Carbonisation of lignin in the presence of a eutectic salt mixture: Identifying the lignin properties that govern the characteristics of the resulting carbon material

Abstract

Numerous studies have explored the behaviour of various lignin types during carbonisation. Yet, misconceptions persist regarding the effects arising from both the source plant and production method of lignin. Lignin is often referenced merely by type, lacking detailed characterisation. Our research examines the properties of three lignin types, elucidates their behaviour during pyrolysis, and establishes the structure-property correlation and interaction of lignin with deep eutectic solvents. By combining several analytical techniques — including NMR, FTIR, XPS, TGA-MS for functional group detection, and HPLC, EA, and ICP for compositional analysis, alongside particle size distribution and SEC for morphology — we can conduct a thorough analysis that facilitates a meaningful comparison across lignin types. This approach allows for better control over the desired carbon properties. Furthermore, we demonstrate how modification with deep eutectic solvents enables the production of biochar from different lignin types, exhibiting properties conducive to large-scale, one-step sustainable production of biochar.