The Design And Synthesis Of Ionic Liquids-based Deep Eutectic Solvents And NH₃ Capacity Study

The environmental pollution and the waste of resources caused by directly releasing NH₃ to atmosphere.There are many disadvantages in traditional NH₃-containing gas separation and recovery process.For example,the water scrubbing and acid scrubbing has the shortcomings of high energy consumption and secondary pollution,respectively.Owing to the remarkable advantages of ionic liquids（ILs）,such as very low volatility and structure designability,more and more attention has been paid to ILs.However,most of the conventional and functionalized ILs possess complex synthesis process and relatively high viscosity,which limits the application of ILs in NH₃ and CO₂ separation.As an analog of ILs,deep eutectic solvents（DESs）has been widely regarded as excellent solvents in gas separation for their outstanding properties such as easy preparation,low viscosity and wide liquid range.Hence,the combination of solid or high viscosity ILs and molecular solvents to form novel IL-based solvents for NH₃absorption has significant meanings not only to overcome the above problem of kinetic absorbent performance but also expand the application of ILs in gas separation.The novel IL-based DESs were prepared by mixing solid protic ILs with polybasic alcohols,then the effect of the structure of IL on NH₃capacity,NH₃selectivity,NH₃absorption-desorption ability were investigated and the mechanism for NH₃ absorption were investigated by NMR and in-site FTIR spectra.Based on the selection of ILs,in order to evaluate the NH₃ capacity of novel IL（X）,the continue absorption-desorption experiments of dealing containing-NH₃tail also were carried out,and all of data above mentioned is critical for the recovery of containing-NH₃tail in industry.The main innovative work are as follows:1)The design and synthesis of protic ILs for highly efficient and reversible separation of NH₃.There kinds of solid protic ILs were synthesized by one step method,including imidazolium nitrate（[Im][NO₃]）methylimidazolium nitrate（[Mim][NO₃]）and1,2-dimethylimdazolium nitrate（[Mmim][NO₃]）.The structures of ILs were confirmed by NMR spectroscopy.Their thermodynamic properties such as decomposition temperatures and melting point as well as absorption-desorption cycle experiments were investigated.The highest NH₃ capacity 252 mg NH₃/g DES was possessed by[Im][NO₃].2)The design and synthesis of IL-based DESs for highly efficient and reversible separation of NH₃.The novel IL-based DESs have been produced by mixing the molecular solvent ethylene glycol（EG）as hydrogen-bond donors with the PILs as hydrogen-bond accepters,which present outstanding properties including wide liquid range and composites designability.The effect of the structure of ILs on NH₃ absorption performances were investigated,besides,NH₃capacity under different temperatures（from-20 to 80℃）and pressures（from 0.01 to 0.1 MPa）were also studied.The IL is dominance in absorption process and the ILs with double protic H possess higher NH₃capacity than single protic H,when the content of[Im][NO₃]in DES is 41wt%,[Im][NO₃]/EG exhibited highest NH₃ capacity up to 211 mg NH₃/g DES.NMR and In-situ FTIR spectra indicated that multiple hydrogen bonding interactions occurred in NH₃ absorption by the PIL-based DESs.3)The optimization experiments of IL continually deal the gas including NH₃ and CO₂.After 1000 h continue experiments,it is can be concluded the novel IL（X）owns outstanding NH₃selectivity.When it deals containing-NH₃ tail（NH₃:45～52 vol.%;CO₂:20～28 vol.%）,the NH₃ can mostly be absorbed so that the concentration of NH₃ cannot be monitored by gas chromatography in neat gas stream;and the concentration of NH₃in regeneration gas is achieved to 95 vol.%.