Abstract: Dealuminated mordenites with Si/Al ratio of 15～112 have been prepared. The amount of dealumination defects in the zeolites was measured by IR method. Experimental results on the thermal stability and hydrophobicity of the zeolites showed that the majority of the terminal silanol groups formed during dealumination still remains as hydrophilic center. Additional treatment with steam or(NH₄)₂SiF₆ solution,which transforms the hydrophilic surface silanol groups into hydrophobic —Si—O—Si— bonds, markedly increases the hydrophobicity of the dealuminated zeolite.

Key words: mordenite, dealumination, thermal stability, hydrophobicity