%0 Journal Article
%T Comparison of Two Preparation Methods on Catalytic Activity and Selectivity of Ru-Mo/HZSM5 for Methane Dehydroaromatization
%A Lucia M. Petkovic
%A Daniel M. Ginosar
%J Journal of Fuels
%D 2014
%R 10.1155/2014/364107
%X Catalytic performance of Mo/HZSM5 and Ru-Mo/HZSM5 catalysts prepared by vaporization-deposition of molybdenum trioxide and impregnation with ammonium heptamolybdate was analyzed in terms of catalyst activity and selectivity, nitrogen physisorption analyses, temperature-programmed oxidation of carbonaceous residues, and temperature-programmed reduction. Vaporization-deposition rendered the catalyst more selective to ethylene and coke than the catalyst prepared by impregnation. This result was assigned to lower interaction of molybdenum carbide with the zeolite acidic sites. 1. Introduction Catalytic methane dehydroaromatization is a potential alternative to methane steam reforming to produce hydrogen. It is also an alternative for production of valuable aromatics from oil-associated gases that are usually flared. Since its first report in 1993 [1], however, methane dehydroaromatization continues to be a challenge from both scientific (nature of catalyst active sites) and industrial (catalyst activity and stability) points of view [1¨C9]. The most promising catalyst is Mo/HZSM5 [1, 10¨C13]. Dehydroaromatization of methane on Mo-zeolite catalysts has been proposed to follow an initial induction period during which Mo is reduced to molybdenum carbide (MoCx). Methane activation occurs on MoCx which leads to the formation of ethylene and hydrogen. Ethylene then reacts on the zeolite acidic sites to form aromatics [14, 15]. The acid sites and channel structure of the zeolite and the state and location of Mo species are fundamental factors for good catalytic performance [16]. A number of different preparation methods and incorporation of different promoters have been reported [10, 17, 18]. In particular, Weckhuysen et al. [10] reported that the incorporation of molybdenum onto the HZSM5 zeolite by impregnation produced a catalyst that displayed higher activity and shorter initial induction period than solid state ion-exchanged materials. Tessonnier et al. [19] reported that catalysts prepared by direct vaporization-reaction of MoO3 displayed increased activity and limited deactivation. Reports also indicate that incorporation of ruthenium on Mo/HZSM5 catalysts improves catalyst performance [17, 20, 21]. The work reported here shows a comparison of the catalytic performance of Mo/HZSM5 and Ru-Mo/HZSM5 catalysts prepared by impregnation and vaporization-deposition and the results are interpreted in terms of catalyst characterization analyses. 2. Experimental 2.1. Catalyst Preparation Four catalyst samples were prepared and labeled as follows: MV and RMV for
%U http://www.hindawi.com/journals/jfu/2014/364107/