Hydrocarbons such as isobutane and benzenes are alkylated using a solid catalyst in a process which simulates the cocurrent movement of the catalyst bed versus the reactants. This has been found to greatly reduce the rate of catalyst deactivation compared to simulated countercurrent flow. The process may be performed using five or more beds of catalyst, with two undergoing regeneration at any one time. One bed is subjected to a short term liquid-phase regeneration while the other is subjected to long term vapor-phase regeneration. The catalyst preferably contains a metal hydrogenation function effective to selectively hydrogenate C.sub.6 -plus materials trapped on the used catalyst.