连锁结构金属-有机骨架材料强化甲烷吸附的分子模拟研究

A systematic molecular simulation study was performed to investigate the effect of catenation on methane adsorption in metal-organic frameworks (MOFs). Four pairs of isoreticular MOFs (IRMOFs) with and without catenation were adopted and their capacities for methane adsorption were compared at room temperature. The pre-sent work showed that catenation could greatly enhance the storage capacity of methane in MOFs, due to the for-mation of additional small pores and adsorption sites formed by the catenation of frameworks. In addition, the simulation results obtained at 298 K and 3.5 MPa showed that catenated MOFs could easily meet the requirement for methane storage in porous materials.     

分子动力学模拟研究盐离子对十二烷基硫酸钠胶束溶液中亲水亲油协调机制的影响

The presence of salt has a profound effect on the size, shape and structure of sodium dodecyl sulfate (SDS) micelles. There have been a great number of experiments on SDS micelles in the presence and absence of salt to study this complex problem. Unfortunately, it is not clear yet how electrolyte ions influence the structure of micelles. By describing the compromise between dominant mechanisms, a simplified atomic model of SDS in presence of salt has been developed and the molecular dynamics (MD) simulations of two series of systems with different concentrations of salt and charges of ion have been performed. Polydispersity of micelle size is founded at relatively high concentration of SDS and low charge of cation. Although the counter-ion pairs with head groups are formed, the transition of micelle shape is not observed because the charge of cation is not enough to neutralize the polar of micelle surface.     

蛋白质在温度响应性PNIPAAm接枝硅胶表面吸附和解吸过程:分子模拟和实验研究(英文)

Poly(N-isopropylacrylamide)(PNIPAAm) grafted onto silica,which may be used for reverse phase chromatography(RPC),was simulated and synthesized for protein separation with temperature-triggered adsorption and desorption.Molecular dynamics simulation at an all-atom level was performed to illustrate the adsorption/desorption behavior of cytochrome c,the model protein,on PNIPAAm-grafted-silica,a temperature responsive adsorbent.At a temperature above the lower critical solution temperature(LCST),the PNIPAAm chains aggregate on the silica surface,forming a hydrophobic surface that is favorable for the hydrophobic adsorption of cytochrome c,which has a high exposure of hydrophobic patches.At temperatures below the LCST,the PNIPAAm chains stretch,forming hydrophilic surface due to hydrogen bonding between PNIPAAm and surrounding water.Desorption of cytochrome c on the PNIPAAm-grafted-silica surface occurs as a result of competition with water,which forms hydrogen bonds with the protein.The conformational transitions of both cytochrome c and PNIPAAm are monitored,providing molecular insight into this temperature-responsive RPC technique.PNIPAAm-grafted-silica beads were synthesized and used for the adsorption and desorption of cytochrome c at approximately 313 K and 290 K,respectively.The experimental results validate the molecular dynamics simulation.In comparison to conventional RPC,using temperature as a driving force for RPC reduces the risk of protein denaturation caused by exposure to chaotropic solvents.Moreover,it simplifies the separation process by avoiding the buffer exchange operations between the steps.     

用定标粒子理论研究不同温度下2-甲基-2-丙醇与腈二元液相混合物的超额热力学参数和超音速度理论估值(英文)

Density, ρ, ultrasonic speed, u, and viscosity, η, of binary mixtures of 2-methyl-2-propanol (2M2P) with acetonitrile (AN), propionitrile (PN) and butyronitrile (BN) including those of pure liquids are measured over the entire composition range at temperatures 298.15, 303.15 and 308.15 K. From these experimental data, the excess available volume, E a V , excess free volume, E f V , excess isothermal compressibility, E T β , excess thermal expansion coefficient, E α , and excess internal pressure, E i π , are calculated. The variation of these properties with composition and temperature are discussed in terms of molecular interactions between unlike molecules of the mixtures. It is found that the values of E a V , E f V , E T β and E α are positive and those of E i π are negative for all the mixtures at each temperature studied, indicating the presence of weak interactions between 2M2P and AN/PN/BN molecules. The variations of E a V , E f V , E T β , E α and E i π values with composition indicate that the interactions in these mixtures follow the order: ANPNBN, i.e., the 2M2P-nitrile interaction decreases with the increase of alkyl chain length in these nitrile molecules. In addition, the theoretical ultrasonic velocity is calculated using the scaled particle theory and compared with the experimental values.     

萃取精馏和精馏结合分离混合二氯苯的模拟及试验研究

采用三对角距阵法模拟混合二氯苯萃取分离结果,考察物料进料位置、进料量、回流比及塔板数对分离过程的影响,优化分离过程的工艺条件,在回流比R=4:1条件下,原料经萃取精馏和精馏结合分离,一次可得到99.5%以上的邻二氯苯和89.7%以上的对二氯苯,得率分别可达80%和97.9%以上,邻二氯苯分离过程能量消耗仅为精馏方法的28.7%;以二苯胺为萃取剂,进行萃取精馏和精馏试验,当溶剂比为1:1,回流比R=4时,原料液经萃取精馏和精馏分离后,一次可得到99.5%以上的邻二氯苯和86.7%的对二氯苯,得率分别达到72%和83.5%,试验和模拟计算结果基本一致,为进一步放大试验提供依据.     

CH4在PVDF中渗透行为及机理的分子模拟研究

采用巨正则蒙特卡洛法(GCMC)和分子动力学法(MD)相结合的方法模拟研究了典型气体CH4在聚偏氟乙烯(PVDF)中的吸附扩散行为,探讨了温度及压力对气体吸附扩散能力的影响,分析了CH4在PVDF中的吸附位点及扩散轨迹.模拟结果表明,CH4在PVDF中的溶解系数、渗透系数随温度的升高先增大后减小,随压力的升高而增大;扩...     

表面粗糙度及氢对S32750 SDSS在模拟海水中腐蚀行为的影响

对于富氢服役工况下的钢材结构,其服役时间以及服役性能都与其表面粗糙度有很大关系,但是目前对于S32750超级双相不锈钢富氢环境下的表面粗糙度研究较少。为此采用开路电位（OCP）测试法、电化学阻抗谱（EIS）等方法,研究了表面粗糙度Ra分别为0.244、0.178、0.124、0.054μm的S32750 SDSS充氢后在3.5%NaCl溶液中的腐蚀行为。结果表明：随着表面粗糙度Ra的增大,开路电位越负,容抗弧直径越小,耐蚀性大幅降低。表面粗糙度越大,在富氢环境下试件表面发生的点蚀越严重。     

数值模拟在研究高分子材料结构与性能方面的应用

介绍了高分子材料结构与性能方面计算机数值模拟的种类、常用方法、研究的主要方向、趋势、涉及的材料等。在简略介绍对高分子材料结构的分子模拟方法的同时,重点介绍了在高分子材料宏观性能计算机模拟中,有限元方法应用的主要领域及其有关问题。并以高分子共混物中添加相粒子的不同分布状态下组元模型的选取以及建立为例,介绍了采用有限元方法研究高分子材料的相关性质时如何初步建立与实际较为相符的模型。     

噻吩及其与异辛烷二元混合物在介孔炭材料CMK-3中吸附的蒙特卡罗模拟北大核心

建立了介孔炭材料CMK-3的分子模型,并采用巨正则蒙特卡罗方法模拟了噻吩分子及其与异辛烷二元混合物在介孔炭材料CMK-3中298 K下的吸附等温线和吸附分布情况以及该二元混合物在介孔炭材料CMK-3中的等量吸附热。结果表明,噻吩分子在介孔炭材料CMK-3表面的吸附主要为多分子层物理吸附,且集中在粗炭棒表面。在二元混合物的吸附中,噻吩和异辛烷在介孔炭材料CMK-3中存在竞争吸附过程,异辛烷的吸附能力强于噻吩,且异辛烷主要聚集在离粗炭棒较近的位置,而噻吩主要集中在离粗炭棒相对较远的位置和细炭棒上。     

分散红73和分散蓝183及其混合物在超临界二氧化碳中溶解度的测定与关联(英文)

The solubility of disperse dyes and their mixture in supercritical carbon dioxide is an important property in study and development of supercritical fluid dyeing technology. In this study, solubilities of C.I. Disperse Red 73, C.I. Disperse Blue 183 and their mixture in supercritical CO2 are measured at temperatures from 343.2 to 383.2 K and pressures from 12 to 28 MPa with a static recirculation method. Under the experimental conditions for the binary (C.I. Disperse Red 73 + CO2 or C.I. Disperse Blue 183 + CO2) and ternary (C.I. Disperse Red 73 + C.I. Disperse Blue 183 + CO2) systems, the solubilities increase with pressure. The solubility of C.I. Disperse Blue 183 decreases with the increase of temperature when the pressure is lower than 16 MPa, and the trend is opposite when the pressure is higher than 16 MPa. However, there is no crossover pressure for C.I. Disperse Red 73. The solubilities are also affected by molecular polarity of dyes. The co-solvent effect exhibited in the dissolving process of mixed dyes promotes their disso-lution in supercritical CO2. The experimental data of solubilities of C.I. Disperse Red 73, C.I. Disperse Blue 183, and their mixture are correlated with the Chrastil model and Mendez-Santiago/Teja model. The former is more accurate.     

Separation of CO2/N2 Gas Mixture through Carbon Membranes: Monte Carlo Simulation

Abstract

Monte Carlo simulation method is employed to investigate separation behavior of gas mixture composed of carbon dioxide and nitrogen through a model carbon membrane under the different conditions. The simulation gives insight into the separation mechanism to a certain extent, which is based on the loading and diffusion of carbon dioxide and nitrogen in the carbon membrane with different pore size. The simulation results indicate that the carbon dioxide can be adsorbed on the surface of membrane wall more strongly, whereas the diffusion rate of nitrogen is more prominent. When the separation condition alters, the influence of the two main factors mentioned above on transport of gas molecules in membranes becomes different. Therefore, the equilibrium selectivity of nitrogen and carbon dioxide changes correspondingly.     

In Silico Screening of Metal-Organic Frameworks for Formaldehyde Capture with and without Humidity by Molecular Simulation

Capturing formaldehydes (HCHO) from indoor air with porous adsorbents still faces challenges due to their low capacity and poor selectivity. Metal-organic frameworks (MOFs) with tunable pore properties were regarded as promising adsorbents for HCHO removal. However, the water presence in humid air heavily influences the formaldehyde capture performance due to the competition adsorption. To find suitable MOFs for formaldehyde capture and explore the relationship between MOFs structure and performance both in dry air and humid air, we performed grand canonical Monte Carlo (GCMC) molecular simulations to obtain working capacity and selectivity that evaluated the HCHO capture performance of MOFs without humidity. The results reveal that small pore size (~5 Å) and moderate heat of adsorption (40–50 kJ/mol) are favored for HCHO capture without water. It was found that the structure with a 3D cage instead of a 2D channel benefits the HCHO adsorption. Atoms in these high-performing MOFs should possess relatively small charges, and large Lennard-jones parameters were also preferred. Furthermore, it was indicated that Henry’s constant (K_H) can reflect the HCHO adsorption performance without humidity, in which the optimal range is 10⁻²–10¹. Hence, Henry’s constant selectivity of HCHO over water (SK_H HCHO/H₂O) and HCHO over mixture components (H₂O, N_2, and O₂) was obtained to screen MOFs at an 80% humidity condition. It was suggested that SK_H for the mixture component overestimates the influence of N₂ and O₂, in which the top structures absorb a quantity of water in GCMC simulation, while SK_H HCHO/H₂O can efficiently find high-performing MOFs for HCHO capture at humidity in low adsorption pressure. The ECATAT found in this work has 0.64 mol/kg working capacity, and barely adsorbs water during 0–1 bar, which is the promising candidate MOF for HCHO capture.     

分子模拟技术在气体膜分离研究中的应用

回顾了分子模拟技术在气体膜分离领域的应用，介绍了各种模拟方法的特点，阐述了具体的应用范围、存在的问题及发展趋势。表明分子模拟在定性分析气体与膜材料的亲和性、预测渗透系数和分离因子方面有一定价值，但离定量预测和分析还有一定距离，非平衡分子动力学是适用于气体膜分离研究的方法，其研究还处于初期阶段。     

一维直孔道MOFs对CH4/N2和CO2/CH4的分离

非常规天然气未来可以作为常规天然气的有效补充,其中低浓度煤层气和生物质燃气分别需要脱除大量的N₂ 和CO₂以达到富集和纯化CH₄的目的。本研究针对CH₄/N₂这一对较难分离的气体组合,选取了具有一维菱形孔道的MOFs材料Cu(INA)₂作为吸附剂,将合成的样品做了XRD和TG表征,测试了纯气体CO₂、CH₄和N₂的吸附曲线,利用巨正则系综蒙特卡罗(GCMC)分子模拟和理想吸附溶液理论(IAST)计算了气体的吸附热和该材料对于CH₄/N₂和CO₂/CH₄的吸附选择性系数;3 MPa压力下制备的颗粒样品填装吸附分离装置,进行了混合气体CH₄/N₂ (50%/50%)和CO₂/CH₄ (50%/50%)的穿透试验,分离的结果显示,Cu(INA)₂不仅高选择性地吸附CH₄/N₂混合物中的CH₄(S_CH4/N2=10),而且对CH₄/N₂的分离效果优于CO₂/CH₄。     

Molecular Simulation on Microstructure of Ionic Liquids in Capture of CO_2

Molecular dynamic simulation is used to study the microstructure of four kinds of ionic liquids (ILs), [Emim]PF6, [Emim][Tf2N], [PC6,6,6,14]PF6 and [PC6,6,6,14][Tf2N] in the capture process of CO2. Radial distribution function (RDF) and spatial distribution function (SDF) are used to analyze the microscopic properties of these systems. The calculated results show that the space distribution of CO2 around ILs determines the capability of ionic liquids for capturing CO2. Based on the analysis of SDF, CO2 and PF6- are overlapped partially around [Emim]+ in [Emim]PF6-CO2 mixture. When the anion is [Tf2N]-, cations are mainly distributed on one side of [Tf2N]- near N atom, and CO2 is concentrated on two sides near the fluoroalkylgroup (?CF3), and there is little overlapped district between cation and CO2. In [PC6,6,6,14]PF6-CO2 mixture, layered structure is found and CO2 is much nearer to PF6- than [PC6,6,6,14]+. Based on the analysis of RDF, in the phosphonium-based ILs, the highest distribution densities of anions and CO2 around cations are about 6 and 3 times as their average ones respectively, while in the imidazolium-based ILs, they are about 3 and 2 respectively, this means that the distributions of CO2 and anions around the imidazolium-based ILs are more evenly distributed than those around the phosphonium-based ILs.     

基于Aspen Plus粗甘油混合物的分离工艺模拟

采用化工流程模拟软件Aspen Plus,以NRTL热力学模型对粗甘油混合物的分离过程进行了模拟。流程采用闪蒸分子蒸馏相结合的技术,考察了压强和温度对分离效果的影响。模拟优化的结果为:闪蒸的真空度为6.7 kPa,除去10%的水,其中携带甘油的含量为0.5%;分子蒸馏的真空度为420 Pa,温度为160℃,蒸出的甘油蒸汽的量为717.44 kg/h,其中甘油的质量分数为95%(W),一级产品总量为626.22 kg/h,甘油纯度为99.8%(W),二级产品总量为57.96 kg/h,甘油纯度为95.8%(W)。甘油总收率达到94.6%(W)。     

金属-有机骨架材料CO2捕获性能的大规模计算筛选

全球性温室效应形势的日趋严重，迫切需要研究和开发可用于CO₂捕集的高性能材料。对于含有双铜船桨型片段(Cu₂(COO)₄)的MOF材料，因其结构中含有配位不饱和的Cu金属位点，在低压区域的CO₂捕获方面展现出优异的性能。目前，大规模计算筛选工作主要是基于传统的分子力场，无法对此类Cu-MOFs中主客体分子间的相互作用进行准确描述。基于量化计算获得的精确分子力场，利用Monte Carlo分子模拟方法考察了常温常压条件下763个基于Cu-OMS的MOF材料对CO₂存储和CO₂/N₂的分离行为。不仅筛选出潜在的高性能材料，而且揭示出了材料的结构与其性能之间的关系和具有优良性能的材料结构特征，可为面向特定应用的新材料设计和合成提供理论参考。     

Residual Interactions of LL-37 with POPC and POPE:POPG Bilayer Model Studied by All-Atom Molecular Dynamics Simulation

LL-37 is a membrane-active antimicrobial peptide (AMP) that could disrupt the integrity of bacterial membranes due to its inherent cationic and amphipathic nature. Developing a shorter derivative of a long peptide such as LL-37 is of great interest, as it can reduce production costs and cytotoxicity. However, more detailed information about the residual interaction between LL-37 and the membrane is required for further optimization. Previously, molecular dynamics simulation using mixed all-atom and united-atom force fields showed that LL-37 could penetrate the bilayer membrane. This study aimed to perform all-atom molecular dynamics simulations, highlighting the residual interaction of LL-37 with the simplest model of the bacterial membrane, POPE:POPG (2:1), and compare its interaction with the POPC, which represents the eukaryotic membrane. The result showed leucine–leucine as the leading residues of LL-37 that first contact the membrane surface. Then, the cationic peptide of LL-37 started to penetrate the membrane by developing salt bridges between positively charged amino acids, Lys–Arg, and the exposed phosphate group of POPE:POPG, which is shielded in POPC. Residues 18 to 29 are suggested as the core region of LL-37, as they actively interact with the POPE:POPG membrane, not POPC. These results could provide a basis for modifying the amino acid sequence of LL-37 and developing a more efficient design for LL-37 derivatives.     

金属有机骨架材料在吸附分离CH_4/N_2中的研究进展

简单介绍了金属有机骨架材料的发展,主要从甲烷选择型MOF吸附剂、氮气选择型MOF吸附剂2个方面综述了金属有机骨架材料在CH4/N2分离中的研究进展,并对MOFs吸附剂与传统吸附剂的CH4/N2分离性能进行了比较,同时展望了MOFs吸附剂在低品质煤层气脱N2过程的应用前景。