DiReC-IL · Computer Simulation of the Dissolution and Regeneration of Cellulose from Ionic Liquids

Computer Simulation of the Dissolution and Regeneration of Cellulose from Ionic Liquids

"The problem being addressed: Cellulose is the most abundant and also the most widely used organic material on Earth accounting for roughly 40 and 90% of the dry mass of wood and cotton, respectively. The separation of cellulose fibers from other plant materials is often achieved by applying strong, derivatizing chemicals (e.g. NaOH) in order to dissolve cellulose fibers, while keeping the polymeric structure of cellulose molecules intact. Cellulose-intensive industries (paper and textile) consume an ever-increasing amount of cellulose. In order to satisfy this increasing need in a sustainable way one needs to improve processing techniques allowing 1) to employ resources (e.g. wood waste) not yet used and 2) to develop new, green and less hazardous chemicals which also ensure the application of less hostile processing conditions, and thus reducing related costs. The recalcitrance of cellulose (its extraordinary resistance to mechanical and chemical impact) is rooted in its highly ordered pattern of H-bonds that hold cellulose fibers together. Ionic liquids (ILs) were found to be very efficient solvents for dissolving cellulose, presumably because of their efficacy in breaking those strong H-bonds and their somewhat amphiphilic character providing a particular solvation environment. The aim of this project is to provide new insight into the dissolution mechanism and to contribute in an indirect way to the development of better IL solvents. Importance for society: The development of more benign, potentially less dangerous solvents which, at the same time, also ensure better energy efficiency, and consequently more economical operation with lower carbon footprint are of crucial importance to improve sustainability of modern societies. These better, greener technologies would allow for the development of industries (in line with one of the major objectives of the European Union) based on more carbon-neutral, bio-degradable resources, such as cellulose. Overall objectives: The main objective of this project is to provide new insight into the dissolution mechanism of cellulose in the BMIM Cl ionic liquid by applying a bottom-up approach starting with understanding the dissolution mechanism of glucose, the monomer of cellulose in this ionic liquid (in comparison to the dissolution in water), and then gradually increasing the complexity of considered sugars. This would eventually allow us to extrapolate to the case of cellulose. Conclusions: -The ideal set of force fields for the dissolution study consists of the force field by Mondal et al (J. Phys. Chem. B, 2015, 119, 11041–11051), CHARMM36 for sugars, and TIP4P/2005 for water. -Cl ions form very strong H-bonds with the OH groups of sugars, sometimes even ""bidentate"" complexes. The breaking up of of H-bond between sugar molecules due to Cl ions happens on a much faster timescale than in water. -The number of still intact H-bonds to other sugar molecules together with the number of already formed ones with the solvent is a good measure for the study of the evolution of the dissolution process -In the case of larger sugar molecules, the change in conformation of glycosidic bonds is also an important indicator of the progress of the dissolution. -The cation acts as a H-donor to form H-bonds with the OH groups of sugars (though much weaker than Cl ions). They can effectively shield the hydrophobic side of the sugar molecules (in the axial directions)."

Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз