Investigating the promotion of Fe–Co catalyst by alkali and alkaline earth metals of inherent metal minerals for biomass pyrolysis

The alkali and alkaline earth metals (AAEMs) in the inherent metallic minerals of biomass have a crucial effect on the pyrolysis process. In our previous work, the experiments mainly investigated the effects of Fe–Co catalysts on pine needle (PN) pyrolysis. This work further explored the synergistic effect of AAEMs (K, Ca, Na, and Mg) with Fe–Co-catalyzed biomass pyrolysis. The results showed that AAEMs in biomass could improve the gas yield by promoting decarbonization, decarboxylation, and hydrocarbon conversion. Adding Co to Fe enhanced the stability and anti-coking properties of the catalyst, which facilitated the breakage of C–H/C–C bonds and the conversion of oxygenated compounds to hydrocarbons, increasing the H2 yield (13.99 mL/g → 92.50 mL/g). AAEMs enhanced the catalytic activity of Fe–Co catalysts with high selectivity for H2 (92.50 mL/g→104.81 mL/g) and CO (65.00 mL/g→73.65 mL/g). The characterization results showed that AAEMs promoted the reduction of Fe–Co catalyst and the dispersion of metal active sites, which facilitated the transition from disordered to ordered carbon and the removal of oxygen functional groups such as O–H, thus increasing the CO yield, while the effective cleavage of CH4 and C2 compounds and the dehydrogenation of organic components promoted the increase of H2 yield, and the activity followed Na > Ca > Mg > K.