The majority of ionic liquids for are not suitable for processing owing to their poor chemical instability – many are hydrolytically unstable, corrosive or both. However, ionic liquids such as 1-butyl-3-methylimidazolium methylsulfate and 1-butyl-3-methylimidazolium hydrogensulfate are promising ionic liquids for biomass deconstruction. Importantly, these ionic liquids don’t degrade into dangerous products, making them suitable for biomass processing.
Ionic liquids-based process engineering is still 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. The soft-SAFT approach has previously been successfully applied to ionic liquids with applications in CO2 capture. Following previous work, we represent the ionic liquids as Leonard-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.