Conversion of ethanol to hydrocarbons on hierarchical HZSM-5 zeolites
•Synthesis and characterization of the nano-size hierarchical mesoporous HZSM-5.•Catalytic activity comparison of hierarchical HZSM-5 and conventional HZSM-5.•The hierarchical HZSM-5 with mesoporosity demonstrated improved catalyst life-time.•Mesoporosity facilitated the migration of coke to the external surface.
This study reports synthesis, characterization, and catalytic activity of the nano-size hierarchical HZSM-5 zeolite with high mesoporosity produced via a solvent evaporation procedure. Further, this study compares hierarchical zeolites with conventional HZSM-5 zeolite with similar Si/Al ratios for the ethanol-to-hydrocarbon conversion process. The catalytic performance of the hierarchical and conventional zeolites was evaluated using a fixed-bed reactor at 360 °C, 300 psig, and a weight hourly space velocity of 7.9 h−1. For the low Si/Al ratio zeolite (∼40), the catalytic life-time for the hierarchical HZSM-5 was approximately 2 times greater than the conventional HZSM-5 despite its coking amount deposited 1.6 times higher than conventional HZSM-5. For the high Si/Al ratio zeolite (∼140), the catalytic life-time for the hierarchical zeolite was approximately 5 times greater than the conventional zeolite and the amount of coking deposited was 2.1 times higher. Correlation was observed between catalyst life time, porosity, and the crystal size of the zeolite. The nano-size hierarchical HZSM-5 zeolites containing mesoporosity demonstrated improved catalyst life-time compared to the conventional catalyst due to faster removal of products, shorter diffusion path length, and the migration of the coke deposits to the external surface from the pore structure.
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Journal: Catalysis Today - Volume 238, December 2014, Pages 103–110