Fraunhofer Cluster of Excellence Circular Plastics Economy CCPENew approaches in the purification of pyrolysis oils from chemical recycling
Adsorption and hydrogenation processes specially adapted to pyrolysis oils are required for mixed waste from plastics. The Fraunhofer CCPE has extensive equipment for the distillation, hydrogenation and testing of catalysts and adsorbents. It develops new processes for the optimal purification of pyrolysis oils in terms of quality and yield.
In order to achieve the EU's ambitious targets for the circular economy of plastics, chemical recycling must be able to recover plastic waste that is difficult or impossible to recycle mechanically. The biggest challenge here is that pyrolysis oils from chemical recycling must match the specifications of industrial downstream processes such as steam cracking if they are to be used at a high level. So far, these qualities have not usually been achieved, as the concentrations of nitrogen, oxygen and sulphur, among other things, exceed the maximum values required in the industry. Petrochemical plants are also generally not designed for other undesirable elements such as halogens (chlorine, bromine), iron, calcium, phosphorus, mercury or lead. Pyrolysis oils from waste containing plastics have therefore only been used as "drop-ins" to date. Therefore, there is an overall high demand for treatment and purification processes.
Especially for mixed plastic waste and composite materials or other contaminated fractions, adsorption and hydrogenation processes specially adapted to pyrolysis oils are required. Corresponding catalysts and adsorbents are already available, but their industrial use is not yet established. One challenge is to reliably remove the varying concentrations of interfering elements depending on the source material. This requires selective and robust adsorbents and catalysts in conjunction with the appropriate process parameters.
The Fraunhofer UMSICHT, Sulzbach-Rosenberg branch, is part of the CCPE and is intensively involved in the processing of pyrolysis oils. It has extensive equipment for distillation (up to 3 liters / hour continuously in a vacuum), hydrogenation (up to 30 liters / hour) as well as for testing catalysts and adsorbents. Using an innovative combination of process control and catalyst, the concentration of heteroatoms in pyrolysis oils from challenging material streams such as electronic waste, mixed plastics or shredder fractions, for example, has been reduced to such an extent that the product meets industry specifications.