Separation of CO2 from Methane Using Ionic Liquids

Abstract

When natural gas is produced along with the methane it carries several impurities such as Carbon dioxide (CO2) and Hydrogen sulphide (H2S). The CO2 can form dry ice and hydrates in the pipelines, causes corrosion in supply lines and decreases the calorific value of the gas. The presence of H2S can cause environmental and health hazards as well. Henceforth the natural gas is pretreated in order to separate the acid gases before the commercial use. Over the course of time several separation techniques have been developed and deployed for the separation of CO2 from methane such as Amine scrubbing with suitable amine solution. Membrane separation process is also being used for the separation of the CO2 from methane using the semi permeable membranes. Recent studies have depicted Ionic Liquids as another potential candidate for the CO2 separation due to their wide liquid range, high thermal stability and near zero volatility. Ionic Liquids are salts in liquid state at room temperature having melting point below 100 °C. They have high affinity for the CO2 due to quadrupole moment and physical absorption takes place due to the Vaan der Waals forces. The purpose of this research is to test CO2 solubility in the 1-butyl-3-methylimidazolium tetrafluoroborate [Bmim][BF] ionic liquids for the effective CO2 separation from methane, testing the solubility of CO2 at different pressure. Preparation and testing of CO2 solubility in [Bmim][BF4] ionic liquid based solvent systems. Comparative analysis of the absorption efficiency with the Amine scrubbing processes. Process simulation of the ionic liquid based process for performance and techno-economic evaluation and comparative analysis with conventional amine process using Aspen PLUS® simulator. This work also includes the economic analysis of ionic liquid based natural gas sweetening process.