Preparation Of New Double-site Ionogel Depending On Mesoporous Silica And Their Synergetic Performance For Carbon Dioxide Capture

As people's awareness of environmental protection continues to increase,the country's emission standards for CO₂ and other pollutants in industrial flue gas have gradually been increased.Therefore,the development of a highly efficient technology for CO₂ capture and separation in flue gas is the main research focus on flue gas purification in the future.As a green solvent,ionic liquid is considered to be a new type of CO₂ adsorbent with competitive potential due to its unique properties.Aiming at the problems of high viscosity and high cost of ionic liquids,growing immobilized ionic liquids?ionogels?have been developed,and the pore structure of the support is one of the important factor for the adsorption performance of the iongel.Based on the tunable property of anion and cation as well as the structural characteristics of different supports,an ionic liquid[P₄₄₄₄][2-Op]with duble active sites and five kinds mesoporous silica support materials with different pore structures were designed and synthesized.?MSV50,MSV75,MSV100,SBA-15 and HSBA-15?.Combined with the advantages of both to obtain duble-site ionogel with different pore structure,and explore the influence mechanism on the immobilization of ionic liquid and the adsorption performance for CO₂ with the different pores structure of supports.The main research contents and conclusions of this paper are as follows:First,a novel duble-site functionalized ionic liquid?IL?[P₄₄₄₄][2-Op]was synthesized by using tetrabutyl phosphonium([P₄₄₄₄]⁺)as a cation and2-hydroxypyridine?2-Hp?as an anion.The physical property characterization results show that the viscosity of the ionic liquid is 202 mPa·s,the water content is 0.6%,and the thermal stability is maintained at 230°C.Due to the synergistic effect of the active sites"N"and"O",the adsorption amount of the ionic liquid reached 0.56 molCO₂/molIL at 50°C,and the adsorption time was about 90 min.The mesoporous silica supports with vesicle pore structure MSVw?MSV50,MSV75,MSV100?and columnar pore structure?SBA-15,HSBA-15?were prepared.The synthesized duble-active site ionic liquid was immobilized in the support by immersion-evaporation method to obtain ionogels MSVw-s,SBA-15-s and HSBA-15-s with different pore structures??s?is the mass percentage of immobilized for IL?.The structural characteristics and the CO₂adsorption properties of the ionogels were studied in this paper.The results showed that the ionogels MSVw-s and HSBA-15-s retained the pore structure of the support after the IL was immobilized,and the sample with good thermal stability was up to 420°C at a lower IL immobilization?2%?.The difference in thermal stability of the ionogel shows that the IL of different immobilization has different dispersion states in the pores.In addition to the immobilization of the IL,Its dispersing of in the pores depends on the pore characteristics?specific surface area,pore size and pore volume?of the support.IL with low immobilization can form monolayer distribution and increase CO₂ adsorption rate in small pore supports due to their strong nano-confinement effect.The high adsorption capacity and rate can be ascribed to its large pore structure,which not only offers more space for highly dispersed IL but also serves as necessary pathway for fast diffusion of guest molecule CO₂.The ionogel MSV100-10 with a large pore size has a CO₂adsorption capacity of 1.49 mmol/?g-ionogel?at 50°C and a partial pressure of0.15,the adsorption amount remains at the initial 95%after 10 adsorption cycles.Unlike the adsorption performance of the vesicle pore structure,the cylindrical pore structure of HSBA-15-5 has a CO₂ adsorption capacity of 0.69mmol/?g-ionogel?under simulated flue gas conditions.The results show that due to the different pore structure of the support,the IL has a lower immilization in the columnar channel under the same impregnation amount,and the agglomeration phenomenon in the channel due to the weak nanolimited affect.Thereby effecting the adsorption performance of CO₂.