Enhanced CO₂ gasification of polyethylene terephthalate using a two-stage gasification process to produce CO-rich and tar-deficient syngas

This study demonstrates that a two-stage gasification process consisting of a fluidized bed gasifier followed by a tar-cracking reactor packed with activated carbon enables stable and efficient CO₂ gasification of polyethylene terephthalate. Conventional fluidized-bed CO₂ gasification typically suffers from low CO₂ conversion due to limited gas–solid residence time and the inherently low reactivity of CO₂. In contrast, the present two-stage configuration significantly enhances CO₂ utilization by first fixing polyethylene terephthalate-derived tar on activated carbon and subsequently promoting its reaction with CO₂, thereby intensifying the Boudouard reaction. Under 100 vol% CO₂, the system achieved outstanding performance, producing CO-rich syngas with CO concentrations up to 80 vol% and CO yields of 1.03 kg per kg of dry feed, while simultaneously reducing char formation. The carbon utilization efficiency reached 57–64 %, indicating that a substantial portion of supplied CO₂ was successfully converted into syngas carbon. Moreover, when the tar-cracking reactor temperature exceeded 800 °C, the condensed tar yield decreased to 3–7 g per kg of dry feed, confirming that this configuration effectively mitigates tar-related issues that have traditionally limited CO₂ plastic gasification. These findings show that the two-stage process overcomes the intrinsic limitations of CO₂ fluidized-bed gasification and offers a practical route for simultaneous polyethylene terephthalate recycling and CO₂ utilization. The significant improvement in CO₂-to-CO conversion further highlights the potential of CO₂ gasification as a promising method for producing high-purity CO while contributing to carbon circularity.