EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Methane, the main component of biogas, can be used for the production of heat, electricity, and chemicals. The reaction of methane oxidative coupling (OCM) is a promising process that can produce value-added products (ethylene and ethane) via the direct conversion of methane. Normally, the direct gas-phase reaction of OCM can occur at high temperatures (> 700 °C). However, the chemical durability of CH4 and the thermodynamically favorable production of CO and CO2 make the production of higher hydrocarbons (C2) extremely complicated. In the work presented herein, La2O3-MgO-CeO2 catalysts were tested during the OCM. The catalysts were prepared using the citrate sol-gel method, to increase the homogeneity of the mixed metal oxides. The moral ratio between the metals La, Mg and Ce was also varied to tune the support basicity, the population of basin sites (O2−) and to increase the surface active oxygen sites. The morphological, textural, and structural characteristics of the catalytic samples were investigated using Raman spectroscopy, X-ray diffraction, N2 physisorption-desorption, CO2 Temperature-programmed Desorption, H2- Temperature-programmed Reduction and X-ray photoelectron spectroscopy. It was shown that the addition of La3+ increased the surface basicity and the concentration of superoxide (O2−) and peroxide species (O22−) on the catalyst surface, which are characterized as the main active centers that improve the activation of methane to form a methyl radical (CH3.) intermediate product to generate ethyne and ethane. Finally, the activity experiments were performed at Weight Gas Hourly Space Velocity = 10,000 mL g−1 h−1 with moral ratio CH4/O2 = 4:1 at reaction temperature range between 650 and 870oC and showed that the La0.6Ce0.3Mg0.1Ox catalyst presented the highest C2H4 and C2H6 selectivity and yield at low reaction temperatures.