Conversion of Methane to Value-Added Hydrocarbons via Modified Fischer–Tropsch Process Using Hybrid Catalysts

Abstract

Typically, the conversion of methane to value-added hydrocarbon (C₂₊) via the oxidative coupling of methane is accomplished using high energy due to the temperature of the operation (more than 700 °C). The conversion of methane to C₂₊ was investigated using a hybrid catalyst consisting of 15 wt% of Ni on Al₂O₃ (15Ni/Al₂O₃) and 10–25 wt% of Co supported on Al₂O₃ (Co/Al₂O₃) packed as a prioritized layer in a reactor. The effects of operating conditions—different Co loading in Co/Al₂O₃, reactor pressure and temperature, percentage of O₂ in the feed, total feed flow rate, and different weights of Co/Al₂O₃—on the performance of the hybrid catalyst were studied for the reaction. The highest performance (3.6% C₂₊ yield with 7.9% C₂₊ selectivity and 46.3% CH₄ conversion) of the hybrid catalyst was achieved at 6 bar, 490 °C, 37.5% of O₂ in the feed, a total flow rate of 50 ml/min, and using 0.25 g of 15Ni/Al₂O₃ and 0.1 g of 15 wt% of Co/Al₂O₃ (15Co/Al₂O₃). The prepared catalysts were characterized using X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, N₂-sorption analysis, X-ray photoelectron spectroscopy, NH₃- and CO₂-temperature-programmed desorption, and thermogravimetric analysis to acquire the chemical and physical properties of the catalysts. A time-on-stream testing of the optimized hybrid catalyst for 24 h was performed to determine the stability of the catalyst and revealed that the formation of coke caused rapid deactivation of the catalyst.