GB766876A - Process for the manufacture of benzene and of alkyl benzenes - Google Patents

Abstract

Benzene and its alkyl derivatives are obtained by a process comprising the conversion of straight chain olefins of formula CnH2n, in which n may be 2 to 6, either singly or in admixture, by the process of Specification 713,081 or of Specification 742,642, into higher olefines having at least 6 carbon atoms in a straight chain and the subsequent aromatization of the higher olefins so obtained by dehydrogenation and cyclisation in known manner. For example, butene-1 and butene-2 may be dimerized by heating at 180-250 DEG C. in the presence of an alkylaminium compound or a similar organo-metallic compound according to the process of Specification 742,642, to yield mainly 2-ethylhexene-1 which on cyclization gives a mixture of o-xylene, p-xylene and ethyl benzene. Similarly a mixture of 3-methylbutene-1 and propylene yields a mixture of p-xylene and o-xylene. In the examples: (a) butene-1 is mixed with triethylaluminium and heated under pressure to give butene dimer which is heated in the presence of a chromic oxide catalyst to give p-xylene, o-xylene and ethyl benzene; (b) a mixture of 3-methylbutene-1 and propylene is treated as in (a) to give a mixture of p-xylene and o-xylene; (c) a mixture of butene-1 and propylene is treated as in (a) to give toluene and the same products from the aromatization of the butene dimer as in (a); (d) ethylene is heated with triethylaluminium to give butene, hexene and octene which on aromatization give p-xylene, o-xylene, ethylbenzene and benzene; and (e) a mixture of propylene and pentene-1 is heated with tripropylaluminium to give among other products a co-dimer of propylene and n-pentene which on aromatization gives m-xylene.