Dispersed Copper Particles Research Articles

Si-Cu contact mass for catalysis in coatings industry for oil and gas pipes

Two contact masses were obtained and analyzed for their catalytic properties in the production of hydrophobic coatings. These masses are based on the silicon-copper system and consist of 25%Cu-75%Si and 50%Cu-50%Si compositions. A standard method of copper(I) chloride reduction was optimized to obtain finely dispersed copper particles with high catalytic activity. It is shown that reduction is possible directly in contact with silicon, the resulting average diameter of copper particles is 5-10 microns in both contact masses (25%Cu-75%Si and 50%Cu-50%Si). A metallographic analysis revealed a loose morphology of the silicon-copper phase interfaces, which is necessary to enhance the catalytic activity of the contact masses. Local chemical analysis by scanning electron microscopy has established the ratio of the particle size of the initial polycrystals of copper chloride(I) and the resulting copper particles as a result of reduction on silicon. The process of deep reduction makes it possible to obtain particles up to 5 microns in size. These results provide useful insights into the formulation of coatings containing organosilicon compounds to reduce friction in hydrocarbon transport.

One-pot synthesis of 2,5-bis(propoxymethyl)furan from 5-hydroxymethylfurfural by using the supported copper catalyst and hierarchical pore ZSM-5 zeolite

The highly-efficient conversion of 5-hydroxymethylfurfural (HMF) to 2,5-bis(propoxymethyl)furan was achieved via the one-pot route, which were performed by the combination of supported copper catalyst and hierarchical pore ZSM-5 zeolite. Among the supported copper catalyst, the Cu/Al2O3 catalyst exhibited the excellent activity and selectivity in the hydrogenation of HMF, obtaining a 98.7% yield of BHMF at 100 °C for 6 h under 2.5 MPa of H2. The reason might be attributed to that the highly dispersed copper particles and relatively weaker acid sites, which improved the hydrogenation activity of catalyst and suppressed the occurrence of side reaction. In the one-pot synthesis of BPMF, the Cu/Al2O3 catalyst and HP-ZSM-5 zeolite were responsible for HMF hydrogenation and BHMF etherification, respectively, and the competition between them is negligible. This work provides a simple route to produce furanic diether from HMF.

Synthesis of CuAl-LDHs by Co-Precipitation and Mechanochemical Methods and Selective Hydrogenation Catalysts Based on Them

The paper presents the results of the synthesis and study of CuAl layered double hydroxides (LDHs) as well as their application as catalysts for the selective hydrogenation of crotonaldehyde. Phase-homogeneous LDHs were obtained by co-precipitation and mechanochemical methods, and critical parameters ensuring the formation of the target product were identified. In the case of coprecipitation, the formation of LDH is most affected by the pH of the reaction medium and the CO32−/Al3+ ratio. The optimal CO32−/Al3+ ratio is ca. 0.5–0.8 and pH 9.5–10.0. When mechanochemical synthesis is used, at 500 m·s−2 and 60 min, it is possible to obtain a single-phase CuAl LDH, whereas at higher energies, LDH is destroyed. The mechanochemical method makes it possible not only to reduce the synthesis time and the amount of alkaline wash water but also to obtain more dispersed copper particles with a higher hydrogenating activity. The conversion of 2-butenal (T = 80 °C, P = 0.5 MPa, 180 min, ethanol) for this sample was 99.9%, in contrast to 50.5% for the catalyst obtained by co-precipitation. It is important that, regardless of the conversion, both catalysts showed high selectivity (S = 90–95%) for the double bond hydrogenation.

Synthesis of flower-like MnO2 nanostructure with freshly prepared Cu particles and electrochemical performance in supercapacitors

Four types of flowerlike manganese dioxide in nano scale was synthesized via a liquid phase method in KMnO4-H2SO4 solution and Cu particles, wherein the effect of Cu particles was investigated in detail. The obtained manganese dioxide powder was characterized by XRD, SEM and TEM, and the supercapacity properties of MnO2 electrode materials were measured. The results showed that doping carbon black can benefit to better dispersion of copper particles, resulting in generated smaller size of Cu particles, and the morphology of MnO2 nanoparticles was dominated by that of Cu particles. The study of MnO2 synthesis by different sources of Cu particles showed that the size of MnO2 particles decreased significantly with freshly prepared fine copper powder compared with using commercial Cu powder, and the size of MnO2 particles can be further reduced to 120 nm by prepared Cu particles with smaller size. Therefore, it was suggested that the copper particles served as not only the reductant and but also the nuclei centre for the growth of MnO2 particles in synthesis process MnO2, and that is the reason how copper particles worked on the growth of flower-like MnO2 and electrochemical property. In the part of investigation for electrochemical property, the calculated results of b values indicated that the electrode materials have pseudo capacitance property, and the highest specific capacitance of 197.2 F g-1 at 2 mV s-1 and 148 F/g at 1 A/g were obtained for MCE electrode materials (MnO2 was synthesized with freshly prepared copper particles, where carbon black was used and dispersed in ethanol before preparation of Cu particles). The values of charge transfer resistance in all types of MnO2 materials electrodes were smaller than 0.08 Ω. The cycling retention of MCE material electrode is still kept as 93.8% after 1000 cycles.

The feasibility of masks and face shields designed by 3D printing makers; some considerations of their use against the COVID-19

The use of mask and face shield has been established as one of the main preventive measures for the control of COVID 19 spread. In Mexico, as well as in other regions of the world, 3D printing has been employed for the design and production of masks and face shields as personal protective equipment (PPE). These models have been fabricated mainly by the makers, industries, and university communities; therefore, it is necessary to analyze the feasibility of the 3D printed PPE to understand its advantages and limitations. In this work, some characteristics of masks and face shields fabricated by additive manufacturing were studied to explore their viability as protection against flow fluids similar to human sneeze. In the present paper, the PPE was designed, and 3D printed utilizing three types of polylactic acid (PLA) as base material. The morphology and the surface elemental analyses of sectioned samples were analyzed by scanning electron microscopy (SEM) and energy dispersion x-ray spectroscopy (EDS). Showing spacing between printed layers, porous areas, and dispersed copper particles. On the other hand, a computational fluid dynamics (CFD) simulation was carried out, the results demonstrated the importance of using PPE for protection of a possible exposure to a “contaminated” aerosol and human sneeze. Based on the abovementioned results, it is possible to consider the commercial PLA as suitable material for the manufacturing of PPE due to its capability to be disinfected employing isopropanol, ethanol, or commercial disinfectants.

Theoretical Insights into Synergistic Effects at Cu/TiC Interfaces for Promoting CO2 Activation.

The adsorption behaviors of CO2 at the Cun/TiC(001) interfaces (n = 1–8) have been investigated using the density functional theory method. Our results reveal that the introduction of copper clusters on a TiC surface can significantly improve the thermodynamic stability of CO2 chemisorption. However, the most stable adsorption site is sensitive to the size and morphology of Cun particles. The interfacial configuration is the most stable structure for copper clusters with small (n ≤ 2) and large (n ≥ 8) sizes, in which both Cu particles and TiC support are involved in CO2 activation. In such a case, the synergistic behavior is associated with the ligand effect introduced by directly forming adsorption bonds with CO2. For those Cun clusters with a medium size (n = 3–7), the configuration where CO2 adsorbs solely on the exposed hollow site constructed by Cu atoms at the interface shows the best stability, and the charger transfer becomes the primary origin of the synergistic effect in promoting CO2 activation. Since the most obvious deformation of CO2 is observed for the TiC(001)-surface-supported Cu4 and Cu7 particles, copper clusters with specific sizes of n = 4 and 7 exhibit the best ability for CO2 activation. Furthermore, the kinetic barriers for CO2 dissociation on Cu4- and Cu7-supported TiC surfaces are determined. The findings obtained in this work provide useful insights into optimizing the Cu/TiC interface with high catalytic activation of CO2 by precisely controlling the size and dispersion of copper particles.

High Performance and Sustainable Copper-Modified Hydroxyapatite Catalysts for Catalytic Transfer Hydrogenation of Furfural

Designing and developing non-noble metal-based heterogeneous catalysts have a substantial importance in biomass conversion. Meerwein-Ponndorf-Verley (MPV) reaction is a significant pathway for eco-friendly catalytic transfer hydrogenation (CTH) of biomass derived furfural into furfuryl alcohol. In this work, a series of copper-supported hydroxyapatite (HAp) catalysts with different copper loadings (2–20 wt.%) were prepared by a facile impregnation method and tested in the reduction of furfural to furfuryl alcohol using 2-propanol as a hydrogen donor. The structural and chemical properties of the synthesised catalysts were analysed by using various techniques (XRD, N2 sorption, SEM, TEM, UV-DRS, ICP, FTIR, TPR, TPD-CO2 and N2O titration). The effect of copper loading was found to be significant on the total performance of the catalysts. The results demonstrate that 5CuHAp catalyst possess highly dispersed copper particles and high basicity compared to all other catalysts. Overall, 5CuHAp exhibited highest conversion (96%) and selectivity (100%) at 140 °C at 4 h time on stream. The optimised reaction conditions were also determined to gain the high activity.

Chemical Copper Plating of Cotton Fabrics by Photochemical Activation of the Surface

Activation of the surface of cotton fabrics before chemical copper plating is proposed to be carried out by applying dispersed copper particles. For this purpose, physical and chemical processes that occur in thin layers of copper chloride solutions under the influence of electromagnetic solar rays of the visible spectrum are used. Initially, copper chlorides interact with cellulose, which is the main component of the tissue, and form copper monochloride. It is shown that this interaction is stimulated by solar rays. After that, the fabric is moistened with a solution of ascorbic acid and again exposed to sunlight. Under the action of photons of solar radiation, electrons in a semiconductor acquire additional energy and restore copper to the elemental state, and the vacancies formed are filled with electrons due to the oxidation of ascorbic acid. As a result of these processes, a film is formed on the surface of the tissue containing copper particles that can catalyze chemical copper plating.

Thermal conduction of the magnetic fluids mixing micrometer size particles

In this study, thermophysical properties of magnetic fluids mixing micrometer size spherical copper particles were investigated experimentally. To examine the behavior of dispersed micrometer size copper particles in the magnetized magnetic fluid, visualization experiments were performed by using a dark field microscope. From the visualization experiments, cluster formations of the copper particles in the magnetic field direction in the magnetic fluid under applied uniform magnetic field were observed. The thermal conductivity of the test fluid was measured by using the transient hot wire method. Thermal conductivity of the magnetic fluid with randomly dispersing copper particles is larger than the thermal conductivity of the base magnetic fluid. In case of the magnetic fluid mixed 12 vol% of spherical copper particles, it was estimated that the thermal conductivity in the field direction increases by 1.7 times or more of the thermal conductivity of the fluid in the absence of magnetic field. The Landau-Lifshitz equation for estimating the relationship between the thermal conductivity and the internal structure was expanded to consider spherical shape of the dispersed particles in the fluid and the particle distribution state was estimated by using the expanded Landau-Lifshitz equation.

Диэлектрлі беттерде антибактериалды мысқұрамды наноқабықшаларды алу

Activation of the surface of cotton fabrics before obtaining a chemical copper film is recommended to be carried out by precipitation of dispersed copper particles. For this purpose, physical and chemical processes occurring in thin layers of copper chloride solutions under the influence of the visible spectrum of electromagnetic solar radiation are used. In this case, copper chlorides interact with cellulose, which is the main component of the fabric, forming copper monochloride. It is shown that this interaction occurs from exposure to sunlight. After that, the fabric is moistened with a solution of ascorbic acid and again exposed to solar radiation. Electrons located in a semiconductor under the influence of solar photons receive additional energy and oxidize the copper element, and the free spaces that appear in this case are filled with electrons depending on the oxidation of ascorbic acid. As a result of these processes, a shell containing copper particles that can catalyze the chemical copper is formed on the surface of the tissue.

Understanding methanol synthesis from CO/H2 feeds over Cu/CeO2 catalysts

Understanding copper-based methanol synthesis catalysts as a function of catalyst type and applied reaction conditions is an area of active industrial and academic research. In this work, results of a methanol synthesis study over a Cu/CeO2 catalyst using CO/H2 feeds are presented, using catalyst performance data combined with catalyst characterisation information (DRIFTS, XPS, TPR, XRD) obtained during start-up and under steady state methanol synthesis conditions. The results indicate that the active site and reaction mechanism for methanol synthesis over Cu/CeO2 are different from the conventional Cu/ZnO/Al2O3 catalyst, with CO, rather than CO2, being the carbon source for methanol. Fixed-bed micro reactors were employed to obtain catalyst performance data in discrete bed sectors using experimental spatial discretisation methods. Methanol synthesis activity over Cu/CeO2 from CO/H2 is preceded by transient CO2 formation, with the onset of methanol synthesis activity observed when the CO2 formation reaches its peak. Considerable differences between reactor bed sectors are observed during start-up, with CO2 formation, CO2 re-adsorption (as surface carbonates and formates), methanol formation and transient methanol decomposition occurring to different degrees and at different time scales.The interfaces of defective CeO2−x in contact with highly dispersed copper particles form the active site of the catalyst under steady-state methanol synthesis conditions, with the copper oxidation state being a combination of 0 and +1 states. The CeO2−x defect sites are formed during start-up upon reaction of CeO2 with CO. The CO2 thus formed leads to catalyst deactivation due to build-up of carbonate and formate species on the catalyst surface. A gradient of progressive poisoning/deactivation is observed going further down the catalyst bed, where the level of deactivation can be controlled by modifying the CO content in the feed. CO2 thus acts as a poison for the Cu/CeO2 catalyst, and addition of even low levels of CO2 to the feed leads to an evenly deactivated catalyst. During start-up in CO/H2, transient CO2 and H2O formation is also observed in the case of Cu/ZnO/Al2O3, ascribed to partial reduction of ZnO, similar to the partial reduction of CeO2 as seen in Cu/CeO2. The key difference between the two systems is the absence of CO2 and H2O re-adsorption on Cu/ZnO/Al2O3, resulting in stable methanol production distributed equally over the catalyst bed. Introduction of CO2 to the CO/H2 feed in case of Cu/ZnO/Al2O3 leads to reduction of Cu+ to Cu0 and a change in methanol synthesis mechanism from CO to CO2 hydrogenation.

Chemical synthesis of copper nanoparticles in aqueous solutions in the presence of anionic surfactant sodium dodecyl sulfate

Well dispersed copper particles with size from 15 to 100 nm and their aggregates up to 320 nm were obtained by chemical reduction in the presence of anionic surfactant sodium dodecyl sulfate. As a reducing agent hydrazine hydrate of various volumes (1, 3 and 6 ml) was used with a fixed volume of solvent (40 ml), a sample of the copper (II) chloride salt and at pH = 11 of the reaction mixture. The formation of copper nanoparticles and their stability over time were controlled by UV–vis spectroscopy for two weeks. The morphology of the surface and the elemental (chemical) composition of films with copper nanoparticles were characterized by a scanning electron microscope.

Thermal Performance Evaluation of Friction Stir Welded and Bolted Cold Plates with Al/Cu Interface

An attempt is made to design and fabricate a cold plate with aluminum-copper dissimilar interface joined by friction stir welding. Optimum welding conditions for obtaining sound-quality corner and T joints with an aluminum-copper interface were established. Welded cross sections of the friction stir welded cold plate were analyzed to understand the bonding characteristics. Computational fluid dynamics (CFD) was used to evaluate the fluid-flow characteristics and thermal resistance of friction stir welded cold plate and the resulted are compared with the conventional bolted cold plate configuration. For CFD modeling of a cold plate with a dissimilar interface, a new methodology is proposed. From the CFD analysis and experimental results, it is observed that friction stir welded cold plate offered better thermal performance compared to the bolted cold plate and it is due to the metallurgical bonding at the aluminum-copper interface with the dispersion of copper particles.

Effects of Metal Particles Decoration on n-Type Chalcogenides Processed by Open Die Pressing

The effects of copper particles dispersed into Bi1.9Sb0.1Te2.85Se0.15 nanopowders and sintered by open die pressing (ODP) have been investigated. Submicrometric copper particles were obtained by decomposing copper acetate molecules dispersed into chalcogenides nanopowders. The acetate powders were decomposed during the sintering process at 390 °C obtaining a fine dispersion of copper particles with dimensions in the order of 500 nm. Contents up to 0.2 wt.% of copper were investigated. ODP, previously introduced as a forming process for sintering and texturing p-type (Bi0.2Sb0.8)2Te3 nanopowders, has been applied to n-type chalcogenide: the mixed alloy nanopowders and copper acetate were compacted inside a metallic protective shell and fast pressed between two heated plates, keeping the composite under load for sintering. ODP processing ensures complete consolidation of nanopowders and material texturing with the basal (00l) planes of the hexagonal crystal cell oriented parallel to the plates. The X-ray diffraction pattern shows an orientation factor, f, obtained by the Lotgering method, up to 64 %. Thermoelectric performance of the samples was measured by the Harman method in the range of 20–170 °C. Figure of merit (ZT) behavior with temperature was improved in copper-dispersed samples showing a shift of the maximum value at higher temperatures. This effect can be mainly associated with an improvement of electrical conductivity, due to the presence of the copper particles.

Vapor-phase synthesis of 3-methylindole from glycerol and aniline over zeolites-supported Cu-based catalysts

Zeolites-supported Cu-based catalysts for the vapor-phase synthesis of 3-methylindole from glycerol and aniline were investigated. The catalysts were characterized by N2 adsorption, XRD, NH3-TPD and TG–DTA techniques. The results indicated that Cu/NaY catalyst exhibited higher activity and selectivity than Cu/5A, Cu/HZSM-5 or Cu/MCM-41 due to better dispersion of copper particles and larger amount of weak acid sites on the catalyst. The addition of Na2O to Cu/NaY not only improved the selectivity of the catalyst efficiently, but also inhibited the deactivation of the catalyst. Over Cu/NaY–Na2O, the selectivity of 3-methylindole reached 72.3% and the yield of the aim product was up to 50.4%. The characterizations revealed that Na2O promoter could decrease the amount of middle-strong acid sites of the catalyst remarkably as well as prevent from the formation of the coke. Furthermore, a probable catalytic mechanism for the synthesis of 3-methylindole from glycerol and aniline was proposed.

Catalytic properties of M-Cu/ZrO2 (M = Fe, Co, Ni) in steam reforming of ethanol

We show that bicomponent supported catalysts M-Cu/ZrO2 (M = Fe, Co, Ni) are considerably more efficient than Cu/ZrO2 in steam reforming of ethanol at 350-550 °C. We have found that Fe-Cu/ZrO2 has increased activity and selectivity in ethanol steam reforming, due to the presence of highly dispersed copper particles and iron oxide particles, which are active in the water-gas shift reaction, and as a result carbon monoxide (a secondary product of ethanol steam reforming) is converted to the target CO2 and H2.

Novel Cu and Cu2In/aluminosilicate type catalysts for the reduction of biomass-derived volatile fatty acids to alcohols

Abstract This work relates to the consecutive reduction of short chain carboxylic acids (volatile fatty acids, VFAs) to alcohols as main products. Acetic acid (AA) was used as a reactant to model the VFAs that can be produced by either thermochemical or biological biomass degradation. The amorphised zeolite supported copper catalysts (Cu/SiAl), especially the In-modified CuIn/SiAl catalysts, showed high hydroconversion activity and selectivity for alcohol, ester and aldehyde. Catalysts containing dispersed copper particles in amorphous aluminosilicate were obtained by dehydrating and H2-reducing Cu-forms of low-silica synthetic zeolites (A, X, P). The activity of the highly destructed Cu-aluminosilicates was found to depend on the structure of the zeolite precursor. The formation of ethyl acetate could be suppressed by adding water to the AA feed and by modifying the catalyst, e.g. by In2O3 additive. In the catalysts modified by In2O3 additive formation of copper-indium alloy phase (Cu2In intermetallic compound) was detected resulting in a different selectivity than the one recorded for the Cu/SiAl.

Surface characterization of ZnO/ZnMn2O4 and Cu/Mn3O4 powders obtained by thermal degradation of heterobimetallic complexes

From the selective transformation of the heterometallic (Zn–Mn or Cu–Mn) carboxylate complexes with 2,2′-bipyridyl by thermal degradation at relatively low (350°C) temperature, it was possible to get either well defined spinel ZnMn2O4 over zinc oxide or well dispersed copper particles surrounded by a manganese oxide (Mn3O4) in a core–shell like structure. Morphology of the powder surface was examined by scanning electron microscopy with energy dispersive X-ray microanalysis (SEM/EDX). Surface composition was determined by X-ray photoelectron spectroscopy (XPS). Specific surface of the powders by nitrogen adsorption was found to be 33±0.2 and 9±0.06m2g−1 for Zn–Mn and Cu–Mn samples, respectively, which is comparable to those of commercial products.

Al–Cu–Fe quasicrystals for steam reforming of methanol: a new form of copper catalysts

Alloy catalysts were prepared by leaching various structures of Al–Cu–(Fe) alloys (quasicrystal (QC), beta- or theta-phase) in NaOH and Na 2CO 3 aqueous solutions. Comparison of the catalytic properties for steam reforming of methanol (SRM) on different Al–Cu–(Fe) alloy phases (quasicrystalline versus crystalline phase) was made. At high temperatures (e.g., 360 °C), the catalytic activity of the QC catalyst (5% Na 2CO 3-leached) for the SRM was much higher than that of other phase catalysts. No sintering of highly dispersed copper particles on QC catalyst was observed by XRD measurements even after the SRM reaction at 360 °C. We propose that the high catalytic activity and the excellent thermal stability of copper particles on QC catalyst are due to the immiscibility of Fe with Cu and the interaction with QC surface.

Synthesis of Uniform Cu Paricles by Hydrazine Reduction from Copper Sulfate Solution

In order to prepare the uniform copper particles from copper sulfate solution by using hydrazine as a reduction agents, the reduction behavior of copper particles from copper sulfate was investigated in detail at room temperature by the observation of reaction products. The effects of <TEX>$NH_4$</TEX>OH and <TEX>$Na_4$</TEX><TEX>$P_2$</TEX><TEX>$O_{7}$</TEX> on the formation of uniform copper particles were discussed. (<TEX>$NHCu_3$</TEX>)<TEX>$_4$</TEX><TEX>$SO_4$</TEX>was completely formed at over pH 11 by adding <TEX>$NH_4$</TEX>OH in copper sulfate solution. The fine <TEX>$Cu_2$</TEX>O with the particle size of 50 nm was produced in the initial reduction process of (NH<TEX>$Cu_3$</TEX>)<TEX>$_4$</TEX><TEX>$SO_4$</TEX>solution with <TEX>$Na_4$</TEX><TEX>$P_2$</TEX><TEX>$O_{ 7}$</TEX> and then the Cu<TEX>$_2$</TEX>O was converted into copper particles by inserting additional hydrazine. When Cu(NH<TEX>$_3$</TEX>)<TEX>$_4$</TEX>SO<TEX>$_4$</TEX>solution with <TEX>$Na_4$</TEX><TEX>$P_2$</TEX><TEX>$O_{ 7}$</TEX> was reduced at <TEX>$80^{\circ}C$</TEX> by hydrazine, the highly dispersed copper particles with the particle size of about 0.8 <TEX>$\mu\textrm{m}$</TEX> was obtained.