Effect of silicon carbide-based iron catalyst on reactor optimization for non-oxidative direct conversion of methane

Abstract

The conversion of methane to olefins, aromatics, and hydrogen (MTOAH) can be used to stably obtain hydrocarbons when the effect of the catalytic surface is optimized from the reaction engineering perspective. In this study, Fe/SiC catalysts were packed into a quartz tube reactor. The catalytic surfaces of SiC and the impregnated Fe species decreased the apparent activation energies (Ea) of methane consumption in the blank reactor between 965 and 1020 °C. Consequently, the hydrocarbon yield increased by 2.4 times at 1020 °C. Based on the model reactions of ethane, ethylene, and acetylene mixed with hydrogen in the range of 500–1020 °C, an excess amount of Fe in the reactor favored the C–C coupling reaction over the selective hydrogenation of acetylene; consequently, coke formation was favored over the hydrogenation reaction. The gas-phase reactions and catalyst properties were optimized to increase hydrocarbon yields while reducing coke selectivity. The 0.2Fe catalyst-packed reactor (0.26 wt% Fe) resulted in a hydrocarbon yield of 7.1% and a coke selectivity of <2% when the ratio of the void space of the post-catalyst zone to the catalyst space was adjusted to be ≥2. Based on these findings, the facile approach of decoupling the reaction zone between the catalyst surface and the gas-phase reaction can provide insights into catalytic reactor design, thereby facilitating the scale-up from the laboratory to the commercial scale.