Influence of magnesia modification on the properties of copper oxide supported on gamma-alumina

XRD, BET, TPR, UV-vis DRS and in situ FT-IR were employed to investigate the dispersion, reduction and CO(2)-adsorption behaviors of copper oxide supported on magnesia modified gamma-Al(2)O(3) (Mg-Al) samples. The results indicate that magnesia could be highly dispersed on the surface of gamma-Al(2)O(3) to form a monolayer and the dispersion capacity is about 1.55 mmol/(100 m(2)gamma-Al(2)O(3)). For copper oxide supported on Mg-Al samples, both the dispersion capacity and the reduction temperature of surface CuO decrease with the MgO loading. CO(2)-adsorption IR results show that the surface strong basic amount for the catalysts increases with the dispersed MgO loading. In addition, the activity of CO oxidation suggests that the main active species in this system should be small CuO cluster and the existence of dispersed MgO enhances the activity of CO oxidation. The catalysts might be applied in pollution control devices for vehicle exhaust, CO gas sensors, catalytic combustion and gas purification of CO(2) lasers. All the results have been discussed by the consideration of the variation of gamma-Al(2)O(3) surface structure before and after magnesia modification.     

Curing and properties of chloroprene and butadiene rubber (CR/BR) blends cross-linked with copper(I) oxide or copper(II) oxide

This paper discusses the curing and properties of chloroprene and butadiene rubber (CR/BR) blends cross-linked with copper(I) oxide (Cu₂O) or copper(II) oxide (CuO). The results revealed that the cross-linking degree of CR/BR blends decreased with the increasing amount of butadiene rubber (BR) in the blends. The mechanical properties of cured CR/BR blends depended on the proportion of elastomers in blends, as well as on the type and amount of the cross-linking agent (Cu₂O, CuO). The cross-linking of CR/BR/Cu₂O or CR/BR/CuO blends followed according to cationic mechanism, using Lewis acid, copper(I) chloride (CuCl) or copper(II) chloride (CuCl₂) generated in situ. Additionally, the prepared compositions, both unfilled and filled, were characterized by very high resistance to flame.     

The composite catalysts of Cu/CuxO nanoparticles supported on the carbon fibers were prepared for styrene oxidation reaction

In this paper a novel simple method for preparing two different catalysts with various‐valences copper was reported. Carbon nanofibers supported copper‐cuprous oxide nanoparticles (Cu‐Cu₂O NPs/CNFs) and copper oxide nanoparticles (CuO NPs/CNFs) through electrospinning, adsorption and reduction in the high‐pressure hydrogenation and the high‐temperature calcination methods. These catalysts were investigated by a series of characterizations and were applied in reaction in nitrogen atmosphere, which had a good catalytic activity and selectivity of benzaldehyde for the reaction. Above all, the new study has been certified clearly, in which Cu‐Cu₂O NPs/CNFs and CuO NPs/CNFs composite catalysts enhanced the generation of benzaldehydeand the excellent catalytic properties were exhibited.     

铂负载二氧化钛光催化剂在单波长下苯乙炔高选择性加氢（英文）

苯乙烯是一种非常重要的化工原料,它是工业上生产聚苯乙烯、树脂和丁苯橡胶的重要单体,而苯乙烯单体中经常含有苯乙炔杂质,影响苯乙烯的聚合性能,因此研究苯乙炔选择性加氢生成苯乙烯具有十分重要的工业意义.传统的热催化苯乙炔加氢反应会用到易燃易爆的氢气,引起操作的危险性,因此,开发具有环境友好型的加氢反应体系具有很重要的意义.光催化加氢反应利用光生电子强的还原能力,还原质子产生活性的氢物种加氢,相较于传统的热催化使用氢气作为加氢源加氢,能够在温和的条件下实现高选择性加氢.基于此,本文利用Pt/TiO2作为光催化剂,甲醇作为加氢源实现了在385 nm单波长光照下苯乙炔的高选择性加氢.首先,我们利用光沉积的方法将Pt负载在TiO2的表面,通过透射电子显微镜图像和紫外可见吸收光谱表征了负载在TiO2表面Pt的颗粒分布和光学性质.结果表明负载的Pt的颗粒大约在5 nm左右,Pt的负载改变了TiO2在可见光区的吸收性能.XPS结果显示,通过光沉积得到的Pt的价态为金属态和氧化态共存.光催化苯乙炔加氢实验表明,Pt/TiO2催化剂在室温常压条件下不仅具有高的苯乙炔光催化转化率,当光照达8 h后,苯乙炔完全转化,而且在6 h之内苯乙烯选择性保持在91.3%,具有高的苯乙烯选择性.通过对负载的Pt的含量进行了优化,筛选出当Pt的负载量为1 wt%时,苯乙炔的转化率最高.为了对比,利用传统热催化的方法氢气作为加氢源进行了苯乙炔加氢实验,结果发现,使用氢气作为加氢源时,虽然苯乙炔的转化率为100%,但产物是过加氢的产物乙苯.这主要是因为在光催化反应过程中,TiO2导带上的电子迁移至Pt颗粒上,导致Pt的电子密度增加,Pt颗粒表面高的电子密度有利于加氢中间产物苯乙烯的脱附,因此,在光催化加氢过程中不会发生过加氢反应,具有高的苯乙烯选择性.同时,扩展实验表明,Pt/TiO2光催化剂对其他类型的炔烃加氢也具有高的选择性,表明Pt/TiO2光催化炔烃加氢具有普适性.由此可见,光催化炔烃加氢未来将成为一种环境友好而高效的方法.     

碳化硅负载氧化铜催化剂低温NH3选择性催化还原NOx的性能

采用湿浸渍法制备了碳化硅负载的氧化铜(CuO/SiC)催化剂,采用扫描电镜(SEM)、X射线衍射(XRD)和X射线光电子能谱(XPS)等对其进行了表征,在模拟烟气条件下研究了该催化剂对低温NH_3选择性催化还原NO_x的性能。结果表明,CuO/SiC还原NO的催化活性与氧化铜含量和反应温度有关。负载质量分数为5%的CuO/SiC催化剂在低温下表现出较高的活性,虽然SO_2对其催化活性略有抑制;研究发现,NO还原反应发生在被吸附的氨与气相的NO或弱吸附的NO之间。所制备的CuO/SiC催化剂为实际的工业应用提供了新的选择。     

A copper (I or II)/diethylphosphite catalytic system for base-free additive dimerization of alkynes

Copper (I) or copper (II) salts and oxides promote regioselective head-to-head additive dimerization of aromatic and aliphatic terminal alkynes in the presence a catalytic amount of diethylphosphite. The reaction proceeds under ambient conditions without any added base with the formation of 1,4-disubstituted 1,3-enynes with the E isomer as major product in good to excellent yields. A plausible mechanism for additive dimerization of terminal alkynes is proposed.     

Quasi-homogeneous hydrogenation with platinum and palladium nanoparticles stabilized by dendritic core-multishell architectures

Platinum and palladium nanoparticles, supported and stabilized by polymeric core-shell architectures, proved to be active catalysts for hydrogenation reactions. Here, two different reactions were used as probes to investigate the influence of the polymeric support: the hydrogenation of α-methyl styrene (AMS) to cumene and the partial hydrogenation of 1,5-cyclooctadiene (COD). We found that the stability of the nanoparticles and the rate of reaction are higher in the presence of a hydrophobic octadecyl shell within a three-shell polymer system. The kinetic study of AMS hydrogenation showed much higher activities for palladium nanoparticles than for platinum nanoparticles, and the obtained results (e.g., 35 kJ/mol for the activation energy) are of the same order of magnitude as reported earlier for palladium supported on alumina. A methanol/n-heptane biphasic mixture was tested for catalyst recycling and allowed for highly efficient catalyst separation with very low metal leaching.     

Synthesis of platinum nanoparticles by reaction of filamentous cyanobacteria with platinum(IV)-chloride complex

Interaction of cyanobacteria (Plectonema boryanum UTEX 485) with aqueous platinum(IV)-chloride (PtCl(4) degrees ) has been investigated at 25-100 degrees C for up to 28 days, and 180 degrees C for 1 day. The addition of PtCl(4) degrees to the cyanobacteria culture initially promoted the precipitation of Pt(II)-organic material as amorphous spherical nanoparticles (< or =0.3 microm) in solutions and dispersed nanoparticles within bacterial cells. The spherical Pt(II)-organic nanoparticles were connected into long beadlike chains by a continuous coating of organic material derived from the cyanobacterial cells, and aged to nanoparticles of crystalline platinum metal with increase in temperature and reaction time. The stepwise reduction for the formation of platinum nanoparticles in the presence of cyanobacteria was deduced to be Pt(IV) [PtCl(4) degrees ] --> Pt(II) [Pt(II)-organics] --> Pt(0). Spherical platinum-bearing nanoparticles were not present in abiotic PtCl(4) degrees experiments conducted under similar conditions and duration.     

An optimistic approach “from hydrophobic to super hydrophilic nanofibers” for enhanced absorption properties

Water holding capacity becomes essential for hygiene applications including baby diapers. Microfibers of hydrophilic polymers have been useful source for such applications. While, super hydrophilic and stable nanofibers incorporation with functional antibacterial agent are essential to get higher absorption of water along with antimicrobial activity against harmful bacteria. In current work, hydrophobic polymeric nanofibers are transformed to super hydrophilic nanofibers by addition of copper (II) oxide (CuO hereafter) nanoparticles. CuO nanoparticles provided two distinctive properties to existing nanofibers. Firstly, nanofibers surface area was significantly increased, and secondly copper (II) oxide itself is hydrophilic material which imparted hydrophilicity to base polymer. Polyacrylonitrile, crosslinked Polyvinyl Alcohol, and PICT were selected as super hydrophobic polymeric nanofibers. Copper II oxide nanoparticles (same concentration) were added in all polymer solution and electrospun. Surface, morphological, and hydrophilic properties were characterized and it was concluded that copper II oxide is suitable for transforming hydrophobic nanofibers to super hydrophilic nanofibers. Water holding capacity (WHC) was also improved for all prepared nanofiber mats. WHC for PVA/CuO, PAN/CuO, and PICT/CuO were recorded an average of 23 g/g, 21 g/g, and 18 g/g respectively. Combining all useful results from possible characterization of nanofiber mats, it is expected that CuO nanoparticles loaded nanofibers will have potential application as antibacterial, sustainable, and stable replacement of hygiene products.     

Studies of the effects of copper, copper(II) oxide and copper(II) chloride on the thermal degradation of poly(vinyl chloride)

Investigations of the pyrolysis of poly(vinyl chloride) (PVC) in the presence of copper metal (Cu), copper(II) oxide (CuO) and copper(II) chloride (CuCl₂) are of potential importance because of the likelihood of the formation of these copper compounds during the thermal degradation of PVC-coated copper wires, a step in the recovery of copper from waste. The presence of Cu, CuO and CuCl₂ (i) retards the thermal degradation of PVC in air and in nitrogen and (ii) decreases the percentages of volatile products produced at both stages of the decomposition. These effects are greatest for PVC-CuO. The presence of copper, CuO or CuCl₂ in PVC has a major effect on the nature of the gaseous emissions of the thermal decomposition in air and in nitrogen. The concentrations of total chlorine, aliphatic hydrocarbons, aromatic hydrocarbons, chlorinated hydrocarbons and soot particulates are all affected relative to an equivalent amount of PVC. These changes are greatest for the PVC-CuO system for which total chlorine emissions in air and nitrogen are reduced by 40% in air and 20% in nitrogen, benzene emissions are reduced by greater than 90% in air and nitrogen, other aromatic and chloroaromatic emissions are reduced, and soot particulate emissions are reduced by more than 50% as the concentrations of aliphatic compounds are increased. These changes are consistent with the presence of copper or its compounds permitting more efficient combustion of the carbon content of the PVC and particularly in the case of PVC-CuO with the removal of chlorine during pyrolysis in the inorganic phase.     

Magnetic CuO nanoparticles supported on graphene oxide as an efficient catalyst for A3-coupling synthesis of propargylamines

Magnetically separable CuO nanoparticles supported on graphene oxide (Fe₃O₄ NPs/GO-CuO NPs) is synthesized and characterized for the preparation of propargylamines in EtOH, at 90℃. Fe₃O₄ NPs/GO-CuO NPs is found to be an efficient catalyst for the A³-coupling of aldehydes, amines, and alkynes through C-H activation. Both aromatic and aliphatic aldehydes and alkynes are combined with secondary amines to provide a wide range of propargylamines in moderate to excellent yields.     

Electrometric monitoring of water adsorption by porous glass modified with copper(II) oxide

Modification of porous glass with copper(II) oxide with planar structure does not change the run of the water-adsorption isotherm, whereas in the case when nanoparticles are formed from the supported oxide, a cluster-type adsorption mechanism is operative when a relative pressure p/p ₀ > 0.5 is reached. These specific features are reflected in the different dependences of the electrical resistance of the samples on humidity. It was shown that a porous glass with distributed copper(II)oxide planar layer can be used as a sensitive element of a resistive humidity sensor.     

Thermal characteristics of ammonium nitrate, carbon, and copper(II) oxide mixtures

Ammonium nitrate (AN) has been extensively used as an oxidizer in energetic compositions, and is a promising compound as a propellant and gas generator. It is well-known that metal oxides help to address some of the disadvantages of AN, such as low stability and a low burning rate in these applications. In order to investigate the effects of copper(II) oxide (CuO) on the thermal decompostion of AN mixtures, the thermal characteristics of AN, carbon, and CuO mixtures were measured using simultaneous differential scanning calorimetry and thermogravimetry–differential thermal analysis connected with infrared spectroscopy and mass spectrometry. As a combustible material, activated carbon (AC), and carbon black (CB) were used in this study. In the TG–DTA results for AN/AC/CuO and AN/CB/CuO mixtures in an open cell, an exotherm was observed at approximately 210 and 230 °C, respectively. In addition, the IR and mass spectra of the gases produced from the AN/AC/CuO and AN/CB/CuO mixtures indicated the presence of CO₂. Notably, the effect of CuO addition on the oxidation of the AN/AC/CuO mixture was different from that on the AN/CB/CuO mixture; the oxidation of AC shifted to a lower temperature, while the oxidation of CB shifted to a higher temperature. These results suggest that the effect of CuO on the oxidation of different types of carbon depends on the chemical reactivity of the carbon, which is derived from its physical properties.     

Stabilisation of water-soluble platinum nanoparticles by phosphonic acid derivatives

Sodium 2-(diphenylphosphino)ethyl phosphonate (1) was investigated as a stabilising agent for platinum nanoparticles (Pt-NPs) in aqueous solution. This phosphino phosphonate is known to stabilise rhodium nanoparticles (NPs) in water. Here we report that in the case of Pt-NPs this ligand is indirectly involved in the stabilisation mechanism and the actual stabilisation agent is the platinum complex Na(2)[Pt(1)(2)] (2). The reduction of platinum(II) salts in the presence of the phosphonates 1, 2, sodium 2-(diphenylphosphoryl)ethyl phosphonate (3) and 3,3,3-triphenylpropyl phosphonate (4) leads to stable platinum NPs with a remarkably narrow particle size distribution. These platinum NPs show high catalytic activity in the hydrogenation of 1-hexene and 1-chloro-3-nitrobenzene under biphasic as well as heterogeneous (supported on charcoal) conditions. The activity of the supported NPs was 30 times higher than the commercially available catalyst Pt(0) EnCat?. Furthermore, the single-crystal X-ray structures of (1)(MeOH)(2)(H(2)O)(2), (3)(H(2)O)(4), and (4)(2)(H(2)O)(17) have been determined.     

A General One-Pot Methodology for the Preparation of Mono- and Bimetallic Nanoparticles Supported on Carbon Nanotubes: Application in the Semi-hydrogenation of Alkynes and Acetylene

A facile and straightforward methodology for the preparation of monometallic (copper and palladium) and bimetallic nanocatalysts (NiCu and PdCu) stabilized by a N-heterocyclic carbene ligand is reported. Both colloidal and supported nanoparticles (NPs) on carbon nanotubes (CNTs) were prepared in a one-pot synthesis with outstanding control on their size, morphology and composition. These catalysts were evaluated in the selective hydrogenation of alkynes and alkynols. PdCu/CNTs revealed an efficient catalytic system providing high selectivity in the hydrogenation of terminal and internal alkynes. Moreover, this catalyst was tested in the semi-hydrogenation of acetylene in industrially relevant acetylene/ethylene-rich model gas feeds and showed excellent stability even after 40 h of reaction.     

A water soluble nanostructured platinum (0) metal catalyst from platinum carbonyl molecular clusters: Synthesis, characterization and application in the selective hydrogenations of olefins, ketones and aldehydes

High nuclearity platinum carbonyl cluster anions (Chini's clusters) have been used as precursors to prepare a platinum nanocatalyst. The ionic polyelectrolyte poly(diallyldimethylammonium chloride) has been used as the support material for anchoring [Pt₃₀(CO)₆₀]²⁻ via ion-pairing and subsequent stabilization of the nanoparticles. The polymer-supported material has been studied by spectroscopy (NIR, ¹³C NMR, and IR) and TEM before and after its use as a water soluble hydrogenation catalyst. The nanocatalyst is found to be effective for the chemoselective hydrogenation of olefinic, aldehydic and ketonic double bonds. For most of the substrates isolation of the product and reuse of the catalyst are extremely easy due to the automatic phase separation of the products from the catalyst. The spectral features of the fresh catalyst show retention of the carbonyl ligands and molecular identity of the parent cluster, but after use the carbonyl ligands appear to be lost. TEM of the supported material before and after use as a catalyst shows the presence of platinum nanoparticles with majority (≥70%) of the particles in the range of 2–6 nm. Smaller particles are dominant in the used catalyst and this observation is rationalized on the basis of the known reactivity of Chini's clusters with dihydrogen.     

Characterization and Activity of Cu‐MnOx/γ‐Al2O3 Catalyst for Hydrogenation of Carbon Dioxide

The effect of manganese on the dispersion, reduction behavior and active states of surface of supported copper oxide catalysts have been investigated by XRD, temperature‐programmed reduction and XPS. The activity of methanol synthesis from CO₂/H₂ was also investigated. The catalytic activity over CuO‐MnO_x/γ‐Al₂O₃ catalyst for CO₂ hydrogenation is higher than that of CuO/γ‐Al₂O₃. The adding of manganese is beneficial in enhancing the dispersion of the supported copper oxide and make the TPR peak of the CuO‐MnK_x/γ‐Al₂O₃ catalyst different from the individual supported copper and manganese oxide catalysts, which indicates that there exists strong interaction between the copper and manganese oxide. For the CuO/γ‐Al₂O₃ catalyst there are two reducible copper oxide species; α and β peaks are attributed to the reduction of highly dispersed copper oxide species and bulk CuO species, respectively. For the CuO‐MnO_x/γ‐Al₂O₃ catalyst, four reduction peaks are observed, α peak is attributed to the dispersed copper oxide species; β peak is ascribed to the bulk CuO; γ peak is attributed to the reduction of high dispersed CuO interacting with manganese; δ peak may be the reduction of the manganese oxide interacting with copper oxide. XPS results show that Cu⁺ mostly existed on the working surface of the Cu‐Mn/γ‐Al₂O₃ catalysts. The activity was promoted by Cu with positive charge which was formed by means of long path exchange function between Cu? O? Mn. These results indicate that there is synergistic interaction between the copper and manganese oxide, which is responsible for the high activity of CO₂ hydrogenation.     

Regiospecific hydrogenation of quinolines and indoles in the heterocyclic ring

Quinolines, indoles, acridine, and carbazole were hydrogenated using a large variety of heterogeneous catalysts in hydrocarbon solvents in an effort to achieve selective hydrogenation of the heterocyclic ring. When quinolines were hydrogenated using supported platinum, palladium, rhodium, ruthenium, or nickel metal catalysts in the presence of hydrogen sulfide, carbon disulfide, or carbon monoxide, there was exclusive hydrogenation of the heterocyclic ring to give only 1,2,3,4-tetrahydroquinolines. Use of iridium, rhenium, molybdenum(VI) oxide, tungsten(VI) oxide, chromium(III) oxide, iron(III) oxide, cobalt(II) oxide-molybdenum(VI) oxide, or copper chromite catalysts also caused exclusive hydrogenation of the heterocyclic ring even without addition of sulfur Compounds or carbon monoxide. Hydrogenation of indoles using platinum, rhenium, or, in some cases, nickel catalysts (with or without sulfur Compounds) occurred exclusively in the heterocyclic ring to give indolines, but conversions were affected by indole-indoline equilibria.     

Sonochemical synthesis of a novel nanorod diaqua(pyridine-2,6-dicarboxylato)copper(II) 3-D supramolecular network: new precursor to prepare pure phase nanosized copper(II) oxide

A nanosized copper(II) supramolecular compound, [Cu(dipic)(H₂O)₂] _n (1) [dipic?=?2,6-pyridinedicarboxylate], has been synthesized by sonochemical method and characterized by elemental analysis, scanning electron microscopy, X-ray powder diffraction, IR spectroscopy, TGA/DTA, and BET surface area studies. The structure of single crystalline 1 developed from nanosized 1 has been determined by X-ray crystallography and further characterized by scanning electron microscopy, TGA/DTA, and BET surface area studies. The XRD studies reveal that nanorod copper(II) supramolecular compound adopts a 3-D supramolecular network owing to extensive hydrogen-bonding and π–π stacking. Solvent effects on size and morphology of nanosized 1 have been studied. Calcination of nanosized 1 at 500°C under air yields CuO nanoparticles.     

Dispersion and reduction of copper oxide supported on WO3-modified Ce(0.5)Zr(0.5)O2 solid solution

XRD (X-ray diffraction), BET (Brunauer-Emmett-Teller), LRS (laser Raman spectra), XPS (X-ray photoelectron spectroscopy), and TPR (temperature-programmed reduction) are used to investigate the surface properties of CuO/WO3/Ce(0.5)Zr(0.5)O2 samples. The results indicate that (1) tungsten oxide can be highly dispersed on Ce(0.5)Zr(0.5)O2 (denoted as CZ hereafter) solid solution, with a dispersion capacity of about 0.8 mmol WO(3)/(100 m2 CZ), and comparatively, the supported tungsten oxide species are preferentially interacted with ceria component on the surface of CZ; (2) for CuO/WO3/CZ samples with a half-monolayer WO3 loading, i.e., xCu-0.4W-CZ series, the surface of CZ is only partially covered by the preloaded WO3) and the supported copper oxide species are dispersed on the remaining surface vacant sites on CZ as well as on top of the preloaded tungsten oxide, while for the samples preloaded with a full-monolayer WO3, i.e., xCu-0.8W-CZ series, only dispersed on the top of the preloaded tungsten oxide monolayer; (3) the effect of the loading amount of WO3 on the reduction property of Cu2+ ions in a series of CuO/WO3/CZ samples has been observed and tentatively attributed to the formation of WO3 monolayer on CZ and the different coordination environments of the dispersed Cu2+ ions are discussed on the basis of the consideration of the incorporation model proposed previously (Chen, Y.; Zhang, L. Catal. Lett. 1992, 12, 51).