Thermocatalytic Conversion of Automotive Shredder Waste and Formation of Nanocarbons as a Process Byproduct

Thermocatalytic conversion of plastic wastes using titanium dioxide (TiO₂) is a novel and promising approach for waste management and sustainable production of materials. In this approach, the heat-treatment of a mixture of plastic waste and TiO₂ at elevated temperatures helps to achieve fast and complete decomposition and offers several advanced byproducts. In this study, the different physicochemical interactions between TiO₂ and an industrial plastic waste (i.e., automotive shredder residue, ASR) at elevated temperatures were investigated. The nonisothermal degradation kinetics of ASR, with and without TiO₂, were calculated from the thermogravimetric analysis (TGA) and results confirmed that the TiO₂ influences and catalyzes the degradation of ASR. The analysis of the resulting gas showed that the TiO₂ limits the formation of CO₂ gas, which is considered an unfavorable product of thermal processes, without changing the quality of the hydrocarbons (i.e., oils) generated during the heat treatment of ASR. While ASR decomposes, TiO₂ transforms into value-added Ti-based ceramics; this transformation generates a high yield of CO that can be collected for commercial purposes. In addition, TiO₂ led to the formation of considerable quantities of onion-like carbon nanoparticles (OLC-NPs) from the gas phase; this product was characterized and its formation mechanism was discussed.