A process for alkylating aromatics comprises: i) contacting a feed containing alkylatable aromatic, e.g., benzene, under liquid phase alkylating conditions with an alkylating agent, e.g., ethylene, in the presence of an alkylation catalyst comprising a porous crystalline material, e.g., MCM-22, to provide an alkylated aromatic product during which contacting said catalyst becomes at least partially deactivated by sorbing catalyst poisons present in said feed; ii) treating said at least partially deactivated catalyst in situ by contacting with at least one polar compound, e.g., water or acetic acid, having a dipole moment of at least 0.05 Debyes under conditions of temperature and pressure employed in said liquid phase alkylating conditions which are sufficient to at least partially desorb said catalyst poison from said catalyst; and iii) collecting said alkylated aromatic product.