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

Abstract

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.