Thermal stability and characterization of a tetramethylguanidine–imidazole ionic liquid for acid gas removal

The increasing need for efficient and sustainable technologies for acid gas removal has stimulated the development of alternative absorbents with enhanced chemical properties. In this work, the thermal stability and physicochemical properties of a tetramethylguanidine–imidazole ionic liquid (IL) were investigated, as this material emerges as a promising medium for reactive SO₂ capture applications. The assessment of thermal stability and physicochemical behavior is considered essential for the successful large-scale adoption of this emerging material. Thermal behavior was evaluated through calorimetric analyses performed on the individual reactants, the synthesized ionic liquid, and mixtures containing the IL and ethanol as synthesis solvent. The analysis enabled the determination of the main onset temperatures and relevant kinetic parameters. Particular attention was devoted to identifying potential thermal hazards and assessing the stability of the system under operating conditions relevant to gas absorption processes. In addition, the ionic liquid was characterized through measurements of viscosity, density, heat capacity, and electrical conductivity. Infrared (IR) spectroscopy was employed to confirm the successful synthesis of the ionic liquid and to investigate intermolecular interactions within the system. The obtained results contribute to the understanding of tetramethylguanidine-based ionic liquids and support their potential application in the scale-up of emerging SO₂ removal technologies.