Selective hydrogenation process of linoleic acid present in conjunction with the oils which contain highly unsaturated fatty acids.

摘要

Oils, containing linoleic acid in addition to more highly unsaturated fatty acids are hydrogenated at 150 DEG to 225 DEG C in presence of a copper hydrogenation catalyst as defined below until the content of the more highly unsaturated fatty acids has been reduced while retaining at least 40% of the original content of linoleic acid, the hydrogenated oil being subsequently freed from traces of copper. The oil may be pretreated, e.g. deslimed, deoderized, given an alkaline treatment to reduce the free fatty acid content to below 0.8% or bleached, using activated fuller's earth. The term "copper hydrogenation catalyst" defines catalysts which catalyse the hydrogenation of olefinic bonds in glyceride oils, in which the only active material, as distinguished from any material present which by itself is incapable of catalysing the hydrogenation, is composed substantially of elementary copper and/or a copper oxide, hydroxide or salt. Catalyst carriers may be used, e.g. charcoal, diatomaceous earth, activated clay, aluminium oxide, silica gel, chromium oxide, asbestos, iron oxide, titanium dioxide and manganese oxide and specified catalysts which may be pretreated with hydrogen before use are Cu/kieselguhr; Cu/MgO; Cu/Cr2O3/BaO; Cu/Al2O3 and Cu/MgO/SiO2 and free copper. The amount of catalyst used may be 0.05 to 2.0% by weight of copper based on the weight of oil, e.g. rapeseed oil, mustard oil, rubberseed oil, wheat germ oil and soyabean oil, and pressures of 1 to 200 atmospheres, preferably 5 to 10, may be used. The product is freed from catalyst by filtration in the absence of air and/or at a temperature not greater than 100 DEG C., and is then washed with aqueous acid solution (k = 10-3) to reduce the copper content to below 0.1 p.p.m. The oils treated preferably contain no more than 0.04% by weight of moisture and hydrogenation is continued until the content of the more highly unsaturated fatty acids is reduced by 5 to 25% of the original content while retaining 80 to 60% of the original linoleic acid. The product materials may be used to prepare salad oils and margarines.ALSO:Hydrogenation catalysts comprise elementary copper and/or copper oxide, hydroxide or salt, and an inactive carrier e.g. charcoal, diatomaceous earth, activated clay, aluminium oxide, silica gel, chromium oxide, asbestos, iron oxide, titanium dioxide and manganese oxide. Specified catalysts are Cu/Kieselguhr; Cu/MgO; Cu/Cr2O3/BaO; Cu/Al2O3 and Cu/MgO/SiO2 and free copper. They may be treated with hydrogen before use e.g. at 200 DEG C. The catalysts may be prepared by (1) thermal decomposition in the absence of free oxygen and without sintering of copper salts of carboxylic acids e.g. formate or oscalute, to produce free copper; (2) precipitating copper compounds from aqueous solutions by alkaline reagents with or without co-precipitation of compounds which may form a support and then drying the precipitate; (3) impregnating a suitable support e.g. diatonaceous earth, silica gel or charcoal, with a copper salt solution and drying the impregnated material; (4) Renting a dry mixture of copper compound and carrier; (5) treating an alloy of copper with a more electropositive metal e.g. Al, Mg, Zn, Cd or Fe to dissolve out the metal and leave the copper in porous form. Alkali is used to dissolve out Al or Zn and acid for Mg, Fe, Cd or Zn. A preferred catalyst is prepared by co-precipitating ammonium chromate and a copper salt as ammonium copper chromate, the precipitate being converted by heating into copper chromite and/or a mixture of oxides of copper and chromium. Barium chromate may be present in the precipitate.