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Open AccessReview

Incorporating Hierarchy into Conventional Zeolites for Catalytic Biomass Conversions: A Review

1
Department of Chemical and Process Engineering, the University of Canterbury, Christchurch 8041, New Zealand
2
State Key Laboratory of Heavy Oil Processing and the Key Laboratory of Catalysis of CNPC, China University of Petroleum, Beijing 102249, China
3
Department of Chemical and Biological Engineering, College of Engineering, Korea University, Seoul 02841, Korea
*
Author to whom correspondence should be addressed.
Catalysts 2019, 9(2), 127; https://doi.org/10.3390/catal9020127
Received: 14 January 2019 / Revised: 29 January 2019 / Accepted: 30 January 2019 / Published: 31 January 2019
(This article belongs to the Special Issue Understanding the Zeolite Catalysis: Synthesis and Application)
Zeolites are promising catalysts that are widely used in petrochemical, oil, and gas industries due to their unique characteristics, such as ordered microporous networks, good hydrothermal stability, large surface area, tunable acidity, and shape-selectivity. Nevertheless, the sole presence of microporous channels in zeolites inevitably restricts the diffusion of bulky reactants and products into and out of the microporous networks, leading to retarded reaction rates or catalyst deactivation. This problem can be overcome by developing hierarchical zeolites which involve mesoporous and macroporous networks. The meso- and macro-porosities can enhance the mass transport of molecules and simultaneously maintain the intrinsic shape selectivity of zeolite microporosity. Hierarchical zeolites are mainly developed through post-synthesis and pre-synthesis or in situ modification of zeolites. In this review, we evaluated both pre-synthesis and post-synthesis modification strategies with more focus on post-synthesis modification strategies. The role of various synthesis strategies on the intrinsic properties of hierarchical zeolites is discussed. The catalytic performance of hierarchical zeolites in important biomass reactions, such as catalytic pyrolysis of biomass feedstock and upgradation of bio-oil, has been summarized. The utilization of hierarchical zeolites tends to give a higher aromatic yield than conventional zeolites with microporosity solely. View Full-Text
Keywords: hierarchical zeolite; synthesis; micropores; mesopores; deactivation; biomass conversion hierarchical zeolite; synthesis; micropores; mesopores; deactivation; biomass conversion
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Khan, W.; Jia, X.; Wu, Z.; Choi, J.; Yip, A.C. Incorporating Hierarchy into Conventional Zeolites for Catalytic Biomass Conversions: A Review. Catalysts 2019, 9, 127.

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