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The direct alkylation of toluene with ethane to the isomeric ethyltoluenes and hydrogen using a bifunctional Pd/H-ZSM-5 catalyst was carried out in a fixed-bed, flow-type reactor. The effect of pressure was investigated between 1 and 100 bar and at moderate temperatures of 300 and 350 °C. From stoichiometry, no influence of pressure is expected for ideal gases. However, thermodynamic equilibrium calculations for a network of reactions, taking into account nonideal gas behaVior, do predict an influence of pressure. Toluene conversions of 5-8% observed experimentally at 300 °C over the entire pressure range are in line with these calculations. In contrast, the toluene conversion observed at 350 °C and 50 bar is at 27% well above the equilibrium value calculated using a limited reaction network. It is proposed that the formation of hydrogen-rich light alkanes is favored at high pressures, creating a hydrogen sink. Hence, the equilibrium is shifted toward the formation of ethyltoluenes. The maximum experimental yield of ethyltoluenes achieved so far is approximately 14 wt %.

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