Methane conversion to ethylene over GaN catalysts. Effect of catalyst nitridation

Vast availability of natural and shale gases makes methane a reliable source for synthesizing valuable chemical building blocks such as ethylene. A new stable supported GaN/SBA15 catalyst from an emerging class of nitride catalysts was reported for the direct non-oxidative methane coupling to ethylene. The effect of nitridation on the catalyst properties and activity was investigated. The optimum nitridation temperatures were 700 degrees C and 750 degrees C for the GaN/SBA15 and the unsupported GaN catalyst, respectively. Supported catalysts were more stable and had 5-10 times higher product (ethylene) formation rates per gram of gallium than the unsupported catalysts due to the higher surface area ( > 320 vs. < 20 m(2)g(-1)) and Ga-dispersion inside the pores. Compared to the oxide precursors, the nitrides exhibited a higher atom conversion efficiency for the CH 4 carbon leading to higher ethylene selectivity (71 % for GaN/SBA15, < 58 % for Ga2O3 /SBA15) and lower coke selectivity (27 % for GaN/ SBA15, 40 % for Ga2O3 /SBA15).