Investigation on microwave pyrolysis mechanism and synergism of seaweed and rice husk with comprehensive experimental and theoretical study

Microwave co-pyrolysis for producing bio-oil and bio-gas is a green and sustainable way to realize efficient energy conversion, and the understanding of synergism is necessary for source control of pyrolysis reactions. In this study, individual and synergistic microwave pyrolysis of sargassum (SS) and rice husk (RH) were investigated experimentally and theoretically, to clarify the pyrolysis mechanism and synergism. The release behaviors of bio-oil and bio-gas from SS and RH are similar. The trends of H2, CO, and CH4 yield with pyrolysis process are consistent, while that of CO2 is different, due to its lower generation energy barrier. The yield of H2, CO, CO2 and CH4 are all increase with temperature. Oxygen-containing compounds is the dominate in bio-oil. Phenol is the main oxygen-containing compound in bio-oil of RH due to the decomposition of lignin, while more phenol is released to biol-oil of SS than furan due to the introduction of free hydrogen atom. During co-pyrolysis, due to the the synergism, the yield of bio-gas, H2 and CO2 are increased, while that of CO and bio-oil barely changed. But the distribution of components in bio-oil were changed, and the generation and aromatization of oxygen-containing compounds and hydrocarbon were promoted. The synergism of SS and RH is mainly caused by the intermolecular reactions between aliphatic volatiles generated from SS with BTEX in bio-oil/char generated from RH and the catalytic effect of AAEM.