Showing papers on "Reducing agent published in 1998"

Electroless plating processes

Abstract: The invention includes processes for combined polymer surface treatment and metal deposition. Processes of the invention include forming an aqueous solution containing a metal activator, such as an oxidized species of silver, cobalt, ruthenium, cerium, iron, manganese, nickel, rhodium, or vanadium. The activator can be suitably oxidized to a higher oxidation state electrochemically. Exposing a part to be plated (such as an organic resin, e.g. a printed circuit board substrate) to the solution enables reactive hydroxyl species (e.g. hydroxyl radicals) to be generated and to texture the polymer surface. Such texturing facilitates good plated metal adhesion. As part of this contacting process sufficient time is allowed for both surface texturing to take place and for the oxidized metal activator to adsorb onto said part. The part is then contacted with a reducing agent capable of reducing the metal activator to a lower ionic form, or a lower oxidation state. That reduction can result in the formation of metallic catalytic material over the surface of the part. The reduced metal activator can then function to catalyze the electroless deposition of metal such as copper from solution by contacting the part with the plating solution.

Reduction of Ag+ on Polyacrylate Chains in Aqueous Solution

Abstract: Silver ions are reduced in aqueous solutions that contain sodium polyacrylate or partly carboxylated polyacrylamide or glutaric acid. The reducing agent is the hydrated electron (generated γ-radiol...

Polymer-stabilised metal colloid solutions, method for producing said solutions and use of the same as catalysts for fuel cell

Abstract: The invention relates to a method for producing metal colloid solutions by reacting a platinum compound and optionally, one or more compounds of Rh, Ru, Ir or Pd with a reducing agent. At least one cation exchange polymer is used to stabilise the metal colloid solutions.

New Catalytic Properties of Iron Porphyrins: Model Systems for Cytochrome P450-Catalyzed Dehydration of Aldoximes

Abstract: Various iron porphyrin systems were found to catalyze the dehydration of aldoximes, such as heptanaldoxime or phenylacetaldoxime, into the corresponding nitriles under mild conditions (t = 20 °C, neutral or slightly acidic pH). In all these systems, the presence of both the iron porphyrin catalyst and a reducing agent is required, indicating that the active species is the iron(II) porphyrin. The most efficient systems used either an organosoluble iron porphyrin, such as Fe(OEP), in the presence of a carboxylic acid and zinc amalgam as reducing agent, or a water-soluble heme fragment of cytochrome c (microperoxidase MP-11) in the presence of dithionite. The catalytic activity of the systems was greatly increased when using electron-rich iron porphyrins bearing an electron-donating axial ligand, such as imidazole, and a carboxylic acid cocatalyst in close proximity to the iron center. The activity of the best systems was comparable to that of microsomal cytochromes P450 (between 1 and 10 turnovers per min)....

Molar mass control of poly(N-isopropylacrylamide) and poly(acrylic acid) in aqueous polymerizations initiated by redox initiators based on persulfates

Abstract: Poly(N-isopropylacrylamide) (PNIPAM) and poly(acrylic acid) (PAA) were synthesized by aqueous radical polymerization initiated by the redox couple ammonium persulfate/sodium metabisulfite. PNIPAM was also synthesized by using a similar redox system: ammonium persulfate/2-aminoethanethiol hydrochloride (AET), the reducing agent being in this case a well known chain transfer agent. The final products were characterized by size exclusion chromatography. The influence on the weight-average molar mass (Mw) of several factors, such as monomer concentration and ionic strength of the reaction solution, were investigated. It was found that the concentration of ammonium persulfate does not practically affect the Mw of the products for both polymers investigated and independently of the reducing agent used. On the contrary, for constant monomer concentration, Mw is inversely proportional to the concentration of the reducing agent, either sodium metabisulfite or AET. This behaviour, combined with similar observations concerning the synthesis of polyacrylamide and other redox initiator systems containing metabisulfite as reducing agent, proves the special role of this reducing agent in the aqueous radical polymerizations.

Method of making iron and steel

Abstract: Molten iron is prepared by (1) providing iron oxide and a carbonaceous reducing agent; (2) preparing a shaped product from the carbonaceous reducing agent and the iron oxide; (3) preparing solid reduced iron from the shaped product, wherein the solid reduced iron has a metallization of at least 60 %, a specific gravity of at least 1.7, and a carbon content of at least 50 % of the theoretical amount required for reducing the iron oxide remaining in the solid reduced iron; and (4) before substantial cooling occurs, heating the solid reduced iron in an arc heating-type melting furnace at a high temperature. The molten iron can be prepared efficiently from iron ores of relatively low iron content without causing erosion of refractories, at high energy and high reduction efficiencies, and by a simple operation in a simple facility.

The role of acid sites in cobalt zeolite catalysts for selective catalytic reduction of NO x

Abstract: The role of the acidic support in ion-exchanged cobalt-zeolite, lean NOx catalysts has been determined by studying the individual steps in the selective reduction pathway. At a GHSV of 10,000 and reaction temperatures below 400°C, NO oxidation is not sufficiently rapid to obtain equilibrium over, for example, 1–4 wt% Co-mordenite catalysts. The NO oxidation rate increases in the order H+Co2+ Co oxide, and neither the number, nor the strength of the acid sites affects the specific rate of the Co2+ ions. For reduction of NO2 by propylene at 300°C and methane at 400°C, the formation of N2 is suggested to occur at support protons sites. In addition, the rate of N2 formation increases linearly with an increase in the number of acid sites, and the specific activity increases with an increase in acid strength. Cobalt (2+) ions do not contribute significantly to the formation of N2, but do non-selectively reduce NO2 to NO. It is proposed that the formation of N2 occurs by protonation of the reducing agent followed by attack of the carbocation by gas phase NO2. Thus, the selective reduction of NO requires two catalytic functions, metal and acid sites.

Time and temperature integrating indicator device

Abstract: Time and temperature integrating devices for providing a visually observable indication of cumulative thermal exposure are disclosed comprising (a) a substrate having thereon a thermally sensitive image-forming area comprising a combination of (i) an organic silver salt oxidizing agent and (ii) a reducing agent for the organic silver salt oxidizing agent, and (b) indicating indicia in association with the image forming area for indicating when the device has been exposed to a predetermined cumulative thermal exposure. In accordance with further embodiments of the invention, a process of applying such a device to a perishable product, and a perishable product having such a device applied directly thereto or to packaging thereof, are also disclosed. Time-temperature indicators in accordance with the invention undergo readily detectable changes can be easily optimized to match various rates of time-temperature dependent cumulative changes desired to be monitored for various products.

Selective removal of cesium from Acid solutions with immobilized copper ferrocyanide.

Abstract: Copper ferrocyanide can be immobilized on Chelex-20, a technical grade chelating resin, for selective removal of cesium from neutral to acidic solutions. The immobilized copper ferrocyanide is much easier to handle than the copper ferrocyanide powder in extraction and separation of cesium from aqueous solutions. In the presence of a reducing agent such as hydrazine, the immobilized copper ferrocyanide resin is able to remove 98% of the cesium from a simulated acid waste solution in one cycle of batch experiments. The resin shows promising properties for remediation of acidic nuclear wastes and for concentration of (137)Cs from environmental samples for quantitative analysis.

Method for the preparation of facial metal tricarbonyl compounds and their use in the labelling of biologically active substrates

Abstract: The invention relates to a method of preparing a compound of the general formula (I): fac-[M(CO)3(OH2)3]+ wherein M is Mn, ?99mTc, 186Re or 188?Re, by reacting a metal in the permetallate form with carbon monoxide and a reducing agent, characterized in that a mixture of a base, a reducing agent soluble in water but not substantially decomposed by water, and optionally a stabilizing agent is solved in a water containing solvent system containing a solution of the metal in the permanganate, pertechnetate or perrhenate form in the presence of carbon monoxide and optionally in the presence of a halide. The invention further relates to a method of preparing a labeled compound with the aid of the compound of general formula (I), to a method of direct preparation of labeled compounds, to a method of labeling of substrates such as amino acids, peptides, proteins, sugars, small receptor binding molecules and body cells with the aid of compound of general formula (I) and to a kit for the preparation of a labeling composition and a kit for the preparation of a diagnostic of therapeutic pharmaceutical composition.

Selective catalytic reduction of NO with C2H4 over Cu/ZSM-5: Influences of oxygen partial pressure and incorporated rhodia

Abstract: Catalytic activities of copper-exchanged ZSM-zeolites for the reduction of nitric oxide to nitrogen using ethylene as reducing agent in the presence or absence of oxygen are compared with those of Rh-ZSM-5 zeolites and binary Cu/Rh-ZSM-5 catalysts at 623–823 K. Copper ZSM-5 systems with high copper loadings (> 2.1) are shown to be much more active in the presence of oxygen, in marked contrast to Rh ZSM-5 catalysts which were more active in its absence. Binary ZSM-5 catalysts containing both copper and rhodium maintained intermediate activity in both conditions. A sample of Cu ZSM-5 containing only 1.8% copper also evidenced some activity in both conditions, which could be understood on the basis of catalytic action by copper ions within the zeolitic framework, allied to inherent Bronsted acidity of the latter. Comparative catalytic data are presented for the oxygen partial pressure dependence of the conversion to nitrogen over all catalysts at 673 K. These delineate the interplay between selective catalytic reduction (SCR) of NO by C2H4 and ethylene oxidation by dioxygen. Techniques utilised to characterise the catalysts include: powder XRD, TPR in H2, and TPD of O2.

Promotional effect of H2O on the activity of In2O3-doped Ga2O3-Al2O3 for the selective reduction of nitrogen monoxide

Abstract: Effect of metal oxide additives on the catalytic performance of Ga2O3–Al2O3 prepared by the sol–gel method for the selective reduction of NO with propene in the presence of oxygen was studied. Of several metal oxide additives, the addition of In2O3 enhanced drastically the activity of Ga2O3–Al2O3 for NO reduction by propene in the presence of H2O. In addition, the activity of In2O3‐doped Ga2O3–Al2O3 catalyst was extremely intensified by the presence of H2O below 350°C. The promotional effect of H2O was interpreted by the suppression of undesirable propene oxidation and the removal of carbonaceous materials deposited on the catalyst surface. We also found that close interaction of In2O3 and Ga2O3 is necessary for the enhancement of activity by H2O. A lot of hydrocarbons except methane and oxygenated compounds served as good reducing agents, among which propene and 2‐propanol were the most efficient ones. In2O3‐doped Ga2O3–Al2O3 catalyst was capable of reducing NO into N2 quite efficiently in the presence of H2O at a very high space velocity.

Kinetic and solvent extraction studies of the selective reduction of np(vi) by new salt-free reducing agents

Abstract: A variety of salt free organic reducing agents (carboxylic acids, aldeiiydes, ketones, guanidines and substituted hydrazines) have been screened for their reactivity with Np(VI) and Pu(IV) ions. The objective was to find reductants that have fast kinetics for Np(VI) reduction but which also showed a high selectivity for Np(VI) reduction over Pu(IV). Substituted hydrazines, particularly 1,1-diniethyl hydrazine and tert-butyl hydrazine, were shown to be the most promising of the screened reductants. The kinetics of Np(VI) and Pu(IV) reduction reactions with 1,1-dimethyl hydrazine and tert-butyl hydrazine were studied in greater detail and demonstration solvent extraction experiments were performed. The reduction of Pu(IV) was shown to be enhanced in the presence of U(VI) and this made 1,1-diniethyl hydrazine unsuitable as a selective reductant. Tert-butyl hydrazine may however show some promise as a selective reductant for Np(VI) under carefully controlled conditions.

Photon reducing agents and compositions for fluorescence assays

Abstract: The present invention provides a method for reducing undesirable light emission from a sample using at least one photon producing agent and at least one photon reducing agent (e.g. dye-based photon reducing agents). The present invention further provides a method for reducing undesirable light emission from a sample (e.g., a biochemical or cellular sample) with at least one photon producing agent and at least one collisional quencher. The present invention also provides a method for reducing undesirable light emission from a sample (e.g., a biochemical or cellular sample) with at least one photon producing agent and at least one quencher, such as an electronic quencher. The present invention further provides a method of determining bound and free analyte in a sample using at least one photon reducing agent. The present invention also provides a method of screening test chemicals in fluorescent assays using photon reducing agents. The present invention also provides compositions and kits for practicing these methods.

Effects of Oxidation of Immobilized Poly(L-Cysteine) on Trace Metal Chelation and Preconcentration

Abstract: The on-line reversible oxidation of poly(l-cysteine) immobilized on controlled-pore glass (PLC−CPG) was demonstrated using 1% hydrogen peroxide, aerated buffer solution, and Cu(II) as oxidizing agents and dithiothreitol (DTT) as a reducing agent. Cd breakthrough curves on the oxidized forms of PLC−CPG, used as an ion exchanger, revealed that hydrogen peroxide was an effective oxidizing agent for the sulfhydryl groups and eliminated all of the strong binding sites for Cd, while oxidation by aerated water removed only 33% of the total Cd capacity after an 18-h reaction. A Cu(II) breakthrough curve on a partially reduced form of PLC−CPG showed that strong Cu binding sites were present and that the Cu(II) oxidized PLC−CPG, most likely through the binding of Cu(II) to sulfhydryl binding sites, followed by their oxidation to disulfides with the production and likely binding of Cu(I). At least 10% of the bound Cu had to be removed using KCN, which suggested Cu(I) was strongly complexed. Oxidation of PLC−CPG usin...

Synthesis of metal complexes of 2,9-bis(2-hydroxyphenyl)-1,10-phenanthroline and their DNA binding and cleaving activities

Abstract: A series of metal complexes that combine the structure of phenanthroline and salen have been synthesized and characterized by electron paramagnetic resonance spectroscopy. The effects of the 2,9-bis(2-hydroxyphenyl)-1,10-phenanthroline compounds complexed with CuII, NiII, CoII or MnIII on the temperature-dependent helix-to-coil transition of DNA have been measured. The interaction with DNA is metal-dependent and the highest stabilization is observed with the Co complex. The DNA cleaving activities have been studied with plasmid DNA and/or with a 32P-labelled duplex oligonucleotide depending on the redox properties of the complexes. The Cu complex is inactive whereas the Co chelate efficiently cleaves DNA in the presence of a reducing agent. Cleavage of DNA by the Mn complex can occur either in the presence of a reducing agent via the production of oxygen radicals (which are detected by EPR spectroscopy) or in the presence of an oxidant such as KHSO5. In both cases, the cleavage of nucleic acids is very efficient whereas no cleavage is observed with the Ni complex. The complexes of bis(hydroxyphenyl)phenanthroline with Mn and Co complement the tool-box of reagents available for cleavage of DNA.

Dissolved oxygen removal method using activated carbon fiber and apparatus thereof

Abstract: A dissolved oxygen removal method using an activated carbon fiber catalyst thereof which includes the steps of a reducing agent injection step for injecting a reducing agent into the water, a reactor entrance dissolved oxygen measuring step for measuring a concentration of a dissolved oxygen contained in a water, a water flow rate control step for controlling the supplied amount of the water, an activated carbon fiber catalyst reaction step for removing a dissolved oxygen contained in the water with the reaction between the reducing agent and the dissolved oxygen in an activated carbon fiber reactor in which an activated carbon fiber catalyst is packed, and a control step for controlling the feeding rate of the reducing agent in accordance with the water flow rate and the reactor entrance dissolved oxygen, for thereby extending the life time of the facility and decreasing the operational and maintenance costs by fully removing a dissolved oxygen in water used for an steam generator or cooling system.

Cyanide-free monovalent copper electroplating solutions

Abstract: A substantially cyanide-free plating solution for depositing copper from the monovalent ionic state, which includes a source of copper ions, a reducing agent capable of reducing divalent copper ions to monovalent copper ions, an alkali material in an amount sufficient to maintain the pH of the solution in the range of about 7 to about 10, and a complexing agent of an imide, such as succinimide, 3-methyl-3-ethyl succinimide, 3-methyl succinimide, 3-ethyl succinimide, 3,3,4,4-tetramethyl succinimide, or 3,3,4-trimethyl succinimide, or a hydantoin, such as dimethyl hydantoin. The substantially cyanide-free plating solutions may also include at least one of a conductivity salt, an additive to promote brightness, or an alloying metal. The reducing agent may be an alkali sulfite, alkali bisulfite, hydroxylamine, or hydrazine. The copper is typically provided in the form of CuC1, CuC12, CuSO4, or Cu20 in an amount sufficient to provide a copper ion concentration of from about 2 to about 30 grams per liter of solution, and the complexing agent is present in an amount sufficient to provide a molar ratio of copper ions to complexing agent of from about 1:1 to about 1:5, preferably about 1:4. The alkali material is typically NaOH, KOH, NH4OH, or Na2CO3, and the conductivity salt is typically NaC1, KC1, Na2SO4, K4P2O7, Na3PO4, C6H5Na3O7, C6H11NaO7, NH4C1, or KNaC4H4O6. Useful additives include organic amines or oxyalkyl polyamines, such as triethylene tetramine, tetraethylene pentamine, and polyoxypropyl-triamine. Methods for preparing such a solution for plating copper onto a substrate, and of plating copper onto a substrate with such a solution are also disclosed.