The Effect of Drying Technique of Silica Support on Properties and Catalytic Activity of Multi-Metal Catalyst for Oxidative Coupling of Methane

Abstract

Oxidative coupling of methane (OCM) is an alternative reaction for the direct conversion of methane into high-value hydrocarbons. Silica is more favoured for using as a catalyst support of metal catalyst used in OCM reaction. The affective catalyst used in OCM reaction is Na₂WO₄-Mn₂O₃/SiO₂ (NWM) catalyst. Drying is one of the processes directly effect on the characteristics and performance of catalysts. Microwave drying has been reported to be the effective drying method for catalyst preparation. The effect of microwave drying of silica support for multi-metal catalyst synthesis is very limited. The objective of this work was to investigate the effect of microwave (MW) drying with different power levels, compared to hot air (HA) drying for silica support preparation on the characteristics and performance of the Na₂WO₄-Mn₂O₃/SiO₂ catalyst for employing in OCM reaction. Silica support was prepared by the sol-gel method and the Na₂WO₄-Mn₂O₃/SiO₂ catalyst was prepared by incipient wetness impregnation method. The result showed that N₂-sorption isotherm of HA and MW dried silica support showed similar isotherm. These isotherms exhibited the type IV isotherm with H1 hysteresis loop, considered as the characteristic of mesopore structure and high uniform of pore size. MW dried silica support showed the high surface area and pore volume, while HA dried silica support showed densely packed particles with small pore volume. Moreover, the MW dried silica support exhibited greater dispersion and more uniform distribution of active Mn and W components after loading of Mn and W metal species, compared to HA dried silica support. NWM catalyst, which the silica support dried by microwave drying with the power of 1,000 W, displayed the highest methane conversion and the highest yield of C₂₊ hydrocarbon at a reaction temperature of 800 °C.