Brønsted acid sites [12]. Nevertheless, toluene dispropor-tionation and transalkylation to benzene and xylenes and toluene hydro-dealkylation to benzene and methane could take place on strong acid sites at high temperatures. Com-pared to toluene, methanol is relatively reactive on zeolitic catalysts and forms dimethylether and water at low temper-atures and can be converted to gaseous hydrocarbons at high temperatures [11,13]. Therefore, the alkylation perfor-mance of zeolites depends on the amount, type and strength of acid sites. Since the activity of zeolites for acid-catalyzed reactions is directly related to the number of framework aluminum atoms, hydrothermal treatment is usually employed to prepare partially dealuminated zeolites to adjust the acidity and improve their selectivity and stabil-ity [4,14,15]. In this study, hydrothermally treated nano-scale ZSM-5 shows some special properties in alkylation of toluene with methanol, and alkylation of ethylbenzene with ethanol is taken as comparative reaction to display the different acid type and strength demanded in different alkylation processes.