GB663566A - Improvements in or relating to the production of organic carboxylic esters of polyhydric alcohols - Google Patents

Abstract

Polyhydric alcohol esters of carboxylic acids are made by heating an agitated suspension of freshly heat-activated aluminium oxide in a liquid or molten mixture of the polyhydric alcohol and carboxylic acid to such a temperature that water appears as a reaction product, distilling off said water as the reaction proceeds until the reaction is complete, and thereafter separating the resulting ester in a liquid condition from the spent aluminium oxide and thermally reactivating the latter for re-use in the process. Alcohols specified are pentaerythritol, polypentaerythritols, mannitol, sorbitol, ethylene glycol and glycerol. Monoor poly-carboxylic acids may be used and the invention has particular reference to esters which can be distilled without decomposition only under high vacua or not at all, e.g. esters with monobasic aliphatic or cyclo-aliphatic saturated or unsaturated acids having more than 10 C atoms, such as fatty acids or esters with phthalic or maleic acid. The catalyst is obtained by heating aluminium hydroxide gel to red heat in an inert atmosphere and is reactivated at 900 DEG C., also in an inert atmosphere. Advantageously the catalyst is used in quantities of 1-5 per cent by weight of reactants. The catalyst may be recovered while the reaction residue is still molten or by solvent extraction of the ester. Solvents specified are chloroform, benzene, alcohol, ligroin or mixtures thereof. In examples, in which the above catalyst is used, (1) stearic acid and glycerol are reacted at 260-280 DEG C., water formed being continuously removed and glyceryl tristearate separated from spent catalyst in the molten state; (2) stearic acid (1 1/2 mols.) and pentaerythritol ( 1/2 mol.) are reacted as in (1), cooled to 150 DEG C. and adipic acid ( 1/4 mol.) added and reaction completed at 260-280 DEG C. to yield bis - tristearoyl - pentaerythrityl adipate; (3) pentaerythritol and glacial acetic acid are reacted at 98-106 DEG C. to yield pentaerythrityl tetra-acetate; and in (4) pentaerythritol (2 mols.), stearic acid (6 mols.) and adipic acid (1 mol.) are heated at 260-280 DEG C. in CO2 to yield bis-tristearoyl-pentaerythrityl adipate.