Selective Hydrogenation of Soybean Oil on Copper Catalysts as a Tool Towards Improved Bioproducts

The liq.-phase soybean oil hydrogenation was studied on silica-supported Cu and ternary Cu-Zn-Al catalysts. Cu/SiO2 samples were prepd. by incipient-wetness impregnation (Cu/SiO2-Imp) and chemisorption-hydrolysis (Cu/SiO2-CH), while two Cu-Zn-Al mixed oxides contg. 8 (Cu(8)-Zn-Al) and 15 % Cu (Cu(15)-Zn-Al), resp., were prepd. by copptn. Copper dispersion (D Cu) was 23 % on Cu/SiO2-CH, and this sample showed a high activity for soybean oil hydrogenation; in contrast, Cu/SiO2-Imp was inactive, probably because Cu was poorly dispersed (D Cu = 2 %). The oil hydrogenation activity on Cu(15)-Zn-Al (D Cu = 9 %) was lower than on Cu/SiO2-CH, while Cu(8)-Zn-Al (D Cu = 23 %) was inactive. Citral hydrogenation used as a test reaction showed that the intrinsic Cu0 activity was not significantly changed by the kind of support or the catalyst prepn. method. These latter results suggested that the obsd. differences in soybean oil hydrogenation may be explained as changes in accessibility of the triglyceride mols. to Cu active sites. In ternary Cu-Zn-Al samples, access to catalytic sites was hampered by the narrower pore structure of the catalyst. Copper exhibited unique properties for obtaining proper lubricants from soybean oil hydrogenation because selectively hydrogenated unsatd. linolenic (C18:3) and linoleic (C18:2) fatty acids to unsatd. oleic acid (C18:1) without forming satd. stearic acid (C18:0).