Suppressed formation of CO₂ and H₂O in the oxidative coupling of methane over La₂O₃/MgO catalyst by surface modification

Oxidative coupling of methane (OCM) is a promising way to convert methane into C₂ hydrocarbons. However, CO₂ and H₂O are by-products of the reaction. To utilize the higher activity of lanthanum oxide and save its usage, MgO supported La₂O₃ catalyst was prepared. Surface modification of the catalyst with nitric acid was made to suppress the formation of the by-products. Experimental results indicated that the addition of nitric acid increased the surface oxygen species with binding energy of ca. 531.7 eV and at the same time reduced the pore volume of the catalyst. These effects of nitric acid finally led to the increase of C ₂ selectivity and the decrease of the by-products formation. Hydrogen selectivity was found about 14%-18% over the catalysts adopted in this work.