Nitrogen Fixation Through Al2O3-Based Catalysts Embedded in a Microwave Plasma Post-Discharge

The conventional Haber-Bosch process for nitrogen fixation is energy-intensive and associated with high greenhouse gas emissions. Plasma-assisted catalysis represents an alternative approach for nitrogen oxidation under milder conditions. In this study, catalyst-assisted microwave plasma was investigated using alumina-based catalysts and alumina-supported metal oxides (Mo, W, Co, and Ni). Microwave plasma alone predominantly produced NO, whereas the presence of catalysts promoted additional NO2 formation, indicating the importance of plasma-catalyst interactions. Catalytic performance depended strongly on the physicochemical properties of alumina, with delta-Al2O3 exhibiting the highest activity. Mo- and W-loaded catalysts further enhanced NOx formation, while Ni and Co showed weaker effects. An overall increase of up to ~30% in NOx production was achieved compared to plasma alone.