Oxidation to acetic add

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. 

The Union Carbide process starting with cydohexane, which is first converted to cyclohexanone, which is in tnm oxidized to caprolactooe. This compound is then converted to caprolactam by the action of ammonia, at 4O0°C, under 17.106 Pa absolute pressure. Cyclohexanone is oxidized around 50 C, at normal pressure, by means of peracetic add, in the presence of acetaldehyde, which is oxidized to acetic add. The plant built by Union Carbide was shut down shortly after its construction. Variants have been proposed by Degussa, Toa Gosei and Ugine Kuhlmann without industrial success. 

Apart from water, the most frequent impurity is acetaldehyde. The water content is eliminated by reaction with acetic anhydride. Acetaldehyde can be oxidized to acetic add with chromium(VI) oxide or potassium permanganate. The simplest purification procedure consists of refluxing glacial acetic add containing acetic anhydride for 1 h with chromium(VI) oxide, followed by fractional distillation. 

Another e of deamination is reductive deamination as carried out anaerobically by the Clostridia. Glydne gives acetic add, alanine and serine give propionic add, etc. Although evidently hydrogen plays some part in the reaction, only amino acids are necessary. For example, two moles of glydne are reductively deaminated in the presence of Cl. sporo-genes whilst at the same time a mole of alanine is oxidized to acetic add. 

Packed generator systems. The traditional acetifler comprises a tall vat packed with an inert material (usually birch twigs or wood shavings) which act as the carrier for the acetobacter culture. The alcoholic substrate is sprayed on the top of the column and allowed to flow down against a stream of air, introduced from the bottom of the vat, into a false bottom and is recirculated for several days until most of the alcohol has been oxidized to acetic add. 

Ethanol metabolism occurs mainly in the liver and proceeds by oxidation in two steps, first to acetaldehyde (CHjCHO) and then to acetic add (CH3CO2H)- When continuously present in the body, ethanol and acetaldehyde are toxic, leading to the devastating physical and metabolic deterioration... 

Acridine is readily oxidized to acridone by sodium dichromate and acetic acid. Pyridin-2-one and nicotinic acid have been found to undergo oxidation to oxalic add on treatment with Fenton s reagent (69CHE563). 

Alkyl groups attached to aromatic rings are oxidized more readily than the ring in alkaline media. Complete oxidation to benzoic adds usually occurs with nonspecific oxidants such as KMn04, but activated tertiary carbon atoms can be oxidized to the corresponding alcohols (R. Stewart, 1965 D. Arndt, 1975). With mercury(II) acetate, allylic and benzylic oxidations are also possible. It is most widely used in the mild dehydrogenation of tertiary amines to give, enamines or heteroarenes (M. Shamma, 1970 H. Arzoumanian, 1971 A. Friedrich, 1975). 

Alkylfurans are usually obtained by ring synthesis, decarboxylation of alkylfurancarboxy-lic acids, Wolff-Kishner reduction of aldehydes or ketones, or by reduction of halomethyl groups with zinc and acetic acid or LAH (79JOC3420) alkylation is of limited value. The chemistry of these compounds is conventional but oxidation to furancarboxylic adds cannot usually be carried out due to the lability of the ring. NBS bromination (Section 3.11.2.2.5) is a useful route to side-chain substituted compounds but reduction of esters to hydroxymethyl groups and subsequent transformation is often preferable. The haloalkyl compounds are extremely sensitive to resinification but if adequate precautions are taken they are... 

Much has been published on the selective electrochemical oxidation of a large variety of organic compounds, among which the higher alcohols (e.g. ethanol to acetic add, propanol-2 to acetone). The interesting point in the present context is that some of these conversions have also been studied purely catalytically in the liquid phase, employing catalysts such as Pt/C, with O2 or air as the oxidant. It has been remarked [152] that such systems should also be considered from an electrochemical point of view. Indeed, it stands to reason that the overall oxidation reaction is essentially the sum of the two constitutive electrochemical half-reactions [153]. In the case of alcohol oxidation we would then have... 

The catalytic oxidation of acetaldehyde in the liquid phase to acetic add by air or oxygen is still widely applied, and accounts for about 40 per cent of installed worldwide production capacity. 

Whereas the cobalt and manganese salts actually catalyze the oxidation, the effect of copper acetate essentially involves the decomposition of this complex to acetic add. The reaction takes place in slightly different conditions, depending on the type of oxidant employed. They can be summarized as follows x... 

Most of the methyl ethyl ketone (d ° 0.805t3 mp —819 0, bpt013 = 79.6°Q manufactured worldwide is produced by the dehydrogenation of secondary butanol Smaller quantities me obtained as a by-product of the oxidation of a-butane to acetic add. This is the case in the United States of Celanese in its Pampa, Texas, plant (40,000 t/year) and of Union Carbide in Brownsville, Texas (35,000 t/year). Plants of this type built in Western Europe have been shut down, including the Kooas plant in the Netherlands (20.000 year at Europoort) which was closed in 1979. 

The principal liquid phase processes, currently abandoned, which saw considerable development, are those of Hoechst, ICI Imperial Chemical industries), Nippon Gosei, etc Their common feature is operation at moderate temperatures, in the presence of palladium chloride and hydrochloric acid. They are self-sufficient in terms of acetic add, since they produce acetaldehyde as a by-product, which can be oxidized to the add and recycled. 

Mn(OAc)3 in AcOH at 60 °C oxidizes aldehydes RCH2CHO to RCH-CHO. These radicals add to alkenes to give radicals that abstract a hydrogen, or are oxidized to acetates or alkenes affording mixtures of limited synthetic utility [11a]. Similarly, Mn(OAc)3 in AcOH at 40-80 °C oxidizes acetophenone, acetone, cyclo-pentanone, cyclohexanone or other simple symmetrical ketones to a-keto radicals that add to alkenes leading to modest yields of coupled products [11a]. 

Another possibility is reduction of acetamide. This requires an initial oxidation of ethanol to acetic add. 

Table 9.1 summarizes catalyst compositions and corresponding performances. The oxidation of ethane to acetic add is now commerdal an industrial plant is installed, with the technology developed by Saudi Basic. Elements that have contributed to the successful development of the process are (1) the discovery of a catalytically active compound, the multifunctional properties of which can be modified and tuned to be adapted to reaction conditions through incorporation of various elements (2) the stability of the main products, ethylene and acetic add, which do not undergo extensive consecutive degradation reactions (3) the possibility of recyding the unconverted reactant and the major by-product, ethylene (4) the use of reaction conditions that minimize the formation of CO and (5) an acceptable overall process yield. 

The work was strongly inspired by Union Carbide s Ethoxene process, a route for manufacturing ethylene from ethane and oxygen by oxidative dehydrogenation. The first catalysts consisted of molybdenum, vanadium, and niobium oxides. The selectivity for ethylene was very high but, unfortunately, the conversion of ethane was low ( 10%). Therefore, scientists at the time focused on the co-production of ethylene and acetic acid. A catalyst consisting of molybdenum, vanadium, niobium, calcium, and antimony supported on a molecular sieve was developed (63% selectivity to acetic acid, 14% selectivity to ethylene, and 3% conversion of ethane). In addition, Rhone-Poulenc (catalyst vanadium oxide or vanadyl pyrophosphate) and BP (catalyst combination of rhenium and tungsten) patented processes for the production of acetic acid from ethane. Very efficient catalysts were also disclosed by Hoechst (molybdenum vanadate, promoted with Nb, Sb, Ca, and Pd, 250-280 °C, 15 bar, 86% selectivity to acetic add at 11% conversion of ethane per pass) and Sabic (phosphorus-modified molybdenum-niobium vanadate, 260 °C, 14 bar, 50% selectivity to acetic acid at 53% conversion of ethane). 

A closer inspection of the yields to the different products reveals that carbon dioxide is a minor product, below 3%, of the ethanol electrooxidation. The main product of the ethanol electrooxidation is acetaldehyde with a yield above 60% when using 1M ethanol. Nevertheless, the selectivity to the different products strongly depends on the concentration of ethanol thus the selectivity to acetaldehyde increases as the concentration of ethanol increases from 0.001 to 0.5 M whereas the selectivity to CO2 and to acetic add decreases in this concentration range [47] as shown in Figure 3.6. This observation has been ascribed to the lower probability of readsorption and further oxidation of partially oxidized intermediates due to a higher surface coverage of ethanol. 

Bianchini, C., Bambagioni, V., Filippi, J., Marchionni, A., Vizza, F., Bert P., and Tampucci, A. (2009) Selective oxidation of ethanol to acetic add in highly efficient polymer electrolyte membrane-direct ethanol fuel cells. Electrochemistry Communications, 11 (5), 1077-1080. 

Liquid-phase oxidation of associated gas. For comparison, it is worthwhile to briefly mention the liquid-phase oxidation of associated gas. in contrast to the gas-phase oxidation, wherein the bulk of the products are oxygenated compoimds with a number of carbon atoms smaller than in the original hydrocarbon, the hquid-phase oxidation makes it possible to introduce oxygen into the hydrocarbon molecule without changing the structure of the latter. For example, the oxidation of n-butane gives methyl ethyl ketone with a high )deld. The main product of the hquid-phase oxidation of n-butane is acetic add, which enables to organize its production by this method. The oxidation is carried out at a temperature of 175—200 °C and a pressme of 45—60 atm. In addition to acetic add, methyl ethyl ketone, ethyl acetate, methyl acetate, acetone, isobutanol, and other compoimds are formed. 

Another, even more elegant solution may be a cascade of alcohol- and aldehyde dehydrogenase (AldDH) to catalyze the through oxidation of ethanol to acetic add (Scheme 8.9) [60]. Hence, not only the NAD(P)H yield per equivalent of ethanol is doubled, but also acetic acid represents a thermodynamically and Idnetically inert coproduct, thereby making the entire regeneration reaction irreversible. 

Acetic acid (qv) can be produced synthetically (methanol carbonylation, acetaldehyde oxidation, butane/naphtha oxidation) or from natural sources (5). Oxygen is added to propylene to make acrolein, which is further oxidized to acryHc acid (see Acrylic acid and derivatives). An alternative method adds carbon monoxide and/or water to acetylene (6). Benzoic acid (qv) is made by oxidizing toluene in the presence of a cobalt catalyst (7). 

In a first step oxidized aromatic amines are reduced with titaniumflll) chloride in glacial acetic add solution and then condensed to a colored Schiff s base with 4-(dimethylamino)-benzaldehyde (cf. Chapter 2). 

Several other important commercial processes need to be mentioned. They are (not necessarily in the order of importance) the low pressure methanol process, using a copper-containing catalyst which was introduced in 1972 the production of acetic add from methanol over RhI catalysts, which has cornered the market the methanol-to-gasoline processes (MTG) over ZSM-5 zeolite, which opened a new route to gasoline from syngas and ammoxidation of propene over mixed-oxide catalysts. In 1962, catalytic steam reforming for the production of synthesis gas and/or hydrogen over nickel potassium alumina catalysts was commercialized. 

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