Continuous-Flow Vapor-Phase Methanolysis in a Fixed-Bed Enables PET Recycling with In Situ Decolorization and Purification

Traditional PET methanolysis often suffers from high solvent consumption and complicated downstream purification, particularly when processing colored or contaminated polyester waste. Herein, we report a continuous-flow vapor-phase methanolysis approach using a fixed-bed reactor combined with catalyst-pretreated PET for the depolymerization of waste polyester materials. In this process, methanol vapor continuously passes through the reactor and transports volatile depolymerization products out of the reaction zone during the reaction. Under optimized conditions, the system achieved up to 90% dimethyl terephthalate (DMT) yield, while the condensed products exhibited a combined DMT/MHET purity of approximately 99%. In addition, colored PET feedstocks underwent effective in-situ decolorization during vapor-phase methanolysis, with decolorization efficiencies exceeding 90%. ICP analysis further demonstrated substantially reduced metal contamination in the recovered products compared to conventional liquid-phase methanolysis. These results suggest that continuous vapor-phase methanolysis enables simultaneous PET depolymerization and partial purification within a single-process configuration, providing experimental insights into the treatment and upgrading of colored and contaminated polyester wastes.