One-Step Carbothermal Reduction Synthesis of Metal-Loaded Biochar Catalyst for In Situ Catalytic Upgrading of Plastic Pyrolysis Products

A novel biochar-supported metal catalyst was prepared in this study using a one-step carbothermal reduction synthesis method for the catalytic pyrolysis of plastics. Several catalysts with different metals (Cu, Fe, Ni, and Ru) loaded on three biochar supports from lignin, soybean straw, and Chlorella vulgaris were evaluated using XRD, FTIR, NH3-TPR, and TEM. Zerovalent metal nanoparticles, including Ni, Cu, and Ru, and various functional groups were observed on the biochar surface. The chemical selectivities of gasoline hydrocarbons (C4–C12 hydrocarbons) reached 76.2% with a remarkable catalytic cracking effect of Ni/lignin biochar on low density polyethylene (LDPE). Catalytic performance was comparable to that of the Ru-based catalyst, which contributed to 85.6% of gasoline hydrocarbons. The Ni/lignin catalytic cracking of plastic waste simulated by LDPE, polypropylene (PP), and polystyrene (PS) showed a maximum selectivity of 87.9% for C4–C12 hydrocarbons and yields of 78.1 mg/g for benzene, toluene, and xylene (BTX). The mechanism related to the cleavage of long chain radicals of polyethylene, polypropylene, and polystyrene as well as the aromatization of aliphatics were proposed.