COMPARISON OF THE PROTONIC ACIDITY OF HY, LZY-82, HSAPO-37, AND HEMT - EFFECT OF THE STRUCTURE AND OF THE NATURE OF T-ATOMS

Citation
Bl. Su et D. Barthomeuf, COMPARISON OF THE PROTONIC ACIDITY OF HY, LZY-82, HSAPO-37, AND HEMT - EFFECT OF THE STRUCTURE AND OF THE NATURE OF T-ATOMS, Zeolites, 13(8), 1993, pp. 626-633
Citations number
32
Categorie Soggetti
Chemistry Physical
Journal title
ISSN journal
01442449
Volume
13
Issue
8
Year of publication
1993
Pages
626 - 633
Database
ISI
SICI code
0144-2449(1993)13:8<626:COTPAO>2.0.ZU;2-0
Abstract
Four different zeolites built from sodalite cages and hexagonal prisms are compared using infrared spectroscopy with regards to their hydrox yl properties and to their interaction with benzene. Among the th ree materia Is 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 ze olites with the faujasite structure. The overall order of thermal stab ility (hydroxyls and texture) is HY < HEMT < LZY-82 < HSAPO-37. The in teraction 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 ben zene can enter the cages of HY to titrate all the protons and a part o f the LF band is unaffected. There is space enough in HEMT; neverthele ss, a fraction of the LF hydroxyls is trapped in the sodalite cage and is not attracted in the large cages. The integrated intensity \ of th e CH out of plane vibration of benzene adsorbed is similar for all the materials.