Oxidation of acetaldehyde

Backstrom [24] found that the photochemical oxidation of acetaldehyde in the liquid phase led to the formation of peracetic acid as the primary product. Bowen and Tietz [25] examined the photochemical oxidation of acetaldehyde in the gas and liquid phases the primary product was always peracetic acid. The kinetic results of this work are the same as those obtained in 1951 by Niclause and coworkers [26] in their later kinetic investigation of the oxidation in the liquid phase using a wider range of conditions. 

Photochemical initiation is brought about by a UV lamp with a maximum intensity for X between 2967 and 3200 A. The temperature range 

The kinetic characteristics of this oxidation are similar to those obtained with decanal and are 

F depends to an increasing extent on P0l up to a maximum value of unity. It also depends to a decreasing extent on temperature. The activation energy for V is equal to 3.5 kcal mole-1. 

Bawn and Williamson [9] examined the catalyzed oxidation of acetaldehyde in solution in acetic acid at 25°C. Whereas uncatalyzed oxidation has mediocre reproducibility, catalyzed oxidations are reproducible within 2%. The catalyst was cobalt acetate in solution in the cobaltous form. The partial oxygen pressure varied from 550 to 950 torr. Under such conditions, as in the case of photochemical oxidations, the stoichiometry of the reaction follows the overall equation 

The oxidation chemistry of small, partially-oxygenated fuels is of great interest in combustion chemistry as these are important intermediates in the combustion of virtually all commercial hydrocarbon fuels. Fuels with long carbon backbones react in their early stages mainly through a sequence of reactions that cause chain rupture, yielding smaller hydrocarbon fragments such as radicals. These then typically react with O2 to produce precursors of aldehydes, ketones etc. Not all of the features of acetaldehyde chemistry are completely representative of hydrocarbon oxidation, but this point is developed in the next chapter. 

The basic global behaviour of a mixture of acetaldehyde vapour in O2 is illustrated by reference to the p-T ignition diagram. Fig. 5.39. Up to five regions of qualitatively different responses are characteristic [75]. At low ambient temperature and pressure, the system exhibits a steady dark reaction. Region I. This may support a measurable steady-state tem- 

The products detected from reaction in region IV include CO, H2O, CH2O, CH3OH and CH4 and lower quantities of peracetic acid, ethane (C2H6) and hydrogen peroxide (H2O2) all of which oscillate with the cool-flame period as indicated in Fig. 5.41. 

We may also note that at yet higher T), beyond region V, a simple ignition limit may be encountered. 

It is evident that A5 e 0, indicating that the equilibrium will shift from 

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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. 

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... 

Facial dushing after ingestion of alcohol occurs in up to one-third of patients taking chlorpropamide. The mechanism, like that of the disulfiram reaction, probably involves inhibition of the oxidation of acetaldehyde, a metaboUte of ethanol. The plasma concentration of chlorpropamide may be correlated with chlorpropamide—alcohol dushing. 

This process is one of the three commercially practiced processes for the production of acetic anhydride. The other two are the oxidation of acetaldehyde [75-07-0] and the carbonylation of methyl acetate [79-20-9] in the presence of a rhodium catalyst (coal gasification technology, Halcon process) (77). The latter process was put into operation by Tennessee Eastman in 1983. In the United States the total acetic anhydride production has been reported to be in the order of 1000 metric tons. 

Although this process has not been commercialized, Daicel operated a 12,000-t/yr propylene oxide plant based on a peracetic acid [79-21-0] process during the 1970s. The Daicel process involved metal ion-catalyzed air oxidation of acetaldehyde in ethyl acetate solvent resulting in a 30% peracetic acid solution in ethyl acetate. Epoxidation of propylene followed by purification gives propylene oxide and acetic acid as products (197). As of this writing (ca 1995), this process is not in operation. 

Viayl acetate [108-05-4] is obtained by vapor-phase oxidation of ethylene with acetic acid. Acetic acid is obtained by oxidation of acetaldehyde. 

Acetic acid is also produced hy the oxidation of acetaldehyde and the oxidation of n-hutane. However, acetic acid from the carhonylation route has an advantage over the other commercial processes because both methanol and carbon monoxide come from synthesis gas, and the process conditions are quite mild. 

Acetic acid is obtained from different sources. Carbonylation of methanol is currently the major route. Oxidation of butanes and butenes is an important source of acetic acid, especially in the U.S. (Chapter 6). It is also produced by the catalyzed oxidation of acetaldehyde ... 

Approximately 2.5 million tons of acetic acid is produced each year in the United States for a variety of purposes, including preparation of the vinyl acetate polymer used in paints and adhesives. About 20% of the acetic acid synthesized industrially is obtained by oxidation of acetaldehyde. Much of the remaining 80% is prepared by the rhodium-catalyzed reaction of methanol with carbon monoxide. 

Acetic acid can also be obtained by the oxidation of acetaldehyde, CH3CHO ... 

Threonine. Threonine is cleaved to acetaldehyde and glycine. Oxidation of acetaldehyde to acetate is followed by formation of acetyl-CoA (Figure 30-10). Catabolism of glycine is discussed above. 

DuPont has developed a process for the manufacture of glyoxylic acid by aerobic oxidation of glycolic acid (Fig. 2.33) mediated by whole cells of a recombinant methylotrophic yeast (Gavagnan et al, 1995). The glycolic acid raw material is readily available from the acid-catalysed carbonylation of formaldehyde. Traditionally, glyoxylic acid was produced by nitric acid oxidation of acetaldehyde or glyoxal, processes with high E factors, and more recently by ozonolysis of maleic anhydride. 

Glyoxal has been obtained by several methods, only a few of which are of preparative value. The most feasible are the oxidation of acetaldehyde by nitric3 4 5 or selenious6 acid the hydrolysis of dichlorodioxane 7 and the hydrolysis of the product resulting from the action of fuming sulfuric acid upon tetra-haloethanes.8... 

The chain unit in the thermal and photochemical oxidation of aldehydes by molecular dioxygen consists of two consecutive reactions addition of dioxygen to the acyl radical and abstraction reaction of the acylperoxyl radical with aldehyde. Experiments confirmed that the primary product of the oxidation of aldehyde is the corresponding peroxyacid. Thus, in the oxidation of n-heptaldehyde [10,16,17], acetaldehyde [4,18], benzaldehyde [13,14,18], p-tolualdehyde [19], and other aldehydes, up to 90-95% of the corresponding peroxyacid were detected in the initial stages. In the oxidation of acetaldehyde in acetic acid [20], chain propagation includes not only the reactions of RC (0) with 02 and RC(0)00 with RC(0)H, but also the exchange of radicals with solvent molecules (R = CH3). 

Washing for over 100 h in a solvent such as toluene before the reaction resulted in no significant loss of the catalytic activity, and recovery and reusability studies at high turnover number also indicated the catalyst stability. Same catalysts, H5[PV2Mo10O40] supported on fiber and fabric carbon materials, catalyzed 02-based oxidations of acetaldehyde and 1-propanethiols [113], This aerobic heterogeneous oxidation proceeded under mild reaction conditions. 

The second category of aldehyde dehydrogenases are efficient catalysts of the oxidation of both aryl and alkyl aldehydes to the corresponding carboxylic acids. The most well known and common of such reactions is the oxidation of acetaldehyde, derived from alcohol, to acetic acid. 

FIGURE 4.39 AO-catalyzed oxidation of acetaldehyde to acetic acid. 

These materials are very easily autoxidised and often have a low autoignition temperature. It is reported that many of the less volatile liquid aldehydes will eventually inflame if left exposed to air on an absorbent surface. The mechanism is undoubtedly similar to that giving rise to easy ignition in the air-oxidation of acetaldehyde and propionaldehyde initial formation of a peroxy-acid which catalyses the further oxidation[l]. Autoignition temperatures of lower aldehydes are much reduced by pressure, but appear to depend little on oxygen content. The effect is worst in the presence of free liquid, in which initial oxidation appears to occur, possibly catalysed by iron, followed by ignition of the vapour phase [2], An acetaldehyde/rust mix exploded at room temperature on increasing the air pressure to 7 bar. 

Acetic acid, CH3COOH, can be made by the oxidation of acetaldehyde, CH3CHO by catalytic addition of CO to methanol or by butane oxidation. Most acetic acid is used to make vinyl acetate or cellulose acetate, which are the intermediates for plastics, paints, adhesives, yarn, and cigarette filters. 

McDowell, C. A., and Thomas, J. H., Oxidation of Aldehydes in the Gaseous Phase Part IV. The Mechanism of the Inhibition of the Gaseous Phase Oxidation of Acetaldehyde by Nitrogen Peroxide, Transactions of the Faraday Society, Vol. 46, No. 336, 1950, pp. 1030-1039. 

This enzyme [EC 1.2.1.10] catalyzes the oxidation of acetaldehyde in the presence of NAD+ and coenzyme A to form acetyl-CoA -i- NADH + H+. Other aldehyde substrates include glycolaldehyde, propanal, and bu-tanal. 

Table 8.1 shows the stochastic model solution for the petrochemical system. The solution indicated the selection of 22 processes with a slightly different configuration and production capacities from the deterministic case, Table 4.2 in Chapter 4. For example, acetic acid was produced by direct oxidation of n-butylenes instead of the air oxidation of acetaldehyde. Furthermore, ethylene was produced by pyrolysis of ethane instead of steam cracking of ethane-propane (50-50 wt%). These changes, as well as the different production capacities obtained, illustrate the effect of the uncertainty in process yield, raw material and product prices, and lower product... 

Acetic acid is one of the oldest known chemicals. Dilute acetic acid, vinegar, has been made by aerobic bacterial oxidation of ethanol. It has also been reclaimed by extraction or extractive distillation from pyroligneous acid, which was obtained from the extractive distillation of wood (J ). In the early nineteen hundreds, oxidation of acetaldehyde became the main source of acetic acid. The acetaldehyde has been obtained from acetylene ( ). ethylene (3) or ethanol as indicated below. 

Doping with small amounts of noble metals was often used to promote the photobehavior. However, the loealization of these metal nanoparticles within the Ti02 nanotubes was reeently shown to have an important role. Nishijima et investigated site-seleetive deposition of Pt nanoparticles on a titania nanotube (TNT). When Pt nanopartieles were deposited only inside the TNT, aetive sites on the TNT were not covered by Pt nanoparticles, resulting in an inerease in its photoeatalytic activity for oxidation of acetaldehyde. 

Action of Aliphatic Amines on Slow Oxidation of Acetaldehyde and Ethyl Ether, and on Decomposition of Organic Peroxides in the Gas Phase... 

Aliphatic amines have much less effect on the later reactions of the gas-phase oxidation of acetaldehyde and ethyl ether than if added at the start of reaction. There is no evidence that they catalyze decomposition of peroxides, but they appear to retard decomposition of peracetic acid. Amines have no marked effect on the rate of decomposition of tert-butyl peroxide and ethyl tert-butyl peroxide. The nature of products formed from the peroxides is not altered by the amine, but product distribution is changed. Rate constants at 153°C. for the reaction between methyl radicals and amines are calculated for a number of primary, secondary, and tertiary amines and are compared with the effectiveness of the amine as an inhibitor of gas-phase oxidation reactions. 

Mechanism I. Following work on the slow oxidation of acetaldehyde, during which the surface-volume ratio of the reaction vessel was varied, Cullis and Khokhar (8) interpreted the mechanism in terms of the ability of amines to be absorbed onto the surface of the reaction vessel. Thus, if the chain-initiating processes between the fuel and oxygen occur on the surface, the fuel will not be oxidized until the amine is burned off. 

Action of Aliphatic Amines on Oxidation Products of Acetaldehyde. Peracetic acid is formed in large quantities during the early stages of the slow oxidation of acetaldehyde—i.e., during the time of negative pressure change (12, 20, 21, 22). 

Diethylamine, a powerful inhibitor of acetaldehyde oxidation when added at the start of the reaction (10), was added during the oxidation of acetaldehyde. The later the inhibitor is added, the less effect it has on the subsequent reaction, although the length of the induction period still depends on the amount of amine added (Figure 1). Again, the... 

It is believed that peractic acid is primarily responsible for chain branching during the oxidation of acetaldehyde (12) and ethyl ether (24, 27). Although amines are powerful inhibitors of these oxidation processes, they have much less effect if added during the reaction. The inhibiting power of amines becomes smaller the longer the reaction between the fuel and oxygen has proceeded. Similar behavior is observed... 

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