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Abstract Title: Comprehensive chemical description of pyrolysis chars from low-density polyethylene LDPE by thermal analysis hyphenated to different mass spectrometric approaches
Abstract Type: Seminar
Session Choice: Analytical challenges in addressing new generation FuelFeedstocks and renewables
Presenter Name: Mr Lukas Friederici
Co-authors:Mr Eric Schneider
Dr Gatan Burnens
Dr Thorsten Streibel
Prof Pierre Giusti
Dr Christopher Rger
Prof Ralf Zimmermann
Company/Organisation: University of Rostock
Country: Germany

Abstract Information :

Introduction: In the last decades the production and demand of plastics has drastically increased, with severe environmental impact. Concerning climate change and the idea of a circular economy, waste incineration is not favored, and efficient recycling strategies are needed. Pyrolysis is one of the most promising approaches for the recycling of solid plastic waste SPW, generating a certain amount of solid residue besides liquid and gaseous products. In contrast to the gaseous and liquid products, which can be traced back to typical refining processes. The chemical nature of this char is not fully understood, but it holds the potential to be used in the field of material science e.g. batteries, catalysis, water purification or to generate further chemicals.rnAim: Provide a comprehensive chemical analysis of pyrolysis chars from low-density polyethylene waste LDPE by thermal analysis coupled with the different mass spectrometric techniques and to explore the value of this feedstock.rnMethods: In this study, thermal analysis was coupled to different mass spectrometry approaches. For detailed molecular description, selective and sensitive photoionization schemes were applied and flash-pyrolysis gas chromatography Pyr-GC with mass spectrometric detection was used as validation method. Thermogravimetry simultaneously hyphenated to high resolution mass spectrometry TG-HRMS and a non-heated gas phase mass spectrometer with electron ionisation TG-EI-QMS was applied. The char samples were generated in a pilot plant from unmixed SPW composed of LDPE at 410 C.rnResults: The thermal analysis of the char revealed a unique behaviour with four mass loss steps and the amount of char can be reduced by a factor of two, by a second pyrolysis. With the help of soft photoionization techniques, we were able to identify alkenes, dienes, and polycyclic aromatic hydrocarbons PAHs, which were emitted at elevated temperatures up to 500 C. Here, resonance-enhanced multiphoton ionization allows selectively addressing the aromatic constituents, whereas single-photon ionization covered a comprehensive chemical range. Interestingly, the common plastic UV-absorber benzophenone was identified with different methods at temperatures above 550 C. This delayed release is explained by the incorporation into the three-dimensional char network only decomposed at elevated temperatures. The fourth mass loss belongs to the release of incorporated carbon dioxide. Finally, high-resolution mass spectrometry allowed to unravel the complex pattern on the isobaric level and indications for a three-dimensional network composed of archipelago and island structural motifs were found, highlighting the not-fully graphitized and heterogeneous character of the chars.rnConclusion: A comprehensive set of thermal analysis mass spectrometric platforms enabled an in-depth chemical description of plastic pyrolysis char, valuable knowledge in reactor design and material science.rn