(243c) Strategies to Enhance Catalyst Stability for the Upcycling of Polyvinyl Chloride to Hydrocarbon Waxes Via Tandem Dechlorination and Catalytic Hydrogenation

The critical shortage of economical technologies to recycle waste polyvinyl chloride (PVC) plastics has led to the landfill of nearly all waste PVC. For this reason there is an urgent need to develop novel technologies for the upcycling of waste PVC streams to value added products. The commercialization of tandem dechlorination and catalytic hydrogenation of PVC waste to hydrocarbon waxes has shown promise as a process that can meet recycling demand. In this reaction, PVC in a water-amine mixture is completely dechlorinated with water acting as a Cl “sink” which prevents deactivation of the catalyst by Cl, while a Pt catalyst hydrogenates the resultant polyene to hydrocarbon waxes. For this process to be scalable the Pt catalyst must be virtually 100 % recyclable. However, the catalyst stability was found to be low in these hydrothermal reactions largely due to the activity of the water in the amine-water mixture. To address this issue, we found that a heterogeneous chloride sink, in lieu of utilizing deactivating high temperature water, is required to prevent poisoning of the catalyst active sites by Cl and to prevent restructuring of the catalyst support. Hydrotalcite adsorbents demonstrated feasibility as an effective Cl sink in lieu of water which enables catalyst recyclability > 90 % and product hydrocarbon wax yields of up to 80 % when a Pt:PVC ratio of 1:150 is utilized.

Ongoing experiments are focused on calibrating catalyst deactivation against deactivating species that are present in real PVC waste such as phthalates, metals, and other legacy additives. Current reaction experiments are utilizing real waste from PVC streams that are incredibly expensive to recycle with traditional technologies. These wastes include vinyl flooring, vinyl roofing, automotive shredder residue (ASR), and cable wire jacketing.