Manganese acetate acetaldehyde oxidation

Oxidation. Acetaldehyde is readily oxidised with oxygen or air to acetic acid, acetic anhydride, and peracetic acid (see Acetic acid and derivatives). The principal product depends on the reaction conditions. Acetic acid [64-19-7] may be produced commercially by the Hquid-phase oxidation of acetaldehyde at 65°C using cobalt or manganese acetate dissolved in acetic acid as a catalyst (34). Liquid-phase oxidation in the presence of mixed acetates of copper and cobalt yields acetic anhydride [108-24-7] (35). Peroxyacetic acid or a perester is beheved to be the precursor in both syntheses. There are two commercial processes for the production of peracetic acid [79-21 -0]. Low temperature oxidation of acetaldehyde in the presence of metal salts, ultraviolet irradiation, or osone yields acetaldehyde monoperacetate, which can be decomposed to peracetic acid and acetaldehyde (36). Peracetic acid can also be formed directiy by Hquid-phase oxidation at 5—50°C with a cobalt salt catalyst (37) (see Peroxides and peroxy compounds). Nitric acid oxidation of acetaldehyde yields glyoxal [107-22-2] (38,39). Oxidations of /)-xylene to terephthaHc acid [100-21-0] and of ethanol to acetic acid are activated by acetaldehyde (40,41). 

The Acetaldehyde Oxidation Process. Liquid-phase catalytic oxidation of acetaldehyde (qv) can be directed by appropriate catalysts, such as transition metal salts of cobalt or manganese, to produce anhydride (26). Either ethyl acetate or acetic acid may be used as reaction solvent. The reaction proceeds according to the sequence... 

The present work was initiated as a consequence of an exploratory program on acetaldehyde oxidation in which copper (II), manganese (II), and cobalt (II) acetates were evaluated. The results indicate a significant difference both in acetaldehyde efficiency to acetic acid and in by-product distribution. 

Acetaldehyde Oxidation. In the oxidation of acetaldehyde with oxygen-nitrogen mixtures, at conditions under which the rate-limiting factor is oxygen transfer to the solution, manganese (II) acetate gives a better efficiency to acetic acid than copper (II) acetate, which in turn is better than cobalt (II) acetate. However, when either cobalt (II) or copper (II) acetate is used in the presence of manganese (II) acetate, the... 

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. 

Oxidation of Acetaldehyde. When using cobalt or manganese acetate the main role of the metal ion (beside the initiation) is to catalyze the reaction of peracetic acid with acetaldehyde so effectively that it becomes the main route to acetic acid and can also account for the majority of by-products. Small discrepancies between acetic acid efficiencies in this reaction and those obtained in acetaldehyde oxidation can be attributed to the degradation of peracetoxy radicals—a peracetic acid precursor— by Reactions 14 and 16. The catalytic decomposition of peracetic acid is too slow (relative to the reaction of acetaldehyde with peracetic acid) to be significant. The oxidation of acetyl radical by the metal ion in the 3+ oxidation state as in Reaction 24 is a possible side reaction. Its importance will depend on the competition between the metal ion and oxygen for the acetyl radical. 

Acetaldehyde Oxidation. Ethanol [64-17-5] is easily dehydrogenated oxidatively to acetaldehyde (qv) using silver, brass, or bronze catalysts. Acetaldehyde can then be oxidized in the liquid phase in the presence of cobalt or manganese salts to yield acetic acid. Peracetic acid [79-21-0] formation is prevented by the transition metal catalysts (7). (Most transition metal salts decompose any peroxides that form, but manganese is uniquely effective.)... 

Acetic acid is usually made by one of three routes acetaldehyde oxidation, involving direct air or oxygen oxidation of liquid acetaldehyde in the presence of manganese acetate, cobalt acetate, or copper acetate liquid-phase oxidation of butane or naphtha methanol carbonylation using a variety of techniques. 

Acetaldehyde is separated from the light products by scrubbing with water, concentrated, and then oxidized to acetic add in the presence of manganese acetate. The intense corrosion implies the use of coatings of titanium, resin-impregnated graphite, ceramics, etc. 

Side reactions are the formation of dehydration of the pendent 2-hy-droxyethyl ester to result in pendent vinyl ester groups. These can further react under the ejection of acetaldehyde. Suitable catalysts are germanium compounds, such as germanium oxide, zinc acetate, manganese acetate, or a combination of antimony trioxide and trimethyl phosphate. ... 

Small amounts of acetaldehyde (from acetylene) are converted industrially into alcohol by catalytic hydrogenation, and large amounts are transformed into acetic acid by catalysed autoxidation (with oxides of manganese). 

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%. 

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. 

Manganese dioxide at 200° oxidises alcohol to aldehyde and is itself reduced to Mn203 at 250° the Mn303 brings about further oxidation and tho products are acetaldehyde, carbon dioxide, and acetic acid. 

The roles of manganese in TPA manufacture are better understood than in the Witten process, and include decomposition of the CH2COOH radical (derived from the acetic acid solvent) and regeneration of the bromine atom promoter [13], In an effort to eliminate halogen compounds which are highly corrosive to oxidation equipment, use of acetaldehyde [14] and paraldehyde [15] has been developed. These aldehyde promoters are ultimately converted to acetic acid in high yield. For economic reasons, these aldehyde processes have been abandoned in favor of the bromine-promoted Amoco process. 

Ethyl acetate can be obtained by the dehydrogenation of ethanol in 95.7% yield.25 The process may involve a disproportionation of the intermediate acetaldehyde. It can also be made by direct esterification of ethanol using acetic acid made by fermentation. Acetone was prepared in 97-98% yield by treatment of acetic acid with cerium (IV) oxide on silica26 or manganese nodules from the Indian Ocean.27 This is an alternative to the fermentation that produces it along with 1-butanol and might be preferable, in that any process that produces two coproducts must find adequate outlets in the market for both of them. There is a loss of one carbon when acetic acid is converted to acetone. 

The oxidation of acetaldehyde for the commercial production of acetic acid can be accomplished with pure oxygen or air in the presence of manganese or cobalt-acetate catalyst solutions [Eq. (6.15.2)]. The use of air saves the air separation unit but has the disadvantage that its high N2 content requires extensive purging to avoid build-up of inerts in the process ... 

Some acetic acid still is derived from cthyiene-based acetaldehyde by oxidation with molecular oxygen, This is a free radical process and typically is manganese salt-... 

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