ICRC 2024 - Session 6

Prof. Dr. Xin Tu
University of Liverpool

Dr. Gert Homm, Fraunhofer IWKS

Dr. Marc Widenmeyer, Technische Universität Darmstadt 

Insightfully understanding the process of volatiles from plastic depolymerization entering from the exterior into internal structure of catalyst favors to rationalize the catalyst design in scale-up principles. Herein, catalytic degradation of plastic wastes with fluid catalytic cracking catalyst (FCC) was investigated in-depth. The structural evolution of catalyst on overall scope, including the topology of heterogeneous pore systems and spatial distribution of zeolite was probed by X-ray nano-CT. The results showed that FCC enhanced the transformation of C16-C30 chains to C9-centered monocyclic aromatics. The nano-CT analysis of FCCs illustrated remarkable loss of exterior porosity after reaction, particularly at the depth of ~16.5 μm from the outmost layer. While the interior pores were marginally affected, indicating large hydrocarbons incapable of engaging with active sites to full advantage, which preferably occupied large-size pores (>385 nm) of external surface.The performance of Li-ion batteries is determined by the architecture and properties of electrodes formed during manufacturing, particularly in the drying process when solvent is removed and the electrode structure is formed. A comparison of temperature effects on both NMC622-based cathodes (PVDF-based binder) and graphite-based anodes (water-based binder) dried at RT, 60, 80, 100 and 120 °C has been undertaken. X-ray computed tomography showed that NMC622 particles concentrated at the surface of the cathode coating except when dried at 60 °C. However, anodes showed similar graphite distributions at all temperatures. Focused-ion beam scanning electrode microscopy and energy-dispersive X-ray spectroscopy suggested that the F-rich binder distribution was largely insensitive to temperature for cathodes. To date there is limited discussion of these processes in the literature due to the limitation of existing in-situ metrology. Here, ultrasound acoustic measurements are demonstrated as a promising tool to monitor the physical evolution of the electrode coating in-situ. A possible application of using this technique is to adjust the drying rates based upon the ultrasound readings at different drying stages to speed up the drying time. These findings prove this measurement can be used as a cost-effective and simple tool to provide characteristic diagnostics of the electrode, which can be applied in large scale coating manufacturing.

The presentation will place chemical recycling in the existing waste hierarchy and reflect the recent discussion on the topic in the European context. It provides an overview of the different technological options and focuses on the pyrolytic conversion and gasification processes for mixed plastic waste. The general process principles, products and process conditions will be discussed and recent development directions will be analysed and typical concepts will be presented. A market overview of technologies, plant sizes, announced projects and partnerships will be complemented by examples of current commercial implementation and research activities.

The pressing need for effective recycling strategies within the wind energy industry has motivated us to investigate the behavior of various solvents and catalysts used in the solvolysis of carbon fiber reinforced plastics. Our research has revealed that methanesulfonic acid presents itself as an intriguing alternative to conventional solvents and catalytic Bronsted and Lewis acids. In our study, we applied two layers of carbon fibers (CFs) that were impregnated with amine-based epoxy using a vacuum-assisted resin infusion (VARI) process. The findings unequivocally demonstrated that methanesulfonic acid (MSA) stands as the most efficient catalytic solvent for the solvolysis of carbon fiber reinforced plastics (CFRPs), outperforming other commonly investigated acids. Furthermore, the recycled products exhibited commendable properties for both the matrix and the fiber, aligning comparably with virgin materials.

Increasing the amount of recycled plastic in our current manufacturing processes of polymer materials, such as polypropylene (PP) and polyethylene (PE), requires the exploration of new methods of chemical recycling of plastic waste. In this lecture, I will discuss three different chemical routes, namely the catalytic pyrolysis, chemical oxidation, and photo-oxidation-solvolysis chemistry of polyolefins.The first system of interest is the so-called fluid catalytic cracking (FCC) system, which currently converts crude oil fractions into transportation fuels, such as gasoline, and chemical building blocks, such as propylene. We have explored in the past years the use of various FCC systems, containing for example various metal ions, for the catalytic conversion of polypropylene into aromatics. It was found that not only acidity and metal content are of importance, but also the accessibility thereby showing that the overall performance of catalyst materials is determined by the unique balance between active sites and the accessibility or wetting of these active sites. Various spectroscopy and microscopy techniques have revealed the different chemical species involved in the reaction and deactivation mechanism of the catalytic pyrolysis of polypropylene and polyethylene, thereby comparing FCC materials with zeolites and mesoporous materials.Another system of interest is the oxidation of polyethylene into dicarboxylic acids, thereby comparing the effect of the type of oxidant, namely NO and O2. It was found that mixtures of dicarboxylic acids could be formed, which subsequently can be transformed into polyamides in the presence of amines. The addition of transition metal oxides and its effect on the catalytic performance will also be explored.A third system of interest is the photo-oxidation of plastic waste, in particular low-density polyethylene, thereby combining photocatalysis by a.o. titania with solvolysis. The result of this research is the formation of carboxylic acids, and other oxidation products, such as carbon dioxide, next to microplastics.The lecture ends with some reflections on the different possibilities of chemical and catalytic technologies to turn plastic waste into valuable products.

Materials used as the active layers of organic optoelectronic devices such as organic LEDs and organic solar cells are almost exclusively based on petrochemical starting materials. Their production still relies on relatively energy-intensive processes and often uses hazardeous and environmentally harmful reagents. Efforts aimed at the development of recyclable materials for these purposes are scarce. Furan derivatives can be obtained from the platform chemical furfural and thus are derived from lignocellulosic biomass. Furan rings are also biodegradable. For optoelectronic applications, furan-based materials offer several advantageous features such as exceptionally bright luminescence, good solubility, and effective pi-electron delocalization along their backbone. The reason why they have received relatively little consideration for such applications in the past is their moderate oxidative stability in air, especially in the presence of incident light. Herein, it is demonstrated that furan-containing optoelectronic materials are effectively stabilized through the combination with electron-deficient trivalent boron. In addition, this provides the materials with special features enabling their use for certain sensory applications and as stimuli-responsive materials. Innovative synthetic concepts will also be presented. Our group has developed an environmentally benign organocatalytic polymerization method, which avoids the use of toxic reagents such as organotin compounds previously used in organboron chemistry.