Showing papers on "Reducing agent published in 2002"

Method of growing electrical conductors

Abstract: A method for forming a conductive thin film includes depositing a metal oxide thin film on a substrate by an atomic layer deposition (ALD) process. The method further includes at least partially reducing the metal oxide thin film by exposing the metal oxide thin film to a reducing agent, thereby forming a seed layer. In one arrangement, the reducing agent comprises one or more organic compounds that contain at least one functional group selected from the group consisting of —OH, —CHO, and —COOH. In another arrangement, the reducing agent comprises an electric current.

A new concept for producing Ti sponge: Calciothermic reduction

Abstract: This article presents a new cell concept for the calciothermic reduction of titanium dioxide and an ongoing test program for its experimental verification. The thermochemical background of this concept is focused and a new cell design is described. This system consists of a single cell, where both the reduction reaction and the electrolytic reaction for recovery of reducing agent coexist in the same molten calcium-chloride bath. The theoretical electric energy requirement for this cell is about half of that for the magnesium electrolytic cell in the Kroll process.

Selective catalytic reduction

Abstract: A method of selectively catalysing the reduction of NO x in an exhaust gas flowing in an exhaust system of an internal combustion engine comprising a filter ( 40 ) for particulate matter comprising a catalyst capable of selectively catalysing the reduction of NO x with a reducing agent, which method comprising introducing a reducing agent, or a precursor thereof, into the exhaust gas and contacting the resulting gas with the filter ( 40 ).

Composition containing a polymerizable reducing agent, kit, and method

Abstract: The present invention provides a hardenable (i.e., curable by polymerization, crosslinking, ionic, or other chemical reaction) composition that includes polymerizable urea or thiourea compounds that function as reductants (i.e., reducing agents) in redox polymerization reactions.

Protein-Protected Nanoparticles from Rapid Expansion of Supercritical Solution into Aqueous Solution

Abstract: Nanocrystalline silver particles were prepared via a supercritical fluid processing technique RESOLV (Rapid Expansion of a Supercritical Solution into a Liquid SOLVent) coupled with chemical reduction. The preparation involved the rapid expansion of a supercritical ammonia solution of silver nitrate into an ambient solution that contained sodium borohydride or hydrazine as reducing agent and poly(N-vinyl-2-pyrrolidone) (PVP) or bovine serum albumin (BSA) protein as the protection agent for the resulting nanoparticle suspension. The nanoparticles were characterized using UV/vis absorption, X-ray powder diffraction, and transmission electron microscopy methods. The results show that the BSA protein-protected Ag nanoparticles are much larger than those obtained with PVP as protection agent under otherwise the same experimental conditions but still maintain relatively narrow size distributions. Mechanistic implications of the results are discussed.

Heterogeneous Palladium‐Catalysed Heck Reaction of Aryl Chlorides and Styrene in Water Under Mild Conditions

Abstract: The Heck reaction of chlorobenzene and substituted chlorobenzenes with styrene is performed in water using catalytic palladium on carbon. The presence of a reducing agent, a mild base, and a phase-transfer catalyst enhances the reactivity of chloroarenes. Transfer hydrogenation of the stilbene double bond to yield 1,2-diphenylethane is also observed in situ. The competing reactions in this system are haloaryl homocoupling and hydrodehalogenation. The effects of various process parameters on substrate conversion and product selectivity are examined for PhCl and PhBr and the unique role of the reducing agent is discussed. A series of filtration experiments indicate that, in this system, the catalysis is heterogeneous and not due to palladium leaching.

Self-Curing System For Endodontic Sealant Applications

Abstract: A two-part self-curing endodontic sealing system comprises a thiourea derivative, such as acetyl thiourea, and a hydroperoxide, such as cumene hydroperoxide. The thiourea derivative is used as a reducing agent and the hydroperoxide is used as an oxidizing agent.

Metal salt reduction to form alloy nanoparticles

Abstract: A method for making nanoparticles via metal salt reduction comprises, first, mixing metal salts in a solvent. Second, a reducing agent is added to the solvent at a temperature in the range of 100° C. to 350° C. Third, the nanoparticles dispersion is stabilized. Fourth, the nanoparticles are precipitated from the nanoparticle dispersion. Finally, the nanoparticles are re-dispersed into the solvent. The metal salt comprises a combination of FeCl 2 , FeCl 3 , Fe(OOCR) 2 , Fe(RCOCHCOR) 3 , CoCl 2 , Co(OOCR) 2 , Co(RCOCHCOR) 2 , and one of Pt(RCOCHCOR) 2 , PtCl 2 . The reducing agent comprises one of MBR 3 H, MH, M naphthalides, and polyalcohol; wherein R comprises one of H and an alkyl group, wherein M comprises one of Li, Na, and K. Long chain alkyl diols, and alkyl alcohol, can be used as a co-surfactant or a co-reducing agent to facilitate nanoparticle growth and separation.

Effects of thermal pretreatment on the redox behaviour of Ce0.5Zr0.5O2: isotopic and spectroscopic studies

Abstract: The temperature programmed reduction (TPR) of a single phase Ce0.5Zr0.5O2 solid solution is investigated by using 1H2/Ar and 2H2/Ar mixtures as reducing agents. The effects of mild (700 K) or severe (1273 K) pre-oxidation (MO, SO) on the TPR profile are analysed. It is observed that after SO pretreatment hydrogen activation/scrambling occurs at about 600 K and the reduction profile is characterised by a single reduction peak at 920 K. In contrast, a TPR/MO pretreatment of such SO sample leads to a facile hydrogen activation/scrambling and low temperature reduction profiles, the main reduction peak being observed at ca. 650 K. Using 1H2 and 2H2 as reducing agents, an isotopic effect is observed for the reduction processes with a peak occurring above 700 K, while equal activation energies are measured for those occurring below 700 K. This suggests that under the TPR conditions the surface reduction steps (activation of the reducing agent at the surface, surface reduction steps and water evolution) are not rate limiting for the low temperature reduction process, which is controlled by bulk diffusion, while some surface step (probably water formation) is limiting for the high temperature reduction. Studies by EPR on the nature of the oxygen species adsorbed on variously pretreated specimens and by FTIR of the methoxy species formed upon methanol adsorption on the same materials reveal that the main changes induced by high temperature calcination are related to segregation of ceria- and zirconia-type islands, with some surface enrichment in cerium probably occurring as well. Only subtle differences between SO and MO pretreated samples can be detected at either surface or bulk (XRD experiments) levels, in contrast with the significant modifications produced by the different pretreatments on the reduction characteristics of the sample.

Role of redox potential of hemoglobin-based oxygen carriers on methemoglobin reduction by plasma components

Abstract: A functional requirement for all hemoglobin-based oxygen carriers (HBOCs) is the maintenance of the heme-iron in the reduced state. This is necessary for the reversible binding/release of molecular oxygen and minimization of methemoglobin (Fe+3) formation. Acellular hemoglobins are especially susceptible to oxidation and denaturation. In the absence of the intrinsic reducing systems of the red blood cell, the reduced heme-Fe+2 can be oxidized to form increasing levels of methemoglobin that can give rise to free radicals and oxidative cellular damage. If acellular HBOCs are to be utilized as red cell substitutes for oxygen delivery, these carriers must be stabilized in the plasma, the carrier medium. Normal plasma contains reducing components, such as ascorbic acid and glutathione, that can afford protection to these acellular HBOCs through electron-transfer mediated processes. For these components to provide effective reduction to an HBOC, a favorable reduction potential difference must exist between the reducing agent and the HBOC. Using a modified thin-layer spectroelectrochemical method, a determination of the formal reduction potential (vs. Ag/AgCl) of several oxygen carriers, including monomeric myoglobin, tetrameric HbA and HbS, chemically cross-linked HbXL99alpha, polymerized oxyglobin (FDA approved for canine anemia), and the natural cross-linked polymeric Lumbricus hemoglobin, have been determined. In contrast to the negative formal reduction potentials (-155 to -50 mV) obtained for Mb, HbA, HbS, HbXL99alpha, and oxyglobin, Lumbricus hemoglobin exhibited a positive formal reduction potential (approximately 100 mV). These results may help explain the greater effectiveness of the tested reducing agents to reduce met Lumbricus hemoglobin, compared to the other HBOCs, back to the required reduced form necessary for physiological binding/release of oxygen. Each reducing agent was capable of reducing met Lumbricus hemoglobin to the fully reduced state, although the kinetics of these reactions were different. HbA, HbXL99alpha, and oxyglobin were only partially reduced (10 to 37%) by glutathione, beta-NADH, and ascorbic acid under similar conditions.

Process for producing water-absorbing resin

Abstract: A process for preparing a water-absorbent resin made from an α,β-unsaturated carboxylic acid as an essential monomer characterized in that the process comprises allowing a metal chelating agent to be present at any step in the process in an amount of 0.001 to 6 parts by weight, based on 100 parts by weight of the α,β-unsaturated carboxylic acid; and adding a reducing agent or an oxidizing agent thereto in an amount of 0.001 to 6 parts by weight, based on 100 parts by weight of the α,β-unsaturated carboxylic acid before initiation of drying and/or during drying of a gelated product containing a water-absorbent resin obtained by polymerization.

A new cross-linked quaternized-chitosan resin as the support of borohydride reducing agent

Abstract: A new cross-linked resin was prepared by an inverse emulsion method under the protection of amino group. The resin reacted with glycidyl trimethylammonium chloride to form the quaternary ammonium ion resin, whose chloride was exchanged with potassium borohydride to get the borohydride exchange resin (CBER). CBER was used as a new polymer-supported reducing agent for the reduction of carbonyl compounds to corresponding alcohols, and exhibited a relatively high chemoselectivity and possessed the advantage of easy work-up.

Method of cleaning membranes

Abstract: The present invention relates a method for cleaning polymeric microfiltration membranes and membrane units, and to compositions useful in such methods. The compositions include at least one soluble sulfite reducing agent and a compatible solvent.

Method and device for electrochemical formation of therapeutic species in vivo

Abstract: A device and method are provided for spontaneous electrochemical production of therapeutic species, in vivo. An active metal is implanted in the tissue. The metal undergoes corrosion, thus acting as a reducing agent to constituents in the tissue, so as to cause these constituents to form the therapeutic agents.

Catalytic Conversion of N2O to N2 over Metal-Based Catalysts in the Presence of Hydrocarbons and Oxygen

Abstract: The catalytic conversion of N2O to N2 in the presence or the absence of propene and oxygen was studied. The catalysts examined in this work were synthesized impregnating metals (Rh, Ru, Pd, Co, Cu, Fe, In) on different supports (Al2O3, SiO2, TiO2, ZrO2 and calcined hydrotalcite MgAl2(OH)8·H2O). The experimental results varied both with the type of the active site and with the type of the support. Rh and Ru impregnated on γ-alumina exhibited the highest activity. The performance of the above most promising catalysts was studied using various hydrocarbons (CH4, C3H6, C3H8) as reducing agents. These experimental results showed that the type of reducing agent does not affect the reaction yield. The temperature where complete conversion of N2O to N2 was measured was independent of the reductant type. The activity of the most active catalysts was also measured in the presence of SO2 and H2O in the feed. A shift of the N2O conversion versus temperature curve to higher temperatures was observed when SO2 and H2O were added, separately or simultaneously, to the feed. The inhibition caused by SO2 was attributed to the formation of sulfates and that caused by water to the competitive chemisorption of H2O and N2O on the same active sites.

Oxygen detecting composition

Abstract: The oxygen detecting composition of the present invention comprises a layered silicate, a cationic surfactant, an organic colorant, a reducing agent, and optionally a basic substance. The oxygen detecting composition is suitable for indicating the presence or absence of oxygen or the degree of oxygen concentration by its reversible color change because of its high light resistance, high heat resistance, transparency and translucency.

Exhaust gas purifying apparatus for internal combustion engine and control method thereof

Abstract: An exhaust gas purifying apparatus for an internal combustion engine includes plural catalysts provided in parallel. In a case where temperatures of the catalysts need to be raised, a catalyst is selected from among the catalysts and the exhaust gas is allowed to flow in the selected catalyst. In addition, the temperature of the selected catalyst is raised without using a reducing agent when the temperatures of the catalysts are lower than a temperature range in which the reducing agent can be purified. Alternatively, the reducing agent is supplied to the selected catalyst so as to raise the temperature thereof when the temperatures of the catalysts are equal to or higher than the temperature at which the reducing agent can be purified.

Shape-controlled synthesis of nanostructured gold by a protection–reduction technique

Abstract: We describe a novel method to control the shape and size of Au nanoparticles using a protection–reduction technique. The remarkable feature of this method is that the reducing and protecting agents were mixed first prior to addition to the solution of KAu(CN)2.The reactivity and concentration of reducing agent, the molar ratio of ascorbic acid (AA)/poly(vinylpyrrolidone) (PVP) and the redox potential of the Au complex anion have significant effects on the formation and growth of these novel nanostructures. The Au nanoparticles self-assembly into dendritic structures at molar ratios of AA/PVP > 7 while spherical and cubic nanoparticles form at ratios of AA/PVP ≤ 3 and 4–6, respectively. This simple and effective method can be used for other noble metals.

Method of semiconductor nanoparticle synthesis

Abstract: A Method is described for the manufacture of semiconductor nanoparticles. Improved yields are obtained by use of a reducing agent or oxygen reaction promoter.

Substrate (Ni)-catalyzed electroless gold deposition from a noncyanide bath containing thiosulfate and sulfite. I. Reaction mechanism

Abstract: Electroless gold deposition is known to take place on Ni-based substrates even when the conventional reducing agent is excluded from the autocatalytic bath containing thiosulfate and sulfite as ligands for gold ions. It is shown in this paper that the reaction of gold deposition from this bath on electroless Ni-B substrate is not autocatalytic but, instead, proceeds primarily by the mechanism of substrate catalysis with galvanic displacement playing a secondary role. It was established that sulfite serves as the reducing agent for the substrate-catalyzed gold deposition reaction.

Dosing system for dosing a reducing agent for exhaust gas aftertreatment

Abstract: The invention relates to a device for dosing a reducing agent, especially urea or a urea-water solution, for reducing the nitrogen oxides contained in the exhaust gas of an internal combustion engine. The invention also relates to a transport device (10) for transporting a reducing agent. Said transport device (10) is arranged in such a way that it can be fixed to or inside the reservoir (12). The transport device (10) forms a module which is separate from an apportioning device (32;52) containing a proportioning valve. Said apportioning device can be connected to the transport device (10) by means of a reducing agent line (38).

Enhancement of iron toxicity in L929 cells by D-glucose: accelerated(re-)reduction.

Abstract: It has recently been shown that an increase in the cellular chelatable iron pool is sufficient to cause cell damage. To further characterize this kind of injury, we artificially enhanced the chelatable iron pool in L929 mouse fibroblasts using the highly membrane-permeable complex Fe(III)/8-hydroxyquinoline. This iron complex induced a significant oxygen-dependent loss of viability during an incubation period of 5 h. Surprisingly, the addition of L-glucose strongly enhanced this toxicity whereas no such effect was exerted by L-glucose and 2-deoxyglucose. The assumption that this increase in toxicity might be due to an enhanced availability of reducing equivalents formed during the metabolism of L-glucose was supported by NAD(P)H measurements which showed a 1.5-2-fold increase in the cellular NAD(P)H content upon addition of L-glucose. To assess the influence of this enhanced cellular reducing capacity on iron valence we established a new method to measure the reduction rate of iron based on the fluorescent iron(II) indicator PhenGreen SK. We could show that the rate of intracellular iron reduction was more than doubled in the presence of L-glucose. A similar acceleration was achieved by adding the reducing agents ascorbate and glutathione (the latter as membrane-permeable ethyl ester). Glutathione ethyl ester, as well as the thiol reagent N -acetylcysteine, also caused a toxicity increase comparable with L-glucose. These results suggest an enhancement of iron toxicity by L-glucose via an accelerated (re-)reduction of iron with NAD(P)H serving as central electron provider and ascorbate, glutathione or possibly NAD(P)H itself as final reducing agent.

Depilatory compositions and articles and the use thereof

Abstract: The present invention relates to a composition or article containing at least one oxidizing agent and at least one reducing agent, wherein at least one of the at least one reducing agent is a depilatory agent, the equivalent ratio of the at least one oxidizing agent to the at least one reducing agent is less than 1:1, and the article is exothermic when wet with water, and the use thereof to remove hair from the skin.

Trehalose glass-facilitated thermal reduction of metmyoglobin and methemoglobin

Abstract: The reduction of ferric derivatives of hemeproteins in solution typically requires moderate to strong reducing agents. Reducing sugars are not adequate to reduce ferric myoglobins or hemoglobins under solution conditions favorable to protein stability. We find that embedding aquo-met derivatives of horse myoglobin and human adult hemoglobin in a glucose-doped glassy matrix derived from trehalose facilitates an efficient thermally initiated reduction that yields a five-coordinate high-spin ferrous heme. The trehalose glass plays a central role by stabilizing the reduction-prone bis-histidine heme (hemichrome) intermediate under the high-temperature conditions that favor the open reducing form of glucose. Due to glass-imposed limitations on conformational reorganization, this process has clear applications in biophysics where it can be used to generate nonequilibrium ferrous derivatives having the initial conformation of the aquo-met derivative. Since the glassy matrix can be redissolved to release the embedded protein, this technique is not only a basis for a relatively benign method of reducing hemoglobin-based blood substitutes that have undergone autoxidation during storage but may also be a way to reactivate stored proteins that have undergone oxidation.

Method for reducing the content of n2o and nox in gases

Abstract: A method for reducing the content of N2O and NOX in gases is disclosed, with addition of a gaseous reduction agent, in amounts necessary for the reduction of the NOx, in the presence of one or several zeolites loaded with iron, with no pores or channels in the crystal structure larger than 7 Angstrom, at temperatures less than 450 °C in the reaction zone. The flow rate of the gas mixture and/or the catalyst amount is thus selected that the required decomposition rate for N2O is achieved. The method is particularly suitable for application in production of saltpetre, in power stations and gas turbines.

Use of sulphur dioxide as reducing agent in cobalt leaching at Shituru hydrometallurgical plant

Abstract: Copper oxide ores deposits in the Katanga province of the Democratic Republic of Congo (DRC) contain at variable level cobalt oxide minerals. In contrast to copper oxide minerals which readily dissolve in the sulphuric acid solution, the cobalt oxide bearings are difficult to dissolve, especially if cobalt is present in the third oxidation state (Co2O3). This species become soluble after reduction of Co+3 in Co+2. In practice, the use of reducing agent is therefore necessary in order to transform the insoluble minerals into soluble cobalt sulphate species. The following reducing agents are currently used at the Shituru plant: ferrous ions, which are present in leach solutions, pulverised copper or sodium meta bisulphite (MBS). Due to the high consumption of reducing agents (0,8 t MBS/t of solubilized Co; 1,2 t Cu/t-Co), cobalt production is expensive. The use of sulphur dioxide as reducing agent was then investigated in order to reduce operating cost. This reagent also presents the advantage of sulphuric acid production during the leaching process. It has been added in the leaching vessel (tank). From the laboratory and industrial tests, selective leaching of cobalt (78%) has been performed. The cobalt leaching kinetic depend on sulphur dioxide dosage. Dissolution of copper, iron and manganese remained very low. No emanation of SO2 gas was observed during the process.