A review on carbon materials production from plastic wastes

Approximately 36 million tons of waste plastics are generated in the United States each year, most of which are discharged into the environment and end in landfills. This is potentially a serious threat to the ecosystem and human health. Considering that the production of liquid fuels and chemicals from waste plastics is difficult to make profits and achieve zero carbon emissions, transforming waste plastics into high-quality carbon materials becomes more attractive. In this review, the production of carbon nanomaterials from different plastic materials is comprehensively discussed by an extensive list of processes developed in the past years. We show how the reactor design, catalyst types, and pyrolysis/catalysis temperature affect carbon nanomaterials' quality. In terms of catalysts, the variety of metals and supports, metal particle size, metal-support interaction, and calcination temperatures have changed the carbon nanomaterials' morphology, geometrical shape, and yield, so these parameters should be fine-tuned to improve the carbon quality. Furthermore, the existing characterization techniques for carbon materials are summaried and the potential applications of the carbon materials are outlooked. Although some satisfactory progress has been achieved, many fundamental research topics and applications, such as the effect of impurities, large-scale carbon quality evaluation, and potential application scenarios, still require lots of future effort. The plastics-to-carbon materials technology is very open for further research and is considered a promising route for recycling plastics in a more economical and environmentally friendly manner.