透氢钯复合膜的原理、制备及表征

钯及其合金膜由于具有透氢性好和耐高温的特点,除了用作氢气分离和纯化器外,还可以用作脱氢、制氢等反应的反应器,以实现反应和分离的一体化,并提高转化率和选择性。本文综述了钯基复合膜的原理、制备及表征,并重点介绍了本研究组的光催化镀膜工艺。     

透氢钯复合膜的原理、制备及表征

钯及其合金膜由于具有透氢性好和耐高温的特点,除了用作氢气分离和纯化器外,还可以用作脱氢、制氢等反应的反应器,以实现反应和分离的一体化,并提高转化率和选择性.本文综述了钯基复合膜的原理、制备及表征,并重点介绍了本研究组的光催化镀膜工艺.     

膜催化研究——Ⅳ.钯-氧化铝/陶瓷复合膜

本文在无机氧化铝膜的基础上掺入钯,用sol-gel法制得钯-氧化铝/陶瓷复合膜,将该膜用于乙醇脱氢制乙醛反应,分别考察了反应温度、乙醇进样量以及内管惰性气体吹扫气流对乙醛产率的影响,并在相同条件下比较了常规反应器及单纯氧化铝膜反应器的结果.实验数据表明,氧化铝膜中掺入钯后可显著提高乙醛产率.本文测定了该复合膜的H_2/Ar分离系数、孔径分布,并利用电子显微镜、X射线衍射等手段对其进行了表征.     

负载型Heck反应催化剂的研究进展

Heck反应是一类重要的C-C偶联反应,传统的均相Heck反应催化剂存在分离和回收困难等问题;近年来负载型Heck反应催化剂的研究引起了人们的广泛关注.本文综述了钯基和非钯基负载型Heck反应催化剂的研究进展,评述了不同载体上催化活性组分对Heck反应的特点,并展望了其发展趋势.     

钯合金膜分离纯化氢同位素的研究进展

钯合金膜因其具有优异的透氢性能及良好的化学和热稳定性,已被广泛应用于氢同位素的分离纯化领域。而PdAg和PdY合金膜在众多钯合金膜中透氢性能出色备受关注。本文比较了PdAg、PdY等多元钯合金膜的透氢性能及抗中毒情况,总结了PdAg复合膜的制备方法及透氢选择性,重点介绍了钯合金膜分离氢同位素的研究进展,并对钯合金膜的未来研究方向进行展望。     

钯复合膜的研究进展

钯复合膜具有很高的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。本文综述了近年来在钯复合膜透氢机理、钯膜制备方法以及钯膜反应器等方面的研究进展；着重讨论了近3年来钯复合膜制备方法的新进展，包括超临界条件下制备钯复合膜的新技术等内容；总结了钯复合膜在脱氢、部分氧化以及耦合反应过程中应用的一些代表性工作，并对钯复合膜制备与应用的发展趋势进行了展望。     

含氮配体的分子内邻位钯化反应

总结了近年来含氮配体的分子内邻位钯化反应,分析了钯化试剂、金属环大小、溶剂以及底物结构等因素对钯反应的影响以及它们在有机合成中的应用,讨论了邻位钯反应的机制。     

二苯硫脲纤维素分离富集原子吸收光谱法测定地质样品中痕量钯

采用自行研究了合成的二苯硫脲纤维素分离富集地质样品中痕量钯，并使用火焰原子吸收光谱法（ＦＡＡＳ）测定，系统研究了二苯硫脲纤维素分离富集钯的各种条件，并将方法应用于地质样品中痕量钯的分析。     

负载钯催化的Suzuki偶联反应研究进展

负载钯催化的Suzuki偶联反应,由于产物易分离、催化剂可重复使用,已引起人们的广泛关注.综述了近年来负载钯催化的Suzuki偶联反应研究进展,载体包括活性碳、金属氧化物、硅铝酸盐微孔分子筛、二氧化硅材料、活性粘土和聚合物等.     

不饱和烃杂钯化反应在有机合成中的应用

不饱和烃杂钯化反应是合成高活性反应中间体烷基钯(II)和烯丙基钯(II)重要的途径. 这些钯的络合物, 在合适的条件下能被各种亲核试剂例如烯丙基卤、一氧化碳、不饱和烃、有机硼、有机锡等捕获. 经过一系列插入及消除反应, 能够有效地构建多种生理活性药物、有机功能分子以及重要合成骨架. 近年来, 引起了有机合成工作者的兴趣. 在这里, 对杂钯化最新进展进行综述.     

Study on the variation of morphology and separation behavior of the stainless steel supported membranes at high temperature

Palladium composite membranes were prepared on stainless steel (SUS) supports modified by nickel submicron powder and colloidal silica sols. Permeation tests of the palladium composite membranes were carried out at high temperature in order to observe the thermal stability of the membrane. The palladium composite membrane failed with formation of plenty of pinholes in the presence of hydrogen at high temperature. The failure of the composite membrane was verified by comparing the nitrogen permeance before hydrogen permeation test with that after hydrogen permeation test and comparing the H₂/N₂ selectivity for single gas permeation test with that for mixture gas permeation test. The variation of the membrane surface due to the failure of the membrane was characterized in scanning electron microscopy (SEM) and energy dispersive X-ray spectrometer (EDS) analyses. As a result, it can be concluded that reducible metal oxides can be attributed to the failure of the composite membranes resulting from reduction of the metal oxides by hydrogen whichever position in the membrane the metal oxides are layered.     

An observation of palladium membrane formation on a porous stainless steel substrate by electroless deposition

The membranes made of palladium and its alloys are used for the extraction of high quality hydrogen from a mixture of gases. Most of recent research is focused on the development technologies for depositing a durable ultra-thin palladium membrane on a porous substrate in order to assure a good mechanical support and maximize the flux of hydrogen permeation. The formation of a palladium membrane deposited on a porous stainless steel substrate by an electroless process is recorded and described in this paper. The palladium deposition progress around the pore area at the surface of the substrate in the initial stages is illustrated. A bridge model is presented to describe the membrane formation around the pore area of the substrate. This model, together with the micrographs showing the deposition progress on the pore areas, will lead to the control of the deposition process for a membrane fabrication as well as the design and modification of a substrate.     

Experimental studies on the hydrogen isotope recovery using low-pressure palladium membrane diffuser

In this paper, we introduce a set of low-pressure palladium membrane diffuser designed to recover hydrogen isotopes from inert mixture gases. Several gaseous mixtures (D₂/Ar and D₂/He) with different deuterium concentration have been used for cleanup test of the low-pressure palladium membrane diffuser at 723 K. Effect of the composition of feed gas on the pressure of permeate side has been observed by gas chromatography (GC) and pressure sensor. With the feed flow rate of the mixture gases increasing, the D₂ permeate pressure is increasing as well. Decontamination factor (DF) of more than 1000 and recovery efficiency greater than 99.9% have been obtained by controlling the feed gas flow rate. The same palladium membrane diffuser was used to process helium-3 gas with more than 10% hydrogen isotope and about 0.3% tritium gas. The pure helium-3 (above 99.4%) with low content of hydrogen isotopes (about 0.084%) has been obtained. Recovery efficiency of all hydrogen isotopes is 99.5% above.     

Chelated palladium nanoparticles on the surface of plasma‐treated polyethersulfone membrane for an efficient catalytic reduction of p‐nitrophenol

Herein, a novel method was reported for the use of polyethersulfone (PES) membranes in catalytic reactions with an enhanced distribution and superior catalytic activity of palladium nanoparticles immobilized on the surface of the membranes. For this purpose, the surface of PES membrane was treated with plasma, and subsequently, the consequent oxygen‐containing functional groups were reacted with APTES and 2‐pyridinecarbaldehyde, respectively, to provide sites by which Pd could form complexes. The mean roughness as well as the surface and cross‐sectional morphology were investigated using atomic force microscopy, scanning electron microscopy (SEM), and field‐emission scanning electron microscopy (FESEM), respectively. Furthermore, SEM mapping was used to examine the palladium distribution on the surface of the membranes. Further characterizations of as‐prepared Pd‐loaded PES membranes conducted using EDX, ICP, and XRD analyses. The reduction of p‐nitrophenol to p‐aminophenol was also used as a model reaction to investigate the membranes' performance. The results, analyzed using UV‐Vis instrument, demonstrated that the complete reduction of p‐nitrophenol was achieved at a short time via Pd‐chelated plasma‐treated membrane. Furthermore, the rod‐like and sphere‐like structure of Pd was acquired as a result of palladium chelating with nitrogen‐containing ligands, produced through the reaction between 2‐pyridinecarbaldehyde and (3‐Aminopropyl)triethoxysilane. It was observed that the rod‐like structure of Pd exhibited a trivial catalytic activity in reduction of p‐nitrophenol to p‐aminophenol in contrast with the sphere‐like structure, nonetheless.     

“Superpermeability” and “pumping” of atomic hydrogen through palladium membranes

Permeation of atomic as well as molecular hydrogen through palladium membranes has been investigated experimentally in the temperature range from room temperature to 200 °C and at a higher incident flux of hydrogen atoms on palladium surface than in previous studies. The results demonstrate that phenomena of ‘superpermeability’ and ‘pumping’ of atomic gases through metal membranes are of a common nature. A theoretical model based on chemical thermodynamics and diffusion theory adequately describes the quantitative relationships observed in experiments. It was found that permeability of atomic hydrogen depends strongly on the magnitude of surface incident flux and membrane temperature.     

Repair of Pd/α-Al_2O_3 composite membrane with defects

A palladium composite membrane with a large number of defects was repaired using the electroless plating combined with the technique of osmosis. The loose structure of palladium film prepared by the conventional electroless plating was densified. Defects were repaired. Hydrogen selectivity was thus significantly increased without significantly increasing palladium film thickness and reducing hydrogen permeability.     

Palladium magnetic nanoparticle‐polyethersulfone composite membrane as an efficient and versatile catalytic membrane reactor

Developing polymer catalytic membrane reactors is an aim due to its outstanding advantages. In this paper, a novel catalytic membrane containing palladium‐supported magnetic nanoparticles is introduced. Silica‐iron oxide core shell nanoparticles were first prepared and functionalized by phosphine ionic liquid functionalized poly(ethylene glycol). The modified magnetic nanoparticles were used as support for immobilization of palladium. The final palladium‐immobilized nanoparticles were used as active filler for the preparation of membrane reactor. The prepared membranes were characterized, and their activities were tested in carbon‐carbon bond formation and catalytic reduction. The catalytic membrane showed good performance in the mentioned reactions.     

Repair of Pd/α-Al2O3 composite membrane with defects

A palladium composite membrane with a large number of defects was repaired using the electroless plating combined with the technique of osmosis. The loose structure of palladium film prepared by the conventional electroless plating was densified. Defects were repaired. Hydrogen selectivity was thus significantly increased without significantly increasing palladium film thickness and reducing hydrogen permeability. Project supported by the Chinese Academy of Sciences (Grant No. KJ951-A1-508) and the National Natural Science Foundation of China (Grant No. 29392003).