A well-known collision experiment can be carried out with an arrangement of several elastic balls suspended in a horizontal row. As we have shown in a previous article a necessary condition for the observed, simple behavior of this arrangement during collision is that the perturbation propagates throughout the system without dispersion. In the present paper, we show that the arrangement can be described by a series of spatially separated masspoints and springs of a special type: the exponent of the force law of the springs is 1.5 according to a theory of H. Hertz. It follows that the first collision sequence of such an experiment is not completely dispersion free. Indeed, slight dispersion during the first collision sequence creates the conditions for the total absence of dispersion in all the subsequent collisions.

Increased media coverage of plastic pollution in the environment and import bans on plastic waste in several countries have resulted in plastic waste becoming one of the most discussed waste streams in recent years. In the European Union (EU), only about one-third of the post-consumer plastic waste is recycled; the rest goes to energy recovery and landfilling in equal parts. In connection to the necessary increase in efforts to achieve the ambitious EU recycling targets, chemical recycling is currently receiving more and more attention. The assumption is that chemical recycling processes could open up new waste streams for recycling and generate valuable raw materials for the chemical industry. Although there exists no legal definition for chemical recycling, there is more or less agreement that it covers the conversion of plastic polymers into their monomers or chemical building blocks. Techniques such as gasification, pyrolysis and liquefaction as well as solvolysis can be used for chemical recycling. So far, only few large-scale plants for chemical recycling exist worldwide. This article presents the different processes by means of examples from (formerly) running installations and their suitability for plastics recycling is assessed. However, to date, only few chemical recycling plants are in continuous operation, and further scientific evidence for the ecological and economic benefits is still necessary for final evaluation.

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In a circular economy, processes such as the pyrolysis of polyolefin plastic waste must be established for naphtha cracker feedstock production. However, the composition of the plastic waste used has a strong influence on the conversion process and the heteroatom content, and thus on the quality of the pyrolysis oils. In this work, the influence of critical plastic components (e.g., polyamide 6) on the catalytic cracking of polyethylene (PE-HD) in a batch rotary kiln reactor was investigated and a cost-effective concept for integrating chemical recycling into a steam cracking plant was proposed.

The catalytic pyrolysis of lignites is a technical process whose development is complex and timeconsuming with the goal to maximize the yield of the desired low-volatile hydrocarbons of choice and to minimize the yield of solid residual products. Not every type of lignite is suitable for this process due to its particular chemical composition. In order to be able to predict which lignite specimen will be an especially promising raw material for the pyrolytic liberation of target products, the chemical classification by IR spectroscopic methods was investigated. MIR spectroscopy has been demonstrated to be a valuable tool to characterize the the molecular composition of lignites and to determine the concentrations of aliphatic and aromatic functional groups in lignite as well as alcoholic OH and other forms of bound oxygen. These data provide a comprehensive chemical characterization of the material and help to predict the composition of the chemical components liberated by catalytic decomposition. With a complementary NIR spectroscopic approach, a chemometric method has been developed with which the elemental composition of the lignites can be determined in a fast and pragmatic way leading to a prediction of the product range of a theoretical pyrolytic product range. Thus, this spectroscopic investigation is a toolbox that can answer the question if the commercial exploitation of catalytic pyrolysis of a lignite sample in question will make sense without preliminary conduction of long and time-consuming testing.

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Für die stoffliche Verwertung von Braunkohle sind in der Vergangenheit unterschiedliche Verfahren entwickelt worden. Eines davon ist die thermische Pyrolyse. In dieser Arbeit wird ein neuer Ansatz aufgezeigt, der den Einsatz von heterogenen Katalysatoren im direkten Kontakt mit der Einsatzkohle verfolgt. Dabei können aliphatische Bestandteile der Braunkohle gespalten und Olefine sowie Aromate erzeugt werden. Ein Katalysatorscreening zeigt, dass zeolithische Materialien für diesen Zweck geeignet sind. Diese können mit vergleichbaren Eigenschaften zur besseren Abtrennung von den Koksrückständen auf Trägermaterialien aufgebracht werden.

Chemical recycling offers the opportunity to foster the transition towards a circular economy for plastics as a complementary strategy for mechanical recycling. For the implementation of chemical recycling technologies, there are still significant challenges ahead that -besides the definition of binding legal frameworks -need for intensified research: knowledgebased methods for both the identification of suitable process technologies considering decentralized waste conditions and the design of conversion steps and downstream processing are strongly needed for process development and process evaluation.