期刊
APPLIED CATALYSIS A-GENERAL
卷 447, 期 -, 页码 115-123出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.apcata.2012.09.012
关键词
Pyrolysis; Biomass; Biofuel; Zeolite; Shape selectivity
资金
- National Special Program of Water Pollution Control and Management [2012ZX07301-005]
- State Key Joint Laboratory of Environment Simulation and Pollution Control [11Y03ESPCT]
- Science and Technology Planning Project of Zhejiang Province [2012C21055]
Catalytic fast pyrolysis (CFP) of lignin with four different zeolite catalysts was investigated to determine the role of shape selectivity of zeolites in CFP. These zeolites included ZSM-5, mordenite, beta, and Y zeolites, which have various crystallographically determined static pore sizes between 5.6 and 7.6 angstrom. The molecular dimensions of pyrolysis products, including lignin-derived oxygenates and aromatics, were calculated using quantum chemical computations. The effective pore sizes of the four zeolites at 650 degrees C were then determined by analyzing the molecular size and conversion behavior of the pyrolysis products in CFP. Results suggest that thermal distortion of the zeolite pore structure under high-temperature conditions of CFP effectively enlarge the crystallographically determined pore sizes of the zeolites by 2.5-3.4 angstrom Therefore, many lignin-derived oxygenates with a molecular size considerably larger than the static pore size were able to enter the pores of the zeolites and become effectively converted in our CFP tests. Bulkier monolignols derived from syringyl lignin, however, could not be effectively converted by ZSM-5 and mordenite zeolites due to size exclusion or pore blockage. Among the four zeolites, ZSM-5 produced the highest aromatic yield, followed in order by beta, mordenite, and Y zeolites. Beta and Y zeolites were the most effective catalysts for deoxygenating lignin-derived oxygenates. This analysis indicates that for CFP of softwood, ZSM-5 is the optimal catalyst because it can achieve satisfactory deoxygenation and aromatic production simultaneously, whereas for hardwood feedstock, beta zeolite may be used to convert bulky oxygenates derived from syringyl lignin. (C) 2012 Elsevier B.V. All rights reserved.
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