Temperature-programmed surface reaction of butadiene on molybdenum nitride catalyst

The surface species from butadiene adsorption on γ-Mo₂N were studied by temperature-programmed surface reaction (TPSR). The C₄ hydrocarbons desorbed at 60°C can be attributed to the complex formed between butadiene and Mo sites. They were reversibly adsorbed on the catalysts and can be easily removed through hydrogenation at adsorption temperature. The C₄ hydrocarbons desorbed at 120°C may be butylidyne. The species desorbed at 320°C are irreversibly adsorbed on the catalyst and are difficult to be removed through hydrogenation at adsorption temperature; these species are associated with the deactivation of the catalyst. Oligomers involved in the TPSR vary their desorption temperature between 120°-360°C with conditions of butadiene adsorption and the catalysts. The products of TPSR on the passivated Mo₂N, compared with the fresh catalyst, showed a larger amount of products formed from the cracking and polymerization. Two models of active sites were proposed to explain the difference of TPSR between the fresh and the passivated Mo₂N.