Base Catalysed Hydrothermal Reformation of Kraft Lignin

Lignin comprises ca. 20 - 30 wt.% of the wood that is used in the pulp & paper industry and is a potentially viable renewable source of aromatic chemicals. Conventionally, lignin product streams from pulping are used as an energy source. With the introduction of new technologies at pulp mills (e.g. LignoBoost® or LignoForceTM), it is expected that the availability of lignin and particularly Kraft Lignin (KL) will increase in the future. Instead of using this bio-resource as energy carrier for fuelling the mills' processes, the lignin streams could be used as a platform from which to produce a number of chemicals and materials. In this context, a recently considered possibility is the usage of KL as a precursor for the production of carbon fibres. The high carbon content of KL (ca. 60%) makes it a promising candidate for this application, although its chemical structure / heterogeneity still implies a number of challenges regarding successful spinning, stabilisation, and carbonisation. Therefore, it is necessary to improve the properties of lignin (e.g. KL) for improved usage in the three aforementioned methods, ideally performed in an as easy to apply pre-process as possible. In this context, the focus of this thesis is upon the development of a process based on solvent extraction and a subsequent base catalysed reformation of technical softwood KL with the aim of increasing product thermal stability and carbon content whilst reducing the polydispersity (PDI).