Projekt 3 im Rahmen Center for Dynamic Systems (CDS) ZS/2023/12/182075: Transforming Waste into High-Value Products: Harnessing Lignin, Lignocellulose, and Black Liquor for Sustainable Chemicals and Polymer Innovations - Electrochemical transformation of black liquor to green hydrogen and lignin-derived functional components (Projektbereich 1, Teilprojekt 1.4)

Elektrochemische Oxidation von Schwarzlauge
Schwarzlauge, ein Abfallprodukt der Zellstoff- und Papierindustrie (ca. 50 Millionen Tonnen pro Jahr), stellt eine erhebliche Herausforderung für die Umwelt dar. Derzeit werden Lignin-Nebenprodukte und Schwarzlauge überwiegend durch energieintensive Verdampfung und anschließende Verbrennung verwertet. Lignin ist jedoch die reichhaltigste natürliche Quelle für aromatische Verbindungen und bietet daher eine nachhaltige Möglichkeit zur Herstellung aromatischer Chemikalien wie Vanillin, p-Hydroxybenzoesäure und Syringasäure. Dies eröffnet auch Wege zur Herstellung nachhaltiger Kunststoffvorläufer und -produkte unter Verwendung funktioneller Ligninpolymere und -oligomere wie Caprolactam. Die Integration der Ligninverwertung mit erneuerbaren Energiequellen wie Solar- und Windenergie bietet eine vielversprechende Strategie zur Erreichung der CO2-Neutralität. Ziel dieses Projekts ist die Entwicklung eines neuen elektrochemischen Depolymerisationsverfahrens zur Behandlung von Lignin bei Raumtemperatur und unter Umgebungsbedingungen. Es werden wertvolle Produkte wie Syringyl und Guaiacyl sowie Wasserstoff erwartet.

Project 3 within the Center for Dynamic Systems (CDS) ZS/2023/12/182075: Fractionation and valorization of black liquor and lignin (project area 1, subproject 1.4)

Electrochemical Oxidation of Black Liquor

Black liquor, a waste byproduct generated in the pulp and paper industries (approximately 50 million tons per year), poses significant environmental challenges. Currently, the predominant method for utilizing lignin side streams and black liquor involves incineration after energy-intensive evaporation. However, lignin, being the most abundant natural source of aromatic compounds, presents a sustainable opportunity for producing aromatic chemicals such as vanillin, p-hydroxybenzoic acid, and syringic acid. This also opens pathways for creating sustainable plastic precursors and products using functional lignin polymers and oligomers, like caprolactam. Integrating lignin conversion with renewable energy sources, such as solar and wind power, offers a promising strategy for achieving carbon neutrality. The aim of this project is to develop a new electrochemical depolymerization process for treating lignin, at room temperature and under ambient conditions. Valuable products are expected, like syringyl and guaiacyl as well as hydrogen.

Electrochemical depolymerization is a promising technique for treating lignin, as it can be conducted at room temperature and under ambient conditions. Currently, there are several publications on lignin electrochemical degradation, but limited work has been done on using black liquor as a lignin source. In this WP an electrochemical reactor for black liquor conversion will be developed, considering at first membrane-less design. Both direct lignin oxidation and oxidation mediated via reactive oxygen species (ROS) will be explored. Potential electrode materials include nickel, graphite, and boron-doped diamond (BDD). The initial characterization will utilize synthetic black liquor, modeled after the composition provided by our industry partner. To remove electrodeposited lignin products pulsed electrolysis conditions or sonoelectrochemical approaches (possible cooperation Prof. Ohl, OVGU) can be explored. Online gas chromatography (GC) will be employed to characterize product gases. The oxidation products of lignin will be identified in collaboration with WP2/4. Possible products include syringyl and guaiacyl on the anode side, and hydrogen on the cathode side. These products will be evaluated as precursors for synthesising caprolactam or caprolactam-like chemicals (WP6). To produce caprolactam, lignin-derived aromatic components must undergo dealkenylation, which will be addressed in conjunction with WP2. Furthermore, WP6 will explore the potential for creating new biodegradable and sustainable polymers based on lignin-derived aromatic compounds like vanillin, but also based on direct functionalization of lignin for cross-linking into lignin-derived polymers. In the subsequent stage, the pre-conditioning of real, industrial feeds will be considered.