Pyrolysis technology for plastic waste recycling: A state-of-the-art review

Discarded plastics can be converted to various fuels and chemicals to generate positive economic value instead of polluting the environment. In the past few years, pyrolysis has attracted much attention in the industrial and scientific communities as a promising versatile platform to convert plastic waste into valuable resources. However, it is still difficult to fine-tune an efficient and selective pyrolysis process to narrow the product distribution for a feasible commercial production. Furthermore, traditional plastic-to-fuels technology looks like another expensive way to burn fossil fuels, making no contribution to the plastic circular economy. By learning from the developed plastic-to-fuels technology, achieving the conversion of plastic waste into naphtha or plastic monomers that can be used for new plastic manufacturing in a closed-loop way is a more promising resource recovery pathway. However, there is no comprehensive review so far about achieving plastic waste recycling/upcycling by pyrolysis. This article will provide a critical review about the recovery pathways of plastic pyrolysis based on the various products (fuels, naphtha, hydrogen, and light olefins). It will overview the recent advances regarding plastic pyrolysis process and reactor design, introduce various recovery pathways based on the pyrolysis process, summarize process optimization and catalyst development, discuss the present challenges for plastic pyrolysis, highlight the importance and significance of creating a plastics’ circular economy, discuss the economic feasibility, the environmental impact, and outlook for future development for plastic pyrolysis. This review presents useful information to further develop and design an advanced pyrolysis process, with an improved efficiency, desirable product selectivity, and minimum environmental impacts. It is helpful to encourage more circular economy-oriented research aimed at converting waste plastics to naphtha and plastic monomers instead of simply producing fuels from the scientific communities of chemistry, energy, and the environment.