| Ammonia（NH3）is a typical toxic and harmful air pollutant,and it is also an important chemical raw material in the fields of fertilizers and pharmaceuticals.It has important scientific and practical significance for its purification,separation and recovery.The traditional industry’s use of acid or water to absorb ammonia usually causes problems such as high pollution,high energy consumption,and strong corrosiveness.In recent years,eutectic solvents（DESs）have become a new hot spot in the field of gas separation research.Because they are easy to prepare,low cost and good absorption performance。Taking into account the lone electron pair in the NH3 molecule and based on the tunable structure of DESs,this paper relies on the principle of alkaline gas acid solvent trapping,and systematically regulates the acidity of each component of the deep eutectic solvent according to the characteristics of the weak alkalinity of ammonia.Designed a series of binary weakly acidic deep eutectic solvents to explore the strong absorption between ammonia gas,the details are as follows:Firstly,1-ethyl-3-methylimidazole chloride（[emim]Cl）is used as the hydrogen bond acceptor（HBA）to construct a series of weakly acidic deep eutectic solvents with different acidity hydrogen bond donors（HBDs）.The acidity of the hydrogen bond donor is regulated in The pKa value in DMSO ranges from 8.2-18.6.By characterizing different weakly acidic DESs,the adsorption and desorption properties of DESs for NH3 have been systematically studied,and the correlation with the acidification of HBDs has been studied.The solubilities of NH3 follow the sequence of[emim]Cl+Tetz（1:1）>[emim]Cl+Ben Triz（1:1）>[emim]Cl+Triz（1:1）>[emim]Cl+Si（1:1）>[emim]Cl+P h（1:1）>[emim]Cl+Ben Im（1:1）>[emim]Cl+Im（1:1）,which is nearly identical to the sequence of acidities for corresponding HBDs,this work has guiding significance for the development of NH3 capture technology.Secondly,a series of deep eutectic solvents（DESs）composed of ethylamine hydrochloride（EaCl）and glycerol（Gly）were designed,which can react strongly with NH3 by hydrogen bonding and lewis acid-base interaction by using the weak acidity of EaCl and multiple hydroxyl groups in Gly.The absorption of NH3 in EaCl+Gly mixture prepared at different temperatures and pressures was measured experimentally.The results show that the NH3 capacity of EaCl+Gly mixture is considerable,reaching the maximum value of 9.631 mol/kg at 298.2 K and 106.7 k Pa,which exceeds the NH3capacity of most absorbents.Finally,considering that the concentration of NH3 in the industrial stream is usually low（3～15%by volume）,a new type of DESs were prepared using ethylamine hydrochloride（EaCl）and phenol（PhOH）,both of which have a certain degree of weak acidity.The results show that the viscosity of EaCl+PhOH DESs are very low,only4.4～7.5 c P at 293.2 K,which is of great significance to its practical application in gas absorption;secondly,the absorption of NH3 in EaCl+PhOH DESs is very fast,and it starts to approach equilibrium in only 60 s,And show obvious chemical behavior;because EaCl and PhOH both show strong hydrogen-donating ability,we also deduced dual-site reaction equilibrium thermodynamic model;at the same time EaCl+PhOH DESs show quite high NH3 absorption capacity,especially under low pressure,where the absorption capacity reaches 4.795 mol/kg at 298.2 K and low pressure 8.4 k Pa,which has great application prospects in the capture of NH3 in industrial processes.The weakly acidic DESs designed and synthesized in this paper has low viscosity,low price and simple synthesis,and shows excellent performance in the field of NH3absorption and separation.Considering good reversibility,it is considered that this series of deep eutectic solvents has great application prospects in the capture of NH3 in industrial processes. |
