Role of biochar-based catalysts in microwave-induced biomass pyrolysis: Structural properties and modification with Fe-series metals

Abstract

Biochar-based catalysts have great potential for microwave-induced biomass pyrolysis due to the combination of their excellent microwave absorption performance, good porous structure, and high catalytic activity. In this work, the potential of biochar-based catalysts for microwave-induced catalytic biomass pyrolysis to produce gaseous fuel and upgrade bio-oil was explored and the role of the structural characteristics and Fe-series modification was revealed. The results indicated that the catalytic performance of pure biochar was influenced by their microstructures, and the KOH-activated biochar with abundant microporous structures could effectively promote the gas yields from biomass pyrolysis under microwave heating conditions. With the loading of Fe0 crystal nanoparticles on biochar, the catalytic activity of biochar was greatly enhanced, resulting in an increase in combustible gas (CO, H2 and CH4) yield by 50 % compared to pure biochar, reaching 502.09 mL/g at 650 °C, as well as significant simplification of the bio-oil. Furthermore, the Fe-series alloy crystals exhibit superior catalytic activity over Fe0, further improving gas yields and promoting bio-oil upgrading. The biochar loading of Fe0.64Ni0.36 nanoparticles resulted in a combustible gas yield as high as 574.84 mL/g, and the production of hydrocarbons was greatly enhanced, with a high relative content of 33.9 % in bio-oil. Biochar-based CoFe nanoparticles promoted selective production of H2, with a yield as high as 230.84 mL/g, and the content of mono-phenols in the bio-oil was improved to 74.0 % with the composition of a high phenol relative content of 17.508 %, a trans-isoeugenol relative content of 17.260 %, and a guaiacol relative content of 12.780 %.