含醚阴离子功能化离子液体高效捕集SO2

发展高效、经济、绿色的SO₂吸收剂不但具有较强的学术价值,而且有良好的应用前景。设计并制备了一系列含醚的阴离子功能化离子液体,系统地研究了阴离子上引入醚基团对离子液体SO₂吸收容量的影响。结果表明,在阴离子的苯环上引入甲氧基,对离子液体的吸收容量有明显提升。当阳离子为摩尔质量更小的三丁基乙基磷[P₄₄₄₂]时,所得离子液体的吸收容量没有明显下降,20℃、10⁵ Pa SO₂下,[P₄₄₄₂][2-CH₃OPhCOO]有效吸收量为每摩尔离子液体吸收3.32 mol SO₂,有效质量吸收量是每克离子液体吸收0.56 g SO₂。六次吸收解吸循环,表明[P₄₄₄₂][2-CH₃OPhCOO]可以高效可逆地捕集SO₂。基于含醚阴离子功能化离子液体的加强效应进行气体捕集的方法,可进一步应用于分离、催化等领域。     

蒸汽活化钙基吸收剂联合脱碳脱硫特性

利用管式炉（TF）、蒸汽发生器和热重分析仪（TGA）研究了钙基吸收剂联合脱碳脱硫以及水合特性,并通过N2吸附实验对不同烧结程度以及水合前后样品的孔隙结构进行了测量。结果表明,无水合时,40次碳化循环后的样品碳化活性降至18%,但仍具有44%的硫化活性,比新鲜剂仅低4%,说明脱碳失效剂仍是良好的脱硫剂。碳循环失效剂经蒸汽活化后其碳化活性可提高至68%左右,且具有与新鲜剂类似的活性下降规律。每两次碳化循环后进行一次蒸汽活化,可使样品保持65%的平均转化率。蒸汽活化后吸收剂硫化率可提高至80%,远高于新鲜剂,由电镜扫描实验发现这是由于水合时颗粒产生了大的裂缝和破碎,提供了大量产物可自由生长的外表面积。不考虑颗粒磨损,利用钙基吸收剂先循环脱碳再蒸汽活化最后脱硫是一项联合脱除烟气中CO₂和SO₂的新方法。     

基于MDEA的烟气SO2捕集过程工艺参数和能量集成分析

有机胺吸收法是一种高效环保型烟气脱硫技术,而从系统工程的角度对烟气SO₂捕集工艺的分析、优化和能耗评估尚未有详细报道。对N-甲基二乙醇胺（MDEA）为吸收剂的烟气SO₂捕集过程工艺进行研究,考察了MDEA浓度、温度、SO₂解吸率对捕集效果的影响规律。结果显示,MDEA溶液浓度为30%（质量）、烟气温度不高于45℃、回流贫液温度不高于41℃时,SO₂吸收效果较好;增加SO₂解吸率是以降低解吸气中SO₂纯度和增大再沸器负荷为代价,水分汽化是再生能耗增高的主要原因。针对吸收剂再生过程能耗大的问题,采用热泵辅助精馏对解吸过程进行能量集成,吸收剂再生能耗可降低47%,年度总费用（TAC）可降低9.93%。本研究对有机胺体系的SO₂捕集系统工业化应用具有重要的指导作用。     

State of the art of ionic liquid-modified adsorbents for CO2 capture and separation

The enormous emission of carbon dioxide (CO₂) from industries has triggered a series of environmental issues. In recent years, ionic liquids (ILs) as novel absorbents are widely used for CO₂ capture owing to their low vapor pressure and tunable structures. IL-modified adsorbents have the advantages of both ILs and porous supports, such as high CO₂ selectivity and high specific surface area, which are novel agents to capture CO₂ with broad application prospects. In this review, more than 140 IL-modified adsorbents for CO₂ capture in recent years were systematically summarized. The types of ILs including conventional ILs and functionalized ILs on CO₂ separation performance of different IL hybrid adsorbents, and their adsorption mechanisms were also discussed. Finally, future perspectives on IL-modified adsorbents for CO₂ separation were further posed.     

Confining organic cations in metal organic framework allows molecular level regulation of CO2 capture

High tunability of both ionic liquids (ILs) and metal organic frameworks (MOFs) enables great opportunity in the rational designation of IL/MOF composites for physical adsorption and separation. Traditionally, cations and anions of ILs as an entirety are combined with MOFs either inside or outside the microchannels. Herein, organic cations of ILs were confined into Cu-BTC and the champion adsorbent is obtained by using 1-propionic acid-3-vinylimidazole bromide as the precursor with a moderate loading amount, exhibiting higher CO₂ uptakes of 8/5 mmol g⁻¹ than Cu-BTC (6.0/3.5 mmol g⁻¹) at 273/298 K and 100 kPa, associating with significantly improved CO₂/N₂(CH₄) selectivities. The organic cations are interacted with two adjacent CuII₂(CRO₂)₂ paddle wheel units of Cu-BTC, expanding the Cu O bond to strengthen the CO₂ affinity of open Cu sites and also serving as an additive CO₂ adsorptive site. The promotion of CO₂ capture ability is further reflected in the dynamic column breakthrough experiment.     

胆碱类低共融溶剂在CO2捕集与分离中的应用

胆碱类低共融溶剂是一种新型的离子液体。它不仅具有传统离子液体的优点,还具有价格低廉、低毒、生物可降解等优势。对胆碱类低共融溶剂在CO₂捕集与分离中所涉及的物理性质,如气体的溶解度、CO₂的吸收-解吸、密度、稳定性、黏度和表面张力等进行考察,并分析了胆碱类低共融溶剂的结构对各物性的影响。通过与传统离子液体的对比,胆碱类低共融溶剂在CO₂捕集与分离中的应用具有一定的优势,如CO₂溶解度高,黏度低。然而,胆碱类低共融溶剂在气体的选择性分离、表面张力等的研究还不足,且热稳定性方面还存在瓶颈,因此,其在CO₂捕集和分离中的应用还有待进一步探讨。     

燃煤烟气中SO2对氨法脱碳的影响

利用湿壁塔实验台对燃煤烟气中SO₂对氨水溶液［1%～7%(质量）］吸收CO₂的影响进行了实验研究,具体分析了不同反应温度（20～80℃）和CO₂体积分数（5%～20%）条件下,CO₂传质通量及传质系数随SO₂浓度和SO₂负载量的变化规律。结果表明, SO₂浓度由0增至11428 mg·m^-3,CO₂传质通量及传质系数均有一半左右降幅,而SO₂负载量［0.1～0.4 mol SO₂·（mol NH₃）^-1］的增加,同样导致CO₂传质通量及传质系数明显减小。氨水浓度及反应温度增加可有效提高CO₂传质通量和传质系数,相对降低SO₂对CO₂传质的影响。CO₂浓度的增加可明显提高其传质通量,但是CO₂的传质系数有所降低。     

功能化离子液体在二氧化碳吸收分离中的应用

吸收及分离二氧化碳是降低碳排放和应对全球气候变化的主要策略之一,这就必然要求全球科技工作者注重开发具有选择性高效吸收分离二氧化碳的新材料和新路线。作为近20多年来发展的一类代表性的新材料,离子液体（尤其是功能化离子液体）具有独特的物理化学性质,例如几乎没有蒸气压、液态温度范围大、热稳定性和化学稳定性好、电化学窗口宽、不可燃、结构-性质可调控等。这些性质使离子液体在二氧化碳吸收及分离领域受到广泛关注。重点综述了近5年（2015~2019）来功能化离子液体吸收分离二氧化碳的研究进展, 主要内容包括单位点离子液体、多位点离子液体、基于功能化离子液体的混合物、功能化离子液体杂化材料对二氧化碳的吸收分离。同时, 对目前该领域的发展所面临的主要问题和进一步的研究工作进行了分析讨论。     

机械化学法合成小尺寸MOF填料助力高性能CO2分离

利用金属-有机骨架UTSA-280具有特定刚性尺寸的一维孔道可以筛分CO₂、CH₄、N₂的特性,采用机械化学研磨法减小其颗粒尺寸,将UTSA-280掺入聚砜（PSf）中制备MOF基混合基质膜,用于天然气提纯和烟道气CO₂捕获。结果表明,在PSf中掺入UTSA-280不仅可以增加聚合物的CO₂渗透通量而且提高了气体分离选择性。当UTSA-280掺杂量为30%（质量）时,混合基质膜对CO₂/CH₄、CO₂/N₂的分离因子分别为56.39和53.17,CO₂的渗透通量为18.61 Barrer,相对于PSf纯膜,选择性分别提高了47.3%和63.5%,CO₂渗透通量提高了128.9%,打破了“trade-off”效应。该工作通过引进具有分子筛分效应的MOF填料,能够增加气体通量的同时提高混合基质膜对含CO₂气体的分离性能,对天然气的提纯以及烟道气的CO₂的捕获有重要意义。     

Pyrazine-interior-embodied MOF-74 for selective CO2 adsorption

A series of pyrazine-interior-embodied metal–organic framework-74 composites (py-MOF-74) were successfully synthesized by a post-synthetic vapor modification method. Here, pyrazine molecules occupy the cavity to block the wide pores of MOF-74, which accentuates the difference in adsorption of a pair of gases on MOFs and consequently reinforces the adsorption selectivity. Different from the “physical confinement” of occupants, the pyrazine molecule with dual “para-nitrogen” atoms donates one N atom to bond with the open metal ion of MOF-74 for stability and the other N atom for potential CO₂ trapping. Typically, py-MOF-74c with the highest pyrazine insertion ratio displays selectivity greatly superior to that of MOF-74 in equimolar CO₂/CH₄ (598 vs. 35) and in simulated CO₂/N₂ flue gas (471 vs. 49). Py-MOF-74 entities are long-lived adsorbents, and their CO₂ capacity can be maintained even after storage for 1 year in air. Py-MOF-74 also showed a sharp molecular sieve property in fixed-bed cycle adsorption tests, which implies its great potential in real applications.     

Efficient adsorption separation of acetylene and ethylene via supported ionic liquid on metal‐organic framework

Ionic liquid (IL) supported metal‐organic framework (MOF) was utilized to efficiently separate acetylene from ethylene. A common IL, 1‐butyl‐3‐methylimidazolium acetate ([Bmim][OAc]), was encapsulated into a hydrothermally stable MOF, namely MIL‐101(Cr). Characterization techniques including FTIR, Powder X‐ray diffraction, BET, and thermal gravimetric analysis were used to confirm successful encapsulation of the IL within MIL‐101(Cr). Adsorption isotherms of acetylene and ethylene in the IL‐encapsulated MOF were tested. From the results, the MOF composite retained a relatively high adsorption capacity. Remarkably, the adsorption selectivity of acetylene/ethylene has dramatically increased from 3.0 to 30 in comparison with the parent MIL‐101(Cr). Furthermore, the potential of industrial practice was examined by breakthrough and regeneration experiments. It not only satisfies the industrial production of removal of low level of acetylene from ethylene, but also is notably stable during the adsorption‐desorption process. The high designability of ILs combined with richness of MOFs’ structures exploits a novel blueprint for gas separation. © 2016 American Institute of Chemical Engineers AIChE J, 63: 2165–2175, 2017     

A highly stable metal‐organic framework with optimum aperture size for CO2 capture

We herein report an optimal modulated hydrothermal (MHT) synthesis of a highly stable zirconium metal‐organic framework (MOF) with an optimum aperture size of 3.93 Å that is favorable for CO₂ adsorption. It exhibits excellent CO₂ uptake capacities of 2.50 and 5.63 mmol g^?1 under 0.15 and 1 bar at 298 K, respectively, which are among the highest of all the pristine water‐stable MOFs reported so far. In addition, we have designed a lab‐scale breakthrough set‐up to study its CO₂ capture performance under both dry and wet conditions. The velocity at the exit of breakthrough column for mass balance accuracy is carefully measured using argon with a fixed flow rate as the internal reference. Other factors that may affect the breakthrough dynamics, such as pressure drop and its impact on the roll‐up of the weaker component have been studied in details. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4103–4114, 2017     

Designing of anion‐functionalized ionic liquids for efficient capture of SO2 from flue gas

Five kinds of anion‐functionalized ionic liquids (ILs) with different basicity and substituent were selected, prepared and applied in the capture of SO₂ from flue gas, where the concentration of SO₂ is only 2000 ppm. The effect of the anion on SO₂ absorption capacity, desorption residue, and available absorption capacity under 2000 ppm was investigated. The relationship between available absorption capacity and absorption enthalpy was also studied. Through a combination of thermodynamic analysis and quantum calculation, the results indicated that the effect of the cation in the IL on absorption enthalpy was significant. However, the effect of chain length in the cation was weak. Hence, a new IL with low molecular weight, [P₄₄₄₂][Tetz], was further designed and applied for the capture of SO₂, which shows the high absorption capacity of 0.18 g SO₂ per g IL and excellent reversibility for 2000 ppm SO₂. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2028–2034, 2015     

烟气组分对[BPy]Br/AC去除SO2行为的影响

在负载型离子液体溴代正丁基吡啶/活性炭([BPy]Br/AC)脱除SO2性能研究的基础上,通过改变模拟烟气组成,分别研究了该脱硫剂在同一担载比(0.36∶1)相同载体质量(4g)条件下,水蒸气、氧气、二氧化碳及氧气、二氧化碳和水蒸气相互组合对该脱硫剂脱除SO2性能的影响.结果表明,在研究的条件范围内,烟气组分水蒸气、氧气、二氧化碳与SO2同时存在时,存在竞争反应,水蒸气及二氧化碳对该脱硫剂有明显的负面影响.氧气对该脱硫剂脱硫性能的影响相对较弱.     

Thermodynamic-kinetic synergistic separation of CH4/N2 on a robust aluminum-based metal-organic framework

A robust aluminum-based metal–organic framework (Al-MOF) MIL-120Al with 1D rhombic ultra-microporous was reported. The nonpolar porous walls composed of para-benzene rings with a comparable pore size to the kinetic diameter of methane allow it to exhibit a novel thermodynamic-kinetic synergistic separation of CH₄/N₂ mixtures. The CH₄ adsorption capacity was as high as 33.7 cm³/g (298 K, 1 bar), which is the highest uptake value among the Al-MOFs reported to date. The diffusion rates of CH₄ were faster than N₂ in this structure as confirmed by time-dependent kinetic adsorption profiles. Breakthrough experiments confirm that this MOF can completely separate the CH₄/N₂ mixture and the separation performance is not affected in the presence of H₂O. Theoretical calculations reveal that pore centers with more energetically-favorable binding sites for CH₄ than N₂. The results of pressure swing adsorption (PSA) simulations indicate that MIL-120Al is a potential candidate for selective capture coal-mine methane.     

基于酸度系数(pKa)模型的胺法SO2捕集过程多目标效能分析

筛选高SO₂吸收容量、低解吸能耗的吸收剂是提高胺基烟气SO₂捕集工艺应用潜力的重要途径。本研究采用SMD连续溶剂化模型和密度泛函理论在M05-2X/6-31G*基组水平上预测了5种有机二胺类物质的pK_a,基于预测的pK_a建立起吸收剂对SO₂吸收容量和解吸反应热的数学模型,以探讨有机二胺-酸-水三元体系吸收剂捕集SO₂过程中的效能关系。结果表明,数学模型符合工程精度要求。二胺的SO₂吸收容量和脱质子反应焓都随pK_a增大而增加,筛选有机胺吸收剂展现出对SO₂吸收容量和反应焓的多目标矛盾性特征;量化了5种二胺的SO₂循环吸收容量和解吸反应热的数值关系,在相同SO₂循环容量条件下,5种二胺中羟乙基哌嗪（HEP）的解吸热最小,HEP为有机二胺-酸-水三元体系中的一种潜力二胺类吸收剂。     

Chemical solvent in chemical solvent: A class of hybrid materials for effective capture of CO2

Amino acid ionic liquids (AAILs) are chemical solvents with high reactivity to CO₂. However, they suffer from drastic increase in viscosity on the reaction with CO₂, which significantly limits their application in the industrial capture of CO₂. In this work, 1‐ethyl‐3‐methylimidazolium acetate ([emim][Ac]) which also exhibits chemical affinity to CO₂ but low viscosity, and its viscosity does not increase drastically after CO₂ absorption, was proposed as the diluent for AAILs to fabricate hybrid materials. The AAIL+[emim][Ac] hybrids were found to display enhanced kinetics for CO₂ absorption, and their viscosity increase after CO₂ absorption are much less significant than pure AAILs. More importantly, owing to the fact that [emim][Ac] itself can absorb large amount of CO₂, the AAIL+[emim][Ac] hybrids still have high absolute capacities of CO₂. Such hybrid materials consisting of a chemical solvent plus another chemical solvent are believed to be a class of effective absorbents for CO₂ capture. © 2017 American Institute of Chemical Engineers AIChE J, 64: 632–639, 2018     

Enhanced one-step purification of C2H4 from C2H2/C2H4/C2H6 mixtures by fluorinated Zr-MOF

The extraction of C₂H₄ from C₂H₆/C₂H₄/C₂H₂ mixtures is of great significance in the chemical industry for C₂H₄ production but the process remains challenging due to the similarity of these C₂ hydrocarbon species in their molecular size and physical properties. Here, we report the fluorination of a stable Zr-MOF, UiO-66, to fine-tune the pore dimensions and pore functionality. In particular, UiO-66-CF₃ shows notably preferential adsorption of C₂H₆ and C₂H₂ over C₂H₄, with C₂H₂/C₂H₄ and C₂H₆/C₂H₄ selectivities of 1.4 and 1.9, respectively. Theoretical calculations provide insight into the binding sites of UiO-66-CF₃ for C₂ hydrocarbon adsorption. Breakthrough experiments further confirmed the capability of the material for purification of C₂H₄ from C₂H₂/C₂H₄/C₂H₆ ternary mixtures, evidenced by the high purity C₂H₄ (99.9%+) obtained directly from outlet gas.     

Chelation of transition metals into MOFs as a promising method for enhancing CO2 capture: A computational study

Metal organic frameworks (MOFs) are one kind of promising porous materials for CO₂ capture and separation. In this work, the chelation of the first-row transition metals (from Sc to Zn) into MOFs was proposed to enhance its CO₂ adsorption capacity. The adsorption mechanisms and adsorption capacities of CO₂ in the chelated MOFs were explored by using quantum mechanical calculation and QM-based grand canonical Monte Carlo simulations. The results show that the chelation of transition metals can significantly improve the adsorption capacity of CO₂ in MOFs, especially at low pressure. Among the first row transition metals, the chelation of Mn(II), Fe(II), Co(II), Ni(II), Cu(II), and Zn(II) gives higher binding energies than other transition metals. The chelation of Mn(II) into MOFs shows the highest uptake amount at low pressure. The CO₂ uptake amounts in UiO(bpydc)-MnCl₂ and BPV-MOF-MnCl₂ are about six times higher than the original counterparts at 298 K and 100 kPa. Based on this significant enhancement, the chelation of transition metals in MOFs provides an efficient approach for enhancing CO₂ capture.