The purpose of this study was to evaluate the catalytic activity and propose a mechanism for the heterogeneous bimolecular catalytic reaction of methane with oxygen on an alumina-supported palladium catalyst. The catalyst (5% w/w Pd on Al2O3) was prepared by Incipient Wetness Method using palladium (II) nitrate hydrate and gamma-aluminum oxide nanopowder in a Vortex mixer, followed by drying in air oven at 110 0C overnight and calcination at 500 0C for 6 hours. The activity of the catalyst was determined by passing a gas mixture (1% CH4, 4% O2, balance He) through a fixed catalytic reactor with a space velocity, 1.7x105(cc/cc).hr.-1 The highest methane conversion over a temperature range of 250-400 0C was 94% at 325 0C. The effects of partial pressures were studied at 280 0C with concentrations of CH4 (1 and 2%) at constant 4 % O2 concentration; similarly concentrations of O2 were changed from 4% to 8% O2 keeping CH4 concentration at 2%. Based on the kinetic data it is proposed that the catalytic oxidation of methane follows a bimolecular Langmuir-Rideal-Eley mechanism with O2 adsorbed on palladium surfaces and CH4 in the gas phase. This proposed mechanism is supported by the experimental rate law [ r=K1 PO2 .PCH4/( 1+K2 PO2) with first order in CH4 and zero order in O2. The X-ray Photoelectron Spectroscopy (XPS) data confirmed the surface contained about 1% of Pd in the form of PdO (38%) and nonstoichiometric palladium oxide [Pdntv, 62%). The activity of the catalyst on the oxidation of methane (1% and 5%) in the presence of air is under investigation and the data will indicate the efficiency of the catalyst in real-world conditions.

Activity and mechanism of methane oxidation over Pd/Al2O3 catalyst

255th National Meeting (2018)

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