Cubic and hexagonal faujasites with varying Si/Al ratios I. Synthesis and characterization Original Research Article

Zeolite faujasite type with hexagonal structure (EMT) and zeolite faujasite types with cubic structure (FAU) were synthesized with crown ethers as templating agents. The Si/Al ratio of the assynthesized samples was determined to 3.7. The samples were dealuminated by steaming at 773, 873 and 1073 K, respectively. A part of the dealuminated samples was treated with diluted acid to extract the non-framework aluminum. Nature and concentration of the acid centres were estimated by IR spectroscopy and TPDA measurements. From N2 isotherms follows that the extracted samples undergo a partial damage of the structure. It seems that the EMT samples are more stable in the process of steaming and extraction with diluted acid.