GB774855A - Improvements in or relating to the recovery of tocopherols from deodorizer sludges - Google Patents

Abstract

Tocopherol concentrates are prepared by saponifying a vegetable oil deodorizer sludge containing 1 per cent or more of tocopherol, acidifying the resulting saponified composition, separating off the glycerine containing phase from the bottom of the reaction mixture, esterifying the fatty acids in the remaining composition with a lower monohydric alcohol, and thereafter separating from the resulting ester composition a tocopherol concentrate. The sludge may be derived from soya bean oil, or from cottonseed oil, or mixtures thereof. The saponification step may be carried out with an alkali metal hydroxide such as sodium or potassium hydroxide, in an aqueous medium or in a medium comprising a lower monohydric alcohol, preferably one containing between 1 and 4 carbon atoms such as methanol. The saponified sludge may be acidified with p-toluene-sulphonic acid or a mineral acid such as hydrochloric or sulphuric acid. After the separation of the glycerine containing phase, which settles to the bottom of the reaction mixture, the fatty acids in the remaining composition are preferably esterified with a lower monohydric alcohol containing 1 to 4 carbon atoms. The esterification is preferably effected in the presence of a catalyst such as a mineral acid-particularly hydrochloric acid in a quantity comprising 1 to 2 per cent by weight of the reaction mixture. A preferred method of operation is to use sulphuric acid to neutralize the saponified sludge and to catalyse the esterification with hydrochloric acid. The tocopherol concentrate, which at this stage is composed essentially of free tocopherols, lower monohydric alcohol esters of fatty acids and free sterols, may be separated from the ester composition by distillation, solvent extraction, crystallization, selective adsorption, or combinations thereof. The fatty acid esters are preferably removed by distillation prior to the separation of the tocopherol concentrate from the sterol fraction. The sterols are preferably separated by wintering and filtering off the relatively insoluble sterols, crystallization of the sterols being promoted by the addition of a small amount of a lower monohydric alcohol, and the resulting filtrate which usually contains tocopherols and fatty acid esters of lower monohydric alcohols may be subjected to vacuum distillation, thereby distilling off the esters followed by a tocopherol concentrate. Another method of separating a tocopherol concentrate is by distilling the crude reaction mixture to strip off the low-boiling esters, distilling off a fraction comprising essentially tocopherol and sterols, and leaching out a tocopherol concentrate with a solvent, e.g. acetone, acetonitrile, methyl ethyl ketone or isopropyl ether. The sludge treatment may be modified in that it is first enriched in alpha-tocopherol content, or the resulting tocopherol concentrate may be treated to increase the alpha-tocopherol content, e.g. methylation can be carried out by halomethylation and reduction, or by hydroxymethylation and reduction. The process is applicable to a sludge derived from soya bean oil to increase the tocopherol content from more than about 5 per cent by weight to more than about 20 per cent by weight -the tocopherol fraction in a soya bean oil sludge usually comprises 10 per cent alpha-tocopherol, 60 per cent gamma-tocopherol and 30 per cent delta-tocopherol. A number of detailed examples are given in which the sludge is derived from soya bean oil. Specification 548,731, [Group IV], is referred to.