Upcycling of polyvinyl chloride into polyalphaolefin lubricants.

Abstract

Polyvinyl chloride (PVC) is a thermoplastic used ubiquitously in households and industry owing to its light weight, mechanical strength, durability, low cost and ultraviolet and fire resistance^1,2. With a production volume of about 60 million tonnes annually², post-consumer and post-industrial PVC waste pose marked environmental challenges, such as leaching chlorohydrocarbons and additives, which contaminate groundwater and soil^1-4. To address the formidable challenge of recycling PVC and achieving carbon circularity, valorization into high-value products is essential to mitigate the associated costs and offer high financial incentives for reusing plastic waste^5-14. Here we report a method for upcycling PVC into high-value lubricants with controllable viscosities. Using AlCl₃ at a mild temperature of 70 °C, PVC undergoes dechlorination, alkylation and chain scission, producing vinyl-derived polyalphaolefins (vPAO). PVC serves as an effective template for the alkylation of α-olefins of various chain lengths, producing vPAO with limited short branches in the backbone without the need for metallocene catalysts essential to current PAO technology. The PVC-derived lubricants exhibit tunable molar masses, kinematic viscosities at 100 °C (KV₁₀₀ ≈ 14.9-26.3 centistokes), a low coefficient of friction (COF ≈ 0.08-0.15) and a high viscosity index (VI up to 130). This work highlights an economical approach to using PVC as a low-cost feedstock to synthesize high-value lubricants with superior tribological properties, meeting the demand for sustainability in both the plastic and lubricant industries.