Catalytic Solvent-based Recycling of Plastic Waste

Promovendus/a: Galahad O'Rourke

Promotor(en): Prof. dr. ir. Dirk De Vos

Plastic waste is one of today’s most urgent global problems, with over 380 million tons produced each year. Plastics are everywhere—used in packaging, construction, and countless everyday products—which has led to a mountain of waste that’s hard to manage. While traditional recycling helps a bit, only a small portion of plastic is actually recycled. Most of it ends up in landfills or is incinerated, which pollutes the environment, wastes resources, and releases greenhouse gases. Recently, chemical recycling has emerged as a promising solution, with the potential to turn plastic waste back into raw materials for new plastics or industrial chemicals. This method, called "closed-loop recycling," could pave the way for a circular plastic economy and make a real dent in the plastic waste crisis.

This PhD research focuses on developing advanced recycling technology that uses chemical and solvent-based methods to tackle two particularly challenging types of plastic waste. First, it targets multilayer packaging, which is difficult to recycle because it’s made of different types of plastics held together with strong adhesives. By selectively dissolving the adhesive, this new process separates the layers, allowing for efficient recycling of the plastics individually. Second, the research looks at recycling PVC, a common plastic in construction. Current PVC recycling methods are limited because PVC often contains toxic additives like lead and phthalates. To overcome this, the study developed two innovative catalytic systems that break down PVC, removing chlorine atoms and converting it into safer, reusable materials.

In one system, a special ionic liquid combined with a rhodium-based catalyst achieves 80% dechlorination of new PVC, producing a material similar to polyethylene. The second system, using zinc chloride and ruthenium, completely removes chlorine from used PVC waste. A unique solvent was also discovered that enhances the process, improving the recycling results.

The technologies from this research present groundbreaking methods to recycle difficult plastic types, potentially transforming waste into a valuable resource. This work opens up new possibilities for managing plastic waste more sustainably, pointing us toward a future where plastics can be fully recycled and reused.