Copper catalytic properties

The effect that the presence of hydrogen in the lattice of nickel or nickel-copper alloys has on catalytic properties is much more difficult to trace in the literature than is the case with palladium and its alloys. Several factors contribute to this ... 

Bimetallic nanoparticles, either as alloys or as core-shell structures, exhibit unique electronic, optical and catalytic properties compared to pure metallic nanopartides [24]. Cu-Ag alloy nanoparticles were obtained through the simultaneous reduction of copper and silver ions again in aqueous starch matrix. The optical properties of these alloy nanopartides vary with their composition, which is seen from the digital photographs in Fig. 8. The formation of alloy was confirmed by single SP maxima which varied depending on the composition of the alloy. 

Ruthenium-copper and osmium-copper clusters (21) are of particular interest because the components are immiscible in the bulk (32). Studies of the chemisorption and catalytic properties of the clusters suggested a structure in which the copper was present on the surface of the ruthenium or osmium (23,24). The clusters were dispersed on a silica carrier (21). They were prepared by wetting the silica with an aqueous solution of ruthenium and copper, or osmium and copper, salts. After a drying step, the metal salts on the silica were reduced to form the bimetallic clusters. The reduction was accomplished by heating the material in a stream of hydrogen. 

The results of the EXAFS studies on osmium-copper clusters lead to conclusions similar to those derived for ruthenium-copper clusters. That is, an osmium-copper cluster Is viewed as a central core of osmium atoms with the copper present at the surface. The results of the EXAFS investigations have provided excellent support for the conclusions deduced earlier (21,23,24) from studies of the chemisorption and catalytic properties of the clusters. Although copper is immiscible with both ruthenium and osmium in the bulk, it exhibits significant interaction with either metal at an interface. 

Copper is a component of several enzymes that have quite different catalytic properties ... 

In the present study, we report the synthesis, characterisation and catalytic properties (in selective oxidation reactions) of copper acetate, copper tetradecachlorophthalocyanine and copper tetranitrophthalocyanine encapsulated in molecular sieves Na-X, Na-Y, MCM-22 and VPI-5. Both molecular oxygen and aqueous HjOj have been used as the oxidants. The... 

Silver and gold, which are corrosion resistant in many solutions, are rather efficient catalysts for the cathodic reduction of oxygen and certain other reactions. Some sp-metals (mercury, tin, zinc) exhibit interesting catalytic properties for the cathodic reduction of CO2. Copper might be a very interesting material for a number of electrochemical reactions, but so far has not been examined thoroughly. 

Marquez-Alvare C, Rodriguez-Ramos I, Guerrero-Ruiz A. Removal of NO over carbon supported copper catalysts II. Evaluation of catalytic properties under different reaction conditions, Carbon 1996, 34,1509-1514. 

S. Chavan, D.Srinivas, and R. Ratnasamy, Structure and catalytic properties of dimeric copper(II) acetato complexes encapsulated in zeolite-Y, J. Catal. 192, 286-295 (2000). 

Nickel(II) ion and complexes are often included in the study of the catalytic properties of metal ions (Chap. 6). Nickel(II) (and copper(II)) have a marked ability to promote ionization from coordinated amide and peptide likages (Sec. 6.3.2). Nickel(II) can also help assemble reactants in a specific fashion to produce macrocycles. 

The catalytic properties of copper catalysts for CSRM are significantly different from those of other transition metals. Several investigations have been performed on the behavior of group 9-10 transition metals in the conversion of alcohols [120-122]. 

Two types of catalysts have been proposed for the CPOM reaction copper and palladium. The catalytic properties of these materials show significant discrepancies with respect to by-product formation and the effect of oxygen partial pressure. The Cu-based catalysts display high selectivity for the CPOM reaction whereas for the Pd-based catalysts CO formation is significant. 

The group 10 metals, such as palladium and platinum, are active for the conversion of methanol. However, they are much less selective than the copper-based catalysts, yielding primarily the decomposition products [123,124,133]. This catalytic property makes them less feasible for fuel cell applications. The only exception found is for Pd/ZnO, which showed selectivity close to that of a copper catalyst [105, 121]. 

The catalytic properties of a copper ion-exchanged ZSM-5 zeolite (Cu-ZSM-5) can be compared with others. 

The catalytic properties of copper during polyols conversion in aqueous phase may be drastically modified by some additives. Metals having a standard oxido-reduction potential higher than that of copper (Ir, Rh, Ru, Pd, Pt, Au) can be deposited on it by oxido-reduction reaction. The first atoms of second metal deposited exchange with hydroxylated... 

Now the influence of water or ammonia on copper catalysts is being investigated. Previously A. BAIKER and coll, have shown that ammonia could modify the catalytic properties of copper catalysts used in the amination of alcohols (9). These authors noticed the formation of copper nitride after NH3 exposure at a temperature of about 300°C which is the reaction temperature of our study. The first results that we obtained in our study showed that both H2O and NH3 decrease significantly the copper dispersion in unpromoted catalysts and that this modification is less significant when Ca or Mn are added to the Cu-Cr catalyst. We are now studying what are the superfical modifications consecutive to the addition of promoters or/and water and ammonia. 

Organic Catalysts. V. Specific Catalytic Properties of Copper-Iron Polyphthalo-... 

Originally, the effect of charge state of nanostructures on their catalytic activity was recognized from analysis of the experimental data on the catalytic properties of metallic nanoparticles immobilized in the matrix of a poly-paraxylylene polymer [13-15,24]. It was found that the dependence of the catalytic activity (and, in some cases, of the selectivity) of copper, palladium, and iron nanoparticles on the metal content of these structures has a maximum. This maximum exists not only for the specific (related to unit weight) activity, but also for the absolute activity. More specifically, for copper and... 

A number of copper) I) and copper) 11) complexes with [22]py4pz and [22]pr4pz have been isolated and structurally characterized [47—49]. Their structural and catalytic properties, as well as studies on the mechanism of the catalytic oxidation of catechol performed by some of these compounds, are discussed below. 

The choice of solvent has had little, if any, influence on the majority of Diels-Alder reactions.210,211 Although the addition of a Lewis acid might be expected to show more solvent dependence, generally there appears to be little effect on asymmetric induction.118129 However, a dramatic effect of solvent polarity has been observed for chiral metallocene triflate complexes.212 The use of polar solvents, such as nitromethane and nitropropane, leads to a significant improvement in the catalytic properties of a copper Lewis acid complex in the hetero Diels-Alder reaction of glyoxylate esters with dienes.213... 

The preparation of well-defined single-crystal surfaces of copper oxides in UHV or of well-sintered powders, starting from polycrystalline materials, is difficult. Consequently, structure-catalytic property correlations remain to be established. 

The early conflicting reports on the activity of pure copper metal could not be reconciled without the simultaneous or concurrent measurements of activity, surface area, and surface composition. Moreover, it became evident that it is important to use unsupported copper as the reference material to avoid support-metal interactions that may influence the catalytic properties of the latter. 

Figure 5.7 Three-dimensional drawing of the experimental system used to assess the catalytic properties of the amorphous iron silicate smokes. The (smoke) catalyst is contained in the bottom of a quartz finger (attached to a 2L Pyrex bulb) that can be heated to a controlled temperature. A Pyrex tube brings reactive gas to the bottom of the finger. The gas then passes through the catalyst into the upper reservoir of the bulb and flows through a copper tube at room temperature to a glass-walled observation cell (with ZnSe windows) in an P iiR spectrometer. From there, a closed-cycle metal bellows pump returns the sample via a second 2L bulb and the Pyrex tube to the bottom of the catalyst finger to start the cycle over again (Hill and Nuth 2003).

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