Comparison of the protonic acidity of HY, LZY-82, HSAPO-37, and HEMT: Effect of the structure and of the nature of T atoms

• Published in: Zeolites 1993-11, Vol.13 (8), p.626-633
• Main Authors: Su, Bao Lian, Barthomeuf, Denise
• Format: Article
• Language: English
• Subjects: benzene adsorption; Chemistry; Exact sciences and technology; General and physical chemistry; HEMT; HSAPO-37; infrared; Ion-exchange; LZY-82; protonic acidity; Surface physical chemistry; thermal stability; Zeolites: preparations and properties
• ISSN: 0144-2449; 1873-3115
• DOI: 10.1016/0144-2449(93)90134-O

Four different zeolites built from sodalite cages and hexagonal prisms are compared using infrared spectroscopy with regards to their hydroxyl properties and to their interaction with benzene. Among the three materials that have the faujasite structure (HY, LZY-82. and HSAPO-37), HSAPO-37 is the most stable with regards to hydroxyls and texture. The presence of P also facilitates the generation of very strong acid sites for pretreatments above around 1000 K. The different arrangement of building units in HEMT involves a mean stronger acidity than in zeolites with the faujasite structure. The overall order of thermal stability (hydroxyls and texture) is HY < HEMT < LZY-82 < HSAPO-37. The interaction of benzene with the hydroxyls of the two infrared bands (HF and LF) is total in HSAPO-37. Because of lack of space, not enough benzene can enter the cages of HY to titrate all the protons and a part of the LF band is unaffected. There is space enough in HEMT; nevertheless, a fraction of the LF hydroxyls is trapped in the sodalite cage and is not attracted in the large cages. The integrated intensity l of the CH out of plane vibration of benzene adsorbed is similar for all the materials.