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Isomerization of ethylbenzene in the gaseous phase over bifunctional Pt/AI^a nd Pt-zeolite catalysts was investigated in a microcatalytic fixed bed reactor using the pulse method. Over the Pt/Al203 catalyst, where the carrier displays only weak acidity, xylenes are formed from ethylbenzene mainly via the route ethylbenzene-ethylcyclohexene-1,2-methylethylcyclopentene-1,2-dimethylcyclohexene-o-xylene, which corresponds to predictions from a bifunctional mechanism in which skeletal rearrangements of tertiary carbocations only are considered to be the rate-determining steps. Over Pt-zeolite catalysts with higher acidity, skeletal isomerizations in which secondary carbocations are involved contribute-in addition to the route mentioned above-to the measured product distributions.

The kinetics of isomerization of C8‐aromatics on a bifunctional Pt/zeolite catalyst has been studied at 422°C, total pressures of 7.102 KPa to 18.102 KPa and H2/hydrocarbon ratios of 3 to 18 in a fixed bed reactor. The rate of ethyl‐benzene isomerization can be described on the basis of a bifunctional reaction mechanism. For modeling the rates of interconversion of the C8‐aromatics linear rate laws are suitable as long as hydrogen and hydrocarbon partial pressures are kept constant.

According to Constantinides and Arich (1964), most V can be removed by precipitation of asphaltenes. This suggests that V content increases relative to Ni in the direction of heavy asphaltene fractions. This is supported by a number Literature Cited

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