钯膜及钯膜反应器的研究进展

钯基膜具有很高的透氢速率和透氢选择性以及良好的化学和热稳定性,一直是膜技术领域的研究热点。文章综述了钯膜的透氢原理、钯膜制备方法及钯膜反应器的研究进展。重点介绍了钯膜反应器在加氢、脱氢等反应中的应用,并对钯膜反应器的发展趋势进行了展望。     

钯膜及钯膜反应器的研究进展

钯基膜具有很高的透氢速率和透氢选择性以及良好的化学和热稳定性,一直是膜技术领域的研究热点。文章综述了钯膜的透氢原理、钯膜制备方法及钯膜反应器的研究进展。重点介绍了钯膜反应器在加氢、脱氢等反应中的应用,并对钯膜反应器的发展趋势进行了展望。     

流化床透氧膜反应器用于天然气制氢的工艺模拟

氢气是一种重要的化工原料,流化床透氧膜反应器是一种新型的天然气制氢装置。建立了该新型装置的AspenPlus模型,并模拟了反应压力、氧碳比(OC)、水碳比(SC)对反应温度、合成气成分的影响,并与普通的流化床自热反应器进行了比较。结果表明,流化床透氧膜反应器由于分离了空气中的N2,反应可在高的氧气摩尔分数下进行,合成气中的H2摩尔分数大大提高,甲烷转化率较大,氢气产量也提高。     

透氢铌基钯合金膜

目前商用的致密型钯合金膜是钯银合金膜,较高的使用成本限制了其大规模的应用。而铌基钯合金膜因其较高的透氢率,机械性能及较低的使用成本等诸多优势受到了广泛关注。本文简要介绍了钯膜的透氢机理和影响钯膜透氢性能的因素,重点综述了以Pd/Nb/Pd复合膜为代表的新型夹层型复合膜透氢性能的研究进展,并对未来铌基钯合金膜的研究方向作出了展望。     

流化床膜反应器的应用研究进展

流化床膜反应器中所采用的膜主要有2类,一类为钯(及其合金)膜,另外一类为透氧膜.介绍了近十几年来流化床膜反应器的新型应用研究,主要集中在反应器概念设计、膜及其透过性能、以及流化床流体特性.提出未来有必要对流化床膜反应器中化学反应与膜分离过程的耦合这一关键科学问题进行深入的研究,揭示膜对流化床流体力学特性的影响和流化床对膜透过性能的影响机理,以及这两个过程的耦合机制.     

多孔膜反应器中丙烷催化脱氢制丙烯的模拟研究

针对丙烷高效脱氢制丙烯的多孔膜反应器构建了无量纲数学模型并进行了模拟研究,考察了催化剂活性、透氢膜性能、操作条件对多孔膜反应器中丙烷脱氢的转化率、丙烯收率、氢气收率和纯度的影响。结果表明,移走产物氢气可以有效提升膜反应器的性能,其性能的提升程度由不同温压条件下催化剂和透氢膜性能共同决定。高活性催化剂是丙烷高效转化的基础,催化剂活性越高,膜反应器内的产氢速率越快;其次,膜的选择性和渗透通量越高,氢气的移除效率越高,可在最大程度上打破热力学平衡的限制,使反应向生成丙烯的方向移动。当多孔透氢膜的氢气渗透率在10^-7~10^-6 mol·m^-2·s^-1·Pa^-1,H₂/C₃H₈选择性达到100时,其丙烷转化率可以与Pd膜反应器内的转化率相当,但分离的氢气纯度低于Pd膜反应器。与传统的固定床反应器相比,膜反应器由于促进了化学平衡的移动,可以在较低的反应温度下获得相当高的丙烷转化率,且丙烷转化率随着反应压力的增加呈现出一个最大值。该模拟研究可为实际生产过程中膜反应器用于PDH反应的高效强化提供有益的技术指导。     

基于Ba-Ce-Co-Fe-O膜反应器的甲烷部分氧化反应研究

为开发稳定性和透氧量俱佳并适用于甲烷部分氧化反应(POM)的透氧膜材料,采用溶胶凝胶工艺合成了具有纯相钙钛矿结构的BaCe0.1Co0.4Fe0.5O3-δ混合导体陶瓷材料。POM操作结果表明:BaCe0.1Co0.4Fe0.5O3-δ膜反应器透氧量高于同类材料,875℃时透氧量达到了8.9 mL/(cm2.m in)。在1 000 h寿命实验中,膜反应器各项反应指标没有出现任何衰减,反应性能稳定,甲烷转化率和CO的选择性都在97%以上。SEM表征表明,反应后膜片表面微观结构的变化虽然不可避免,但是其仍然保持比较完整的结构。因此,该材料良好的透氧量和稳定性说明其具有较好的应用前景。     

非对称LSCF中空纤维透氧膜的制备及性能

采用溶胶-凝胶法制备了具有钙钛矿型结构的La_(0.6)Sr_(0.4)Co_(1-y)Fe_yO_(3-δ)(LSCF,y=0.2,0.5或0.8)氧化物,然后以相转化烧结技术制备了LSCF中空纤维透氧膜,考察了凝固浴与Co/Fe摩尔比对LSCF中空纤维膜微结构及透氧性能的影响。使用70%(质量分数) NMP与30%乙醇的混合液作为内凝固浴,去离子水为外凝固浴,制备了具有外表面薄而致密的分离层、同时具有贯穿内表面的众多指状孔结构的LSCF中空纤维陶瓷膜。指状孔结构会极大地降低扩散阻力,从而改善LSCF膜的透氧量。LSCF中空纤维膜的透氧量随温度和吹扫气He吹扫速率的增加逐渐升高。Co/Fe摩尔比对LSCF中空纤维膜的微观结构和透氧量具有重要影响,透氧量随Co/Fe摩尔比的增大而增加。950℃(透氧膜的测试温度)、吹扫气He的吹扫速率为120 m L·min~(-1)、Co/Fe摩尔比为4时,LSCF透氧膜的氧气渗透通量达到2.81 m L·min~(-1)·cm~(-2)。     

钙钛矿型混合导体透氧膜的研究

详细地介绍了近年来国内外有关钙钛矿型混合导体透氧膜的透氧机理、研究进展以及其应用范围,对其制备方法及表征进行了阐述,并对此类材料的应用前景作了展望。     

混合导体透氧膜材料的设计与应用

混合导体透氧膜材料在高温下具有氧离子－电子混合导电性能,在纯氧制备、膜反应器以及固体燃料电池等方面展现出广阔的应用前景。本文对近年来混合导体透氧膜材料的开发和在甲烷部分氧化等方面的应用进行了详细综述,重点介绍了本课题组在此领域的工作。     

Promotion of hydrogen permeation on metal-dispersed alumina membranes and its application to a membrane reactor for methane steam reforming

A mesoporous membrane for selective separation of hydrogen was prepared usingthe sol-gel method. Some metal salts such as RuCl₃, Pd(NH₃)₄Cl₂, RhCl₃,, and H ₂PtCl₆, were added to the boehmite sol and coated on a porous alumina substrate before firing at 500°C. It was foundthat the permeability of hydrogen and the separation factor for a hydrogen-nitrogen gaseous mixture of these metaldispersed membranes exceeded the limitations of the Knudsen diffusion mechanism. Although the gas permeation through a neat alumina membrane is governed by the Knudsen diffusion, the metals dispersed in alumina membranes were effective in promoting hydrogen permeation. These metaldispersed alumina membranes were also used in a membrane reactor for methane steam reforming at low temperature. In the temperature range of 300 to 500°C, the membrane reactor attained a methane conversion twice as high as the equilibrium value of the packed bed catalytic reactor system as a result of the selective removal of hydrogen from the reaction system.     

钯膜及其在涉氢反应中的应用研究进展

综述了钯膜应用的研究进展，重点阐述了钯膜的透氢机理、制备方法、表征方法及在涉氢反应中的应用，总结了钯膜透氢性能的影响因素，指出了钯膜在分离和催化反应中面临的挑战，并对钯膜反应器的应用发展前景进行了展望。     

钯银合金膜反应器中二甲醚水蒸汽重整体系的透氢性能研究

二甲醚(DME)由于其清洁环保特性成为燃料电池电动汽车的理想氢源之一。在200~300℃温度范围,1.0×105~4.0×105Pa的压力范围内,Pd-Ag-Au-Ni合金膜对H2与Ar和N2的分离系数接近无穷大,同时,膜具有较好的透氢稳定性。通过实验研究了膜反应器中Ar、N2、CO、CO2、H2O和DME等气体存在时对钯银合金膜透氢性能的影响。实验结果表明,Ar、N2、DME基本对透氢性能无影响,CO2、CO、H2O存在时,会影响氢气的渗透性。三者当中,CO2的影响最小,混合气中H2O比CO对透氢性能的影响大,这是由于H2O在钯膜表面有更大的竞争吸附作用。本研究结果为更详细地研究二甲醚水蒸气重整制氢过程提供了重要参考依据。     

Production of pure hydrogen and more valuable hydrocarbons from ethane on a novel highly active catalyst system with a Pd-based membrane reactor

Production of pure hydrogen and more valuable hydrocarbons from ethane on a novel highly active catalyst system with a Pd-based membrane reactor is studied at the mild reaction temperatures of 773–858 K and a wide SV range of ethane. Re/HZSM-5 is highly active for upgrading of ethane for production of hydrogen and more valuable hydrocarbons such as ethylene and aromatics (BTX) even at the relatively lower temperatures. Formation rates of the more valuable hydrocarbons and hydrogen are remarkably enhanced by selective permeation of hydrogen product in the membrane reactor. It is also found that formation rate of methane as a side product is effectively suppressed by selective permeation of hydrogen though the membrane tubes. Therefore, both ethane conversion and selectivity for production of hydrogen and more valuable hydrocarbons such as ethylene and BTX are greatly enhanced by application of the membrane reactor.     

Preparation and properties of polybenzidine film-coated electrode as an H2O2 selective polymeric material

By means of electrochemical polymerization, polybenzidine-modified electrodes were prepared in an aqueous monomer solution at a potential of 0.7 V versus Ag/AgCl. The permselective character of the polybenzidine electrode prepared in a one-step procedure was examined for electroactive (ascorbic acid, oxalic acid, and hydrogen peroxide) and nonelectroactive (lactose, sucrose, and urea) species. Influence of the various parameters on the permselective properties of the polybenzidine membrane was systematically investigated and the optimal values for these parameters were determined. It has been found that polybenzidine membrane showed selective permeation for hydrogen peroxide while blocking the permeation of electroactive and nonelectroactive interferents through film. In brief, it is claimed that this polybenzidine film can be used as a coating material to prevent interferences in electrochemical biosensor applications. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2227–2234, 1998     

Diffusion coefficient of hydrogen in a Pd-Ag membrane: Effect of hydrogen solubility

The permeabilities of hydrogen through a Pd₇₅-Ag₂₅ membrane have been measured at temperatures ranging from 423 to 573 K and under hydrogen pressure differences ranging from 69 to 256 kPa. From the available literature solubility data a neural network model has been developed in order to simulate the variation of the hydrogen content in the alloy as a function of pressure and temperature. Then, from steady state permeability measurements and calculated solubilities, the diffusion coefficients of hydrogen have been computed. At a given temperature, the diffusion coefficient has been found to decrease with the hydrogen content (0.1 ≤ n = H/M ≤ 0.37). A simple relation is then suggested to predict the variation of the diffusion coefficient on both temperature and hydrogen content. To account for the variation of the diffusion coefficient with n, the integration of Fick's law of diffusion has been performed numerically, resulting in non-linear profile of hydrogen content through the membrane under steady state permeation.     

钯膜制备新技术

介绍了钯膜的制备方法及在载体上制备越薄钯膜的改进技术，由无电子电镀过程制备的钯膜对氢渗透速率高，对氢有良好的选择性，由金属有机气相沉积法（MOCVD）在载体孔内沉积钯膜有助于防止氢的脆化作用，利用渗透压的新技术可控制膜的微观结构和孔隙率。将多孔不锈钢作为载体时，利用不同的技术能克服氢的脆化作用，减少钯膜厚度以及防止钯－银层与不锈钢间金属原子的相互扩散，由光催化沉积可在半导体载体上制备越薄钯膜。     

氯碱先进生产技术在黑龙江昊华的应用

介绍了黑龙江昊华化工有限公司氯碱厂在2010年建设的25万t/a离子膜法烧碱工程中,采用的膜法脱硝工艺、膜极距复极式离子膜电解槽、孟莫克布林克除雾器元件、副产蒸汽二合一氯化氢炉4项先进生产技术的实际应用情况。     

Hydrogen evolution and permeation into steel during zinc electroplating; effect of organic additives

The Devanathan and Stachurski diffusion membrane method was used to study the evolution of hydrogen and its permeation into a steel sheet during cathodic charging from a chloride electrolyte or during zinc electroplating. The influence of four different organic compounds, which are the components of various formulations derived to improve zinc electrocoatings, were also tested. At a high-charging current density, the permeation transients obtained in a chloride electrolyte without zinc ions exhibit a maximum attributed to hydrogen trapping in the subsurface layer on the entry side. The concentration of adsorbed hydrogen on the steel surface depends not only on the cathodic current density and the composition of the solution, but also on the influence of the organic additives on the recombination of hydrogen atoms. During zinc electrodeposition, the coating covers the substrate in a few seconds and acts as a barrier for hydrogen absorption. The permeation rate depends on the cathodic current density but also on the concentration of ZnCl₂ in correlation with the porosity of the coating. It is shown that steel substrate hydrogenation (beneath the zinc coating) is strongly reduced in the presence of a combined additive, composed of four compounds in appropriate amounts as well as in the presence of PEG₆₀₀₀ in the plating bath. This effect, which is correlated to the modification of the hydrogen evolution process, can be used to hinder the severe drawbacks caused by hydrogen penetration into the steel substrate.     

二维材料调控阻氢涂层研究进展

在涉氢应用领域,氢及其同位素的渗透导致结构材料氢损伤、能源浪费及核污染等诸多问题,在结构材料表面覆盖阻氢涂层是解决氢渗透问题的重要技术手段。总结了传统阻氢涂层的特性及其阻氢效果,并阐明了传统阻氢涂层仍然存在的效率低及寿命短等问题。最新研究表明,石墨烯等二维材料薄膜具有很强的阻挡特性,多层堆垛结构效果尤其明显,可作为优异的阻氢材料,而传统阻氢涂层兼具有一定的吸附储氢性能。通过对氢渗透机理的分析提出引入二维材料作为阻氢层,并结合传统阻氢涂层的储氢特性构建新型阻氢结构模型,阐述了阻氢层的制备应用现状及储氢层的储氢机理,同时探讨了针对不同应用背景下新型阻氢结构的不同形式与应用效果,最后展望了新型阻氢结构涂层在不同应用领域下的应用前景。