Chemical Recycling of PET: Pathways, Process Bottlenecks, and Optimization Strategies - A Review

Polyethylene terephthalate (PET) is one of the most produced plastics worldwide, yet less than 30% is effectively recycled, leading to significant environmental and economic challenges. This review critically evaluates major PET chemical recycling pathways hydrolysis, glycolysis, methanolysis, aminolysis, and enzymatic depolymerization focusing on reaction mechanisms, optimization strategies, and sustainability considerations. A structured literature survey (2010–2025) using Dimensions, Scopus, and Web of Science identified 95 relevant studies for comparative analysis. Results indicate that glycolysis provides the highest scalability with up to 95% bis(2-hydroxyethyl) terephthalate (BHET) yield, while hydrolysis offers >99% pure terephthalic acid (TPA) but requires high energy input. Methanolysis achieves >98% dimethyl terephthalate (DMT) purity under pressurized conditions, and enzymatic depolymerization operates at 30–70°C with approximately 85% selectivity, though limited by enzyme stability and cost. Hybrid chemo-enzymatic and AI-assisted approaches are emerging as promising solutions, potentially reducing energy demand by 20–30%. This review highlights that no single process fulfills all industrial criteria, emphasizing the need for catalyst innovation, reactor optimization, and integration of digital and biological strategies to achieve sustainable and economically viable PET recycling.