Catalytic Activity and Reusability of Nickel-Based Catalysts with Different Biochar Supports during Copyrolysis of Biomass and Plastic

Abstract

Low-cost biochar is a promising catalyst support for catalytic pyrolysis to produce pyrolysis oil, pyrolysis gas, and carbon nanomaterials (CNMs). The effect of different Ni/biochar (four kinds of original biochar and three kinds of modified biochar) catalysts on the yield and properties of copyrolysis products from Chinese herb residue and reused polypropylene (PP) was studied. Results show that the modified biochar support had a high surface area and high catalytic activity. Particularly, Ni/ZC (ZnCl2-modified biochar) obtained higher yields of CNMs (2.92 wt %) and pyrolysis gas (55.44 wt %). Moreover, it exhibited high stability in repeated use experiments. Interestingly, the Ni/ZC catalyst showed the highest catalytic activity during second reuse (ZC-R2) due to moderate precoking. The high content of hydrocarbons and the C6–C20 component in the ZC-R2 group is attributed to the stronger secondary cracking capacity. The stronger secondary cracking capacity of the front-end catalyst may increase the content of CH4 in pyrolysis gas. Therefore, the Ni/ZC catalyst significantly increased the yield of a high-quality 3D graphitic carbon network structure in a second-stage reactor. This work contributes to the industrial application of catalytic pyrolysis technology by reducing the catalyst cost and increasing the product value.