The Experts below are selected from a list of 294 Experts worldwide ranked by ideXlab platform
Saim Özkar - One of the best experts on this subject based on the ideXlab platform.
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Hydrogen generation from the dehydrogenation of ammonia–borane in the presence of ruthenium(III) acetylacetonate forming a Homogeneous Catalyst
International Journal of Hydrogen Energy, 2013Co-Authors: Sibel Duman, Saim ÖzkarAbstract:Abstract Starting with ruthenium(III) acetylacetonate a Homogeneous Catalyst is formed which catalyzes the release of 1 equivalent of hydrogen gas from the dehydrogenation of ammonia–borane in toluene solution at low temperature in the range 50–65 °C. Mercury poisoning experiments showed that the catalytic dehydrogenation of ammonia–borane starting with ruthenium(III) acetylacetonate is a Homogeneous catalysis. The final product obtained after the catalytic dehydrogenation of ammonia borane was thoroughly characterized by using 11 B Nuclear Magnetic Resonance and Infrared spectroscopies. The Homogeneous Catalyst formed from the reduction of ruthenium(III) acetylacetonate provides 950 turnovers (TTO) over 58 h and 27 (mol H 2 )(mol Ru) −1 (h) −1 value of initial turnover frequency (TOF) in hydrogen generation from the dehydrogenation of ammonia–borane at 60 °C before deactivation. Kinetics of this homogenous catalytic dehydrogenation of ammonia–borane was studied depending on the Catalyst concentration, substrate concentration, and temperature. The hydrogen generation was found to be first order with respect to both the substrate concentration and Catalyst concentration. The activation parameters of this reaction were also determined from the evaluation of the kinetic data: activation energy; E a = 48 ± 2 kJ mol −1 , the enthalpy of activation; Δ H # = 45 ± 2 kJ mol −1 and the entropy of activation Δ S # = −152 ± 5 J mol −1 K −1 .
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Ruthenium(III) acetylacetonate: A Homogeneous Catalyst in the hydrolysis of sodium borohydride
Journal of Molecular Catalysis A-chemical, 2008Co-Authors: Ezgi Keçeli, Saim ÖzkarAbstract:Abstract Ruthenium(III) acetylacetonate was employed for the first time as Homogeneous Catalyst in the hydrolysis of sodium borohydride. Ruthenium(III) acetylacetonate was not reduced by sodium borohydride under the experimental conditions and remains unchanged after the catalysis. Poisoning experiments with mercury and trimethylphosphite provide compelling evidence for the fact that ruthenium(III) acetylacetonate is indeed a homogenous Catalyst in the hydrolysis of sodium borohydride. Kinetics of the ruthenium(III) acetylacetonate catalyzed hydrolysis of sodium borohydride was studied depending on the Catalyst concentration, substrate concentration, and temperature. The hydrogen generation was found to be first order with respect to both the substrate concentration and Catalyst concentration. The activation parameters of this reaction were also determined from the evaluation of the kinetic data: activation energy; E a = 58.2 ± 2.6 kJ mol −1 , the enthalpy of activation; Δ H # = 55.7 ± 2.5 kJ mol −1 and the entropy of activation Δ S # = 118 ± 5 J mol −1 K −1 . Ruthenium(III) acetylacetonate was found to be highly active Catalyst providing 1200 turnovers over 180 min in hydrogen generation from the hydrolysis of sodium borohydride before deactivation.
Ezgi Keçeli - One of the best experts on this subject based on the ideXlab platform.
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Ruthenium(III) acetylacetonate: A Homogeneous Catalyst in the hydrolysis of sodium borohydride
Journal of Molecular Catalysis A-chemical, 2008Co-Authors: Ezgi Keçeli, Saim ÖzkarAbstract:Abstract Ruthenium(III) acetylacetonate was employed for the first time as Homogeneous Catalyst in the hydrolysis of sodium borohydride. Ruthenium(III) acetylacetonate was not reduced by sodium borohydride under the experimental conditions and remains unchanged after the catalysis. Poisoning experiments with mercury and trimethylphosphite provide compelling evidence for the fact that ruthenium(III) acetylacetonate is indeed a homogenous Catalyst in the hydrolysis of sodium borohydride. Kinetics of the ruthenium(III) acetylacetonate catalyzed hydrolysis of sodium borohydride was studied depending on the Catalyst concentration, substrate concentration, and temperature. The hydrogen generation was found to be first order with respect to both the substrate concentration and Catalyst concentration. The activation parameters of this reaction were also determined from the evaluation of the kinetic data: activation energy; E a = 58.2 ± 2.6 kJ mol −1 , the enthalpy of activation; Δ H # = 55.7 ± 2.5 kJ mol −1 and the entropy of activation Δ S # = 118 ± 5 J mol −1 K −1 . Ruthenium(III) acetylacetonate was found to be highly active Catalyst providing 1200 turnovers over 180 min in hydrogen generation from the hydrolysis of sodium borohydride before deactivation.
Andreas J. Vorholt - One of the best experts on this subject based on the ideXlab platform.
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toward water based recycling techniques methodologies for Homogeneous Catalyst recycling in liquid liquid multiphase media and their implementation in continuous processes
Industrial & Engineering Chemistry Research, 2019Co-Authors: Thorsten Rosler, Andreas J. Vorholt, Thiemo A Fasbach, Marco Schrimpf, Walter LeitnerAbstract:Biphasic water-based solvent systems offer the opportunity of efficient recycling of Homogeneous Catalysts. Water separates well from most organic solvents; therefore, water-soluble Catalysts can be immobilized in this phase. Furthermore, water can substitute hazardous and environmentally unfriendly organic solvents in these systems. Within industry only the Ruhrchemie/Rhone-Poulenc process uses plain water to immobilize the Homogeneous Catalyst for the hydroformylation of propene. Yet for more hydrophobic substrates, no water-based system has been commercialized. This review will summarize recent developments in the field of water-based recycling strategies. Topics in this field are the intensification of the mixing process, the use of thermomorphic solvent systems, and the employment of several additives, like alcohols and surfactants. Continuously operated processes for these recycling strategies will be presented and discussed.
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Recyclable Homogeneous Catalyst for the hydroesterification of methyl oleate in thermomorphic solvent systems
Chemical Engineering Science, 2013Co-Authors: Arno Behr, Andreas J. Vorholt, N. RentmeisterAbstract:In the development of commodity markets alternatives to fossil resources are of high interest. One alternative is the usage of oleo compounds. In this paper an atom economic hydroesterification of methyl oleate to linear and branched diesters is described. The selectivity to linear or branched products can be influenced by reaction parameters. These diesters can be used in polymers, plasticizers, lubricants or to adjust crystallinity in these materials. To the best of our knowledge we provide the first efficient Catalyst recycling in the hydroesterification of fatty compounds. The Catalyst system of palladium and XANTphos proved to be very stable. Products with the tough palladium XANTphos Catalyst are mostly branched, while the selectivity to linear products can be influenced by temperature, carbon monoxide pressure and choice of solvent up to 64%. A high selectivity of 94% towards branched products was obtained if no solvent was used. Separation of products and Catalyst was realised using thermomorphic solvent systems (TMS). The Catalyst was recycled in a methanol/decane system with low leaching values. A recycling of the Catalyst phase was conducted three times with no significant activity loss.
Liangnian He - One of the best experts on this subject based on the ideXlab platform.
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guanidinium salt functionalized peg an effective and recyclable homo geneous Catalyst for the synthesis of cyclic carbonates from co2 and epoxides under solvent free conditions
Synlett, 2007Co-Authors: Jinquan Wang, Ya Du, Er Wang, Liangnian HeAbstract:A guanidinium bromide covalently bound to CO 2 -philic polyethylene glycol (PEG) is proved to be a highly effective Homogeneous Catalyst for the eco-friendly synthesis of cyclic carbonates from carbon dioxide and epoxides under mild conditions, which requires no additional organic solvents or co-Catalyst. Notably, it has been found that there is a pronouncedly cooperative effect between the Catalyst part and the support part. Moreover, the Catalyst is able to be reused with retention of high catalytic activity and selectivity. This process looks promising as a strategy for Homogeneous Catalyst recycling.
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new procedure for recycling Homogeneous Catalyst propylene carbonate synthesis under supercritical co2 conditions
Green Chemistry, 2003Co-Authors: Liangnian He, Hiroyuki Yasuda, Toshiyasu SakakuraAbstract:Polyfluoroalkyl phosphonium iodides, Rf3RPI (Rf = C4F9C2H4, C6F13C2H4, C8F17C2H4; R = Me, Rf), catalyzed propylene carbonate synthesis from propylene oxide and carbon dioxide under supercritical CO2 conditions, where propylene carbonate was spontaneously separated out of the supercritical CO2 phase. The Rf3RPI Catalyst could be recycled with maintaining a high CO2 pressure and temperature by separating the propylene carbonate from the bottom of the reactor followed by supplying propylene oxide and CO2 to the upper supercritical CO2 phase in which the Rf3RPI remained.
Philip G. Jessop - One of the best experts on this subject based on the ideXlab platform.
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Recycling of a Homogeneous Catalyst using switchable water
Catalysis Science & Technology, 2012Co-Authors: Sean M. Mercer, Tobias Robert, Daniel V. Dixon, Philip G. JessopAbstract:Aqueous/organic biphasic catalysis allows easy separation of a Homogeneous Catalyst from product, but is often inefficient when hydrophobic substrates are used. A system based on switchable water is monophasic in the absence of CO2 and biphasic in its presence. Catalysis can be performed in the monophasic solvent, and then switched to a biphasic system, separating Catalyst from product. Removal of CO2 allows for easy recycling of the Catalyst. Hydroformylations have been achieved using this solvent system. The Catalyst was recycled several times with minimal loss of activity.