Partial hydrogenation of 1, 3-butadiene on Pt electrode in aqueous alkaline solutions

Abstract

Hydrogenation of 1,3-butadine (1,3-C″ 4) was studied on Pt in aqueous alkaline solutions at open circuit and potentiostatic conditions. The highly selective partial hydrogenation to butenes was achieved ( ca. 90%) with the increase of P H (hydrogen pressure) at pH = 12.6 or with the increase of Ph beyond 12.6 at a constant P H. At these conditions, the butenes are confirmed not to be hydrogenated. These results are explained by the absence of the adsorbability of the butenes. The reaction rate at the open circuit hydrogenation is controlled by the mass transfer of either 1,3-C″ 4 or H 2. 1,3-C″ 4 undergoes an irreversible, molecular adsorption. H/D exchange during the hydrogenation reveals the predominant, successive additions of the hydrogen atoms. In addition, nmr spectra show the exclusive 1,2 and 1,4 additions in 1- and trans-2-butene formations. The above results are compared with those obtained in 0.5 M H 2SO 4 and the reaction mechanism is discussed.