功能型离子液体吸收电厂烟气CO2的研究进展

CO2是目前排放量最大的温室气体,利用离子液体固定CO2已经成为CO2减排的重点研究方向之一。介绍了近几年来各种离子液体吸收CO2的研究历程以及研究成果,对比各种离子液体吸收性能的差异,并着重介绍了功能型离子液体捕获CO2的特点及其应用,突出其在CO2固定方面的诸多优势,并对离子液体的吸收机理进行了讨论,同时探讨离子液体在电厂烟气CO2处理过程中所面临的问题。     

离子液体吸收CO2的研究进展

CO2的捕集、分离与利用已成为人类共同关心的重要课题。工业上,通常使用传统的有机胺水溶液或热钾碱溶液等脱除CO2。有机胺具有蒸气压,易产生挥发性有机物(VOCs)对环境造成污染;热钾碱溶液等脱除CO2需要较高操作温度因而能耗较高,生产过程经济性有待改善。离子液体具有几乎无蒸气压、热稳定性、结构可设计性等独特优点,在CO2分离领域的巨大应用潜力已成共识。本文结合课题组近期的研究工作,就国内外离子液体吸收CO2的主要研究成果进行综述。     

Gemini胺功能离子液体吸收CO2的研究

受亲水有机胺与CO2进行化学反应的启发,将胺功能基团能引入到咪唑环上,合成含胺功能基团的离子液体.本研究以四个亚甲基为连接基,合成含胺功能基团的Gemini咪唑离子液体1,4一二(溴化3-乙胺基咪唑)丁烷,所合成的物质经红外、核磁共振氢谱表征确为目标产物.进行了简单的吸收实验,其对CO2的吸收比物理吸收高很多,可与CO...     

离子液体支撑液膜的CO2/CH4分离性能

由于离子液体对CO₂具有较好的溶解选择性,离子液体支撑液膜分离CO₂越来越受到关注。比较了含3种不同阴离子的常规离子液体([bmim][BF₄]、[bmim][PF₆]、[bmim][Tf₂N])作为支撑液膜的液膜相分离CO₂/CH₄的性能,考察了咪唑环上烷基链长对离子液体支撑液膜性能的影响。考虑向离子液体中引入胺基和羧基等亲CO₂基团,制备了1-丁基-3-甲基咪唑丙氨酸离子液体([bmim][β-Ala]),考察了 [bmim][β-Ala]支撑液膜分离CO₂/CH₄的性能,并对在CO₂渗透测试前后的支撑液膜进行了FT-IR分析,发现氨基酸离子液体中的-NH₂和CO₂的较强作用以及该离子液体的高黏性影响了CO₂的透过性,使[Bmim][β-Ala]支撑液膜的CO₂透过率低。     

离子液体支撑液膜分离CO2的研究进展

总结了离子液体支撑液膜分离CO2的研究进展,简要分析了气体在离子液体支撑液膜中的传质机理;介绍了离子液体支撑液膜的制备方法及影响离子液体支撑液膜稳定性的因素;指出了今后用于分离CO2的离子液体支撑液膜的发展方向。     

氨基酸离子液体-MDEA混合水溶液的CO2吸收性能

为改善N-甲基二乙醇胺(MDEA)水溶液对CO₂气体的吸收性能,选择了四甲基铵甘氨酸(［N₁₁₁₁］［Gly］)、四乙基铵甘氨酸(［N₂₂₂₂］［Gly］)、四甲基铵赖氨酸(［N₁₁₁₁］［Lys］)、四乙基铵赖氨酸(［N₂₂₂₂］［Lys］)4种功能性离子液体作为活化剂与其复配组成新型CO₂吸收剂。用恒定容积法考察了总质量分数为30%的混合溶液吸收CO₂的性能,分析了离子液体在水溶液中与MDEA通过质子传递相互促进吸收CO₂的机理。实验结果显示离子液体能够显著提高MDEA水溶液吸收CO₂的速率,且吸收速率随着添加量的增加而提高。在本文所用的几种混合吸收剂中,阴离子为赖氨酸的离子液体混合吸收剂具有较高的吸收负荷;而［N₁₁₁₁］［Gly］-MDEA混合溶液对CO₂的初期吸收速率最快,同时［N_1111^］［Gly］-MDEA混合吸收剂的再生效率高于其他离子液体混合吸收剂,达到98%。     

相变离子液体体系吸收分离CO2的研究现状及展望

全球工业化的迅速发展及人口增长使得化石燃料消耗不断增加,导致二氧化碳(CO₂)排放量逐年递增,引发全球化气候问题。醇胺吸收法目前在工业CO₂捕集应用最广泛,主要以单乙醇胺、甲基二乙醇胺等水溶液为吸收剂,存在溶剂损耗大、再生能耗高等问题,开发高效低能耗的新型吸收剂是实现CO₂大规模捕集的关键。离子液体具有气体亲和性好、蒸气压低、结构性质可调等特点,其中相变离子液体体系因节能潜力大被认为是新一代CO₂吸收剂,其吸收CO₂后由均相变为互不相溶的液-液或液-固两相,再生时仅需对CO₂富相加热处理,可有效减少吸收剂再生体积,降低再生能耗。重点总结近五年相变离子液体体系在CO₂分离的研究现状和进展,对不同相变行为的液-液和液-固相变离子液体体系分类阐述和讨论,并对其发展趋势进行展望。     

离子液体复配溶液吸收CO_2的研究进展

综述了近年来国内外利用离子液体吸收CO2的研究状况,重点分析了离子液体-水复配溶液和离子液体-有机胺复配溶液吸收分离CO2的特点及其机理,讨论了温度、压力、配比、特殊基团等相关影响因素对脱碳过程的影响。对尚存在的问题提出建议,并对前景做了展望。     

离子液体在CO2环加成反应中的应用

离子液体(ILs)作为一种新型的绿色溶剂,因其具有热稳定性好、挥发性低、结构可设计性等优点被广泛应用在CO_2环加成反应中。综述了由ILs催化CO_2与环氧化物的环加成反应制备环状碳酸酯的研究进展,从反应相态的角度将ILs催化剂分为普通ILs催化剂和负载ILs催化剂,分别阐述了其催化性能。简要分析了ILs催化剂目前存在的主要问题,并对ILs在CO_2环加成反应中的应用进行了展望。     

固载氨基化离子液体的制备及其对CO2的吸附性能

利用浸渍法将[NH₃P-mim][BF₄]和[MEA]L两种离子液体负载到AC、Al₂O₃和MCM-41上,考察了对CO₂的吸附性能,确定了[NH₃P-mim][BF₄]/AC对CO₂的吸附性能最优。并对[NH₃P-mim][BF₄]/AC考察了不同负载量、不同温度下对CO₂的吸附性能,确定了固载离子液体对CO₂的吸附容量随着负载量的增加而增加,且30℃是固载离子液体吸附CO₂的最佳温度,吸附容量达到0.063 mmol CO₂·(g SILP)^-1。对[NH₃P-mim][BF₄]/AC进行红外和热重两种表征,确定了负载离子液体的结构以及在50℃以下优良的热稳定性。     

离子液体中电化学还原CO2研究评述与展望

近百年来,伴随着矿石燃料的大量消耗,CO₂的排放量剧增,引发了全球性的生态环境和社会问题。CO₂同时也是廉价且可再生的碳资源,可作为生产醇、醚、酸、酯等重要化工品的原料。在众多吸引力十足的CO₂利用路线中,作为清洁、可控的反应过程,电化学还原固定CO₂技术在温和条件下生产化学品方面具有独特的优势。离子液体以其特有的性质被广泛用于电化学还原CO₂过程,本文对目前国内外离子液体介质中电化学还原CO₂的研究现状进行了综述,介绍了离子液体介质中电化学还原CO₂的主要反应及基本原理;针对离子液体对CO₂高效活化和转化等关键科学问题进行深入探讨,提出新型功能化离子液体的应用将成为CO₂电化学还原领域的发展方向和热点。     

氨基酸离子液体-MDEA混合水溶液的CO_2吸收性能

为改善N-甲基二乙醇胺(MDEA)水溶液对CO2气体的吸收性能,选择了四甲基铵甘氨酸([N1111][Gly])、四乙基铵甘氨酸([N2222][Gly])、四甲基铵赖氨酸([N1111][Lys])、四乙基铵赖氨酸([N2222][Lys])4种功能性离子液体作为活化剂与其复配组成新型CO2吸收剂。用恒定容积法考察了总质量分数为30%的混合溶液吸收CO2的性能,分析了离子液体在水溶液中与MDEA通过质子传递相互促进吸收CO2的机理。实验结果显示离子液体能够显著提高MDEA水溶液吸收CO2的速率,且吸收速率随着添加量的增加而提高。在本文所用的几种混合吸收剂中,阴离子为赖氨酸的离子液体混合吸收剂具有较高的吸收负荷;而[N1111][Gly]-MDEA混合溶液对CO2的初期吸收速率最快,同时[N1111][Gly]-MDEA混合吸收剂的再生效率高于其他离子液体混合吸收剂,达到98%。     

Enhanced gravimetric CO2 capacity and viscosity for ionic liquids with cyanopyrrolide anion

Ionic Liquids (ILs) are considered as alternative solvents for the separation of CO₂ from flue gas due mainly to their CO₂ affinity and thermal stability. The cation architecture in a matrix of ammonium and mostly phosphonium‐based ILs with 2‐cyanopyrrolide as the anion to evaluate its impact on gravimetric CO₂ absorption capacity, viscosity, and thermal stability and the three fundamental properties vital for application realization are systematically investigated. Among the investigated ILs, [P2,2,2,8][2‐CNpyr] demonstrated the lowest viscosity, 95 cP at 40°C, and highest CO₂ uptake, 114 mg CO₂ per g IL at 40°C. Combined effects of asymmetry and the optimized chain lengths also resulted in improved thermal stability for [P2,2,2,8][2‐CNpyr], with a mass loss rate of 1.35 × 10^?6 g h^?1 (0.0067 mass % h^?1) at 80°C. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2280–2285, 2015     

Hydrophobic protic ionic liquids tethered with tertiary amine group for highly efficient and selective absorption of H2S from CO2

Developing absorbents with both high absorption capacity of H₂S and large selectivity of H₂S/CO₂ is very important for natural gas sweetening process. To this end, a class of novel hydrophobic protic ionic liquids (ILs) containing free tertiary amine group as functional site for the absorption of H₂S were designed in this work. They were facilely synthesized through a simple neutralization‐metathesis methodology by utilizing diamine compounds and bis(trifluoromethylsulfonyl)imide as the building blocks for cation and anion, respectively. Impressively, the solubility of H₂S can reach 0.546 mol mol^?1 (1 bar) and 0.225 mol mol^?1 (0.1 bar), and the selectivity of H₂S/CO₂ can reach 37.2 (H₂S solubility at 1 bar vs. CO₂ solubility at 1 bar) and 15.4 (H₂S solubility at 0.1 bar vs. CO₂ solubility at 1 bar) in the hydrophobic protic ILs at 298.2 K. Comparing the hydrophobic protic ILs with other absorbents justifies their superior performance in the selective absorption of H₂S from CO₂. © 2016 American Institute of Chemical Engineers AIChE J, 62: 4480–4490, 2016     

Performance and pressure drop of CO2 absorption into task-specific and halide-free ionic liquids in a microchannel

The gas–liquid two-phase flow pattern, absorption rate and pressure drop of CO₂ absorbed into the aqueous solution of the task-specific ionic liquids (1-aminopropyl-3-methylimidazole tetrafluoroborate [Apmim][BF₄] and 1-hydroxyethyl-3-methylimidazole tetrafluoroborate [OHemim][BF₄]) and halide-free ionic liquid 1-butyl-3-methylimidazolium methylsulfate [Bmim][CH₃SO₄] were investigated in a microreactor. The absorption mechanism of the three ionic liquids was analyzed employing the ¹³C NMR spectroscopy. The [Apmim][BF₄] was found to have the best ability of CO₂ capture compared with the other two ionic liquids, as chemical absorption occurred between [Apmim][BF₄] and CO₂, while only physical absorption took place between [OHemim][BF₄]/[Bmim][CH₃SO₄] and CO₂. The sequence of CO₂ absorption rate in three ionic liquids aqueous solutions is: [Apmim][BF₄] > [Bmim][CH₃SO₄] > [OHemim][BF₄]. Furthermore, the effects of gas–liquid flow rate and ionic liquids concentration on CO₂ absorption rate and pressure drop were studied, the pressure drop models based on various flow patterns were proposed.     

Protic ionic liquids for the selective absorption of H2S from CO2: Thermodynamic analysis

The solubilities of H₂S and CO₂ in four protic ionic liquids (PILs)—methyldiethanolammonium acetate, methyldiethanolammonium formate, dimethylethanolammonium acetate, and dimethylethanolammonium formate were determined at 303.2–333.2 K and 0–1.2 bar. It is shown PILs have higher absorption capacity for H₂S than normal ionic liquids (ILs) and the Henry's law constants of H₂S in PILs (3.5–11.5 bar at 303.2 K) are much lower than those in normal ILs. In contrast, the solubility of CO₂ in PILs is found to be a magnitude lower than that of H₂S, implying these PILs have both higher absorption capacity for H₂S and higher ideal selectivity of H₂S/CO₂ (8.9–19.5 at 303.2 K) in comparison with normal ILs. The behavior of H₂S and CO₂ absorption in PILs is further demonstrated based on thermodynamic analysis. The results illustrate that PILs are a kind of promising absorbents for the selective separation of H₂S/CO₂ and believed to have potential use in gas sweetening. © 2014 American Institute of Chemical Engineers AIChE J 60: 4232–4240, 2014     

Solubility of CO2 in three cellulose-dissolving ionic liquids

The solubility of CO₂ in three cellulose-dissolving ionic liquids (1-ethyl-3-methylimidazolium diethylphosphate, [Emim][DEP], 1-allyl-3-methylimidazolium chloride, [Amim][Cl], and 1-butyl-3-methylimidazolium chloride, [Bmim][Cl]) at temperatures within 298 and 356 K and pressures up to 6.5 MPa was determined using a Van Ness-type apparatus (static isochoric). It was demonstrated that this device can work in isothermal and isoplethal modes, being the latter faster and more precise. Moreover, it was possible to determine CO₂ solubilities in metastable liquid [Bmim][Cl]. Experimental data were modeled using the Extended Henry's law correlation and the group contribution equation of state. New parameters for the binary interaction of CO₂ with ionic liquid groups were calculated.     

肉桂酸型离子液体的合成及其二氧化碳吸收

合成了一系列肉桂酸型功能化离子液体,研究了其CO₂ 吸收性能。结果表明,肉桂酸型功能化离子液体吸收二氧化碳性能良好,其阴离子苯环上的取代基会影响CO₂ 吸收性能。随着温度的升高和压力的降低,其CO₂吸收性能都会降低。同时,该离子液体具有很好的循环稳定性,经过5 次吸收脱附循环,该离子液体仍能保持较高的CO₂ 吸收量。结合红外光谱和其低浓度下CO₂ 的吸收研究发现肉桂酸型离子液体吸收CO₂ 存在着化学作用。     

Promoted adsorption of CO2 on amine‐impregnated adsorbents by functionalized ionic liquids

Amine‐impregnated adsorbents are promising alternatives to aqueous amines for CO₂ capture. However, the diffusion‐controlled CO₂ adsorption process is a significant issue associated with them, resulting in the insufficient utilization of amine groups. Herein, we propose the use of functionalized ionic liquids 1‐ethyl‐3‐methylimidazolium acetate ([emim][Ac]) with chemical reactivity to CO₂ and low viscosity as the additive to amine‐impregnated adsorbents. The key is that [emim][Ac] does not show drastic increase in viscosity after reacting with CO₂. Taking the polyethyleneimine (PEI)‐impregnated SBA‐15 as a model system, it is found that the CO₂ capacities of PEI/SBA‐15 composites are improved by 86%, and the active site efficiencies are improved by 270%, after the addition of [emim][Ac]. The addition of [emim][Ac] to PEI/SBA‐15 composites also helps improve the CO₂ adsorption rate and recycling stability of composites. Therefore, [emim][Ac] offers the opportunity to fabricate amine‐impregnated adsorbents with simultaneously improved CO₂ capacities, adsorption kinetics, and recycling stability. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3671–3680, 2018