Methane Dehydroaromatization on Mo/HMCM-22 Catalysts: Effect of SiO 2 /Al 2 O 3 Ratio of HMCM-22 Zeolite Supports
- PDF / 278,469 Bytes
- 6 Pages / 593.972 x 792 pts Page_size
- 39 Downloads / 155 Views
Catalysis Letters Vol. 108, Nos. 1–2, April 2006 (Ó 2006) DOI: 10.1007/s10562-006-0023-0
Methane dehydroaromatization on Mo/HMCM-22 catalysts: effect of SiO2/Al2O3 ratio of HMCM-22 zeolite supports Lin Liu, Ding Ma, Huiying Chen, Heng Zheng, Mojie Cheng, Yide Xu, and Xinhe Bao* State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, P.O. Box 110, Dalian 116023, P.R. China
Received 19 November 2005; accepted 19 January 2006
HMCM-22 zeolite with variable SiO2/Al2O3 ratios has been successfully synthesized and used as support of molybdenum based catalyst in methane dehydroaromatization. Effect of SiO2/Al2O3 ratio on the catalytic performance of Mo/HMCM-22 catalysts was studied, and results show that methane conversion and benzene selectivity increase with the decrease of SiO2/Al2O3 ratio, and reach maximum on Mo/HMCM-22 catalyst with SiO2/Al2O3 ratio of 25. Further increasing SiO2/Al2O3 ratio results a decrease of activity and benzene selectivity. 27Al MAS NMR spectroscopy and NH3-TPD techniques were applied to characterize the structure–property relationship of the catalyst. The catalytic performance of Mo/HMCM-22 catalysts in methane dehydroaromatization has been correlated with the Bro¨nsted acidity of HMCM-22 zeolite supports, which may promote not only the methane activation on the Mo carbide sites of Mo/HMCM-22 catalysts, but also further oligomerization of the CHx surface species towards aromatics products in the reaction. KEY WORDS: methane dehydroaromatization; HMCM-22 zeolite; Mo/HMCM-22 catalyst; SiO2/Al2O3 ratio; Bro¨nsted acidity.
1. Introduction Natural gas (mostly methane) is becoming a promising energy source in the 21st century, but now the utilization of the resource is limited by the high cost of transportation [1,2]. Developing efficient utilization processes of abundant natural gas to valuable liquid fuels and petrochemical intermediates has become a field of continuous interest not only from the standpoint of academic research but also from the potential industrial application. In 1993, Xu and his colleagues [3] first reported that methane could be transformed into aromatics of benzene and naphthalene on Mo/HZSM-5 catalyst under nonoxidative conditions at 973 K. Since then, methane dehydroaromatization reaction has received considerable attention during the past 12 years [4–21]. Mo modified HZSM-5 zeolite catalyst is a bi-functional catalyst with a synergic effect between the molybdenum species and the HZSM-5 zeolite, which results in a efficient catalyst for methane dehydroaromatization with a methane conversion of about 10% and benzene selectivity of 50–60% at 973 K [7–9,16–21]. In addition to Mo/HZSM-5, we recently reported that Mo/HMCM-22 catalysts showed better catalytic performance with higher benzene selectivity (ca. 80% in maximum) as well as a better tolerance to carbonaceous deposits, as compared with Mo/HZSM-5 catalyst under *To whom correspondence should be addressed. E-mail: [email protected]
the same experimental condition
Data Loading...
