Energy-Efficient Chemical Recycling of Polyethylene Terephthalate via Water-Free Glycolysis Process Using Membrane...

Conventional chemical recycling of polyethylene terephthalate (PET) via glycolysis is hindered by the high energy cost of separating water and ethylene glycol (EG) via distillation. In this work, the energy-intensive EG-water separation step was excluded by implementing a water-free, membrane-based process for the production and purification of bis(2-hydroxyethyl) terephthalate (BHET) from PET glycolysis. The proposed approach is built upon three key innovations: (1) a micro-sized MgO/SiO₂ heterogeneous catalyst that enhances PET depolymerization efficiency, achieving a 95.1% BHET yield, (2) a water-free glycolysis process that reduces process complexity, and (3) an organic solvent nanofiltration-based purification and concentration strategy that selectively separates BHET while minimizing energy-intensive phase-change operations. A high overall BHET yield of 93.2% was achieved, enabled by a two-stage cascade concentration with over 99% yield. Compared to conventional distillation, the proposed process reduces energy consumption by 86%. Techno-economic analysis revealed a return on investment of 2.48 years for a production capacity of 1000 tons of BHET per day, highlighting its economic viability. By minimizing reliance on phase-change operations, this process presents a scalable and transformative solution for sustainable chemical recycling, serving as an important stepping stone to transform PET glycolysis from a batch to a continuous process.