Cobalt acetate, oxidations

Oxidations with Cobaltous acetate Oxidation, also partial, of methyl to carboxyl groups Phthalic acid anhydrides from phthalidcs... 

High purity acetaldehyde is desirable for oxidation. The aldehyde is diluted with solvent to moderate oxidation and to permit safer operation. In the hquid take-off process, acetaldehyde is maintained at 30—40 wt % and when a vapor product is taken, no more than 6 wt % aldehyde is in the reactor solvent. A considerable recycle stream is returned to the oxidation reactor to increase selectivity. Recycle air, chiefly nitrogen, is added to the air introducted to the reactor at 4000—4500 times the reactor volume per hour. The customary catalyst is a mixture of three parts copper acetate to one part cobalt acetate by weight. Either salt alone is less effective than the mixture. Copper acetate may be as high as 2 wt % in the reaction solvent, but cobalt acetate ought not rise above 0.5 wt %. The reaction is carried out at 45—60°C under 100—300 kPa (15—44 psi). The reaction solvent is far above the boiling point of acetaldehyde, but the reaction is so fast that Httle escapes unoxidized. This temperature helps oxygen absorption, reduces acetaldehyde losses, and inhibits anhydride hydrolysis. 

Other apphcations of sodium bromide iaclude use ia the photographic iadustry both to make light-sensitive silver bromide [7785-23-1] emulsions and to lower the solubiUty of silver bromides during the developing process use as a wood (qv) preservative in conjunction with hydrogen peroxide (14) as a cocatalyst along with cobalt acetate [917-69-1] for the partial oxidation of alkyl side chains on polystyrene polymers (15) and as a sedative, hypnotic, and anticonvulsant. The FDA has, however, indicated that sodium bromide is ineffective as an over-the-counter sleeping aid for which it has been utilized (16). 

Although an inherently more efficient process, the direct chemical oxidation of 3-methylpyridine does not have the same commercial significance as the oxidation of 2-methyl-5-ethylpyridine. Liquid-phase oxidation procedures are typically used (5). A Japanese patent describes a procedure that uses no solvent and avoids the use of acetic acid (6). In this procedure, 3-methylpyridine is combined with cobalt acetate, manganese acetate and aqueous hydrobromic acid in an autoclave. The mixture is pressurized to 101.3 kPa (100 atm) with air and allowed to react at 210°C. At a 32% conversion of the picoline, 19% of the acid was obtained. Electrochemical methods have also been described (7). 

A number of different cobalt salts have been used in the oxidation of toluene, the most common being cobalt acetate [71-48-7] cobalt naphthenate, and cobalt octoate [1588-79-0],... 

Physical and Chemical Properties. The (F)- and (Z)-isomers of cinnamaldehyde are both known. (F)-Cinnamaldehyde [14371-10-9] is generally produced commercially and its properties are given in Table 2. Cinnamaldehyde undergoes reactions that are typical of an a,P-unsaturated aromatic aldehyde. Slow oxidation to cinnamic acid is observed upon exposure to air. This process can be accelerated in the presence of transition-metal catalysts such as cobalt acetate (28). Under more vigorous conditions with either nitric or chromic acid, cleavage at the double bond occurs to afford benzoic acid. Epoxidation of cinnamaldehyde via a conjugate addition mechanism is observed upon treatment with a salt of /-butyl hydroperoxide (29). 

Cobalt compounds can be classified as relatively nontoxic (33). There have been few health problems associated with workplace exposure to cobalt. The primary workplace problems from cobalt exposure are fibrosis, also known as hard metal disease (34,35), asthma, and dermatitis (36). Finely powdered cobalt can cause siUcosis. There is Htfle evidence to suggest that cobalt is a carcinogen in animals and no epidemiological evidence of carcinogenesis in humans. The LD q (rat) for cobalt powder is 1500 mg/kg. The oral LD q (rat) for cobalt(II) acetate, chloride, nitrate, oxide, and sulfate are 194, 133, 198, 1700, 5000, and 279 mg/kg, respectively the intraperitoneal LD q (rat) for cobalt(III) oxide is 5000 mg/kg (37). 

Cyclohexane is also a precursor for adipic acid. Oxidizing cyclohexane in the liquid-phase at lower temperatures and for longer residence times (than for KA oil) with a cobalt acetate catalyst produces adipic acid ... 

The catalyzed oxidation of p-xylene produces terephthalic acid (TPA). Cobalt acetate promoted with either NaBr or HBr is used as a catalyst in an acetic acid medium. Reaction conditions are approximately 200°C and 15 atmospheres. The yield is about 95% ... 

Quite different kinetics are exhibited by the anaerobic oxidation of alkyl-benzenes by cobaltic acetate in a 95 % acetic acid medium , viz. 

The cobaltous acetate reduction of tert-butyl hydroperoxide in acetic acid yields mainly ter/-butanol and oxygen the metal ion stays in the +2 oxidation state because of the reactivity of Co(III) towards hydroperoxides (p. 378) °. The rate law is... 

Oxidising acetaldehyde in air when cobalt acetate at -20°C is present gives rise to a detonation, if the medium is stirred. It has been put down to the formation of a very sensitive peroxidic compound. On the other hand, the presence of a halogen derivative inhibits this oxidation. 

Salts of transition metals are widely used in technological processes for the preparation of various oxygen-containing compounds from hydrocarbon raw materials. The principal mechanism of acceleration of RH oxidation by dioxygen in the presence of salts of heavy metals was discovered by Bawn [46 19] for benzaldehyde oxidation (see Chapter 1). Benzaldehyde was oxidized with dioxygen in a solution of acetic acid, with cobalt acetate as the catalyst. The oxidation rate was found to be [50] ... 

Alkylaromatic hydrocarbons, such as tetralin, ethylbenzene, and cumene, are oxidized in a solution of acetic acid in the presence of cobalt acetate by a different mechanism. In these... 

Celanese LPO [Liquid phase oxidation] A process for making acetic acid by oxidizing n-butane in the liquid phase, catalyzed by cobalt acetate. Developed by Hoechst Celanese and operated in the United States and The Netherlands. See also DF. 

Butane oxidation Cobalt acetate 300-450 800 57 Acetaldehyde + acetone + methanol... 

The TPA process. The technology involves the oxidation of p-xylene, as shown already in Figure 18—2. The reaction takes place in the liquid phase in an acetic acid solvent at 400°F and 200 psi, with a cobalt acetate/ manganese acetate catalyst and sodium bromide promoter. Excess air is present to ensure the p-xylene is fully oxidized and to minimize by-products. The reaction time is about one hour. Yields are 90—95% based on the amount of p-xylene that ends up as TPA. Solid TPA has only limited solubility in acetic acid, so happily the TPA crystals drop out of solution as they form. They are continuously removed by filtration of a slipstream from the bottom of the reactor. The crude TPA is purified by aqueous methanol extraction that gives 99 % pure flakes. 

A method was proposed for the preparation of p-hydroxybenzoic acid by oxidation of p-cresol with atmospheric oxygen in an acetic acid-acetic anhydride mixture under catalysis of cobalt acetate, manganese(II) acetate, and sodium bromide (Litvintsev et al. 1994). This procedure ensures 60% yield of p-acetoxybenzoic acid and 100% conversion of the initial p-cresol. 

The liquid-phase oxidation of p-methylacetophenone is important from practical and methodological points of view and deserves a concise consideration. The reaction is performed in acetic acid with the cobalt acetate catalyst. As shown by Obukhova et al. (2002), the catalyst detaches an electron from the substrate. The latter forms the cation-radical, which can dissociate in the following two ways ... 

When it was a major source for acetic acid, acetaldehyde was in the top 50 at about 1.5 billion lb. Now it is under a billion pounds but it is still used to manufacture acetic acid by further oxidation. Here a manganese or cobalt acetate catalyst is used with air as the oxidizing agent. Temperatures range from 55-80°C and pressures are 15-75 psi. The yield is 95%. 

Synonym Gamma-Chloropropylene Oxide 3-Chloro-1,2-Propylene Oxide Chlorosulfonic Acid Chlorothene Chiorotoluene, Alpha Alpha-Chlorotoluene Omega-Chlorotoluene Chlorotrifluoroethylene Chlorotrimethylsilane Chlorsulfonic Acid Clilorylen Clip Chromic Acid Chromic Anhydride Chromic Oxide Chromium (VI) Dioxychloride Chromium Oxychloride Chromium Trioxide Chromyl Chloride Cianurina Citric Acid Citric Acid, Diammonium Salt Clarified Oil Clorox Cc Ral Coal Tar Oil Cobalt Acetate Cobalt Acetate Tetrahydrate Cobalt (II) Acetate Cobalt Chloride Cobalt (II) Chloride Cobaltous Acetate Cobaltous Chloride Cobaltous Chloride Dihydrate Cobaltous Chloride Hexahydrate Cobaltous Nitrate Cobaltous Nitrate Hexahydrate Cobaltous Sulfate Heptahydrate Cobalt Nitrate Cobalt (II) Nitrate Cobalt Sulfate Compound Name Epichlorohydrin Epichlorohydrin Chlorosulfonic Acid Trichloroethane Benzyl Chloride Benzyl Chloride Benzyl Chloride Trifluorochloroethylene Trimethylchlorosilane Chlorosulfonic Acid Trichloroethylene Cumene Hydroperoxide Chromic Anhydride Chromic Anhydride Chromic Anhydride Chromyl Chloride Chromyl Chloride Chromic Anhydride Chromyl Chloride Mercuric Cyanide Citric Acid Ammonium Citrate Oil Clarified Sodium Hypochlorite Coumaphos Oil Coal Tar Cobalt Acetate Cobalt Acetate Cobalt Acetate Cobalt Chloride Cobalt Chloride Cobalt Acetate Cobalt Chloride Cobalt Chloride Cobalt Chloride Cobalt Nitrate Cobalt Nitrate Cobalt Sulfate Cobalt Nitrate Cobalt Nitrate Cobalt Sulfate... 

Noncatalytic oxidation to produce acetic acid can be carried out in the gas phase (350-400°C, 5-10 atm) or in the liquid phase (150-200°C). Liquid-phase catalytic oxidations are operated under similar mild conditions. Conditions for the oxidation of naphtha are usually more severe than those for n-butane, and the process gives more complex product mixtures.865-869 Cobalt and other transition-metal salts (Mn, Ni, Cr) are used as catalysts, although cobalt acetate is preferred. In the oxidation carried out in acetic acid solution at almost total conversion, carbon oxides, carboxylic acids and esters, and carbonyl compounds are the major byproducts. Acetic acid is produced in moderate yields (40-60%) and the economy of the process depends largely on the sale of the byproducts (propionic acid, 2-butanone). 

Y. Kamiya illustrates the influence on catalytic activity of the form of the catalyst. Thus, in the cobalt-catalyzed oxidation of hydrocarbons in acetic acid solution, introduction of bromide ions increases the activity of the catalyst, especially when the metal ion concentration is fairly high. The presence of bromides also results in a marked increase in the proportion of carbonyl compounds among the products and it is believed that these are formed as a result of a propagation step in which bromine-containing cobaltous ions react with alkylperoxy radicals. 

Table I. Effect of NaBr on Oxidation Rate of Hydrocarbons Catalyzed by 5 X 10"2M Cobalt Acetate in Acetic Acid...

The activation energy of over-all oxidation catalyzed by 0.02M cobalt acetate and 0.04M NaBr is very small—8.3 kcal./mole for ethylbenzene, 8.7 for p-xylene, and 14.9 for n-dodecane. 

The broken line in Figure 2 shows that the steady rate of oxidation of 4.07M ethylbenzene in acetic acid, catalyzed by cobalt acetate, reaches a limiting rate of 2.2 X 10 r> mole liter"1 sec. 1 (after correcting for the dielectric effect (5,9), 1.8 X 10 5), which is in excellent agreement with the theoretical limiting rate of 1.85 X 10"r> mole liter 1 sec. 1 as calculated by 32(RH)2/2 6. 

The solvent acid also affects the oxidation rate since the rate with cobalt acetate (Table II) is reduced in propionic or butyric acids in contrast to the increase in the hydroperoxide decomposition rate. 

The oxidation rate of 0.5 gram atactic polypropylene with 0.02M cobalt acetate in 10 ml. of a 1/1 mixture by volume of chlorobenzene and acetic acid increases from 2.7 X 10"4 to 2.76 X 10"8 mole kg. 1 sec."1 in the presence of 0.04M sodium bromide. The rate of powdered isotactic polypropylene under the same conditions increases only from 2.05 X 10"8 to 2.45 X 10"3 mole kg. 1 sec. 1 in the presence of sodium bromide. 

It is known that olefins are oxidized easily by cobaltic sulfate (2) and toluene by Co3+(H20)6 (3). We found that various hydrocarbons (12) such as toluene, ethylbenzene, and cumene can be oxidized rapidly by cobaltic acetate in the absence of oxygen. 

The distribution of by-products originating from the methyl group in acetaldehyde oxidation is significantly different for each catalyst. Typical results are presented in Table II. Methane is the predominant by-product with cobalt acetate, while methane and carbon dioxide and methyl esters and carbon dioxide predominate with manganese and copper acetates, respectively. 

Reaction 22a is important only with cobalt acetate catalyst and accounts for the fast rate of methane formation during the reaction of peracetic with acetaldehyde. It can also explain how methane is produced only from the methyl group of peracetic acid. This reaction path is more important with cobalt probably because of the higher oxidation potential of the cobalt (III)-cobalt (II) couple relative to that of the manganese (III) -manganese (II) couple. 

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