Conversion of acetylene to benzene over palladium single-crystal surfaces. 1. The low-pressure stoichiometric and the high-pressure catalytic reactions

TLDR: In this article, the reaction products are benzene from cyclotrimerization, ethylene from hydrogenation, and hydrogen from decomposition on palladium single crystals in ultrahigh vacuum (UHV) and at atmospheric pressures (10/sup -1/-1 atm).

Abstract: Acetylene cyclotrimerizes to form benzene on palladium single crystals in ultrahigh vacuum (UHV) (10/sup -12/-10/sup -8/ atm) and at atmospheric pressures (10/sup -1/-1 atm). The reaction is structure sensitive in both pressure regimes. In UHV the (111) face is the most active followed by the (110) and then the (100) surfaces. At high pressure the (111) and (100) surfaces have equal catalytic activity whereas the (110) face is one-fourth as active. In UHV the reaction products are benzene from cyclotrimerization, ethylene from hydrogenation, and hydrogen from decomposition. At high pressures only benzene was detected. The high-pressure catalytic reaction proceeds on the bare metal surface. The reaction also proceeds readily on Pd films and Pd supported on alumina.