Showing papers on "Selective reduction published in 2015"

Metal−Organic Frameworks for Electrocatalytic Reduction of Carbon Dioxide

Abstract: A key challenge in the field of electrochemical carbon dioxide reduction is the design of catalytic materials featuring high product selectivity, stability, and a composition of earth-abundant elements. In this work, we introduce thin films of nanosized metal-organic frameworks (MOFs) as atomically defined and nanoscopic materials that function as catalysts for the efficient and selective reduction of carbon dioxide to carbon monoxide in aqueous electrolytes. Detailed examination of a cobalt-porphyrin MOF, Al2(OH)2TCPP-Co (TCPP-H2 = 4,4',4″,4‴-(porphyrin-5,10,15,20-tetrayl)tetrabenzoate) revealed a selectivity for CO production in excess of 76% and stability over 7 h with a per-site turnover number (TON) of 1400. In situ spectroelectrochemical measurements provided insights into the cobalt oxidation state during the course of reaction and showed that the majority of catalytic centers in this MOF are redox-accessible where Co(II) is reduced to Co(I) during catalysis.

Achieving Selective and Efficient Electrocatalytic Activity for CO2 Reduction Using Immobilized Silver Nanoparticles.

Abstract: Selective electrochemical reduction of CO2 is one of the most sought-after processes because of the potential to convert a harmful greenhouse gas to a useful chemical. We have discovered that immobilized Ag nanoparticles supported on carbon exhibit enhanced Faradaic efficiency and a lower overpotential for selective reduction of CO2 to CO. These electrocatalysts were synthesized directly on the carbon support by a facile one-pot method using a cysteamine anchoring agent resulting in controlled monodispersed particle sizes. These synthesized Ag/C electrodes showed improved activities, specifically decrease of the overpotential by 300 mV at 1 mA/cm2, and 4-fold enhanced CO Faradaic efficiency at −0.75 V vs RHE with the optimal particle size of 5 nm compared to polycrystalline Ag foil. DFT calculations enlightened that the specific interaction between Ag nanoparticle and the anchoring agents modified the catalyst surface to have a selectively higher affinity to the intermediate COOH over CO, which effectivel...

An Iron Electrocatalyst for Selective Reduction of CO2 to Formate in Water: Including Thermochemical Insights

Abstract: C–H bond formation with CO2 to selectively form products such as formate (HCOO–) is an important step in harnessing CO2 emissions as a carbon-neutral or carbon-negative renewable energy source. In this report, we show that the iron carbonyl cluster, [Fe4N(CO)12]−, is an electrocatalyst for the selective reduction of CO2 to formate in water (pH 5–13). With low applied overpotential (230–440 mV), formate is produced with a high current density of 4 mA cm–2 and 96% Faradaic efficiency. These metrics, combined with the long lifetime of the catalyst (>24 h), and the use of the Earth-abundant material iron, are advances in catalyst performance relative to previously reported homogeneous and heterogeneous formate-producing electrocatalysts. We further characterized the mechanism of catalysis by [Fe4N(CO)12]− using cyclic voltammetry, and structurally characterized a key reaction intermediate, the reduced hydride [HFe4N(CO)12]−. In addition, thermochemical measurements performed using infrared spectroelectrochemi...

Oxygen Plasma Induced Hierarchically Structured Gold Electrocatalyst for Selective Reduction of Carbon Dioxide to Carbon Monoxide

Abstract: Electrochemical reduction of CO2 into C1 products with high energy density has attracted attention due to the demands for renewable energy sources. Herein, we demonstrate a selective electrocatalytic CO2 reduction system where the cathode consists of hierarchically structured Au islands catalysts. To be more specific, the Au islands were prepared by oxygen plasma treatment on the Au foil to increase the current density for the selective production of carbon monoxide with over 95% of faradaic efficiency. Faradaic efficiency, production rate, and the onset potential for CO2 reduction were significantly improved by the expanded surface area compared with a polycrystalline Au electrode. Furthermore, the performance of CO2 reduction to CO was enhanced by adding ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate) which has high CO2-capture ability and catalytic activity. On the other hand, the rate-determining step of the Au electrode for the CO production determined by Tafel plots was found to be cons...

Nanostructuring gold wires as highly durable nano- catalysts for selective reduction of nitro compounds and azides with organosilanes

Abstract: A general method is developed to prepare durable hybrid nanocatalysts by nanostructuring the surface of gold wires via simple alloying and dealloying. The resulting nanoporous gold/Au (NPG/Au) wire catalysts possess nanoporous skins with their thicknesses on robust metal wires specified in a highly controllable manner. As a demonstration, the as-obtained NPG/Au was shown to be a highly active, chemo-selective, and recyclable catalyst for the reduction of nitro compounds and azides using organosilanes as reducing agents.

Selective reduction of nitro-compounds to primary amines by nickel-catalyzed hydrosilylative reduction

Abstract: Ni(acac)2 and PMHS were found to be an excellent catalytic system for the chemoselective transfer hydrogenation of nitro-compounds to primary amines. Under mild conditions a series of nitro-compounds containing a variety of sensitive functional groups including aldehydes, esters, cyano, and nitrine were reduced to their corresponding amines in good to excellent yields with no byproduct.

Discerning the Role of Ag-O-Al Entities on Ag/gamma-Al2O3 Surface in NOx Selective Reduction by Ethanol

Abstract: Alumina-supported silver catalysts (Ag/Al2O3) derived from AlOOH, Al(OH)(3), and Al2O3 were investigated for the selective catalytic reduction of NOx by ethanol. In order to discern the role of support Al skeleton in anchoring silver species and reducing NOx, the series of alumina-supported silver catalysts calcined at different temperatures was characterized by means of in situ DRIFTS, XPS, UVvis DRS, XRD, BET, and NMR. It was found that the NOx reduction efficiency order as affected by alumina precursors could be generally described as AlOOH > Al2O3 >> Al(OH)(3), with the optimum calcination temperature of 600 degrees C. XPS and UV-vis results indicated that silver ions predominated on the Ag/Al2O3 surface. Solid state NMR suggested that the silver ions might be anchored on Al tetrahedral and octahedral sites, forming Ag-O-Al-tetra and Ag-O-A(locta) entities. With the aid of NMR and DFT calculation, A(locta) was found to be the energetically favorable site to support silver ions. However, DFT calculation indicated that the Ag-O-Al-tetra entity can significantly adsorb and activate vital -NCO species rather than the Ag-O-Al-octa entity. A strongly positive correlation between the amount of Al-tetra structures and N-2 production rate confirms the crucial role of Al-tetra in NOx reduction by ethanol.

Sn-MFI as active, sulphur and water tolerant catalysts for selective reduction of NOx

Abstract: Sn-MFI catalysts with Si/Sn molar ratios from 33 to 133 were synthesized for NOx selective reduction by propane. SEM images of the samples showed that they consist of neat and uniform particles with different morphologies by varying the Si/Sn ratios. XRD, N2 adsorption–desorption, DRUV-vis, FTIR and XPS analysis confirmed that the samples were of an MFI structure if the Si/Sn ratio is above 20, in which Sn was incorporated into the MFI framework. As a consequence, a large amount of Lewis acidic sites, mesopores and active surface oxygen species have been formed. The mesopores could facilitate the diffusion of the reactants and products, and the Lewis acidic sites are favourable for the formation of active NOx adsorbates. Therefore, compared with the whole silica Si-MFI (Silicalite-1), all of the Sn-MFI catalysts with an MFI structure show much improved NOx-SCR activity. Furthermore, Sn-MFI catalysts display potent resistance to both sulphur and water vapour deactivation, which makes them potential catalysts for real exhaust control.

Catalyst for ammonia selective reduction of nitrogen oxide and preparation method of catalyst

Abstract: The invention relates to a compound oxide catalyst for ammonia selective reduction of nitrogen oxide and a preparation method of the compound oxide catalyst. The catalyst is mainly applied to purification of nitrogen oxide in flue gas of factories and tail gas of motor vehicles. According to the catalyst, ferric oxide is used as an active ingredient, and rare-earth oxide and other transition metal oxides with different contents are used as co-catalysts. The catalyst is characterized in that the catalyst has a very wide temperature window for the reaction of ammonia selective reduction of nitrogen oxide, can be used for realizing over 80 percent NO removal rate in the temperature range of 100-550 DEG C, has strong water resistance and sulfur poisoning resistance, and can be regenerated to recover performance by means of simply rinsing after being poisoned by sulfur dioxide. The catalyst has a simple preparation method and low cost, and has a good application prospect in purification of nitrogen oxide in flue gas of factories and tail gas of motor vehicles.

Hydrocarbon adsorption and NOx-SCR on (Cs,Co)mordenite

Abstract: (Cs,Co)Mordenite catalysts with 2.9 wt.% of Co and either 2 or 7 wt.% of Cs are active for the selective reduction of NOx with butane and toluene as reducing agents and, at the same time, they can act as hydrocarbon traps at the cold-start conditions of an engine. The presence of cesium does not decrease the catalytic activity of cobalt in the two reducing agents. When butane is the hydrocarbon, cesium increases the temperature window for NOx reduction. The sulfur poisoning of the Cs2CoM catalyst for the selective catalytic selective of NOx with butane is investigated. The catalyst has medium sulfur tolerance and a lower tolerance to hydrothermal treatment. However, this catalyst showed a better performance against poisons compared with that of the CoM catalyst. CoM has almost null adsorption capacity. The incorporation of a low amount of cesium (2 wt.%) notably enhances the adsorption properties and the toluene retention at temperatures higher than 100 °C. Probably, the presence of cesium increases the density charge of oxygen, so that it interacts more strongly with the C H groups. In the samples studied, the adsorption capacity (μmoles m−2) follows the order Cs2CoM ∼ Cs7CoM > NaM > CoM in both hydrocarbons. However, the desorption of butane occurs at temperatures significantly lower than that of toluene. This is related to the interaction of the C H bonds (σ) that gives place to the interaction of butane with the zeolite structure through the hydrogen bridge bond (C H⋯O). Additionally, in the case of toluene, the electronic interactions with the aromatic ring are very important. When NOx diluted in He is passed over the different catalysts with toluene adsorbed, the formation of isocyanate species takes place only when Co is present. These experiments also show that the hydrocarbon adsorption and the NOx reduction may take place simultaneously over the Cs and Co sites, respectively.

Efficient and selective electro-reduction of nitrobenzene by the nano-structured Cu catalyst prepared by an electrodeposited method via tuning applied voltage

Abstract: Pollution caused by toxic nitrobenzene has been a widespread environmental concern. Selective reduction of nitrobenzene to aniline is beneficial to further efficient and cost-effective biologic treatment. Electrochemical reduction is a promising method and Cu-based catalysts have been found to be an efficient cathode material for this purpose. In this work, Cu catalysts with different morphologies were fabricated on Ti plate using a facile electrodepositon method via tuning the applied voltage. The dendritic nano-structured Cu catalysts obtained at high applied voltages exhibited an excellent efficiency and selectivity toward the reduction of nitrobenzene to aniline. Effects of the working potential and initial nitrobenzene concentration on the selective reduction of nitrobenzene to aniline using the Cu/Ti electrode were investigated. A high rate constant of 0.0251 min–1 and 97.1% aniline selectivity were achieved. The fabricated nano-structured Cu catalysts also exhibited good stability. This work provides a facile way to prepare highly efficient, cost-effective, and stable nano-structured electrocatalysts for pollutant reduction.

Electrocatalysts for the Selective Reduction of Carbon Dioxide to Useful Products.

Abstract: The electrochemical reduction of carbon dioxide (CO(2)) to hydrocarbons and alcohols holds great promise as a sustainable and green method to produce valuable carbon fuels. In this work, we review the catalysts used in the selective reduction of CO(2) to formate, carbon monoxide, methane and ethylene.

Reduction of a garnieritic laterite ore by CO-CO2 gas mixtures

Abstract: In extraction of nickel from laterite ores, nickel has to be reduced to metallic form in pyrometallurgical processes. This paper studied the reduction of a garnieritic laterite ore in order to establish the extents and rates of reduction of nickel, cobalt and iron oxides under different conditions, reduction mechanisms, and the optimum conditions for selective reduction of nickel and cobalt oxides over iron oxides. The reduction of the garnieritic ore was examined at 700900°C in the CO-CO2 gas mixtures containing 20-70 vol% CO; the gas flow rate was varied in the range of 350-1050 mL/min. A ferronickel alloy was formed by reduction of the metal oxides in the ore. The extent of reduction of nickel oxide increased with increasing temperature to 740 °C and then decreased with further increasing temperature. The extents of reduction of cobalt and iron decreased slightly with increase in temperature. Increase in CO concentration also promoted reduction of the metal oxides. When CO content was lower than 60 vol%, the extent of reduction of iron oxides was below 20%. Increase in CO concentration to 70 vol% sharply increased iron metallisation (>50%). Gas flowrate above 350 mL/min had a negligible effect on the ore reduction. The effect of ore size on the reduction of the metal oxides was insignificant. The optimal conditions for selective reduction of the laterite ore included temperature 740 °Cand 60 vol% CO in the CO-CO2 gas mixture.

A method for preparing electrocatalyst for carbon dioxide selective reduction

Abstract: The present invention relates to a method for producing an electrocatalyst for the selective reduction of carbon dioxide, comprising the steps of: (A) dissolving a metal precursor in an organic solvent and then subjecting the metal precursor to a first heat treatment to prepare a metal precursor solution; (B) dispersing the carbon support in a mixed solution of a fixing agent and an organic solvent by ultrasonic to prepare a carbon support solution; (C) adding the carbon support solution to the metal precursor solution and performing the second heat treatment for 1 to 3 hours, thereby improving the ferrode efficiency and lowering the over-potential in the selective reduction from CO 2 to CO.

Selective Reduction of No By C3 and C8 Alkanes Over Silver Catalysts on Structured Al2O3/Cordierite Supports

Abstract: An extremal dependence of the catalytic activity of Ag/Al2O3/cordierite on the silver content in the selective catalytic reduction of NO with propane and octane was discovered. The optimum content of Ag was higher during reduction with octane (0.5 wt.%) than with propane (0.3 wt.%). The role of the silver involves formation not only of oxidation–reduction centers but also of additional Lewis acid centers at which activation of the reagents (NO and C n H m ) occurs.

A Comparative Study of M/ZSM-5 (M = Pd, Ag, Cu, Ni) Catalysts in the Selective Reduction of Nitrogen (II) Oxide by Ammonia

Abstract: The improvement of H-ZSM-5 catalyst for NO removal from stack of nitric acid unit was studied in this research. Selective catalytic reduction of NO was investigated on Pd, Ag, Cu and Ni impregnated on ZSM-5 in the presence of excess of oxygen. The new prepared catalysts were characterized by XRD, FTIR, H2-TPR and N2 adsorptiondesorption methods. Successively, NO conversion increased with the reaction temperature transmission through a maximum, and then decreased at higher temperatures, because of the combustion of the ammonia on Pd/ ZSM-5and Cu/ ZSM-5 catalysts. The apparent activation energies in NO removal reaction have been determined for the prepared catalysts and it changes from 23 to 48 kJ/mol. In synthesis catalysts, partial dealumination were confirmed by XRD results. The results exhibited that the Cu/ZSM-5 and Pd/ZSM-5 catalysts had acceptable activity between 200 to 400 °C and under 250°C, respectively. It is found that the NOx removal efficiency does not obey from the same pattern by rising temperature in all of these catalysts.

Deterioration detection device for selective reduction type catalyst

Abstract: PROBLEM TO BE SOLVED: To provide a deterioration detection device for an SCR (Selective Catalytic Reduction)catalyst which is arranged in an exhaust passage downstream of an NSR (NOx Storage Reduction) catalyst, for accurately detecting the deteriorating condition of the SCR catalyst.SOLUTION: The deterioration detection device for the SCR catalyst diagnoses the deterioration of a selective reduction type catalyst under circumstances in which the ammonia adsorption amount of the SCR catalyst is greater than the amount of ammonia which the SCR catalyst in an abnormal condition can absorb, using an integrated value for a NOinflow amount and an integrated value for a NOoutflow amount as parameters when an integrated value for a NOamount flowing into the SCR catalyst reaches a reference NOamount. In this configuration, the deterioration diagnosis of the selective reduction type catalyst is performed under conditions that a difference between the NOeliminating performance of the selective reduction type catalyst in a normal condition and the NOeliminating performance of the selective reduction type catalyst in the abnormal condition is greater, so that the abnormality of the selective reduction type catalyst can be more accurately detected.

Development and Evaluation of a Borohydride- palladium System for Selective Reduction of the C=C Bond of α,β-unsaturated Carbonyl Compounds

Abstract: Selective reduction of the carbon-carbon double bond of α,β-unsaturated carbonyl compounds is most commonly and reliably effected using a palladium metal catalyst together with molecular hydrogen from a pressurized tank. Sodium borohydride, like other hydrides, is ordinarily associated with reduction of the more polarized carbonyl of such compounds. However, we have developed an alternative means of employing sodium borohydride in combination with palladium metal to selectively reduce the carbon-carbon double bonds of these compounds. In this survey study, we introduce sodium borohydride as an alternative hydrogen source for such selective, palladium-catalyzed reductions. We also compare the results of this new, heterogeneous borohydride-palladium method with that of traditional palladium-catalyzed hydrogenation. A third method using only sodium borohydride with no palladium is included for comparison.

Porous ceramics-supported palladium catalyst

Abstract: PROBLEM TO BE SOLVED: To provide a new reduction catalyst that can selectively reduce only a specific functional group, and a selective reduction method using the reduction catalyst.SOLUTION: The present invention relates to: (i) a reduction catalyst comprising a ceramics-supported palladium, where the ceramics comprises silicon oxide, aluminum oxide and calcium oxide, and the sum of these compounds is 85 to 100 wt.%; and (ii) a selective reduction method for a functional group, selected from an alkynylene group, alkenylene group, alkynyl group, alkenyl group, azide group, nitro group, carbobenzoxy group as a protecting group for an amino group, aromatic aldehyde group, and trialkylsilyloxy group, by bringing a compound having at least one of the above groups into contact with a hydrogen source in the presence of the reduction catalyst of the present invention.

Selective method for reduction of Oximes to amines in the presence of Cu nanoparticle

Abstract: The selective reduction of oximes with sodium borohydride (NaBH4) in the presence of nano Cu and charcoal was investigated. Cu nanoparticles are widely used as catalysts; efficacious catalyst: copper and copper alloy nanometer feature high efficacy and selectivity, and can be used as catalyst in some reactions. We have shown that NaBH4 in the presence of charcoal is an efficient protocol for the reduction of oximes. Reduction reactions were carried out in EtOH (5 mL) as solvent under reflux condition at 70–80oC. The product amines were obtained in high to excellent yields. The stereo-chemistry of the reduction by using nano Cu is distinctively different from the other methods.

NOx SELECTIVE REDUCTION CATALYST, METHOD FOR PRODUCING THE SAME AND NOx PURIFICATION METHOD USING THE SAME

Abstract: PROBLEM TO BE SOLVED: To provide an NOx selective reduction catalyst capable of exhibiting high NOx purification activity at high temperature conditions above 400°CSOLUTION: There is provided an NOx selective reduction catalyst which is used in reducing a nitrogen oxide (NOx) with a reducing agent and comprises zeolite containing an aluminum (Al) atom, a phosphorus (P) atom and a silicon (Si) atom in the sketon structure, copper (Cu) carried inside and outside of fine pores of the zeolite and at least one added metal (N) selected from the group consisting of nickel (Ni), cobalt (Co), stannum (Sn) and titanium (Ti), where the content of the copper relative to the amount of the silicon atom contained in the zeolite is 01 to 08 at a Cu/Si molar ratio and the content of the added metal (N) relative to the amount of the copper is 005 to 3 at a M/Cu ratio

Exhaust purification system, exhaust purification method, selective reduction type nox catalyst using the same and production method of the catalyst

Abstract: PROBLEM TO BE SOLVED: To provide an SCR catalyst where NOx purification performance under a comparatively high temperature environment is improved.SOLUTION: A selective reduction type NOx catalyst disposed at the downstream of an exhaust purification catalyst where ammonia is generated in the case that an air-fuel ratio in an exhaust is lower than a theoretical air-fuel ratio performs the selective reduction of NOx by using ammonia generated by the exhaust purification catalyst as a reducing agent. The selective reduction type NOx catalyst includes zeolite supported with Cu and the zeolite contains at least Si, Al and P in a skeletal structure. X and Y satisfies a specific condition when: the supported quantity (in terms of Cu, wt.%) of Cu in the zeolite supported with Cu is X; and the content Si/(Si+Al+P) (mol%) of Si in the zeolite is Y.

Catalyst for exhaust purification

Abstract: PROBLEM TO BE SOLVED: To provide an excellent NOx selective reduction catalyst.SOLUTION: An NOx selective reduction catalyst comprises a complex oxide of Ti, Ce, W, and P or S.SELECTED DRAWING: Figure 2

Regiospecific Reduction of the C=N Bond in 5,6-Dialkyl-2-chloropyridine-3,4-dicarbonitriles.

Abstract: Dihydropyridines are an important group of heterocyclic compounds and they can show different forms of biological activity [1], e.g., antihypertensive [2], antiarrhythmic [3], bioprotective [4], and hepatoprotective [5]. Amongst this group, 1,2(1,6)-dihydropyridines are very poorly represented, that is linked to the small number of methods for preparing them. With the aim of developing novel methods for the synthesis of 1,2(1,6)-dihydropyridines we have studied the reduction process of polyfunctional 5,6-dialkyl-2-chloropyridine-3,4-dicarbonitriles 1. These compounds were prepared according to a three-component method developed by us from tetracyanoethylene, ketones, and concentrated hydrochloric acid [6]. A special feature of the pyridines 1 is the presence of several reactive centers which can undergo a reduction, viz. two cyano groups, the C–Cl bond, and the pyridine ring. This fact complicates the problem of a targeted reduction of the C=N bond in the pyridine ring. It should be noted that, up to the time of our study, the literature has reported reduction processes of structural analogs of pyridines 1, viz compounds containing a 2-halopyridine-3-carbonitrile fragment including other heterocycles in composition. Hence there has been reported a selective reduction of a C–Cl bond by hydrogenolysis in the presence of Pd/C [7], by the action of zinc dust in acidic medium [8], and by the action of a solution of hydriodic acid, iodine, and red phosphorus [9]. In the hydrogenolysis of 2,6-dibromopyridine3,5-dicarbonitrile in the presence of Pd/CaCO3 a simultaneous reduction of the C–Br and C=N bonds of the pyridine ring occurs [10]. The process of reduction of pyrido[2,3-d]pyrimidines has also been reported using NaBH4 in which the pyridine ring was reduced with retention of the halogen to yield 1,4-dihydropyridine derivatives [11]. A selective reduction of the cyano group to an aminomethyl has been reported for 2-chloropyridine-3-carbo-nitrile reaction with NaBH4 in the presence of CoCl2 or with hydrogen using Raney nickel [12]. We have developed a method for the selective reduction of the C(6)=N bond in the pyridines 1a-d which is achieved via their reaction with sodium borohydride in methanol at 20oC for 30 min. The result of this reaction is the formation of the 5,6-dialkyl-2-chloro-1,6-dihydropyridine-3,4-dicarbonitriles 2a-d in 74-91% yields. _______ *To whom correspondence should be addressed, e-mail: oleg.ershov@mail.ru.