Aluminium bromide catalysed transalkylations of a Texas lignite coal

Texas lignite coal was treated at a variety of reaction times and temperatures with water-activated AlBr 3 in the presence of either m-xylene or diphenyl ether. Reactions with m-xylene resulted in increases in coal weights, probably due to incorporation of xylene into the coal structure, whereas reactions with diphenyl ether resulted in weight losses in the treated coal. The solubility in pyridine of the coal recovered from these reactions was increased significantly, reaching a maximum of 50% in one reaction with diphenyl ether. Suggestions are made for processes that may explain both the weight increases and the greater pyridine solubility. Support for the occurrence of transalkylation of alkyl groups from lignite to diphenyl ether was provided by g.c.-m.s. analysis of an ether extract in which diphenyl ether molecules substituted with C 1–C 13 alkyl groups could be identified. Also of interest was the observation of the compound phenoxathin among the products of transalkylation.