Electrocatalytic hydrogenation of diethyl fumarate. A simple system development.

Diethyl fumarate was chosen as a model in search for better conditions to a chieve selective electrocatalytic hydrogenation. In addition to carbon felt , several catalytic cathode surfaces have been examined, including Fe, Pt, Ni, Pb, Al, Co, Zn, and stainless steel. Other variables like current densi ty (58 to 285 mA.dm(-2)), supporting electrolyte (NaCl, KBr, NaBr, NaI, NaF ), solution pH* (3.0 to 9.0) and co-solvent (CH3CN, t-BuOH, MeOH and THF) w ere tried. The majority of the reactions were carried out at constant curre nt in an undivided cell fitted with the chosen working electrode and DSA((R )) (RuO2/TiO2) as the auxiliary electrode, in H2O/co-solvent (4:1). The bes t results for hydrogenation (84 % chemical yield) were obtained using Fe as cathode, a current density of 175 mA.dm(-2), in H2O/CH3CN (4:1) at pH* 5.5 . NaBr and KBr are also useful electrolytes for hydrogenation. pH* variatio n does not seem to affect product ratio. THF as co-solvent and NaF as suppo rting electrolyte should be avoided, as well as carbon felt and Ni as elect rodes. (C) 1999 Elsevier Science Ltd. All rights reserved.