Selective Hydrogenation of Soybean Oil: XII. Trialkyl Aluminum-Copper 'Stearate Homogeneous Catalysts'

The reaction of copper stearate with triethylaluminurn (TEAL) formed a soluble catalyst that promoted the selective hydrogenation of the linolenyl groups in soybean oil. This homogeneous catalyst was more active than copper-chromite. The activity was enhanced by the addition of silica, alumina or titania. Ethyl alcohol accelerated the hydrogenation when it was added in small amounts and retarded hydrogenation when increased amounts were added. More active and, in some cases, more selective catalysts were formed when TEAL was replaced by trialkylaluminum compounds containing longer chain length in the alkyl groups. Among other organometallies tested, diethylmagnesium and diisobutylaluminum ethoxide formed catalysts with activity comparable to heterogeneous nickel catalysts. The linolenate selectivity of these homogeneous catalysts (KLe/KLo = 2.8-5.2) was less than that obtained with copperchromite (12-14), but greater than that of commercially used nickel catalysts (2). Isomerization, as measured by the percentage of trallS isomers formed, was similar to that of heterogeneous copper catalysts (% tralls/AN =0.6-0.7).