Manufacture of ethyl benzene

In a process for effecting ethylation of an alkylatable aromatic hydrocarbon compound by contacting said compound with ethylene under conversion conditions of 250 to 600.degree. C., a pressure between about 0.1 and about 100 atmospheres, a feed weight hourly space velocity between about 0.1 and about 100 and a molar feed ratio of said compound to ethylene between about 1 and about 30 in the presence of a crystalline aluminosilicate zeolite having a silica to alumina ratio of at least about 12 and a constraint index within the approximate range of 1 to 12 in a series of beds of said zeolite wherein effluent of each such bed except the last is admixed with fresh reactant supplied at a temperature lower than that of said effluent and the so-quenched reaction mixture is passed to the next such bed;

• the improvement comprises supplying charge to the first said bed and fresh reactants to said effluents as a mixture consisting essentially of said alkylatable aromatic hydrocarbon compound and ethylene admixed with at least an equi-molar amount of inert hydrocarbon diluent consisting essentially of methane, ethane or a mixture of the same whereby to increase the partial pressure driving force to desorb coke precursors from the catalyst surface.