A. Kalantar Neyestanaki

Catalytic combustion of propane and natural gas over Cu and Pd modified ZSM zeolite catalysts

Abstract Copper-exchanged ZSM-5, ZSM-11 and ZSM-48 as well as Pd-ZSM-5 zeolite catalysts were prepared and tested for their light-off and conversion behaviour in complete oxidation of propane and natural gas. Metal modified ZSM zeolite catalysts were found to be superior to the Pd and Cu/alumina catalysts prepared for comparison. Cu-ZSM-5 (Cu, 1.3 wt.-%) appeared to be the most active of the Cu-containing ZSM catalysts exhibiting combustion efficiencies of 97.6 and 94.8% for propane and natural gas, respectively. The method of introducing Pd into the zeolite was found to affect the catalysts activity strongly. Pd-ZSM-5 catalysts prepared by ion-exchange were more active than when the Pd was introduced into the zeolite during the process of hydrothermal zeolite synthesis. Combustion efficiencies of 100 and 98.1% for propane and natural gas combustion were achieved with Pd-ZSM-5 (Pd, 0.9 wt.-%) prepared by the ion-exchange method. The light-off temperatures were found to increase as: Pd-ZSM-5

Catalytic Combustion of Propane and Natural Gas over Silica-Fibre Supported Catalysts

ABSTRACT Different knitted silica-fibre supported metal oxides (oxides of Co, Ni, Mn, Cr) and various combinations of them, platinum-activated cobalt and nickel oxide catalysts as well as noble metal (Pt, Pd) catalysts were prepared. The catalysts were tested for their activity in propane and natural gas combustion in a continuous flow tube reactor at temperature range of 423-823 K and GHSV of 23900 and 47800 h−1. High combustion efficiencies were obtained by the metal oxides and platinum activated metal oxides. Co3O4 was found to be the most active single metal oxide catalyst in propane combustion. The low temperature activity of metal oxide was strongly improved by use of platinum as an activator. The propane combustion over Pd/SiO2 was found to be structure sensitive under our experimental conditions. The dependence of the rate of propane combustion over noble metal containing catalysts was found to be zero order with respect to oxygen and one with respect to propane. The reaction orders over metal oxi...

Catalyst selection and solvent effects in the enantioselective hydrogenation of 1-phenyl-1,2-propanedione

1-Phenyl-1,2-propanedione was hydrogenated at 5 bar and 25°C over Pt/Al2O3 catalysts in the presence of cinchonidine. The effect of four different solvents, ethyl acetate, toluene, ethanol and dichloromethane in the enantioselective hydrogenation of the dione was tested. The highest enantiomeric excess of (R)-1-hydroxy-1-phenyl-2-propanone, 65%, was obtained in dichloromethane. Also toluene and ethyl acetate gave relatively high enantiomeric excesses. In ethanol, which highly interacts with Pt surface, the enantiomeric excess was only 12%. Two different alumina supports and Pt-precursors were investigated using ethyl acetate as solvent. The highest enantiomeric excesses of (R)-1-hydroxy-1-phenyl-2-propanone were obtained with α-Al2O3 supported Pt catalyst prepared from hydrogen hexachloroplatinate(IV)hydrate presursor. The highest Pt loadings in the catalyst preferred enantiodifferentiation. Higher enantiomeric excesses were obtained by increasing the mean metal particle size of Pt.

Kinetics and modeling of o-xylene hydrogenation over Pt/γ-Al2O3 catalyst

Gas-phase hydrogenation of o-xylene to cis- and trans-dimethylcyclohexane (DMCH) was studied in a differential microreactor at atmospheric pressure and 430–520 K over a Pt/-Al2O3 catalyst. Rapid reversible deactivation of the freshly reduced catalyst prompted reactivation before every kinetic measurement and extrapolation of the steady-state activity to initial activity. Reaction orders were close to zero for o-xylene and ranged from 1.5 (430 K) to 3.0 (520 K) for hydrogen. A rate maximum for the production of the saturated compounds was observed at about 460 K. The results were in line with previously reported results on xylene hydrogenation on Ni/-Al2O3 catalyst.

Immobile silica fibre catalyst in liquid-phase hydrogenation

A new knitted silica fibre catalyst was introduced to liquid-phase hydrogenation of organic compounds. The fibre catalyst combined the advantages of catalyst slurries and large catalyst particles: diffusional limitations are minimized and the catalyst is immobile. Nickel impregnated silica fibres were used in the hydrogenation of citral to citronellal and citronellol. The catalyst performance was competitive with a conventional crushed nickel catalyst.