Imidazolium-based Ionic Liquids Preparation And Ammonia Absorption Performance

The environmental pollution caused by ammonia?NH₃?is becoming more and more serious,and it is easy to react with SO_X and NO in the atmosphere to form ammonium salts.It is one of the main sources of secondary particles of haze,and the purification treatment of industrial ammonia-containing tail gas has received extensive attention.There are many shortcomings in traditional ammonia-containing gas separation and recovery process.For example,the water scrubbing has the problems of water consumption,cannot easily recover NH₃ and high energy consumption for regeneration,and the acid scrubbing easily corrode equipment and also cause secondary pollution.Ionic liquids?ILs?have great application prospects in the separation and recovery of NH₃,due to their extremely low vapor pressure,excellent thermal stability and adjustable structures.At present,there are many reports on ILs for NH₃ absorption,including conventional ILs,protic ILs,metal ILs,etc.However,considering the separation effectiveness,the preparation process and production cost of ILs,this paper synthesizes a series of ILs,and selected an ionic liquid absorbent suitable for industrial applications,and optimize the process conditions for its amplification and explore the NH₃ absorption performance.At the same time,three kinds of imidazolium-based protic ionic liquids?PILs?were used to support the activated carbon?AC?to prepare the supported materials,which is expected to be applied to the industrial NH₃ separation and recovery process.The main findings are as follows:?1?A series of imidazolium-based ILs were synthesized,including conventional imidazolium-based IL 1-butyl-3methylimidazolium nitrate?[Bmim][NO₃]?and protic ILs,suchasbutylimidazoliumnitrate?[Bim][NO₃]?,imidazolium bis?trifluoromethylsulfonyl?imide?[Im][NTf₂]?,1-methylimidazolium bis?trifluoromethylsulfonyl?imide?[1-Mim][NTf₂]?,2-methylimidazolium bis?trifluoromethylsulfonyl?imide?[2-Mim][NTf₂]?and optimized a new type of ionic liquid absorbent.The purities and structures of ILs were confirmed by Nuclear Magnetic Resonance?NMR?and Fourier Transform Infrared?FTIR?spectroscopy,and the results indicated that the ILs synthesized are the target ILs.?2?The NH₃ absorption/adsorption capacities of several imidazolium-based ILs were investigated.The new IL?X?suitable for industrial NH₃ absorption process was selected after NH₃ absorption/adsorption performance comparisons,and the preparation process of the new IL?X?was optimized.The effects of raw material concentration,water content,temperature and pressure on the NH₃ absorption capacity of the new IL?X?were investigated.The selectivity of IL?X?to NH₃/CO₂was investigated,and found that the selectivity was as high as 107.6.The cycle regeneration performance of IL?X?prepared by amplification was investigated.The continuous absorption-desorption evaluation experiment of IL?X?was carried out and the results show that IL?X?prepared by amplification exhibits great NH₃absorption performance and recyclability after five cycles.?3?Since IL?X?was subjected to a continuous absorption-desorption experiment for 130 h,the NH₃ concentration of the ammonia-containing gas was reduced from14,000 ppm to 2000 ppm.In order to further reduce the NH₃ concentration of ammonia-containing tail gas,it is considered that three PILs with higher NH₃adsorption capacity were supported onto AC with larger specific surface area to prepare PILs supported AC materials for the low-concentration ammonia-containing tail gas adsorption process.The NH₃ adsorption capacity and recyclability of the supported materials were investigated.The effects of adsorption temperature,pressure and loading on the NH₃ adsorption capacity of supported materials were investigated.The regeneration performance of the supported materials was investigated,and the breakthrough time of the five regeneration experiments was between 50-60 min.The results showed that the adsorption properties of the supported materials are good and can be recycled.