The University of Utrecht has chosen a Coperion STS 25 Mc11 twin screw extruder for a chemical plastics recycling research project. A research group headed by Assistant Professor Dr. Ina Vollmer will undertake comprehensive investigations of the mechanical-chemical conversion of mixed plastic waste using catalysts.
Coperion
At the K trade show (8-15 October 2025, Dusseldorf, Germany) Coperion, together with Herbold Meckesheim, will present their entire repertoire of technology for plastics recycling at Booth 9B34 in Hall 9 as well as in the Open Area in pavilion FGCE07.
Efficient conversion of plastic waste using catalysts
Alongside proven solutions for mechanical plastics recycling, Coperion realises plants for chemical plastics recycling. This process converts plastic waste back into high-quality raw materials, potentially making unlimited recycling possible. So far, the process is energy intensive and does not always result in high-quality products. Using catalysts could play an important role in the continued improvement of end product quality and process efficiency.
The University of Utrecht’s research project is dedicated to precisely this challenge. The STS 25 Mc11 twin screw extruder, being installed there to carry out the experiments, processes waste plastic, shredded or compacted, with two co-rotating screws in a closed process section. Together, intensive dispersion and high shear introduce a great deal of mechanical energy into the material. The plastic is energy-efficiently melted – an advantage that is particularly important in chemical recycling. Moreover, the extruder achieves a very high mixing effect with its twin screws. The catalysts being implemented in this research project are distributed absolutely homogeneously throughout the plastic melt and can fully develop their intended effect.
In conventional pyrolytic processes, the hot plastic melt is prepared within the twin screw extruder for the next step in chemical processing: pyrolysis. There, in an oxygen-free environment, the plastic is broken down to its chemical building blocks. The temperature of the pyrolysis can be lowered thanks to the efficient use of catalysts, as Vollmer’s team has shown in preliminary work.
Said Dr. Ina Vollmer regarding her research assignment: “Using the extruder, we can achieve an efficient use of the catalyst. Still, our vision is to allow pyrolysis to take place even in the extruder. We can achieve this by exploiting the mechanical-chemical reaction that occurs within the twin screw extruder, and specifically convert the polymer at lower temperatures than have previously been necessary for pyrolysis. Mixing with high shear in the extruder has a very positive effect on the use of catalysts. We are convinced that we can direct the chemical recycling process more precisely using lower temperatures, and this will lead to purer products while at the same time having the potential to revolutionise the chemical plastics recycling process sequence and save energy. “
Should the use of catalysts in the chemical recycling process prove its worth, the results of this research will easily be transferable to larger throughput ranges.