Zeolite ZSM-5, for catalyzing shape-selective disproportionation of ethylbenzene (EB) to produce para-diethylbenzene (p-DEB), was modified by chemical liquid deposition of silica (SiO2-CLD), chemical vapor deposition of silica (SiO2-CVD), loading MgO and SiO2-CLD and loading MgO. The results show that ZSM-5 modified by SiO2-CLD (SiO2-CLD/ZSM-5) has better catalytic performance than ZSM-5 modified by SiO2-CVD (SiO2-CVD/ZSM-5) due to passivation of partial acidic sites in channels Of SiO2-CVD/ZSM-5. When SiO2-CLD/ZSM-5 is further modified by a loading of 0.50 wt% MgO to ZSM-5, it decreases both in acidic amount and in acidic strength, and its catalytic activity decreases slightly. But, the residual acidic sites on the external surface Of SiO2-CLD/ZSM-5 are well eliminated. As a result, MgO modification improves paradiethylbenzene selectivity (p-DEB to DEB) up to 98.6% with appreciable EB conversion of 28.1%, and it greatly reduces the side reaction of EB dealkylation. Besides, ZSM-5 modified by SiO2-CLD and MgO (SiO2-CLD and MgO/ZSM-5) shows a good stability due to proper modification of its acidity and structure. (c) 2005 Elsevier B.V. All rights reserved.