Poisoning of a supported molybdenum olefin disproportionation catalyst

Nitric oxide and carbon monoxide have been used to poison a propene disproportionation catalyst prepared from molybdenum hexacarbonyl on silica. Nitric oxide is strongly adsorbed, and an effective poison, but infra-red spectra indicate that adsorption occurs on more than one type of site, so that estimates of the active sites obtained are upper limits only. The nitric oxide poisoning experiments have shown that molybdenum is well dispersed on the silica support. Carbon monoxide is not strongly adsorbed; the slight poisoning effect observed can be accounted for in terms of competition between gas phase carbon monoxide and propene for the active sites.