Transalkylation of toluene with C₉ aromatic hydrocarbons over ZSM5 zeolites

Abstract

Abstract The transalkylation reactions of a mixture of toluene and C 9 + aromatics were studied over HZSM5 catalysts of varying SiO 2 :Al 2 O 3 ratios (30–800) as well as over a NiHZSM5 catalyst. As the SiO 2 : Al 2 O 3 ratio is increased, the rate of transalkylation is decreased. Among the C 9 aromatics that were present in the feed, the ethyl toluenes were extensively de‐ethylated to toluene. The shape‐selective characteristics of the ZSM5 zeolite were revealed through the relative order of reactivity of the three trimethyl benzene isomers 1.2.4>1.2.3>1.3.5. The stable life of the catalyst can be prolonged by the incorporation of nickel. The influences of process parameters such as temperature, pressure, space velocity and H 2 : hydrocarbon ratio are also presented. It was observed that the transalkylation of C 9 aromatics with toluene to yield xylenes occurs mainly on the external surface of the ZSM5 crystals. The disproportionation of toluene to yield benzene and xylene, however, takes place predominantly in the pore system.