Deep Eutectic Solvents For Multiple Sites Reversible Chemical Capture Of Ammonia

Ammonia（NH₃）is one of the important basic chemical raw materials.The development of other industries such as the pharmaceutical industry,food industry and basic chemical industry cannot be separated from the major support of the ammonia industry.Ammonia plays an irreplaceable role in global economic development.Modern ammonia synthesis technology relies on the Haber-Bosch process to use N₂and H₂ to apply catalysts under high temperature and high pressure to synthesize NH₃.During the process of ammonia synthesis,3%-6%of ammonia still escapes mixed with other gases,which not only causes ammonia resources was wasted,but poses a serious threat to the atmosphere.For example,part of PM2.5 is formed by ammonia and acid pollutants in the exhaust gas.At present,the process method for ammonia in the exhaust gas of the synthetic ammonia are water absorption method and chemical absorption method.Both methods can efficiently remove ammonia.However,the water absorption method consumes a lot of water,and the formed ammonia water cannot be desorpted and separated,lead to waste of ammonia;chemical absorption method converts gaseous ammonia into solid-phase ammonium salt,and ammonia gas cannot be recovered.According to industrial economic requirements and green environmental protection,it is of prospective significance to develop a green solvent that can efficiently absorb and separate ammonia and can recycle ammonia.As ionic liquids（ILs）analogs,deep eutectic solvents（DESs）not only possess the structural designability of ILs,non-volatile and wide liquid path,but also have unique acid-base adjustment functions,which have potential application value in the field of gas separation.In this work,a series of weakly acidic DESs were prepared,which showed high solubility and separation ability for ammonia separation.The specific research contents of this paper are as follows:1.1-ethyl-3-methylimidazole chloride（[Emim]Cl）was used as hydrogen bond acceptor and combined with hydrogen bond donors phenol（Ph OH）,resorcinol（Res）and phloroglucinol（Phl）,respectively,to construct a series of phenol-bsaed DESs.The physicochemical properties of phenol-based DESs were systematically determined,and the flowability was evaluated in terms of density and viscosity.In addition,the absorption performance,desorption performance and NH₃/CO₂ absorption and separation performance of phenol-based DESs were systematically measured.It was found that phenol-based DESs had high solubility for NH₃ and good reversibility.The lower CO₂ absorption capacity indicates its have excellent NH₃/CO₂ absorption and separation performance.Finally,the interaction mechanism between NH₃ and phenol-based DESs was analyzed by means of ¹H NMR and FTIR spectroscopy,and the intrinsic mechanism of NH₃ absorption in phenol-based DESs was verified at the molecular level by means of quantum chemical calculations.2.Using ethylamine hydrochloride（Ea Cl）as hydrogen bond acceptor,Res and phl as hydrogen bond donors to synthesis a new type of phenol-based DESs with multiple weak acid sites.Firstly,the physicochemical properties（density,viscosity and melting point,etc.）of the prepared DESs were systematically determined,and then the NH₃ absorption properties of the DESs with different components,molar ratios and different temperatures were systematically measured.The results show that the prepared DESs can chemically absorbed NH₃ and NH₃ has high solubility,for example,the solubility of NH₃ reaches 9.00 mol/kg at 313.2 K and 102.1 k Pa,especially the solubility of NH₃ at low pressure（4.7 k Pa）can reach 3.73 mol/kg.Five absorption-desorption experiments demonstrate that the absorption of NH₃ is highly reversible.The absorption experiment of NH₃/N₂/H₂ mixture gas proved that DESs has high selectivity to NH₃.Theoretical calculations and spectroscopic characterization confirmed that the phenolic hydroxyl group plays a key role in the absorption of NH₃,and the DESs reacts with NH₃ through weak acid-base interaction.3.In this text,a class of metal-based DESs composed of Ea Cl,metal chlorides（Sn Cl₂,Zn Cl₂,Fe Cl₃ and Co Cl₂）and glycerol（Gly）was designed and synthesized.The physical and chemical properties and NH₃ absorption properties of metal-based DESs were systematically measured,and it was found that the solubility of NH₃ in metal-based DESs was very high,which can reach up to 10.24 mol/kg at 298.2 K and 6.8 k Pa.Results of multiple coordination and hydrogen-bonding interactions between the metal-based DESs and NH₃.The absorption of NH₃ in metal-based DESs also showed excellent reversibility,as well as high separation selectivity for NH₃.It is also found that the coordination numbers（CNs）of metal ions have a great influence on the viscosity and NH₃ solubility of the prepared metal-based DESs.Finally,the NH₃absorption mechanism in metal-based DESs was verified by FTIR spectroscopy,quantum chemical calculations and molecular dynamics simulations.