Chemical recycling of post-consumer textile waste via continuous hydrothermal liquefaction and hydrotreatment for simultaneous monomer and hydrocarbons production

Abstract

Textile waste streams pose a significant sustainability challenge for industry, particularly due to the complex, mixed composition and the presence of various chemical additives, such as colorants, dyes and other finishing chemical additives. This study utilizes hydrothermal liquefaction (HTL) with aqueous phase (AP) recirculation to chemically recycle real mixed textile waste, resulting in an increase from an initial 5 wt% to 27 wt% oil in batch reactors due to water saturation and the partitioning of less polar compounds from the aqueous phase into the oil phase. Continuous processing with AP recirculation further enhances the HTL oil yields to 39 wt% and enables the recovery of 48 wt% of terephthalic acid (TPA) from the original polyesters. The chemical recycling of TPA via HTL has a similar range of energy intensity as its direct synthesis from crude sources. The resulting oil was hydrotreated, producing a fully deoxygenated hydrocarbon mixture rich in a nitrogen free naphtha fraction. However, the full denitrogenation was not achieved in the kerosene, gas oil and bottom residue fractions. This study demonstrates the technical feasibility and energy efficiency of chemical recycling of mixed textile waste using HTL.