Structural effect of one-dimensional nanowire 2%Mn-5%Na2WO4/SiO2 catalyst towards oxidative coupling of methane

Nanowire-structured 2%Mn-5%Na2WO4/SiO2 was successfully synthesized and demonstrated superior catalytic performance compared to its powder form across the entire temperature range of 650–800 °C. In this study, the hydrothermal synthesis time for the nanowires was varied at 8, 12, 17, and 24 h, referred to as NWs-8, NWs-12, NWs-17, and NWs-24, respectively. NWs-12 exhibited the smallest diameter and the longest length among the synthesized nanowires. However, NWs-17 showed the best performance for the oxidative coupling of methane (OCM) process, despite having a relatively less impressive morphology. This superior performance could be attributed to the presence of Mn2O3 active species without interference from MnO2, which was only observed in NWs-17 and NWs-24. The larger crystal size of NWs-24 contributed to its poorer performance compared to NWs-17. NWs-17 achieved a maximum C2+ selectivity of 68% and a high CH4 conversion rate of 21.8% under operating conditions of 775 °C, CH4:O2 = 4, and WHSV = 8572 ml/h/g.