Microwave-Assisted Catalytic Pyrolysis of Biomass with Biochar Materials Derived from Spent Lithium-Ion Batteries:Microwave Absorption and Pyrolysis Characteristics

Abstract

Microwave-assisted catalytic pyrolysis (MACP) of biomass into high-value products is a promising strategy for solving the global increasingly severe energy and environmental issues. However, this strategy is still limited by the lack of low-cost and efficient catalysts with strong microwave absorption. In this study, a series of biochar materials derived from spent lithium-ion batteries (BC, HC, sLFPHCs and sNCMHCs) were developed for the catalysts in MACP of biomass. Microwave absorption and the MACP characteristics of rice straw with these biochar materials were investigated. The results showed that these biochar materials have better microwave absorption than SiC. Since the increase in graphitization after microwave calcination, their ε' ,ε" and tanδε increased and the RLmin decreased significantly together with higher maximum heating rates (630 ~720 ℃/min) at the microwave power of 800W (2.45GHz). The MACP of rice straw with these biochar materials showed higher yields of H2-rich syngas and lower yields of liquid products at microwave power of 360W and less than 350 ℃. Analysis of these liquid products showed increases in the hydrocarbon content, especially monocyclic aromatic hydrocarbons (MAHs), and the polymerization of MAHs to form polycyclic aromatic hydrocarbons was inhibited. In particular, the MACP with sNCMHC-C obtained the highest selectivity of H2 (50.22 vol. %) in the gaseous products, MAHs (18.86 area. %) and benzene, 1-propynyl- (17.41 area. %) in the liquid products. This study suggests that the MACP with biochar materials derived from spent lithium-ion batteries has a high potential to promote high-value recycling of waste biomass.

Keywords: microwave-assisted biomass pyrolysis, biochar, spent lithium-ion battery recycling, microwave absorber