Acetic acid acetaldehyde oxidation

It is well established that the main products of ethanol electro-oxidation on Pt in acidic media are acetaldehyde and acetic acid, partial oxidation products that do not require C—C bond breaking, with their relative yields depending on the experimental conditions [Iwasita and Pastor, 1994]. Apart from the loss of efficiency associated with the partial oxidation, acetic acid is also unwanted, as it constitutes a catalyst poison. 

TABLE 11.2 Chemical Yields in Acetic Acid, Acetaldehyde, and CO2 for Pt/C and Pt-Sn (9 1)/C Catalysts during Ethanol Electro-oxidation under DEFC Operating Conditions at 80 "C for 4 Honrs ... 

Rhone-Poulenc/Melle Bezons A process for making acetic acid by oxidizing acetaldehyde with oxygen in air. Removal of the nitrogen would incur a cost penalty. 

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%. 

Degussa AG Acetic acid Acetaldehyde Pharmaceutical purity, catalyst recovery, oxidation with air or oxygen 2 1993... 

Mo is the essential element of effective catalysts for propene oxidation to acrolein and acrolein oxidation to acrylic acid, while V is an essential element for effective catalysis of acrolein oxidation to acrylic acid. Mo-V-Nb oxide catalysts are capable of activating propane even at 573 K, but yields products of acetic acid, acetaldehyde, and carbon oxides. The addition of Te or Sb to Mo-V-Nb oxides induces certain structural changes leading to the formation of acrylic acid. ... 

The future of the commercial acetaldehyde processes mainly depends on the availability of cheap ethylene. Acetaldehyde has been replaced as a precursor for 2-ethylhexanol ( aldol route ) or acetic acid (via oxidation cf. Sections 2.1.2.1 and 2.4.4). New processes for the manufacture of acetic acid are the Monsanto process (carbonylation of methanol, cf. Section 2.1.2.1), the Showa Denko one-step gas-phase oxidation of ethylene with a Pd-heteropolyacid catalyst [75, 76], and Wacker butene oxidation [77]. Other outlets for acetaldehyde such as pentaerythritol and pyridines cannot fill the large world production capacities. Only the present low price of ethylene keeps the Wacker process still attractive. 

It should also be emphasized that very little experimental kinetic research has been done on oxidations with high aldehyde conversion rates because such oxidations are made complex by the reaction of the peracid formed on the aldehyde present, by the complementary initiation caused by the peracid, and by the inhibition reactions. Likewise, very little kinetic data have been published on the oxidation of aldehydes on an industrial scale, particularly concerning the oxidation of acetaldehyde in acetic acid, the oxidation of aldehydes in peracetic acid, or the oxidation of acetaldehyde in acetic anhydride. 

Acetic acid, the oxidation product of ethanol and acetaldehyde, has a very different adsorption behavior from that of most organic species. It is one of the rare organic species which, at least at not too high concentrations, adsorbs reversibly on Pt and other noble metals. It is an open question what is the structure of the adsorbed species and whether acetate ions or undissociated acetic acid molecules are the surface species in the case of an acidic supporting electrolyte. This question was examined by FTIR study at the basal planes at platinum single-crystal electrodes [Pt(lOO), Pt(llO), and Pt (111)]. The authors concluded that acetic acid, adsorbed from a 0.1 mol dm HCIO4 supporting electrolyte, is in the form of acetate-ion on all crystal faces studied. This view is in conflict with the statements made by other authors. ... 

Reactions (5) and (6) are slow and their products are only confirmed with highly selective vibrational techniques. Main products of ethanol oxidation on Pt electrode at potentials up to 0.6 V are acetaldehyde, acetic acid, and carbon dioxide, with electron conversions of 2, 4, or 12 respectively. Since practical potentials for DEFC are lower than 0.6 V at which the total oxidation to CO2 proceeds slowly, the buildup of unreacted CO quickly poisons the Pt electrode surface. A study by Behm et al. showed that the ethanol oxidation on Pt/C yields acetic acid, acetaldehyde... 

Oxidative breaking of C-C bonds giving acetic acid, acetaldehyde, methanol, and formaldehyde... 

Historically, the application of MMO as catalysts for propane oxidation to acrylic acid began in the late 1970s with Mo-V-Nb mixed oxides, previously reported as a catalyst for ethane oxidation [54]. The results of propane oxidation over this catalyst show that propane could be activated at 300°C, but producing only acetic acid, acetaldehyde, and carbon oxides. However, the possibility to activate... 

There are three important industrial preparations of acetic acid ethene oxidation through acetaldehyde (Section 12-16) air oxidation of butane and carbonylation of methanol. The mechanisms of these reactions are complex. 

Ethanol, being a t> pical primary alcohol containing the -CH OH group, gives on oxidation first acetaldehyde and then acetic acid. This process, when carried out by an aqueous oxidising agent, probably consists in the direct... 

To prepare acetic acid, aqueous ethanol is added gradually to a hot mixture of aqueous sodium dichromate and sulphuric acid. The oxidising mixture is now always in excess, and therefore the oxidation proceeds as far as possible moreover, the reaction is carried out under reflux, so that any acetaldehyde which volatilises is returned to the oxidising mixture. Hence the final product contains only a small amount of acetaldehyde. 

Technically, acetaldehyde is mainly made by the oxidation of ethylene using a CuCl2/PdCl2 catalyst system.. Although some acetic acid is still prepared by the catalytic oxidation of acetaldehyde, the main process is the catalytic oxidation of paraffins, usually -butane. 

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