负载型氨基酸离子液体的制备及其对二氧化碳的吸附性能

采用浸渍蒸发法将四甲基铵甘氨酸(N1111]Gly])和四甲基铵赖氨酸(N1111]Lys])两种离子液体分别负载到硅胶(SG)表面,利用EA、TGA、BET和FT-IR等技术对所得到的吸附剂进行表征,考察了离子液体种类、离子液体负载量和温度等条件对其CO_2吸附性能的影响。结果表明,离子液体成功负载到硅胶表面,所制得的负载型氨基酸离子液体对二氧化碳具有良好的吸附性能。在所考察的温度范围(303.15-323.15 K)内,温度越高,平衡吸附量越小;在负载量为10%-60%,随着负载量的增加,平衡吸附量先增加后减小。对于N1111]Gly]/SG,当负载量为22.4%(质量分数)、吸附温度为30℃、压力为0.1 M Pa时,二氧化碳的平衡吸附量可达到41 mg/g(相对于1 mol AAILs吸附0.62 mol CO_2),而且,吸附20 min即可达到平衡吸附量的90%。吸附剂在循环使用六次之后,其结构与性能均保持良好。

Preparation of silica gel supported amino acid ionic liquids and their performance capacity towards carbon dioxide

Two amino acid ionic liquids (AAILs), viz., tetramethyl ammonium glycinate (N₁₁₁₁]Gly]) and tetramethyl ammonium lysine (N₁₁₁₁]Lys]) were supported on porous silica gel through impregnation evaporation method and used as the adsorbents for carbon dioxide. They were characterized by elemental analysis (EA), thermogravimetric analysis (TGA), nitrogen physisorption and Fourier transform infrared (FT-IR) spectroscopy; the effects of AAIL type, loading and temperature on their adsorption capacity towards carbon dioxide were investigated. The results illustrate that AAILs are successfully immobilized into the porous silica gel and the supported sorbents exhibit excellent performance towards carbon dioxide, i.e. fast adsorption rate and high capacity. At 303.15-323.15 K, the adsorption capacity reduces with the increase of temperature, whereas there is a optimal loading of ionic liquids to get highest adsorption capacity towards carbon dioxide. Under 30 ℃ and 0.1 MPa, the N₁₁₁₁]Gly]/SG adsorbent with a N₁₁₁₁]Gly] loading of 22.4% exhibits the highest CO₂ capture capacity, i.e. 41 mg/g, equivalent to 0.62 mol CO₂ per mol AAILs; moreover, 90% of the equilibrium adsorption amount can be achieved in 20 min. Furthermore, no obvious decrease in the adsorption capacity is observed after recycling for six times.