Thermochemical Conversion of Plastic Waste into Fuels, Chemicals, and Value‐Added Materials: A Critical Review and Outlooks

Abstract

Plastic waste is an emerging environmental issue for our society. Critical action to tackle this problem is to upcycle plastic waste as valuable feedstock. Thermochemical conversion of plastic waste has received growing attention. Although thermochemical conversion is promising for handling mixed plastic waste, it typically occurs at high temperatures (300–800 °C). Catalysts can play a critical role in improving the energy efficiency of thermochemical conversion, promoting targeted reactions, and improving product selectivity. This Review aims to summarize the state‐of‐the‐art of catalytic thermochemical conversions of various types of plastic waste. First, general trends and recent development of catalytic thermochemical conversions including pyrolysis, gasification, hydrothermal processes, and chemolysis of plastic waste into fuels, chemicals, and value‐added materials were reviewed. Second, the status quo for the commercial implementation of thermochemical conversion of plastic waste was summarized. Finally, the current challenges and future perspectives of catalytic thermochemical conversion of plastic waste including the design of sustainable and robust catalysts were discussed.

Towards high-quality petrochemical feedstocks from mixed plastic packaging waste via advanced recycling: The past, present and future

“…Catalytic pyrolysis of plastic waste as a means to steer the composition of the produced pyrolysis oils is a promising technique to further improve the quality of the products as extensively described by Miandad et al [122][123][124]. Often used catalysts are zeolites and acidic solids [125][126][127][128][129][130]. A disadvantage of catalysts for the pyrolysis of end-of-life plastics is the high content of feedstock contaminants which may lead to a rapid deactivation of the used catalysts [32,33,128,131].…”

Hydrogen/Syngas Production from Different Types of Waste Plastics Using a Sacrificial Tire Char Catalyst via Pyrolysis–Catalytic Steam Reforming

“…There has been much research into the production of hydrogen from waste plastics involving thermochemical routes, including pyrolysis and gasification, and several different process configurations have been investigated and recently reviewed. − A successful two-stage pyrolysis–catalytic steam reforming process for the production of hydrogen from waste plastics has been developed and investigated by several different research groups. − The pyrolysis–catalytic reforming process involves initial pyrolysis of the plastics in the first stage to produce a wide range of volatile hydrocarbons, which are subsequently catalytically steam-reformed in the second stage. The two stages are usually separate reactors to aid independent process control of the reaction parameters to optimize both the pyrolysis and reforming stages .…”

Processing Plastic Wastes into Value-Added Carbon Adsorbents by Sulfur-Based Solvothermal Synthesis

“…New approaches are therefore urgently needed for the efficient conversion of plastic wastes into carbon materials with high yields and porosity. Recent technologies mainly focus on the following: (1) depolymerizing polymers into corresponding monomers or oligomers (or their derivatives) and then converting monomers or oligomers (or derivatives) into high-value chemicals; − (2) degrading polymer wastes into platform small molecules such as CO/H 2 , CH 4 , formic acid, and methanol, and then these reactive molecules are further transformed into high-value chemicals; ,− (3) based on the activation and fracture of specific chemical bonds, plastic polymer wastes are directly transformed. ,− In fact, those processes significantly contribute to this field, while the plastic recycling method by earth-abundant materials or industrial byproducts is still pursued by scientists …”