Development of an Aqueous Liquid–Solid Phase-Change System of Piperazine/2-Amino-2-methylpropanol/Water for Energy-Efficient CO2 Capture

This study introduces a novel aqueous liquid–solid phase-change absorbent comprising piperazine (PZ), 2-amino-2-methylpropanol (AMP), and water to mitigate the high regeneration energy penalties associated with conventional CO2 capture processes. Although PZ provides rapid absorption kinetics and high capacity, its highly soluble byproducts usually prevent solid formation. The strategic incorporation of sterically hindered AMP overcomes this issue by enabling controlled liquid–solid phase separation. Systematic optimization identified the composition denoted as P15A35H50 as the optimal sample, demonstrating exceptional absorption and desorption capacities of 3.76 mol·kg–1 and 4.80 mol·kg–1, respectively. During absorption, CO2 is concentrated into solid precipitates that can be separated and consist of stable PZ-AMP complexes. Consequently, regenerating only the CO2-rich solid phase eliminates solvent vaporization energy losses, significantly reducing the regeneration energy for desorption to 1.54 GJ·t–1 CO2, a value representing only 42.9% of that required by conventional aqueous PZ systems. Furthermore, the system exhibits delayed precipitation onset and maintains low viscosity, ensuring operational safety and efficient mass transfer. This study presents a highly efficient, low-energy solution that constitutes a promising advancement for industrial CO2 capture technologies.