THE PARTIAL OXIDATION OF METHANE ON MOO3/SIO2 CATALYSTS - INFLUENCE OF THE MOLYBDENUM CONTENT AND TYPE OF OXIDANT

The selective oxidation of methane to formaldehyde at atmospheric pressure was studied over a series of silica supported molybdena catalysts. Two silica supports of substantially different surface areas (80 and 200 m2/g) and molybdenum contents ranging from 0 to 3.5 Mo/nm2 were used for this purpose. The catalytic performance of the two catalyst series was compared for a wide range of experimental conditions, including the influence of the oxidant in the feed (O2 or N2O). The main products of the oxidation reaction were formaldehyde, CO and CO2. Small amounts of C2H6 and CH3OH were also identified. For typical reaction conditions, i.e., reaction temperatures 863 K, W/F 4.5 g h/mol and CH4/O2 = 10 M both methane conversion and formaldehyde selectivity were higher with O2 as oxidant. Furthermore, formaldehyde selectivity reached a maximum for molybdenum concentrations ca. 1 Mo/nm2 with both oxidants. The molybdenum exposure on the surface of fresh and spent catalysts was monitored by X-ray photoelectron spectroscopy. © 1993 Academic Press, Inc.