PhD defence: Anders Jensen
Anders Jensen defends his thesis,
Liquefaction of Biorefinery Lignin for Fuel Production
Professor Claus Felby
Professor Joseph Bozell, University of Tennessee
Professor Lasse Rosendahl, Aalborg University
Professor Ole John Nielsen (chair), Department of Chemistry, UCPH
Lignocellulosic biorefineries can be an important piece of the puzzle in fighting climate change. Present, biorefineries that produce ethanol from lignocellulose are challenged in working on market terms as the two product streams ethanol and lignin are low value products. The aim of this project has been to increase the value of the lignin stream. Recent regulations on shipping exhaust gasses in coastal waters dictate lower sulfur emissions which require ships to use low sulfur fuels for propulsion. This opens or expands a very large market for low sulfur fuels because a shift from traditional sulfur containing bunker fuel is needed. The lignin stream from lignocellulosic biorefineries could provide a source for the production of sulfur free fuels and this is what has been explored and demonstrated in this PhD project.
The chemical reactions taking place in lignin during hydrothermal pretreatment of wheat straw has been investigated by size exclusion chromatography and NMR spectroscopy. It was found that contrary to literature reports on hydrothermal pretreatment of hardwood the lignin in wheat straw depolymerizes. The argument for this depolymerization is that unlike hardwood lignin, grass lignin (e.g. wheat straw) contains tricin that can act as a polymerization inhibitor during pretreatment.
A solvolysis reaction involving ethanol and hydrothermally pretreated wheat straw lignin from the pilot scale biorefinery Inbicon in Denmark was tested at lab scale. Here it was found that in a batch reactor it is possible to produce a biooil from lignin. Yields up to 85 % were achieved at very low lignin loadings in ethanol. At higher loadings of 10-40 % lignin ethanol, oil yields between 40 and 20 % were achieved. Further the oil was found to be more deoxygenated at higher loadings. The effect of increased reaction time was found to be beneficial for oil yields but also caused an increase in solvent consumption and so there is a trade-off where a compromise has to be found in the event of an up scaled reaction. The reactions that cause solvent consumption during the process were identified and this knowledge might help to lower solvent consumption in future processing. From these batch reactor results it was found that solvolysis of hydrothermally pretreated lignin in a primary alcohol holds a large potential and two patent applications were filed and two manuscripts for publication of the results were prepared and is presented here.
The thesis is available for inspection at the PhD administration office, 03.1.353, at Øster Voldgade 10, 1350 CPH K