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
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.