Biorefinery lignin: Structural characterization, modification and production of nano-particles for applications
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Journal Title
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Volume Title
Kemian tekniikan korkeakoulu |
Master's thesis
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Authors
Date
2022-08-23
Department
Major/Subject
Materials and Biopolymers
Mcode
Degree programme
Master's Programme in Biological and Chemical Engineering for a Sustainable Bioeconomy
Language
en
Pages
46
Series
Abstract
As the second most abundant vascular plant biopolymer after cellulose, lignin is an important raw material for future biobased chemicals and materials. Due to its complex structure, the full utilization of the widely available technical lignins streams from biomass processing still remains a challenge. In this study, four samples of biorefinery lignins obtained through Dawn Technology™, which uses concentrated HCl for biomass fractionation, were studied to uncover potential applications of these untapped resources. Samples originated from a softwood (pine – SL) and a hardwood (aspen – HL), and were received either as fresh wet chips after hydrolysis (SL1 and HL1) or as dry materials (SL2 and HL2). The soluble fractions were obtained using ultrasound-assisted solvent fractionation with THF, and characterized using attenuated total reflectance Fourier transform infrared spectroscopy (ATR–FTIR), liquid state 1D and 2D nuclear magnetic resonance (1H and 1H—13C HSQC NMR), gel permeation chromatography (GPC) and thermogravimetric analysis (TGA). Structural characterization indicated that drying of lignin in acidic conditions leads to condensed structures. In the SL sample, the presence and co-extraction of extractives greatly hindered the determination of the fractionation yield. HL1 was chemically modified using either a short chain (–C2) or a long chain (–C12) fatty acid. Water-soluble colloidal dispersions of lignin nanoparticles (CLPs) could be obtained from all samples, except for the –C2-derivatized HL1, using solvent shifting method with water as anti-solvent, thus offering an alternative for diverse potential applications of lignin-based materials. The –C12-derivatized HL1 allowed the production of CLP with light colour, which widens the potential use of CLP in applications where the dark colour of lignin could pose an issue. The CLPs were applied as surfactants in Pickering emulsions of olive oil/water, where –C12-derivatized HL1 showed the best performance for emulsion stabilization. Chemical modification of biorefinery lignins and production of CLPs thereof offers therefore a viable pathway for lignin valorisation. Further work should aim to increase the yield of soluble lignin by optimization of solvent choice and fractionation condi-tions, and to assess applications for the insoluble fraction, such as composites for packaging applications.Description
Supervisor
Österberg, MonikaThesis advisor
Nousiainen, PaulaLukk, Tiit
Keywords
technical lignins, acid hydrolysis, valorisation, colloidal lignin particles, pickering emulsions