Carbon supports from natural organic materials and carbon-supported palladium catalysts

Experimental data are presented concerning the influence of preparation conditions on the pore structure of carbon supports obtained from different types of plant biomass, thermally expanded graphites, and chemically modified anthracites, on the distribution and particle size of supported palladium, and on the activity of the supported catalyst in the liquid-phase hydrogenation of hex-1-ene and cyclohexene.     

固载化催化剂在烯烃氧化合成醛酮中的应用

总结了固载化催化剂在烯烃氧化合成醛酮中的应用。着重介绍了钯配合物固载在无机载本上,钯盐和杂多化合物固载在无机载体上,钯盐固载在化催化剂在烯烃氧化合成醛酮中的应用。对负载型液相催化剂,负载型水相催化剂,负载型熔融盐Wacker催化剂,活性C固载的Pd膜及Pt膜催化剂催化烯烃氧化合成醛酮也作了简单介绍。     

Specific features of the catalytic behavior of supported palladium nanoparticles in heterogeneous catalytic reactions

Specific features of the catalytic behavior of supported palladium nanoparticles were analyzed in terms of both the size of the particles and their interaction with the support. The influence of these factors on the activity and selectivity of palladium nanoparticles in carbon-carbon bond hydrogenolysis, hydrogenation of aromatic compounds, olefins, and acetylenes, hydrodechlorination, as well as complete oxidation of organic compounds was discussed. It was shown that the optimal nanoparticle size depends on the type of the reaction and also such factors as the nature of interaction between the nanoparticles and support, absorptivity of the substrates and catalytic reaction products, and electronic and crystal structure of the nanoparticles.     

磁性纳米粒子负载钯催化有机合成反应研究进展

磁性纳米粒子负载钯催化的有机合成反应,由于具有催化活性高,催化剂在外加磁场作用下即可快速分离和重复使用等特点,已引起了人们的广泛关注.综述了近年来磁性纳米粒子负载钯催化有机合成反应的研究进展,载体包括Fe3O4纳米粒子、有机小分子修饰的磁性纳米粒子、SiO2包覆的磁性纳米粒子、碳修饰磁性纳米粒子、羟基磷灰石包覆的磁性纳米粒子和有机高分子修饰的磁性纳米粒子等.     

Palladium nanoparticles supported on poly (N-vinylpyrrolidone)-grafted silica as new recyclable catalyst for Heck cross-coupling reactions

Novel catalytic system based on palladium nanoparticles supported on poly (N-vinylpyrrolidone) (PVP) grafted silica was prepared. Aminopropylsilica was reacted with acryloyl chloride to form acrylamidopropylsilica, and onto this functionalized silica vinylpyrrolidone monomer was polymerized by free-radical polymerization. The complexation of PVP-grafted silica with PdCl₂ was carried out to obtain the heterogeneous catalytic system. X-ray diffraction (XRD) technique and transmission electron microscopy (TEM) image showed that palladium dispersed through the support in nanometer size. This catalytic system exhibited excellent activity in cross-coupling reactions of aryl iodides, bromides and also chlorides with olefinic compounds in Heck-Mizoraki reactions in short reaction time and high yields. Elemental analysis of Pd by inductively coupled plasma (ICP) technique and hot filtration test showed low leaching of the metal into solution from the supported catalyst. The catalyst can be reused several times in repeating Heck reaction cycles without considerable loss in its activity.     

The leaching and re-deposition of metal species from and onto conventional supported palladium catalysts in the Heck reaction of iodobenzene and methyl acrylate in N-methylpyrrolidone

When supported palladium catalysts are used for Heck vinylation of iodobenzene with methyl acrylate in N-methylpyrrolidone (NMP) in the presence of triethylamine and sodium carbonate bases, the reaction proceeds homogeneously with dissolved active palladium species that are formed through coordination of NMP and triethylamine with palladium. These active species easily react with iodobenzene (oxidative addition), beginning the catalytic cycle of Heck coupling. The last step of catalyst regeneration takes place with the action of sodium carbonate. The active palladium species are not stable and deposit the metal to support when they cannot find iodobenzene to react in the reaction mixture after this substrate is completely consumed. The re-deposition of palladium occurs on the surfaces of bare support and/or palladium particles remaining on it, depending on the nature of support surface and the number and size of residual metal particles. The growth of palladium particles has been observed after the reuse of catalyst in some case. However, the supported catalysts are recyclable without loss of activity.     

Reductive carbonylation of nitrobenzene over Pd/Fe/I2/Py and Pd/C/Fe/I2/Py catalytic systems

A simple catalytic system containing metallic palladium, iron and iodine has been shown to be very active in the carbonylation of nitrobenzene to carbamate. The influence of the components of the catalytic system studied on its selectivity and activity has been established. It has been found that the catalytic activity of palladium supported on carbon (using both lignite coal and bituminous coal) was not lower than the activity of metallic palladium. This revised version was published online in August 2006 with corrections to the Cover Date.     

Influence of support and of palladium profile in the pellet on the catalytic activity for selective hydrogenation

The metal profile in the pellets does not affect the catalytic activity of palladium supported catalysts during selective styrene hydrogenation. The support, due to different metal-support interactions, modifies the activity.     

0.1%Pt-0.02%Pd/不锈钢整体催化剂上丙酮氧化性能及稳定性(英文)

制备了0.1%Pt-0.02%Pd/不锈钢整体催化剂。选取不锈钢为该催化剂的载体,可克服传统γ-Al2O3和堇青石蜂窝载体热稳定性差的缺点。采用阳极氧化技术在不锈钢上自生长了结构致密的多孔阳极氧化膜,并在其上负载Pt和Pd制备得到挥发性有机物(VOCs)净化催化剂。结果表明,经500、800和1000℃不同温度焙烧后,该催化剂完全氧化丙酮的温度分别为160、160和200℃。该催化剂表现出以下优点:(a)高温稳定性能好;(b)低温催化活性高;(c)贵金属负载量低。通过SEM和EDX等技术对该催化剂的结构及活性组分分散情况进行了表征。     

Preparation and characterization of bimetallic PdMo/Y-zeolite: catalytic properties in methane combustion

This work deals with the preparation and the characterization of palladium and palladium–molybdenum supported on HY and NaY zeolites, with the aim to study the effect of molybdenum on the properties of palladium. Catalytic performances were tested in the reaction of methane combustion. The introduction of molybdenum in palladium exchanged zeolites NaY and HY was realized in dynamic or static regime (under vacuum) using Mo(CO)₆ vapor at ambient temperature. Pd was found to migrate in supercages under the influence of Mo(CO)₆, which produces by decomposition, Mo⁵⁺ species revealed by EPR spectroscopy and consequently palladium was reduced. Catalytic results show that the activity of PdHY increases with time during a relatively long period compared to the other samples. This activation in stream can be attributed to a slow migration of palladium to supercages. Nevertheless, PdHY and PdMoNaY were less active than PdNaY at 500 °C. The catalytic activity of monometallic samples increases with time, whereas it decreases for bimetallic ones. The comparison of the catalytic activities of Pd and PdMo supported on NaY and HY suggests that the basicity of the support enhances the oxidation ability of palladium by an increase of the electronic density of the metal particles at the surface. The pretreatment conditions exerted also a great effect on the behavior of mono and bimetallic catalysts. The reduction in hydrogen at 500 °C led to a decrease of the combustion activity depending on the nature of the catalyst.     

Catalytic allylation of 1-trimethylsilyloxycyclopent-1-ene into 2-allylcyclopentanone over palladium supported on silica

1-Trimethylsilyloxycyclopent-1-ene can be catalytically converted into 2-allylcyclopen-tanone through reaction with diallyl carbonate over palladium supported on silica. The selection of solvent was crucial, ethylene glycol dimethyl ether being the most effective solvent giving 74.9% yield of 2-allylcyclopentanone and 95.7% selectivity over palladium (4.1 wt.%) supported on silica at 333 K for 24 h. The catalytic activity depended strongly on the dispersion of palladium.     

乙二胺功能化树脂负载Pd(0)配合物：可重复使用的高活性Heck芳基化催化剂

The ethylenediamine-functionalized resin-supported Pd(0)complex was prepared from PdCl_2 and ethylenedia-mine-functionalized chloromethylated polystyrene,followed by reduction with KBH_4.The complex was character-ized by FT-IR,XRD,BET,SEM and EDS.The resin-supported catalyst exhibited high catalytic activity in theHeck reaction and could be reused up to 17 times in NMP or 16 times in DMF at 90 ℃ in the Heck reaction of io-dobenzene with acrylic acid.The leaching investigation disclosed that the palladium leaching was caused by the in-teraction of iodobenzene with the metal Pd(0)on supported catalyst.The leached palladium species in filtrate wasvery stable and could be reused five times after the solid catalyst was filtered off.A cross-transfer test in recyclingin the presence of additional carbon disclosed that the soluble leached palladium species had much higher catalyticactivity than supported and/or adsorbed palladium in solid-solution heterogeneous Heck reaction.     

Effect of the Structure of Carbon Nanofibers on the State of an Active Component and on the Catalytic Properties of Pd/C Catalysts in the Selective Hydrogenation of 1,3-Butadiene

The state of highly dispersed palladium particles supported on filamentous carbon was studied using high-resolution electron microscopy, XPS, and X-ray diffraction analysis. Three types of filamentous carbon were used, in which the basal planes of graphite were arranged along, across, and at an angle to the nanofiber axis. The amount of supported palladium was 0.25–5.8 wt %. The structure of the carbon support was found to affect the properties of the active component. Highly dispersed palladium particles exhibited the strongest interaction with a carbon surface formed by the butt ends of graphite (002) layers. This interaction resulted in electron transfer from the metal to the support and in the stabilization of palladium in the most dispersed state. A change in the properties of palladium particles caused a change in the catalytic properties of Pd/C catalysts in the reaction of selective 1,3-butadiene hydrogenation to butenes. The strong interaction of Pd²⁺ with the butt ends of graphite resulted in the stabilization of palladium in an ionic state. An increase in the fraction of Pd²⁺ in the catalysts was responsible for a decrease in both the overall activity and selectivity of Pd/C catalysts in the reaction of 1,3-butadiene hydrogenation to butenes.     

Regularities of formic acid oxidation in the presence of porous silicon nanocomposites with palladium

Nanocomposites demonstrating high catalytic activity in the oxidation of formic acid were obtained by depositing palladium on porous silicon support. The palladium samples on porous silicon are superior to commercial samples on carbon black in many characteristics. A decrease in the size of palladium nanoparticles favors an increase in the catalytic activity of the palladium/porous silicon nanocomposites.     

Nano-scale effects in electrochemistry

We report combined scanning tunneling microscopy and electrochemical reactivity measurements on individual palladium nanoparticles supported on a gold surface. It is shown that the catalytic activity towards electrochemical proton reduction is enhanced by more than two orders of magnitude as the diameter of the palladium particles parallel to the support surface decreases from 200 to 6 nm. Density functional theory (DFT) calculations combined with molecular dynamics (MD) simulations have been used to investigate the origin of the effect. It is concluded that the size effect is given by the thickness-variation of the support-induced strain at the surface of the palladium nanoparticles.     

Silica–acetylacetone‐supported palladium nanoparticles as an efficient and reusable catalyst in the Heck–Mizoroki C–C cross‐coupling reaction

The preparation of palladium nanoparticles supported on acetylacetone‐modified silica gel and their catalytic application for Heck olefination of aryl halides were investigated. The catalyst was characterized using X‐ray diffraction, X‐ray photoelectron spectroscopy, and transmission and scanning electron microscopies. The supported palladium nanoparticles are demonstrated to be a highly active and reusable catalyst for the Heck reaction. Several reaction parameters, including type and amount of solvent and base, were evaluated. The heterogeneity of the catalytic system was investigated with results indicating that there is a slight palladium leaching into the reaction solution under the applied reaction conditions. Despite this metal leaching, the catalyst can be reused nine times without significant loss of catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd.     

Influence of oxygen on catalytic properties of supported palladium catalysts in CO hydrogenation

It has been established that the addition of oxygen to synthesis gas has a positive effect of the activity and selectivity of supported palladium catalysts in methanol synthesis. The degree of the effect of oxygen depends on the chemical nature of the support and the conditions of catalysis, preceding the addition of oxygen to the reaction mixture. The probable causes for the influence of oxygen on the catalytic properties of palladium, supported on oxide supports, have been discussed.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 5, pp. 557–563, September–October, 1989.     

Texture and catalytic properties of palladium supported on thermally expanded natural graphite

Data about preparation and properties of palladium catalysts on porous supports prepared by intercalation and subsequent thermal expansion of natural graphite are presented. Some relations between the structure of the graphite support, the state of supported palladium and its catalytic properties in the model reaction of cyclohexene liquid-phase hydrogenation were established. This revised version was published online in June 2006 with corrections to the Cover Date.     

负载离子液体纳米钯催化芳卤羰化反应

研究了高分散性的负载离子液体纳米钯催化剂的制备及其催化芳卤羰化反应的性能. 用XRD、HRTEM和XPS等方法对催化剂进行了表征, 结果表明, 钯组分处于高分散零价态, 其平均粒径小于5 nm, 且催化剂表面存在一厚度适中的离子液体液膜, 有利于提高催化剂的稳定性; 该催化剂对PhI、PhBr、PhCl的羰化反应的催化活性优于离子液体两相催化体系, 在优化的反应条件下, 碘苯的转化率可达99.3％, 生成苯甲酸乙酯的转化频率(TOF)可高达4926 h−1, 反应产物中苯甲酸乙酯的选择性大于99％.     

膦化聚2,6—二甲基1,4—苯醚负载钯催化剂的表征及其催化性能

报道了四种不同P/Pd摩尔比的膦化聚2,6-二甲基1,4-苯醚负载把催化剂的加氢和异构化性能;通过XPS、电镜和远红外对催化剂进行了表征;并考察了溶剂和温度对催化剂活性的影响.