The mechanism of plasma affecting biomass pyrolysis to more H₂, activated char and less CO₂

The current application of plasma in pyrolysis mainly focuses on the secondary cracking of tar, while the effect of plasma on solid-phase char formation during the direct pyrolysis of biomass has not been investigated in detail. In this paper, a high-temperature dielectric barrier discharge reaction system was designed to introduce plasma into a direct pyrolysis, and the mechanism was also explored by combining a pin-plate dielectric barrier discharge structure and in-situ diffuse reflectance infrared spectroscopy for detection. The results show that the plasma mainly breaks the C-H bonds in cellulose, leading to the release of up to 200 times more H₂ than normal pyrolysis. Additionally, CO₂ is ionized or re-adsorbed on the surface of the char, where it is converted into CO for release, which causes a reduction in CO₂ emissions of nearly 70%. The use of plasma can obtain deoxygenated and refined char that is still highly active. This paper clarifies the favorable effects of directly introducing plasma into biomass pyrolysis and provides a detailed description of its action mechanism, which will be important for the utilization of plasma in practical pyrolysis applications.