Pyrolysis of Polyethylene Terephthalate: Process Features and Composition of Reaction Products

The need for polyethylene terephthalate recycling is associated with the formation of significant amount of its waste, which should be reprocessed due to the growth of polymer production and consumption of plastic products used in light, chemical, medical industries, in mechanical engineering and instrument making. The main share of polyethylene terephthalate (PET) recycling processes is chemical methods through which various monomers are generated. After purification and modification of these monomers, valuable petrochemical raw materials can be yielded. The review describes the principles and mechanisms of polyethylene terephthalate degradation upon pyrolysis. The influence of the heating rate during pyrolysis (fast, slow), type of raw material (pure polymer, polymer waste), additives (modifiers, stabilizers, fire retardants), type of reactor in the process (horizontal, vertical, fixed bed reactor, fluidized bed reactor, conical tip reactor, rotating dc arc plasma reactor) is considered, as well as the effect of processing conditions such as temperature, amount of raw material, pressure, atmosphere, and presence of catalyst on the quantitative and qualitative composition of oxygen-containing compounds formed in the gas fraction, pyrolysis oil, and semi-coke. The influence of additives of various polymers in a mixture with polyethylene terephthalate on the formation of products (gas fraction, pyrolysis oil, and semi-coke), additives of plant biomass, and food waste is demonstrated. The effect of microwave radiation on the polyethylene terephthalate pyrolysis is considered.