The IMPRESS project continues to advance. This time we are going to give you a glimpse into our lignin research work through Master’s theses.

Chemical modification of biorefinery lignins and production of colloidal lignin particles (CLPs) offers a viable pathway for lignin valorisation  

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. Researchers from Aalto University have studied four samples of biorefinery lignins obtained through Dawn Technology™ to uncover potential applications of these untapped resources. Samples originated from a softwood (pine – SL) and a hardwood (aspen – HL) were received either as fresh wet chips after hydrolysis (SL1 and HL1) or as dry materials (SL2 and HL2). The researchers were able to overcome the challenges with the samples, such as drying of lignin in acidic conditions as well as the presence and co-extraction of extractives, and to produce water soluble colloidal lignin particles (CLPs). The CLPs were applied as emulsifiers in Pickering emulsions of olive oil/water, where –C12-derivatized HL1 showed the best performance for emulsion stabilization.

For more information please visit the Master's Thesis that was completed in August 2022 based on the results of this work: Yasmini Silva, ‘Biorefinery lignin: Structural characterization, modification and production of nano-particles for applications’.

New optimized method of preparation of spherical lignin nanoparticles from the Dawn process lignin has been developed  

Despite of its antioxidant, UV-shielding and antimicrobial properties, lignin is undervalued plant-based material most of which is burned as fuel. Limited use of crude lignin is caused by its heterogeneous structure, low solubility of most of industrial lignins in water. Preparation of spherical lignin nanoparticles with well-defined surface structure allows to overcome many limitations of crude lignin and opens up new application possibilities.

Lignin from the Dawn process had the same limitations but appeared quite challenging also for converting into nanoparticles. Nevertheless, researchers from Aalto University revealed which specific process conditions during isolation of Dawn process lignin that had a negative impact on lignin chemical structure and thus hindered converting lignin into lignin nanoparticles. This finding was made possible through effective communication and support from Avantium.

Obtained knowledge allowed to develop optimized method of preparation of spherical nanoparticles from the Dawn process lignin. Master's Thesis was completed in February 2022 based on the results of this work: Fengyang Wang, ‘Supramolecular Colloidal Assembly of Flow Hydrolysis Hardwood Lignin from Dawn Technology™ Process’.
 

Spherical lignin nanoparticles made of the Dawn process lignin. AFM 3D image.