GB655715A - Process for the production of aromatic compounds - Google Patents

Abstract

Addition compounds (i.e. products of physical association of molecules, which easily revert to their original constituents, as distinct from compounds formed by chemical reaction, in which the identities of the reactants are lost), are produced from lower alkyl phenols (i.e. phenols containing a relatively low number of alkyl groups), by treating a lower alkyl phenol, present in a mixture containing other components from which it can only be separated with difficulty by normal methods, with an auxiliary alkyl phenol (containing a different number of alkyl groups, and preferably containing no alkyl group of more than six carbon atoms), causing or permitting the lower alkyl phenol and the auxiliary alkyl phenol to form an addition compound, and separating the latter from the reaction mixture. Preferably, the auxiliary alkyl phenol, the quantity thereof and the reaction conditions are so chosen that the addition compound is formed as a solid while the other components of the reaction mixture remain liquid. The addition products are in some cases useful per se, or they may be decomposed into their constituents and these then separated. Higher alkyl phenols (i.e. phenols containing a higher number of alkyl groups than the initial lower alkyl phenols), are obtained by alkylating the addition product or the lower alkyl phenol separated therefrom. In the former case the auxiliary alkyl phenol is preferably chosen to be identical with the higher alkyl phenol so that the alkylation product consists solely of the latter, part of which may be recycled to form an addition compound with a further quantity of the lower alkyl phenol. Thus in a preferred embodiment of the invention, which is illustrated by examples, 2 : 4-dimethyl-6-tert.-butylphenol is added to a mixture of xylenols, and its addition compound with 2 : 4-xylenol is separated and treated with a butylating agent (e.g. isobutylene) to form substantially pure 2 : 4-dimethyl-6-tert.-butylphenol. Alternatively, an addition compound of 2 : 4-xylenol and m-cresol is produced by adding 2 : 4-xylenol to a mixture of cresols or m-cresol to a mixture of xylenols, and may be butylated to give a mixture of 2 : 4-dimethyl-6-tert.-butylphenol and 2 : 4 - di - tert. - butyl - 5-methylphenol, which compounds are easily separable. The process is stated to be applicable also to the treatment of the ethyl, propyl, butyl amyl and hexyl homologues of the specified methyl and polymethyl phenols. Suitable apparatus is described with the aid of a flow sheet. The Specification as open to inspection under Sect. 91 comprises in general a process for producing derivatives of aromatic compounds from multi-component systems containing the aromatic compound whose derivative is desired, which comprises mixing said multi-component system with an additament capable of forming an addition compound with said aromatic compound, separating the resulting addition compound and treating it to form the desired derivative. Additional compounds stated to be capable of being separated in this way are xylenes, dimethylnaphthalenes, picolines and especially compounds containing polar groups such as -NH2, -CN or -COOH, e.g. toluidines; xylidines; naphthylamines and alkylated naphthylamines; benzonitrile and alkylated benzonitriles, such as 2 : 4-dimethyl-benzonitrile or its ethyl, propyl, butyl, amyl or hexyl homologues; benzoic acid and alkylated benzoic acids, such as 2 : 4-dimethylbenzoic acid. Other substances specified as additaments are urea, oxalic acid and cineole, the combination of the last-named compound with two molecular proportions of 2 : 4-xylenol being described in a further example. This subject-matter does not appear in the Specification as accepted.