Transalkylation of toluene with C<SUB>9</SUB> aromatic hydrocarbons over ZSM5 zeolites

The transalkylation reactions of a mixture of toluene and C9+ aromatics were studied over HZSM5 catalysts of varying SiO2:Al2O3 ratios (30-800) as well as over a NiHZSM5 catalyst. As the SiO2: Al2O3 ratio is increased, the rate of transalkylation is decreased. Among the C9 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&gt;1.2.3&gt;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 H2: hydrocarbon ratio are also presented. It was observed that the transalkylation of C9 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