revolPET®: An Innovative “Back-to-Monomer” Recycling Technology for the Open Loop Value Chain of PET and Polyester Composite Packaging and Textiles

Abstract

Nowadays there is a need for innovative solutions for composite materials in the packaging and textile sectors. These are formed by multilayer structures that improve technical performance however complicates recycling. Consequently, they are mostly sent to energy recovery or downgrade recycling processes. To avoid this, new recycling technologies are needed.The innovative “back-to-monomer” recycling technology “revolPET®” represents a solution for this challenge. In the process, the polyethylene terephthalate (PET) is selectively depolymerized to recover the monomers ethylene glycol (EG) and terephthalic acid (TA) for a new PET production. By an alkaline hydrolysis, the PET reacts continuously with a strong base in a twin-screw extruder. The average residence time in the extruder is less than one minute with a process yield up to 95%. Due to the mild depolymerization conditions, the other polymers remain chemically unchanged and can be easily separated. The produced monomers are regained in virgin quality and can achieve a 33% reduction on the greenhouse gases emissions if compared with the crude oil production route.In this contribution, the technology on a pilot scale as well as the results of the first scale-up investigations are presented and discussed with respect to technical maturity and environmental benefit.

Precipitation of Terephthalic Acid from Alkaline Solution: Influence of Temperature and Precipitation Acid

“…With this intention and economic aspects on heat integration, the depolymerization and precipitation should be continuously operated. 27,28 In conclusion, back-to-monomer recycling processes and their crystallization of terephthalic acid must be able to compete economically and qualitatively with virgin terephthalic acid production via the fossil production route. Therefore, for a successful industrial implementation, factors like the cost of reactants, quality of by-products, and operational costs as well as the necessary time and effort to yield the final monomers must be considered.…”

“…The influence of byproducts of a realistic depolymerized feed can be neglected since solid residues can be separated by filtration and soluble colored impurities can be removed by adsorptive processes. 27,28 However, in future industrial implementation of a TA precipitation process the influence of EG which is known to reduce aqueous solubility of DST at higher concentrations has to be considered. 29 Likewise, higher reactant concentrations of the PA and DST must be focused with regard to process water reduction.…”