One main ongoing theme in the group has been the development of cellulose-dissolving ionic liquids, as a platform for a wide range of applications: IONCELL process (dry-jet wet-spinning of cellulose from ionic liquids), wood gluing, biomass fractionation, 3D printing of true cellulose solutions, regeneration to novel morphologies etc... The group has strong links to the pulp and paper industry in Finland, so has exellent perspective on the scientific requirements to meet industry demands, including the value of research in society and for the preservation of our environment.
As such, focus in the group has been on the development of novel processes and processing methods, with strong emphasis on materials science and analytics. The research does not focus on the development of low molecular-weight chemicals or fuels from biomass but rather on preservation of molecular weight and development of the morphologies possible through chemistry and novel regeneration methods.
Since the discovery that ionic liquids (molten salts that melt below 100 oC) can dissolve cellulose, in 2002 by Swatlowski et al., the main focus for research in the Kilpeläinen group has been on the development of ionic liquids as a platform for biomass processing in general. The initial focus was on dissolution of residual (condensed) lignin for NMR analysis but there was clear potential for dissolution of whole biomass (wood) itself. One key application from this is logically fractionation of biomass. However, the major drawback of this approach is in the recovery of the expensive ionic liquid component, as losses are not offset by the low value of the obtained fractions. Therefore, the clear challange was to improve the recyclability of the ionic liquids but also to focus on the simpler processing schemes, with minimal components to recycle.
In 2011 we developed the concept of 'distillable acid-base conjugate ionic liquids' (Angewandte Chemie 2011, 50, 6301), designed for cellulose processing. These were shown to be highly effective at cellulose dissolution and were distillable using simple distillation apparatus. The concept was developed further, by combining different superbases with organoacids (ChemSusChem 2013, 6, 2161). This yielded a series of ionic liquids that were exclusively effective in dry-jet wet-spinning of their cellulose solutions: the IONCELL Process (collaboration with Aalto University - Sixta Group in the Department of Bioproducts and Biosystems).
Figure: Crystal structures for 5 distillable cellulose-dissolving ionic liquids, effective for dry-jet wet-spinning of cellulose: Left - [TMG-H][O2CEt] (DOI: doi.org/10.1002/anie.201100274), Right - a) [HMPA-H][O2CEt], b) [DBU-H][O2CEt], c) [DBN-H][OAc], d) [mTBD-H][OAc]. (DOI: doi.org/10.1002/cssc.201300143)
With the success of the IONCELL process (currently beginning the piloting stage) and the development of further in-house concepts (e.g. wood gluing and 3D printing of cellulose), new low-cost sources of ionic liquids needed to be developed. Therefore, much of the focus of the group is in the further expansion of this class of ionic liquids, with emphasis on the development of scalable chemistries and novel properties to expand the application scope. Currently, a development spin-off company has been formed (Liuotin Group Oy) concerning the development of the technnology side.
Currently, there is plenty of room for further development and talented students to join the research team.
Much of our efforts have focused on the IONCELL process, which has a clear environmental element to it, due to the demand to find replacement feedstocks for cotton. In this regard, using Finnish chemical pulp, also brings relevance to the Finnish bioeconomy. The following is a small overview by Aalto University on the impact of the IONCELL process:
Further applications that we have been developing are........
The Kilpeläinen group has a strong history of the development and application of advanced spectroscopic methods for biopolymer characterisation.
Lignin chemistry has been a historical field for the Laboratory, with dibenzodioxocins (disputed branch point in lignin) being discovered in the lab (Tetrahedron Letters 1995, 1, 169):
Dibenzodioxocin core structure.
Development of NMR methods and for improving our analytical accuracy is also an important feature of the research. For example, 'Quantitative 2D HSQC (Q-HSQC) via suppression of J-dependence of polarization transfer in NMR spectroscopy: Application to wood lignin' was published in as J. Am. Chem. Soc. 2003, 125, 14 and continues the theme of analysis of complex biopolymers.
Q-HSQC Pulse Sequence (DOI: 10.1021/ja029035k)