HZSM-5 zeolites undergoing the high-temperature process for boosting the bimolecular reaction in n-heptane catalytic cracking

• Published in: Chinese journal of chemical engineering Vol. 66; pp. 136 - 144
• Main Authors: Song, Chenggong, Ma, Zhenzhou, Hou, Xu, Zhou, Hao, Qiao, Huimin, Tian, Changchang, Yin, Li, Jin, Baitang, Yuan, Enxian
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.02.2024
• Subjects: Catalytic cracking; Extra-framework Al; High-temperature treatment; HZSM-5; n-Heptane; High-temperature treatment; HZSM-5; n-Heptane; Catalytic cracking; Extra-framework Al
• ISSN: 1004-9541; 2210-321X
• DOI: 10.1016/j.cjche.2023.10.004

High-temperature treatment is key to the preparation of zeolite catalysts. Herein, the effects of high-temperature treatment on the property and performance of HZSM-5 zeolites were studied in this work. X-Ray diffraction, N2 physisorption, 27Al magic angle spinning nuclear magnetic resonance (MAS NMR), and temperature-programmed desorption of ammonia results indicated that the high-temperature treatment at 650 °C hardly affected the inherent crystal and texture of HZSM-5 zeolites but facilitated the conversion of framework Al to extra-framework Al, reducing the acid site and enhancing the acid strength. Moreover, the high-temperature treatment improved the performance of HZSM-5 zeolites in n-heptane catalytic cracking, promoting the conversion and light olefins yield while inhibiting coke formation. Based on the kinetic and mechanism analysis, the improvement of HZSM-5 performance caused by high-temperature treatment has been attributed to the formation of extra-framework Al, which enhanced the acid strength, facilitated the bimolecular reaction, and promoted the entropy change to overcome a higher energy barrier in n-heptane catalytic cracking. [Display omitted]