(676g) Towards Green Bioprocessing: Ionic Liquids for Biomass Deconstruction

The sustainable production of both biofuels and chemicals depends largely on the cost effective access to cellulose. Current best-practice methods for biomass deconstruction are largely derived from the pulp and paper industry, and are energy intensive and require the use of large quantities of organic solvents. As such, these processes are capital and energy intensive. As an alternative, ionic liquids-based processes provide a promising near-term option for the digestion of lingocellulosic biomass[1].  

Unfortunately, the majority of ionic liquids for which data are available are not themselves suitable for processing owing to their poor chemical instability – many of them are hydrolytically unstable, corrosive or both.  However, other ionic liquids such as 1-butyl-3-methylimidazolium methylsulfate ([C4C1im][C1SO4]) and 1-butyl-3-methylimidazolium hydrogensulfate ([C4C1im][HSO4]) are promising ionic liquids for biomass deconstruction.  They act by reducing the crystallinity of the cellulose fibrils, rendering them open to enzymatic attack. Importantly, these ionic liquids don’t degrade into dangerous products, making them suitable for biomass processing[2].

Ionic liquids-based process engineering is still very much in its infancy. One important limiting factor is the limited availability of thermophysical property data for ionic liquids. Thus, physically based methods for the prediction of thermophysical properties relevant to process engineering are required. One such method is the soft-SAFT equation of state[3]. The soft-SAFT approach has previously been successfully applied to ionic liquids with applications in CO₂ capture[4]^,5. Following previous work, we represent the ionic liquids as associating Lennard-Jones chains. This model represents the ion pairs (anion plus cation) as a single chain molecule with the usual SAFT-type association sites used to describe the short-ranged anisotropic interactions. All molecular parameters were obtained by fitting to available density-temperature data.

In this contribution, we present new soft-SAFT models for a range of ionic liquids which are considered suitable for bioprocessing applications, and consider how these molecular-scale models may be used in an integrated fashion with process scale models for the design, analysis and optimisation of bioprocesses.