Disproportionation of 1,2,4-trimethylbenzene over montmorillonite pillared by aluminium oxide

Abstract

Disproportionation of 1,2,4-trimethylbenzene was investigated in a flow system at 200°C, using montmorillonite intercalated by aluminium chlorohydroxyl complex (Al-mont) as a catalyst. Calcination of the Al-mont at 4000C gave an interlayer spacing of 8.5 A. The Al-mont catalyst was selective for disproportionation to yield 1,2,4, 5-tetramethylbenzene (durene) and xylenes. o-Xylene was produced far more abundantly than expected from thermodynamical equilibrium. A mechanistic consideration suggested that the preferential formation of 1,2,4,5-tetramethylbenzene and o-xylene was a result of restricted transition state selectivity. The catalytic activity decreased with time on stream owing to coke deposition. The catalyst deactivation was, however, prevented by supporting a small amount of Pd on the catalyst and using H 2 as a carrier gas, probably as a result of hydrogen spill-over.