期刊
JOURNAL OF CATALYSIS
卷 283, 期 2, 页码 168-177出版社
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.jcat.2011.08.007
关键词
Core/shell zeolite composite; MCM-22; Borosilicate; Disproportionation of toluene; Shape-selective catalysis; para-Xylene
资金
- NSFC of China [20890124, 20925310, 20873043]
- Science and Technology Commission of Shanghai Municipality [09XD1401500]
- Shanghai Leading Academic Discipline Project [B409]
A shape-selective core/shell-structured Al-MWW@B-MWW composite catalyst has been hydrothermally synthesized through isomorphically overgrowing borosilicate on premade MCM-22 aluminosilicate. The secondary growth of borosilicate enlarged obviously the thickness of the platelet crystallites of MCM-22 and increased the surface Si/Al ratio from 16 to 222. The Fourier transform infrared (FTIR) spectra of adsorbed 2,6-di-tert-butylpyridine indicated that the Bronsted acid sites located on the external surface were virtually covered completely by the generated B-MWW layer, whereas those acid sites within channels were still accessible and detectable by using pyridine or ammonia as probing molecules. When applied to the disproportionation of toluene on a fixed-bed reactor, the Al-MWW@B-MWW composite catalysts exhibited significantly enhanced para-xylene selectivity in comparison with normal MCM-22 and its physical mixture with B-MWW. Al-MWW@B-MVVW's unique catalytic behaviors were ascribed to an effective suppression of para-xylene isomerization as a result of removal of non-shape-selective acid sites on the external surface. (C) 2011 Elsevier Inc. All rights reserved.
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