Catalytic performance of Mn- and Co-modified iron-based oxides for gas quality improvement in biomass gasification

Efficient catalytic gasification is essential for improving producer gas quality by enhancing tar destruction, and thus more sustainable biomass-to-energy pathways. Iron oxides and spinel ferrites (MFe 2 O 4 ) have attracted attention as gasification catalysts due to their redox versatility and structural stability, with the divalent cation playing a crucial role in oxygen mobility and metal-oxygen bond strength. In this work, the effect of Co and Mn as divalent cations in spinel ferrites was investigated and compared with hematite during biomass gasification. Catalysts were synthesized via wet impregnation method combined with microwave-assisted calcination, and characterized by XRD, XRF, BET, SEM/EDS, TGA, and Raman. Their performance was evaluated following the improvement of gas quality during gasification of residual forest biomass in a bench-scale bubbling fluidized bed reactor. The gasification conditions were 850 °C, equivalence ratio of 0.25 and air as gasifying agent. The results show that catalytic activity for gas quality improvement followed the sequence CoFe 2 O 4 > MnFe 2 O 4 > Fe 2 O 3 , mainly due to differences in M − O bond strength and redox flexibility. The Co-based catalyst exhibited the highest performance, increasing the H 2 production by 115% and the H 2 :CO molar ratio by 95%, while decreasing tar production by 66% relative to the reference condition. Process parameters such as CGE, CCE, gas yield and LHV were less affected by the catalyst than the producer gas composition. These results show the positive effect of divalent cations in spinel ferrites and contribute to the rational design of catalysts for efficient biomass to syngas conversion.