Promote the Xylene Production in Benzene Methylation using Hierarchically Porous ZSM-5 Derived from a Modified Dry-Gel Route

Chinese Journal of Chemical Engineering, Available online 18 June 2014, In Press, Accepted Manuscript
Catalysis, Kinetics and Reaction Engineering
Promote the Xylene Production in Benzene Methylation using Hierarchically Porous ZSM-5 Derived from a Modified Dry-Gel Route
Wei Deng (1), Xuan He (1), Chao Zhang (1), Yunyi Gao (1), Xuedong Zhu (1), Kake Zhu (1),  Qisheng Huo (2), Zhijie Zhou (3)
1) College of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China
2) State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012, China
3) Key Laboratory of Coal Gasification, Ministry of Education, East China University of Science and Technology, Shanghai 200237, China
Abstract
Methylation of benzene is an alternative low-cost route to produce xylenes. Unfortunately selectivity to xylene over conventional zeolitic catalysts remains low. Researchers employed a combined dry-gel-conversion and steam-assisted-crystallization method to synthesize hierarchically porous zeolite ZSM-5 with varied Si/Al ratios. Characterization revealed the method to be applicable to ZSM-5 with Si/Al ratios from 20 to 180.
They used the ZSM-5 zeolites as catalysts for benzene methylation at 460 °C to study the effect of additional porosity and Si/Al ratios. At low Si/Al ratios, the benzene conversions over conventional and hierarchical ZSM-5 are close, and selectivity to toluene is high over hierarchical ZSM-5. They observed that hierarchical porosity significantly enhances effectiveness of zeolite and the selectivity towards xylenes via improved mass transport at higher Si/Al ratios.
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