from first principles PP-I-1

OY-III-1Methane Activation and Conversion on Ag/H-MFI CatalystGabrienko A.A., Arzumanov S.S., Stepanov A.G.Boreskov Institute of Catalysis SB RAS, Novosibirsk, Russiagabrienko@catalysis.ruAg-containing MFI zeolite is active catalyst for methane non-oxidative conversion to higherhydrocarbons [1,2]. Methane activation is considered to occur on silver cationic species bydissociation of C–H bond with the formation of silver-hydride and surface methoxide [3]. Butthe data obtained give only indirect evidence of this activation mechanism. Formation of thesilver-hydride has been observed only for the methane dissociation on Ag-FAU zeolite, butnot on MFI. The methoxide formation has not been detected at all. So the question arises onthe mechanism of methane activation and conversion to higher hydrocarbons on Ag/H-MFIzeolite.Kinetics of H/D exchange between Brønsted acid sites of pure H-MFI and Ag/H-MFI zeolitesand methane (CD 4 ) has been monitored by 1 H MAS NMR spectroscopy in situ. Significantincrease of the H/D exchange rate has been observed on the Ag-modified zeolite. Theexchange reaction on Ag/H-MFI zeolite occurs 2 orders of magnitude faster as compared tothat on H-MFI zeolite. Thus silver species does influence on activation of C–H bond ofmethane by Brønsted acid sites of the zeolite.Conversion of pure methane and methane in the presence of co-reactant higher alkanes onAg/H-MFI zeolite has been studied by 13 C CP/MAS NMR. Ethene has been observed as theproduct of pure methane conversion at 673 K. Further formation of aromatic hydrocarbonshas been detected at 723 K. So it has been demonstrated for the first time thatAg/H-MFI zeolite catalyzes pure methane conversion to aromatic hydrocarbons. Alsonoticeable involvement degree of the 13 C-label from methane into the reaction products hasbeen observed as the result of joint conversion of methane with co-reactants. These data provethat methane indeed converts to higher hydrocarbons in the presence of a co-reactant higheralkane.Acknowledgements. This work was supported by the Russian Foundation for Basic Research(grant no. 10-03-00555, 12-03-91162).References:[1] S. Miao, Y. Wang, D. Ma, Q. Zhu, S. Zhou, L. Su, D. Tan, X. Bao, J. Phys. Chem. B. 108 (2004)17866.[2] K. Inazu, T. Koyama, A. Miyaji, T. Baba, J. Jpn. Pet. Inst. 51 (2008) 205.[3] T. Baba, H. Sawada, T. Takahashi, M. Abe, App. Catal. A: Gen. 231 (2002) 55.94