The alkylation of phenol with tert-butyl alcohol was carried out in a continuous flow reactor over a catalyst synthesized from fly ash. The activity of the synthesized catalyst was compared with those of other conventional zeolite catalysts such as 13X (NaX) and H beta. Of all the catalysts tested, zeolite H beta showed the highest activity in phenol conversion followed by the synthesized zeolite (HZOP-31). The activity of commercial 13X zeolite was found to be same as that of HZOP-31. Ce-exchanged catalyst (CeZOP-31) showed even better performance than 13X in the alkylation of phenol. The effects of different parameters such as reactant mole ratio, temperature and space velocity on phenol conversion and tertbutyl phenol selectivity were studied. The effect of mass transfer resistance was found to be negligible within the feed rate range and particle size range studied. The apparent activation energy for the reaction of tert-butyl alcohol over HZOP-31 was determined as 30.1 kJ mol(-1). (c) 2006 Society of Chemical Industry.