Home About us Contact
|
Home About us Contact | ||
|
|
||
Platinum Catalysts (platinum + catalyst)
Selected AbstractsChemInform Abstract: Aerobic Oxidation of Hydroquinone Derivatives Catalyzed by Polymer-Incarcerated Platinum Catalyst.CHEMINFORM, Issue 7 2009Hiroyuki Miyamura Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Immobilization of a Platinum Catalyst Using the Polymer Incarcerated (PI) Method and Application to Catalytic Reactions.CHEMINFORM, Issue 32 2005Hiroyuki Hagio Abstract For Abstract see ChemInform Abstract in Full Text. [source] Carbon-Carbon Double Bond versus Carbonyl Group Hydrogenation: Controlling the Intramolecular Selectivity with Polyaniline-Supported Platinum CatalystsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2008Martin Steffan Abstract The use of polyaniline (PANI) as catalyst support for heterogeneous catalysts and their application in chemical catalysis is hitherto rather poorly known. We report the successful synthesis of highly dispersed PANI-supported platinum catalysts (particle sizes between 1.7 and 3.7,nm as revealed by transmission electron microscopy, TEM) choosing two different approaches, namely (i) deposition-precipitation of H2PtCl6 onto polyaniline, suspended in basic medium (DP method) and, (ii) immobilization of a preformed nanoscale platinum colloid on polyaniline (sol-method). The PANI-supported platinum catalysts were applied in the selective hydrogenation of the ,,,-unsaturated aldehyde citral. In order to benchmark their catalytic performance, citral hydrogenation was also carried out by using platinum supported on the classical support materials silica (SiO2), alumina (Al2O3), active carbon and graphite. The relations of the structural characteristics and surface state of the catalysts with respect to their hydrogenation properties have been probed by EXAFS and XPS. It is found that the DP method yields chemically prepared PtO2 on polyaniline and, thus, produces a highly dispersed and immobilized Adams catalyst (in the ,-PtO2 form) which is able to efficiently hydrogenate the conjugated CC bond of citral (selectivity to citronellal=87%), whereas reduction of the CO group occurs with polyaniline-supported platinum (selectivity to geraniol/nerol=78%) prepared via the sol-method. The complete reversal of the selectivity between the preferred hydrogenation of the conjugated CC or CO group is not only particularly useful for the selective hydrogenation of ,,,-unsaturated aldehydes but also unveils the great potential of conducting polymer-supported precious metals in the field of hitherto barely investigated chemical catalysis. [source] ChemInform Abstract: Strontium-Doped Perovskites Rival Platinum Catalysts for Treating NOx in Simulated Diesel Exhaust.CHEMINFORM, Issue 23 2010Chang Hwan Kim Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Selective Synthesis of N-Aryl Hydroxylamines by the Hydrogenation of Nitroaromatics Using Supported Platinum Catalysts.CHEMINFORM, Issue 3 2010Yasumasa Takenaka Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Xphos Ligand and Platinum Catalysts: A Versatile Catalyst for the Synthesis of Functionalized ,-(E)-Vinylsilanes from Terminal Alkynes.CHEMINFORM, Issue 2 2009Abdallah Hamze Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Donor-Stabilized Phosphenium Adducts as New Efficient and Immobilizing Ligands in Palladium-Catalyzed Alkynylation and Platinum-Catalyzed Hydrogenation in Ionic LiquidsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2009Samer Saleh Abstract The straightforward synthesis of a new donor-stabilized phosphenium ligand 3d by addition of bromodifurylphosphine to 1,3-dimethylimidazolium-2-carboxylate 1 is described. The obtained ligand exhibits a very strong ,-acceptor character, comparable to that of triphenyl phosphite [P(OPh)3] or of tris-halogenophosphines, with a ,CO(A1) at 2087,cm,1 for its nickel tricarbonyl complex. This ligand, as well as the related 3a which was obtained from chlorodiphenylphosphine, were tested in palladium-catalyzed aryl alkynylation and in the platinum-catalyzed selective hydrogenation of chloronitrobenzenes, both in an ionic liquid phase. In CC bond cross-coupling we observed that the increase of the ,-acceptor character in ligand 3d, due to the introduction of an additional electron-withdrawing group, provides a very efficient catalyst in the alkynylation reaction of aryl bromides with phenylacetylene, including the deactivated 4-bromoanisole or the sterically hindered 2-bromonaphthalene. The catalytic activity decreases with recycling due to the sensitiveness of ligands to protonation in the ionic phase. Conversely, a multiple recycling of the metal/ligand system in non-acidic media was achieved from platinum-catalyzed hydrogenation of m- chloronitrobenzene. The catalytic results obtained by employing the complex of platinum(II) chloride with 3a [trans -PtCl2(3a)2] in comparison with the non-ionic related trans -tris(triphenylphosphine)platinum dichloride [trans -PtCl2(PPh3)2] complex clearly indicate that the simultaneous existence of a strong ,-acceptor character and a positive charge within the ligand 3a significantly increases the life-time of the platinum catalyst. The selectivity of the reaction is also improved by decreasing the undesirable formation of dehalogenation products. This cationic platinum complex trans -PtCl2(3a)2 is the first example of a highly selective catalyst for hydrogenation of chloronitroarenes immobilized in an ionic liquid phase. The system was recycled six times without noticeable metal leaching in the organic phase, and no loss of activity. [source] Preparation and properties of polyethoxysilsesquioxane-C60 hybridsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2007Takahiro Gunji Abstract Free-standing films of C60 -polyethoxysiloxane hybrids were prepared, and their optical limiting properties were evaluated. Triethoxysilylated C60, with a formula of H3C60[Si(OEt)3]3, was synthesized by the hydrolysilylation of C60 with triethoxysilane in the presence of platinum catalyst. C60 -polyethoxysiloxanes were prepared by a cohydrolytic polycondensation of triethoxysilylated C60 with tetraethoxysilane in a molar ratio of Si/C60 = 10,1000 under nitrogen flow. The molecular weight of C60 -polyethoxysiloxane increased with a decrease of Si/C60. Transparent and flexible free-standing films were prepared by aging an ethanol solution of C60 -polyethoxysiloxane at 80 °C for 6,8 days. The mechanical strength and Young's modulus increased with a decrease in Si/C60. These free-standing films showed an optical limiting property, for which the threshold value decreased from 1163 mJ/cm2 (Si/C60 = 1000) to 130 mJ/cm2 (Si/C60 = 10) with a decrease of Si/C60. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3273,3279, 2007 [source] Reaction Mechanisms for Renewable Hydrogen from Liquid Phase Reforming of Sugar CompoundsASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1-2 2006A. Tanksale Hydrogen is anticipated to become a major source of energy in the future. Hydrogen is a clean burning fuel and has been described as a long-term replacement for natural gas. It has been demonstrated here that hydrogen can be produced from biomass in the temperature range of 185-220°C using a single batch reactor pressurised at 25-30 bar. The current work is based on sugars which are considered here as the biomass resource. Glucose, fructose and sucrose solutions were used for the liquid phase reforming using supported platinum catalyst. The sugar molecules might go through reversible dehydrogenation steps to give adsorbed species on metal sites. This adsorption might be either on CC or CO bond cleavage. Platinum is one of the best catalysts for the reforming of hydrocarbons due to its high selectivity for CC bond cleavage. The CC bond cleavage is the limiting factor for the reforming and leads to a high rate of formation of hydrogen. On the other hand CO bond cleavage results in formation of alcohols, acids and other organic groups. [source] Carbon-Carbon Double Bond versus Carbonyl Group Hydrogenation: Controlling the Intramolecular Selectivity with Polyaniline-Supported Platinum CatalystsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2008Martin Steffan Abstract The use of polyaniline (PANI) as catalyst support for heterogeneous catalysts and their application in chemical catalysis is hitherto rather poorly known. We report the successful synthesis of highly dispersed PANI-supported platinum catalysts (particle sizes between 1.7 and 3.7,nm as revealed by transmission electron microscopy, TEM) choosing two different approaches, namely (i) deposition-precipitation of H2PtCl6 onto polyaniline, suspended in basic medium (DP method) and, (ii) immobilization of a preformed nanoscale platinum colloid on polyaniline (sol-method). The PANI-supported platinum catalysts were applied in the selective hydrogenation of the ,,,-unsaturated aldehyde citral. In order to benchmark their catalytic performance, citral hydrogenation was also carried out by using platinum supported on the classical support materials silica (SiO2), alumina (Al2O3), active carbon and graphite. The relations of the structural characteristics and surface state of the catalysts with respect to their hydrogenation properties have been probed by EXAFS and XPS. It is found that the DP method yields chemically prepared PtO2 on polyaniline and, thus, produces a highly dispersed and immobilized Adams catalyst (in the ,-PtO2 form) which is able to efficiently hydrogenate the conjugated CC bond of citral (selectivity to citronellal=87%), whereas reduction of the CO group occurs with polyaniline-supported platinum (selectivity to geraniol/nerol=78%) prepared via the sol-method. The complete reversal of the selectivity between the preferred hydrogenation of the conjugated CC or CO group is not only particularly useful for the selective hydrogenation of ,,,-unsaturated aldehydes but also unveils the great potential of conducting polymer-supported precious metals in the field of hitherto barely investigated chemical catalysis. [source] Autothermal Catalytic Partial Oxidation of Glycerol to Syngas and to Non-Equilibrium ProductsCHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 1 2009David Abstract Glycerol, a commodity by-product of the biodiesel industry, has value as a fuel feedstock and chemical intermediate. It is also a simple prototype of sugars and carbohydrates. Through catalytic partial oxidation (CPOx), glycerol can be converted into syngas without the addition of process heat. We explored the CPOx of glycerol using a nebulizer to mix droplets with air at room temperature for reactive flash volatilization. Introducing this mixture over a noble-metal catalyst oxidizes the glycerol at temperatures over 600,°C in 30,90,ms. Rhodium catalysts produce equilibrium selectivity to syngas, while platinum catalysts produce mainly autothermal non-equilibrium products. The addition of water to the glycerol increases the selectivity to H2 by the water gas shift reaction and reduces non-equilibrium products. However, water also quenches the reaction, resulting in a maximum in H2 production at a steam/carbon ratio of 2:3 over a Rh-Ce catalyst. Glycerol without water produces a variety of chemicals over Pt, including methylglyoxal, hydroxyacetone, acetone, acrolein, acetaldehyde, and olefins. [source] | ||||||||||