Patent GB-714089-A (GB)
Title: Method of refining esters
IPC: C11B3/00
Filed: 1951-12-10
Abstract: A process for the combined refining and bleaching of crude substantially neutral fatty acid esters of glycerol or polyglycols comprises treating said esters in a single refining vessel with weak alkali, substantially free from water, the alkali being present in an amount at least sufficient to neutralize all of the free fatty acids present, heating and agitating the mixture, adding a small amount of an aqueous hydrogen peroxide solution sufficient to bleach the mixture when it is heated to almost the boiling point of water, again heating and agitating the mixture to cause refining and bleaching allowing the mixture to settle to form two layers and recovering the refined ester.  After separation and recovery of the ester it may be heated to a temperature above the boiling point of water, preferably to about 110 DEG  C., under vacuum to remove any traces of water present.  It is preferred to use sodium carbonate in powder form as the weak alkali and to use hydrogen peroxide in an amount of 0.5 to 2.5 per cent of the weight of the crude ester in the form of a 30 per cent aqueous solution.  In the example a crude mixture of substantially neutral triethylene glycol esters of a mixture of fatty acids, of which capric and caprylic are the principal constituents, are treated with sodium carbonate, heated to about 50 DEG  C. and treated with 30 per cent aqueous hydrogen peroxide.  The mixture is heated to about 90 DEG  C. and the product allowed to settle; the upper layer of refined ester is separated and heated to about 110 DEG C. under vacuum and is then filtered through bleaching earth or activated carbon.  Other fatty esters may be refined such as those from acids obtained from animal or vegetable oils or from synthetic acids.  Specification 713,355, [Group IV (a)], is referred to.ALSO:Crude fatty acid esters of glycerol or polyglycols are refined and bleached by treating them in a single refining vessel with weak alkali, substantially free from water, in sufficient amount to neutralise any acid present, heating and agitating the mixture, adding a relatively small amount of an aqueous hydrogen peroxide solution sufficient to bleach the mixture when it is heated to almost the boiling point of water, again heating and agitating the mixture to cause refining and bleaching, allowing the mixture to settle and separating the refined ester.  After separation and recovery of the ester it may be heated to a temperature above the boiling point of water, preferably to about 110 DEG C., under vacuum to remove any traces of water present.  It is preferred to use sodium carbonate in powder form as the weak alkali and to use hydrogen peroxide in an amount of 0.5 to 2.5 per cent. of the weight of the crude ester, as a 30 per cent. aqueous solution.  In the example a crude mixture of substantially neutral triethylene glycol esters of a mixture of fatty acids, of which capric and caprylic are the principal constituents, is treated with sodium carbonate, heated to about 50 DEG C. and treated with 30 per cent. aqueous hydrogen peroxide, the mixture is heated to about 90 DEG C. and the product allowed to settle; the upper layer of refined ester is separated and heated to about 110 DEG C. under vacuum and is then filtered through bleaching earth or activated carbon.  Fatty esters derived from acids in animal or vegetable oils or from synthetic acids may be similarly refined. Specification 713,355, [Group IV (a)], is referred to.