Copper oxide, reaction with carbon monoxide

Reaction with carbon monoxide using copper/zinc oxide catalyst yields methanol ... 

Most investigations were concerned with the oxidation reaction of carbon monoxide on manganese peroxide, copper oxide, and some other oxides. The pioneer investigators (46, 47) came to the conclusion about the participation of oxygen of oxide catalysts in this reaction. Contrary... 

Other reported syntheses include the Reimer-Tiemann reaction, in which carbon tetrachloride is condensed with phenol in the presence of potassium hydroxide. A mixture of the ortho- and para-isomers is obtained the para-isomer predominates. -Hydroxybenzoic acid can be synthesized from phenol, carbon monoxide, and an alkali carbonate (52). It can also be obtained by heating alkali salts of -cresol at high temperatures (260—270°C) over metallic oxides, eg, lead dioxide, manganese dioxide, iron oxide, or copper oxide, or with mixed alkali and a copper catalyst (53). Heating potassium salicylate at 240°C for 1—1.5 h results in a 70—80% yield of -hydroxybenzoic acid (54). When the dipotassium salt of salicylic acid is heated in an atmosphere of carbon dioxide, an almost complete conversion to -hydroxybenzoic acid results. They>-aminobenzoic acid can be converted to the diazo acid with nitrous acid followed by hydrolysis. Finally, the sulfo- and halogenobenzoic acids can be fused with alkali. 

Structural sensitivity of the catalytic reactions is one of the most important problems in heterogeneous catalysis [1,2]. It has been rather thoroughly studied for metals, while for oxides, especially for dispersed ones, situation is far less clear due to inherent complexity of studies of their bulk and surface atomic structure. In last years, successful development of such methods as HREM and STM along with the infrared spectroscopy of test molecules has formed a sound bases for elucidating this problem in the case of oxides. In the work presented, the results of the systematic studies of the bulk/surface defect structure of the oxides of copper, iron, cobalt, chromium, manganese as related to structural sensitivity of the reactions of carbon monoxide and hydrocarbons oxidation are considered. 

A slurry phase concurrent synthesis of methanol using a potassium meth-oxide/copper chromite mixed catalyst has been developed. This process operates under relatively mild conditions such as temperatures of 100-180°C and pressures of 30-65 atm. The reaction pathway involves a homogeneous carbonylation of methanol to methyl formate followed by the heterogeneous hydrogenolysis of methyl formate to two molecules of methanol, the net result being the reaction of hydrogen with carbon monoxide to give methanol via methyl formate ... 

The high initial activity of the fresh alumocopperchromium catalyst in the oxidation of carbon monoxide is due to Cufll) cations within the copper chromite and in CuO surface clusters (Fig 1) Centres with chromium cations in the highest oxidation degrees are bound to the support surface and solid solutions of the aluminate type. These contain cations of bivalent copper and are less active in the CO oxidation reaction. It was shown by IRS and XPS that during the use of this catalyst in CHG, as well as during the unsteady-state oxidation reaction/ a partial reduction of Cu(II) to Cu I occurs (Fig, 2), which leads to a decrease in catalyst activity in the oxidation of the carbon monoxide. In the fresh alumomagnesiumchromium catalyst, the activity for carbon monoxide is determined by the centres containing chromium cations in... 

As many carbonate complexes are synthesized usually in aqueous solution under fairly alkaline conditions, the possibility of contamination by hydroxy species is often a problem. To circumvent this, the use of bicarbonate ion (via saturation of sodium carbonate solution with COj) rather than the carbonate ion can often avoid the precipitation of these contaminants. Many other synthetic methods use carbon dioxide as their starting point. Transition metal hydroxo complexes are, in general, capable of reacting with CO2 to produce the corresponding carbonate complex. The rate of CO2 uptake, which depends upon the nucleophilicity of the OH entity, proceeds by a mechanism that can be regarded as hydroxide addition across the unsaturated C02. There are few non-aqueous routes to carbonate complexes but one reaction (3), illustrative of a synthetic pathway of great potential, is that used to prepare platinum and copper complexes. Ruthenium and osmium carbonate complexes result from the oxidation of coordinated carbon monoxide by dioxygen insertion (4). ... 

CuCl) A white solid, insoluble in water, prepared by heating copper(II) chloride in concentrated hydrochloric acid with excess copper turnings. When the solution is colorless, it is poured into air-free water (or water containing sulfur(IV) oxide) and a white precipitate of copper(I) chloride is obtained. On exposure to air this precipitate turns green due to the formation of basic copper(II) chloride. Copper(I) chloride absorbs carbon monoxide gas. It is used as a catalyst in the rubber industry. The chloride is essentially covalent in structure. In the vapor phase both dimeric and trimeric forms exist. It is used in organic chemistry in the Sandmeyer reactions. 

The electrophilic substitution is the most characteristic reaction for these classes of compounds. Compound (21) undergoes standard electrophilic aromatic substitution reactions. Thus it forms the 6-bromo compound (58) with A7-bromosuccinimide and 6,7-dibromo compound (72) with the excess of the same reagent. It also forms the 6-nitro compound (67) with copper(II) nitrate trihydrate and 6,7-dinitro compound (68) with excess of nitronium tetrafluoroborate. The bis(trifluoro-acetoxy)thallium derivative (73) was formed from trithiadiazepine (21) and thallium(III) trifluoro-acetate in refluxing acetonitrile. Without isolation, (73) was directly converted into the pale yellow 6-iodo compound (74) with aqueous potassium iodide, into the 6-cyano compound (75) with copper(I) cyanide, and into methyl trithiadiazepine-6-carboxylate (76) with carbon monoxide and methanol in the presence of palladium chloride, lithium chloride, and magnesium oxide. Compound (21) is acetylated in the presence of trifluoromethanesulfonic acid (Scheme 7) <85CC396,87JCS(P1)217, 91JCS(P1)2945>. 

Co2(CO)g] is prepared by the reaction of carbon monoxide with dispersed metal or with its compounds (halides, carboxylates, etc.) in the presence of copper. At atomospheric pressure in aqueous solutions containing CN ions, Co(II) salts from [Co(CO)4] up to 100% yield if the CN /Co(II) ratio is from 1 to 2. Oxidation of [Co(CO)4]- gives [Co2(CO)8]. 

Colloidal copper has been prepared by an organometallic route through the reaction of (cydopentadienyl)(tert-BuNQCu with carbon monoxide in the presence of either PVP in methylene chloride or poly(dimethylphenylene oxide), PPO, in anisole. The PPO stabilized sol contains zerovalent copper particles of 4.0 nm diameter, while the PVP stabilized colloid contains larger particles with a relatively broad size distribution. [115]... 

Studies of the mammalian cytochromes of the a type have raised at least three problems (1) the identity of cytochromes a and (2) the presence of copper in the cytochrome molecule and (3) the mechanism of oxygen reduction. Again, the preferred theory postulates the existence of two different cytochromes, but this concept is not accepted by all biochemists, and some still believe in a Unitarian theory which postulates that cytochromes a and are actually a single molecule. For example, it was demonstrated that cytochrome a, provided it is in the ferrous form, can also react with carbon monoxide furthermore, the presence of cytochrome c renders cytochrome a autoxi-dizable. Finally, the oxidation of reduced cytochrome Cl requires cytochromes a and c, and the rate of the reaction is optimal if the ratio of a/c is equal to 1. 

Saturated hydrocarbons, including branched and unbranched chain alkanes as well as cycloalkanes, react with carbon monoxide in the presence of copper(I) oxide in HSOsF-SbFs to afford ter tiary and secondary carboxylic adds in high yield (eq 20). The reaction proceeds at 0 °C under 1 atm CO. In some cases the reaction involves cleavage of C C bonds and isomerization of the intermediate carbocatlons. 

The top reaction, between carbon monoxide and hydrogen to form methanol, is the basis for all conunercial methanol synthesis plants, and is desirable. This reaction is carried out using a heterogeneous catalyst containing copper and zinc oxide, and is quite reversible at conunercial reaction conditions. The bottom, undesirable reaction is referred to as methanation. It is relatively slow with today s methanol synthesis processes and catalysts. However, methanation can be important if die catalyst becomes contaminated with elements such as nickel and iron, which catalyze the methanation reaction. 

The palladium(II)-catalyzed olefin carbonylation reaction was first reported more than 30 years ago in studies by Stille and co-workers and James et al. The reaction of carbon monoxide with cis- and tra 5-but-2-ene in methanol in the presence of palladium(II)-chloride and copper(II)-chloride yielded threo- and eryt/zro-3-methoxy-2-methyl-butanoate, respectively. The transformation that was based on the well-known Wacker process for oxidation of ethylene into acetaldehyde in water " is now broadly defined as the Pd(II)-catalyzed oxycarbonylation of the unsaturated carbon-carbon bonds. This domino reaction includes oxypalladation of alkenes, migratory insertion of carbon monoxide, and alkoxylation. Since the development of this process, several transformations mediated by palladium(II) compounds have been described. The direct oxidative bisfunctionalization of alkenes represents a powerful transformation in the field of chemical synthesis. Palladium(II)-promoted carbonylation of alkenes in the presence of water/alcohol may lead to alkyl carboxylic acids (hydrocarboxylation), diesters [bis(aIkoxycarbonyla-tion)], (3-alkoxy carboxylic acids (alkoxy-carboxylation), or (3-alkoxy esters (alkoxy-carbonylation or alkoxy-alkoxy-carbonylation). Particularly attractive features of these multitransformation processes include the following ... 

Because the synthesis reactions are exothermic with a net decrease in molar volume, equiUbrium conversions of the carbon oxides to methanol by reactions 1 and 2 are favored by high pressure and low temperature, as shown for the indicated reformed natural gas composition in Figure 1. The mechanism of methanol synthesis on the copper—zinc—alumina catalyst was elucidated as recentiy as 1990 (7). For a pure H2—CO mixture, carbon monoxide is adsorbed on the copper surface where it is hydrogenated to methanol. When CO2 is added to the reacting mixture, the copper surface becomes partially covered by adsorbed oxygen by the reaction C02 CO + O (ads). This results in a change in mechanism where CO reacts with the adsorbed oxygen to form CO2, which becomes the primary source of carbon for methanol. 

Oxidation. Carbon monoxide can be oxidized without a catalyst or at a controlled rate with a catalyst (eq. 4) (26). Carbon monoxide oxidation proceeds explosively if the gases are mixed stoichiometticaHy and then ignited. Surface burning will continue at temperatures above 1173 K, but the reaction is slow below 923 K without a catalyst. HopcaUte, a mixture of manganese and copper oxides, catalyzes carbon monoxide oxidation at room temperature it was used in gas masks during World War I to destroy low levels of carbon monoxide. Catalysts prepared from platinum and palladium are particularly effective for carbon monoxide oxidation at 323 K and at space velocities of 50 to 10, 000 h . Such catalysts are used in catalytic converters on automobiles (27) (see Exhaust CONTHOL, automotive). 

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