The electrochemical hydrogenation of edible oils in a solid polymer electrolyte reactor. II. Hydrogenation selectivity studies

Soybean oil has been hydrogenated electrochemically in a solid polymer elec trolyte (SPE) reactor at 60 degrees C and 1 atm pressure. These experiments focused on identifying cathode designs and reactor operation conditions th at improved fatty acid hydrogenation selectivities. Increasing oil mass tra nsfer into and out of the Pd-black cathode catalyst layer (by increasing th e porosity of the cathode carbon paper/cloth backing material, increasing t he oil feed flow rate, and inserting a turbulence promoter into the oil fee d flow channel) decreased the concentrations of stearic acid and linolenic acid in oil products [for example, an iodine value (IV) 98 oil contained 12 .2% C-18:0 and 2.3% C-18:3]. When a second metal (Ni, Cd, Zn, Pb, Cr, Fe, A g, Cu, or Co) was electrodeposited on a Pd-black powder cathode, substantia l increases in the linolenate, linoleate, and oleate selectivities were obs erved. For example, a Pd/Co cathode was used to synthesize an IV 113 soybea n oil with 5.3% stearic acid and 2.3% linolenic acid. The trans isomer cont ent of soybean oil products was in the range of 6-9.5% (corresponding to sp ecific isomerization indices of 0.15-0.40, depending on the product IV) and did not increase significantly for high fatty acid hydrogenation selectivi ty conditions.