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Indexed by:期刊论文

Date of Publication:2006-09-08

Journal:MICROPOROUS AND MESOPOROUS MATERIALS

Included Journals:SCIE、EI、Scopus

Volume:94

Issue:1-3

Page Number:325-329

ISSN No.:1387-1811

Key Words:acid strength; acid sites; modified Hammett indicator; NH3-TPD; useful acid sites; nanoscale HZSM-5

Abstract:The acid strength distribution of different samples such as HZSM-5, modified HZSM-5, TS-1 and SiO2 was investigated by modified Hammett indicator and ammonia temperature programmed desorption (NH3-TPD). It has been shown that only acid sites with H-0 <= +2.27 contribute to the conversion of toluene in toluene disproportionation, which is only small percent in the total acid amount. The acid sites with strength +4.8 <= H-0 <= +6.8 may be ascribed to the acid sites that were produced by silanol group in HZSM-5. In study of HZSM-5 and modified HZSM-5 by NH3-TPD, the lower temperature peak (LT) and higher temperature peak (HT) are ascribed to the acid sites with strength -3.0 < H-0 <= +2.27 and H-0 <= -3.0, respectively. The two kinds of acid sites origin from framework Al in certain circumstances and one (H-0 <= -3.0) is easy to block and the other one (-3.0 < H-0 <= +2.27) is the body of acid sites, which is significant to fully understand the acid sites of nanoscale HZSM-5. (c) 2006 Elsevier Inc. All rights reserved.