文献类型：期刊文献

英文题名：Study on the deactivation mechanism of HZSM-5 in the process of catalytic cracking of n-hexane

作者：He, Mu[1];Ali, Muhammad-Faryad[1];Song, Yue-Qin[1];Zhou, Xiao-Long[1];Wang, Jin An[2];Nie, Xin-Yao[3];Wang, Zheng[1]

机构：[1]East China Univ Sci & Technol, Inst Chem Engn, Int Joint Res Ctr Green Chem Engn, Shanghai 200237, Peoples R China;[2]Inst Politecn Nacl, ESIQIE, Col Zacatenco, Mexico City 07738, Mexico;[3]Qingyang Chem Ind Corp, Liaoyang 11100, Peoples R China

年份：2023

卷号：451

外文期刊名：CHEMICAL ENGINEERING JOURNAL

收录：;EI(收录号：20223512666399);WOS:【SCI-EXPANDED(收录号:WOS:000864082500001)】；

基金：The financial support from the Instituto Politecnico Nacional, Mexico (Grant No. SIP -20220883) is appreciated. H. Mu thanks to the International Joint Research Center of Green Chemical Engineering, at the Institute of Chemical Engineering of the East China University of Science and Technology for supporting his doctoral thesis investigation.

语种：英文

外文关键词：Coke deactivation; Hexane; Zeolite; Acid properties; Decoking

摘要：The coke deactivation over HZSM-5 zeolites with different Si/Al ratios in the n-hexane cracking reaction was studied in 200 h of reaction. In the products, alkanes, C-2(=), C-3(=), C-4(=) and aromatic compounds such as benzene, toluene, and xylene (BTX) were formed. The selectivity variations of C-3(=) and C-4(=) were inverse proportional to that of BTX, indicating that C-3(=) and C-4(=) intermediates were the precursors of BTX compounds. The internal coke was preferentially formed inside zeolite micropores in the initial reaction period (0-70 h), which significantly diminished the micropore volume, covered the strong acid sites, and strongly inhibited catalytic activity of the catalysts with lower Si/Al ratio. The external coke was principally formed after 70 h of reaction and had a less influence on the catalytic activity. The internal coke (density 1.03 g.cm(-3) and a H/C ratio of 1.16) could be effectively removed by H-2 treatment at 850. C; while the external coke (density 1.46 g.cm(-3) and a H/C ratio of 0.28) with graphite-like structure resisted H-2 treatment. For the zeolites with low Si/Al molar ratio (25 and 50), the rapid coking stage (0-70 h) occurred at high n-hexane conversion followed by a slow deactivation stage at low conversion (70-200 h); for zeolites with high Si/Al molar ratio (85 and 130), a very slow deactivation stage took place in the reaction period (0-70 h), followed by a faster deactivation stage (70-200 h). This work demonstrated that zeolite deactivation behavior was correlated not only with the strong acid sites and microporosity of catalyst, but also affected by the location, amount, structure, and type of coke. The mechanisms for internal and external coke formation and H-2 decoking strategy for the deactivated catalyst regeneration were discussed and proposed.