Hydrogenation of Fatty Acid Esters. II. Kinetics of Hydrogenation of Methyl (Z)- and (E)-9-Octadecenoate Catalyzed by a Ziegler Nickel Catalyst

Abstract

Kinetics of the title reactions has been studied, using nickel(II) 2,4-pentanedionate/triethylaluminium system as a model catalyst. Initial rate measurements showed that in both cases the hydrogenation is first order in hydrogen, zero order in the octadecanoate and a fractional order (close to one) in the catalyst. Both hydrogenations have similar activation energies (30.2 ± 2.3 kJ mol-1 and 28.9 ± 2.6 kJ mol-1 for the (Z)- and (E)-9-octadecenoate, respectively). Based on these data and the results of competition experiments, two models have been proposed to describe isomerization of the octadecenoates (either direct or via an intermediate).