Effect of Si/Al Ratios on the Structure and Catalytic Properties of Alkaline-Treated ZSM-5 Catalysts

Abstract:

A series of hierarchical HZSM-5 catalysts were synthesized by alkaline (denoted as HZSM-5-At) and/or alkaline-acid (denoted as HZSM-5-At-acid) treatments, and they as catalyst pairs were employed for the synthesis of glycerol and ammonia toward pyridine bases in a series-connected two-stage reactor. The characterization was analysed by means of N₂-physorption and NH₃-TPD techniques. The catalytic evaluation showed that the lower Si/Al ratio (Si/Al = 25 before treatment) in catalyst pairs (HZSM-5-At + ZnO/HZSM-5-At-acid) possessed the highest total yield of pyridine bases among all the catalyst pairs, but the suitable Si/Al ratio in alkaline-treated ZSM-5 (Si/Al = 38 before treatment) in the first stage of reactor and ZnO/HZSM-5-At-acid (Si/Al = 25 before treatment) in the second stage of reactor had the stronger stability relative to other catalyst pairs. The characterization revealed that the amount of acid sites play a vital role in the formation of pyridine bases whereas the appearance of mesoporous structure and the declined concentration of acid sites were main reasons for promoting the stability.

• Periodical: Materials Science Forum (Volume 896)
• Pages: 141-147
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.896.141
• Online since: March 2017
• Authors: Cai Wu Luo*, Xiang Yang Li, Zi Sheng Chao
• Keywords: Alkaline, Catalyst, Mesoporous, Si/Al, ZSM-5

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