(426d) Ionic Liquid Design and Sustainable Process Simulation for Decarbonization of Shale Gas and Gas Separations

Ionic liquids (ILs) have been receiving increasing attention as a potential decarbonization solvent as well as solvent for gas separations, which are usually energy intensive. However, the enormous number of potential ILs that can be synthesized makes it a challenging task to search for the best IL as a decarbonization solvent, for example, for CO2 removal from methane. Also, for gas separations, for example, gas purification processes, ILs can play a major role by replacing the extractive distillation column with a liquid-liquid extractive column, while the recovery column is replaced by an evaporator, thereby saving a lot of energy. The main question is what properties should the ionic liquids and solute (gas)-IL mixtures have to design the optimal separation process? If the IL properties can be matched, then the target process design would be obtained.

In this work, a systematic method is proposed to screen suitable ILs based on a collection of ILs (generated by Computer Aided Molecular Design and collected data); using the COSMO-RS (Conductor-like screening model for real solvents) model and available data in the database, a model for absorption mechanism as well as process simulation-design tools. Several IL properties related to gas absorption, such as the Henryâ??s constant, the viscosity, gas-solvent solubility data as well as toxicity of ILs are considered for evaluation of targeted decarbonization process and gas separation processes. Furthermore, process simulation is performed to evaluate the new IL-based decarbonization and gas separation technologies. Considering CO2 solubility, CO2/CH4 selectivity, gas solubility, gas/gas selectivities, viscosity and toxicity of ILs, several IL such as [Bmim][NTf2] has been found as a potential solvent from among more than 5000 ILs in the database. Based on reliable experimental data (available for only a fraction of the ILs present in the database), a rigorous thermodynamic model is established by comparing the simulation results with available experimental data. Different process flowsheet options obtained from targeted solvent behavior have been investigated to determine the best IL-based flowsheet. For the decarbonization process, compared with the well-known MDEA (methyldiethanolamine) process for CO2 capture, the single-stage and multi-stage process alternatives with IL reduce the total energy consumption by 42.8%, 66.04%, respectively. For selected gas separation, the potential for energy reduction is even higher â?? a reduction of more than 70% can be achieved. Net carbon emission as well as eco efficiency indicators are also evaluated to highlight the more sustainable and innovative aspects of the process designs.