Thermal and Thermophysical Properties of Anionic Amines and Their Aqueous Solutions for CO2 Capture in Confined Environments

Air revitalization for the International Space Station (ISS) has been identified by NASA as a mission critical need which requires improvement. The current method uses13X zeolite, a solid adsorbent, to adsorb carbon dioxide. While this is effective, the zeolite adsorbent produces dust that is unwelcome on the space station. Furthermore, the adsorbentis too sensitive to humidity in moderate temperature gas streams [1]. Aqueous solutions of ionic amines show promise as a safe and efficient solution, as they do not volatilize and are not water sensitive [2]. Specifically, anionic amines have the most potential because of the amine functional group’s ability to readily scrub CO2out of the air [3, 4]. There are several different anionic amine compounds the research group at South Alabama is analyzing that show promise for this application in confined environments. Different aqueous ionic amine solutions release different amounts of energy when they absorb CO2, which can be useful in producing the heat needed to regenerate the solution after absorption, but also will require more energy to remove to carbon dioxide. To remove the CO2after it is chemically absorbed, the solution is to be heated and the carbon dioxide will return into the gas phase[5]. Ionic amines tend to be very viscous, but water can be added so the solution will flow more easily. However, water has a high heat capacity and will require more energy to heat the solution during regeneration and cool afterward. These circumstances–heat of absorption, viscosity, and heat capacities of the solutions–require our research team to find data for several different conditions to be able to determine the best ionic solution for air revitalization. For this project, the team will not pursue the logistics of viscosity,however, it will need to determine the thermophysical properties of the solutions at different concentrations. The pure component thermophysical properties must also be known for these ionic amines to calculate the energetics of the reaction