Metal-based Ionic Liquids For Efficient Separation Of Ammonia

Ammonia,emitted from industrial production,has caused serious environmental pollution and resources wasting.The traditional water scrubbing method has the limitations such as high energy consumption,waste of resources and secondary pollution.Ionic liquids(ILs)have characteristics of low melting point,wide liquid range,high solubility and tunable structure,which make them have a good prospect in the field of absorption and separation of ammonia.In order to further improve NH3 absorption properties of ILs,a series of metal-based ionic liquids(MILs)and their loaded materials were designed and synthesized.The absorption/adsorption capacity under different conditions,selectivity and cyclicity and the absorption/adsorption mechanism were studied,which provided the basic data of a new generation of new ILs for gas separation technology.The major work and results are as follows:A series of MILs were designed and prepared.Their structure were characterized by NMR,IR and elemental analysis and their physical properties including thermal decomposition temperature,melting point,density and viscosity were measured.The amount of NH3 absorbed by MILs at different temperatures and pressures were determined by gravimetric method.Compared with conventional ILs,it was found that the introduction of metal chloride anions can greatly increase the absorption capacity.[Bmim]2[NiCl4]and[Bmim]2[CuCl4]had the highest NH3 absorption capacity,which could be up to 0.195 gNH3·gIL-1(343.15 K,0.1 MPa)and 0.172 gNH3 gIL-1(303.15 K,0.1 MPa),respectvely.Through five cycles,it was found that[Bmim]2[SnC14]has very good reproducibility.Through IR analysis and quantitative calculation,it was found that complex reaction occurred between[Bmim]2[CuCl4]and NH3,while there was a strong hydrogen bonding effect between[Bmim]2[SnCl4]and NH3.In view of the limitation of the large viscosity of MILs,silica gel-supported MILs materials(SILs)were prepared by impregnation-evaporation method.The SILs were characterized by IR,BET and thennogravimetry.The adsorption properties of SILs on NH3 were investigated by gravimetric method.The effects of temperature,partial pressure and load amount on the adsorption properties were investigated.The results showed that the MILs impregnated on silica gel could increase its contact area with NH3 and increase the adsorption rate.It was found that impregnation of MILs could increase the adsorption capacity.The adsorption capacity could reach 99.53 mgNH3·gIL-1 when the MIL content was 50wt%(303.15 K,0.1 MPa).The increase of the adsorption capacity was mainly attributed to the chemical complexation and hydrogen bonding between MILs and NH3.This research provides a new research idea of technology development and industrial application in further dealing with NH3 pollution.