Dispersion Property of CO2 in Oil. Part 3: Aggregation of CO2 Molecule in Organic Liquid at Near Critical and Supercritical Condition of CO2

To study the dispersion property of CO₂ in organic liquids, the solubility of CO₂, the volume of CO₂ + organic liquids under different pressure at 318.15 K were measured and the radial distribution function of CO₂ molecule aggregate in the organic liquids was calculated by molecule dynamic simulation. The results show that the aggregate of CO₂ molecules in the organic liquids is formed obviously; the aggregation and disperse property of CO₂ molecule in the organic liquids is affected by the structure and polarity of the organic molecule at near critical and supercritical condition of CO₂ dominantly.     

超临界CO2/离子液体体系

超临界CO2和离子液体是两种具有优异性能的绿色化学试剂,本文介绍了将两者结合反应,分离体系的物化性质和多种绿色化学过程。利用超临界CO2可以广泛地萃取离子液体中的不挥发性化合物而不导致离子液体及其中催化剂的流失,在加氢、醛化、甲酰化等反应,分离过程中的应用表明,过程具有很好的反应分离特性和环境友好性,应用前景广阔。     

Electrocatalytic Recycling of CO2 and Small Organic Molecules

As global warming directly affects the ecosystems and humankind in the 21^st century, attention and efforts are continuously being made to reduce the emission of greenhouse gases, especially carbon dioxide (CO₂). In addition, there have been numerous efforts to electrochemically convert CO₂ gas to small organic molecules (SOMs) and vice versa. Herein, we highlight recent advances made in the electrocatalytic recycling of CO₂ and SOMs including (i) the overall trend of research activities made in this area, (ii) the relations between reduction conditions and products in the aqueous phase, (iii) the challenges in the use of gas diffusion electrodes for the continuous gas phase CO₂ reduction, as well as (iv) the development of state of the art hybrid techniques for industrial applications. Perspectives geared to fully exploit the potential of zero‐gap cells for CO₂ reduction in the gaseous phase and the high applicability on a large scale are also presented. We envision that the hybrid system for CO₂ reduction supported by sustainable solar, wind, and geothermal energies and waste heat will provide a long term reduction of greenhouse gas emissions and will allow for continued use of the abundant fossil fuels by industries and/or power plants but with zero emissions.     

Mean Residence Time of CO2 Molecules in Flexible ZIF-8 Cages Explored by Molecular Dynamics Simulations

The adsorption sites and diffusion mechanism of CO2 molecules in the flexible Zn（MeIM）2 （MeIM=2-methylimidazole） （ZIF-8） have been investigated by grand canonical Monte Carlo and molecular dynamics simulations. A reasonable time correlation function is for the first time constructed to explore the mean residence time of CO2 molecules in the ZIF-8 cages, suggesting that C02 molecules can remain in the same cage for up to several tens of picoseconds. Furthermore, we find that the mean residence time almost linearly increases with the increasing pressure （or loading） at 273 and 298 K.     

双功能离子液体的合成及二氧化碳捕集性能

采用两步法合成了新型功能化离子液体1-甲氧基乙基-3-甲基咪唑甘氨酸([C_3O_1mim][Gly]),并研究了其对CO_2的吸收性能.利用核磁共振、红外光谱及热重分析等手段进行表征,验证了该离子液体的结构,且发现其具有较高的热稳定性.对比单乙醇胺(MEA),考察了[C_3O_1mim][Gly]在不同温度下对CO_2的捕集能力,结果表明,[C_3O_1mim][Gly]在40℃下的吸收容量可达1.26 mol CO_2/mol IL,远高于MEA,这表明[C_3O_1mim][Gly]对CO_2具有良好的吸收能力,吸收容量随着温度升高而降低.该离子液体同时具有良好的循环稳定性,进行5次吸收解吸操作后仍可保持较高的CO_2吸收量.对该离子液体吸收CO_2进行了动力学研究,结果表明,Pseudo-second-order模型能够较好地描述该吸收过程.     

超临界CO2与叔丁醇二元系统高压相平衡研究

采用固定体积可视观察法测量装置测定了CO2与叔丁醇在323.2~353.2 K温度范围内于不同压力下的平衡数据, 并运用Peng-Robinson状态方程(PR)和Van der Waals-2混合规则建立了相平衡模型, 通过非线性最小二乘法优化计算得到了不同温度下的模型参数. 并得到了模型参数与温度的表达式, 分别为k12=-199.2066+1.8136T-0.00548T2+5.50×10-6T3; n12=-384.5626+3.4960T-0.01056T2+1.06×10-5T3.获得了此体系在不同组成下的临界压力、临界温度、临界摩尔体积、临界压缩因子和临界密度等临界性质. 研究结果表明, CO2与叔丁醇二元体系的临界温度、临界压力和临界压缩因子均随着临界CO2组成的增加而降低.     

Oxidation of Styrene with Molecular Oxygen in Supercritical CO2

The oxidation of styrene with molecular oxygen catalyzed by PdCl2 CuCl2 has been investigated in supercritical CO2 with a batch reactor. The oxidative system of styrene contains four components at the beginning and seven components during the reaction. The critical temperature, critical pressure, and critical density at different conversions are determined by using a high-pressure view cell. The effect of phase behavior on the conversion and selectivity were studied. Experimental results showed that the critical parameters of the reaction mixture at fixed initial molar ratio changed with the conversion of reactant. The conversion of styrene reached maximum near the critical density of the reaction mixture. Product selectivity also varied with density of reaction mixture and could be tuned to some degree.     

CO2/离子液体体系热力学性质的分子动力学模拟

超临界CO2和离子液体(ILs)是两种绿色溶剂. 离子液体可以溶解超临界CO2, 而超临界CO2不能溶解离子液体. 由此设计构成的CO2/IL二元系统, 同时具备了超临界CO2和离子液体的许多优点: 既可以降低离子液体的粘度, 还便于相分离, 是新型的耦合绿色溶剂. 其物理化学性质对于设计反应、分离等过程非常重要. 因此, 本文以CO2/IL二元系统为研究对象, 通过选择合适的分子力场和系综, 运用分子动力学(MD)模拟方法研究了CO2/[bmim][PF6]、CO2/[bmim][NO3]等体系的热力学性质. 结果表明, CO2对ILs膨胀度的影响非常小, 当CO2摩尔分数为0.5时, ILs膨胀仅为15%. CO2/ILs的扩散系数远小于CO2膨胀甲醇、乙醇溶液的扩散系数. 随着CO2含量的增加, ILs的扩散系数提高, 粘度显著下降, 表明CO2能有效地改善ILs扩散性, 减小其粘度. 因此CO2可用以改善离子液体溶剂体系的传递特性, 增强反应分离过程在其中的进行.     

[C14MIM]Br离子液体对聚丙烯超临界CO2发泡性能的影响

本文对PP/[C₁₄MIM]Br体系的熔融过程和对CO₂的吸收, 以及[C₁₄MIM]Br在PP基体中的分散状态进行了研究, 并初步考察了[C₁₄MIM]Br对PP发泡性能的影响.     

离子液体在CO_2电还原反应过程中的催化作用与机理研究

在1-丁基3-甲基咪唑三氟甲基磺酸盐([Bnlim][CF_3SO_3])/碳酸丙烯酯(PC)溶液中,采用循环伏安曲线、交流阻抗谱及阻抗模拟方法,研究了CO_2在Au上发生电还原反应的速率控制步骤与离子液体的催化作用.结果表明,在CO_2电还原反应过程中,吸附态CO_2经单电子还原生成CO_2~-自由基是速率控制步骤.由于离子液体的催化作用,CO_2在[Bmim][CF_3SO_3]/PC溶液中电还原的过电位比在四丁基三氟甲基磺酸铵([Bu_4N][CF_3SO_3])/PC溶液中降低了239 mV.交流阻抗测试结果表明,离子液体中的阳离子[Bmim]~+吸附在Au电极表面,形成离子液体吸附层,吸附态的CO_2分子经单电子还原后生成CO_2~·-)自由基,与周围离子液体发生相互作用,形成中间体[Bmim-CO_2]_(ad),降低了CO_2~(·-)的能量状态,使得CO_2电还原反应的过电位大幅度降低.     

超临界合成Pt修饰的TiO2用于光催化CO2还原制备太阳能燃料

考察了超临界条件下合成TiO2基光催化剂的性质,尤其是在超临界CO2下得到的分散在TiO2上Pt的特性,并与商品化TiO2性能进行了比较.另外,所得催化剂的光催化活性用CO2光还原制太阳能燃料进行了评价.结果表明,该催化剂可得到具有比商用TiO2更好或类似的性能(高比表面积、结晶度、表面羟基浓度,大的孔容、增强的可见光吸收、高的甲烷生成速率)而用于CO2还原制备燃料的反应中.这可归因于该催化剂超临界介质合成过程.     

CO2在非质子溶剂与铁基离子液体复合体系中的吸收

选用非质子型有机溶剂聚乙二醇二甲醚(NHD)与N, N-二甲基乙酰胺(DMAC), 分别与BmimFeCl₄复配, 构建了BmimFeCl₄/NHD和BmimFeCl₄/DMAC复合铁基离子液体体系. 考察了温度、 BmimFeCl₄/溶剂的质量 比以及压力对CO₂在复合铁基离子液体体系中溶解行为的影响. 结果表明, 高压低温的吸收条件更利于CO₂ 的溶解, 当BmimFeCl₄/DMAC质量比为7∶3时, CO₂在BmimFeCl₄/DMAC复合体系中的亨利系数为0.9181 MPa·L·mol^-1, 低于同等条件下BmimFeCl₄/NHD体系的亨利系数. 在常压、 363.2 K条件下进行再生, 经5次循环后, CO₂在BmimFeCl₄/NHD和BmimFeCl₄/DMAC中的溶解度分别为初次吸收量的92.53%和99.04%. 傅里叶变换红外光谱(FTIR)结果表明, 铁基离子液体复配体系吸收CO₂为物理吸收过程. 密度泛函理论(DFT)计算与IRI分析的结果表明, 在复配DMAC的体系中, CO₂更倾向与阳离子和溶剂分子作用, 而在复配NHD的体系中, CO₂则更容易与阴离子和溶剂分子作用.     

Sustainable Production of Chemicals via Hydrotreating of CO2 and Biomass Derived Molecules Using Heterogeneous Noble Metal Oxide Catalysts

The noble metals are widely used in heterogeneous catalysis and automobile industry. The limited natural sources and high cost of noble metals dictates improving the efficiency of modern industry. This review considers the applications of noble metal oxide as potential solutions to the sustainability issues, including biomass conversion, CO₂ capture and conversion, green fuel production, etc. Noble metal oxides with their different compositions (monometallic and bimetallic) and structures exhibit a wide range of properties in heterogeneous catalysis. Although platinum metals in an oxidized form may not be the most common choice in hydroprocesses; recently, there have been studies indicating that they were highly active and selective catalysts in hydrogenation and hydrogenolysis. This review outlines the most established noble metal oxide catalysts used in hydrogenation catalysis and shed the light on the relation of noble metal oxide species to catalyst selectivity based on state-of-the-art techniques. Finally, the perspectives on the application of noble metal oxide catalysts to produce value-added chemicals are discussed.     

聚吡咯薄膜在超临界CO_2与离子液体两相体系中的电化学合成

首次在超临界CO2与离子液体两相体系中实现了聚吡咯（PPyr）薄膜的电化学合成.与纯离子液体相比,该体系中合成的PPyr膜具有均匀平滑的表面.随着CO2压力的增加,膜的生长速度减慢,膜的表面变得更加均匀平滑.     

Theoretical Studies on Critical Properties of Binary System with Supercritical Carbon Dioxide

A new expression of mixing rule is suggested according to the Mayson‘s mixing rule in this paper,which adopts the Redlich-Kwong cubic equation of state and the modifed Chueh-Prausnitz method to calculate the experiment critical points of six binary mixtures CO2 toluene,CO2 cyclohexane,CO2 n-butanal,CO2 i-butanal,CO2 methanol,CO2 ethanol.The coefficients of interaction parameter in the expression of mixing rule were optimized from experimental data.The calculated results of critical temperature and critical pressure meet the experiment data well.The maximum relative errore of temperature and pressure between the calculation results and experiment data are 1.493% and 5.2236% respectively,indicating that the proposed expression of mixing rule is reasonable.This may provide a fundamental method for studying and predicting the properties of supercritical fluids.     

A Comparison of Modeling Approaches for Dispersion Homopolymerization of MMA and Styrene in Supercritical CO2

A comparison of kinetic models for dispersion polymerization of MMA and styrene in supercritical CO₂ is presented. The limiting case of solution polymerization, as a simplified case, was also addressed. Calculation of the partition of components between the continuous and dispersed phases was emphasized. Experimental data for the solution and dispersion polymerizations of styrene and MMA, using different types of stabilizers, were used to guide the study. Although all the models analyzed can be considered as “adequate” in representing the behavior of the system, some of their strengths and drawbacks have been highlighted.

     

钴联吡啶配合物在硅电极表面高效光电催化二氧化碳还原反应（英文）

光驱动二氧化碳还原实现可再生能源转化近年来引起普遍关注.利用小分子金属配合物电催化剂和吸光半导体材料构建的光电催化体系兼具电催化剂的高选择性和光电极的高光电转化效率等优点,在能源催化领域的应用日益广泛.已有将贵金属配合物催化剂用于光电催化二氧化碳还原的研究报道,但催化剂成本较高且制备方法不简便,在规模化实际应用中受到局限.基于早期的研究报道,我们发现非贵金属多联吡啶铁钴镍配合物在乙腈电解质中能高选择性电催化还原二氧化碳.结合半导体材料的特异性电荷分离性能从而将光能高效转化为电能驱动催化反应进行,我们选择廉价且易于制备的多联吡啶钴配合物催化剂,利用半导体硅晶片光电极,实现了均相体系二氧化碳的高效光电催化还原.我们采用电化学循环伏安法和恒电位电解法分别研究了催化剂在干燥和加水电解质环境中的催化还原行为,并且进一步研究了微量质子源的加入对半导体界面催化过程的影响,从而提出一种能改善半导体光电催化体系选择性的新方法.首先我们构建了电化学三电极体系,研究了在暗环境下三联吡啶钴和二联吡啶钴这两种配合物催化还原二氧化碳的电流密度和电解产物分布情况.由循环伏安曲线发现,这两种配合物都有两组催化还原峰,第二个基于吡啶配体还原的峰具有明显的催化特性.少量水的加入能进一步增加催化电流强度,而三联吡啶钴配合物的催化增强效果更加显著.在变扫速条件下将电流密度对扫速平方根进行归一化处理,发现无论在干燥环境还是少量加水环境下,两种催化剂的归一化电流密度均随扫速降低而明显增强,证明了催化剂具有电催化特性.推测水的催化增强作用可能与质子化电催化过程活性中间体有关.恒电位电解结果说明电催化产物以一氧化碳为主.基于上述研究,我们构建了光电化学三电极体系,以单晶硅片为工作电极,研究了在光照环境下这两种配合物催化还原二氧化碳的电流密度和电解产物分布情况.研究发现,催化剂对二氧化碳仍具有催化活性,光电压为400 m V.不同于硅线电极加水导致产氢,改用少量甲醇做质子源后,光电流强度进一步增强,竞争性产氢受到了抑制,从而使一氧化碳的法拉第效率得到显著提高,分别优化为94%和83%,并且光电流在14h内保持稳定.推测甲醇质子源的催化增强作用可能是与改变光电极液接界面传质动力学过程有关.     

Organic molecules involved in Cu-based electrocatalysts for selective CO2 reduction to C2+ products

Electrocatalytic carbon dioxide (CO₂) reduction reaction (CO₂RR) is a promising process to mitigate the environmental issues caused by CO₂, as well as to produce valuable multicarbon (C₂₊) products. Significant progresses have been made to explore highly efficient Cu-based electrocatalysts for CO₂RR in recent years. Adding organic molecules into electrocatalytic systems can tune the CO₂ interaction with the electrocatalysts for CO₂RR, therefore, the final C₂₊ products, which are not solely achieved by inorganic modification. In this review, we will summarize the recent progress of the organic molecules participation in CO₂ electroreduction to C₂₊ products on Cu-based electrocatalysts. The applied organic molecules are reviewed based on the heteroatoms (N and S), with the emphasis on their roles in activity and selectivity toward C₂₊ products. A perspective on the application of organic molecules for efficient and selective CO₂RR has been provided.     

超临界条件下负载型配合物催化剂Cu2(μ-OEt)2/SiO2合成碳酸二甲酯的反应性能

采用表面改性和离子交换相结合的方法制备了负载型配合物Cu2(μ-OEt)2／SiO2催化剂，用化学分析、IR、TPD和超临界反应技术考察了催化剂的表面构造、CO2和甲醇在催化剂上的化学吸附及超临界条件下的反应性能，结果表明：双核配合物Cu2(μ-OEt)2中金属离子Cu^2 与载体SiO2表面O^2-以双齿配位键合，配体以桥基形式连接双金属离子形成双核物种Cu2(μ-OEt)2；CO2在催化剂表面存在桥式和乙氧碳酸酯基两种吸附态，其中乙氧碳酸酯基吸附态是生成DMC的关键物种；CH3OH在催化剂上只有一种分子吸附态．催化剂用量、反应压力、反应温度和反应时间对甲醇的转化率都有不同程度的影响，在超临界条件下，DMC的选择性为100％，甲醇的转化率超过4％．     

有机物在超临界二氧化碳中的无限稀释扩散系数的测定

利用经改造的超临界流体色谱仪测定不同温度和压力下苯、丙酮在超临界二氧化碳中的无限稀释扩散系数,开发出一个针对本科高年级学生的开放性实验,旨在加深学生对超临界流体及其性质的理解。在熟悉超临界流体色谱仪的工作原理、结构及其应用并掌握其操作方法的基础上,拓展学生视野和思维的深度及广度,提升学生的实验操作技能,培养高素质化学人才。