A Highly Catalytic Bimetallic System for the Low-Temperature Selective Oxidation of Methane and Lower Alkanes with Dioxygen as the Oxidant

Abstract

This report describes a highly catalytic bimetallic system for the low temperature selective oxidation of methane, ethane, and butane with dioxygen as the oxidant. The catalytic system consists of a mixture of copper chloride and metallic palladium and operates in a 3:1 mixture (v/v) of trifluoroacetic acid and water in the presence of dioxygen and carbon monoxide. Methane was selectively converted to methanol. The dependence of the reaction rate on the partial pressure of methane was measured, and saturation kinetics was observed. The dependence of the rate on the partial pressure of carbon monoxide was measured at two different pressures of methane, and a first-order dependence on the partial pressure of carbon monoxide was observed in both instances. The activation parameters for the overall reaction were obtained under the reaction conditions when the rate was first order in both methane and carbon monoxide. The values obtained were A = 2 × 104 s-1 and Ea = 15.3 kcal mol-1. Both C−H and C−C cleavage products were observed for ethane and n-butane, resulting in the formation of methanol, ethanol, and acetic acid. The rate of formation of methanol from methane with the bimetallic system was ca. 65 × 10-4 M/min at 145−150 °C. This rate may be compared to the rate of formation of acetic acid from methanol in the benchmark Monsanto process: 380 × 10-4 M/min at 180 °C.