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.
Aqueous amine-based CO2 capture is considered as the most mature and applicable CO2 capture method for post-combustion. With the CO2 capture process running for a long time, the degradation of aqueous amine-based is inevitable, and the degradation products are numerous and complicated. Therefore, the performance evaluation of aqueous amine solutions containing degradation products is crucial in both guiding the selective removal of degradation products and maintaining or reducing of the solution cyclic utilization rate. Unfortunately, a simple and effective way to increase the economic feasibility of the CO2 capture process after accumulated degradation products remains absent, and little attention has been paid to the real effect of degradation products on the CO2 capture performance in aqueous amine solutions. In this work, we propose a simple method to evaluate the performance and regeneration energy of aqueous monoethanolamine (MEA) solutions accumulating single degradation products based on the fast-bubbling reactor. Using this method, it is possible to quickly determine the key degradation products that affect the performance of aqueous MEA solutions so as to achieving clearer optimization, more direct purification, and a reduced solution cyclic utilization rate.
Four deep eutectic solvents (DESs) based on 1,1,3,3-tetramethylguanidine (TMG) and N-heterocycles (succinimide, 2-pyrrolidinone, 2-oxazolidone, N -methylurea) were prepared and assessed for NO capture. At 313.2 K and 1 bar, the viscosities of TMG/succinimide (TMG-Succ) and TMG/2-pyrrolidinone (TMG-Pyrr) were measured as 49.23 mPa·s and 2.85 mPa·s, respectively, while their corresponding nitric oxide (NO) uptake capacities reached 1.62 Mol·kg −1 and 1.10 Mol·kg −1 under identical conditions. Spectroscopic analysis confirmed chemisorption in TMG-Succ versus physical dissolution in TMG-Pyrr. Thermodynamic fits yielded the absorption enthalpy ΔH = −16.94 kJ·Mol −1 for TMG-Succ and − 70.1 kJ·Mol −1 for TMG-Pyrr DES. In addition, the absorption capacities of both DESs remained almost unchanged during the 10 cycles of absorption-desorption experiments, highlighting their low-viscosity, high-capacity, and energy-efficient reversible NO capture performance
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