Ethylation of benzene with ethanol in the vapour phase was studied over AlPO4-5, MAPO-5, ZAPO-5 and MnAPO-5. The products were ethylbenzene (EB), 1,4-diethylbenzene (PDEB), 1,3-diethylbenzene (MDEB) and polyalkyl benzenes (1,2,4- and 1,3,5-triethylbenzene, and 1,2,4,5-tetraethylbenzene). MnAPO-5 was found to be more active than the other catalysts. Maximum conversion (47%) was noted at 400degreesC over MnAPO-5. Although isomorphic substitution in MnAPO-5 is nearly the same as in MAPO-5 and ZAPO-5, the increment in conversion was attributed to the presence of unpaired electrons in the d-subshell of manganese. The selectivity of the products was found to decrease with stream but the selectivity to EB showed an increase after 2 h of stream. MnAPO-5 registered nearly 14% yield of EB and 17% yield of DEB, whereas the yield of other products was found to be 16% at maximum conversion. (C) 2003 Elsevier B.V. All rights reserved.