Amount Of Palladium Research Articles

Synthesis, Characterization and Catalytic Applications of 2,2-Dimethylpropane-1,3-Diaminopalladium(II) Complex in Mizoroki-Heck Reaction

New tetradentate Schiff base ligand (LSB) and its palladium(II) complex, i.e., complexation of N,N'-bis(4-methoxysalicylidene)-2,2- dimethylpropane-1,3-diaminopalladium(II) (PdLSB) has been successfully synthesized through condensation reaction between primary amine 2,2-dimethyl-1,3-propanediamine with 2-hydroxy-4-methoxybenzaldehyde. The palladium complex was then prepared by refluxing the corresponding LSB with an equimolar amount of palladium(II) acetate to give C21H24N2O4Pd. The complex was characterized by using several techniques, such as the elemental chemical analysis CHN, FTIR, NMR spectroscopy and single crystal X-ray crystallography. This air/moisture stable complex was investigated to be a high class of homogeneous catalyst for Mizoroki-Heck reaction. The reaction was monitored by GC-FID at 12 h reaction period. The percentage conversion of 4-bromoacetophenone was 70 % indicated that PdLSB can act as an ideal potential catalyst in the Mizoroki-Heck reaction.

含氚氢同位素中少量氕的去除技术研究

基于前期钯与氢同位素间的基础研究以及相关的工艺实验探索结果，提出了一种能从氘氚气体中快速去除少量氕的新方法—钯留滞法。该方法充分利用常温或低温下钯氢化物的同位素效应，使含氕的氘氚气体流经钯分离柱后，能将少量氕优先留滞在钯分离材料中，从而达到气相氕贫化、固相氕富集的分离效果。实验结果表明，与钯热置换法相比，在相同的处理时间及装钯量下，分离能力提高了近10倍，产品气的提取效率由40%提高至50%~60%左右，大大降低了工作人员的操作强度，提高了工作效率。 Based on the early stage of the palladium interact with hydrogen isotopes of basic research and related technical research, a kind of new method was proposed which can quickly remove a small amount of protium from the deuterium-tritium gas—palladium retention method. The method makes full use of the isotope effect of palladium-hydride system. When hydrogen isotopes gas with a small amount of protium flows through the separation column at normal temperature or low temperature, a small amount of protium priority can be detention in palladium separation material, so as to achieve the gas phase protium dilution, and protium enrichment in solid phase .Results show that compared with palladium thermal displacement method, under the same processing time and the loading amount of palladium, by about 10 times the separation ability, product gas extraction efficiency from 40% to 60%, greatly reduce the intensity of the operating staff and improve work efficiency.

Development of transparent conducting palladium and hydrogen-codoped cadmium oxide thin films

Cadmium oxide is a transparent conducting oxide (TCO) material with versatile applications, many of which are linked to either light transparency in the NIR spectral range in addition to unique electrical conductivity. Doping is a known approach to influence those optoelectrical properties in order to bring them into a desired choice. In the present work, hydrogenated (annealed in hydrogen atmosphere) cadmium oxide (CdO) thin films doped with different amounts of palladium (Pd) ions were deposited on glass and silicon wafer substrates by physical vapour deposition method. The films were characterized by X-ray diffraction, optical absorption spectroscopy, and dc-electrical measurements. The obtained results show notable improvements in the conductivity, mobility, and carrier concentration of host CdO. Hydrogenated CdO film doped with 15 wt% Pd shows utmost enhancement in mobility (32.02 cm2/Vs), conductivity (4.6948 × 103 S/cm) and carrier concentration (9.16 × 1020 cm−3). This suggests the possibility of using hydrogenated Pd-doped CdO films in different TCO field of applications.

Suzuki-Miyaura coupling reactions using novel metal oxide supported ionic palladium catalysts

Palladium substituted CeO2, SnO2 and their mixed oxides have been synthesized in quantitative yields out of non-toxic and inexpensive precursors using a simple and rapid single step solution combustion method. The resulting oxides, especially the mixed oxides Ce0.79Sn0.20Pd0.01O2-δ, Sn0.79Ce0.20Pd0.01O2-δ and Sn0.99Pd0.01O2-δ proved to be highly active (TOF>12,000h−1) for Suzuki-Miyaura cross-couplings of phenylboronic acid with various bromoarenes. The reactions were carried out in ambient air at moderate temperatures using environmentally friendly aqueous ethanol solutions as reaction solvents. Minimal amounts of palladium in the product solution (<0.14mg/L), the reaction kinetics as well as catalyst poisoning tests support the thesis that the reaction proceeds via dissolved palladium species in a homogeneous reaction mechanism. Nevertheless, the synthesized catalysts could be reused for at least five times with only minor changes in activity and no changes in the crystal structure, indicating the high potential of the investigated catalysts as quasi-heterogeneous CC coupling catalysts.

Reactions of palladium(II) and rhodium(III) with pyridylazo-2-naphthol and dithizone on PANV–KU-2 and PANV–AV-17 fibrous materials

Reactions of palladium(II) and rhodium(III) with dithizone (DT) on polyacrylonitrile fiber filled with an AV-17 anion exchanger (PANV–AV-17) and 1-(2-pyridylazo)-2-naphthol (PAN) immobilized on polyacrylonitrile fiber filled with a KU-2 cation exchanger (PANV–KU-2–PAN) are studied by diffuse reflection spectroscopy. Conditions of rhodium complexation on PANV–KU-2–PAN (ascorbic acid concentration, pH of solution in adsorption, and the duration of heating samples) and palladium complexation with DT after adsorption from a 0.1 M NaCl solution (pH 2) on PANV–AV-17 in the dynamic mode are found. The limits of detection for rhodium and palladium are 10 and 5 ng/mL, respectively. At 640 nm, the calibration graphs are linear in the ranges of palladium and rhodium concentrations 0.008–0.06 µg/mL and 0.02–0.2 µg/mL, respectively. The mutual influence of rhodium and palladium is studied. It is shown that the determination of palladium with DT on a PANV–AV-17 solid phase is not affected by the presence of a 5-fold amount of rhodium, and rhodium can be determined on PANV–KU-2–PAN at 590 nm in the presence of 2-fold amounts of palladium.

CO elimination processes over promoter-free hydroxyapatite supported palladium catalysts

The catalytic performance of synthesised calcium-deficient hydroxyapatite supported Pd catalysts are examined for various CO elimination processes, namely CO total oxidation, CO preferential oxidation and water gas shift reactions. The prepared samples loaded with different amounts of palladium (0.5–2%) are thoroughly characterised by a wide number of analytical techniques including N2 physisorption, XRD, H2-TPR, TEM, CO-TPD, H2 chemisorption, OSCC and OSC techniques. The characterisation results show that, besides an incorporation of 0.3wt% Pd into hydroxyapatite structure, on the Pd(0.5)/HAP sample, small Pd particle sizes (7.6nm) are deposited on the HAP support surface presenting relatively high dispersion (19%). The OSCC and OSC studies show that the highly dispersed Pd species lying on the HAP surface present high reducibility and high oxygen mobility.In the three investigated CO elimination processes the Pd(0.5)/HAP catalyst proves to be highly active and exhibits higher stability compared to that of the Pd(1)/HAP and Pd(2)/HAP catalysts. The catalytic performance of the series of the catalysts demonstrates their structure-sensitivity in the investigated processes. The latter are remarkably enhanced in the presence of small Pd particle sizes which provide high reducibility and high oxygen storage capacity. Moreover, the performances of the Pd/HAP catalysts evidence the potential of HAP support as promising alternative to those reported in the available literature.

Palladium‐Catalyzed Aminocarbonylation of Aryl Halides with 2,4,6‐Trichloro‐1,3,5‐triazine/Formamide Mixed Reagent

AbstractIn this work, the mixture of formamide and 2,4,6‐trichloro‐1,3,5‐triazine (cyanuric chloride or TCT) is introduced as a new amidating agent in Pd‐catalyzed aminocarbonylation of aryl halides. In the presence of a catalytic amount of palladium and TCT/formamide reagent, a range of aryl halides (X = Cl, Br, I) were converted into amides efficiently in N,N‐dimethylformamide at 120 °C.

Catalytic and kinetic investigation of the encapsulated random alloy (Pdn-Au110-n) nanoparticles

Generation six hydroxyl terminated PAMAM dendrimer was used as template for the synthesis of several palladium-gold random alloy nanoparticles. The synthesis process was monitored using UV–spectroscopy. The microscopy image of the alloy nanoparticles was captured by transmission electron microscopy and their average size was compared to the theoretical value. Catalytic oxidation of morin by hydrogen peroxide was performed to investigate the activity of the alloy nanoparticles. The Langmuir–Hinshelwood approach was used to conduct a full kinetic evaluation of the catalytic process. The catalytic activity exhibited by the alloy nanoparticles demonstrates a proportional increase with the relative palladium amount. The encapsulated alloy and mono metal nanoparticles remained narrowly dispersed after the reaction.

Immobilized Pd on (S)‐methyl histidinate‐modified multi‐walled carbon nanotubes: a powerful and recyclable catalyst for Mizoroki–Heck and Suzuki–Miyaura C–C cross‐coupling reactions in green solvents and under mild conditions

A stable and powerful heterogeneous palladium catalyst was synthesized using immobilized palladium on (S)‐methyl histidinate bonded onto the surface of multi‐walled carbon nanotubes. The catalyst was characterized using a combination of Fourier transform infrared and X‐ray photoelectron spectroscopies, transmission electron microscopy, X‐ray powder diffraction and inductively coupled plasma, thermogravimetric and elemental analyses. This new air‐ and moisture‐stable phosphine‐free palladium catalyst was found to be highly active and reusable in Mizoroki–Heck and Suzuki–Miyaura cross‐coupling reactions in poly(ethylene glycol) and aqueous ethanol as green solvents using an extremely small amount of palladium under mild conditions. Copyright © 2016 John Wiley &amp; Sons, Ltd.

ChemInform Abstract: An Efficient Method for the Synthesis of 2‐Methylallyl Alkenes by Cross‐Coupling Reactions.

To obtain aromatic 2-methylallyl derivatives, cross-coupling reactions between 2-methyl-2-propen-1-ol and various boronic acids were studied. Among allylic alcohols described for such cross-coupling reactions, 2-methyl-2-propen-1-ol has a low reactivity. Indeed, this substrate did not react with several boronic acids under the previously described conditions and new reaction conditions were investigated. We describe herein a new protocol with small amounts of palladium and ligand, without any additive solvent and under microwave heating. A subsequent simple distillation process not only leads to the product, but also allows the ‘reagent–solvent’ to be recycled for further cross-coupling reactions, without loss of yield. Scope and limitations were studied. Furthermore, when this easy cross-coupling reaction was extended to a wide range of organoboronic acids, high functional group tolerance was observed and a new series of alkenes was synthesized in good yields.

Highly efficient Pd-doped ferrite spinel catalysts for the selective catalytic reduction of NO with H2 at low temperature

Palladium-doped ferrite spinels with various divalent metals (Co, Cu or Zn) were prepared using the sol–gel auto-ignition method for use in the selective catalytic reduction of NO with hydrogen (H2-SCR). The activity of the Co–FePd catalyst was greatly enhanced by adding a small amount of palladium and resulted in approximately 96% NO conversion in the 170–250°C range. In TPD and TPR analyses, Co–FePd exhibited a larger peak area and a lower reductive temperature than the other studied materials, indicating that this catalyst possesses stronger reduction ability and larger acidity; these properties were very important for the catalytic performance of Co–FePd, which showed the best SCR activity of the tested materials. The catalytic activities ranked in the following order: Co–FePd>Zn–FePd>Cu–FePd. Adding H2O to the reacting gas mixture slightly decreased NO conversion by the Co–FePd oxide. When the H2O content was increased from 3% to 5%, no further decline of NO conversion occurred. The presence of 100ppm SO2 in the gas phase decreased the SCR activity of Co–FePd by approximately 19%, but no further deactivation was observed when the concentration was increased to 150ppm. When SO2 was removed from the feed stream, NO conversion recovered rapidly; however, the conversion was not restored to the original level, indicating that SO2 has both a reversible and an irreversible effect on the H2-SCR reaction.

Evaluation of Ability of Hydrogen Absorption in SAB-16/Pd Nanostructure Composite

The purpose of this work was to study the hydrogen adsorption on the surface of mesoporous materials based on silica (SBA-16) modified with palladium via temperature. Since mesoporous silica materials have a high specific surface area, and the ordered mesoporous size of 2-10nm, they are suitable for adsorption and storage of hydrogen. SBA-16 is suitable for this purpose due to its cubic crystalstructure and open pores. Single-stage sol-gel method was used to produce nanostructure composite from salt of palladium (PdCl3) and mesoporous silica precursor. The aging time was selected as 12 hr at 80 C. Furthermore, the obtained materials were heated at 550 C for 6 hr to remove surfactant and to form pores. Then the materials were characterized by large angle and small angle x-ray diffraction analysis, and hydrogen absorption analysis at upto 200kPa pressure at three different temperatures of -196 C (77 K), -123 C (150 K) and 30 C (303 K). Furthermore, adsorption-desorption of nitrogen gas was studied. The surface morphology was observed by field emission scanning electron microscope (FESEM). In addition, the amount of palladium, oxygen, and silicon were measured by using energy dispersive spectroscopy (EDS). Finally, the functional groups on the surface of mesoporous silica materials were evaluated using Fourier transform infrared spectroscopy (FTIR). The results of XRD and EDS analyses confirmed the presence of palladium and palladium oxide in mesoporous amorphous silica. In addition, BET results showed that addition of palladium in SBA-16 decreased the surface area, and produced 791 and 538m/g for SBA-16 and SBA-16/Pd, respectively. Hydrogen absorption in nano structure composite was decreasing with temperatur in comparison with SAB-16. On the other hand, the maximum hydrogen absorption in the nano structure composite containing palladium was obtained at -196 C (77 K).

Solar water-splitting using palladium modified tungsten trioxide-titania nanotube photocatalysts

Palladium modified tungsten trioxide-titania nanotubes (WOTNs) with different amounts of palladium were prepared by two methods; photo-assisted deposition and one-step electrochemical anodizing method. The resulting samples were characterized by X-ray diffraction, field emission scanning electron microscope, ultraviolet–visible spectroscopy and energy dispersive X-ray spectrometer methods. The photocatalytic water splitting was used as a model reaction to evaluate the photocatalytic activity of the obtained samples. The photocatalytic performance was examined under xenon lamp irradiation in 1 M NaOH electrolyte. All palladium modified samples showed photocatalytic properties superior to that for the bare WOTNs sample. The total amount of H2 evolved on the Pd/WOTNs2 sample was 2.5 times higher than that on the bare WOTNs sample. These new photoanodes showed enhanced high photocurrent density with good stability and are highly promising photoanodes for photocatalytic hydrogen production.

Palladium(0)-catalysed synthesis of 2,3- and 3,4-unsaturated aryl β-O-glycosides

Arylation of 6-O-tert-butyldiphenylsilyl-3,4-di-O-isobutyloxycarbonyl-d-glucal (3) with various phenols in the presence of a catalytic amount of palladium(0) gave the corresponding 2,3- and 3,4-unsaturated β-O-glycosides. The reaction is stereospecific, in all cases, only the β-anomer is formed.

An Efficient Method for the Synthesis of 2-Methylallyl Alkenes by Cross-Coupling Reactions

To obtain aromatic 2-methylallyl derivatives, cross-coupling reactions between 2-methyl-2-propen-1-ol and various boronic acids were studied. Among allylic alcohols described for such cross-coupling reactions, 2-methyl-2-propen-1-ol has a low reactivity. Indeed, this substrate did not react with several boronic acids under the previously described conditions and new reaction conditions were investigated. We describe herein a new protocol with small amounts of palladium and ligand, without any additive solvent and under microwave heating. A subsequent simple distillation process not only leads to the product, but also allows the ‘reagent–solvent’ to be recycled for further cross-coupling reactions, without loss of yield. Scope and limitations were studied. Furthermore, when this easy cross-coupling reaction was extended to a wide range of organoboronic acids, high functional group tolerance was observed and a new series of alkenes was synthesized in good yields.

Study of Aminosilane-Compound Modification Condition on Polished Silicon Wafer and Its Influence on the Adhesion of Electroless Nickel/Phosphorous Film

Electroless deposition (ELD) of nickel/phosphorous (Ni/P) layer has been a special interest in modern technique, especially in the production of diffusion barriers in the silicon industry [1]. The crucial part of ELD is a catalytic reaction that needs a trace amount of palladium [2] as the activator to lower the activation energy of metal formation. Due to the adhesion of ELD Ni/P film is associated with the interfacial property of catalyst and silicon surface. In order to increase the bridging between the silicon substrate and palladium catalyst, modifying silicon surface with organo-silane compound such as 3-[2-(2-aminoethylamino)ethylamino] propyl-trimethoxysilane (ETAS). The ETAS then form a self-assembled monolayer (SAM) to facilitate the adsorption of palladium catalyst [3]. However, it is known that the SAM formation is very sensitive to process condition such as soaking time, soaking temperature and solvent agents. In this study, the ETAS modification condition on silicon wafer is investigated. In particular, the ETAS-modified film was fabricated by a wet-soaking method and the effects of soaking time, soaking temperature and solvent agents onto silicon surface were discussed. As shown in Fig 1, the images of AFM with various soaking time of ETAS-modified silicon surface showed significant difference; this means that the long soaking time did influence SAM formation. Finally, the adhesion of ELD Ni/P on ETAS-modified silicon surface with different process parameters is discussed. REFERENCES [1] A. Brenner, G.E. Riddell, J. Res. Nat'l Bur. Std. 37 (1946) 31. [2] L. Li, B. Liu, Mater. Chem. Phys. 128 (2011) 303. [3] T. C. Wei, T. P. Pan, C. M. Chen, K. C. Lai, C. H. Wu, Electrochem. Commun. 54 (2015) 6 Figure 1

Hydrotalcite derived (Cu, Mn)–Mg–Al metal oxide systems doped with palladium as catalysts for low-temperature methanol incineration

Hydrotalcite derived (Cu, Mn)–Mg–Al mixed metal oxides, synthesized by coprecipitation method, were found to be effective catalysts for methanol incineration. Copper and/or manganese oxides deposited on commercial γ-Al2O3 and MgO were used as the reference catalysts. Cu–Mg–Al–O mixed oxide system was found to be the most active catalysts in a series of the hydrotalcite originated metal oxides and supported samples. On the other hand, copper deposited on Al2O3 and MgO supports were significantly less active than the hydrotalcite derived catalysts. Activity of the catalysts was improved by deposition of small amount of palladium (0.5wt.%). Temperature-programmed surface reaction method (CH3OH-TPSR) and in situ Fourier-transform infrared spectroscopy (FT-IR) were employed to study the species formed on the catalyst surface during the process of methanol oxidation.

Methane oxidation over Pt, Pt:Pd, and Pd based catalysts: Effects of pre‐treatment

This paper presents a comparison of the activity for methane oxidation of selected commercial platinum, palladium, and platinum‐palladium supported catalysts. Precious metal loadings are typical of those found in the catalytic converters for lean‐burn natural gas engines. Experiments are presented for de‐greened as well as hydrothermally aged catalysts, both in the presence and the absence of water. For the platinum catalyst, fraction conversion of methane is shown to be independent of methane concentration, while for the palladium‐containing catalysts a dependence of conversion on methane partial pressure is observed. For catalysts containing palladium, reduction in hydrogen gives an increase in methane conversion activity, although the increase is subsequently lost in the oxidizing atmosphere. Hydrothermal aging of the platinum catalyst causes a relatively large and permanent loss in methane oxidation activity, while the palladium‐based catalysts showed more resistance to deactivation. Adding a small amount of palladium to the platinum catalyst provides an overall improvement in performance.

The thermal behavior of Pd on graphene/Ru(0001)

The thermal behavior of various amounts of palladium deposited onto graphene/Ru(0001) at room temperature was investigated by X-ray photoelectron spectroscopy (XPS) and infrared reflection absorption spectroscopy (IRAS) of adsorbed CO. IRAS spectra of adsorbed CO on palladium deposited onto the graphene layer reveal the formation of defect-rich, highly-stepped and/or nanoparticle-typed palladium clusters. Annealing to temperatures below ~900K, palladium clusters mainly experience agglomeration on the graphene layer, but at higher temperatures intercalation of palladium between the graphene layer and Ru substrate takes place. Eventually, palladium completely desorbs and the graphene layer dissolves into the ruthenium substrate at 1400K. Even though the annealing induces the intercalation and desorption of palladium, the topmost graphene layer stays intact without any physical damage at and below 1300K.

Diastereoselective Synthesis of Six‐Membered Carbocyclic Spirooxindoles via 6π‐Electrocyclization of 3‐Dienylidene‐2‐ oxindoles

AbstractThe Wittig reaction of isatin derivatives with Morita–Baylis–Hillman bromides of cinnamaldehydes afforded 3‐dienylidene‐2‐oxindoles. These trienes were converted into the corresponding spirooxindoles in a stereoselective manner in refluxing toluene in good yields. The diastereomeric spirooxindoles could be obtained stereoselectively by adding a catalytic amount of palladium(II) acetate via the palladium‐catalyzed isomerization of EEE‐trienes to ZEE‐trienes followed by a more facile 6π‐electrocyclization process. The obtained spirooxindoles could be further functionalized by palladium‐catalyzed oxidative arylation, thionation with Lawesson’s reagent, catalytic hydrogenation and Friedel–Crafts‐type reaction.magnified image