Catalytic Effect Of Copper Research Articles

Realizing single-layer graphene by simultaneous crystallization and top-down etching of amorphous graphene-like carbon obtained via CVD

Continuous large-area graphene can be obtained on copper by utilizing solid polymer carbon sources (SPCS). However, the detailed conversion process and related mechanisms have been rarely reported. Here, a low-temperature chemical vapor deposition (CVD) combined with high-temperature hydrogen annealing (HTHA) method is designed to investigate the intricate evolution process from SPCS to amorphous graphene-like carbon (AGLC), and subsequently to single-layer graphene (SLG). During low-temperature CVD process, under catalysis of copper and auxiliary catalysis of hydrogen, the pyrolysis products of SPCS undergo nucleation and growth on copper, resulting in the formation of AGLC at 500 °C. During subsequent HTHA process above 1000 °C, the conversion of AGLC to continuous SLG can be achieved through simultaneous catalytic crystallization of copper and top-down etching of hydrogen, which sequentially undergoes coexistence stage of AGLC/few-layer graphene (FLG), followed by FLG formation stage. Under different stage and conditions, there exists a synergistic-competitive relationship between catalytic effect of copper and etching effect of hydrogen. The proposed conversion mechanism can provide fundamental insights into SLG synthesis via SPCS, which could facilitate further advancements in large-scale industrial applications of graphene.

Si3N4 preparation from photovoltaic kerf loss silicon waste by copper collaborative nitriding method

In this work, Si3N4 powders were prepared by collaborative direct nitriding method from photovoltaic kerf loss silicon waste. The catalytic effect of copper (Cu) on the direct nitriding reaction of photovoltaic Si waste and the morphologies of the nitriding products were investigated. The quantitative analysis of XRD results and thermogravimetric results demonstrate that Cu significantly reduces the initial nitriding temperature, and Cu has a positive effect on the nitriding of silicon waste. At 1300 °C, the sample without Cu had almost no nitriding reaction, while the total conversion rate of kerf loss waste Si was 100 %, and the yield of (α+β) Si3N4 was up to 79.2 % with 8 wt% Cu additive. The thermodynamic analysis of the Si-O-N-Cu and nitriding process was carried out by FactSage software. Moreover, the morphologies of the nitride products were observed by SEM. The addition of copper promoted the generation of Si3N4 nanorods, and the number and diameter of α-Si3N4 nanorods increased with the increase in copper content. Three reaction mechanisms of Si nitridation were discussed. This work provides a feasible method to reuse and recycle the kerf lost silicon waste.

Micro-Mechanism Influence of Copper on Thermal Decomposition of Vegetable Oil-Paper Insulation Based on ReaxFF-MD

The ecological environment is increasingly damaged due to the impact of mineral oil extraction and leakage. As a kind of sustainable resource, a vegetable oil transformer has bright application prospects in future. However, the stability of vegetable oil has always been a problem to be solved. In addition, the metallic copper inside the transformer has a certain catalytic effect on the deterioration of vegetable oil. In this article, a copper–oil–paper insulation model is established. Based on the molecular dynamics simulation method, the catalytic mechanism of copper on the deterioration of oil-paper insulation is revealed from the microscopic level. Then, the effects of temperature, contact area, and oxygen on the catalytic effect of copper are discussed. The results show that copper could accelerate the decomposition of oil-paper insulation by attracting H atoms and O atoms in oil-paper. The increase in temperature accelerates the progress of the catalytic reaction and aggravates the deterioration of oil-paper insulation. The oxygen concentration has an important influence on the catalytic reaction of copper. As the oxygen concentration increases, the catalytic effect of copper is weakened. The abovementioned research could provide some theoretical reference for further exploration of effective oil-paper insulation deterioration protection technology.

Catalytic Effect of Copper on Ozonation in Aqueous Solution

ABSTRACT Catalytic effects of cupric ion (Cu2+) and zero-valent copper (Cu0) on ozonation in aqueous solution were discussed in this research using 1,4-dioxane as a radical probe. Ozonation with Cu0 enhanced 1,4-dioxane removal, whereas Cu2+ had no catalytic effect. Two initiation steps were proposed for the catalytic effect of Cu0; the corrosion of Cu0 by oxygen and ozone and a one-electron redox reaction of Cu0 with ozone. The former produced cuprous ion (Cu+) and the latter produced both Cu+ and ozonide ion (O3˙−). Hydroxyl radicals (HO˙) was generated by the reaction of Cu+ with ozone and protonation of O3˙−.

Cu-Catalyzed Hydrodehalogenation of Brominated Aromatic Pollutants in Aqueous Solution

The catalytic effect of copper in Devarda’s Al-Cu-Zn alloy (Dev. alloy) and sole metallic copper, copper salts and copper oxides in the coaction of NaBH4 within the hydrodehalogenation (HDH) of polybrominated phenols, such as the herbicide Bromoxynil in alkaline aqueous solution has been investigated. Namely, the hydrodebromination (HDB) activity of Dev. alloy/NaOH system has been compared to heterogeneous Cu-based catalysts using NaBH4 as a reductant. Differences in the solid-state structures of used Cu-based heterogeneous catalysts after the mentioned HDB process have been studied using the powder XRD and SEM techniques. It was found that some of the used copper-based catalysts are reusable and reasonably effective even at room temperature. Efficiency of the most promising copper-based reduction systems (Dev. alloy/NaOH and Cu-based catalysts/NaBH4) have been successfully tested within the HDB of industrially important brominated flame retardant tetrabromobisphenol A (TBBPA). Dev. alloy/NaOH and Cu-based catalyst generated in-situ within the CuSO4/NaBH4 produced were recognized as the most active HDB agents for complete debromination of both BRX and TBBPA.

Catalytic Effect of Copper on Ozonation in Aqueous Solution

ABSTRACT Catalytic effects of cupric ion (Cu2+) and zero-valent copper (Cu0) on ozonation in aqueous solution were discussed in this research using 1,4-dioxane as a radical probe. Ozonation with Cu0 enhanced 1,4-dioxane removal, whereas Cu2+ had no catalytic effect. Two initiation steps were proposed for the catalytic effect of Cu0; the corrosion of Cu0 by oxygen and ozone and a one-electron redox reaction of Cu0 with ozone. The former produced cuprous ion (Cu+) and the latter produced both Cu+ and ozonide ion (O3˙−). Hydroxyl radicals (HO˙) was generated by the reaction of Cu+ with ozone and protonation of O3˙−.

PROSPECTS FOR THE USE OF ASPERGILLUS NIGER CHITIN-GLUCAN COMPLEX IN THE COMPOSITION OF ELECTRICAL INSULATING TYPES OF PAPER

The paper presents the results of experiments to improve the performance of insulating paper as a component of high-voltage paper-impregnated insulation by introducing the modifying additive into the paper mass. Environmentally safe and economically feasible method of obtaining modifying additives of the chitin-glucan complex of Aspergillus niger (A.n.) which is a large-tonnage waste production of citric acid is proposed. The modifying additive was introduced into the paper mass in an amount of 5–10% to the mass of absolutely dry fiber of sulfate insulating cellulose. The paper samples were subjected to accelerated thermal aging at 140 °C for 250 hours. The values of the short – term electrical strength of the samples with the modifying additive, both in the initial and in the aged state, exceeded the similar characteristic of the paper sample without additives. for the paper made of 100% cellulose after 250 hours of accelerated thermal aging the maximal mechanical tensile strength decreased by 2.1 times; for paper containing 5% HGC A.n. – by 1.5 times and for the insulating paper, which was introduced into 10% of the modifying additive, the specified parameter during the test has not changed. Comparative evaluation of the sorption activity of the cellulose component was carried out by determining the light transmission coefficient of transformer oil relative to the standard at the process of thermal aging. It was found that the modification of insulating paper by biopolymer also increases its sorption activity in relation to the products of destruction of paper-impregnated insulation components under the catalytic effect of copper.

Glyphosate photodegradation: stoichiometry, kinetic and catalytic effects

Photodegradation of glyphosate (PMG) in aqueous solution by the action of UV-light and the catalytic effect of copper and copper-alga Ulva lactuca is described. The photodegradation kinetic reaction of PMG can be explained using a first-order kinetic model, with a mean rate constant of k = (0.04 ± 0.01) h-1 and a mean half-life (τ) = (17 ± 4) h. The quantum yield (φ) obtained for the photochemical decomposition of PMG was (4.8 ± 0.1) 10-4 mol Einstein-1. The resulting photodegradation by-products obtained were acetate, aminomethylphosphonic acid (AMPA), phosphate, sarcosine and to a lesser extent nitrate. The rate of PMG degradation is increased by the presence of copper and Cu-alga Ulva lactuca in the reaction media. The present work represents a new understanding on the photodegradation of the herbicide glyphosate and the results obtained may contribute to the development of new remediation technologies.

Copper catalytic effect on the thermal deterioration and surface morphology performance of transformer oil–paper insulation

Transformer failure caused by copper corrosion in oil–paper insulation has been attracting much attention in recent years. It is necessary to get a better understanding the effect of copper on the degradation rate and the microcosmic performance of the oil–paper insulation. In this way, targeted measures could be taken to prevent harm to the transformer. The catalytic effect of copper on the thermal aging rate and the micro‐/nano‐level morphology of oil–paper insulation aged with and without copper are compared in this paper. The dynamic behavior of copper compounds dissolved in oil and deposited on the insulation paper surface is discussed. Results show that copper plays a catalytic role in the deterioration of oil–paper insulation, and this role becomes obvious in the later stages of aging. Compared to the oil–paper insulation sample aged without copper, in the oil–paper insulation sample aged with copper the oil has higher acidity and higher ultraviolet absorption wavelength. Besides, the degree of polymerization of the paper is lower. Scanning electron microscopy/energy dispersive spectrometry (SEM/EDS) results show that copper is present on the innermost paper surface. SEM and atomic force microscopy clearly show the deposition of copper compounds. Higher deterioration of the paper results in more roughness of the paper surface. The content of copper compounds dissolved in oil was found to be increasing first and then decreasing in the later process of aging. The content of copper compounds deposited on the paper increases significantly when the oil is aged for a long time. The catalytic effect of copper on the thermal aging rate and the surface morphology of oil–paper insulation should be paid more attention even for a noncorrosive oil. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Preparation of Adhesive Carbon Film on Cu Substrate by Electro-Oxidation of C2 − 2 in a LiCl-KCl-CaCl2-CaC2 Melt

Deposition of carbon film on copper substrate with and without electroplating Ni coating by a two-stage potentiostatic electro-oxidation of acetylide anion in a LiCl-KCl-CaCl2-CaC2 melt at 823 K. The results indicated that the carbon deposits obtained on the Ni-coated was continuous and tenacious film due to the high solubility of C in Ni, while that obtained on the bare copper emerged a poor adhesion to the substrate with few carbide or solid solution formation. The cyclic voltammetry for a copper electrode showed that C2 − 2 ions are oxidized more favorably than on graphite electrode, that is due to the active Cu surface can play a catalytic role for oxidation reaction of acetylide ions. However, the catalytic effect of copper will decline when the surface was covered by carbon deposits. By surface modification with electroplating nickel on the Cu substrate, the coarse appearance of Ni coating composed of the small and spherical grains probably helps to the nucleation and growth of carbon film with graphitized and amorphous phases. Meanwhile, the coated Ni interlayer can enhance adhesion of carbon film to copper substrate according to scratch test results and probably protect metallic copper form the anodic dissolution in some extent.

Electrochemical Impedance Spectroscopic Investigation in Detecting 2,4‐dinitrophenylhydrazine Using Catalytic Effect of Copper at Glassy Electrode

AbstractThis paper reports on the use of electrochemical impedance spectroscopy (EIS) allied to copper (II) for the determination of 2,4‐dinitrophenylhydrazine (DNPH) at glassy carbon electrode (GCE). The experiment measurements were carried out in methanol at a potential of 0.3 V versus Ag/AgCl. The Nyquist plots were modeled with a Randle equivalent circuit, by identifying the charge transfer resistance as the relevant concentration dependent parameter. These measurements show that the impedance spectra of DNPH increased by the formation of non‐electroactive compound produced from specific interaction between DNPH and Cu (II), which will block the electron‐transfer process of the redox probe. Therefore, the proposed methodology offers a detection limit of 4.0×10−8 mol L−1. The proposed methodology was satisfactorily applied to determine DNPH in industrial water samples.

Copper(II) catalysis for oxidation of l-tryptophan by hexacyanoferrate(III) in alkaline medium: A kinetic and mechanistic approach

The catalytic effect of copper(II) catalyst on the oxidation of l-tryptophan (Trp) by hexacyanoferrate(III) (HCF), has been investigated spectrophotometrically in an aqueous alkaline medium at a constant ionic strength of 0.5moldm−3 and at 25°C. The stoichiometry for both the uncatalyzed and catalyzed reactions was 1:2 (Trp:HCF). The reactions exhibited first order kinetics with respect to [HCF] and less than unit orders with respect to [Trp] and [OH−]. The catalyzed reaction exhibited fractional-first order kinetics with respect to [CuII]. The reaction rates were found to increase as the ionic strength and dielectric constant of the reaction medium increase. The effect of temperature on the rates of reactions has also been studied, and the activation parameters associated with the rate-determining steps of the reactions have been evaluated and discussed. Addition of the reaction product HCF(II) to the reaction mixture did not affect the rates. Plausible mechanistic schemes for uncatalyzed and catalyzed reactions explaining all of the observed kinetic results have been proposed. In both cases, the final oxidation products are identified as indole-3-acetaldehyde, ammonia, and carbon dioxide. The rate laws associated with the reactions’ mechanisms are derived. The rate constants of the slow steps of the reactions along with the equilibrium constants are also calculated.

Thin-Layer Chromatography of Metal Cations Modified with Amines and Surfactants and the Sorption-Catalytic Detection of Cobalt(II) and Copper(II)

The thin-layer chromatography (TLC) procedures of metal cations, modified with amines and cationic surfactant micelles, followed by the sorption-catalytic detection of cobalt(II) and copper(II) directly into the thin layer were presented. It has been shown that the addition of hexamethylenediamine to the mobile phase acetone—3 M HCl and the impregnation of TLC plates with cetyltrimethylammonium bromide micelles and triethylamine followed by separation in 5% NaCl (pH 2.3) improves the separation efficiency of divalent metal cations mixture. A new highly sensitive detection of copper(II) and cobalt(II) after modified TLC with sorption-catalytic method was proposed. The TLC modifiers enhance the catalytic effect of copper(II) and cobalt(II) in the indicator reactions and detection selectivity. The detection limit was 0.1 ppb for copper(II) and 0.02 ppt for cobalt(II). It should be noted that cobalt(II) does not interfere with the determination of copper( II) in a 200-fold excess. The possibility of using the developed procedures in the analysis of natural water and food was shown.

Kinetics and Mechanistic Approach to the Oxidative Behavior of Biological Anticancer Platinum(IV) Complex toward ‐Asparagine in Acid Medium and the Effect of Copper(II) Catalyst

ABSTRACTThe catalytic effect of copper(II) ions toward the oxidation of ‐asparagine (Asn) by an anticancer platinum(IV) complex in the form of hexachloroplatinate(IV) (HCP) has been investigated in aqueous acid medium at the constant ionic strength and temperature. The progress of both uncatalyzed and copper(II)‐catalyzed oxidation reactions has been monitored spectrophotometrically. The stoichiometry in both cases is [Asn]/[HCP] = 1:1. The kinetics of both redox reactions is first order with respect to [oxidant] and less than the unit order in [acid]. The order with respect to [Asn]T decreases from unity in the uncatalyzed path to less than unity in the catalyzed one. The catalyzed path is first order in [CuII]T. Increasing ionic strength and dielectric constant decreases the oxidation rates. The final oxidation products of ‐asparagine are identified as the corresponding aldehyde (α‐formyl acetamide), ammonium ion, and carbon dioxide. Tentative mechanisms of both reactions have been suggested. The appropriate rate laws are deduced. The activation parameters of the uncatalyzed reaction have been evaluated and discussed.

A study of the effect of copper and additives in hydrocarbon and ester based insulating liquids with isothermal microcalorimetry

An isothermal microcalorimeter has been used to study the effect of solid copper in hexadecane, vegetable oil (ester) and mineral oil. The experiments have shown a catalytic effect of copper in oxidation of hydrocarbons and also the anti-oxidative effect of dibenzyl disulphide when combined with copper addition. The catalytic effect of copper is found in hydrocarbon as base oil and hexadecane, but not in experiments using inhibited oil and ester as the dielectric liquid.

Chemiluminescence determination of dissolved copper(II) in natural waters

The catalytic effect of copper(II) on the chemiluminescence reaction of luminol oxidation in the presence of some modeling organic substances of natural waters, i.e., EDTA and citric and glutamic acids, is studied. A comparison of the data obtained with the calculated profiles of copper distribution among the dissolved forms in model solutions revealed that the binding of copper to citrate does not affects and its binding with the other organic reagents reduces the catalytic effect of copper(II) in the chemiluminescence reaction. Free ions and monohydroxo complexes of copper(II) demonstrate the highest activity in the CL reaction. The chemiluminescence method is applicable to the direct (with no preliminary separation) determination of labile copper species in natural surface waters.

Electrocatalytic Sensing of Nitrate at Cu Nanosheets Electrodeposited on WO<sub>3</sub>/Polyaniline Modified Electrode

A porous copper/tungsten oxide (WO3)/polyaniline (PANI) composite modified electrode CuWP was fabricated by electrochemical deposition of copper nanosheets on WO3/PANI composite. The CuWP exhibited higher electrocatalytic activity for nitrate reduction than the similarly prepared copper modified electrode due to the larger surface area of CuWP and the synergistic catalytic effect of copper and WO3/PANI. The linear scan voltammetry results showed a good linear relationship between nitrate reduction current and concentration of nitrate from 40 to 276 μM, with a sensitivity of 4.5 μA/μM and detection limit (S/N=3) of 1.2 μM. The CuWP modified electrode was tried to be employed in determination of nitrate in drinking water.

Effects of pipe materials, orthophosphate, and flow conditions on chloramine decay and NDMA formation in modified pipe loops

This study examined the effects of pipe materials (iron, copper, lead and PVC) and orthophosphate on chloramine decay and N -nitrosodimethylamine (NDMA) formation under stagnant, laminar and turbulent conditions using modified pipe loops. As expected, chloramine decay rates generally increased with increasing flow velocity. In the presence of orthophosphate, chloramine degradation in the iron loop increased regardless of flow conditions, whereas chloramine decay rates decreased for the copper and lead loops, especially under turbulent conditions. NDMA formation in the copper loop was consistently higher than it was in the PVC control loop under laminar conditions, supporting the theory of a possible catalytic effect of copper on NDMA formation (as reported elsewhere). Iron catalysis of NDMA formation became more prominent in the presence of orthophosphate, but copper catalysis became less significant after the addition of orthophosphate. Only in the copper loop, the released metal concentrations were decreased under laminar conditions compared with turbulent flow, and they were also reduced effectively due to the addition of orthophosphate, suggesting that the catalytic effect was not primarily due to dissolved copper but likely included copper-based solids (corrosion products).

Catalytic effect of copper(II) oxide on oxidation of cellulosic biomass

The reuse and recycling of biomass materials can minimize the environmental impact of society, and can help create a sustainable community. Although cellulosic biomass from demolished buildings is a promising resource for recycling, contaminants, such as wood preservatives that likely contain metal oxides, are found in recycled wood dust. These oxides could act as catalysts for the oxidation of organic materials, resulting in spontaneous ignition of large piles of recycled wood dust. Copper(II) oxide (CuO) is major component in wood preservative and plays a catalytic role in the oxidation of cellulose, which could cause spontaneous ignition. The present study focused on the influence of CuO on oxidation of cellulose. The exothermal behavior and mass loss of cellulose/CuO mixtures were investigated. Changes in exothermal behavior and mass loss with an increasing amount of CuO were measured by differential scanning calorimetry and thermogravimetry. In addition, kinetics and spectroanalysis were conducted to determine the catalytic effect of CuO on oxidation of cellulose and help determine the oxidation model of cellulose upon addition of CuO. Results revealed a change in exothermal behavior and increase in mass loss with increasing amounts of CuO. In addition, CuO had a catalytic effect on the oxidation of cellulose, which helped determine the oxidation model of cellulose upon addition of CuO.

Catalytic effect of Ag + and Cu 2+ on leaching realgar (As 2S 2)

The catalytic effect of Ag + and Cu 2+ on the dissolution of realgar was studied. In the absence of these catalysis ions, little realgar can be leached by Fe 3+ either with or without bacteria. Silver ion can enhance the chemical leaching and bioleaching rate remarkably, while the catalytic effect of copper(II) ion was not so obvious. The catalytic mechanism of Ag + and Cu 2+ was similar: the surface arsenic was replaced by the formation of Ag 2S or CuS, which was then dissolved by Fe 3+. With Ag + added, the influences of concentration of Fe 3+ and temperature on chemical leaching were also investigated.