THE COBALT-MOLYBDENUM INTERACTION IN COMO/SIO2 CATALYSTS - A COOXIDATION STUDY

The interaction among cobalt, molybdenum and silica in CoMo/SiO2 catalysts has been investigated in a series of catalysts with the same overall composition and varying interaction among the components. XRD and DRIFTS give a rough indication of the phases present, and the formation of CoMoO4 can be easily monitored. The formation of CoMoO4 is observed in most of the catalysts due to the poor interaction between molybdenum oxide and silica. The presence of other minor, non-crystalline phases must be attested by other methods, such as, TPR and catalytic oxidation of carbon monoxide. The presence of ''free'' cobalt can be demonstrated by a low temperature peak in TPR. The catalytic oxidation of CO may function as a useful indicator for the interaction between cobalt and molybdenum, because the oxidation activity of cobalt species incorporated in a molybdate lattice (i.e. CoMoO4) is considerably less than cobalt oxide.