Investigation of metal oxide additives onto Na2WO4-Ti/SiO2 catalysts for oxidative coupling of methane to value-added chemicals

The oxidative coupling of methane (OCM) is a closely related reaction process involving the transformation of methane (CH4) and O-2 mixtures into value-added chemicals such as ethylene and ethane (i.e. C2+). This work presents the effects of metal oxide additives into the Na2WO4-Ti/SiO2 catalyst on the performance of the OCM reaction. Several metal oxide additives-including oxides of Co, Mn, Cu, Fe, Ce, Zn, La, Ni, Zr, Cr, and V-were investigated with the Na2WO4-Ti/SiO2 catalyst. All of the catalysts were prepared using co-impregnation and the catalyst activity test was performed in a plug flow reactor at a reactor temperature range of 600-800 degrees C and atmospheric pressure. The physicochemical properties of the prepared catalysts relating to their catalytic activity were discussed by using the information of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) measurements. Na2WO4-Ti/SiO2 added Mn was found to be the most active catalyst, involving shifts of binding energies of W 4f and Ti 2p toward lower binding energies. Moreover, a variety of operating conditions-including reactantto-nitrogen gas ratio, catalyst mass, reactor temperature, and total feed flow rate-were intensively examined for the OCM reaction using the Na2WO4-Ti-Mn/SiO2 catalyst. The maximum C2+ yield was subsequently discovered at 22.09% with 62.3% C2+ selectivity and 35.43% CH4 conversion. Additionally, the stability of the Na2WO4-Ti-Mn/SiO2 catalyst was also monitored with time on stream for 24 h.