Experimental solubility and thermodynamic modeling of nitric oxide absorption in low-viscosity DBU-based deep eutectic solvents

Developing absorbents with highly efficient nitric oxide (NO) absorption and desorption is very important for flue gas denitrification process. Toward this end, a class of DBU-based deep eutectic solvents (DESs) containing alkanones or azoles as functional HBDs for the capture of NO were synthesized in this work, with viscosities of only 7.71–45.57 mPa·s at 303.2 K. Solubilities of NO in these DESs were determined at temperatures from 303.2 to 333.2 K and pressures from zero to 1 bar. It was found that the absorbing abilities of the DESs increased with the increasing HBDs’ alkalinity. Impressively, these DBU-based DESs had remarkable larger absorption capacities than those reported DESs in the literature. According to the solubility curves of NO, chemical absorption was thought to occur accompanying with the physical one in the systems. Therefore, the reaction equilibrium thermodynamic model (RETM) was applied to model the experimental NO solubilities. The corresponding thermodynamic parameters for each system, such as the reaction equilibrium constant, Henry’s law constant, and the enthalpy change were also obtained to assess the NO absorption process in these DESs.