Synthesis Of Imidazolium-based Functional Absorbents And Its Application In SO₂ Capture

Sulfer dioxide（SO₂）which mainly comes from the combustion of fossil fuels is the primary cause of acid rain and haze.It has brought serious harms to the atmosphere and human health.At present,the traditional desulfurization technology used in chemical industry have some obvious disadvantages such as lots of by-products and the secondary pollution.Imidazolium-based functional absorbents show excellent desulfurization properties,we designed the muiti-site aqueous mixed absorbent and imidazolium-based deep eutectic solvent for SO₂ capture process.In this work,we have designed and prepared a new type of imidazole derivative:tris（2-（1-H-imidazole-1-y1）ethyl）amine（TIA）and mixed with water to form the mixed absorbents.The structure of TIA was characterized by spectra characterization and the absorbents showed high stability and low viscosity,which is beneficial to the mass transfer.The absorption experiment indicated that TIA/A（0.2:1）could absorb2.09 mol SO₂ per mol absorbent at low SO₂ concentration（2 k Pa）.With the increasing of TIA mass fraction,the total molar absorption capacity of SO₂ increased clearly.The desorption experiment was carried out at 80 ^oC and the desorption efficiency reached more than 99%within 1 h.The SO₂ absorption performance of the absorbents remained unchanged after 5 cycles,which suggested the absorbents has well recycling performance.The absorption mechanism between TIA/A（0.3:1）and SO₂ was analyzed by FTIR and NMR and the multi-site of TIA is the main reason for the high SO₂ absorption capacity.The relevant thermodynamic parameters were calculated by g PROMS to evaluate the reversibility of the absorption process.On the basis of the above,In order to further simplify the synthetic steps and improve the SO₂ absorption capacity under low partial pressure,12 kinds of deep eutectic solvents（DESs）based on imidazole derivatives were designed.The viscosity of the DESs were determined,and the absorption capacity of SO₂,as well as the influence of temperature,partial pressure of SO₂ and impurities in flue gas on the desulfurization performance of the DESs were investigated.Results showed that the SO₂ absorption capacities by DESs were significantly affected by the alkalinity of the hydrogen bond donor（HBDs）,and the DESs with 1-Butyl-3-methylimidalium chloride（Bmim Cl）as hydrogen bond acceptor（HBAs）could efficiently absorb SO₂.Bmim Cl:4CH₃-Im（1:2）could absorb 1.42 and 0.244 g _SO2/g _DES at 101.3 and 2 k Pa SO₂partial pressure,respectively,which were higher than most reports to date under this condition.The total absorption capacity decreased less than 8%when adding 10 wt%water to the Bmim Cl:4CH₃-Im（1:2）,and the SO₂/CO₂ selectivity of it was 38,which had great potential for flue gas desulfurization.FTIR and NMR analysis showed that the synergistic effect of HBDs and HBAs on SO₂ resulted in the high SO₂ capture performance.In total,we have studied the comprehensive performance of imidazolium-based mixed solution and DESs for SO₂ absorption process.The chemical reaction mechanism were discussed through experimental results and spectrogram analysis,which provided data support and new ideas for further design of efficient and green absorbent for acid gas separation.