Magnetic field effect on mechanism and syngas products of microalgae pyrolysis with activated carbon catalysts

Abstract

H₂-rich syngas has various applications, but it is primarily produced from fossil fuels, contributing to greenhouse gas emissions. Its conversion from renewable sources, such as biomass, can bring environmental benefits and help achieve a reduction in global temperatures below 2 °C. Biomass conversion through the thermal process offers a promising solution for syngas generation. Pyrolysis is appealing as it is more cost-effective than other thermal conversion technologies. The objective of this study is to investigate the conversion of Spirulina microalgae (SP) into syngas (CH₄, H₂, and CO₂) using activated carbon (AC) as a catalyst under the influence of a magnetic field, employing a fixed-bed pyrolysis reactor. Characterization on raw and char SP reveals those biomasses’s main component affecting volatile population, CH₄ and H₂ correlated with protein and lipid decomposition; on the other hand, CO₂ product depends on carbohydrates degradation. An investigation of fresh and spent AC indicates that the main catalytic interaction between pyrolysis vapor and AC is through the Van der Waals force. The magnetic field helps prevent pore blocking on AC, which is proved by specific surface analysis results indicating in a positive synergistic effect between the magnetic field and AC. Activated carbon and magnetic field affected syngas production through a series of pyrolysis vapor cracking, deoxygenation, and hydrocarbon declustering, enhancing CH₄ and H₂ production by 28.66 and 8.4 %, respectively, and suppressing CO₂ by 28.64 % compared to SP pyrolysis alone.