TEXTURE, ELECTRON-ACCEPTOR, ACID-BASE, AND CATALYTIC PROPERTIES OF MODIFIED ZSM-5 ZEOLITE .1. HYDROPHOBY OF THE STARTING ZEOLITES AND EFFECT OF MODIFICATION OF THE OUTER SURFACE WITH TETRAETHOXYSILANE

The texture and hydrophobic properties of ZSM-5 zeolites with (SiO2/Al 2O3) ratios of 32, 40, 48, 55, 66, and 840 were investigated both in t he starting H form and after modification of the outer surface with te traethoxysilane. The x-ray diffraction data and analysis of the C6H6 a dsorption isotherms showed that the synthesized zeolites have 70-80% c rystallinity and contain no other phases. The amount of adsorbed H2O i n samples annealed at 500-degrees-C decreased linearly with an increas e in the ratio and was 5-6 molecules of H2O per Al atom, and the maxim um amount was 23 molecules of H2O/unit cell. A similar linear function also persisted for samples annealed at 800-degrees-C, but the number of acid OH groups adsorbing H2O decreased by two times in this case. I t was shown that modification of the outer surface with tetraethoxysil ane did not affect the amount of adsorbed H2O.