Cu/Zn oxides

Methanol is currently the largest volume carbonylation product and is made by passing syngas (CO -f H2 Section 4.1.2) over a solid Cu-Zn oxide catalyst. Most of the other carbonylation reactions are catalyzed by the later c -block transition metals, often under homogeneous conditions in solution. This is despite a public perception that the use of heavy metals (such as the complexes of the 4d and 5d transition metals) is generally undesirable. However their extremely effective catalytic properties now make their use mandatory in many... 

Electroreduction of CO2 using Cu/Zn oxides loaded gas diffusion electrodes... 

Table 5 Summary of CO2 electrorcduction results for 200 C passed at Cu/Zn oxides loaded gas diffusion electrodes in 0.5 M KH2PO4 aq. soln. at 25°C.

In order to produce ethanol by COj hydrogenation, the catalyst should have two functions C-C bond formation and C-0 bond partial preservation. In the case of the CO/Hj feed gas system, the former is industrially performed in Fischer-Tropsch synthesis, while the latter in methanol synthesis. K/Fe oxides catalyst, being effective in Fischer-Tropsch synthesis, was found to produce C-C bond in COj hydrogenation. It converted COj into CO, alcohols, and hydrocarbons. Cu-Zn oxides catalyst, practically used in methanol synthesis from CO/CO2/H2 mixture, was found unable to produce C-C bond it converted CO, to CO and methanol without any other detected compounds. 

Preparation of binary M/Mn (M = Co, Cu, Zn) oxide eatalysts by thermal degradation of heterobimetallie eomplexes... 

S. Ikeda, S. Shiozaki, J. Susuki, K. Ito and H. Noda, Electroreduction of CO2 using Cu/Zn oxides loaded gas diffusion electrodes. In T. Inui, M. Anpo, K. Izui, S. Yanagida and T. Yamaguchi (eds.). Advances in Chemicd Conversions for Mitigating Carbon Dioxide, Series Studies in Surface Science and Catalysis, Vol. 114,1998, 225-230. 

The conversion of CO to CO2 can be conducted in two different ways. In the first, gases leaving the gas scmbber are heated to 260°C and passed over a cobalt—molybdenum catalyst. These catalysts typically contain 3—4% cobalt(II) oxide [1307-96-6] CoO 13—15% molybdenum oxide [1313-27-5] MoO and 76—80% alumina, JSifDy and are offered as 3-mm extmsions, SV about 1000 h . On these catalysts any COS and CS2 are converted to H2S. Operating temperatures are 260—450°C. The gases leaving this shift converter are then scmbbed with a solvent as in the desulfurization step. After the first removal of the acid gases, a second shift step reduces the CO content in the gas to 0.25—0.4%, on a dry gas basis. The catalyst for this step is usually Cu—Zn, which may be protected by a layer of ZnO. 

Only about 10 elements, ie, Cr, Ni, Zn, Sn, In, Ag, Cd, Au, Pb, and Rh, are commercially deposited from aqueous solutions, though alloy deposition such as Cu—Zn (brass), Cu—Sn (bronze), Pb—Sn (solder), Au—Co, Sn—Ni, and Ni—Fe (permalloy) raise this number somewhat. In addition, 10—15 other elements are electrodeposited ia small-scale specialty appHcations. Typically, electrodeposited materials are crystalline, but amorphous metal alloys may also be deposited. One such amorphous alloy is Ni—Cr—P. In some cases, chemical compounds can be electrodeposited at the cathode. For example, black chrome and black molybdenum electrodeposits, both metal oxide particles ia a metallic matrix, are used for decorative purposes and as selective solar thermal absorbers (19). 

Blowing air through the hot, crude, liquid metal oxidizes traces of metals such as Fe, Cu, Zn and Pb which form an easily removable scum. Further purification is by distillation under reduced pressure. About 4000 tonnes of mercury are used annually but only half is from primary, mine production the other half being secondary production and sales from stockpiles. The main primary producer is now Spain, but several other countries, including the former Soviet Union, China and Algeria, have capacity for production. 

Traces of many metals interfere in the determination of calcium and magnesium using solochrome black indicator, e.g. Co, Ni, Cu, Zn, Hg, and Mn. Their interference can be overcome by the addition of a little hydroxylammonium chloride (which reduces some of the metals to their lower oxidation states), or also of sodium cyanide or potassium cyanide which form very stable cyanide complexes ( masking ). Iron may be rendered harmless by the addition of a little sodium sulphide. 

The major types of interferences in ASV procedures are overlapping stripping peaks caused by a similarity in the oxidation potentials (e.g., of the Pb, Tl, Cd, Sn or Bi, Cu, Sb groups), the presence of surface-active organic compounds that adsorb on tlie mercury electrode and inhibit the metal deposition, and the formation of intermetallic compounds (e.g., Cu-Zn) which affects the peak size and position. Knowledge of these interferences can allow prevention through adequate attention to key operations. 

Methanol production is carried out over a catalyst containing Cu and Zn oxide on alumina at around 300 °C and 100 atm according to Equation 6.7. It is actually thought that most of the methanol is produced from CO2 formed from reaction of CO with steam (Equation 6.8). 

Setting times and hydrolytic stability of these cements are given in Table 8.3. In some cases the speed of reaction was very high, and practical cements could not be formed from ZnO or CaO even when these oxides were deactivated by heating. All the faster-setting cements exhibited good hydrolytic stability. The stability of the complexes between divalent cations and PVPA was found by a titrametric procedure to follow the order Mg Ca < Cu Zn (Ellis Wilson, 1991). This result was... 

Patients in which oxidative damage may be an important aetiological factor cataract formation include those with Down s syndrome, since there is now evidence that they have increased indices of free-radical activity and lipid peroxidation. It has been su ested that this is due to the increased levels of Cu/Zn-SOD (carried on chromosome 21) generating increased concentrations of hydrogen peroxide (Bras etal., 1989). In the presence of superoxide radicals these produce highly reactive hydroxyl radicals. 

About 20 HTe superconducting compounds and copper oxidic systems Correlations of the Cu NQR/NMR data with the Cu( Zn) emission Mossbauer data for HTSC lattices as a tool for the determination of atomic charges... 

During preparation of an oxidising agent on a larger scale than described [1], addition of warm sodium hydroxide solution to warm ammoniacal silver nitrate with stirring caused immediate precipitation of black silver nitride which exploded [2], Similar incidents had been reported previously [3], including one where explosion appeared to be initiated by addition of Devarda s alloy (Al—Cu—Zn) [4], The explosive species separates at pH values above 12.9, only produced when alkali is added to ammoniacal silver solutions, or when silver oxide is dissolved with ammonia [5], The Sommer Market reagent mixture used to identify cellulose derivatives led to a severe explosion [6],... 

The new silazane 5 may be reacted with activated metals, organometallic compounds or simple metal amides, or may first be transformed to its lithium salt and then reacted with metal(II) chlorides [11]. In all these cases, metal derivatives of 5 are obtained with the general formula j [Mc (/BuO)Si 9N(9M, which have no further base coordinated to the metal. So far we have synthesized amides with M = Ca, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Ba, all elements in oxidation state +2. X-ray structure determinations have been performed on the calcium, manganese, iron, zinc, and barium derivatives. 

The range of reactions which have been examined is wide (248) and includes hydrogenations (256), ammonia synthesis (257), polymerizations (257), and oxidations (258). Little activity has occurred in this area during the past few years. Recent reports of the effects of sonication on heterogeneous catalysis include the liquefaction of coal by hydrogenation with Cu/Zn (259), the hydrogenation of olefins by formic acid with Pd on carbon (260), and the hydrosilation of 1-alkenes by Pt on carbon (261). 

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