曹雨微[1],2,刘远2,孔会民1,2,岳萍2,唐大才2,林彦军1,[3]

以MgCl2为晶面调控剂，利用水热法对氢氧化镁（MH）的（001）晶面选择性生长进行调控，研究了晶面调控剂浓度、反应温度、反应时间等因素对MH颗粒的溶解和结晶作用。调控后产品各晶面的XRD衍射峰强度I001/I101和I001/I110较原料分别提高了214.30%和307.45%，百吨级中试产品的I001/I101和I001/I110较原料分别提高了84.08%和112.99%。采用XRD、FE-SEM、TEM、FTIR、粒度分析仪对MH产品的形貌、结构进行了表征，并对调控机理进行了研究。结果表明，MgCl2可以在水热体系中促进MH的（001）晶面选择性生长。一方面，MgCl2作为强酸弱碱盐降低了体系pH值，同时Cl－可以通过电荷中和效应使MH发生进一步加速溶解。另一方面，MgCl2提供的Cl－作用于MH的结晶过程，通过促进MH边缘生长，强化了（001）晶面的生长。     

应用ICP-AES法测定铁矿石中SiO_2,MnO,CaO,MgO,TiO_2,Al_2O_3和P

介绍了应用ICP-AES法同时测定铁矿石中SiO2,MnO,CaO,MgO,TiO2,Al2O3和P七个元素的方法,首先选择溶样试剂和分析谱线,再进行仪器分析参数的设置和优化,结果直接使用标准样品制作工作曲线表示。方法中SiO2,MnO,CaO,MgO,Al2O3,TiO2,P的检出限分别为0.15,0.005,0.16,0.04,0.06,0.004,0.19μg/mL,相对标准偏差小于5.0%,基本上满足了铁矿石中该七个元素测定的要求,与标准样品对照,结果令人满意。     

新化合物2K2O,2CaO,5.2Nb2O5

在K_2O-Nb_2O_5-CaO三元系统中发现存在化合物2K_3O·2CaO·5.2Nb_2O_5。用粉晶衍射法获得了该化合物的粉晶衍射图谱,该化合物为一致熔融化合物,熔点为1280℃,晶体呈无色。透明、针状,25℃时测量密度D_m=4.51g/cm~2,用单晶测得晶胞参数a=b=12.524(4)(?),c=3.926(2)(?),属四方晶系,空间群为P(4/m)bm,该化合物晶体结构属钨青铜结构类型,结晶学分子式为K_4Ca_2Nb_(?.4)Nb_(10)O_(30)。     

CO2,H2,N2在MDEA水溶液中的溶解 度

ＣＯ２、Ｈ２、Ｎ２在ＭＤＥＡ水溶液中的溶解度徐国文张成芳钦淑均（华东理工大学无机化工研究所，上海２００２３７）关键词：ＣＯ２Ｈ２Ｎ２溶解度ＭＤＥＡ１前言国外报道的ＣＯ２溶解度数据［１～９］，布点稀疏，无法满足工程计算及动力学研究之需。王挹薇等采...     

纳米Al2O3,ZnO,CeO2,ZrO2对低温无铅熔块性能的影响

采用正交实验法,研究了在无铅基础熔块中,添加纳米Al2O3,ZnO,CeO2,ZrO2对其抗弯强度、维氏硬度及化学稳定性等性能的影响。结果表明:外加纳米氧化铝等可使无铅熔块抗弯强度提高30%,化学稳定性提高60%～80%,硬度提高10%左右。     

1H,1H,2H,2H-全氟烷基丙烯酸酯的自压催化合成

以丙烯酸钾盐和全氟烷基乙烯基加成物(PFOEI)为原料,在反应体系自身产生的压力下,催化合成1H,1H,2H,2H-全氟烷基丙烯酸酯,考察了在原料配比为,n(PFOEI):n(丙烯酸钾):n(叔戊醇):n(PIC):n(阻聚剂)=1:1.5:20:0.06:0.05、反应时间为9 h下,溶剂、相转移催化剂和反应温度对酯...     

H2, CO, N2, O2和CH4在碳膜中的扩散

Diffusion of pure H2, CO, N2,O2 and CH4 gases through nanoporous carbon membrane is investigated by carrying out non-equilibrium molecular dynamics （NEMD） simulations. The flux, transport diffusivity and activation energy for the pure gases diffusing through carbon membranes with various pore widths were investigated. The simulation results reveal that transport diffusivity increases with temperature and pore width, and its values have a magnitude of 10^-7 m^2·s^-1 for pore widths of about 0.80 to 1.21 nm at 273 to 300 K. The activation energies for the gases diffusion through the membrane with various pore widths are about 1-5 kJ·mol^-1, The results of transport diffusivities are comparable with that of Rao and Sircar （J. Membr. Sci., 1996）, indicating the NEMD simulation method is a good tool for predicting the transport diffusivities for gases in porous materials, which is always difficult to be accurately measured by experiments.     

Computer simulation of diffusion within and through membranes using nonequilibrium molecular dynamics

A novel nonequilibrium molecular dynamics (NEMD) method introduced in 1994 and its recent application to investigations of the transport properties of gases and dense fluids within strongly inhomogeneous pore structures are reviewed. In this technique molecular simulations are conducted under realistic nonequilibrium (experimental) conditions thus enabling direct insight into the underlying microscopic processes taking place during transport within pores. The case studies reviewed in this paper establish the versatility and scope of the NEMD technique and also demonstrate its significant advantages over prior molecular simulation procedures as a tool to assist in the design and tailoring of novel nanopore systems.     

Studies on Gas Transport Through Dry Cellulose Acetate Membranes Prepared by Solvent Exchange Technique

Abstract

The mechanism of gas transport through pores on the surface of dry cellulose acetate membranes under pressure was identified for membranes prepared by the solvent exchange technique using pure gas permeation rate data. The pure gases were helium, methane and carbon dioxide. The variables Involved in the membrane preparation are the shrinkage temperature, the first solvent, the second solvent and the combinations thereof. Different conditions of membrane preparation produce different pore sizes. Depending on this pore size, one of the following mechanisms becomes dominant: Knudsen, surface and size exclusion.     

Surface wettability effect on fluid transport in nanoscale slit pores

The surface wettability effect on fluid transport in nanoscale slit pores is quantitatively accessed by using non‐equilibrium molecular dynamics (NEMD) simulation incorporating with density functional theory (DFT). In particular, the slip lengths of benzene steady flows under various wetting conditions are computed with NEMD simulations and a quasi‐general expression is given, while the structural properties are investigated with DFT. By taking into account the inhomogeneity of fluid density inside pore, we find that the conventional flux enhancement rate is associated with both the molecule slipping and geometrical confinement, and it becomes drastically high in solvophobic pores especially when the pore size is of several fluid diameters. In good agreement with experimental results, we further show that the wettability effect competes with pore size effect in determining the flux after pore inner surface modification, and a high flux can be achieved when the deposited layer is solvophobic yet thin. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1704–1714, 2017     

Selective transport of CO2, CH4, and N2 in coals: insights from modeling of experimental gas adsorption data

Selective adsorption and transport of gases in coal are important for natural gas recovery and carbon sequestration in depleted coal seams for environmental remediation. Gases are stored in coal mainly in the adsorbed state. In this study, the interaction energies of adsorbates (CO₂, CH₄, and N₂) and micropores with various widths are investigated using a slit-shape pore model. The experimental adsorption rate data of the three gases conducted on the same coal sample are numerically simulated using a bidisperse model and apparent diffusivities of each adsorbate in the macropore and micropore are determined. The results indicate that the relative adsorbate molecule size and pore structure play an important role in selective gas adsorption and diffusion in micropores. Generally, the microporous coals diffusion is activated and the apparent micropore diffusivities of gases in coal decrease strongly with increase in gas kinetic diameters. Apparent micropore diffusivity of CO₂ is generally one or two order of magnitude higher than those of CH₄ and N₂ because their kinetic diameters have the relation: CO₂ (0.33 nm)<N₂ (0.36 nm)<CH₄ (0.38 nm). In contrast to theoretical values, apparent macropore diffusivity of CO₂ is also larger than those of CH₄ and N₂, suggesting that coal has an interconnected pore network but highly constricted by ultra micropores with width <∼0.6 nm. It is also found that the apparent diffusivity strongly decreases with an increase in gas pressure, which may be attributed to coal matrix swelling caused by gas adsorption. Therefore, rigorous modeling of gas recovery and production requires consideration of specific interaction of gas and coal matrix.     

Effects of Thermal Treatment on Gas Transport Through Porous Silica Membranes

Abstract

The effects of thermal treatment from 180°C to 1150°C on the gas transport properties of porous silica membranes were systematically studied for various gases. The permeance of all gases, except for CO₂, has a maximum at 800°C. The CO₂ permeance was constant from 180°C to 600°C and then decreased monotonically. Membranes thermally treated at 1150°C did not exhibit any gas permeation because of pore collapse. The gas transport behavior follows a combination of Knudsen diffusion and surface diffusion for all gases tested except for carbon dioxide. The permeation of carbon dioxide is strongly affected by capillary condensation. We propose a new transport model composed of two components; that is, the Knudsen diffusion factor, α, and the surface diffusion factor, β. A transition was observed for α and β at around 800–900°C, which is close to the strain point of the membrane. This transition treatment temperature can be correlated with the changes in gas permeance. The model allows qualitative evaluation of gas transport through porous membranes regardless of their actual microporous structures.     

炭化条件对多孔炭膜性能的影响

以石油沥青为原料,采用无粘结剂成型制备多孔炭膜,考察了炭化条件对炭膜的Ｈ２和Ｎ２气体渗透率和理想分离系数的影响,并用压汞法表征了炭膜的孔径分布,结果表明：炭化温度是影响炭膜性能的关键因素,制备的炭膜具有均匀性孔径分布,平均孔径为１５３ｎｍ。     

稀四氟化碳气体混合物传递性质的确定(英文)

In our previous work, we calculated transport properties of pure gaseous polyatomic carbon tetrafluoride (CF4) and five equimolar binary gas mixtures of CF4 with noble gases through inversion technique. The present work is a continuation of our studies on determining the transport properties of binary gas mixtures CF4 with some gases including three diatomic molecules CO, N2, and O2, a linear polyatomic CO2, and two non-linear polyatomic molecules SF6 and CH4. The Chapman-Enskog and Vesovic-Wakeham methods as well as inversion procedure are used to determine the viscosities, diffusivities, and thermal conductivities, which deviates from the literature values within 1%, 4%, and 5%, respectively.     

PREPARATION AND TESTING OF CARBON/SILICALITE-1 COMPOSITE MEMBRANES

Methods for preparation of carbon/silicalite-1 composite membranes have been developed. First, silicalite-1 membranes were prepared by in-situ hydrothermal synthesis on both porous alumina and metal disks. Preparation of the carbon/silicalite-1 composite membranes was accomplished by polymerizing furfuryl alcohol on the surface of the silicalite-1 membrane, followed by carbonizing the polymer layer in an inert atmosphere at 773 K. The pure silicalite-1 membrane showed no selectivity for single gases, indicating the presence of intercrystalline diffusion and viscous flow as the dominant transport mechanism. The carbon/zeolite composite membrane exhibited ideal selectivities for He/N₂, CO₂/N₂, and N₂/CH₄ of 11.99, 17.12, and 3.58 at room temperature. No permeation of n-butane and i-butane for the composite membrane was detected up to temperatures of 453 K, indicating that the pore size for the composite membrane was approximately 0.4 nm. By carefully oxidizing the carbon layer in air at 623 K, the pore size of the composite membrane was adjusted such that n-butane permeation could be detected. No permeation of i-butane was apparent, suggesting that the pore size of the composite membrane had been enlarged to approximately 0.5 nm. Further oxidation of the carbon layer produced a finite n-/i-C₄H₄ ideal selectivity, indicating that the pore size of the membrane was now larger than 0.55 nm. Therefore, selective oxidation of the carbon layer can be used to control the pore size of the composite membrane.