Alteration in Surface Reaction Selectivity of Nitriles. 2. CH3CN on W(100) and W(100)-(5x1)-C2

Article abstract of DOI:10.1021/j100409a025

The adsorption and reaction of acetonitrile has been investigated on clean W(100) and W(100)-(5x1)-C surfaces, using thermal desorption spectroscopy and isotopic labeling.Irreversible decomposition of acetonitrile dominates on clean W(100) producing gaseous N2, H2, and adsorbed carbon.At high acetonitrile exposures some molecular CH3CN desorption is observed at 190 deg K as well as C-C bond activation and hydrogenation which results in CH4 and HCN formation.The activation energy for irreversible decomposition of CH3CN and the reaction selectivity are dramatically different on the -(5x1)-C surface, a model for the basal plane of WC(0001).In this case, the thermal desorption spectrum of the parent CH3CN consists of five poorly resolved features with acetonitrile desorption observed up to 600 deg K.The acetonitrile peaks above 400 deg K on this surface are attributed to rehydrogenation of adsorbed CH2CN.Molecular hydrogen, nitrogen, and hydrogen cyanide were the only additional reaction products detected.No methane formation was observed, indicating that C-C bond activation is less facile on the -(5x1)-C vs. the clean W(100).The production of HCN is attributed to intramolecular hydrogen atom transfer of surface bound HCCN.