GB806239A - Purification of polyalkylphenols - Google Patents

Abstract

The invention comprises a process for the separation of phenols substituted in at least both 2 and 6-positions by an alkyl group, from mixtures of them with other phenols, by heating the mixture with a trialkyl borate, the trialkyl borate reacting with phenols other than those substituted in the 2 and 6-positions, to produce phenol borate esters, and separating the diortho alkyl substituted phenols from these esters by conventional methods. The trialkyl borate used should be such that the physical properties of the borate esters of phenolic impurities, formed during the process of the invention, are sufficiently different from that of the desired phenol, as to allow easy separation. Suitable trialkyl borates are trimethyl borate, triethyl borate, tripropyl borate, tri-isobutyl borate, tri-normal butyl borate, and tri-(2-ethyl hexyl) borate. The reaction is preferably carried out at temperatures above the melting-point of the mixture of phenols, e.g. about 70-175 DEG C., preferably about 150 DEG C., for about one hour, and it is preferable to use an excess of the trialkyl borate required to react with the active phenol. Examples are given of the separation of 2,6-ditertiary butyl-4-methyl phenol from (1) butyl-4-methyl phenol; (2) tertiary-butyl-3-methyl phenol; (3) 4-octyl phenol, using triisobutyl borate and (2-ethyl hexyl) borate. The process of the invention may be carried out, e.g., in one step or in two separate stages, in the first of which the phenols and borate are reacted, and in the second, the fractional distillation of the reaction products is effected. The phenols which have reacted with the trialkyl borates may be recovered by hydrolysis and purified for instance by steam distillation or any other suitable method.