Zeolite synthesis in the SiO2–Al2O3–Na2O–pyridine–H2O system

The crystallisation of zeolites from the SiO2–Al2O3–Na2O–pyridine–H2O system has been investigated. Three zeolitic phases were isolated : mordenite, ferrierite and ZSM-5. Only the ferrierite phase is specifically directed by the pyridine molecules. Depending upton the composition of the reaction mixture, mordenite or ZSM-5 can be synthesised in the absence of the organic additive. The ferrierite phase is formed over a wide range of gel compositions although the yield and purity of the sample is dependent upon the aluminium content of the gel. The ferrierite phases formed are relatively siliceous and are all within the composition range SiO2/ Al2O3= 25–38. Ca. 2–3 pyridine molecules are occluded per unit cell within the ferrierite channels.