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论文类型：期刊论文

发表时间：2009-02-28

发表刊物：APPLIED CATALYSIS A-GENERAL

收录刊物：SCIE

卷号：355

期号：1-2

页面范围：184-191

ISSN号：0926-860X

关键字：Coking benzene; Nanoscale HZSM-5; Hydrothermal treatment; Calcination; La2O3 modification

摘要：The objective of this work is to study some post-treatment effects, including hydrothermal treatment, calcination and La2O3 modification, on the catalytic performance of a nanoscale HZSM-5 zeolite for ethylation of coking benzene. The nanoscale HZSM-5 zeolite was treated by hydrothermal treatment, calcination and La2O3 modification in series, and the prepared catalysts were evaluated in a fixed-bed down-flow reactor. The catalyst samples were also characterized by XRD, SEM, NH3-TPD, IR, N-2 adsorption-desorption isotherms, cyclohexane adsorption isotherms and TG. The results showed that both the hydrothermal treatment and the calcination led to a drastic decrease in the total amount of acid sites, while the subsequent La2O3 modification resulted in only a slight increase in the number of acid sites. These post-treatments led to a decrease in the Bronsted/Lewis ratio of the nanoscale HZSM-5 zeolites. The hydrothermal treatment followed by the La2O3 modification created new large micropores on the nanoscale HZSM-5 zeolites, which results in the coexistence of micropores and large micropores. The increase in the catalyst lifetime can be attributed to both suppression of carbon deposit formation and partial accommodation of the formed carbon deposit in La-C-HT-HZSM-5 catalyst with lower acidity, lower ratio of B/L and complicated pore structure. The prepared La-C-HT-HZSM-5 catalyst showed good catalytic stability within 1500 h of time on stream in the ethylation of coking benzene containing high sulfur content (375 ppmw) with ethylene under industrial reaction conditions. (C) 2008 Elsevier B.V. All rights reserved.