One of the most challenging aspects of modern day catalysis is the activation of methane, a major component of natural gas. Mo/W carbides supported on ZSM-5/MCM-22 are some of the most active catalysts to activate methane. The metal carbides are reported to be responsible for methane activation by forming CHx species.The CHx species is dimerized into C2Hy species, which are then cyclized on the available acidic sites of ZSM-5, producing aromatics, among other products. In our previous study, Mo2C supported on sulfated zirconia (SZ), a well-known superacid with strong acidic sites showed activity for methane conversion. In the present work, WC supported on SZ was tested for methane conversion. 5 wt. % WOx was doped on SZ and studied for the activation of methane at 650oC-750oC. DRIFTS was used to investigate any change in surface acidity when WOx was doped on SZ. WOX was first reduced under H2 at reaction temperature. It was then carburized under 1:4 CH4:H2 ratio to carburize WO to WC. Products observed were primarily ethylene, ethane, propylene and propane, along with aromatics including benzene, toluene and ethylbenzene. Methane conversion increased with temperature (not shown). C2 selectivity increased noticeably at higher temperatures, whereas benzene selectivity decreased significantly with time (Figures 1, 2). It appears that the WC sites, which are generally thought to be responsible for the dimerization of methane, do not deactivate with time. However, the SZ acid sites, which are responsible for the cyclization of the C2 intermediates to aromatics, deactivate rapidly. These aromatics are coke precursors, as confirmed in subsequent TPO results.

Effect of temperature in activation of methane using WC catalyst supported on sulfated zirconia

256th National Meeting (2018)

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