Catalytic Properties Of Cu Research Articles

Effects of B Addition on Microstructure Evolution and Efficient Hydrogen Evolution of Self‐Supported Cu–Fe–P Immiscible Alloy

Herein, the effect of B elements on the microstructure and catalytic properties of Cu–31.5Fe–4.5P immiscible alloy is systematically investigated. After microstructure characterizations, it is found that B elements are mainly concentrated in FexP (Fe2P, Fe3P) particles, which affect the Marangoni motion of the particles. With the concentration of B content increasing to 0.75%, the diameter size of the second‐phase particles in the alloys is first refined and then coarsened, in which the alloy with B content of 0.25% has the finest particle size and the proportion of second‐phase particles with sizes ranging from 1 to 10 μm reaches 97%. The electrochemical characterization of dealloyed specimens shows that the overpotential of Cu–Fe–P alloys containing 0.25% B reaches 193 mV at a current density of 10 mA cm−2 in 0.5 m H2SO4 solution. The excellent catalytic performance might be attributed to the increase in the obviously specific surface area of Fe2P and Fe3P particles and the significant increase in the electron transfer.

Effect of Copper Particle Size on the Surface Structure and Catalytic Activity of Cu–CeO2 Nanocomposites Prepared by Mechanochemical Synthesis in the Preferential CO Oxidation in a H2-Rich Stream (CO-PROX)

An effect of Cu powder dispersion and morphology on the surface structure and the physical–chemical and catalytic properties of Cu–CeO2 catalysts prepared by mechanochemical synthesis was studied in the preferential CO oxidation in a H2-rich stream (CO-PROX). Two catalysts, produced by 30 min ball-milling from CeO2 and 8 mass% of copper powders and with particle sizes of several tens (dendrite-like Cu) and 50–200 nm (spherical Cu obtained with levitation-jet method), respectively, were characterized by X-ray diffraction and electron microscopy methods, a temperature-programmed reduction with CO and H2, and with Fourier-transform infrared spectroscopy. The catalyst synthesized from the “large-scale” dendrite-like Cu powder, whose surface consisted of CuxO (Cu+) agglomerates located directly on the surface of facetted CeO2 crystals with a CeO2(111) and CeO2(100) crystal planes exposition, was approximately two times less active at 120–160 °C than the catalyst synthesized from the fine Cu powder, whose surface consisted of CuxO (Cu2+) clusters of 4–6 nm in size located on the steps of facetted CeO2 nanocrystals. Although a large part of CO2 reacted with a ceria surface to give carbonate-like species, no blockage of CO-activating centers was observed due to the surface architecture. The surface structure formed by the use of highly dispersed Cu powder is found to be a key factor responsible for the catalytic activity.

Structures and catalytic properties of Cu(II) complex with chelating fluorinated ligands

Structure of Cu(II) complex with chelating fluorinated ligands were studied at 298 K and 90 K using CW X-band electron paramagnetic resonance (EPR) spectroscopy and density functional theory (DFT). Spin-Hamiltonian and structural parameters have been determined and the latter were compared with the X-ray data showing good similarity. A phase transition occurred at 360 K in solid crystalline sample was observed by EPR and discussed. Qualitative kinetic analysis of the catalytic behavior of Cu(II) complex upon H2O2 decomposition in acetonitrile-aqueous solutions at 313 K was studied using EPR and UV–visible spectroscopy.

Obtaining Methanol from CO2 on Cu–Zn/Al2O3 and Cu–Zn/SiO2 Catalysts: Effect of the Support and Conditions of the Reaction

A study is performed of the catalytic properties of Cu–Zn catalysts on Al2O3 and SiO2 supports (Acros) in the reaction of CO2 hydrogenation to obtain methanol. A sample of 30Cu15Zn/Al2O3 displays great selectivity toward methanol. A sample of 30Cu15Zn/SiO2 has the highest methanol performance. The methanol performance of a sample of 10Cu5Zn/Al2O3 is doubled when the pressure is raised from 10 to 30 atm, and a 94% increase in selectivity is observed. A sample of catalyst 10Cu5Zn/SiO2 does not lose its activity after 10 h of a catalytic reaction, and its methanol performance grows with repeated use

Obtaining Methanol from CO2 on Cu–Zn/Al2O3 and Cu–Zn/SiO2 Catalysts: Effect of the Support and Conditions of the Reaction

A study is performed of the catalytic properties of Cu–Zn catalysts on Al2O3 and SiO2 supports (Acros) in the reaction of CO2 hydrogenation to obtain methanol. A sample of 30Cu15Zn/Al2O3 displays great selectivity toward methanol. A sample of 30Cu15Zn/SiO2 has the highest methanol performance. The methanol performance of a sample of 10Cu5Zn/Al2O3 is doubled when the pressure is raised from 10 to 30 atm, and a 94% increase in selectivity is observed. A sample of catalyst 10Cu5Zn/SiO2 does not lose its activity after 10 h of a catalytic reaction, and its methanol performance grows with repeated use.

Selective hydrogenation reactions of 5-hydroxymethylfurfural over Cu and Ni catalysts in water: Effect of Cu and Ni combination and the reagent purity

This work studies the catalytic properties of Cu and Ni catalysts, as well as the effect of Cu and Ni combination on the activity and selectivity during the aqueous phase hydrogenation of 5-hydroxymethylfurfural (HMF) in a batch reactor, at 60 °C under 30 bar H2. Catalysts with different Ni/Cu ratios (10 wt%) were synthesized over a high surface area graphite (HSAG). While Ni provides the bimetallic catalyst the capacity for hydrogenation of CO and CC groups, Cu contributes to suppress the hydrogenation of the furan ring, reaching a 99% of selectivity to the partial hydrogenated product, 2,5-di-hydroxymethylfuran (DHMF), over 5Cu5Ni/HSAG. The increase of reaction temperature (180 °C) conduced to the hydrolytic ring-opening and rearrangement of HMF. Under such reaction conditions, monometallic Ni afforded the highest yield towards the hydrogenative rearrangement product, 3-hydroxymethylcyclopentanone (81%). However, Cu and CuNi bimetallic catalysts were less reactive to the ring-rearrangement reaction and showed higher tendency to deactivation, especially when the HMF supplier contain sulfur impurities.

The effects of near-surface atomic order on the catalytic properties of Cu3Au and CuAu3 intermetallics for the CO2 reduction reaction

Density functional theory (DFT) calculations combined with cluster expansions (CE) were employed to explore the catalytic activity of stoichiometric and non-stoichiometric Cu3Au and CuAu3 surfaces for CO2 reduction to CO.

Catalytic synthesis of isoprenol from fatty acid ester over bimetallic Cu–Fe catalysts

Supported bimetallic Cu–Fe catalysts revealed high activity and selectivity in isoprenyl acetate hydrogenation to isoprenol under mild reaction conditions (2 MPa H2 and 170 °C). The nature of the carrier has a significant impact on the catalytic properties of Cu–Fe catalysts. The best catalytic properties were found for the 5% Cu–5% Fe/Al2O3 bimetallic catalyst, which provides a 98% isoprenyl acetate conversion in 4 h with the isoprenol selectivity of 82%.

Hydrogen‐Free Hydrogenation of a Nitrogen‐Containing Ring of Quinolines in an Alcoholic Suspension of a Titanium(IV) Oxide Photocatalyst Modified with Metal Cocatalysts

AbstractTiO2 photocatalysts having various metal cocatalysts were prepared and used for photocatalytic hydrogenation of quinoline in 2‐propanol suspensions, in which 2‐propanol acted as the hydrogen source in addition to the solvent. Hydrogenation over cocatalyst‐loaded TiO2 competed with H2 evolution by the self‐coupling of active hydrogen species over the cocatalyst, and the use of TiO2 with a Rh cocatalyst resulted in a large 1,2,3,4‐tetrahydroquinoline (THQn) yield and a much larger H2 yield. In contrast, the use of TiO2 with an inexpensive Cu cocatalyst resulted in a relatively large THQn yield with greatly suppressed evolution of H2, and the hydrogenation was greatly accelerated at slightly elevated temperatures with the rate being almost the same as that with Rh−TiO2 at the same temperature. Based on the results of a kinetic study, the catalytic properties of Cu−TiO2 and Rh−TiO2 are discussed. Hydrogenation over Cu−TiO2 under solar light was investigated in addition to the expandability and reusability of Cu−TiO2.

How the Way a Naphthalimide Unit is Implemented Affects the Photophysical and -catalytic Properties of Cu(I) Photosensitizers.

Driven by the great potential of solar energy conversion this study comprises the evaluation and comparison of two different design approaches for the improvement of copper based photosensitizers. In particular, the distinction between the effects of a covalently linked and a directly fused naphthalimide unit was assessed. For this purpose, the two heteroleptic Cu(I) complexes CuNIphen (NIphen = 5-(1,8-naphthalimide)-1,10-phenanthroline) and Cubiipo (biipo = 16H-benzo-[4′,5′]-isoquinolino-[2′,1′,:1,2]-imidazo-[4,5-f]-[1,10]-phenanthroline-16-one) were prepared and compared with the novel unsubstituted reference compound Cuphen (phen = 1,10-phenanthroline). Beside a comprehensive structural characterization, including two-dimensional nuclear magnetic resonance spectroscopy and X-ray analysis, a combination of electrochemistry, steady-state and time-resolved spectroscopy was used to determine the electrochemical and photophysical properties in detail. The nature of the excited states was further examined by (time-dependent) density functional theory (TD-DFT) calculations. It was found that CuNIphen exhibits a greatly enhanced absorption in the visible and a strong dependency of the excited state lifetimes on the chosen solvent. For example, the lifetime of CuNIphen extends from 0.37 µs in CH2Cl2 to 19.24 µs in MeCN, while it decreases from 128.39 to 2.6 µs in Cubiipo. Furthermore, CuNIphen has an exceptional photostability, allowing for an efficient and repetitive production of singlet oxygen with quantum yields of about 32%.

Anion effect on the cumene hydroperoxide decomposition in the presence of Cu(II) 1,10-phenanthrolinates

Kinetics of the cumene hydroperoxide catalytic decomposition in the presence of Cu(II) salt complexes with 1,10-phenanthroline (Phen) has been investigated in the water: ethanol (1:1) solvent mixture. Catalytic properties of Cu(CH3COO)2 - Phen complex were confirmed: after full hydroperoxide conversion its new portion had been added to the reaction mixture. The hydroperoxide decomposition rate constant observed on the second cycle was the same. The salt anion effect on the complex catalytic activity has been revealed. The rate constant of the cumene hydroperoxide catalytic decomposition increases in the following row of anions: SO42− < Cl− < CH3COO−, the hydroperoxide decomposition in the presence of Cu(II) nitrate in the same experimental conditions was not observed. The effect of the anion nature in the reaction of cumene hydroperoxide catalytic decomposition may be associated with both the structure of the Cu(II) complex with Phen, as well as the structure of the hydroperoxide - catalyst complex. In addition, the double activation effect is observed in the reaction considered. The hydroperoxide molecule is chemically activated by the corresponded Cu(ІІ) salt. The Cu(ІІ) salt reactivity by-turn is activated in the presence of 1,10-phenanthroline and can be regulated by means of variation in corresponded salt anion.

Study on the Controlled Preparation, Analysis and Catalytic Properties of Cu&lt;sub&gt;2&lt;/sub&gt;O Crystals

Study on the Controlled Preparation, Analysis and Catalytic Properties of Cu&lt;sub&gt;2&lt;/sub&gt;O Crystals

The catalytic properties of Cu modified attapulgite in NH3–SCO and NH3–SCR reactions

The cheap and readily available attapulgite (ATP) was doped with different Cu content by using an improved wet impregnation method and their NH3 oxidation and NOx reduction properties were analyzed at 150–500 °C. Results suggested that all these Cu-ATP catalysts possessed superior NH3 oxidation activity, which was further promoted in the presence of NO. However, higher Cu loading led to lower N2 selectivity and NO conversion at high temperatures. 1%Cu-ATP catalyst exhibited good performance in both selective catalytic oxidation of NH3 (NH3-SCO) and selective catalytic reduction of NO by NH3 (NH3-SCR) at 350 °C. And it showed relatively good SO2 and H2O tolerance in the presence of NO. Characterization results proved that Cu2+ ion increased the strong acid sites and redox properties of 1%Cu-ATP, and should be responsible for the outstanding NH3-SCO and NH3-SCR activity. While CuO species, which introduced abundant moderate acid sites and significantly improved redox capability, enriched on the catalysts as the copper loading increased. It dramatically promoted NH3 oxidation and inhibited NO conversion and N2 formation. Therefore, 1%Cu-ATP was more suitable to simultaneously remove slip ammonia and residual NOx in the flue gas, which would facilitate the efficient operation of SCR system and reduce the maintenance costs.

Thermodynamic and catalytic properties of Cu- and Pd- oxides over mixed γ–χ–Al2O3 for methanol dehydration toward dimethyl ether

The development of catalytic systems to generate alternative energies capable of replacing diesel is a great challenge. Methanol dehydration (2CH3OH → CH3OCH3 + H2O) is one of the most suitable catalytic reactions to produce dimethyl ether (DME). In DME synthesis, CuO/γ–Al2O3 based-materials showed to be catalytically active at high pressures, but these lack high performance under atmospheric conditions. In this work, we synthesized CuO/γ–χ–Al2O3, PdO/γ–χ–Al2O3, and CuOPdO/γ–χ–Al2O3 by a facile impregnation method for methanol dehydration at atmospheric pressure. Catalytic results showed that the CuOPdO/γ–χ–Al2O3 sample performed the highest activity. All catalysts reached selectivity of 100% toward DME, regardless of the reaction temperature. Remarkably, the bimetallic catalyst containing low loadings of copper and palladium retained stability during 48 h of reaction at 275 °C, and after its regeneration they showed a similar trend. The activation energies (Ea) for the methanol dehydration using the catalyst that performed the highest catalytic activity CuOPdO/γ–χ–Al2O3 compared with the material with the lowest catalytic activity γ–χ–Al2O3 were obtained. The activation energy values of the γ–χ–Al2O3 and CuOPdO/γ–χ–Al2O3 catalysts were 112.57 kJ/mol and 45.73 kJ/mol, respectively.

Kinetic studies of the impact of thiocyanate moiety on the catalytic properties of Cu(II) and Fe(III) complexes of a new Mannich base

Four new metal complexes of a novel Mannich base 5-methyl-2-((4-(pyridin-2-yl)piperazin-1-yl)methyl)phenol (HL) have been prepared. The compounds were characterized by an array of analytical and spectroscopic methods including Nuclear Magnetic Resonance, Infra-red and UV–Visible spectroscopy. Compounds 1–4 behaved as effective catalysts towards the oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) to its corresponding quinone in the presence of molecular oxygen in DMF solution while compound 4 proved to be the best catalyst with a turnover rate of 17.93 ± 1.10 h−1 as other complexes showed lower rates of oxidation. Also with the exception of dinuclear iron complex (4); thiocyanate containing Cu(II) complex exhibited lower catecholase activity compared to the Cu(II) complex without it.

Catalytic properties of Cu–Mg–Al hydrotalcites, their oxides and reduced phases for ethanol dehydrogenation

Different phases of Cu–Mg–Al compounds, hydrotalcites, their oxides, and reduced phases were prepared by co-precipitation and evaluated using the ethanol reactions. The solids were characterized by surface area measurements, X-ray diffraction (XRD), thermogravimetry coupled with differential thermal analysis, H2-temperature-programmed reduction, CO2 temperature-programmed desorption and temperature-programmed oxidation. The catalytic runs were performed at temperatures ranging from 250 to 350 °C. Activation with H2 was previously carried out in situ at 300 °C for the reduced samples. The samples with higher amount of Cu presented high ethanol conversion independent of the phase evaluated. The characterization by XRD after the reaction revealed that all samples exhibited only the metallic phase of Cu, independent of the phase before the reaction. The high selectivity for dehydrogenation was responsible for the transformation of hydrotalcites and mixed oxides into metallic phase during the ethanol reaction. Samples with lower amounts of Cu were deactivated by carbon deposition whereas samples with higher amount of Cu were deactivated mainly by sintering.

Oxidation of CO on the Cu–Co–Fe oxide system applied on carbon nanotubes synthesized on Co2O3

Physicochemical characteristics of carbon nanotubes synthesized on Co2O3 and oxide Cu–Co–Fe catalysts on their base applied in the CO oxidation reaction have been investigated. It is shown that the deposition technology of the active mass, which, according to the X-ray phase analysis, is a mixture of the Cu2(OH)3NO3 and CuO phases, strongly influences the activity of the Cu–Co–Fe/CNT catalysts. The greatest amount of the Cu2(OH)3NO3 phase is observed in the catalysts produced by a single deposition of the active component on carbon nanotubes, which according to the thermodesorption mass spectroscopy, contributes to the formation of active centers with the lower activation energy of the CO2 desorption and the reaction of the CO oxidation proceeds at a considerably lower temperatures. The TEMdata indicate that at the step-by-step deposition of the active mass in the surface layer the formation of the massive agglomerates, which are inhomogeneously located on the disordered structures of nanotubes, and this unfavourably affects the catalytic properties of Cu–Co–Fe/CNT catalysts.

Influence of Mn content on the catalytic properties of Cu-(Mn)-Zn-Mg-Al mixed oxides derived from LDH precursors in the total oxidation of methane

Cu-(Mn)-Zn-Mg-Al mixed oxides with Cu/Zn atomic ratio of 1 and different Mn contents were synthesized by thermal decomposition of layered double hydroxides (LDHs) precursors. They were characterized using X-ray diffraction, textural measurements, EDX, TEM, H2-TPR and XPS techniques, and their catalytic properties in the total oxidation of methane were evaluated. The precursors consisted in nitrate-interlayered multicationic LDH phase with additional Mn3O4 side phase for Mn-containing systems. Their thermal decomposition resulted in complex mixed oxides containing periclase-like, CuO and different spinel (Cu1.5Mn1.5O4, CuMn2O4, and MnAl2O4) phases. XPS analysis confirmed the existence of copper and manganese with different valence states in the Cu,Mn-containing mixed oxides. The catalytic activity expressed as the intrinsic rate of CH4 conversion increased by adding Mn to the CuZnMgAl mixed oxide calcined at 650°C and by increasing its content. The intrinsic activity also strongly increased when the calcination temperature increased from 650 to 800°C. The increased activity was correlated to enhanced catalyst reducibility due to the favorable Cu-Mn interaction. Among the different catalytic active phases, i.e. CuO, Cu1.5Mn1.5O4 and CuMn2O4, the Cu1.5Mn1.5O4 spinel seems to be the most active one.

Effect of synthesis method on physicochemical and catalytic properties of Cu–Zn-based mesoporous nanocatalysts for water-gas shift reaction

Two new mesoporous nanocatalysts based on CuO–ZnO/MgO were synthesized by using a modified liquid-phase method. Due to use of this method, the nanocatalysts contained an efficient ZnO/MgO phase in which MgO is incorporated into ZnO phase. The structural and catalytic properties of the nanocatalysts in the water-gas shift reaction were investigated compared with samples prepared by conventional sol–gel and liquid-phase methods as references, as well as a commercial catalyst. The results reveal that the new nanocatalysts exhibited higher surface area, lower degree of agglomeration, and higher activity than the reference samples, indicating the influence of both the synthesis method and phase composition.

Immobilized copper- and molybdenum-containing ionic liquids in oxidation of sulfides

The synthesis and comparative analysis of catalytic properties of Cu- and Mo-containing ethylpropylimidazolium derivatives immobilized on silica-series mineral supports have been performed. The oxidation of diethyl sulfide and methyl phenyl sulfide with oxygen and hydrogen peroxide in a hydrocarbon medium has been studied as a model process. The catalyst based on ethylpropylimidazolium polymolybdates is the most active and stable in the oxidation of methyl phenyl sulfide.