Direct Non-Oxidative Conversion of Methane to C2 Hydrocarbons, Aromatics and Hydrogen
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Catalytic activity of Fe/HZSM-5 and Mo/HZSM-5 during methane dehydroaromatization was investigated. The catalysts were prepared by wet impregnation method, calcinated in air flow, tested in laboratory reactor and characterized by nitrogen adsorption, TGA and DSC. The results show that conversions increase with temperature but also coke formation increases resulting to faster deactivation. CO2 is produced first, then C2 hydrocarbons such as ethane, ethylene and acetylene are produced and benzene is the last produced product. These facts support the mechanism, which says that metal oxide on a catalyst is first converted to carbide, C2 are produced on carbide sites and oligomerized on acid sites. Fe/HZSM-5 was regenerated at 600°C and Mo/HZSM-5 was regenerated at 500 and 600°C. Catalytic activity of the catalysts regenerated at 600°C was significantly lower than catalytic activity of fresh ones but at 500°C there was only slight decrease.Amount of coke and the temperature, when the coke is burned were increasing with reaction temperature. Furthermore, surface areas and micropore volumes of used catalysts were decreasing significantly only when the catalysts showed relatively high activity. These results indicate different nature of coke produced at various temperatures.