Reactivity of C1 Surface Species Formed in Methane Activation on Zn-Modified H-ZSM-5 Zeolite

• Published in: Chemistry : a European journal Vol. 16; no. 47; pp. 14016 - 14025
• Main Authors: Wu, Jian Feng, Wang, Wei David, Xu, Jun, Deng, Feng, Wang, Wei
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 17.12.2010; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Subjects: Activation; Atmospheric chemistry; Carbon dioxide; Carbon monoxide; Catalysts; Chemistry; Formates; Methane; methane activation; Methanol; Methyl alcohol; reactivity; Spectroscopy; Surface chemistry; Zeolites; Zinc
• ISSN: 0947-6539; 1521-3765; 1521-3765
• DOI: 10.1002/chem.201002258

Solid‐state 13C magic angle spinning (MAS) NMR spectroscopy investigations identified zinc methyl species, formate species, and methoxy species as C1 surface species formed in methane activation on the zeolite Zn/H‐ZSM‐5 catalyst at T≤573 K. These C1 surface species, which are possible intermediates in further transformations of methane, were prepared separately by adsorption of 13C‐enriched methane, carbon monoxide, and methanol onto zinc‐containing catalysts, respectively. Successful isolation of each surface species allowed convenient investigations into their chemical nature on the working catalyst by solid‐state 13C MAS NMR spectroscopy. The reactivity of zinc methyl species with diverse probe molecules (i.e., water, methanol, hydrochloride, oxygen, or carbon dioxide) is correlated with that of organozinc compounds in organometallic chemistry. Moreover, surface formate and surface methoxy species possess distinct reactivity towards water, hydrochloride, ammonia, or hydrogen as probe molecules. To explain these and other observations, we propose that the C1 surface species interconvert on zeolite Zn/H‐ZSM‐5. As implied by the reactivity information, potential applications of methane co‐conversion on zinc‐containing zeolites might, therefore, be possible by further transformation of these C1 surface species with rationally designed co‐reactants (i.e., probe molecules) under optimized reaction conditions. Reactivity of C1 surface species: Zinc methyl species, formate species, and methoxy species were identified as C1 surface species formed in methane activation on the zeolite Zn/H‐ZSM‐5 catalyst at T≤573 K (see graphic). We successfully isolated each surface species and investigated their chemical nature on the working catalyst by solid‐state NMR spectroscopy.