Catalysis over molybdenum carbides and nitrides. II. Studies of CO hydrogenation and C/sub 2/H/sub 6/ hydrogenolysis

The hydrogenation of CO and the hydrogenolysis of C/sub 2/H/sub 6/ were studied over the hcp and fcc phases of Mo/sub 2/C, and the fcc phase of Mo/sub 2/N. The CO hydrogenation activity and selectivity of the fcc phases of Mo/sub 2/C and Mo/sub 2/N are identical. The activity of the hcp phase of Mo/sub 2/C is half that of the other two catalysts but the olefin selectivity is higher. Elemental analysis reveals that the catalysts contain a substantial amount of oxygen following extended use for CO hydrogenation. The hydrogenolysis activity of both Mo/sub 2/C phases increases markedly with decreasing content of oxygen in the catalyst. Consistent with the known structure sensitivity of C/sub 2/H/sub 6/ hydrogenolysis, the activity of the hcp phase of Mo/sub 2/C is 200-fold higher than that of the fcc phase. This difference in activity is attributed to differences in the structure of the principal planes exposed by each phase of the carbide. 32 references.