Investigation of CH.sub.x Adsorption on Mo.sub.2C and Mo.sub.4C.sub.2 Sites Incorporated in ZSM-5 Zeolite Using Periodic-DFT Approach

• Published in: Catalysis letters Vol. 148; no. 1; p. 68
• Main Authors: Shetty, Sharankumar, Sivakumar, S, Jana, Suman Kumar, Sreenivasarao, G
• Format: Journal Article
• Language: English
• Published: Springer 01.01.2018
• Subjects: Animal behavior; Methane; Zeolites
• ISSN: 1011-372X
• DOI: 10.1007/s10562-017-2199-x

One of the major challenges of methane dehydroaromatization technology development is rapid deactivation of the catalyst due to the coke formation. The coke formation depends on the stability of CH.sub.x species formed during the stage of CH.sub.4 activation. In the present computational study, we have employed periodic-DFT approach to investigate the adsorption behavior of the CH.sub.x (x = 2-4) species on Mo.sub.2C and Mo.sub.4C.sub.2 clusters incorporated at three different Al substitutions viz. T8-T8, T8-T12 and T8-T7. The results indicate that the Mo.sub.2C cluster is responsible for weaker CH.sub.4 adsorption compared to Mo.sub.4C.sub.2. However, the CH.sub.3 and CH.sub.2 species are chemisorbed on the Mo.sub.2C cluster. Interestingly, in the case of Mo.sub.4C.sub.2 cluster we found two chemisorbed states of CH.sub.2 species. From this analysis, we propose that the relatively weaker chemisorbed state of CH.sub.2 in the top-site would be responsible for the formation of C.sub.2 intermediate leading to desired aromatics, while the strongly chemisorbed CH.sub.2 state will lead to undesired C formation. Graphical