GB1039937A - Process for producing alkyl aromatic hydrocarbons - Google Patents

Abstract

<PICT:1039937/C4-C5/1> Alkyl aromatic hydrocarbons are prepared by reacting a paraffinic hydrocarbon with a halogen, separately recovering the alkyl halide and hydrogen halide produced, reacting the alkyl halide with an aromatic hydrocarbon in presence of an alkylation catalyst and separately recovering the alkyl aromatic hydrocarbon product and additional hydrogen halide, reacting the hydrogen halide with a free oxygen containing gas, recovering liberated halogen and recycling the latter to further reaction with the paraffinic hydrocarbon. The alkylation catalyst is a Friedel-Crafts metal halide in which the halogen is the same as that reacted with the paraffinic hydrocarbon which contains at least two carbon atoms or may contain at least one tertiary carbon atom. Specified paraffin hydrocarbons have 2 to 10 carbon atoms and include methyl derivative and cycloparaffins. Any halogen may be used, preferably bromine. The aromatic hydrocarbons used include benzene and derivatives thereof having up to 18 carbon atoms in the side chain, naphthalene, alkyl naphthalenes, anthracene, phenanthrene, naphthacene and rubrene. Specified catalysts are aluminium chloride or bromide, zirconium chloride, ferric chloride, zinc chloride, bismuth chloride or boron trifluoride. Halogenation of the paraffin takes place at 0 DEG to 400 DEG C. and alkylation of the aromatic hydrocarbon at 0 DEG to 300 DEG C. at atmospheric to 200 atmospheres pressure. The hydrogen halide product streams may be combined and reacted with free oxygen containing gas at 50 DEG C. to 400 DEG C. in presence of a metal oxide of copper, iron, nickel, cobalt, magnesium and zinc, the latter two may be modified with up to 5% copper, nickel or silver. In a modification, the hydrogen halide is first reacted with the metal oxide and the metal halide formed is subsequently reacted with the oxygen containing gas. As shown in the Figure, paraffin hydrocarbon is supplied through line 1 and is admixed with recycle halogen from zone 13 and additional halogen added from line 17. Halogenation takes place in zone 2, using up to 20 moles hydrocarbon per mole of halogen, any unreacted hydrocarbon being recycled from separator 4 through line 5, hydrogen halide being passed to halogen regeneration zone 13. Alkyl halide is passed via line 6 to alkylation zone 8 wherein reaction takes place preferably in the liquid phase with aromatic hydrocarbon supplied through line 7, the h.l.s.v. of the feed being 0.1 to 20 and the ratio of aromatic hydrocarbon to alkyl halide being up to 20:1. Unreacted aromatic compound is recycled from separation zone 10 to the alkylation zone, alkylated aromatic hydrocarbon is taken off through line 15 and hydrogen halide is passed to zone 13 for conversion to free halogen and recycle to halogenation zone 2. The examples describe (i) the ethylation of benzene using ethyl bromide, (ii) the propylation of benzene using propyl bromide and (iii) the preparation of butyl benzene in presence of a copper-modified magnesium oxide.