Synthesis of pillared MCM-36 zeolites with tetramethylammonium silicate as pillaring reagent

Pillared MCM-36 zeolites of MWW type were hydrothermally synthesized by pillaring swollen layered MCM-22P precursor, with tetramethylammonium silicate as the pillaring reagent; the synthesized zeolites were characterized by different physico-chemical techniques such as XRD, N₂ adsorption, TEM, ²⁷Al-MAS, NMR and NH₃-TPD. The results showed that the swollen MCM-22P without drying was successfully pillared in an aqueous solution system; the MCM-36 zeolites with an uniform interlayer distance were then readily obtained. The suitable synthesis conditions for MCM-36 are 80℃ for 24 h for the interlayer swelling of MCM-22P at high pH value (13.5), and then at 100℃ for 24 h for the formation of the intercalating pillars. The MCM-36 zeolites obtained exhibit a typical MWW topology structure, with a composite pore system of both micropores in the crystalline layers and mesopores in the interlayer space, and a large specific surface area (especially external specific surface area). Compared with HMCM-22, the HMCM-36 zeolites show lower acid amount; however, a larger amount of structurally accessible Brnsted acid sites located in the interlayer space of MCM-36 zeolites are exposed due to the formation of mesopores in the interlayer space, which should be favorable to the reaction involving bulky molecules.