Desilication of SSZ-33 zeolite – Post-synthesis modification of textural and acidic properties

Desilication conditions (concentration of NaOH, duration of the treatment) of SSZ-33 zeolite (CON topology) were investigated in respect to the textural and acidic properties of the obtained materials. As-synthesized borosilicate SSZ-33 was transformed by isomorphous substitution to Al-form. The alkaline treatment of Al-SSZ-33 zeolite resulted in the formation of mesopores and enhanced accessibility of Bronsted acid sites. The increase in the mesopore volume and also changes in the concentration of acid sites depends mainly on the concentration (pH) of the treatment. Simultaneously, the increase in the pH of the alkaline solution led to the slight increase in Bronsted acid sites and substantial decrease in the micropore volume more than 50%, in comparison with the parent material while the volume of mesopores increased significantly. All desilicated SSZ-33 zeolites are characterized by a broad mesopore-size distribution in the range of 5–20 nm with the maximum depending both on the harshness and duration of the treatment. The average size of mesopores increases with increasing pH of NaOH solution.