Small Amounts Of Palladium Research Articles

A Nickel/Palladium/Ruthenium-Graphene based nanocatalyst for selective catalytic hydrogenation of vegetable oils

The catalytic hydrogenation of vegetable oils has long been the subject of study. Indeed, the reduction of un-saturations can to improve stability and increase properties suitable for a wide range of applications. Moreover, even with so much effort, the results are still far from the objectives of obtaining cis isomer of monoenes in the presence of a low amount of stearic acid. A new catalyst, obtained from a one-step synthesis, operating in mild conditions with high activity and full selectivity towards the cis configuration of 9-octadecanoic acid was proposed. A Ni/Pd/Ru active phase, with surfactant chains surfaces conjugated, results dispersed on few-layer graphene for increased efficiency exploiting the adsorbent properties of the support.The results demonstrate that the nano-hybrid made up of cheap and available Ni with very small amounts of palladium and ruthenium, allows achieving during hydrogenation of canola oil favorable cis-C18:1/C18:0 ratios, at a low catalyst loading of 1 wt.%. The addition of the Ru active phase allows successfully achieving up to 75.3 wt.% cis C18:1, and 2.46 wt.% of stearic acid, after 60 min. Additionally, it is worth noticing that only 2.6 wt.% of cis C18:1 is constituted of cis positional isomers. The graphene stabilizing nanoparticles ensures catalyst stability over cycles of use.

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.

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.

Oxidation of formaldehyde, carbon monoxide and methanol over manganese-cerium-aluminum oxides supported on cordierite monoliths

Catalytic oxidation of formaldehyde, carbon monoxide, and methanol over cordierite-supported manganese-cerium-aluminum mixed oxides was investigated in a laboratory reactor. The activities of base metal oxides (BMO) comprising 27% MnO2, 21% CeO2, and 52% Al2O3 supported on cordierite monoliths calcined at 1,000 °C for 3 h in air dropped very rapidly due to the migration of mobile silicon dioxide (SiO2) from the cordierite to the base metal oxides to react with or physically block the active catalysts. To immobilize migrating SiO2, barrier coats composed of alkali metal (Ba, Sr, Ca, Mg) oxides and alumina were applied to the cordierite prior to coating with active base metal oxides. The base metal oxides supported on cordierite monoliths pretreated with BaO-Al2O3 barrier coats and calcined at 1,000 oC for 3 h in air, initiated the oxidation of HCHO, CO, and CH3OH at 150, 220, and 170 °C, respectively. These catalysts turned out to be more effective for the formaldehyde oxidation than 0.5% Pt/Al2O3 precious metal catalysts. Carbon monoxide and methanol oxidation conversions were comparable. The incorporation of small amount of palladium (0.147 wt%) to base metal oxides supported on cordierite monoliths pretreated with BaO-Al2O3 barrier coats, showed the superiority for HCHO, CO, and CH3OH oxidation to 0.5% Pt/Al2O3 precious metal catalysts. The temperatures of 50% conversion of formaldehyde, carbon monoxide and methanol were 70 °C lower over base metal oxides catalysts than over precious metal catalysts.

How Silver Powder Metallurgy Affects the Physical Properties of Low Temperature Firing Silver Conductor

With the implementation of RoHS (the Restriction of Hazardous Substance) Directive banning the use of Lead, Cadmium, Mercury and Hexavalent Chromium, hybrid microelectronic manufacturers are globally embracing the lead free movement. These manufacturers must not only understand the implications of their material choice but must be aware of the interaction between lead free solder alloys and their RoHS compliant thick film materials. It is commonly known that lead free solder alloys process at much higher reflow temperatures than lead containing solder which can directly impact the fired film leach resistance and the loss of adhesion. There are also other concerns; lead free solders alloys generally require a different organic flux system to promote wetting and reflow, but this change may cause a fired film conductor to leach more easily than the flux used in the lead containing solders. The use of lead free solders such as SAC305, SAC405 or 95/5 on a low firing (550–570 °C) pure silver conductor has the tendency of leaching the fired film more readily than conductors containing small amounts of palladium or platinum. Many of these situations provide new challenges for the hybrid circuit manufacturer. There is little information available regarding the effects of the lead free solders on low firing silver thick film conductors. This paper discusses the results of a newly developed Pb and Cd free silver thick film conductor paste with a modified silver powder metallurgy to improve the leach resistance, solder acceptance and adhesion using lead free solder. In addition, the pure silver conductor was fired on top of a low temperature dielectric paste. This conductor was evaluated by comparing lead free solder alloys to traditional tin-lead-silver solder alloys. This study included evaluations based on SEM photos, solderability, leach resistance, and initial and long term adhesions. Results are published describing the difference in behavior between the different solder alloys in conjunction with the different silver powder metallurgy.

Novel Nanoporous Au−Pd Alloy with High Catalytic Activity and Excellent Electrochemical Stability

A novel nanoporous gold−palladium alloy has been successfully fabricated by electrochemically dealloying a multicomponent metallic glass. In comparison with conventional nanoporous gold prepared by dealloying Au−Ag alloys, the nanoporous gold−palladium alloy shows much higher catalytic activity for electrooxidation of methanol as a free-standing electrode. Moreover, a small amount of palladium in the nanoporous alloy is found to dramatically improve the electrochemical stability of nanoporous gold.

Heck reaction catalyzed by Pd supported on LDH-F hydrotalcite

LDH-F hydrotalcite was used, for the first time, as an efficient and selective basic support for palladium catalyzed Heck reaction. The ligand-free heterogeneous catalyst Pd/LDH-F exhibits higher activity and selectivity in the Heck reaction of aryl bromides with styrene on small amount of palladium (0.1 mol% of Pd). The higher yields than those previously obtained with Pd containing layered double hydroxides (LDHs) are reached. The catalyst can easily be separated from the reaction mixture and reused after washing without loss in activity. The influence of the highly polarized basic fluoride ions on reaction performance is discussed in this study. Moreover, the influence of several fundamental parameters (nature of support, Mg/Al ratio, property of the Pd complex) on the reactivity is also discussed.

Hydrogen production via steam–iron reaction using iron oxide modified with very small amounts of palladium and zirconia

We investigated hydrogen production by the steam–iron reaction using iron oxide modified with very small amounts of palladium and/or zirconia at a temperature of 723 K and under atmospheric pressure. Reduction of iron oxide with hydrogen and oxidation of partially reduced iron oxide with steam (Fe 3O 4 + 4H 2 ↔ 3Fe + 4H 2O) were repeated in the range of reduction degree of 30–50 mol%. Changes in the weight of the samples were monitored using a tapered element oscillating microbalance (TEOM) to control the degree of reduction. Unmodified iron oxide caused significant deactivation due to sintering with increasing number of redox cycles. The addition of a very small amount (0.23 mol%) of palladium or zirconia onto the surface of the iron oxide enhanced the reduction and/or oxidation of the partially reduced iron oxide, which suppressed sintering. Palladium accelerated both the reduction and oxidation rates of partially reduced iron oxide, while zirconia increased only the oxidation rate. Addition of both palladium and zirconia together to the iron oxide resulted in marked enhancement of both reduction and oxidation.

Hydrogen desorption kinetics of nanostructured MgH 2 composite materials

In order to investigate the microscopic mechanism of hydrogen desorption we have studied ball-milled magnesium-composite materials with a relatively large volume fraction of additives. After ball milling the microstructure typically shows additive particles covered with a film of MgH 2 as investigated by scanning electron microscopy and energy-dispersive X-ray microanalysis. Depending on the milling time and material used as additive, the desorption of hydrogen takes place at a far lower temperature than in pure MgH 2 as studied by thermal desorption spectroscopy. In the next step we developed a new method to use only small volume fractions of additives in order to minimize the amount of additive material and maximize the percentage of hydrogen storage material. Therefore, MgH 2 was sputter-deposited by palladium and successively ball milled to achieve a composite material with finely dispersed metallic additives. The desorption kinetics could be strongly improved even though only small amounts of palladium were added. The new method of ultra-fine dispersion may lead to MgH 2 composite materials with a high storage capacity of hydrogen accessible at moderate temperatures.

Activity enhancement of Ag/mordenite catalysts by addition of palladium for the removal of nitrogen oxides from diesel engine exhaust gas

Various Ag-Pd/mordenite catalysts were prepared on washcoated honeycombs and tested in terms of NO x removal from diesel exhaust gas with (CH 3) 2O as a reducing agent at a practical high level of space velocity. The activity was dependent upon the palladium loading. In terms of NO x removal, the order of catalytic activity was Ag(3)/Pd(0.01)/mordenite > Ag(3)/Pd(0.1)/mordenite > Ag(3)/mordenite catalyst > Ag(3)/Pd(1.0)/mordenite. It was found that a relatively small loading of palladium on Ag/mordenite catalysts led to a significant improvement in catalytic activity over a wide range of temperatures. The properties of these catalysts were also investigated by the NH 3 temperature programed desorption (TPD) and BET method. It was found that Ag(3)/Pd(0.01)/mordenite had a larger amount of acid sites. It was concluded that Ag/mordenite catalyst with a small amount of palladium can effectively remove NO x over a wide range of temperatures using (CH 3) 2O as a reducing agent.

液‐液抽出法による廃コンデンサからのパラジウムの回収

In the manufacturing process of multi layer ceramic chip capacitor, some unqualified products are produced and discarded as an industrial waste. Such a waste consists of barium titanate dielectrics and contains small amount of palladium as inner electrode. In order to recover and recycle palladium from the waste, liquid-liquid extraction was applied and investigated.Extraction behaviors of palladium and barium titanate were first examined using n -butanol, iso-octane and kerosene as organic phases at various pH. Palladium was extracted into n-butanol fairly well at the wide pH range of 1.0-10.5. On the contrary, barium titanate was not extracted almost entirely at the same conditions. Therefore, it was estimated that n-butanol was suitable organic phase for the separation of palladium from ceramics. When iso-octane or kerosene was used as an organic phase, large amount of barium titanate transferred into the oil phase at the wide pH range except high acidity, so that successive extraction of palladium from ceramics could not be expected except in high acidic medium. It was also shown that the addition of dodecylammonium acetate (DAA) as a collector was effective to promote the recovery of palladium in n-butanol.Then, the extraction was conducted for the practical waste of ceramic capacitor using n-butanol as an organic phase under the condition of 200mg·dm-3 DAA and pH 1.0. As a result, it was found that palladium was effectively separated with the recovery of 96.8% and the yield of about 10%, and that the product was upgraded to 34.4% palladium, about 10 times higher than the feed.

An improved method for the separation of 111Ag from irradiated natural palladium

A simple, high yield method for the separation of 111Ag by liquid/liquid extraction from irradiated natural palladium for nuclear-medical purposes is described. In a first step 111Ag is extracted almost quantitatively, together with a small amount of palladium, from an aqueous solution into toluene by complexation with triphenylphosphine. Using the different chemical and physical properties of the two elements 111Ag is subsequently re-extracted selectively into a convenient buffer solution. The overall yields of 111Ag are better than 70% and palladium is depleted by a factor of up to 27,000. The procedure takes about 2–3 h.

５，１０，１５，２０‐テトラキス［４‐（トリメチルアンモニオ）フェニル］ポリフィリンを用いる微量パラジウム（ＩＩ）の吸光光度定量

5,10,15,20-テトラキス[4-(トリメチルアンモニオ)フェニル]ポルフィリン (ttmapp) とパラジウム(II) との錯形成反応について検討し, ttmapp の Soret 帯の減少を利用する吸光光度定量法を開発した。パラジウム(II)と ttmapp の反応は常温では非常に遅いが, pH を5として L-アスコルビン酸ナトリウムを加えることにより常温で定量的に反応した。pH 1.2 以下で ttmapp (λmax=432nm) およびパラジウム(II)錯体 (λmax=409nm) のモル吸光係数は, それぞれ 5.14×105dm3・mol-1・cm-1,3.06×105dm3・mol-1・cm-1 であった。サンデル感度は 0.205 ngPdcm-2, 70.6 ppb のパラジウム(II)を20 回測定したさいの相対標準偏差は 0.56% であった。28 種の金属イオンの妨害およびその除去法を検討し, 白金族のイオンに対しても選択的な定量法となった。銅イオンが共存する場合は触媒の選択によりパラジウム(II), 銅(II)の分別定量が可能となった。

Preparation and Properties of a New Thick Film System

Work has been carried out to develop a new ruthenium oxide based thick film resistor whose resistance is independent of the contact area of the conductor to the resistor. Such a resistor can then be combined with a low cost silver conductor.It has been found that such a resistor can be made by doping a ruthenium oxide based thick film resistor with up to several percent of gold. With such a material it is possible to use silver or palladium silver (containing only very small amounts of palladium) as an electrode material and very few interactions have been found to occur between the resistor and electrode. Such a gold doped ruthenium oxide thick film resistor using silver electrodes has some major advantages as follows:-1. The resistor size can be made much smaller than normal.2. The design of a thick film hybrid circuit becomes easier.3. The resistor cost can be reduced.

Mikrosondenuntersuchungen an bestrahltem urancarbid

A shielded Cameca microbrobe, MS 46, was used to examine a UC sample canned in SAP and irradiated to a burnup of 0.7%. An annular zone at about 40% of the outer sample radius was seen to contain precipitates loaded with fission products: microbrobe analysis showed the precipitates to be U 2 (Tc, Ru, Rh)C 2. Small amounts of palladium can be stabilized in this phase. Zirconium and molybdenum were verified in homogeneous distribution in the fuel. The Vickers hardness of the irradiated UC is 1000–1200 kp/mm 2. No signs of incompatibility with the canning material were detected.

Separation and determination of small amounts of palladium and platinum

A procedure is described for the separation of 20 to 100μg of Pd(II) from 100 to 300μg of Pt(IV) in a mixture. The method is based on the selective separation of Pd(II) on silica gel, leaving Pt(IV) in the solution phase. Complete recovery of Pt(IV) in the supernate has been checked with197Pt as the radioactive indicator. The deposited palladium is extracted with dil. HCl, and the separated components are determined spectrophotometrically. A possible mechanism has been suggested.

Spectrographic Determination of Palladium in Doré Metal

A convenient spectrographic procedure for the determination of small amounts of palladium in Dore metal containing varying amounts of copper and gold is described. Copper in excess of 0.4% produced a marked enhancement of the palladium and silver line intensities, thereby prohibiting the use of a single working curve. A number of working curves were prepared, each corresponding to a definite copper concentration and, in the analysis of a Doré metal sample, the copper-silver intensity ratio served to indicate the position of the proper working curve The influence of gold was significant only when its concentration exceeded 9% The procedure was employed to determine 45 to 800 ppm. of palladium in Doré metal and very much smaller concentrations of palladium (down to 0 05 ppm. in a 3 assay-ton sample) in ores, copper concentrates, blister copper and other metallurgical products.