Liquefaction of lignin: Uncatalysed and catalysed ethanolysis

This thesis work had three main objectives: 1) the characterisation of the bioethanol-derived lignin mass, in comparison to other varieties of technical lignin, 2) explore the thermochemical route of liquefaction by ethanolysis of the lignin mass in order to produce a ‘biocrude’, lignin-ethanol energy-rich mixture, and 3) finally assess the potential of the lignin mass, and determine whether the thermochemical route chosen proved a viable option for valorisation of the studied material. The literature review offers insight into the diversity of technical lignin, the current state of lignin pretreatment processes, as well as the thermochemical processes by which depolymerisation of the lignin polymer can be achieved. The experimental work consists of two parts: the first being the characterisation of the lignin mass, and the second being the attempts at liquefaction by ethanolysis, the results and conclusions. The lignin mass was received by St1 Biofuels Oy, in the form of a ground and dried powder. Characterisation of the lignin mass was performed in laboratory with contemporary techniques and standards. The analytical methods used were carbohydrate and lignin determination, inorganic matter determination, methoxyl group determination, molar mass distribution, GC-MS chromatography, 13C NMR analysis and Fourier transformation infrared spectroscopy (FTIR). Elemental analysis was performed out-house. These methods allowed us to determine the composition of the Lignin Mass (LM) along with its characteristics. The aim of the ethanolysis autoclave runs was to depolymerise the Lignin Mass (LM) in ethanol, in order to achieve partial liquefaction. A total of 8 runs were included in this work, 6 of which were uncatalysed, 2 of which were catalysed by heterogeneous catalysts: 5%Ni/γ-Al2O3 and 5%Ru/γ-Al2O3 respectively. Mass balances were determined for each experimental run with further analysis of the products with above mentioned analytical methods: bio-oil, residual lignin and solid fractions. This work provided conclusions on the suitability of the Lignin Mass as a candidate for further refinement, as well as insight into the depolymerisation mechanisms