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Indexed by:期刊论文

Date of Publication:2012-11-01

Journal:MICROPOROUS AND MESOPOROUS MATERIALS

Included Journals:SCIE、EI、Scopus

Volume:162

Page Number:168-174

ISSN No.:1387-1811

Key Words:Zeolite beta; Mesoporosity; Post-synthesis treatment; NaOH solution; alpha-Pinene isomerization

Abstract:Small crystal zeolite beta with Si/Al ratio of 12 was subjected to post-synthesis treatment with NaOH solutions. The effect of alkaline concentration on the crystallinity, pore structures, compositions and acidic properties of zeolite beta was studied by XRD, N-2 sorption, XRF, and FTIR techniques. The catalytic performance of zeolite beta before and after alkaline treatment was investigated in terms of liquid phase isomerization of alpha-pinene. No distinct change in the crystallinity was observed after the zeolite was treated by 0.1-0.4 M NaOH solutions. However, mesoporosity was evidently developed; the mesopore surface area up to 349 m(2) g(-1) was obtained when 0.4 M NaOH solution was employed. The acidic properties of zeolite beta were mostly preserved when it was treated by 0.1-0.2 M NaOH solutions, but the amount of strong Bronsted acid sites was to some extent reduced when 0.4 and 0.7 M NaOH solutions were employed. The catalytic activities of the samples increase with the development of mesoporosity. The best catalytic performance at 70 degrees C and 30 min reaction time was observed on zeolite beta containing the largest mesopore volume of 0.69 cm(3) g(-1): 100% conversion of alpha-pinene with 85.4% selectivity into camphene, terpinolene, alpha- and gamma-terpinene as desired products. At the same conditions only 20.3% conversion was obtained over parent zeolite beta containing only 0.23 cm(3) g(-1) mesopore volume. This result indicates that the enhanced catalytic activity for alpha-pinene isomerization is mainly attributed to the mesopore formation resulting from alkaline treatment. (C) 2012 Elsevier Inc. All rights reserved.