AN INITIAL STRATEGY FOR THE DESIGN OF IMPROVED CATALYSTS FOR METHANE PARTIAL OXIDATION

The catalytic partial oxidation of methane to methanol has proved to be an extremely demanding reaction. It is clearly important that methanol should be stable over any potential catalysts, so a systematic study has been undertaken to determine the types of oxides over which methanol might have the required stability. The results should be valuable for the design of future catalysts. Methanol stability by catalytic oxidation has been investigated in the temperature range 150-500 degrees C and 1 atm pressure. Over the majority of materials a substantial proportion of methanol was converted to carbon oxides below 350 degrees C. Several oxides exhibited improved performance, these were MoO3, Nb2O5, Ta2O5 and WO3. Methanol conversion over these materials was high, but the major products were formaldehyde and dimethyl ether. Sb2O3 showed the best performance, producing a methanol conversion of only 3% at 500 degrees C. The results have been compared with both physical and chemical properties of the oxides in an attempt to establish trends. In particular we have looked at relationships with oxygen exchange data. A weak but significant correlation between methanol decomposition to carbon oxides and the rate of oxygen exchange is discussed.