Catalyst Of Cu Research Articles

Determination of copper(II) in the dairy product by an electrochemical sensor based on click chemistry

Herein, a novel sensitive electrochemical sensor for copper(II) based on Cu(I) catalyzed alkyne–azide cycloaddition reaction (CuAAC) is described. The catalyst of Cu(I) species is derived from electrochemical reduction of Cu(II) through bulk electrolysis (BE) with coulometry technique. The propargyl-functionalized ferrocene (propargyl-functionalized Fc) is covalently coupled onto the electrode surface via CuAAC reaction and forms propargyl-functionalized Fc modified gold electrode, which allows a good and stable electrochemical signal. The change of current at peak ( dI), detected by differential pulse voltammetry (DPV), exhibits a linear response to the logarithm of Cu(II) concentration in the range of 1.0 × 10 −14–1.0 × 10 −9 mol L −1. It is also found that the proposed sensor has a good selectivity for copper(II) assay even in the presence of other common metal ions. Additionally, the proposed method has been applied to determine copper(II) in the dairy product (yoghurt) with satisfactory results.

Dimethyl ether synthesis on the admixed catalysts of Cu-Zn-Al-M (M = Ga, La, Y, Zr) and γ-Al 2O 3: The role of modifier

Dimethyl ether synthesis has been conducted on the admixed catalysts of Cu based catalysts (for methanol synthesis) and γ-Al 2O 3 (for methanol dehydration). The Cu-Zn-Al-M (M = Ga, La, Y, Zr) hydrotalcite-like structures as catalyst precursors for methanol synthesis part of the admixed catalysts are synthesized by the co-precipitation method. The physico-chemical characteristics of the catalysts are analyzed by BET-surface area, XRD, TPR, SEM/EDS, XPS and N 2O pulse chemisorption studies. DME synthesis experiments showed that the CO conversion and DME yield are linearly correlated with Cu metal surface areas of Cu based catalysts admixed with γ-Al 2O 3, indicating that methanol synthesis rate can control the overall DME synthesis rate. The yttrium-modified Cu-Zn-Al admixed catalysts showed the superior activity with a DME yield of 47.7% to other Cu-based catalysts. The reason may be attributed to the increase in Cu metal surface area by the addition of yttrium.

Synthesis of tetrahydrofuran from maleic anhydride on Cu–ZnO–ZrO2/H-Y bifunctional catalysts

Abstract A series of bifunctional Cu–ZnO–ZrO2/H-Y catalysts of different compositions were prepared by coprecipitating sedimentation method and were characterized by surface area and XRD analyses. The catalytic performance in synthesis of tetrahydrofuran was evaluated and optimized in a three-phase slurry batch reactor. The experimental results showed that the appropriate ratio of Cu/ZnO in the hydrogenation catalyst was 50/45, for which the conversion of maleic anhydride (MA) and selectivity of tetrahydrofuran (THF) reached 100% and 46%, respectively, at 50 bar and 493 K after 6 h of operation. Also, according to these results, it was demonstrated that the incorporation of zirconium oxide in the catalyst formulation enhanced the catalytic activity, and tetrahydrofuran selectivity was increased to 55%. Ultimately, it was concluded that the bifunctional catalyst of Cu–ZnO–ZrO2/H-Y was an appropriate catalyst to produce THF from MA with high activity, selectivity and stability.

Catalysts of Cu(II) and Co(II) ions adsorbed in chitosan used in transesterification of soy bean and babassu oils – A new route for biodiesel syntheses

Catalysts of Cu(II) and Co(II) adsorbed in chitosan was used in transesterification of soy bean and babassu oils. The catalysts were characterized by infrared, atomic absorption and TG, and biodiesels was characterized by infrared, NMR, CG, TG, physic chemistry analysis. The maximum adsorption values found for copper and cobalt cations were 1.584 and 1.260mgg−1, respectively, in 180min. However, conversion of oils in biodiesel was better when used Co(II) adsorbed in chitosan.

Dimethyl ether synthesis from syngas over the composite catalysts of Cu–ZnO–Al2O3/Zr-modified zeolites

Abstract The synthesis of dimethyl ether (DME) from a model gas mixture of biomass-derived syngas has been investigated on the composite catalysts, Cu–ZnO–Al 2 O 3 /Zr-modified zeolites (Ferrierite, ZSM-5 and Y). The composite catalysts were synthesized by the coprecipitation of Cu–Zn–Al precursors in the slurry of Zr-modified zeolites. The composite catalyst prepared from Zr–ferrierite showed stable activity and the best DME selectivity. Apart from the easy reducibility of Cu species, the presence of appropriate acid sites of required strength for methanol dehydration is proposed to be the reason for the superior performance of Cu–ZnO–Al 2 O 3 /Zr–Ferrierite catalyst.

A Novel Catalyst of Cu–Bi–V–O Complex in Phenol Hydroxylation with Hydrogen Peroxide

A novel complex oxide of Cu–Bi–V–O was hydrothermally synthesized in a Bi2O3–V2O5–CuO–H2O system, and it was found that this compound is catalytically active for phenol hydroxylation by H2O2, which is comparable to TS-1. Reaction temperature, solvent, the molar ratio of phenol to H2O2, reaction time, catalyst amount, and method of H2O2 addition were found to be major factors for phenol conversion and product selectivity. Furthermore, electron spin resonance (ESR) was used to characterize the reaction intermediates, two species assigned to hydroxyl radicals and hydroperoxyl radicals were observed, and the hydroxyl radicals are proposed to play important roles in the formation of products in catalytic phenol hydroxylation by H2O2.

97/00176 Catalytic effect of Cu(OH) 2 on liquefaction for Taiheiyo coal. (1). Effect of catalyst of Cu(OH) and its related compounds on liquefaction

97/00176 Catalytic effect of Cu(OH) 2 on liquefaction for Taiheiyo coal. (1). Effect of catalyst of Cu(OH) and its related compounds on liquefaction

Higher oxygenate formation from ethanol on Cu/ZnO catalysts: Synergism and reaction mechanism

A remarkable synergism was observed in the higher oxygenate formation from ethanol on Cu/ZnO catalysts compared to one component catalyst of Cu or ZnO. The reaction mechanism was examined by 13C labelling studies and selective feeding methods. A 13C NMR and a GC/MS were used to determine the structure of the labelled products. A mass spectrometer was used to trace the dynamic change of the product distribution. A comprehensive reaction mechanism for the carbon chain growth on Cu/ZnO catalysts was proposed. The synergism could be explained by different intrinsic characteristics of copper and ZnO in the dehydrogenation of ethanol. Nucleophiles are produced preferentially on ZnO and electrophiles are produced preferentially on copper, and they would associate to from dioxygenated C 4 intermediates, which are converted to various higher chain products. A stabilization of ethoxy carbanion on ZnO was suggested, which would participate in the chain growing reaction.

A Microkinetic Analysis of the Water–Gas Shift Reaction under Industrial Conditions

To form the basis for a microkinetic understanding of the low-temperature water–gas shift reaction over Cu-based catalysts as operated industrially, the kinetics have been measured under a wide range of reaction conditions. To elucidate possible support effects the reaction was studied over catalysts of Cu supported on Al2O3, SiO2, or mixed ZnO/Al2O3. The proposed microkinetic model is based on a “surface redox” mechanism deduced from Cu single-crystal studies. All the input data for the elementary steps were taken from available Cu single-crystal studies and the total number of sites was the only free parameter in the microkinetic analysis. It was found to be important especially at high pressure to include in the mechanism the synthesis and hydrogenation of formate. The different dependencies of the overall kinetics have also been evaluated by a power law kinetic model, which was found to give an excellent representation of the kinetic data. It is seen that in spite of the severe constraints placed on the microkinetic model it could account for many of the important kinetic dependencies of the industrial water–gas shift reaction over the different Cu-based catalysts. Furthermore, the deduced number of active sites agrees well with the initial Cu surface area of the reduced catalysts determined separately by H2-TPD suggesting that the model is also satisfactory for describing quantitatively the magnitude of the rates. Thus, a good starting point in interpreting the water–gas shift kinetics is to consider the catalysis occurring solely on the metallic Cu particles in the catalysts. The nature of the support may, however, have important secondary roles. For example, dynamic restructuring of the Cu particles may take place by changing the synthesis conditions and may depend on the nature of the support, as recently evidenced in separate EXAFS experiments.