Acidity and catalytic activity of mesoporous ZSM-5 in comparison with zeolite ZSM-5, Al-MCM-41 and silica–alumina

Autor:	Y. Aoyagi, Katsuki Suzuki, Miki Niwa, Naonobu Katada, Ryong Ryoo, Minkee Choi
Rok vydání:	2008
Předmět:	chemistry.chemical_compound chemistry MCM-41 Inorganic chemistry General Chemistry ZSM-5 Mesoporous material Molecular sieve Zeolite Brønsted–Lowry acid–base theory Catalysis Octane
Zdroj:	Catalysis Today. 132:38-45
ISSN:	0920-5861
Popis:	Acidity of mesoporous HZSM-5 prepared using amphiphilic organosilane template molecules was measured. Bronsted acid sites were observed in the prepared sample, and the number and the strength of Bronsted acid sites were determined quantitatively by a method of infrared-mass spectroscopy/temperature-programmed desorption (IRMS-TPD) of ammonia. ΔH for ammonia adsorption as an index of the strength was ca . 150 kJ mol −1 that was almost the same as on usual HZSM-5, but the number was smaller than that of HZSM-5. From the measured acidity, it was concluded that the mesoporous materials contained a smaller concentration of Bronsted acid site notable on the structure of HZSM-5. Measurements of turnover frequency (TOF) in the catalytic cracking of octane supported the conclusion. Density functional calculations showed that the defect sites Al–OH and Si–OH attached to the Bronsted acid site changed the strength of the acid sites to show some possible structures of the weak and strong Bronsted acid sites included in the mesoporous HZSM-5. Acidities of Al-MCM-41 and silica–alumina were also measured, and the difference in the solid acidities of these materials was discussed.
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_________::7e2e97a019e581a318ac8ee51c3d04bd https://doi.org/10.1016/j.cattod.2007.12.010 Zobrazit plný text záznamu Full Text from ScienceDirect