Mechanism of carbon monoxide and hydrocarbon oxidation on copper chromite

Abstract

Infrared spectroscopic, gravimetric, and kinetic techniques have been used to study the oxidation of CO and hydrocarbons on a copper chromite catalyst. Carbon monoxide adsorbs concurrently on exposed lattice copper atoms to form CuCO and on lattice oxygen atoms to form ▪ groups. The source of the oxygen required to form the unidentate carbonate groups is the catalyst, not the gas phase. In the absence of air, the carbonyl group reacts with oxygen from the catalyst to produce CO 2. In the presence of air, the oxidation reaction via the carbonyl group becomes important at temperatures above 80 °C and that via the decomposition of the carbonate groups above 200 °C. When hydrocarbons adsorb above 130 °C they are transformed to unidentate carbonate groups and liberate water vapor. As with CO, above 200 °C these carbonate groups decompose to give gaseous CO 2. For the carbonyl decomposition path, the reaction is first order in CO, and pseudo-zero order in O 2. The amount of CO 2 produced by the oxidation reaction does not inhibit the rate.