Patent GB-747903-A (GB)
Title: Separation and purification of complex esters
Inventor: AGIUS PETER JOSEPH VERMONT JAM
IPC: C07C69/34
Filed: 1953-07-03
Abstract: The concentration of complex esters in mixtures containing them in admixture with other materials is varied by feeding the mixture to a column packed with a suitable adsorbent material to cause at least a portion of the complex ester to be selectively adsorbed on to the column of adsorbent material.  The complex esters are defined as esters derived from monohydric alcohols, aliphatic dicarboxylic acids and glycols or polyglycols and have the general formula R1OOC-R2-COO-R3-OOC-R4-COOR5 in which R1 and R5 are residues from the monohydric alcohols, R2 and R5 are the hydrocarbon radicals of the aliphatic dicarboxylic acids and R3 is the radical of the glycol or polyglycol, all the radicals R1 to R5 being saturated and R3 being preferably a polyglycol radical.  Esters of this type are disclosed in Specifications 666,697, 680,438, 683,803 and 687,348.  The other materials which may be present in admixture with the complex esters may be simple esters, diesters or unreacted alcohols, glycols or acids used in their preparation.  Some mineral oil may also be present. Specified adsorbent materials are silica gel, attapulgus clay, fuller's earth, talc, bentonitic clays, silica aerogels, sand, lime, chalk, glass spheres, powdered glass, titanium oxide, zinc oxide, and paper pulp.  When it is merely required to produce from the mixture containing the complex ester one cut less rich and a second cut more rich in the complex ester the mixture may be passed through the column without an additional eluent but it is preferred to use a hydrocarbon eluent such as a paraffinic or aromatic hydrocarbon or petroleum ether.  In a preferred embodiment the mixture containing the complex ester and contaminants is fed to a column packed with a suitable adsorbent material preferably in powdered form, the column washed with a hydrocarbon eluent to wash out the contaminants and the column then washed with a liquid organic solvent which is more polar than the hydrocarbon eluent to wash out the complex ester which is then recovered from its solution, e.g. by simple distillation or flashing.  The liquid organic solvent may be an oxygenated hydrocarbon such as a ketone or an alcohol or it may be pyridine. The hydrocarbon eluent may be blended with the complex ester mixture before the latter is fed to the column or it may be passed into the column subsequently.  Alternatively, a portion of the hydrocarbon eluent may be blended with the mixture and the remainder passed subsequently into the column.  In examples: (1) a complex ester/diester blend is prepared as in Specification 666,697 by first forming a half ester from two mols. of sebacic acid and one mol. of triethylene glycol and then esterifying the half ester with two mols. of 2-ethyl-hexanol to yield a complex ester/simple diester blend which is fed to a column packed with silica gel, the column being then elutriated with several portions of benzene to wash out and recover the diester and then with several portions of acetone to wash out and recover the complex ester; (2) the diester blend prepared as in (1) is further blended with dinonyl sebacate and the mixture is then contaminated with a small amount of mineral oil.  The mixture is then fed to a column packed with silica gel and elutriated with petroleum ether to wash out the mineral oil and a part of the diesters, then with benzene to wash out the remainder of the diesters and finally with acetone to wash out the complex ester.  The complex esters are preferably those useful as synthetic lubricants and are preferably derived from C4 to C24 polyglycols, C1 to C12 monohydric alcohols and C6 to C20 aliphatic dicarboxylic acids.  They may also be derived from polyglycol fractions including a variety of specific polyglycols, blends of two or more dibasic acids and aliphatic alcohol cuts containing several different alcohols.  According to the Provisional Specification dicarboxylic acids having less than six carbon atoms, e.g. down to oxalic acid, may be used in the complex ester preparation.