Enhancement of methanol production by electronic interactions of La–Zn in plasma catalytic direct oxidation of methane under mild conditions

Abstract

The plasma catalytic direct oxidation of methane into the value-added chemical methanol over a LaZnAl catalyst was investigated under mild conditions. A synergistic effect between plasma and the LaZnAl catalyst was achieved, driven by the electronic interaction between La and Zn species. This interaction facilitated the formation of oxygen vacancies, enhanced the utilization of the plasma-activated oxygen radicals, and promoted the formation rate of the key intermediate CH₃O species, thereby leading to low apparent activation energies for methane conversion and methanol production. The lowest activation energies were determined to be 47.95 kJ mol⁻¹ for E_a,CH4 and 17.76 kJ mol⁻¹ for E_a,CH3OH. The interaction of La–Zn species resulted in a significantly enhanced contribution of 89.6% to methanol formation, whereas the contribution of Zn alone was only 23.7%, and that of La was even negative (−32.9%). Consequently, methanol production was markedly improved and a methanol selectivity of 40.9% was achieved over the LaZnAl catalyst, compared to 26.7% for ZnAl and 14.5% for LaAl. These findings provide a broadly applicable framework for rational and targeted catalyst design in plasma catalysis, extending beyond specific material systems.