Direct crystallization of B-, Al- and Ga-substituted medium-pore ITH zeolites was carried out using hexamethonium hydroxide (HMH) and N,N,N',N',-tetramethyl-1,6-hexanediamine (TMHDA) as structure-directing agents. The type of organic SDA was found determining the crystal size and the nature of Bronsted acid sites in isomorphously substituted ITH zeolites. The use of HMH resulted in formation of tiny (length of 0.5-3 mu m) needle-like ITH crystals having bridging Si-(OH+)-E(-)(E= B, Al, Ga) groups with acidic strength increasing in the following sequence B < Ga

Keywords:Germanosilicate zeolites;ITH;Isomorphous substitutibn;Acidity;Tetrahydropyranylation of alcohols