液膜分离技术在生化产品提取中的应用进展

介绍了液膜的基本概念、分类和分离机理。与传统的生化产品分离提纯技术相比,液膜分离技术具有简便、高效且成本低的特点。综述了液膜分离技术在抗生素和氨基酸提取中的应用进展,如青霉素、半合成青霉素、头孢菌素、麦白霉素、苯丙氨酸、亮氨酸和谷氨酸的提取,并指出其发展前景。     

直接醇类燃料电池工作原理及研究进展

综述了直接醇类燃料电池的工作原理及最新进展,简述了此类电池存在的主要问题及关键技术,对发展质子交换膜和电催化剂技术提出了建议。     

A photocatalytic membrane reactor for gas-phase reactions using porous titanium oxide membranes

Photocatalytic membrane reactors using porous titanium oxide membranes having pore sizes of several nanometers were utilized for a gas-phase reaction of methanol. Air mixed with methanol (MeOH) vapor, the concentration of which was controlled in the range of 500–6000 ppm, was fed to the photocatalytic membrane reactor in the range of 50–500 cm³/min using several types of flow patterns. Photocatalysis with membrane permeation resulted in a large decomposition rate, compared to photocatalysis without membrane permeation. The characteristics of the reaction such as decomposition ratio of MeOH, the conversion of the decomposed MeOH to CO₂ and H₂O were found to be a function of the residence time in the reactor. The photocatalytic reaction was analyzed based on pseudo-first-order kinetics to ascertain its simplicity, and the fitted curves were found to be in a relatively good agreement with the experimental data. Apparent rate constants with and without membrane permeation were 2.5 and 1.5×10⁻⁶ m s⁻¹, respectively, indicating that the performance of the photocatalytic reaction system with membrane permeation was enhanced.     

分体式质子交换膜燃料电堆的膜加湿实验

在已开发的分体式质子交换膜燃料电池电堆基础上,对膜（Nafion115）加湿器子系统进行了详细的研究,揭示了质子交换膜燃料电池膜加湿方法的特性.初步分析了膜加湿的原理,并在不同操作条件下,定量地对膜透过水量与反应气体的润湿程度进行了测量,得到了Nafion115膜加湿器对电堆的润湿性能.发现操作温度在50～70℃之间,加湿速率最强;随着反应气体流量的增大,加湿速率呈非线性增加,但润湿程度反而降低;增加质子交换膜面积会增大反应气体的相对湿度,而加湿速率将下降;较高反应气体压力下不利于加湿.在适当的膜加湿器工况下,当电流密度为2.1A•cm^-2时,电堆最大功率密度可超过1.2W•cm^-2.     

Rh/γ-Al2O3 Catalytic Layer Integrated with Sol–Gel Synthesized Microporous Silica Membrane for Compact Membrane Reactor Applications

An efficient and compact catalytic membrane reactor for reforming of CH₄ was developed by integrating a hydrogen perm-selective silica membrane with an Rh/-Al₂O₃ catalyst layer. The catalytic layer was sandwiched between the outer surface of the -Al₂O₃ support tube and the silica membrane with an aim of improving the heat and mass transfer rates through the system and to simplify the reactor geometry. The system showed improved efficiency for reforming of CH₄ at comparatively lower operating temperatures and steam to C molar ratios than the conventional fixed-bed steam reforming systems. Under optimized conditions, a nearly 25-30% improvement from the equilibrium conversion level was achieved as a result of abstraction of hydrogen from the product stream by the silica membrane integrated with the catalyst layer. The performance of the system was evaluated as a function of various process parameters. Because of the compactness and efficiency, the present system emerges as a promising alternative to the conventional membrane reactors, which possess separate catalytic and membrane units.     

Metal cation removal by P(VC-r-AA) copolymer ultrafiltration membranes

A series of amphiphilic copolymers containing poly(vinyl chloride-r-acrylic acid) (P(VC-r-AA) ) was synthesized and used to prepare membranes via a nonsolvent induced phase separation method. The prepared membranes were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, and water contact angle and zeta potential measurements. The copolymer P(VC-r-AA) chains did not dissolved in a coagulation bath, indicating that the AA segments were completely retained within the membrane. Enriching degree of AA segments in surface layer was 2 for copolymer membrane. In addition, the introduction of AA segments made the membrane electronegative and hydrophilic so that the membrane was sensitive to the solution pH. The fouling resistance, adsorption of Cu(II), Cr(III) and Ce(IV) ions and the desorption properties of the membranes were also determined. The copolymer membranes exhibited good antifouling performance with a fouling reversibility of 92%. The membranes also had good adsorption capacities for Cu(II), Cr(III) and Ce(IV) ions. The optimal pH for Cu(II) adsorption was 6 and the copolymer membrane has potential applications for low concentration Cu(II) removal.

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面向油水分离的无机膜制备及应用进展

膜技术是处理含油污水及含水油液的有效分离方法。无机膜材料由于可调变的表面性质和良好的稳定性,即使在苛刻的条件下,在分离油水方面表现出优异的分离性能。本文首先阐述了设计与制备油水分离膜的理论基础,包括分离过程中压力驱动力和膜表面特性对膜通量和选择性的影响;然后综述了当前国内外用于油水分离的无机膜的制备及其应用进展,重点介绍分子筛膜、金属氧化物/金属氢氧化物膜和氧化石墨烯膜等的研究,分析了在不同油水混合物中研究者们调控无机膜表面性能的策略,提出膜表面润湿性和膜结构是提高膜分离效率和抗污染性的关键;最后指出抵制含大量表面活性剂、碱液及有机聚合物种的乳化油对膜造成污染,是无机膜亟需解决的问题,并展望了无机膜在分离油水方面的发展方向。     

Simulation of autothermal reforming in a staged‐separation membrane reactor for pure hydrogen production

Steam methane reforming with oxygen input is simulated in staged‐separation membrane reactors. The configuration retains the advantage of regular membrane reactors for achieving super‐equilibrium conversion, but reaction and membrane separation are carried out in two separate units. Equilibrium is assumed in the models given the excess of catalyst. The optimal pure hydrogen yield is obtained with 55% of the total membrane area allocated to the first of two modules. The performance of the process with pure oxygen input is only marginally better than with air. Oxygen must be added in split mode to reach autothermal operation for both reformer modules, and the oxygen input to each module depends on the process conditions. The effects of temperature, steam‐to‐carbon ratio and pressure of the reformer and the area of the membrane modules are investigated for various conditions. Compared with a traditional reformer with an ex situ membrane purifier downstream, the staged reactor is capable of much better pure hydrogen yield for the same autothermal reforming operating conditions.     

萃取和干燥对热致相分离制备聚丙烯微孔膜的影响

应用相对膜体积变化对萃取和干燥的影响进行表征,研究了萃取剂表面张力、沸点以及相互作用与微孔收缩之间的关系,实验结果表明随普萃取剂表面张力的增大、沸点的升高、相互作用的增强,相对膜体积呈下降趋势。这说明毛细管压力的大小、作用时间以及萃取剂对微孔壁的软化作用都会对微孔收缩产生重要影响。     

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.