KINETIC-STUDIES OF THE OXIDATIVE COUPLING OF METHANE OVER A NAOH/CAO CATALYST

The effects of the partial pressures of oxygen and methane as well as temperature on the rates of C2 hydrocarbon formation, carbon oxide formation, and total methane conversion in the oxidative coupling of methane over a NaOH/CaO catalyst were studied at differential operating conditions in a microcatalytic fixed-bed reactor. Temperature and partial pressures of the reactants were varied within the following ranges: 933 K ≤ T ≤ 1033 K, 5 kPa ≤ PCH° ≤ 80 kPa, 0.3 kPa ≤ PO° ≤ kPa. The rate of COx formation was of 0.5 order in methane as well as in oxygen; the rate of C2 hydrocarbon formation was first order in methane while it passed through a maximum with respect to oxygen partial pressure. The rate of methane conversion was well described by a power-law rate equation. Mechanistic assumptions derived from these kinetic results and corroborated by kinetic isotope effects are presented. In addition, kinetic equations for C2 hydrocarbon formation, carbon oxide formation, and methane conversion as reported in the literature were scrutinized for their applicability to describing the experimental data obtained in this work. © 1992.