A kinetic study of partial oxidation of methane with nitrous oxide on a molybdena-silica catalyst

Abstract

Silica-supported molybdena has been found to catalyze the partial oxidation of methane to methanol and formaldehyde. Nitrous oxide as the oxidizing agent and the presence of water vapor in the reactant gas stream were necessary to carry out this reaction at the temperature range of 480–590 °C and a total pressure of 1 atm. Highest turnover rates of methanol and formaldehyde were, respectively, 2.24 × 10 −4 and 6.25 × 10 −4 molec · s −1 · site −1 at 590 °C. The rate of methanol formation was first order with respect to methane and water, and zero order with respect to nitrous oxide; whereas the rate of formaldehyde formation was zero order with respect to all reactants. From activation energy measurements it was possible to identify a low- and a high-temperature mechanism of formaldehyde formation. Predominant at temperatures below 540 °C were the processes leading to parallel formations of methanol ( E a = 41 kcal/mole) and formaldehyde ( E a = 82 kcal/mole) from the same intermediate, while at higher temperatures only the consecutive oxidation processes leading to formaldehyde via methanol with an overall E a of 40 kcal/mole was the major route.