Dispersion Of Cu Particles Research Articles

Vapor-phase synthesis of 3-methylindole from glycerol and aniline: the effect of Al2O3 promoter and the preparation method on the performance of the Cu–Al2O3/SiO2 catalyst

An Al2O3-modified Cu/SiO2 catalyst was used in the vapor-phase synthesis of 3-methylindole from glycerol and aniline. The effect of Al2O3 and the preparation method of the Cu–Al2O3/SiO2 catalyst on the activity and selectivity of the catalyst were investigated. The catalysts were characterized by XRD, TEM, H2-TPR, NH3-TPD and TG techniques. The results indicated that the addition of Al2O3 to Cu/SiO2 increased the activity and selectivity remarkably. Cu–Al2O3/SiO2 prepared by co-precipitation (COP) exhibited better catalytic performance compared with the catalyst prepared by incipient wetness impregnation (IWI) or ultrasonic impregnation (UI), because the catalyst possessed a good dispersion of Cu particles, a better resistance to the sintering of Cu particles as well as a larger amount of weak acid sites. Over Cu–Al2O3/SiO2 (COP) with the Al2O3 content of 1.1 mmol/g, the yield of 3-methylindole reached 44 % at the third hour of reaction, and the yield could be kept to 41 % even after the reaction time of 51 h.

Vapor-Phase Synthesis of 3-Methylindole from Glycerol and Aniline over Cu/SiO<sub>2</sub>-Al<sub>2</sub>O<sub>3</sub> Catalyst Modified by Co or Ni

This paper investigated the vapor-phase synthesis of 3-methylindole from glycerol and aniline over the catalyst of Cu/SiO2-Al2O3 modified by Co or Ni. The catalysts were characterized by N2 adsorption, H2 temperature-programmed reduction (H2-TPR), inductively coupled plasma (ICP) emission spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), temperature-programmed desorption of ammonia (NH3-TPD), and thermogravimetric (TG) analysis. The results indicated that adding Co or Ni to Cu/ SiO2-Al2O3 improved the performance of the catalyst and Co exhibited higher efficiency than Ni. The yields of 3-methylindole over Cu-Co/SiO2-Al2O3 and Cu-Ni/SiO2-Al2O3 reached 47% and 45%, respectively at the third hour of reaction and the yields remained 44% and 42% after the catalysts were regenerated six times. The characterizations revealed that the addition of Co or Ni to Cu/SiO2Al2O3 improved the interaction between copper and the support, which promoted the dispersion of Cu particles on the surface of the support, and also prevented the loss of the copper component during the reaction. Furthermore, Co or Ni promoter decreased the amount of the middle-strong acid sites on the catalyst surface, which gave rise to a high selectivity for 3-methylindole, and inhibited the formation of the coke. In addition, Co promoter increased the amount of the weak acid sites on the catalyst, which was favorable for the production of 3methylindole. A catalytic mechanism in which copper and weak acid sites acted together to promote the 2444 BAO Zhuo-Ran et al.: Vapor-Phase Synthesis of 3-Methylindole from Glycerol and Aniline over Co or Ni Promoted No.11 formation of 3-methylindole was proposed.

Microhardness And Electrical Properties Of PVC/Cu Composites Prepared By Ball Mill

Polymer matrix composites filled with metals are widely studied for the applications in electrostatic dissipation (ESD) and electromagnetic interference (EMI) shielding. In view of this, the electrical conductivity and the microhardness of the polymer matrix composites based on poly(vinyl chloride) (PVC) as matrix and copper (Cu) as reinforcement were determined. The composites were prepared using ball milling followed by hot pressing. Both constituents PVC and Cu were mixed together in a dry condition at room temperature for 12 h, 24 h and 36 h and then blended powder was hot pressed at 175 °C and 50 MPa. The Cu content was varied from 0 to 40 wt% (9.3 vol%) in the matrix. Optical microscope showed good dispersion of Cu particles in the matrix and the degree of Cu dispersion increased with increasing ball milling time. The electrical conductivity of the composites increased approximately six orders of magnitude for 9.3 vol% Cu composite. A percolation threshold was obtained at 3.7 vol% Cu. The microhardness increased by more than 18 % compared to the pure matrix. For a given loading of Cu, the electrical conductivity and the microhardness of the composites increased with increasing ball-milling time. This was attributed to the better and uniform dispersion of the Cu particles in the matrix at higher ball milling time.

Effect of Alkaline-Earth Metal Oxides on Cu/SiO2-Al2O3 Catalyst for Vapor-Phase Synthesis of 3-Methylindole from Glycerol and Aniline

The effect of the addition of an alkaline-earth metal oxide (MgO, CaO, SrO or BaO) to a Cu/SiO 2 -Al 2 O 3 catalyst for the vapor-phase synthesis of 3-methylindole from glycerol and aniline was investigated. The catalysts were characterized by X-ray diffraction, transmission electron microscopy, H 2 temperature-programmed reduction, NH 3 temperature-programmed desorption, and thermogravimetric and differential thermal analysis. MgO reinforced the interaction between copper and the support, which promoted the dispersion of Cu particles. In addition, MgO increased the amount of weak acid sites and inhibited the formation of coke. As a result, the addition of MgO to Cu/SiO 2 -Al 2 O 3 gave a much improved catalyst. Adding CaO, SrO or BaO to Cu/SiO 2 -Al 2 O 3 deteriorated the catalysts because the dispersion of Cu particles became worse and the amounts of weak acid sites on Cu-SrO/SiO 2 -Al 2 O 3 and Cu-BaO/SiO 2 -Al 2 O 3 were fewer. The addition of the alkaline-earth metal oxides did not change the texture of the coke formed. 研究了碱土金属氧化物的添加对丙三醇和苯胺气相合成 3-甲基吲哚的 Cu/SiO 2 -Al 2 O 3 催化剂性能的影响, 采用 X 射线衍射、透射电镜、H 2 程序升温还原、NH 3 程序升温脱附以及热重-差热等技术对催化剂进行了表征. 结果表明, MgO 能加强活性组分和载体之间的相互作用, 从而促进铜粒子在载体上的分散. 另外, MgO 能增加弱酸中心数, 并且抑制积炭的形成, 因而 Cu-MgO/SiO 2 -Al 2 O 3 催化剂性能大大提高; 而 CaO, SrO 或 BaO 的加入不利于 Cu/SiO 2 -Al 2 O 3 催化剂上 3-甲基吲哚的生成. 这是由于铜粒子在载体上的分散度变差, 而且在 Cu-SrO/SiO 2 -Al 2 O 3 及 Cu-BaO/SiO 2 -Al 2 O 3 催化剂上弱酸中心数较少. 碱土金属氧化物的加入不能改变催化剂上积炭的结构. Alkaline-earth oxides introduced into a Cu/SiO 2 -Al 2 O 3 catalyst for the vapor-phase synthesis of 3-methylindole from glycerol and aniline and MgO improved its performance.

Electro Oxidation of Methanol on Copper Nanoparticles Supported Poly (O- Amino Phenol) Nanotubes

In this article, the electrochemical synthesis and the characterization of Cu nanoparticles dispersed poly (o-aminophenol) (POAP) nanotube electrode is reported. The morphology of the electrode was characterized by scanning electron microscopy (SEM). Catalytic activity and stability for the oxidation of methanol were studied by using cyclic voltammetry and electrochemical impedance spectroscopy (EIS) were performed. The results show that poly (o-aminophenol) nanotubes electrodes significantly enhance the catalytic activity of copper nanoparticles for oxidation of methanol. The results obtained affirm that the dispersion of the copper particles is connected with catalytic response to a higher activity. The nanotubular morphology of poly (o-aminophenol) helps in the effective dispersion of Cu particles facilitating the easier access of methanol to the catalytic sites. The poly (o-aminophenol) nanotubes modified with copper nanoparticles cause a great increase in electroactivity and the electro-catalytic oxidation of methanol.

Highly Stabilized and Finely Dispersed Cu2O/TiO2: A Promising Visible Sensitive Photocatalyst for Continuous Production of Hydrogen from Glycerol:Water Mixtures

Cu-doped TiO2 with varying amounts of Cu (0.2, 0.3, 0.5, 1, 2, and 5) are prepared by impregnation method and calcined at 350 and 450 °C for 5 h. These catalysts are characterized by X-ray diffraction, diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy energy-dispersive X-ray spectroscopy (EDAX), and transmission electron microscopy (TEM). The DRS studies are clearly showing the expanded photo response of TiO2 into the visible region on impregnation of copper ions. TEM images are depicting the fine dispersion of Cu particles on TiO2 surface. XPS studies are showing change in the binding energy values of Ti 2p, O 1s, and Cu 2p, indicating that copper ions are in interaction with TiO2. XPS results are also confirming that the oxidation state of copper is +2 in samples calcined at 350 °C and +1 in samples calcined at 450 °C. EDAX analysis supports the presence of copper species on the surface layers of TiO2. Photocatalytic hydrogen production activity...

Microstructure and Mechanical Property of Copper Bearing Eutectoid Steel

Isothermal heat treatment was performed for austenitized Cu bearing eutectoid steels (Fe–0.8%C–Cu alloys). Microstructural observations revealed that the pearlite transformation is significantly retarded by the addition of Cu, but the morphology of pearlite, such as lamellar spacing and block size, are hardly influenced by the Cu addition. From the result of chemical analysis for cementite phase, it was found that the redistribution of Cu had occurred between ferrite and cementite through the interfacial diffusion during pearlite transformation and then the precipitation of Cu takes place simultaneously within ferrite phase. Furthermore, in the 2% Cu steel, age hardening behavior was found at the same temperature applied to the isothermal pearlite transformation. This means that the precipitation of Cu does not complete on pearlite transformation and the ferrite in pearlite structure is in the supersaturated state. Yield strength and tensile strength of the pearlite steels depend on not only lamellar spacing but also the dispersion of Cu particles within the ferrite phase. For example, 2% Cu addition increases yield strength and tensile strength by about 250 MPa without reducing ductility so much.

Factors influencing the catalytic activity of SBA-15-supported copper nanoparticles in CO oxidation

Copper nanoparticles were deposited onto mesoporous SBA-15 support via two different routes: post-grafting method and incipient wet impregnation method. Both XRD and TEM reveal that the post-grafting can make Cu particles very small in size and highly dispersed into channels of SBA-15, while the impregnation method mainly forms large Cu particles on the external surface of SBA-15. TPR experiments show that CuO species formed by the post-grafting method is more reducible than that prepared by the impregnation method. The catalytic activity tests for CO oxidation manifests that the sample prepared by the post-grafting method has a much higher activity than that prepared by the impregnation method, with a lowering of 50 °C for T 50, showing a strong dependence of catalytic activity on the size and dispersion of Cu particles. Besides the preparation procedure, other factors including calcination temperature, reduction treatment, copper loading as well as the feed composition, have an important effect on the catalytic activity. The best performance was obtained when the catalyst was calcined at 500 °C and reduced at 550 °C. The calcination and reduction treatment at high temperature have been found to be necessary to completely remove the organic residue and to generate active metallic copper particles.

Microstructure and properties of monotectic Cr—Cu cast irons

A metal quasi-composite, containing copper inclusions within a chromium cast iron matrix was investigated. The dispersion of Cu particles was produced directly from the melt by cooling through the miscibility gap. The effect of casting parameters (pouring temperature and cooling rate) on the size and distribution of Cu particles has been studied using optical metallography, SEM, and TEM. It has been shown that Cu particles are responsible for improved machineability and wear resistance of Cr cast irons with 10 -12 wt-%Cu, since Cu particles break up the network of primary carbides and also act as a solid lubricant.

The influence of chlorine on the dispersion of Cu particles on Cu/ZnO(0001) model catalysts

One of the ways in which chlorine is thought to poison metal catalysts on oxide supports is by altering their dispersion. The effect of chlorine on Cu/ZnO(0001) model catalysts was studied by vapor‐depositing Cu onto Zn‐terminated ZnO(0001), both with and without preadsorbed Cl2, using XPS, ion scattering spectroscopy (ISS), temperature‐programmed desorption (TPD), work function, and band bending measurements. A disordered, but nearly close‐packed overlayer of Cl adatoms forms at saturation with ∼0.30 Cl adatoms per Zn site. Without Cl, vapor‐deposited Cu grows in two‐dimensional islands that cover ∼33% of the ZnO, after which these islands thicken (i.e., as 3D Cu particles) while the clean ZnO between these Cu islands gets covered with Cu only very slowly. Preadsorbed Cl decreases the fraction of the surface that is covered by Cu islands by a factor of three, so Cl(a) either decreases the number of 2D Cu islands or their critical area before thickening. Both are consistent with weaker binding of Cu to the Cl‐covered surface than to the clean ZnO. The TPD features for formate decomposition after HCOOH adsorption onto Cu/ZnO(0001) were suppressed with preadsorbed Cl, but the CO2 : CO selectivity increased. When Cu was deposited onto Cl‐presaturated ZnO, neither the Zn‐ nor Cu‐formate peaks were observed, showing that Cl covers both the Zn sites and the growing Cu islands, as suggested by ISS also.

Fabrication and mechanical properties of 5 vol% copper dispersed alumina nanocomposite

An optimum route to fabricate the Al 2O 3 Cu nano-composite with sound microstructure and desired mechanical properties was investigated. Two methods for developing a uniform dispersion of Cu particles in Al 2O 3 were compared on the basis of the resulting microstructures and mechanical properties. SEM and TEM analyses for the composites fabricated by reduction and sintering process using Al 2O 3 CuO powder mixture showed that the nano-sized Cu particles were well distributed and situated on the grain boundaries of the Al 2O 3 matrix. The composite, hot-pressed at 1450 °C, exhibited the maximum fracture strength and enhanced toughness compared with monolithic Al 2O 3. The strengthening was mainly attributed to the refinement of Al 2O 3 matrix grains. The toughening mechanism in Al 2O 3 Cu composite was discussed by the observed microstructural features and theoretical predictions based on crack bridging model and thermal residual stress effect.