IN-SITU ELECTROCHEMICAL PROMOTION BY SODIUM OF THE SELECTIVE HYDROGENATION OF ACETYLENE OVER PLATINUM

The applicability of electrochemical promotion (EP) has been extended to an investigation of the Pt-catalysed hydrogenation of acetylene to ethylene and ethane, the first example of the use of EP in catalytic s elective hydrogenation. The system exhibits strong promotion by spillo ver Na supplied from a beta ''-alumina solid electrolyte. In the hydro gen-rich regime, reversible, potential-dependent, increases in ethylen e selectivity of an order of magnitude are achievable under the influe nce of similar to 0.02 monolayer Na, while maintaining high acetylene conversion. Thus, EP by Na induces Pt, normally a poor selective hydro genation catalyst, to behave like Pd. Butenes, butadiene, and benzene are observed as minor products whose formation is also promoted by Na. A simple reaction model based on the destabilising effect of charge t ransfer from Na to adsorbed ethylene accounts for the principal findin gs. (C) 1998 Academic Press.