Efficient absorption and thermodynamic modeling of nitric oxide by low viscous DBU-based N-heterocyclic deep eutectic solvents

Abstract

• The DBU-based N-heterocyclic DESs exhibited low viscosity of 10.02 mPa·s at 293.2 K. • The solubility of NO in the DBU-based N-heterocyclic DESs could reach up to 5.10 mol·kg −1 at 293.2 K and 1 bar. • RETM was designed to correlate the NO experimental solubility to obtain the thermodynamic parameters. • Absorption mechanism was verified that there was a chemical interaction between NO and the N-heterocyclic compounds. A series of low viscous deep eutectic solvents composed of 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) and N-heterocyclic compounds were designed and synthesized as NO trapping agents. These DESs exhibited low viscosity of 10.02 mPa·s and excellent NO absorption capacity up to ∼ 5.10 mol·kg −1 at 293.2 K and atmospheric pressure. The N-heterocyclic compounds were found to play a dominant role in the absorption, and the absorption behavior could thus be adjusted by the molar ratio of DBU to N-heterocyclic compounds. With the assumption of complex formation between NO and DESs, the reaction equilibrium thermodynamic model (RETM) was developed to correlate the experimental solubilities of NO. The thermodynamic parameters, such as the equilibrium constant K , the Henry’s constant H and the enthalpy change Δ H , were thus calculated to evaluate the absorption process. In addition, through a combination of the experimental absorption capacities, the RETM modeling results and the spectroscopic investigations, it was proposed that the absorption of NO in the DBU-based N-heterocyclic DESs was governed by the chemical interaction between NO and the N atom on the N-heterocyclic compounds with the reaction stoichiometry of 1:1.