Effect of Steam Treatment on Catalytic Performance of La₂O₃-HZSM-5 for Methylation of Toluene with Methanol

Abstract:

Methylation of toluene with methanol to synthesize p-Xylene was performed in a fixed-bed reactor. HZSM-5 zeolite as a catalyst was prepared by modification with La₂O₃. In addition, effect of steam treatment for La₂O₃-modified HZSM-5 on its catalytic performance was investigated as well. The properties of as-prepared catalysts were characterized by XRD, BET and NH₃-TPD. The results indicate that modification with La₂O₃ can narrow the size of HZSM-5 channel effectively. And more than 90% selectivity of p-Xylene is obtained over HZSM-5 with loading of 24% and 30% La₂O₃. However, above La₂O₃-modified HZSM-5 with high-selectivity exhibit a poor stability for time on-stream of the methylation reaction. Steam treatment of La₂O₃-modified HZSM-5 can improve its stability and shape selectivity, decreasing by-products. These effects can be attributed to distortion & narrowing of HZSM-5 channel and reduction of HZSM-5 strong Bronsted acid sites during steam treatment. As a result, the excellent catalytic performance is obtained over 24.0% La₂O₃-modified HZSM-5 by steam treatment at 773 K for 1.0 h, being 23% conversion of toluene, 93% selectivity of p-Xylene during time on-stream.

• Periodical: Advanced Materials Research (Volume 629)
• Pages: 381-385
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.629.381
• Online since: December 2012
• Authors: Jun Hui Li, Zhong Hua Hu, Ya Nan Wang, Hao Xiang, Zhi Rong Zhu
• Keywords: HZSM-5, La₂O₃ Modificataion, Methanol, Methylation, Steam Treatment, Toluene

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