2) ) bond formation to give enantiomerically enriched 1,3-butadienyl-2-carbinols occurred through a homoallenylboration reaction between a 2,3-dienylboronic ester and aldehydes under the catalysis of a chiral phosphoric acid (CPA). A diverse range of enantiomerically enriched butadiene-substituted secondary alcohols with aryl, heterocyclic, and aliphatic substituents were synthesized in very high yield with high enantioselectivity. Preliminary density functional theory (DFT) calculations suggest that the reaction proceeds via a cyclic six-membered chairlike transition state with essential hydrogen-bond activation in the allene reagent. The catalytic reaction was amenable to the gram-scale synthesis of a chiral alkyl butadienyl adduct, which was converted into an interesting optically pure compound bearing a benzo-fused spirocyclic cyclopentenone framework. PMID:25939725

  3. 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...

  4. Resin catalysts and method of preparation

    DOEpatents

    Smith, L.A. Jr.

    1986-12-16

    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.

  5. Binary ferrihydrite catalysts

    DOEpatents

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

    1996-12-03

    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.

  6. Topologically unique heterometallic Cu(II)/Li coordination polymers self-assembled from N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid biobuffer: versatile catalyst precursors for mild hydrocarboxylation of alkanes to carboxylic acids.

    PubMed

    Kirillova, Marina V; Kirillov, Alexander M; Martins, André N C; Graiff, Claudia; Tiripicchio, Antonio; Pombeiro, Armando J L

    2012-05-01

    The facile aqueous medium reactions of copper(II) nitrate with BES biobuffer [(HOCH(2)CH(2))(2)N(CH(2)CH(2)SO(3)H), hereinafter referred as H(3)bes] in the presence of various benzenecarboxylic acids [benzoic (Hba), 3-hydroxybenzoic (Hhba), and 3,5-dihydroxybenzoic (Hdhba) acid] and lithium hydroxide gave rise to the self-assembly generation of three new heterometallic Cu(II)/Li materials, [Li(H(2)O)(4)][Cu(4)(?(2)-Hbes)(4)(?(2)-ba)]·H(2)O (1) and [Cu(4)(?(3)-Hbes)(4)(L){Li(H(2)O)(2)}](n)·3nH(2)O {L = ?(2)-hba (2) and ?(2)-dhba (3)}. They were isolated as air-stable crystalline solids and fully characterized by infrared (IR) and UV-vis spectroscopy and electrospray ionization (ESI)-MS(±), elemental, thermal, and single-crystal X-ray diffraction analyses. The latter revealed that 1-3 have comparable packing patterns and unit cell parameters, being composed of similar [Cu(4)(?-Hbes)(4)(?-carboxylate)](-) cores and [Li(H(2)O)(4)](+) cations (in 1) or [?-Li(H(2)O)(2)](+) groups (in 2 and 3), which are arranged into discrete 0D aggregates in 1 or infinite 3D noninterpenetrating metal-organic networks in 2 and 3. The topological analysis of the coordination polymers 2 and 3 disclosed the trinodal 3,3,4-connected underlying nets with an unprecedented topology defined by the point symbol of (4.6.8)(4)(4(2).6)(2)(6(2).16(2).18(2)), further simplification of which resulted in the binodal 4,4-connected nets with the pts (PtS) topology. Apart from representing very rare examples of coordination compounds derived from H(3)bes, 1-3 feature solubility in water and were applied as efficient and versatile catalyst precursors for the mild (60 °C) single-pot hydrocarboxylation, by CO and H(2)O, of various gaseous, linear, and cyclic C(n) (n = 2-9) alkanes into the corresponding C(n+1) carboxylic acids, in H(2)O/MeCN medium under homogeneous conditions and in the presence of potassium peroxodisulfate. Total yields (based on alkane) of carboxylic acids up to 78% were achieved, which are remarkable in the field of alkane functionalization under mild conditions, especially for a C-C bond formation reaction in aqueous acid-solvent-free medium. PMID:22482365

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

    PubMed

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

    2014-06-24

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

  8. Introduction of poly(4-vinylpyridinium) perchlorate as a new, efficient, and versatile solid acid catalyst for one-pot synthesis of substituted coumarins under ultrasonic irradiation.

    PubMed

    Khaligh, Nader Ghaffari; Shirini, Farhad

    2013-01-01

    Poly(4-vinylpyridinium) perchlorate, is a supported, recyclable, eco-benign catalyst for synthesis of substituted coumarins via Pechmann reaction using ultrasound irradiation at room temperature and neat condition in high yields with short reaction times. The catalyst was studied by FT-IR, X-ray diffraction, scanning electron microscope, thermo-gravimetric and energy dispersion X-ray analyses. All the products were extensively characterized by (1)H NMR, FT-IR, MS and melting point analyses. This methodology offers momentous improvements over various options for the synthesis of coumarins with regard to yield of products, simplicity in operation and green aspects by avoiding toxic catalysts and solvents. Further, the catalyst can be reused and recovered for several times without loss of activity. PMID:22922036

  9. Generalized chemical route to develop fatty acid capped highly dispersed semiconducting metal sulphide nanocrystals

    SciTech Connect

    Patel, Jayesh D. [Center for Applied Research on Polymers and Composites, CREPEC, Quebec (Canada) [Center for Applied Research on Polymers and Composites, CREPEC, Quebec (Canada); Chemical Engineering Department, University of Laval, Quebec, QC, G1K 7P4 (Canada); Mighri, Frej, E-mail: Frej.Mighri@gch.ulaval.ca [Center for Applied Research on Polymers and Composites, CREPEC, Quebec (Canada) [Center for Applied Research on Polymers and Composites, CREPEC, Quebec (Canada); Chemical Engineering Department, University of Laval, Quebec, QC, G1K 7P4 (Canada); Ajji, Abdellah [Center for Applied Research on Polymers and Composites, CREPEC, Quebec (Canada) [Center for Applied Research on Polymers and Composites, CREPEC, Quebec (Canada); Chemical Engineering Department, Ecole Polytechnique, C.P. 6079, Succ. Centre-Ville Montreal, QC, H3C 3A7 (Canada)

    2012-08-15

    Highlights: ? Chemical route for the synthesis of OA-capped CdS, ZnS and PbS at low temperature. ? Synthesized nanocrystals via thermolysis of their metal–oleate complexes. ? Size quantized nanocrystals were highly dispersed and stable at room temperature. -- Abstract: This work deals with the synthesis of highly dispersed semiconducting nanocrystals (NCs) of cadmium sulphide (CdS), zinc sulphide (ZnS) and lead sulphide (PbS) through a simple and generalized process using oleic acid (OA) as surfactant. To synthesize these NCs, metal–oleate (M–O) complexes were obtained from the reaction at 140 °C between metal acetates and OA in hexanes media. Subsequently, M–O complexes were sulphurized using thioacetamide at the same temperature. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) characterizations show that the synthesized products are of nanoscale-size with highly crystalline cubic phase. The optical absorption of OA-capped metal sulphide NCs confirms that their size quantization induced a large shift towards visible region. Photoluminescence (PL) spectrum of CdS NCs shows a broad band-edge emission with shallow and deep-trap emissions, while PL spectrum of ZnS NCs reveals a broad emission due to defects states on the surface. The thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy indicate that fatty acid monolayers were bound strongly on the nanocrystal surface as a carboxylate and the two oxygen atoms of the carboxylate were coordinated symmetrically to the surface of the NCs. The strong binding between the fatty acid and the NCs surface enhances the stability of NCs colloids. In general, this generalized route has a great potential in developing nanoscale metal sulphides for opto-electronic devices.

  10. Effect of catalyst concentration and simulation of precipitation processes on liquid-phase catalytic oxidation of p-xylene to terephthalic acid

    Microsoft Academic Search

    A. Cincotti; R. Orrù; A. Broi; G. Cao

    1997-01-01

    The influence of catalyst concentration, i.e. cobalt naphthenate, on product distribution and kinetic constants of the lumped kinetic scheme of liquid-phase p-xylene oxidation proposed in previous works (cf. Cao et al., 1994a, b) is investigated. The experiments involving various levels of catalyst concentrations (from 1.67 to 33.3 × 10?4 mol\\/kgl) are conducted in an isothermal semi-batch oxidation reactor where both

  11. Catalyst for cracking kerosene

    SciTech Connect

    Hsie, C. H.

    1985-06-04

    A catalyst capable of cracking kerosene under lower pressure and temperature comprising kerosene; metal powder mixture of chromium powder, copper powder, lead powder, zinc powder, nickel powder, manganese powder in an amount of 12 to 13 parts by weight per 100 parts by weight of said kerosene; sulfuric acid in an amount of 15 to 30 parts by weight per 100 parts by weight of said kerosene; inorganic powder mixture of aluminum oxide powder, serpentine powder, alum powder, magnesium oxide powder, limestone powder, slake lime powder, silica powder, and granite powder in an amount of 150 to 170 parts by weight per 100 parts by weight of said kerosene.

  12. Asymmetric alkynylation of seven-membered cyclic imines by combining chiral phosphoric acids and Ag(I) catalysts: synthesis of 11-substituted-10,11-dihydrodibenzo[b,f][1,4]oxazepine derivatives.

    PubMed

    Ren, Yuan-Yuan; Wang, You-Qing; Liu, Shuang

    2014-12-01

    Asymmetric alkynylation of seven-membered cyclic imine dibenzo[b,f][1,4]oxazepines is successfully achieved by combining chiral phosphoric acid and Ag(I) catalysts. Various arylacetylenes, conjugated enynes, and terminal 1,3-diynes are good substrates for this reaction, and aliphatic hexyne is also a suitable donor at elevated temperature. Optimization of this approach has provided a facile method to synthesize optically active 11-substituted-10,11-dihydrodibenzo[b,f][1,4]oxazepine derivatives containing a carbon-carbon triple bond with 63-99% ee. Subsequent transformations of the carbon-carbon triple bond for the heterocyclic products have been disclosed. PMID:25375832

  13. Cr(III)-containing Fe3O4/mercaptopropanoic acid-poly(2-hydroxyethyl acrylate) nanocomposite: a highly active magnetic catalyst in solvent-free aerobic oxidation of alcohols.

    PubMed

    Zamani, Farzad; Hosseini, Seyed Mohsen; Kianpour, Sahar

    2014-03-01

    In this study, polymer-grafted magnetic nanoparticles containing chromium(iii) ions incorporated onto Fe3O4/mercaptopropanoic acid-poly(2-hydroxyethyl acrylate) (Fe3O4/MPA-PHEA-Cr) was prepared via a simple and in situ method. The obtained magnetic nanocomposite exhibited a high catalytic activity and excellent selectivity in the aerobic oxidation of alcohols under solvent-free conditions. The magnetic catalyst could also be separated by an external magnet and reused seven times without any significant loss of activity/selectivity. PMID:24413435

  14. A General, Efficient and Functional-Group-Tolerant Catalyst System for the Palladium-Catalyzed Thioetherification of Aryl Bromides and Iodides

    PubMed Central

    Fernández-Rodríguez, Manuel A.; Hartwig, John F.

    2010-01-01

    The cross-coupling reaction of aryl bromides and iodides with aliphatic and aromatic thiols catalyzed by palladium complexes of the bisphosphine ligand CyPF-tBu (1) is reported. Reactions occur in excellent yields, broad scope, high tolerance of functional groups and with turnover numbers that exceed those of previous catalysts by two or three orders of magnitude. These couplings of bromo- and iodoarenes are more efficient than the corresponding reactions of chloroarenes and could be conducted with less catalyst loading and/or milder reaction conditions. Consequently, limitations regarding scope and functional group tolerance previously reported in the coupling of aryl chlorides are now overcome. PMID:19154131

  15. Waste catalysts for waste polymer.

    PubMed

    Salmiaton, A; Garforth, A

    2007-01-01

    Catalytic cracking of high-density polyethylene (HDPE) over fluid catalytic cracking (FCC) catalysts (1:6 ratio) was carried out using a laboratory fluidized bed reactor operating at 450 degrees C. Two fresh and two steam deactivated commercial FCC catalysts with different levels of rare earth oxide (REO) were compared as well as two used FCC catalysts (E-Cats) with different levels of metal poisoning. Also, inert microspheres (MS3) were used as a fluidizing agent to compare with thermal cracking process at BP pilot plant at Grangemouth, Scotland, which used sand as its fluidizing agent. The results of HDPE degradation in terms of yield of volatile hydrocarbon product are fresh FCC catalysts>steamed FCC catalysts approximately used FCC catalysts. The thermal cracking process using MS3 showed that at 450 degrees C, the product distribution gave 46 wt% wax, 14% hydrocarbon gases, 8% gasoline, 0.1% coke and 32% nonvolatile product. In general, the product yields from HDPE cracking showed that the level of metal contamination (nickel and vanadium) did not affect the product stream generated from polymer cracking. This study gives promising results as an alternative technique for the cracking and recycling of polymer waste. PMID:17084608

  16. Economic effects of catalyst deactivation during VOC oxidation

    Microsoft Academic Search

    Sanjay K. Agarwal; James J. Spivey

    1993-01-01

    Catalytic oxidation of volatile organic compounds (VOCs) is widely used for air pollution control. While catalytic oxidation offers several advantages over alternative processes, the catalyst can deactivate over time, resulting in changes in activity and selectivity with time-on-stream. To maintain constant catalyst activity, required for environmental regulations, the temperature is generally increased gradually to compensate for catalyst deactivation. This results

  17. Enhancement of water-gas shift reaction efficiency: catalysts and the catalyst bed arrangement

    NASA Astrophysics Data System (ADS)

    Baronskaya, Natal'ya A.; Minyukova, Tat'yana P.; Khassin, Aleksandr A.; Yurieva, Tamara M.; Parmon, Valentin N.

    2010-12-01

    The results of studies devoted to the search for catalysts of water-gas shift (WGS) reaction that are highly active in a wide temperature interval are generalized. New compositions based on traditional and alternative, as regards the chemical composition, catalysts of high- and low-temperature WGS reaction are considered in detail. The single-stage arrangement of WGS reaction ensuring small temperature gradients in the radial direction of the catalyst bed are discussed.

  18. A facile and general approach for the direct fabrication of 3D, vertically aligned carbon nanotube array/transition metal oxide composites as non-Pt catalysts for oxygen reduction reactions.

    PubMed

    Yang, Zhi; Zhou, Xuemei; Jin, Zhiping; Liu, Zheng; Nie, Huagui; Chen, Xi'an; Huang, Shaoming

    2014-05-21

    A simple and effective strategy involving nebulized ethanol assisted infiltration for the general synthesis of 3D structure-based vertically aligned carbon nanotube arrays (VACNTs) uniformly and deeply decorated with various transition-metal oxide (MOs) has been developed. Furthermore, it is demonstrated that the 3D structure-based VACNTs with decorated MnO2 can exhibit superior electrocatalytic oxygen reduction reaction activity, long-term stability, and an excellent resistance to crossover effects compared to the commercial Pt/C catalyst. PMID:24616041

  19. Preparation of Hydrotreating catalyst from spent catalyst

    SciTech Connect

    Gardner, L.E.; Kidd, D.R.

    1990-01-01

    This patent describes a process for preparing an active hydrotreating catalyst composition from a spent hydrotreating catalyst composition. The process comprising the steps of: grinding a substantially dry spent hydrotreating composition; mixing the ground spent hydrotreating catalyst composition with alumina; shaping the mixture into compacted particles comprising the ground spent hydrotreating catalyst composition and the alumina; and heating the compacted particles in a free oxygen containing gas to a temperature in the range of from about 700{degrees} to about 1000{degrees}F, under such conditions as to substantially convert the solid carbonaceous deposits to carbon oxides, and to obtain an active hydrotreating catalyst composition.

  20. A conserved GTPase-containing complex is required for intracellular sorting of the general amino-acid permease in yeast

    Microsoft Academic Search

    Minggeng Gao; Chris A. Kaiser

    2006-01-01

    The Saccharomyces cerevisiae general amino-acid permease, Gap1p, is a model for membrane proteins that are regulated by intracellular sorting according to physiological cues set by the availability of amino acids. Here, we report the identification of a conserved sorting complex for Gap1p, named the GTPase-containing complex for Gap1p sorting in the endosomes (GSE complex), which is required for proper sorting

  1. Attrition resistant gamma-alumina catalyst support

    DOEpatents

    Singleton, Alan H.; Oukaci, Rachid; Goodwin, James G.

    2006-03-14

    A .gamma.-alumina catalyst support having improved attrition resistance produced by a method comprising the steps of treating a particulate .gamma.-alumina material with an acidic aqueous solution comprising water and nitric acid and then, prior to adding any catalytic material thereto, calcining the treated .gamma.-alumina.

  2. Synthesis and Understanding of Novel Catalysts

    SciTech Connect

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

    2013-07-09

    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.

  3. Fluidised bed catalytic pyrolysis of scrap tyres: influence of catalyst:tyre ratio and catalyst temperature.

    PubMed

    Williams, Paul T; Brindle, Alexander J

    2002-12-01

    Pyrolysis with on-line Zeolite catalysis of scrap tyres was undertaken in a fluidised bed reactor with the aim of maximising the production of higher value single ring aromatic hydrocarbons in the derived oil. Experiments were carried out in relation to the ratio of the catalyst to tyre feedstock and the temperature of the catalyst bed. Two Zeolite catalysts were examined, a Y-type Zeolite catalyst and Zeolite ZSM-5 catalyst of differing pore size and surface activity. The composition of the oils derived from the uncatalysed fluidised bed pyrolysis of tyres showed that benzene concentration was 0.2 wt%, toluene concentration was 0.8 wt%, o-xylene was 0.3 wt%, m/p-xylenes were 1.8 wt% and limonene was 4.3 wt%. Benzene, toluene and xylenes present in the oils showed a significant increase in the presence of both of the catalysts. The maximum concentrations of these chemicals for the Y-Zeolite (CBV-400) catalyst was 1 wt% for benzene, 8wt% for toluene, 3 wt% for o-xylene and 8.5 wt% for m/p-xylenes, produced at a catalyst:tyre ratio of 1.5. There was less influence of catalyst temperature on the yield of benzene, toluene and xylenes, however, increasing the temperature of the catalyst resulted in a marked decrease in limonene concentration. The Y-type Zeolite catalyst produced significantly higher concentrations of benzene, toluene and xylenes which was attributed to the larger pore size and higher surface acidity of the Y-Zeolite catalyst compared to the Zeolite ZSM-5 catalyst. PMID:12549667

  4. Antimony promoted bismuth cerium molybdate catalysts

    SciTech Connect

    Brazdil, J.F.; Glaeser, L.C.; Grasselli, R.K.

    1990-05-01

    This patent describes an improvement in antimony-promoted bismuth cerium molybdate whereby the tendency of the catalyst to lose efectiveness over time is significantly reduced. This patent describes new catalysts which are also useful in other oxidation-type reactions such as the oxidation of acrolein and methacrolein to produce the corresponding unsaturated aldehydes and acids and the oxydehydrogenation of various olefins such as isoamylenes to produce the corresponding diolefins such as isoprene.

  5. Esterification by the Plasma Acidic Water: Novel Application of Plasma Acid

    NASA Astrophysics Data System (ADS)

    Gu, Ling

    2014-03-01

    This work explores the possibility of plasma acid as acid catalyst in organic reactions. Plasma acidic water was prepared by dielectric barrier discharge and used to catalyze esterification of n-heptanioc acid with ethanol. It is found that the plasma acidic water has a stable and better performance than sulfuric acid, meaning that it is an excellent acid catalyst. The plasma acidic water would be a promising alternative for classic mineral acid as a more environment friendly acid.

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

    Microsoft Academic Search

    Beyhan Erdem; Ali Kara

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

  7. The role of surface oxygenated-species and adsorbed hydrogen in the oxygen reduction reaction (ORR) mechanism and product selectivity on Pd-based catalysts in acid media.

    PubMed

    Rahul, R; Singh, R K; Bera, B; Devivaraprasad, R; Neergat, M

    2015-06-01

    Oxygen reduction reaction (ORR) is investigated on bulk PdO-based catalysts (oxides of Pd and Pd3Co) in oxygen-saturated 0.1 M HClO4 to establish the role of surface oxides and adsorbed hydrogen in the activity and product selectivity (H2O/H2O2). The initial voltammetric features suggest that the oxides are inactive toward ORR. The evolution of the ORR voltammograms and potential-dependent H2O2 generation features on the PdO catalyst suggest gradual and parallel in situ reduction of the bulk PdO phase below ?0.4 V in the hydrogen underpotential deposition (Hupd) region; the reduction of the bulk PdO catalyst is confirmed from the X-ray photoelectron spectra (XPS) and X-ray diffraction (XRD) patterns. The potential-dependent H2O2 generation features originate due to the presence of surface oxides and adsorbed hydrogen; this is further confirmed using halide ions (Cl(-) and Br(-)) and peroxide as the external impurities. PMID:25991432

  8. Ruthenium-based olefin metathesis catalysts bearing pH-responsive ligands: External control of catalyst solubility and activity

    NASA Astrophysics Data System (ADS)

    Balof, Shawna Lynn

    2011-12-01

    Sixteen novel, Ru-based olefin metathesis catalysts bearing pH responsive ligands were synthesized. The pH-responsive groups employed with these catalysts included dimethylamino (NMe2) modified NHC ligands as well as N-donor dimethylaminopyridine (DMAP) and 3-(o-pyridyl)propylidene ligands. These pH-responsive ligands provided the means by which the solubility and/or activity profiles of the catalysts produced could be controlled via acid addition. The main goal of this dissertation was to design catalyst systems capable of performing ring opening metathesis (ROMP) and ring closing metathesis (RCM) reactions in both organic and aqueous media. In an effort to quickly gain access to new catalyst structures, a template synthesis for functionalized NHC ligand precursors was designed, in addition to other strategies, to obtain ligand precursors with ancillary NMe2 groups. Kinetic studies for the catalysts produced from these precursors showed external control of catalyst solubility was afforded via protonation of the NMe2 groups of their NHC ligands. Additionally, this protonation afforded external control of catalyst propagation rates for several catalysts. This is the first known independent external control for the propagation rates of ROMP catalysts. The incorporation of pH-responsive N-donor ligands into catalyst structures also provided the means for the external control of metathesis activity, as the protonation of these ligands resulted in an increased initiation rate based on their fast and irreversible dissociation from the metal center. The enhanced external control makes these catalysts applicable to a wide range of applications, some of which have been explored by us and/or through collaboration. Three of the catalysts designed showed remarkable metathesis activity in aqueous media. These catalysts displayed comparable RCM activity in aqueous media to a class of water-soluble catalysts reported by Grubbs et al., considered to be the most active catalyst for aqueous olefin metathesis reactions. In ROMP reactions these particular catalysts dramatically outperformed the literature catalysts, accomplishing ROMP full conversion rates within 15 minutes compared to several hours observed with the literature catalyst. These catalysts were also able to accomplish these reactions at lower catalyst loadings than ever reported with the literature catalyst, making them the most active aqueous olefin metathesis catalysts to date.

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

    PubMed Central

    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

    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

  10. Kinetics and mechanism of the interaction of phenol with ethylene oxide in the presence of ion-exchange resin wofatit SBW as catalyst

    SciTech Connect

    Boeva, R.; Markov, K.; Kotov, S.

    1980-04-01

    The reaction of ethylene oxide with phenol, generally catalyzed with homogeneous catalyst in the production of detergents, was studied with an ion-exchange resin catalyst, i.e., the hydroxyl form of a microreticular gel containing trimethylammonium active groups. The reaction produced only phenoxyethanol. At sufficient excess of ethylene oxide (at least 2.5:1 mole ratio), the reaction was zero order in ethylene oxide, zero order in phenol, proportional to the catalyst amount, and had an activation energy of 17.6 kcal/mole. Under reaction conditions, a catalytically active phenolate counterion apparently formed at the resin, which was not removed by washing with benzene or ether, but was removed by dilute hydrochloric acid. These results suggested that the mechanism and kinetics were the same as with homogeneous basic nucleophilic catalysts.

  11. General method for purification of ?-amino acid-n-carboxyanhydrides using flash chromatography.

    PubMed

    Kramer, Jessica R; Deming, Timothy J

    2010-12-13

    We describe the application of flash column chromatography on silica gel as a rapid and general method to obtain pure ?-amino acid-N-carboxyanhydride (NCA) monomers, the widely used precursors for the synthesis of polypeptides, without the need for recrystallization. This technique was effective at removing all common impurities from NCAs and was found to work for a variety of NCAs, including those synthesized using different routes, as well as those bearing either hydrophilic or hydrophobic side chains. All chromatographed NCAs required no further purification and could be used directly to form high molecular weight polypeptides. This procedure is especially useful for the preparation of highly functional and low melting NCAs that are difficult to crystallize and, consequently, to polymerize. This method solves many long-standing problems in NCA purification and provides rapid access to NCAs that were previously inaccessible in satisfactory quality for controlled polymerization. This method is also practical in that it requires less time than recrystallization and often gives NCAs in improved yields. PMID:21047056

  12. Alkali-Resistant Mechanism of a Hollandite DeNOx Catalyst.

    PubMed

    Hu, Pingping; Huang, Zhiwei; Gu, Xiao; Xu, Fei; Gao, Jiayi; Wang, Yue; Chen, Yaxin; Tang, Xingfu

    2015-06-01

    A thorough understanding of the deactivation mechanism by alkalis is of great importance for rationally designing improved alkali-resistant deNOx catalysts, but a traditional ion-exchange mechanism cannot often accurately describe the nature of the deactivation, thus hampering the development of superior catalysts. Here, we establish a new exchange-coordination mechanism on the basis of the exhaustive study on the strong alkali resistance of a hollandite manganese oxide (HMO) catalyst. A combination of isothermal adsorption measurements of ammonia with X-ray absorption near-edge structure spectra and X-ray photoelectron spectra reveals that alkali metal ions first react with protons from Brønsted acid sites of HMO via the ion exchange. Synchrotron X-ray diffraction patterns and extended X-ray absorption fine structure spectra coupled with theoretical calculations demonstrate that the exchanged alkali metal ions are subsequently stabilized at size-suitable cavities in the HMO pores via a coordination model with an energy savings. This exchange-coordination mechanism not only gives a wholly convincing explanation for the intrinsic nature of the deactivation of the reported catalysts by alkalis but also provides a strategy for rationally designing improved alkali-resistant deNOx catalysts in general. PMID:25941972

  13. The general amino acid control pathway regulates mTOR and autophagy during serum/glutamine starvation.

    PubMed

    Chen, Rui; Zou, Yilong; Mao, Dongxue; Sun, Daxiao; Gao, Guanguang; Shi, Jingwen; Liu, Xiaoqing; Zhu, Chen; Yang, Mingyu; Ye, Wanlu; Hao, Qianqian; Li, Ruiqiang; Yu, Li

    2014-07-21

    Organisms have evolved elaborate mechanisms to adjust intracellular nutrient levels in response to fluctuating availability of exogenous nutrients. During starvation, cells can enhance amino acid uptake and synthesis through the general amino acid control (GAAC) pathway, whereas nonessential cellular contents are recycled by autophagy. How these two pathways are coordinated in response to starvation is currently unknown. Here we show that the GAAC pathway couples exogenous amino acid availability with autophagy. Starvation caused deactivation of mTOR, which then activated autophagy. In parallel, serum/glutamine starvation activated the GAAC pathway, which up-regulated amino acid transporters, leading to increased amino acid uptake. This elevated the intracellular amino acid level, which in turn reactivated mTOR and suppressed autophagy. Knockdown of activating transcription factor 4, the major transcription factor in the GAAC pathway, or of SLC7A5, a leucine transporter, caused impaired mTOR reactivation and much higher levels of autophagy. Thus, the GAAC pathway modulates autophagy by regulating amino acid uptake and mTOR reactivation during serum/glutamine starvation. PMID:25049270

  14. The general amino acid control pathway regulates mTOR and autophagy during serum/glutamine starvation

    PubMed Central

    Chen, Rui; Zou, Yilong; Mao, Dongxue; Sun, Daxiao; Gao, Guanguang; Shi, Jingwen; Liu, Xiaoqing; Zhu, Chen; Yang, Mingyu; Ye, Wanlu; Hao, Qianqian

    2014-01-01

    Organisms have evolved elaborate mechanisms to adjust intracellular nutrient levels in response to fluctuating availability of exogenous nutrients. During starvation, cells can enhance amino acid uptake and synthesis through the general amino acid control (GAAC) pathway, whereas nonessential cellular contents are recycled by autophagy. How these two pathways are coordinated in response to starvation is currently unknown. Here we show that the GAAC pathway couples exogenous amino acid availability with autophagy. Starvation caused deactivation of mTOR, which then activated autophagy. In parallel, serum/glutamine starvation activated the GAAC pathway, which up-regulated amino acid transporters, leading to increased amino acid uptake. This elevated the intracellular amino acid level, which in turn reactivated mTOR and suppressed autophagy. Knockdown of activating transcription factor 4, the major transcription factor in the GAAC pathway, or of SLC7A5, a leucine transporter, caused impaired mTOR reactivation and much higher levels of autophagy. Thus, the GAAC pathway modulates autophagy by regulating amino acid uptake and mTOR reactivation during serum/glutamine starvation. PMID:25049270

  15. Promotion of silver catalysts for selective oxidation of methanol

    SciTech Connect

    Pestryakov, A.N.; Roznina, M.I.; Belousova, V.N.

    1994-04-10

    The catalytic and physicochemical properties of supported silver catalysts modified by oxides of rare and rare-earth metals have been studied. The effects of modifiers on electronic structure, degree of dispersion and surface diffusion of the supported metal, on Broensted`s acidity, and coking degree of the catalyst surface have been determined. The promotion effect of cerium and zirconium oxides on the catalyst have been found also.

  16. Formulation of cracking catalyst based on zeolite and natural clays

    Microsoft Academic Search

    R. R. Aliev; M. I. Lupina

    1995-01-01

    Domestically manufactured cracking catalysts are based on a synthetic amorphous aluminosilicate matrix and Y zeolite. A multistage {open_quotes}gel{close_quotes} technology is used in manufacturing the catalysts. The process includes mixing solutions of sodium silicate and acidic aluminum sulfate, forming, syneresis, and activation of the beaded gel. In the manufacture of bead catalysts, the next steps in the process are washing, drying,

  17. Process and catalyst for carbonylating olefins

    DOEpatents

    Zoeller, J.R.

    1998-06-02

    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.

  18. Rapeseed oil methyl esters preparation using heterogeneous catalysts

    Microsoft Academic Search

    S. Gryglewicz

    1999-01-01

    The classical method of fatty acids methyl esters (FAME) production is based on triglyceride transesterification to methyl esters. Sodium hydroxide dissolved in methanol is used as a catalyst. The purpose of this work was to examine a heterogeneous catalyst, in particular calcium compounds, to produce methyl esters of rapeseed oil. This research showed that the transesterification of rapeseed oil by

  19. Cerium-containing catalysts for converting ethanol into ethylene

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    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.

  20. Modification of silver catalysts for oxidation of methanol to formaldehyde

    Microsoft Academic Search

    A. N. Pestryakov

    1996-01-01

    Physico-chemical and catalytic properties of silver catalysts modified by Zr, Ce, La, Rb and Cs oxides have been studied in the process of the selective oxidation of methanol. Modifying additions in amounts of 1–10 wt.% change the effective charge and redox properties of supported silver, the metal dispersivity and its surface diffusion, surface acidity of the catalyst and degree of

  1. The Candida albicans GAP Gene Family Encodes Permeases Involved in General and Specific Amino Acid Uptake and Sensing?†

    PubMed Central

    Kraidlova, Lucie; Van Zeebroeck, Griet; Van Dijck, Patrick; Sychrová, Hana

    2011-01-01

    The Saccharomyces cerevisiae general amino acid permease Gap1 (ScGap1) not only mediates the uptake of most amino acids but also functions as a receptor for the activation of protein kinase A (PKA). Fungal pathogens can colonize different niches in the host, each containing various levels of different amino acids and sugars. The Candida albicans genome contains six genes homologous to the S. cerevisiae GAP1. The expression of these six genes in S. cerevisiae showed that the products of all six C. albicans genes differ in their transport capacities. C. albicans Gap2 (CaGap2) is the true orthologue of ScGap1 as it transports all tested amino acids. The other CaGap proteins have narrower substrate specificities though CaGap1 and CaGap6 transport several structurally unrelated amino acids. CaGap1, CaGap2, and CaGap6 also function as sensors. Upon detecting some amino acids, e.g., methionine, they are involved in a rapid activation of trehalase, a downstream target of PKA. Our data show that CaGAP genes can be functionally expressed in S. cerevisiae and that CaGap permeases communicate to the intracellular signal transduction pathway similarly to ScGap1. PMID:21764911

  2. Reducing fischer-tropsch catalyst attrition losses in high agitation reaction systems

    DOEpatents

    Singleton, Alan H. (Baden, PA); Oukaci, Rachid (Gibsonia, PA); Goodwin, James G. (Cranberry Township, PA)

    2001-01-01

    A method for reducing catalyst attrition losses in hydrocarbon synthesis processes conducted in high agitation reaction systems; a method of producing an attrition-resistant catalyst; a catalyst produced by such method; a method of producing an attrition-resistant catalyst support; and a catalyst support produced by such method. The inventive method of reducing catalyst attrition losses comprises the step of reacting a synthesis gas in a high agitation reaction system in the presence of a catalyst. In one aspect, the catalyst preferably comprises a .gamma.-alumina support including an amount of titanium effective for increasing the attrition resistance of the catalyst. In another aspect, the catalyst preferably comprises a .gamma.-alumina support which has been treated, after calcination, with an acidic, aqueous solution. The acidic aqueous solution preferably has a pH of not more than about 5. In another aspect, the catalyst preferably comprises cobalt on a .gamma.-alumina support wherein the cobalt has been applied to the .gamma.-alumina support by totally aqueous, incipient wetness-type impregnation. In another aspect, the catalyst preferably comprises cobalt on a .gamma.-alumina support with an amount of a lanthana promoter effective for increasing the attrition resistance of the catalyst. In another aspect, the catalyst preferably comprises a .gamma.-alumina support produced from boehmite having a crystallite size, in the 021 plane, in the range of from about 30 to about 55 .ANG.ngstrons. In another aspect, the inventive method of producing an attrition-resistant catalyst comprises the step of treating a .gamma.-alumina support, after calcination of and before adding catalytic material to the support, with an acidic solution effective for increasing the attrition resistance of the catalyst. In another aspect, the inventive method of producing an attrition-resistant catalyst support comprises the step of treating calcined .gamma.-alumina with an acidic, aqueous solution effective for increasing the attrition resistance of the .gamma.-alumina.

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

    Microsoft Academic Search

    Richard Lavery; Heinz Sklenar

    1988-01-01

    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

  4. Catalyst deoiling process

    Microsoft Academic Search

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

    1987-01-01

    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

  5. Functional Identification of the General Acid and Base in the Dehydration Step of Indole-3-glycerol Phosphate Synthase Catalysis*

    PubMed Central

    Zaccardi, Margot J.; Yezdimer, Eric M.; Boehr, David D.

    2013-01-01

    The tryptophan biosynthetic enzyme indole-3-glycerol phosphate synthase is a proposed target for new antimicrobials and is a favored starting framework in enzyme engineering studies. Forty years ago, Parry proposed that the enzyme mechanism proceeds through two intermediates in a series of condensation, decarboxylation, and dehydration steps. X-ray crystal structures have suggested that Lys-110 (numbering according to the Sulfolobus solfataricus enzyme) behaves as a general acid both in the condensation and dehydration steps, but did not reveal an efficient pathway for the reprotonation of this critical residue. Our mutagenesis and kinetic experiments suggest an alternative mechanism whereby Lys-110 acts as a general acid in the condensation step, but another invariant residue, Lys-53, acts as the general acid in the dehydration step. These studies also indicate that the conserved residue Glu-51 acts as the general base in the dehydration step. The revised mechanism effectively divides the active site into discrete regions where the catalytic surfaces containing Lys-110 and Lys-53/Glu-51 catalyze the ring closure (i.e. condensation and decarboxylation) and dehydration steps, respectively. These results can be leveraged toward the development of novel inhibitors against this validated antimicrobial target and toward the rational engineering of the enzyme to produce indole derivatives that are highly prized by the pharmaceutical and agricultural industries. PMID:23900843

  6. Accuracy assessment of the linear Poisson-Boltzmann equation and reparametrization of the OBC generalized Born model for nucleic acids and nucleic acid-protein complexes.

    PubMed

    Fogolari, Federico; Corazza, Alessandra; Esposito, Gennaro

    2015-04-01

    The generalized Born model in the Onufriev, Bashford, and Case (Onufriev et al., Proteins: Struct Funct Genet 2004, 55, 383) implementation has emerged as one of the best compromises between accuracy and speed of computation. For simulations of nucleic acids, however, a number of issues should be addressed: (1) the generalized Born model is based on a linear model and the linearization of the reference Poisson-Boltmann equation may be questioned for highly charged systems as nucleic acids; (2) although much attention has been given to potentials, solvation forces could be much less sensitive to linearization than the potentials; and (3) the accuracy of the Onufriev-Bashford-Case (OBC) model for nucleic acids depends on fine tuning of parameters. Here, we show that the linearization of the Poisson Boltzmann equation has mild effects on computed forces, and that with optimal choice of the OBC model parameters, solvation forces, essential for molecular dynamics simulations, agree well with those computed using the reference Poisson-Boltzmann model. PMID:25581160

  7. Fundamental studies of hydrogen chemisorption on supported monometallic and bimetallic catalysts using microcalorimetry

    Microsoft Academic Search

    1997-01-01

    Highly dispersed transition metal catalysts are used in numerous commercial processes such as hydrocarbon conversions. For example, the use of Pt supported on acidic alumina or silica-alumina for reforming of naphtha in the production of gasoline is well known. Another use of supported catalysts is in automobile emission control where supported Pt-Rh bimetallic catalysts are used. Supported Ru can be

  8. Mesoporous VMCM-41: highly efficient and remarkable catalyst for selective oxidation of cyclohexane to cyclohexanol

    Microsoft Academic Search

    S. E. Dapurkar; A. Sakthivel; P. Selvam

    2004-01-01

    Liquid phase oxidation of cyclohexane was carried out under milder reaction conditions over mesoporous VMCM-41 molecular sieve catalysts using aqueous hydrogen peroxide as oxidant, acetic acid as solvent, and methyl ethyl ketone as initiator. The catalysts showed high substrate conversion and excellent product (cyclohexanol) selectivity. Although the activity of the catalyst slightly decreased after first recycle, owing to leaching of

  9. Selective naphthene cracking over cascade dual catalyst in heavy aromatics transalkylation

    Microsoft Academic Search

    Tseng-Chang Tsai; Pei-Hsien Chao; Wei-Lun Zeng

    2007-01-01

    Deterioration of benzene product purity has been one of the major hurdles in the catalysis of metal supported zeolite catalyst in aromatics transalkylation processing. In the present study, a dual bed catalyst system is developed to tackle the key problem. By selective naphthene cracking, the use of one acidic zeolite as the bottom catalyst can significantly improve the benzene product

  10. Heterogenization of Homogeneous Catalysts: the Effect of the Support

    SciTech Connect

    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

    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.

  11. Catalyst by Design

    SciTech Connect

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

    2014-01-01

    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.

  12. Preparation of environmentally friendly alkylglucoside surfactants using zeolites as catalysts

    SciTech Connect

    Corma, A.; Iborra, S.; Miquel, S.; Primo, J. [Instituto de Tecnologia Quimica, Valencia (Spain)] [Instituto de Tecnologia Quimica, Valencia (Spain)

    1996-07-01

    Acid zeolites were evaluated for glycosidation activity of D-glucose and n-butanol. Zeolites with high Si/Al ratios such as faujasite and beta are the most suitable catalysts. 24 refs., 7 figs., 5 tabs.

  13. Regulation of the TCA cycle and the general amino acid permease by overflow metabolism in Rhizobium leguminosarum

    Microsoft Academic Search

    David L. Walshaw; Adam Wilkinson; Mathius Mundy; Mary Smith; Philip S. Poole

    1997-01-01

    Mutants of Rhizobium leguminosarum were selected that were altered in the uptake activity of the general amino acid permease (Aap). The main class of mutant maps to sud and suct), which are part of a gene cluster mdh-sucCDAB, which codes for malate dehydrogenase (mdh), succinyl-CoA synthetase (sucCD) and components of the 2-oxoglutarate dehydrogenase complex (sudB). Mutation of either SUCC or

  14. General Route for Preparing ?-Nitrocarbonyl Compounds Using Copper Thermal Redox Catalysis

    PubMed Central

    2015-01-01

    Using a simple copper catalyst, the alkylation of nitroalkanes with ?-bromocarbonyls is now possible. This method provides a general, functional group tolerant route to ?-nitrocarbonyl compounds, including nitro amides, esters, ketones, and aldehydes. The highly sterically dense, functional group rich products from these reactions can be readily elaborated into a range of complex nitrogen-containing molecules, including highly substituted ?-amino acids. PMID:24870052

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

    DOEpatents

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

    1998-01-01

    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.

  16. Fusidic acid cream in the treatment of impetigo in general practice: double blind randomised placebo controlled trial

    PubMed Central

    Koning, Sander; van Suijlekom-Smit, Lisette W A; Nouwen, Jan L; Verduin, Cees M; Bernsen, Roos M D; Oranje, Arnold P; Thomas, Siep; van der Wouden, Johannes C

    2002-01-01

    Objective To test the hypothesis that fusidic acid would not increase the treatment effect of disinfecting with povidone-iodine alone in children with impetigo. Design Randomised placebo controlled trial. Setting General practices in Greater Rotterdam. Participants 184 children aged 0-12 years with impetigo. Main outcome measures Clinical cure and bacterial cure after one week. Results After one week of treatment 55% of the patients in the fusidic acid group were clinically cured compared with 13% in the placebo group (odds ratio 12.6, 95% confidence interval 5.0 to 31.5, number needed to treat 2.3). After two weeks and four weeks the differences in cure rates between the two groups had become smaller. More children in the placebo group were non-compliant (12 v 5) and received extra antibiotic treatment (11 v 3), and more children in the placebo group reported adverse effects (19 v 7). Staphylococcus aureus was found in 96% of the positive cultures; no strains were resistant to fusidic acid. Conclusions Fusidic acid is much more effective than placebo (when both are given in combination with povidone-iodine shampoo) in the treatment of impetigo. Because of the low rate of cure and high rate of adverse events in the placebo group, the value of povidone-iodine in impetigo can be questioned. What is already known on this topicImpetigo is the most common skin infection in childrenFusidic acid, which is advocated as topical treatment in several countries, has never been investigated in a placebo controlled studyWhat this study addsIn combination with povidone-iodine, treatment with fusidic acid is much more effective than placeboNone of the strains of Staphylococcus aureus isolated at baseline showed resistance to fusidic acidThe value of treatment with povidone-iodine alone can be questioned PMID:11809642

  17. Trichloroisocyanuric acid (TCCA) as a mild and efficient catalyst for the trimethylsilylation of alcohols and phenols with hexamethyldisilazane (HMDS) under heterogonous conditions

    Microsoft Academic Search

    Ardeshir Khazaei; Mohammad Ali Zolfigol; Amin Rostami; Arash Ghorbani Choghamarani

    2007-01-01

    A novel and efficient method for the trimethylsilylation of various alcohols and phenols with hexamethyldisilazane (HMDS) catalyzed by trichloroisocyanuric acid (TCCA) in good to excellent yields in dichloromethane at room temperature was described.

  18. Method for regeneration and activity improvement of syngas conversion catalyst

    DOEpatents

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

    1980-01-01

    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.

  19. Photocatalytic degradation of azo dye acid red 14 in water on ZnO as an alternative catalyst to TiO 2

    Microsoft Academic Search

    N Daneshvar; D Salari; A. R Khataee

    2004-01-01

    The degradation of acid red 14 (AR14), commonly used as a textile dye, can be photocatalysed by ZnO. Using advanced oxidation processes (AOPs), zinc oxide appears to be a suitable alternative to TiO2 for water treatment. In this study, a detailed investigation of photocatalytic degradation of acid red 14 is presented. Photodegradation efficiency was small when the photolysis was carried

  20. Textured catalysts and methods of making textured catalysts

    DOEpatents

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

    2007-03-06

    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.

  1. Characteristics of polyaniline cobalt supported catalysts for epoxidation reactions.

    PubMed

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

    2014-01-01

    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

  2. Synthesis and investigation of tungsten-phosphorus catalysts

    SciTech Connect

    Obrubov, V.A.; Zhdanova, S.A.; Shchukin, V.P.

    1988-11-10

    The authors present the results of their investigation of the effect of phosphorus compounds on the activity of tungsten-containing catalysts in the oxidation of ethane. They investigated tungsten-phosphorus catalysts with different phosphorus concentrations (calculated on the basis of P/sub 2/O/sub 5/). The catalysts were prepared by heat decomposition of the starting compounds at 750/sup 0/C for 4 h. As their starting compounds, they used two types of materials: heteropoly acids mixtures of monosubstituted ammonium phosphoric and tungstic acids. The specific surface area of the catalysts was determined using the nitrogen desorption method. The x-ray phase analysis was carried out using a DRON-1.5 diffractometer. The catalytic activity was determined using the impulse method in a reactor with a vibrofluidized catalyst layer.

  3. Methods of making textured catalysts

    DOEpatents

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

    2010-08-17

    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.

  4. 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

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

    2010-11-01

    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.

  5. Generalized CNS disease and massive GM1-ganglioside accumulation in mice defective in lysosomal acid ?-galactosidase

    Microsoft Academic Search

    Christopher N. Hahn; Maria del Pilar Martin; Maria Schröder; Marie T. Vanier; Yoji Hara; Kinuko Suzuki; Kunihiko Suzuki; Alessandra d'Azzo

    Human GM1-gangliosidosis is caused by a genetic deficiency of lysosomal acid ?-galactosidase (?-gal). The disease manifests itself either as an infantile, juvenile or adult form and is primarily a neurological disorder with progressive brain dysfunction. A mouse model lacking a functional ?-gal gene has been generated by homologous recombination and embryonic stem cell technology. Tissues from affected mice are devoid

  6. Catalyst deoiling process

    SciTech Connect

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

    1987-04-28

    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.

  7. Measurement and modeling of acid dissociation constants of tri-peptides containing Glu, Gly, and His using potentiometry and generalized multiplicative analysis of variance.

    PubMed

    Khoury, Rima Raffoul; Sutton, Gordon J; Hibbert, D Brynn; Ebrahimi, Diako

    2013-02-28

    We report pK(a) values with measurement uncertainties for all labile protons of the 27 tri-peptides prepared from the amino acids glutamic acid (E), glycine (G) and histidine (H). Each tri-peptide (GGG, GGE, GGH, …, HHH) was subjected to alkali titration and pK(a) values were calculated from triplicate potentiometric titrations data using HyperQuad 2008 software. A generalized multiplicative analysis of variance (GEMANOVA) of pK(a) values for the most acidic proton gave the optimum model having two terms, an interaction between the end amino acids plus an isolated main effect of the central amino acid. PMID:23247603

  8. Attrition resistant cracking catalyst

    SciTech Connect

    Scherzer, J.

    1991-01-22

    This patent describes an attrition resistant catalytic cracking catalyst. It comprises: a molecular sieve dispersed in a matrix comprising a clay and a synthetic silica-alumina component. The catalyst made by the process comprises: combining the molecular sieve with the clay, a silica sol and aluminum chlorhydroxide to form a mixture consisting essentially of the molecular sieve, the clay, the silica sol and the aluminum chlorhydroxide; and drying the mixture to produce the attrition resistant catalyst.

  9. Kinetic resolution of racemic ?-hydroxyphosphonates by asymmetric esterification using achiral carboxylic acids with pivalic anhydride and a chiral acyl-transfer catalyst.

    PubMed

    Shiina, Isamu; Ono, Keisuke; Nakahara, Takayoshi

    2013-11-25

    A practical protocol is developed to directly provide chiral ?-acyloxyphosphonates and ?-hydroxyphosphonates from (±)-?-hydroxyphosphonates utilizing the transacylation process to generate the mixed anhydrides from acid components and pivalic anhydride in the presence of organocatalysts (s-value = 33-518). PMID:24100408

  10. 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...

  11. Liquefaction with microencapsulated catalysts

    DOEpatents

    Weller, Sol W. (Williamsville, NY)

    1985-01-01

    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.

  12. Polyolefin catalyst manufacturing

    SciTech Connect

    Inkrott, K.E.; Scinta, J.; Smith, P.D. (Catalyst Resources Inc., Pasadena, TX (US))

    1989-10-16

    Statistical process control (SPC) procedures are absolutely essential for making new-generation polyolefin catalysts with the consistent high quality required by modern polyolefin processes. Stringent quality assurance is critical to the production of today's high-performance catalysts. Research and development efforts during the last 20 years have led to major technological improvements in the polyolefin industry. New generation catalysts, which once were laboratory curiosities, must now be produced commercially on a regular and consistent basis to meet the increasing requirements of the plastics manufacturing industry. To illustrate the more stringent requirements for producing the new generation polyolefin catalysts, the authors compare the relatively simple, first-generation polypropylene catalyst production requirements with some of the basic requirements of manufacturing a more complex new-generation catalyst, such as Catalyst Resources Inc.'s LYNX 900. The principles which hold true for the new-generation catalysts such as LYNX 900 are shown to apply equally to the scale-up of other advanced technology polyolefin catalysts.

  13. Oxidation of Benzaldehyde to Benzoic Acid

    Microsoft Academic Search

    Hongyan Yan; Chunsheng Liu; Genxiang Luo

    2005-01-01

    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

  14. Designing catalysts for functionalization of unactivated C-H bonds based on the CH activation reaction.

    PubMed

    Hashiguchi, Brian G; Bischof, Steven M; Konnick, Michael M; Periana, Roy A

    2012-06-19

    In an effort to augment or displace petroleum as a source of liquid fuels and chemicals, researchers are seeking lower cost technologies that convert natural gas (largely methane) to products such as methanol. Current methane to methanol technologies based on highly optimized, indirect, high-temperature chemistry (>800 °C) are prohibitively expensive. A new generation of catalysts is needed to rapidly convert methane and O(2) (ideally as air) directly to methanol (or other liquid hydrocarbons) at lower temperatures (~250 °C) and with high selectivity. Our approach is based on the reaction between CH bonds of hydrocarbons (RH) and transition metal complexes, L(n)M-X, to generate activated L(n)M-R intermediates while avoiding the formation of free radicals or carbocations. We have focused on the incorporation of this reaction into catalytic cycles by integrating the activation of the CH bond with the functionalization of L(n)M-R to generate the desired product and regenerate the L(n)M-X complex. To avoid free-radical reactions possible with the direct use of O(2), our approach is based on the use of air-recyclable oxidants. In addition, the solvent serves several roles including protection of the product, generation of highly active catalysts, and in some cases, as the air-regenerable oxidant. We postulate that there could be three distinct classes of catalyst/oxidant/solvent systems. The established electrophilic class combines electron-poor catalysts in acidic solvents that conceptually react by net removal of electrons from the bonding orbitals of the CH bond. The solvent protects the CH(3)OH by conversion to more electron-poor [CH(3)OH(2)](+) or the ester and also increases the electrophilicity of the catalyst by ligand protonation. The nucleophilic class matches electron-rich catalysts with basic solvents and conceptually reacts by net donation of electrons to the antibonding orbitals of the CH bond. In this case, the solvent could protect the CH(3)OH by deprotonation to the more electron-rich [CH(3)O](-) and increases the nucleophilicity of the catalysts by ligand deprotonation. The third grouping involves ambiphilic catalysts that can conceptually react with both the HOMO and LUMO of the CH bond and would typically involve neutral reaction solvents. We call this continuum base- or acid-modulated (BAM) catalysis. In this Account, we describe our efforts to design catalysts following these general principles. We have had the most success with designing electrophilic systems, but unfortunately, the essential role of the acidic solvent also led to catalyst inhibition by CH(3)OH above ~1 M. The ambiphilic catalysts reduced this product inhibition but were too slow and inefficient. To date, we have designed new base-assisted CH activation and L(n)M-R fuctionalization reactions and are working to integrate these into a complete, working catalytic cycle. Although we have yet to design a system that could supplant commercial processes, continued exploration of the BAM catalysis continuum may lead to new systems that will succeed in addressing this valuable goal. PMID:22482496

  15. Method for producing iron-based catalysts

    DOEpatents

    Farcasiu, Malvina (Pittsburgh, PA); Kaufman, Phillip B. (Library, PA); Diehl, J. Rodney (Pittsburgh, PA); Kathrein, Hendrik (McMurray, PA)

    1999-01-01

    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.

  16. Reclamation of nickel from spent nickel catalyst

    Microsoft Academic Search

    Arun Shukla; P. N. Maheshwari; A. K. Vasishtha

    1988-01-01

    Spent nickel catalyst containing an average 9.6% nickel was obtained locally from an oil hydrogenation industry. It was digested\\u000a with 1–3N HCl, HNO3, H2SO4 and mixtures thereof in one to three stages of durations ranging from one to three hr at 100C using spent nickel catalyst\\u000a to acid proportions of 1:3 to 1:8 (w\\/v). Nickel recoveries of over 94% were

  17. Selective oxidation of veratryl alcohol with composites of Au nanoparticles and graphene quantum dots as catalysts.

    PubMed

    Wu, Xiaochen; Guo, Shouwu; Zhang, Jingyan

    2015-04-14

    Veratryl alcohol can be oxidized to veratryl aldehyde or veratric acid with excellent selectivity and efficient conversion under acidic and alkaline conditions using Au nanoparticles and graphene quantum dot composites (Au/GQDs) as catalysts. PMID:25760658

  18. Esterification Reaction Utilizing Sense of Smell and Eyesight for Conversion and Catalyst Recovery Monitoring

    ERIC Educational Resources Information Center

    Janssens, Nikki; Wee, Lik H.; Martens, Johan A.

    2014-01-01

    The esterification reaction of salicylic acid with ethanol is performed in presence of dissolved 12-tungstophosphoric Brønsted-Lowry acid catalyst, a Keggin-type polyoxometalate (POM). The monitoring of the reaction with smell and the recovery of the catalyst with sight is presented. Formation of the sweet-scented ester is apparent from the smell.…

  19. Metal chelate catalysts for fuel cells. Final report June 1979 - October 1982

    Microsoft Academic Search

    R. Darby; M. Yamana; H. Dhar; R. White

    1982-01-01

    Various modified forms of several organometallic chelate compounds were synthesized and tested for their activity and stability as oxygen reduction electrocatalysts in sulfuric acid electrolyte. The most active catalysts found were cobalt tetraazaannulene (CoTAA), iron phthalocyanine (FePc) and cobalt tetraphenylporphyrin (CoTPP). However, these catalysts have limited stability in strong acids.

  20. Metal chelate catalysts for fuel cells. Final report June 1979 - October 1982

    SciTech Connect

    Darby, R.; Yamana, M.; Dhar, H.; White, R.

    1982-10-01

    Various modified forms of several organometallic chelate compounds were synthesized and tested for their activity and stability as oxygen reduction electrocatalysts in sulfuric acid electrolyte. The most active catalysts found were cobalt tetraazaannulene (CoTAA), iron phthalocyanine (FePc) and cobalt tetraphenylporphyrin (CoTPP). However, these catalysts have limited stability in strong acids.

  1. Thermodynamic and kinetic aspects of surface acidity

    Microsoft Academic Search

    Dumesic

    1991-01-01

    A continuing goal of our research for the Department of Energy has been to develop methods to characterize catalyst acidity and to understand the chemical and structural properties that control the number, type and strength of catalytic acid sites. During the past year we have employed microcalorimetry, thermogravimetry and nuclear magnetic resonance to study the acidity of various zeolite catalysts.

  2. Cerium impregnated H-mordenite as a catalyst for shape-selective isopropylation of naphthalene. Selective deactivation of acid sites on the external surface

    Microsoft Academic Search

    J.-H. Kim; Y. Sugi; T. Matsuzaki; T. Hanaoka; Y. Kubota; X. Tu; M. Matsumoto; S. Nakata; A. Kato; G. Seo; C. Pak

    1995-01-01

    The impregnation of cerium is the effective method for the deactivation of external acid sites of H-mordenite. The selectivity of 2,6-DIPN in the isopropylation of naphthalene was enhanced by the impregnation with such a large amount as 30–50 wt.-% of cerium without significant decrease of catalytic activity. The highest selectivity of 2,6-DIPN was achieved up to 70% over a highly

  3. 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

    Azizi, Seyed Naser; Shakeri, Parmis; Chaichi, Mohammad Javad; Bekhradnia, Ahmadreza; Taghavi, Mehdi; Ghaemy, Mousa

    2014-03-25

    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

  4. 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)

    Azizi, Seyed Naser; Shakeri, Parmis; Chaichi, Mohammad Javad; Bekhradnia, Ahmadreza; Taghavi, Mehdi; Ghaemy, Mousa

    2014-03-01

    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.

  5. 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

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

    2013-05-15

    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

  6. Pd and PdCo alloy nanoparticles supported on polypropylenimine dendrimer-grafted graphene: A highly efficient anodic catalyst for direct formic acid fuel cells

    NASA Astrophysics Data System (ADS)

    Hosseini, Hadi; Mahyari, Mojtaba; Bagheri, Akbar; Shaabani, Ahmad

    2014-02-01

    For the first time, Pd and PdCo alloy nanoparticles supported on polypropylenimine dendrimer-grafted graphene (Pd and PdCo/PPI-g-G) are prepared and characterized with Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The electrocatalytic activity of Pd and PdCo/PPI-g-G are investigated in terms of formic acid electrooxidation in H2SO4 aqueous solution. The PdCo/PPI-g-G shows much higher formic acid oxidation activities in comparison with Pd/PPI-g-G, and it is more resistant to the surface poisoning. This improved electrocatalytic performance may be due to the fine dispersion of PdCo alloy nanoparticles and bi-functional effect. The kinetic parameters such as charge transfer coefficient and the diffusion coefficient of formic acid are estimated under the quasi steady-state conditions.

  7. 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)

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

    2013-05-01

    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.

  8. Nickel recovery from spent nickel catalyst.

    PubMed

    Sahu, Kamala K; Agarwal, Archana; Pandey, Banshi D

    2005-04-01

    A process for nickel recovery from a spent catalyst of definite composition has been developed using the hydro-metallurgical route. The processing steps includes direct sulphuric acid leaching followed by separation of iron as well as silica and other impurities. For a 152 microm particle size catalyst, extraction of about 98% nickel was achieved at 363 K in 2 h using a sulphuric acid concentration (v/v) of 8% and a pulp density of 10%. The dissolution of nickel followed diffusion-controlled leaching kinetics. Increase in temperature and sulphuric acid concentration resulted in increase in the nickel recovery. The activation energy for nickel dissolution was calculated to be 62.8 kJ mol(-1). Finally, nickel was recovered as value-added products such as sulphide and oxalate with overall recovery of 90 and 88% of nickel, respectively. PMID:15864956

  9. Catalyst attrition in cyclones

    Microsoft Academic Search

    J Reppenhagen; J Werther

    2000-01-01

    The mechanism of catalyst attrition in cyclones has been investigated both theoretically and experimentally for various types of catalysts. A model is suggested that considers cyclone attrition under steady-state conditions as a comminution process. It considers the efficiency of such a process by relating the surface energy created by comminution to the kinetic energy, which has been spent to create

  10. Attrition resistant cracking catalyst

    Microsoft Academic Search

    Scherzer

    1991-01-01

    This patent describes an attrition resistant catalytic cracking catalyst. It comprises: a molecular sieve dispersed in a matrix comprising a clay and a synthetic silica-alumina component. The catalyst made by the process comprises: combining the molecular sieve with the clay, a silica sol and aluminum chlorhydroxide to form a mixture consisting essentially of the molecular sieve, the clay, the silica

  11. Hydrocarbon conversion catalyst preparation

    Microsoft Academic Search

    E. W. Albers; J. S. Dumoulin; M. A. Seese

    1981-01-01

    A dense, highly attrition resistant catalyst is prepared by reacting an alkali-metal silicate and aluminate under conditions which produce a thermally and hydrothermally stable cogel having a substantial surface area in pores ranging from about 25 to 75A*. The catalyst includes excess silicate obtained as a product from a type Y zeolite synthesis.

  12. Nanostructured catalyst supports

    DOEpatents

    Zhu, Yimin; Goldman, Jay L.; Qian, Baixin; Stefan, Ionel C.

    2012-10-02

    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.

  13. Designing oxidation catalysts

    Microsoft Academic Search

    Graham J. Hutchings; Stuart H. Taylor

    1999-01-01

    A simplified approach is described for the design of oxidation catalysts. It is based on three components and for selective oxidation the approach involves identifying catalysts that (a) do not catalyse the oxidation of the required product under the reaction conditions to be tested, (b) activate the oxidant and (c) activate the substrate. This approach is initially demonstrated to identify

  14. Fischer-Tropsch Catalysts

    NASA Technical Reports Server (NTRS)

    White, James H. (Inventor); Taylor, Jesse W. (Inventor)

    2008-01-01

    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.

  15. Magnetic and Dendritic Catalysts.

    PubMed

    Wang, Dong; Deraedt, Christophe; Ruiz, Jaime; Astruc, Didier

    2015-07-21

    The recovery and reuse of catalysts is a major challenge in the development of sustainable chemical processes. Two methods at the frontier between homogeneous and heterogeneous catalysis have recently emerged for addressing this problem: loading the catalyst onto a dendrimer or onto a magnetic nanoparticle. In this Account, we describe representative examples of these two methods, primarily from our research group, and compare them. We then describe new chemistry that combines the benefits of these two methods of catalysis. Classic dendritic catalysis has involved either attaching the catalyst covalently at the branch termini or within the dendrimer core. We have used chelating pyridyltriazole ligands to insolubilize catalysts at the termini of dendrimers, providing an efficient, recyclable heterogeneous catalysts. With the addition of dendritic unimolecular micelles olefin metathesis reactions catalyzed by commercial Grubbs-type ruthenium-benzylidene complexes in water required unusually low amounts of catalyst. When such dendritic micelles include intradendritic ligands, both the micellar effect and ligand acceleration promote faster catalysis in water. With these types of catalysts, we could carry out azide alkyne cycloaddition ("click") chemistry with only ppm amounts of CuSO4·5H2O and sodium ascorbate under ambient conditions. Alternatively we can attach catalysts to the surface of superparamagnetic iron oxide nanoparticles (SPIONs), essentially magnetite (Fe3O4) or maghemite (?-Fe2O3), offering the opportunity to recover the catalysts using magnets. Taking advantage of the merits of both of these strategies, we and others have developed a new generation of recyclable catalysts: dendritic magnetically recoverable catalysts. In particular, some of our catalysts with a ?-Fe2O3@SiO2 core and 1,2,3-triazole tethers and loaded with Pd nanoparticles generate strong positive dendritic effects with respect to ligand loading, catalyst loading, catalytic activity and recyclability. In other words, the dendritic catalysts were more efficient and more stable than their nondendritic ?-Fe2O3@SiO2 analogues. The bulk at the dendritic periphery helps to localize the metal nanoparticles at the SPION core surface, which confers these advantages. We could also use sonification as a remarkably simple and efficient method to impregnate the SPIONs with dendrimer-encapsulated PdNPs. Catalysis within the hydrophobic dendrimer pockets that include ligands leads to rapid turnover with or without a ?-Fe2O3@SiO2 core. In addition, catalytically active metal nanoparticles are more robust when they are loaded onto the surface of a ?-Fe2O3@SiO2 dendritic core. Herein, we illustrate this chemistry with examples including olefin metathesis, click chemistry, cross carbon-carbon bond forming reactions, and selective alcohol oxidation. PMID:26098668

  16. A general reaction-diffusion model of acidity in cancer invasion.

    PubMed

    McGillen, Jessica B; Gaffney, Eamonn A; Martin, Natasha K; Maini, Philip K

    2014-04-01

    We model the metabolism and behaviour of a developing cancer tumour in the context of its microenvironment, with the aim of elucidating the consequences of altered energy metabolism. Of particular interest is the Warburg Effect, a widespread preference in tumours for cytosolic glycolysis rather than oxidative phosphorylation for glucose breakdown, as yet incompletely understood. We examine a candidate explanation for the prevalence of the Warburg Effect in tumours, the acid-mediated invasion hypothesis, by generalising a canonical non-linear reaction-diffusion model of acid-mediated tumour invasion to consider additional biological features of potential importance. We apply both numerical methods and a non-standard asymptotic analysis in a travelling wave framework to obtain an explicit understanding of the range of tumour behaviours produced by the model and how fundamental parameters govern the speed and shape of invading tumour waves. Comparison with conclusions drawn under the original system--a special case of our generalised system--allows us to comment on the structural stability and predictive power of the modelling framework. PMID:23536240

  17. Study of liquid-phase dehydration of d,l -1-(4-aminophenyl)ethanol in the presence of acid catalysts

    Microsoft Academic Search

    A. L. Schul’tsev; E. F. Panarin

    2010-01-01

    Thermal acid-catalyzed liquid-phase dehydration of 1-(4-aminophenyl)ethanol at 250–260°C and 30–100 mm Hg was studied. In\\u000a the presence of KHSO4 a 2:1 mixture of 1-amino-4-ethylbenzene with 4-aminostyrene is formed, the use of KHSO4\\/KH2PO4 causes the formation of polymers, and the use of H3BO3 (? 0.26 wt %) in a mixture with KHSO4 allows the preparation of pure 4-aminostyrene. The structure of

  18. Competing reaction processes on a lattice as a paradigm for catalyst deactivation.

    PubMed

    Abad, E; Kozak, J J

    2015-02-01

    We mobilize both a generating function approach and the theory of finite Markov processes to compute the probability of irreversible absorption of a randomly diffusing species on a lattice with competing reaction centers. We consider an N-site lattice populated by a single deep trap, and N-1 partially absorbing traps (absorption probability 0catalyst deactivation processes on planar surfaces and on catalyst pellets where only a single catalytic site remains fully active (deep trap), the other sites being only partially active as a result of surface poisoning. The central result of our study is that the predicted dependence of the reaction efficiency on system size N and on s is in qualitative accord with previously reported experimental results, notably catalysts exhibiting selective poisoning due to surface sites that have different affinities for chemisorption of the poisoning agent (e.g., acid zeolite catalysts). Deviations from the efficiency of a catalyst with identical sites are quantified, and we find that such deviations display a significant dependence on the topological details of the surface (for fixed values of N and s we find markedly different results for, say, a planar surface and for the polyhedral surface of a catalyst pellet). Our results highlight the importance of surface topology for the efficiency of catalytic conversion processes on inhomogeneous substrates, and in particular for those aimed at industrial applications. From our exact analysis we extract results for the two limiting cases s?1 and s?0, corresponding respectively to weak and strong catalyst poisoning (decreasing s leads to a monotonic decrease in the efficiency of catalytic conversion). The results for the s?0 case are relevant for the dual problem of light-energy conversion via trapping of excitations in the chlorophyll antenna network. Here, decreasing the probability of excitation trapping s at sites other than the target molecule does not result in a decrease of the efficiency as in the catalyst case, but rather in enhanced efficiency of light-energy conversion, which we characterize in terms of N and s. The one-dimensional case and its connection with a modified version of the gambler's ruin problem are discussed. Finally, generalizations of our model are described briefly. PMID:25768457

  19. Gasification characteristics of an activated carbon catalyst during the decomposition of hazardous waste material in supercritical water

    Microsoft Academic Search

    Yukihiko Matsumura; F. W. Nuessle; M. J. Jr. Antal

    1996-01-01

    Recently, carbonaceous materials including activated carbon were proven to be effective catalysts for hazardous waste gasification in supercritical water. Using coconut shell activated carbon catalyst, complete decomposition of industrial organic wastes including methanol and acetic acid was achieved. During this process, the total mass of the activated carbon catalyst changes by two competing processes: a decrease in weight via gasification

  20. The selection reaction of homogeneous catalyst in soy-epoxide hydroxylation

    NASA Astrophysics Data System (ADS)

    Elvistia Firdaus, Flora

    2014-04-01

    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.

  1. Using computational methods to explore improvements to Knölker's iron catalyst.

    PubMed

    Lu, Xi; Zhang, Yawei; Turner, Nicholas; Zhang, Mingtao; Li, Tonglei

    2014-07-01

    Knölker's iron catalyst is characterized by low toxicity and relatively low price in comparison with precious metal catalysts. Density functional theory was used to explore improvements to this catalyst. It was found that electron-withdrawing substituents on the CpOH ring are favorable for improving the efficiency of iron catalysts. Increasing the acidity of CpOH is also an available means of improving the catalytic efficiency. However, replacing the hydroxyl of CpOH with the amino group is not a valid choice for improvement. In contrast, substituting phosphine ligands for carbonyls is the most effective method for improving the catalytic activity of the iron catalyst. But the PR3 ligand must have electron-donating groups and its steric effect should be controlled in a suitable range. Replacing carbonyl groups by PH3 and PPhH2 ligands can effectually improve the catalytic activity for hydrogenation of ketones. PMID:24840123

  2. Highly attrition resistant mesoporous catalytic cracking catalysts

    SciTech Connect

    Wachter, W.A.

    1993-06-22

    A catalytic cracking catalyst is described for converting a hydrocarbon feedstock at elevated temperature in the substantial absence of hydrogen, into lower average molecular weight, lower boiling hydrocarbon transportation fuel which comprises a crystalline aluminosilicate zeolite having a silica:alumina mole ratio greater than 2:1, and uniform pore diameters ranging from about 4 Angstroms to about 15 Angstroms in diameter, in concentration ranging from about 30% to about 60%, based on the total weight of the catalyst, a matrix comprised of silica and clay within which the crystalline aluminosilicate zeolite is dispersed, said matrix being characterized as porous and the pores as having a bimodal pore size distribution, as measured by mercury porosimetry, a first mode wherein from about 80% to about 90% of the pore volume measured between 45 Angstroms and 2,000 Angstroms is in pores ranging from about 160 Angstroms in diameter to about 400 Angstroms in diameter, and a second mode wherein from about 5% to about 10% of the pores are of diameter ranging above about 100 Angstroms to about 160 Angstroms, and the attrition-resistance of the catalyst, as measured by the Davison Index ranges from about 1 to about 8, wherein the silica matrix portion of said catalyst is prepared from a silica sol made via an ion-exchanged process, and an acidic silica sol prepared by the reaction of sodium silicate, an acid and an aluminum salt, and an aluminum salt of a mineral acid, and wherein the sol is not converted to a gel during catalyst preparation.

  3. Increasing FCC regenerator catalyst level

    SciTech Connect

    Wong, R.F. (Petroleos del Peru, Lima (Peru))

    1993-11-01

    A Peruvian FCC unit's operations were improved by increasing the regenerator's catalyst level. This increase resulted in lower stack losses, an improved temperature profile, increased catalyst activity and a lower catalyst consumption rate. A more stable operation saved this Peruvian refiner over $131,000 per year in catalyst alone. These concepts and data may be suitable for your FCC unit as well.

  4. Catalyst Activity Comparison of Alcohols over Zeolites

    SciTech Connect

    Ramasamy, Karthikeyan K.; Wang, Yong

    2013-01-01

    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.

  5. Comparison of Pt\\/zeolite catalysts for n-hexadecane hydroisomerization

    Microsoft Academic Search

    Kwang-Cheon Park; Son-Ki Ihm

    2000-01-01

    Bifunctional platinum (0.5wt.%) catalysts containing ZSM-5, ZSM-22, SAPO-11, Al-MCM-41, H-Y and H-? were tested for the hydroisomerization of n-hexadecane and their catalytic activities were compared. The Pt\\/ZSM-5, Pt\\/ZSM-22 and Pt\\/H-? catalysts showed higher hydrocracking activity due to their strong acid sites, while the Pt\\/SAPO-11, Pt\\/Al-MCM-41 and Pt\\/H-Y catalysts with moderate acid strength showed better isomerization selectivity. Especially the Pt\\/Al-MCM-41 catalyst,

  6. Fundamental studies of supported bimetallic catalysts by NMR spectroscopy

    SciTech Connect

    Savargaonkar, N.

    1996-10-17

    Various hydrogenation reactions on transition metals are important commercially whereas certain hydrogenolysis reactions are useful from fundamental point of view. Understanding the hydrogen mobility and kinetics of adsorption-desorption of hydrogen is important in understanding the mechanisms of such reactions involving hydrogen. The kinetics of hydrogen chemisorption was studied by means of selective excitation NMR on silica supported Pt, Rh and Pt-Rh catalysts. The activation energy of hydrogen desorption was found to be lower on silica supported Pt catalysts as compared to Rh and Pt-Rh catalysts. It was found that the rates of hydrogen adsorption and desorption on Pt-Rh catalyst were similar to those on Rh catalyst and much higher as compared to Pt catalyst. The Ru-Ag bimetallic system is much simpler to study than the Pt-Rh system and serves as a model system to characterize more complicated systems such as the K/Ru system. Ag was found to decrease the amounts of adsorbed hydrogen and the hydrogen-to-ruthenium stoichiometry. Ag reduced the populations of states with low and intermediate binding energies of hydrogen on silica supported Ru catalyst. The rates of hydrogen adsorption and desorption were also lower on silica supported Ru-Ag catalyst as compared to Ru catalyst. This report contains introductory information, the literature review, general conclusions, and four appendices. An additional four chapters and one appendix have been processed separately for inclusion on the data base.

  7. Hydroisomerization of n-hexadecane on zeolite catalysts

    Microsoft Academic Search

    W. Huang; D. Li; X. Kang; Y. Shi; H. Nie

    2004-01-01

    Bifunctional platinum catalysts containing MCM-22, ZSM-5, SAPO-11 and H-Beta were tested for their hydroisomerization of n-hexadecane(n-C16), and their catalytic activities and selectivity were compared. Pt\\/MCM-22 and Pt\\/ZSM-5 catalysts showed lower isomerization selectivity due to their strong acidity, while Pt\\/SAPO-11 and Pt\\/H-Beta catalysts showed higher selectivity. Through the analysis of the product distribution, the hydroisomerization mechanism on Pt\\/SAPO-11 was discussed. It

  8. Catalyst for microelectromechanical systems microreactors

    DOEpatents

    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)

    2010-06-29

    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.

  9. Selective hydrogenation of soybean oil. II. Copper-chromium catalysts

    Microsoft Academic Search

    S. Koritala; H. J. Dutton

    1966-01-01

    Soybean oil was partially hydrogenated at 170 and 200C with 0.5 and 0.1% copper-chromium catalysts, respectively. The reaction\\u000a proceeded selectively at both temperatures, although selectivity was better at the lower temperature. Both commercial and\\u000a laboratory-prepared catalysts reduced the linolenic acid to less than 1% and with selectivity ratios (KLe\\/KLo) ranging from 6 to 13. Since stearate did not increase, linoleate

  10. 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.

  11. Catalyst system comprising a first catalyst system tethered to a supported catalyst

    DOEpatents

    Angelici, R.J.; Gao, H.

    1998-08-04

    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.

  12. Bimetallic Cobalt Based Catalysts

    Microsoft Academic Search

    László Guczi; Goran Boskovic; Ern? Kiss

    2010-01-01

    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,

  13. Crystalline titanate catalyst supports

    SciTech Connect

    Anthony, R.G.; Dosch, R.G.

    1991-12-31

    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.

  14. Crystalline titanate catalyst supports

    DOEpatents

    Anthony, Rayford G. (Bryan, TX); Dosch, Robert G. (Albuquerque, NM)

    1993-01-01

    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.

  15. Crystalline titanate catalyst supports

    DOEpatents

    Anthony, R.G.; Dosch, R.G.

    1993-01-05

    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.

  16. Mechanisms of catalyst deactivation

    Microsoft Academic Search

    Calvin H Bartholomew

    2001-01-01

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

  17. Reforming using erionite catalysts

    Microsoft Academic Search

    J. Liers; J. Meusinger; A. Moesch; W. Reschetilowski

    1993-01-01

    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

  18. 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. 

  19. Modified 8-ring zeolites as catalysts

    SciTech Connect

    Bergna, H.E.; Corbin, D.R.; Sonnichsen, G.C.

    1988-06-21

    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.

  20. Advances in autoexhaust catalysts

    SciTech Connect

    Funabiki, M.; Yamada, T.; Kayano, K. [N.E. Chemcat Corp., Numazu (Japan)

    1997-12-31

    Exhaust emission standards were set by the Clean Air Act Amendments of 1970 requiring automobile manufacturers to control the amount of hydrocarbons (HC), carbon monoxide (CO) and oxides of nitrogen (NO{sub x}) emitted from vehicles. These emissions from vehicles have been significantly reduced in the 20 years since auto exhaust catalysts was first used. Non-methane hydrocarbons and NO{sub x} emissions from vehicles, which are the root causes of photochemical smog, come under more stringent control year by year. Hydrocarbon emissions are required to be reduced to less than one-fifth of their present levels by the year 2000. To meet this stringent hydrocarbon emission standards, one of the cold start strategies is to use a quick light-off catalyst which is mounted at a close-coupled manifold position. In this application, it is inevitable that current TWC catalysts manifold position is thermally deactivated, because the catalyst is exposed to high temperatures, 100-150{degrees}C higher than the catalyst would encounter at the underfloor position. Our future catalyst development has focused on minimizing thermal deactivation via stabilization of ceria (CeO{sub 2}), which is used as an oxygen storage component (OSC) in TWC catalysis.

  1. Jumping-catalyst dynamics in nanowire growth.

    PubMed

    Schwarz, K W; Tersoff, J; Kodambaka, S; Ross, F M

    2014-08-01

    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. PMID:25126926

  2. Characterization of three-way automotive catalysts

    SciTech Connect

    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

    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.

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

    SciTech Connect

    Davis, Mark E.

    2009-03-13

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

  4. CLA production from ricinoleic acid by lactic acid bacteria

    Microsoft Academic Search

    Akinori Ando; Jun Ogawa; Shigenobu Kishino; Sakayu Shimizu

    2003-01-01

    The ability to produce CLA from ricinoleic acid is widely distributed in lactic acid bacteria. Washed cells of Lactobacillus plantarum JCM 1551 were selected as a potential catalyst for CLA production from ricinoleic acid. Cells cultivated in medium supplemented\\u000a with a mixture of ?-linolenic acid and linoleic acid showed enhanced CLA productivity. Under optimal reaction conditions,\\u000a with the free acid

  5. Methane oxidation over dual redox catalysts

    SciTech Connect

    Klier, K.; Herman, R.G.; Sojka, Z.; DiCosimo, J.I.; DeTavernier, S.

    1992-06-01

    Catalytic oxidation of methane to partial oxidation products, primarily formaldehyde and C[sub 2] hydrocarbons, was found to be directed by the catalyst used. In this project, it was discovered that a moderate oxidative coupling catalyst for C[sub 2] hydrocarbons, zinc oxide, is modified by addition of small amounts of Cu and Fe dopants to yield fair yields of formaldehyde. A similar effect was observed with Cu/Sn/ZnO catalysts, and the presence of a redox Lewis acid, Fe[sup III] or Sn[sup IV], was found to be essential for the selectivity switch from C[sub 2] coupling products to formaldehyde. The principle of double doping with an oxygen activator (Cu) and the redox Lewis acid (Fe, Sn) was pursued further by synthesizing and testing the CuFe-ZSM-5 zeolite catalyst. The Cu[sup II](ion exchanged) Fe[sup III](framework)-ZSM-5 also displayed activity for formaldehyde synthesis, with space time yields exceeding 100 g/h-kg catalyst. However, the selectivity was low and earlier claims in the literature of selective oxidation of methane to methanol over CuFe-ZSM-5 were not reproduced. A new active and selective catalytic system (M=Sb,Bi,Sn)/SrO/La[sub 2]O[sub 3] has been discovered for potentially commercially attractive process for the conversion of methane to C[sub 2] hydrocarbons, (ii) a new principle has been demonstrated for selectivity switching from C[sub 2] hydrocarbon products to formaldehyde in methane oxidations over Cu,Fe-doped zinc oxide and ZSM-5, and (iii) a new approach has been initiated for using ultrafine metal dispersions for low temperature activation of methane for selective conversions. Item (iii) continues being supported by AMOCO while further developments related to items (i) and (ii) are the objective of our continued effort under the METC-AMOCO proposed joint program.

  6. New catalysts for coal liquefaction and new nanocrystalline catalysts synthesis methods

    SciTech Connect

    Linehan, J.C.; Matson, D.W.; Darab, J.G.

    1994-09-01

    The use of coal as a source of transportation fuel is currently economically unfavorable due to an abundant world petroleum supply and the relatively high cost of coal liquefaction. Consequently, a reduction in the cost of coal liquefaction, for example by using less and/or less costly catalysts or lower liquefaction temperatures, must be accomplished if coal is to play an significant role as a source of liquid feedstock for the petrochemical industry. The authors and others have investigated the applicability of using inexpensive iron-based catalysts in place of more costly and environmentally hazardous metal catalysts for direct coal liquefaction. Iron-based catalysts can be effective in liquefying coal and in promoting carbon-carbon bond cleavage in model compounds. The authors have been involved in an ongoing effort to develop and optimize iron-based powders for use in coal liquefaction and related petrochemical applications. Research efforts in this area have been directed at three general areas. The authors have explored ways to optimize the effectiveness of catalyst precursor species through use of nanocrystalline materials and/or finely divided powders. In this effort, the authors have developed two new nanophase material production techniques, Modified Reverse Micelle (MRM) and the Rapid Thermal Decomposition of precursors in Solution (RTDS). A second effort has been aimed at optimizing the effectiveness of catalysts by variations in other factors. To this, the authors have investigated the effect that the crystalline phase has on the capacity of iron-based oxide and oxyhydroxide powders to be effectively converted to an active catalyst phase under liquefaction conditions. And finally, the authors have developed methods to produce active catalyst precursor powders in quantities sufficient for pilot-scale testing. Major results in these three areas are summarized.

  7. Hydroconversion of n-dodecane over nanoporous catalysts.

    PubMed

    Park, Young-Kwon; Lee, Hyung Won; Jeon, Jong-Ki; Han, Jeongsik; Kim, Chul-Ung; Jeong, Soon-Yong; Jeong, Kwang-Eun

    2013-01-01

    Platinum catalysts impregnated on different nanoporous materials, Meso-MFI, Si-SBA-15 and AI-SBA-15, were synthesized, and the hydroconversion of n-dodecane over these catalysts was performed. The catalytic characteristics were analyzed by Brunauer-Emmett-Teller surface area, X-ray diffraction, N2-adsorption-desorption and temperature programmed desorption of NH3. The effects of operation parameters, such as temperature and pressure, on the catalytic activities were investigated. The catalytic activities were affected considerably by the acidic properties of the catalysts, temperature and pressure. Higher acidity, high temperature and low hydrogen pressure resulted in higher hydroconversion and facilitated hydrocracking. The weak acidity, low temperature and high hydrogen pressure resulted in lower hydroconversion and higher selectivity to i-dodecane. PMID:23646804

  8. Hydrotalcite-type catalysts for narrow-range oxyethylation of 1-dodecanol using ethyleneoxide

    Microsoft Academic Search

    Daehwan Kim; Chengzhe Huang; Hongsun Lee; Insun Han; Sungkwon Kang; Soohan Kwon; Jeongho Lee; Yohan Han; Hyungrok Kim

    2003-01-01

    Hydrotalcite-type catalysts were studied for the oxyethylation of 1-dodecanol. Hydrotalcite-type catalysts treated with dodecanoic acid are very active for the narrow-range oxyethylation of 1-dodecanol.The narrow distribution of oxyethylene units in the dodecylethoxylates is elucidated by the constrained reaction on the surface of hydrotalcite-type catalysts. In the proposed surface reaction scheme, the following points are presented. (1) The relatively basic reactants,

  9. Strontium carbonate supported cobalt catalyst for dry reforming of methane under pressure

    Microsoft Academic Search

    K. Omata; N. Nukui; T. Hottai; Y. Showa; M. Yamada

    2004-01-01

    Catalytic performance of Co–SrO catalyst for dry reforming of methane was investigated at 1 MPa, 1023 K. The catalyst prepared by oxalate co-precipitation method or citric acid method showed a steady activity for dry reforming of methane under pressure. The importance and stability of cobalt metal with strontium carbonate were suggested for the Co–SrO catalyst, and thus it should be

  10. Sustainable production of acrolein: Gas-phase dehydration of glycerol over Nb 2O 5 catalyst

    Microsoft Academic Search

    Song-Hai Chai; Hao-Peng Wang; Yu Liang; Bo-Qing Xu

    2007-01-01

    Gas-phase dehydration of glycerol to produce acrolein was investigated at 315?°C over Nb2O5 catalysts calcined in the temperature range of 350–700?°C. The catalysts were characterized by nitrogen physisorption, TG-DTA, XRD, and n-butylamine titration using Hammett indicators to gain insight into the effect of calcination temperature on catalyst texture, crystal structure, and acidity. Calcination at 350 and 400?°C produced amorphous Nb2O5

  11. 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

    Robert L. Wolff; Frédérique Pédrono; Elodie Pasquier; Anne M. Marpeau

    2000-01-01

    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.

  12. Chemical Interactions in Multimetal/Zeolite Catalysts

    SciTech Connect

    Sachtler, Wolfgang M. H.

    2004-04-16

    This two-year project has led to a significant improvement in the fundamental understanding of the catalytic action of zeolite-supported redox catalysts. It turned out to be essential that we could combine four strategies for the preparation of catalysts containing transition metal (TM) ions in zeolite cavities: (1) ion exchange from aqueous solution; (2) chemical vapor deposition (CVD) of a volatile halide onto a zeolite in its acidic form; (3) solid state ion exchange; and (4) hydrothermal synthesis of a zeolite having TM ions in its lattice, followed by a treatment transporting these ions to ''guest positions''. Technique (2) enables us to position more TM ions into cavities than permitted by the conventional technique (1).viz one positive charge per Al centered tetrahedron in the zeolite lattice. The additional charge is compensated by ligands to the TM ions, for instance in oxo-ions such as (GaO){sup +} or dinuclear [Cu-O-Cu]{sup 2+}. While technique (3) is preferred over CVD where volatile halides are not available, technique (4) leads to rather isolated ''ex lattice'' oxo-ions. Such oxo-ions tend to be mono-nuclear, in contrast to technique (2) which preferentially creates dinuclear oxo-ions of the same TM element. A favorable element for the present research was that the PI is also actively engaged in a project on the reduction of nitrogen oxides, sponsored by EMSI program of the National Science Foundation and the US Department of Energy, Office of Science. This combination created a unique opportunity to test and analyze catalysts for the one step oxidation of benzene to phenol and compare them with catalysts for the reduction of nitrogen oxides, using hydrocarbons as the reductant. In both projects catalysts have been used which contain Fe ions or oxo-ions in the cavities the zeolite MFI, often called ZSM-5. With Fe as the TM-element and MFI as the host zeolite we found that catalysts with high Fe content, prepared by technique (2) were optimal for the De-NO{sub x} reaction, but extremely unselective for benzene oxidation to phenol. Conversely, the catalysts prepared with (4) had the highest turnover frequency for benzene oxidation, but performed very poorly for NO{sub x} reduction with so-butane. In fact the Fe concentration in the former catalysts were so low that it was necessary to design a special experimental program for the sole purpose of showing that it is really the Fe which catalyzes the benzene oxidation, not some acid center as has been proposed by other authors. For this purpose we used hydrogen sulfide to selectively poison the Fe sites, without deactivating the acidic sites. In addition we could show that the hydrothermal treatment of catalysts prepared by technique (4) is essential to transform iron ions in the zeolite lattice to ''ex lattice ions'' in guest positions. That line of the work required very careful experimentation, because a hydrothermal treatment of a zeolite containing Fe ions in its cavities can also lead to agglomeration of such ions to nano-particles of iron oxide which lowers the selectivity for the desired formation of phenol. This part of the program showed convincingly that indeed Fe is responsible for the benzene oxidation catalysis. The results and conclusion of this work, including the comparison of different catalysts, was published in a number of papers in the scientific literature, listed in the attached list. In these papers also our analysis of the reaction orders and the possible mechanism of the used test reaction are given.

  13. Pt/Ceria-based Catalysts for Small Alcohol Electrooxidation

    NASA Astrophysics Data System (ADS)

    Menendez-Mora, Christian L.

    High emissions of fossil-based energy sources have led to scientists around the world to develop new alternatives for the future. In this sense, fuel cells are a remarkable and promising energy option with less environmental impact. The most used fuels for this technology are hydrogen and small chain alcohols, which can be oxidized to transform their chemical energy into electrical power. To do this, fuel cells need catalysts that will act as an active surface where the oxidation can take place. The problem with platinum catalysts is its possible CO poisoning with intermediates that are produced before the complete oxidation of alcohol to CO2. Different approaches have been taken to try to resolve this issue. In this case, cerium oxide (ceria) was selected as a co-catalyst to mitigate the effect of CO poisoning of platinum. Ceria is a compound that has the ability to work as an "oxygen tank" and can donate oxygen to carbon monoxide that is strongly adsorbed at platinum surface to produce CO2 (carbon dioxide), regenerating the Pt surface for further alcohol oxidation. Therefore, enhancing the current density as well as the power output of a fuel cell. First, an occlusion deposition technique was used to prepare platinum/ceria composite electrodes and tested them towards small chain alcohol oxidation such as methanol oxidation reaction in acidic and alkaline media. The preliminary results demonstrated that the Pt/ceria electrodes were more efficient towards methanol electrooxidation when compared to Pt electrodes. This enhancement was attributed to the presence of ceria. A second preparation method was selected for the synthesis of ceria/Pt catalysts. In this case, a hydrothermal method was used and the catalysis were studied for the effect of MeOH, EtOH and n-BuOH oxidation. The observed effect was that electrodes made of Pt/Pt:CeO2-x showed better catalytic effect than Pt/ceria and platinum electrodes. Moreover, a comparison between ceria nanorods versus nanoparticles as substrates was done. The general result was that ceria nanoparticles showed better electrocatalytic behavior towards the oxidation of methanol in alkaline medium. Finally, as an outreach activity, an educational module to reinforce the electrochemical concepts in the General Chemistry Laboratory course at UPR-RP was developed. The module was based on Volta's Experiment and an improvement on students learning was detected when comparing this activity with the normal Daniel's cell experience that is used in most Universities at the undergraduate level. In summary, the findings of this thesis conclude that ceria is a compound that may enhance platinum catalytic activity by CO oxidation, promoting the oxidation of alcohols in acidic and alkaline medium. Moreover, catalysis depends on the morphology of the ceria that is used as the catalysts support.

  14. Catalyst compositional for hydroprocessing petroleum feedstocks

    SciTech Connect

    Sherwood, D.E.; Bartley, B.H.; Neff, L.D.; Dai, P.S.E.

    1992-03-10

    This patent describes a catalyst composition useful in the hydroprocessing of a sulfur- and metal-containing hydrocarbon feedstock. It comprises 1.0-5.0 weight percent of an oxide of nickel or cobalt and 10.0-25.0 weight percent of an oxide of molybdenum, all supported on a porous alumina support in such a manner that the molybdenum gradient of the catalyst has a value of less than 6.0, 15-30% of the nickel or cobalt is in an acid extractable form, and the catalyst is further characterized by having a total surface area of 150-210 m{sup 2}/g, a total pore volume of 0.50-0.75 cc/g, and a pore size distribution such that pores having diameters of less than 100A constitute less than 25.0%, pores having diameters of 100-160A constitute 70.0-85.0% and pores having diameters of greater than 250A constitute 1.0-15.0% of the total pore volume of the catalyst.

  15. Reforming using erionite catalysts

    SciTech Connect

    Liers, J.; Meusinger, J.; Moesch, A. (Univ. of Leipzig (Germany)); Reschetilowski, W. (Karl Winnacker Inst. of DECHEMA, Frankfurt (Germany))

    1993-08-01

    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.

  16. Performance of bimetal catalysts

    SciTech Connect

    NONE

    1995-10-01

    This article describes how both laboratory and engine dynamometer testing were used to characterize the relative impacts of platinum, palladium, and rhodium on catalyst performance. Catalyst design requires detailed knowledge of the influence of noble metal interactions on over-all performance. Modern three-way catalysts invariably contain two and, in some cases, three precious metals (PMs). Bimetal combinations typically combine rhodium (Rh) with either platinum (Pt) or palladium (Pd). While all three are active for the reactions required in the various exhaust-gas-component conversions to CO{sub 2}, H{sub 2}O, and N{sub 2}, some PMs are more effective than others: Rh is particularly effective for NOx reduction to N{sub 2}, while Pt is good for saturated HC conversion. The presence of two PMs introduces the possibility of interactions such as alloy formation, which has been said, in other experiments, to have both negative and positive effects on performance. Researchers at AlliedSignal Environmental Catalysts examined the validity of such claims, and have analyzed the impact of Pt-Rh and Pd-Rh interactions and alloy formation on overall performance for aged catalysts. They used laboratory evaluation in full-complement, synthetic, exhaust gas mixture and dynamometer testing after engine aging.

  17. Comparison Of Asymmetric Hydrogenations Of Unsaturated- Carboxylic Acids And -Esters

    PubMed Central

    Khumsubdee, Sakunchai; Burgess, Kevin

    2013-01-01

    As methodology development matures it can be difficult to discern the most effective ways of performing certain transformations from the rest. This review summarizes the most important contributions leading to asymmetric hydrogenations of simple unsaturated-acid and ester substrates, with the objective of highlighting at least the best types of catalysts for each. Achievements in the area are described and these reveal situations where further efforts should be worthwhile, and ones where more research is only likely to give diminishing returns. In general, our conclusions are that the most useful types of catalysts for unsaturated-acids and -esters tend to be somewhat different, simple substrates have been studied extensively, and the field is poised to address more complex reactions. These could be ones involving alternative, particularly cyclic, structures, chemoselectivity issues, and more complex substrate stereochemistries. PMID:24729943

  18. Combined Acid Catalysis for Asymmetric Synthesis

    E-print Network

    Johnson, Jeff S.

    Combined Acid Catalysis for Asymmetric Synthesis Michael T. Corbett University of North Carolina, 44, 1924­1942. Limitations of classical Brønsted/Lewis Acid catalysis: · Poor reactivity (low acidity) · Low selectivity · High catalyst loading R X R X HMLn X Lewis Acid Catalysis Brønsted Acid Catalysis X

  19. Weak Acid Ionization Constants and the Determination of Weak Acid-Weak Base Reaction Equilibrium Constants in the General Chemistry Laboratory

    ERIC Educational Resources Information Center

    Nyasulu, Frazier; McMills, Lauren; Barlag, Rebecca

    2013-01-01

    A laboratory to determine the equilibrium constants of weak acid negative weak base reactions is described. The equilibrium constants of component reactions when multiplied together equal the numerical value of the equilibrium constant of the summative reaction. The component reactions are weak acid ionization reactions, weak base hydrolysis…

  20. Design of a high activity and selectivity alcohol catalyst. Final status report and summary of accomplishments

    SciTech Connect

    Foley, H.C.; Mills, G.A.

    1994-07-15

    This final DOE report for grant award number DE-FG22-90PC 90291 presents the results of our efforts to better understand the Rh-Mo/{gamma}-Al{sub 2}O3 catalytic system for the hydrogenation of carbon monoxide and carbon dioxide to selectively form oxygenated products. The content of this report is divided into three major sections and a fourth, concluding section which addresses our major research accomplishments, as well as documents the most significant publications and presentations associated with this grant. The three main sections which make up the body of this report are presented in the in form of manuscripts which, in turn, summarize our progress in three areas of this project. The three body sections are organized as follows: Section I--Evidence for site isolation in Rh-Mo bimetallic catalysts derived from organometallic clusters; Section II--Surface Chemistry of Rh-Mo/{gamma}-Al{sub 2}O{sub 3}: An analysis of surface acidity; and Section III--Comparative study of Rh/Al{sub 2}O{sub 3} and Rh-Mo/Al{sub 2}O{sub 3} Catalysts. Section IV summarizes major accomplishments. The content of this final report is meant to generally highlight our progress in both characterizing the nature of the Rh-Mo/Al{sub 2}O{sub 3} system and probing its reactivity for insight on the oxygenate synergy present in this class of catalysts.

  1. Characterization and catalyst development, an interactive approach

    Microsoft Academic Search

    S. A. Bradley; M. J. Gattuso; R. J. Bertolacini

    1989-01-01

    This book presents a perspective on catalyst development. Some chapters characterize the catalyst prior to plant evaluation, whereas others utilize characterization to explain performance variances. Some new types of catalysts incorporated into this volume include the preparation of novel catalyst supports based on alumina and hydrous titanates. Attrition-resistant catalysts and ultrafine ceramics were prepared by modified spray-drying methods. New catalyst

  2. Identification of key amino acid residues in Neisseria polysaccharea amylosucrase.

    PubMed

    Sarçabal, P; Remaud-Simeon, M; Willemot, R; Potocki de Montalk, G; Svensson, B; Monsan, P

    2000-05-26

    Amylosucrase from Neisseria polysaccharea catalyzes the synthesis of an amylose-like polymer from sucrose. Sequence alignment revealed that it belongs to the glycoside hydrolase family 13. Site-directed mutagenesis enabled the identification of functionally important amino acid residues located at the active center. Asp-294 is proposed to act as the catalytic nucleophile and Glu-336 as general acid base catalyst in amylosucrase. The conserved Asp-401, His-195 and His-400 residues are critical for the enzymatic activity. These results provide strong support for the predicted close structural and functional relationship between the sucrose-glucosyltransferases and enzymes of the alpha-amylase family. PMID:10828446

  3. Technology development for iron Fischer-Tropsch catalysts. Quarterly technical progress report for period ending December 1993

    SciTech Connect

    O`Brien, R.J.; Xu, Liguang; Bi, Xiangxin; Eklund, P.; Davis, B.H.

    1993-12-31

    Conversion data as a function of time of synthesis for the two catalysts are shown in Figures 2 and 3. In general the precipitated catalyst is more active than the iron carbide catalyst with syn-gas conversions starting at 80% as compared to 50% for the latter; however, both catalysts deactivated with increasing reaction time. A comparison of the C{sub 2}, C{sub 3} and C{sub 4} olefin selectivities at 26% CO conversion (precipitated catalyst-336 hr of synthesis, iron carbide catalyst-122 hr of synthesis) are shown in Figure 4. Surprisingly the precipitated catalyst had a higher olefin content than the iron carbide catalyst. It has been reported that a similar iron carbide catalyst has higher selectivity for the production of olefins than a ``conventionally prepared`` Fe/Co catalyst. The discrepancy may be due in part to comparing the olefin selectivity of the two catalysts at different conversions. Their ``conventional catalyst`` had a C{sub 2}{minus}C{sub 4} olefin content of 37% at 72% conversion compared to 86% olefin at 55% conversion for the iron carbide catalyst. In general the olefin selectivity of a catalyst is highest at low conversions. The iron carbide catalyst of this study produces more hydrocarbons than the precipitated catalyst; furthermore, it produces a higher fraction of C{sub 3} + (86% vs. 84%) and C{sub 5}+ (67% vs. 61%) hydrocarbons (Figure 5). Correspondingly, the iron carbide catalyst produces less methane and ethane than the precipitated catalyst (Figure 6). These hydrocarbon and C{sub 5}+ selectivities are similar to those reported earlier.

  4. Syntheses and applications of soluble polyisobutylene (PIB)-supported transition metal catalysts

    E-print Network

    Tian, Jianhua

    2009-05-15

    that of their low molecular weight analogs in Mukaiyama epoxidation of olefins. Carboxylic acid terminated PIB derivatives can act as carboxylate ligands for Rh(II) cyclopropanation catalysts. An achiral PIB-supported Rh(II) carboxylate catalyst showed good activity...

  5. Regeneration of a deactivated USY alkylation catalyst using supercritical isobutane

    SciTech Connect

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

    2005-01-01

    Off-line, in-situ alkylation activity recovery from a completely deactivated solid acid catalyst was examined in a continuous-flow reaction system employing supercritical isobutane. A USY zeolite catalyst was initially deactivated during the liquid phase alkylation of butene with isobutane in a single-pass reactor and then varying amounts of alkylation activity were recovered by passing supercritical isobutane over the catalyst bed at different reactivation conditions. Temperature, pressure and regeneration time were found to play important roles in the supercritical isobutane regeneration process when applied to a completely deactivated USY zeolite alkylation catalyst. Manipulation of the variables that influence solvent strength, diffusivity, surface desorption, hydride transfer rates, and coke aging, strongly influence regeneration effectiveness.

  6. Use of ionic liquids as coordination ligands for organometallic catalysts

    DOEpatents

    Li, Zaiwei (Moreno Valley, CA); Tang, Yongchun (Walnut, CA); Cheng; Jihong (Arcadia, CA)

    2009-11-10

    Aspects of the present invention relate to compositions and methods for the use of ionic liquids with dissolved metal compounds as catalysts for a variety of chemical reactions. Ionic liquids are salts that generally are liquids at room temperature, and are capable of dissolving a many types of compounds that are relatively insoluble in aqueous or organic solvent systems. Specifically, ionic liquids may dissolve metal compounds to produce homogeneous and heterogeneous organometallic catalysts. One industrially-important chemical reaction that may be catalyzed by metal-containing ionic liquid catalysts is the conversion of methane to methanol.

  7. Activated Carbon Catalysts for the Production of Hydrogen for the Sulfur-Iodine Thermochemical Water Splitting Cycle

    SciTech Connect

    Lucia M. Petkovic; Daniel M. Ginosar; Harry W. Rollins; Kyle C Burch; Cristina Deiana; Hugo S. Silva; Maria F. Sardella; Dolly Granados

    2009-05-01

    Seven activated carbon catalysts obtained from a variety of raw material sources and preparation methods were examined for their catalytic activity to decompose hydroiodic acid (HI) to produce hydrogen; a key reaction in the sulfur-iodine (S-I) thermochemical water splitting cycle. Activity was examined under a temperature ramp from 473 to 773 K. Within the group of ligno-cellulosic steam-activated carbon catalysts, activity increased with surface area. However, both a mineral-based steam-activated carbon and a ligno-cellulosic chemically-activated carbon displayed activities lower than expected based on their higher surface areas. In general, ash content was detrimental to catalytic activity while total acid sites, as determined by Bohem’s titrations, seemed to favor higher catalytic activity within the group of steam-activated carbons. These results suggest, one more time, that activated carbon raw materials and preparation methods may have played a significant role in the development of surface characteristics that eventually dictated catalyst activity and stability as well.

  8. Transition state stabilization by general acid catalysis, water expulsion, and enzyme reorganization in Medicago savita chalcone isomerase

    PubMed Central

    Hur, Sun; Newby, Zachary E. R.; Bruice, Thomas C.

    2004-01-01

    In aqueous solution, Medicago savita chalcone isomerase (CHI) enhances the reaction rate for the unimolecular rearrangement of chalcone (CHN) into flavanone by seven orders of magnitude. Conformations of CHN and their relative free energies in water and CHI were investigated by the thermodynamic perturbation method. In water, CHN adopts two conformations (I and II) with conformation I being higher in energy than conformation II by 3 kcal/mol. Only I can give rise to a near attack conformer (NAC) where the nucleophile O2? and the electrophile C9 are placed in proximity. In CHI, I binds less tightly than II by ?2 kcal/mol, resulting in the free energy for NAC formation being ?2 kcal/mol higher in the enzyme than in water. This unfavorable feature in the ground state of the CHI reaction requires the predominant catalytic advantage to be taken in the step of NAC ? transition state (TS). From the molecular dynamics simulations of apo-CHI, CHI complexed with CHN (CHI·CHN) and CHI·TS, we found: (i) Lys-97-general-acid catalysis of the O2?- nucleophilic addition; (ii) expulsion of three water molecules in the process of TS formation; (iii) release of enzyme structural distortion on TS formation. In the conclusion, CHI's remarkable efficiency of stabilizing the TS and its relatively poor ability in organizing the ground state is compared with chorismate mutase whose catalytic prowess, when compared with water, originates predominantly from the enhanced NAC population at the active site. PMID:14978275

  9. Measurement of respiratory morbidity in general practice in the United Kingdom during the acid transport event of January 1985

    SciTech Connect

    Ayres, J.; Fleming, D.; Williams, M.; McInnes, G.

    1989-02-01

    The Weekly Returns System of the Royal College of General Practitioners was used to assess the effect on respiratory illness of the acid transport event that occurred during January 1985. The pollution event, as assessed by SO/sub 2/ and smoke levels measured at pollution monitoring stations within and without the affected area showed only modest rises in SO/sub 2/ levels, which were less than levels that occurred 4 years earlier. January is the peak time of year for reporting of acute respiratory episodes, and the minor increase in pollution was not reflected in any rise in respiratory morbidity, both for all ages and for different age bands. There was a rise in rates for children up to the age of 14, but this was seen each year and in both polluted and nonpolluted areas. This was probably due to children returning to school after the winter vacation and the subsequent spread of viral infections. The limitations of the two data sets in this analysis are discussed, including the relative insensitivity of weekly data in picking out a short-lived event, the distribution of the practices and pollution monitoring stations, and the effect of the extreme cold weather and the coal miners' strike on domestic coal burning during this event.

  10. Long-chain polyunsaturated fatty acids have a positive effect on the quality of general movements of healthy term infants1-3

    Microsoft Academic Search

    Hylco Bouwstra; Janneke Dijck-Brouwer; Hendrika M Tjoonk; Jolanda C van der Heide; Frits AJ Muskiet; Mijna Hadders-Algra

    Background: Whether long-chain polyunsaturated fatty acids (LCPs) play a role in the development of the young nervous sys- tem in term infants is debated. Objective: We investigated whether supplementation of formula with LCPs for 2 mo improves the quality of general movements (GMs) in healthy term infants at 3 mo of age. Design: A prospective, double-blind, randomized controlled study was

  11. The effect of copper and zinc at neutral and acidic pH on the general haematology and osmoregulation of Oreochromis mossambicus

    Microsoft Academic Search

    G Nussey; J HJ van Vuren; H H du Preez

    2002-01-01

    The objective of this study was to determine the effect of sublethal copper and zinc concentrations at a neutral and an acidic pH, on selected haematological parameters as well as on the total osmolality and electrolyte concentrations of Oreochromis mossambicus. In general, at neutral pH copper and zinc caused blood acidosis, increases in circulating white blood cell numbers, causing stimulation

  12. Deep eutectic solvents and glycerol: a simple, environmentally benign and efficient catalyst\\/reaction media for synthesis of N-aryl phthalimide derivatives

    Microsoft Academic Search

    Hyacintha Rennet Lobo; Balvant Shyam Singh; Ganapati Subray Shankarling

    2012-01-01

    Deep eutectic solvents (DES) and glycerol have been successfully employed as efficient catalysts\\/reaction media in the synthesis of N-aryl phthalimide derivatives from phthalic anhydride and primary aromatic amines. The DES prepared from choline chloride and malonic acid proved to be an efficient catalyst whereas glycerol and the DES of choline chloride and urea played a dual role of catalyst and

  13. Function-Oriented Investigations of a Peptide-Based Catalyst that Mediates Enantioselective Allylic Alcohol Epoxidation.

    PubMed

    Abascal, Nadia C; Lichtor, Phillip A; Giuliano, Michael W; Miller, Scott J

    2014-11-01

    We detail an investigation of a peptide-based catalyst 6 that is effective for the site- (>100:1:1) and enantioselective epoxidation (86% ee) of farnesol. Studies of the substrate scope exhibited by the catalyst are included, along with an exploration of optimized reaction conditions. Mechanistic studies are reported, including relative rate determinations for the catalyst and propionic acid, a historical perspective, truncation studies, and modeling using NMR data. Our compiled data advances our understanding of the inner workings of a catalyst that was identified through combinatorial means. PMID:25386335

  14. Lewis acid promoted ruthenium(II)-catalyzed etherifications by selective hydrogenation of carboxylic acids/esters.

    PubMed

    Li, Yuehui; Topf, Christoph; Cui, Xinjiang; Junge, Kathrin; Beller, Matthias

    2015-04-20

    Ethers are of fundamental importance in organic chemistry and they are an integral part of valuable flavors, fragrances, and numerous bioactive compounds. In general, the reduction of esters constitutes the most straightforward preparation of ethers. Unfortunately, this transformation requires large amounts of metal hydrides. Presented herein is a bifunctional catalyst system, consisting of Ru/phosphine complex and aluminum triflate, which allows selective synthesis of ethers by hydrogenation of esters or carboxylic acids. Different lactones were reduced in good yields to the desired products. Even challenging aromatic and aliphatic esters were reduced to the desired products. Notably, the in?situ formed catalyst can be reused several times without any significant loss of activity. PMID:25728921

  15. Catalyst, 2000-01.

    ERIC Educational Resources Information Center

    Ryan, Barbara E., Ed.

    2001-01-01

    "Catalyst" is a publication designed to assist higher education in developing alcohol and other drug prevention polices and programs that will foster students' academic and social development and promote campus and community safety. Issue 1 of volume 6 introduces a series of "Presidential Profiles" in which university presidents describe their…

  16. Intercalated clay catalysts

    Microsoft Academic Search

    T. J. Pinnavaia

    1983-01-01

    Recent advances in the intercalation of metal complex cations in smectite clay minerals are leading to the development of new classes of selective heterogeneous catalysts. The selectivity of both metal-catalyzed and proton-catalyzed chemical conversions in clay intercalates can often be regulated by controlling surface chemical equilibria, interlamellar swelling, or reactant pair proximity in the interlayer regions. Also, the intercalation of

  17. Noble metal ionic catalysts.

    PubMed

    Hegde, M S; Madras, Giridhar; Patil, K C

    2009-06-16

    Because of growing environmental concerns and increasingly stringent regulations governing auto emissions, new more efficient exhaust catalysts are needed to reduce the amount of pollutants released from internal combustion engines. To accomplish this goal, the major pollutants in exhaust-CO, NO(x), and unburned hydrocarbons-need to be fully converted to CO(2), N(2), and H(2)O. Most exhaust catalysts contain nanocrystalline noble metals (Pt, Pd, Rh) dispersed on oxide supports such as Al(2)O(3) or SiO(2) promoted by CeO(2). However, in conventional catalysts, only the surface atoms of the noble metal particles serve as adsorption sites, and even in 4-6 nm metal particles, only 1/4 to 1/5 of the total noble metal atoms are utilized for catalytic conversion. The complete dispersion of noble metals can be achieved only as ions within an oxide support. In this Account, we describe a novel solution to this dispersion problem: a new solution combustion method for synthesizing dispersed noble metal ionic catalysts. We have synthesized nanocrystalline, single-phase Ce(1-x)M(x)O(2-delta) and Ce(1-x-y)Ti(y)M(x)O(2-delta) (M = Pt, Pd, Rh; x = 0.01-0.02, delta approximately x, y = 0.15-0.25) oxides in fluorite structure. In these oxide catalysts, Pt(2+), Pd(2+), or Rh(3+) ions are substituted only to the extent of 1-2% of Ce(4+) ion. Lower-valent noble metal ion substitution in CeO(2) creates oxygen vacancies. Reducing molecules (CO, H(2), NH(3)) are adsorbed onto electron-deficient noble metal ions, while oxidizing (O(2), NO) molecules are absorbed onto electron-rich oxide ion vacancy sites. The rates of CO and hydrocarbon oxidation and NO(x) reduction (with >80% N(2) selectivity) are 15-30 times higher in the presence of these ionic catalysts than when the same amount of noble metal loaded on an oxide support is used. Catalysts with palladium ion dispersed in CeO(2) or Ce(1-x)Ti(x)O(2) were far superior to Pt or Rh ionic catalysts. Therefore, we have demonstrated that the more expensive Pt and Rh metals are not necessary in exhaust catalysts. We have also grown these nanocrystalline ionic catalysts on ceramic cordierite and have reproduced the results we observed in powder material on the honeycomb catalytic converter. Oxygen in a CeO(2) lattice is activated by the substitution of Ti ion, as well as noble metal ions. Because this substitution creates longer Ti-O and M-O bonds relative to the average Ce-O bond within the lattice, the materials facilitate high oxygen storage and release. The interaction among M(0)/M(n+), Ce(4+)/Ce(3+), and Ti(4+)/Ti(3+) redox couples leads to the promoting action of CeO(2), activation of lattice oxygen and high oxygen storage capacity, metal support interaction, and high rates of catalytic activity in exhaust catalysis. PMID:19425544

  18. Studies in hydrocarboxylation of styrene and derivatives using palladium complex catalysts

    E-print Network

    Li, Yuanchun

    2010-07-15

    Carbonylation of aryl olefins and alcohols using homogeneous Pd catalysts has gained considerable interest due to their important applications in the synthesis the non-steroidal anti-inflammatory drugs consisting of 2-arylpropionic acids (e...

  19. Synthesis of Mesoporous Aluminophosphates as Potential Catalysts in the Upgrading Petroleum Feedstocks

    SciTech Connect

    Ingram, Conrad, PH.D.

    2002-03-20

    This project focuses on the synthesis of mesoporous aluminophosphate (AlPO) catalysts for application in the acid catalyzed conversion of large petroleum feedstock compounds to Useful middle distillates and naphtha transportation fuels.

  20. Effective Synthesis of tert-Butyl-Substituted 3Carboxy Coumarins in Water Using TEBAC as Catalyst

    Microsoft Academic Search

    Yang Li; Wentao Gao

    2012-01-01

    A facile synthesis of novel tert-butyl substituted 3-carboxycoumarin derivatives is described, featuring the one-pot reaction of tert-butyl substituted salicylaldehydes with Meldrum's acid in water using triethylbenzyl ammonium chloride (TEBAC) as catalyst.

  1. Bulk crush testing of catalysts

    SciTech Connect

    Bradley, S.A. (Allied-Signal Engineered Materials Research Center, Des Plaines, IL (USA)); Koves, W.J. (UOP Inc., Des Plaines, IL (USA)); Pitzer, E.

    1988-09-01

    Catalysts have to be sufficiently strong to endure the rigors of handling and use. For examples, the catalyst must be strong enough to withstand the loading into a reactor. The catalyst also cannot attrite or breakup due to the weight of the bed, gas flow, catalyst movement in continuous processes or thermal expansion and contractions of the bed and container vessel. If a physical breakdown were to occur, the resulting fines formation could produce a pressure drop across the reactor as well as causing flow maldistribution. Channeling or maldistribution through the bed decreases reactor performance because of reduced catalyst contract and reduction of products of reaction. When required, evaluation of the mechanical properties of catalysts by both users and producers requires the utilization of identical test methods. To evaluate the mechanical properties of catalysts and catalyst precursors, the ASTM D-32 Committee on Catalysts has prepared several test methods that meet the criteria of acceptable interlaboratory reproducibility. Some of these methods for evaluating the physical characteristics of a catalyst include attrition and abrasion (D4058), single pellet crush strength (D4174), vibrated packing density (D4180 and D4512), and particle size analysis (D4438, D4464 and D4513). One physical property determination that has proved most difficult to standardize has been the bulk crush strength of a catalyst bed. This paper will describe the experimental problems associated with this determination as well as the development of a new test cell that significantly improves the interlaboratory reproducibility.

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

    PubMed Central

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

    2013-01-01

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

  3. Glucose production from hydrolysis of cellulose over a novel silica catalyst under hydrothermal conditions.

    PubMed

    Wang, Huayu; Zhang, Changbin; He, Hong; Wang, Lian

    2012-01-01

    A novel silica catalyst was synthesized by evaporation-induced self-assembly (EISA) method and tested for the catalytic selective hydrolysis of cellulose to glucose. This silica catalyst exhibited a higher catalytic activity than other oxides prepared by the same method, such as ZrO2, TiO2, and Al2O3. Using silica as a catalyst, cellulose was selectively hydrolyzed into glucose with a glucose yield as high as 50% under hydrothermal conditions without hydrogen gas. The silica catalyst was characterized by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results of temperature-programmed desorption of ammonia (NH3-TPD) and textural properties indicated that the synergistic effect between strong acidity and a suitable pore diameter of the silica catalyst may be responsible for its high activity. In addition, the catalyst was recyclable and showed excellent stability during the recycle catalytic runs. PMID:22655361

  4. Liquid-phase oxidation of propylene to propylene glycol acetates over Pd\\/C and Pt?Pd\\/C: Effect of platinum on catalyst activity and metal dispersity

    Microsoft Academic Search

    A. V. Karandin; E. V. Gusevskaya; V. A. Likholobov; E. M. Moroz; V. I. Zaikovskii

    1992-01-01

    Kinetics of oxidation of propylene to propylene glycol and its acetates in acetic acid solutions of lithium nitrate over Pd\\/C and Pd?Pt\\/C catalysts has been studied. Catalysts were investigated using X-ray phase analysis and electron microscopy. Platinum introduction into catalyst increases the metal dispersity and the catalyst stability but produces no effect on the nature of surface sites active in

  5. Calorimetric study of vanadium pentoxide catalysts used in the reaction of ethane oxidative dehydrogenation

    Microsoft Academic Search

    J. Le Bars; J. C. Vedrine; A. Auroux; B. Pommier; G. M. Pajonk

    1992-01-01

    Vanadium pentoxide catalysts have been studied in the partial oxidation reaction of ethane in the 723-843 K temperature range. The relationship between the acid-base properties and the catalytic behavior was investigated. The number and character of acidic sites of VâOâ catalysts were determined by studying the adsorption of a basic molecule using microcalorimetry. The reducibility level and the evolution of

  6. Preparation and characterization of Fischer–Tropsch active Co\\/SiO 2 catalysts

    Microsoft Academic Search

    Barbara Ernst; Suzanne Libs; Patrick Chaumette; Alain Kiennemann

    1999-01-01

    Silica supported cobalt catalysts have been prepared by a new method combining the precipitation of the metal precursor (cobalt nitrate) by oxalic acid with the hydrolysis and condensation of the silicium precursor (tetraethoxysilane). Depending on the pH during preparation, the textural properties (BET specific surface area, porosity) of the Co\\/SiO2 catalysts can be modified. In an acid medium (pathway A),

  7. JV 58-Effects of Biomass Combustion on SCR Catalyst

    SciTech Connect

    Bruce C. Folkedahl; Christopher J. Zygarlicke; Joshua R. Strege; Donald P. McCollor; Jason D. Laumb; Lingbu Kong

    2006-08-31

    A portable slipstream selective catalytic reduction (SCR) reactor was installed at a biomass cofired utility boiler to examine the rates and mechanisms of catalyst deactivation when exposed to biomass combustion products. The catalyst was found to deactivate at a much faster rate than typically found in a coal-fired boiler, although this may have been the result of high ash loading rather than a general property of biomass combustion. Deactivation was mainly the result of alkali and alkaline-earth sulfate formation and growth in catalyst pores, apparently caused by alkaline-earth ash deposition on or near the pore sites. The high proportion of biomass in the fuel contributed to elevated levels of alkali and alkaline-earth material in the ash when compared to coal ash, and these higher levels provided more opportunity for sulfate formation. Based on laboratory tests, neither catalyst material nor ammonia contributed measurably to ash mass gains via sulfation. A model constructed using both field and laboratory data was able to predict catalyst deactivation of catalysts under subbituminous coal firing but performed poorly at predicting catalyst deactivation under cofiring conditions. Because of the typically higher-than coal levels of alkali and alkaline-earth elements present in biomass fuels that are available for sulfation at typical SCR temperatures, the use of SCR technology and biomass cofiring needs to be carefully evaluated prior to implementation.

  8. Design criteria for stable Pt/C fuel cell catalysts

    PubMed Central

    Katsounaros, Ioannis; Witte, Jonathon; Bongard, Hans J; Topalov, Angel A; Baldizzone, Claudio; Mezzavilla, Stefano; Schüth, Ferdi

    2014-01-01

    Summary Platinum and Pt alloy nanoparticles supported on carbon are the state of the art electrocatalysts in proton exchange membrane fuel cells. To develop a better understanding on how material design can influence the degradation processes on the nanoscale, three specific Pt/C catalysts with different structural characteristics were investigated in depth: a conventional Pt/Vulcan catalyst with a particle size of 3–4 nm and two Pt@HGS catalysts with different particle size, 1–2 nm and 3–4 nm. Specifically, Pt@HGS corresponds to platinum nanoparticles incorporated and confined within the pore structure of the nanostructured carbon support, i.e., hollow graphitic spheres (HGS). All three materials are characterized by the same platinum loading, so that the differences in their performance can be correlated to the structural characteristics of each material. The comparison of the activity and stability behavior of the three catalysts, as obtained from thin film rotating disk electrode measurements and identical location electron microscopy, is also extended to commercial materials and used as a basis for a discussion of general fuel cell catalyst design principles. Namely, the effects of particle size, inter-particle distance, certain support characteristics and thermal treatment on the catalyst performance and in particular the catalyst stability are evaluated. Based on our results, a set of design criteria for more stable and active Pt/C and Pt-alloy/C materials is suggested. PMID:24605273

  9. The acrylation of glycerol over solid base catalysts: A precursor to functionalized lipids

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Transesterification of lipids using lipases is a common strategy used to incorporate novel acids into triacylglycerides. This approach, however, is limited to acids with pKa’s similar to common fatty acids. To overcome this limitation, we have used heterogeneous basic catalysts for the synthesis o...

  10. The Enolase Superfamily: A General Strategy for Enzyme-Catalyzed Abstraction of the R-Protons of Carboxylic Acids

    E-print Network

    Rayment, Ivan

    -Protons of Carboxylic Acids Patricia C. Babbitt,*, Miriam S. Hasson,§,| Joseph E. Wedekind,,# David R. J. Palmer by their ability to catalyze the abstraction of the R-proton of a carboxylic acid to form an enolic intermediate specialized enzymes: mandelate racemase, galactonate dehydratase, glucarate dehydratase, muconate

  11. Ion-exchange membrane fouling by boric acid in the electrodialysis of nickel electroplating rinsing waters: generalization of our results

    Microsoft Academic Search

    Kamel-Eddine Bouhidel; Michel Rumeau

    2004-01-01

    This research investigated electrodialysis membrane fouling (EDMF) by boric acid during nickel salts electrodialysis (ED). This process is used in the nickel electroplating (EP) industry to concentrate and reuse nickel salts and to recycle treated rinse waters. Boric acid is an essential component of the nickel EP bath (Watts bath). Membrane fouling by organics (e.g., brighteners) is a well known

  12. The H[subscript 3]PO[subscript 4] Acid Ionization Reactions: A Capstone Multiconcept Thermodynamics General Chemistry Laboratory Exercise

    ERIC Educational Resources Information Center

    Nyasulu, Frazier; Barlag, Rebecca; Wise, Lindy; McMills, Lauren

    2013-01-01

    The thermodynamic properties of weak acid ionization reactions are determined. The thermodynamic properties are corresponding values of the absolute temperature (T), the weak acid equilibrium constant (K[subscript a]), the enthalpy of ionization (delta[subscript i]H[degrees]), and the entropy of ionization (delta[subscript i]S[degrees]). The…

  13. Effect of Organic Acid Additions on the General and Localized Corrosion Susceptibility of Alloy 22 in Chloride Solutions

    SciTech Connect

    Carranza, R M; Giordano, C M; Rodr?guez, M A; Ilevbare, G O; Rebak, R B

    2007-08-28

    Electrochemical studies such as cyclic potentiodynamic polarization (CPP) and electrochemical impedance spectroscopy (EIS) were performed to determine the corrosion behavior of Alloy 22 (N06022) in 1M NaCl solutions at various pH values from acidic to neutral at 90 C. All the tested material was wrought Mill Annealed (MA). Tests were also performed in NaCl solutions containing weak organic acids such as oxalic, acetic, citric and picric. Results show that the corrosion rate of Alloy 22 was significantly higher in solutions containing oxalic acid than in solutions of pure NaCl at the same pH. Citric and picric acids showed a slightly higher corrosion rate, and acetic acid maintained the corrosion rate of pure chloride solutions at the same pH. Organic acids revealed to be weak inhibitors for crevice corrosion. Higher concentration ratios, compared to nitrate ions, were needed to completely inhibit crevice corrosion in chloride solutions. Results are discussed considering acid dissociation constants, buffer capacity and complex formation constants of the different weak acids.

  14. Improved hydrous oxide ion-exchange compound catalysts

    DOEpatents

    Dosch, R.G.; Stephens, H.P.

    1986-04-09

    Disclosed is 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 exchanged with a catalytically effective quantity of a catalyst metal, and which has been subsequently treated with a solution of a Bronsted acid.

  15. THE NATURE OF HYDROGEN IN RANEY NICKEL CATALYSTS

    Microsoft Academic Search

    IOAN NICOLAU

    1976-01-01

    The amount and nature of hydrogen in Raney nickel catalysts were determined by various methods: thermal desorption in a volumetric apparatus, temperature-programmed desorption using argon as a carrier gas and techniques similar to those of Amenomiya and Cvetanovic, hydrogen-deuterium exchange, dissolution in acids and other methods. Most of the hydrogen removed in thermal desorption can not be readsorbed. Desorption was

  16. Production of biodiesel from soapstock using an ion-exchange resin catalyst

    Microsoft Academic Search

    Ji-Yeon Park; Deog-Keun Kim; Zhong-Ming Wang; Joon-Pyo Lee; Soon-Chul Park; Jin-Suk Lee

    2008-01-01

    The feasibility of biodiesel production from soapstock containing high water content and fatty matters by a solid acid catalyst\\u000a was investigated. Soapstock was converted to high-acid acid oil (HAAO) by the hydrolysis by KOH and the acidulation by sulfuric\\u000a acid. The acid value of soapstock-HAAO increased to 199.1 mg KOH\\/g but a large amount of potassium sulfate was produced. To

  17. Catalyst composition and method for hydroprocessing petroleum feedstocks

    SciTech Connect

    Sherwood, D.E.; Bartley, B.H.; Neff, L.D.; Dai, P.S.

    1991-09-10

    This patent describes a method for the hydroprocessing of a sulfur and metalcontaining hydrocarbon feed. It comprises contacting the feed with hydrogen and a catalyst in a manner such that the catalyst is maintained at isothermal conditions and is exposed to a uniform quality of feed, where the catalyst has a composition comprising 1.0-5.0 weight percent of an oxide of nickel or cobalt and 10.0-25.0 weight percent of an oxide of molybdenum, all supported on a porous alumina support in such a manner that the molybdenum gradient of the catalyst has a value of less than 6.0, 15-30% of the nickel or cobalt is in an acid extractable form, and the catalyst is further characterized by having a total surface area of 150-210 m{sup 2}/g, a total pore volume of 0.50-0.75 cc/g, and a pore size distribution such that pores having diameters of less than 100A constitute less than 25.0%, pores having diameters of 100-160A constitute 70.0-85.0% and pores having diameters of greater than 250A constitute 1.0-15.0% of the total pore volume of the catalyst.

  18. Removal of free fatty acid in Azadirachta indica (Neem) seed oil using phosphoric acid modified mordenite for biodiesel production

    Microsoft Academic Search

    Vasanthakumar SathyaSelvabala; Thiruvengadaravi Kadathur Varathachary; Dinesh Kirupha Selvaraj; Vijayalakshmi Ponnusamy; Sivanesan Subramanian

    2010-01-01

    In this study free fatty acids present in Azadirachta indica (Neem) oil were esterified with our synthesized phosphoric acid modified catalyst. During the esterification, the acid value was reduced from 24.4 to 1.8mg KOH\\/g oil. Synthesized catalyst was characterized by NH3 TPD, XRD, SEM, FTIR and TGA analysis. During phosphoric acid modification hydrophobic character and weak acid sites of the

  19. Cyclic fatty acids from linolenic acid

    Microsoft Academic Search

    R. A. Eisenhauer; R. E. Beal; E. L. Griffin

    1964-01-01

    Linolenic acid of 95% purity was heated with excess alkali in ethylene glycol to produce cyclic fatty acids. Reaction variables,\\u000a which are associated with the cyclization reaction and which were investigated, included solvent-to-fatty-acid ratio, catalyst\\u000a concentration, and reaction temperature, headspace gas (N2 or C2H4), and head-space gas pressure.\\u000a \\u000a Yields of cyclic acids were improved by increasing solvent ratio (1.5–6 wt

  20. Heterogeneous catalytic reduction of perchlorate in water with Re-Pd/C catalysts derived from an oxorhenium(V) molecular precursor.

    PubMed

    Zhang, Yunxia; Hurley, Keith D; Shapley, John R

    2011-02-21

    The molecular Re(V) complex, chlorobis(2-(2'-hydroxyphenyl)-2-oxazoline)-oxorhenium(V), Re(O)(hoz)(2)Cl, has been investigated as a suitable precursor, when combined with activated carbon powder containing 5 wt % Pd, to provide a heterogeneous catalyst for the reduction of aqueous perchlorate by hydrogen. Two general methods for catalyst preparation have been adopted: first, by a standard "incipient wetness" impregnation of the carbon powder with handling under largely aerobic conditions for convenience and, second, by a completely anaerobic procedure maintaining a hydrogen atmosphere during adsorption of the complex in water onto the powder. Both types of catalyst were efficient for the complete reduction of perchlorate to chloride within a few hours at room temperature over a range of initial concentrations (2-200 ppm) under 1 atm of H(2) and acidic conditions (pH 2.7-3.7). The perchlorate reduction profiles displayed pseudo-first-order kinetics, and the rates were insensitive to excess chloride. Complete reduction of perchlorate was observed even at pH 5.9 in a phosphate buffer over the course of two weeks. Under comparable conditions, chlorate reduction proceeded ca. 10 times more quickly than perchlorate reduction. The impregnated catalyst was examined by STEM/EDS, which revealed a wide distribution in Pd nanoparticle sizes and also suggested that the Re complex did not aggregate preferentially on or near the Pd particles. XPS of this material provided evidence for reduced Pd after the reaction, but only a +7 oxidation state was seen for the Re sites both pre- and postreduction. Elemental analyses of the catalyst materials taken pre- and postreduction showed variable amounts of Re loss (0-50%) but relatively unchanged amounts of nitrogen. These results show the need to maintain a reducing atmosphere during the preparation and operation of the catalyst in order to achieve optimum activity and stability. PMID:21226477