The alkylation of toluene with 1-dodecene was carried out over a HFAU zeolite (total and framework Si/Al ratio = 25) under the following conditions: fixed-bed reactor, 90 degrees C, molar toluene/dodecene ratio of 3, WHSV = 10 h(-1). Monododecyltoluenes are selectively formed, bidodecyltoluenes appearing only in low amounts at a complete conversion of dodecene. Tridodecyltoluenes are also formed inside the supercages but cannot desorb from the zeolite. These compounds, mainly located in the outer part of the crystallites are responsible for catalyst deactivation. However, tridodecyltoluenes can be completely removed by treatment under toluene flow, which allows a complete regeneration of the catalyst. This removal occurs by transalkylation between tridodecyltoluenes and toluene molecules with a final formation of monododecyltoluenes. At least, the first transalkylation steps occur between toluene in the liquid phase and tridodecyltoluenes in the zeolite pores (pore mouth catalysis).