A computational analysis of a chemical switch mechanism. Catalysis-inhibition effects in a copper surface-catalyzed oxidation

Abstract

A reaction scheme was designed for the tert.-butyl hydroperoxide-initiated autoxidation of hexadecane at 100/sup o/C, which was inhibited by small amounts of copper and accelerated by copper in excess of a critical ratio of initial hydroperoxide concentration to copper surface area. The model consisted of a homogeneous reaction set of 53 steps based on well-known free-radical oxidation, and a surface reaction set of 34 steps based on a proposed competition for trapping of hydroperoxide at inhibition and catalysis surface sites. A computational procedure for numerical solution of the mass-action differential equations by the Gear integration technique was used. The homogeneous mechanism correctly predicted the observed oxidation rates and insensitivity to initial hydroperoxide concentrations in the absence of copper. The surface mechanism, tested with various initial conditions and rate parameters, gave results in agreement with experiment for the following phenomna: location of the switch point of the mechanism, the shape of the reaction curve, and the insensitivity of the rate to the hydroperoxide concentration above the switch point. Graphs, tables, and 15 references.