Reduction of copper

By the reduction of copper(II) chloride or a mixed solution of copper(II) sulphate and common salt by sulphur dioxide. 

Properties of T2O. Some important physical properties of T2O are Hsted in Table 2. Tritium oxide [14940-65-9] can be prepared by catalytic oxidation of T2 or by reduction of copper oxide using tritium gas. T2O, even of low (2—19% T) isotopic abundance, undergoes radiation decomposition to form HT and O2. Decomposition continues, even at 77 K, when the water is fro2en. Pure tritiated water irradiates itself at the rate of 10 MGy/d (10 rad/d). A stationary concentration of tritium peroxide, T2O2, is always present (9). AH of these factors must be taken into account in evaluating the physical constants of a particular sample of T2O. 

In practice vapours of the hydrocarbon halide, e.g. methyl chloride, are passed through a heated mixture of the silicon and copper in a reaction tube at a temperature favourable for obtaining the optimum yield of the dichlorosilane, usually 250-280°C. The catalyst not only improves the reactivity and yield but also makes the reaction more reproducible. Presintering of the copper and silicon or alternatively deposition of copper on to the silicon grains by reduction of copper (I) chloride is more effective than using a simple mixture of the two elements. The copper appears to function by forming unstable copper methyl, CUCH3, on reaction with the methyl chloride. The copper methyl then decomposes into free methyl radicals which react with the silicon. 

Aldehydes are formed by the reduction of the ester of the corresponding acid to the alcohol, and then oxidising the alcohol with heated copper as catalyst. It is well known that when primary alcohols in the gaseous state are passed over finely-divided copper dust, obtained by reduction of copper oxide, at 250° to 400°, they yield hydrogen, and aldehydes or ketones respectively. 

It also is common to observe reddish stains of elemental copper in the same area (as a result of the reduction of copper oxides by hydrogen generated during the steel corrosion process). 

Copper (Cu) is deposited in boilers either by direct exchange with iron or by the hydrogen reduction of copper oxide during the corrosion of steel. 

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. 

The co-reduction of copper and selenium is considered as an exception to Kroger s theory. Current-potential curves in the literature show that deposition of copper is rather compulsory to make the deposition of selenium possible. In fact, although the standard potential for Se(IV) reduction is more positive than that of copper (0.741 and 0.340 V vs. SHE, for selenous acid and cupric ion, respectively), it turns out that Se(IV) alone is reduced at more negative potentials than Cu(II). In the presence of copper, the order is reversed. 

Fig. 14.16 Nanobell formation through catalytic reduction of copper from loaded copper salt.

Fig. 4. Current density for the reduction of copper and the double layer capacity of a copper electrode in an acidic copper sulfate solution vs. applied overpotential (adapted from ref. 50).

Figure 6.20 Quick EXAFS and XRD measurements recorded during the temperature programmed reduction of copper in a Cu/Zn0/Al203 methanol synthesis catalyst. The disappearance and appearance of peaks with increasing temperature in the series of EXAFS spectra corresponds to the conversion of oxidic to metallic copper. The intensity of the relatively sharp peak around 9040 eV, indicative of Cu metal, clearly illustrates the kinetics of the reduction process, as does the intensity of the (111) reflection of Cu metal in the XRD spectra (adapted from Clausen 44J).

Figure 6.20 shows an example in which QEXAFS has been used in combination with XRD to study the temperature programmed reduction of copper oxide in a Cu/ZnO/Al203 catalyst for the synthesis of methanol [43,44]. Reduction to copper metal takes place in a narrow temperature window of 430-440 K, and is clearly revealed by both the EXAFS pattern and the appearance of the (111) reflection of metallic copper in the XRD spectra. Note that the QEXAFS detects the metallic copper at a slightly lower temperature than the XRD does, indicating that the first copper metal particles that form are too small to be detected by XRD, which requires a certain extent of long range order [43,44],... 

There have been many recent studies in support of this mechanistic approach. Stepwise reductive formation of Ag3+ and Ag4+ clusters has been followed using spectroscopic methods by Henglein [33], Reduction of copper (II) to colloidal Cu protected by cationic surfactants (NR4+) through the intermediate Cu+ prior to nucleation of the particles [36] as monitored by in situ x-ray absorption spectroscopy is another example. The seed-mediated synthesis also serves as evidence in support of this mechanism [38-41],... 

Metal ion reduction can also occur during surface studies. One of the best documented examples is that of the reduction of copper(II) to copper(I), a process that has been reviewed extensively in the research literature (11). Certain copper(II) minerals, such as CuO (tenorite), are quite susceptible to photoreduction (11), and care must be taken in conducting surface studies on them. 

Write the half-reaction for (a) the oxidation of zinc (b) the reduction of copper. 

Commercial copper bromide or its dimethyl sulfide complex contains impurities that are deleterious to the reaction. Therefore, the copper(l) bromide-dimethyl sulfide complex is prepared according to the method of House from copper(l) bromide generated by reduction of copper(ll) bromide (Aldrich Chemical Company, Inc., 99%) with sodium sulfite. Best results ctre obtained using copper(l) bromide-dimethyl sulfide complex freshly recrystallized according to the following procedure. 

Copper(I) chloride is prepared by reduction of copper(ll) chloride in solution ... 

Reduction of copper(II) hydroxide, Cu(OH)2 with sulfur dioxide, glucose, or another reducing agent. 

In each compartment of the electrochemical cell a half reaction occurs. The two half reactions result in an overall reaction that generates a flow of electrons or current. In one cell compartment, zinc is oxidized according to the reaction Zn Zn + 2e . The reduction of copper takes place in the other cell s compartment Cu +,, + 2e Cu,.. Notice that these reactions are the same ones that take place... 

Hydroborate Reduction. Lithium or sodium tetrahydroborate and diborane can be used for reduction of metal ions, especially light transition metal ions, to produce colloidal metals. For example, colloidal copper protected by polymer was prepared by reduction of copper(II) sulfate by a large excess of sodium tetrahydroborate in the presence of PVP or other polymers (12). A similar procedure for nickel(III) chloride produced nickel boride, not zero-valence nickel metal particles. 

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