Cyclohexane nitric acid reaction

Since adipic acid has been produced in commercial quantities for almost 50 years, it is not surprising that many variations and improvements have been made to the basic cyclohexane process. In general, however, the commercially important processes stiU employ two major reaction stages. The first reaction stage is the production of the intermediates cyclohexanone [108-94-1] and cyclohexanol [108-93-0], usuaHy abbreviated as KA, KA oil, ol-one, or anone-anol. The KA (ketone, alcohol), after separation from unreacted cyclohexane (which is recycled) and reaction by-products, is then converted to adipic acid by oxidation with nitric acid. An important alternative to this use of KA is its use as an intermediate in the manufacture of caprolactam, the monomer for production of nylon-6 [25038-54-4]. The latter use of KA predominates by a substantial margin on a worldwide basis, but not in the United States. 

Although many variations of the cyclohexane oxidation step have been developed or evaluated, technology for conversion of the intermediate ketone—alcohol mixture to adipic acid is fundamentally the same as originally developed by Du Pont in the early 1940s (98,99). This step is accomplished by oxidation with 40—60% nitric acid in the presence of copper and vanadium catalysts. The reaction proceeds at high rate, and is quite exothermic. Yield of adipic acid is 92—96%, the major by-products being the shorter chain dicarboxytic acids, glutaric and succinic acids,and CO2. Nitric acid is reduced to a combination of NO2, NO, N2O, and N2. Since essentially all commercial adipic acid production arises from nitric acid oxidation, the trace impurities patterns ate similar in the products of most manufacturers. 

Other processes explored, but not commercialized, include the direct nitric acid oxidation of cyclohexane to adipic acid (140—143), carbonylation of 1,4-butanediol [110-63-4] (144), and oxidation of cyclohexane with ozone [10028-15-5] (145—148) or hydrogen peroxide [7722-84-1] (149—150). Production of adipic acid as a by-product of biological reactions has been explored in recent years (151—156). 

Cyclohexanone shows most of the typical reactions of aUphatic ketones. It reacts with hydroxjiamine, phenyUiydrazine, semicarbazide, Grignard reagents, hydrogen cyanide, sodium bisulfite, etc, to form the usual addition products, and it undergoes the various condensation reactions that are typical of ketones having cx-methylene groups. Reduction converts cyclohexanone to cyclohexanol or cyclohexane, and oxidation with nitric acid converts cyclohexanone almost quantitatively to adipic acid. 

The subsequent reaction of cyclohexane with air in the first step to adipic acid is not simple and, actually, is not well understood chemically. Only a small amount of cyclohexane present in the operation is allowed to react before the unreacted cyclohexane is recovered for recycle and the oxygen-containing products isolated for further reaction with nitric acid. Despite decades of research on this chemistry in efforts to increase yields and decrease by-product formation, substantial amounts of the starting cyclohex-... 

When nitric acid was added to cyclohexanol when preparing cyclohexane-1,2-dione, the reactor detonated, probably because of the exothermicity of the oxidation reaction, which was complete instead of partial (reaction (2)). 

Adipic acid is made by the reaction of nitric acid and cyclohexane. The adipic acid has two -COOH groups, which makes it very reactive. Adipic is used primarily for making Nylon 66. 

In the Dupont process, cyclohexane is reacted with air at 150 °C and 10 atm pressure in the presence of a soluble cobalt(II) salt (naphthenate or stearate). The conversion is limited to 8-10% in order to prevent consecutive oxidation of the ol-one mixture. Nonconverted cyclohexane is recycled to the oxidation reactor. Combined yields of ol-one mixture are 70-80%.83,84,555 The ol-one mixture is sent to another oxidation reactor where oxidation by nitric acid is performed at 70-80 °C by nitric acid (45-50%) in the presence of a mixture of Cu(N03)2 and NH4V03 catalysts, which increase the selectivity of the reaction. The reaction is complete in a few minutes and adipic acid precipitates from the reaction medium. The adipic acid yield is about 90%. Nitric acid oxidation produces gaseous products, mainly nitric oxides, which are recycled to a nitric acid synthesis unit. Some nitric acid is lost to products such as N2 and N20 which are not recovered. 

As mentioned earlier, soluble salts of cobalt and manganese catalyze oxidation of cyclohexane by oxygen to cyclohexanol and cyclohexanone. Cyclohexanol and cyclohexanone are oxidized by nitric acid to give adipic acid. The oxidation by nitric acid is carried out in the presence of V5+ and Cu2+ ions. These reactions are shown by Eq. 8.8. Adipic acid is used in the manufacture of nylon 6,6. 

Microemulsion-Mediated Hydrothermal Synthesis Triton X-100 was served as the surfactant, n-hexanol as co-surfactant, cyclohexane as the continuous oil phase, and a solution of titanium -butoxide dissolved in an acid (HCl or HNO3) was employed as the dispersed aqueous phase. The concentration of hydrochloric acid or nitric acid ranged from 0.5 M to 2.0 M. A transparent feedstock of microemulsions was charged into a Teflon-lined stainless autoclave and hydrothermal reaction was... 

Explosive reaction with nitric acid at 75°C. Reaction with hydrogen peroxide + nitric acid forms an explosive peroxide. To fight fire, use alcohol foam, dry chemical, or CO2. When heated to decomposition it emits acrid smoke and irritating fumes. See also KETONES and CYCLOHEXANE. 

In Amoco patents [18b], the addition of controlled amounts of water after the initiation ofthe oxidation reaction is claimed to be a tool to obtain a better yield to AA. The best yield achieved was 88% (based on the identifiable compounds) at 98% cyclohexane conversion, with a Co(II) acetate catalyst, an acetic add solvent, at 95 °C and 70 atm air pressure. It is reported that water, if present during the induction period, depletes the concentration of free radicals in the absence of water, the yield was remarkably lower. These results are comparable to those attained by the air /nitric acid two-step oxidation of cydohexane. 

The two phase nature of the reaction mixture (aqueous nitric acid/lanthanide salt and solvent/substrate) poses a number of questions. Foremost amongst these is the following in which phase does the actual nitration occur Comparison of the nitration rates using 1,2-dichloroethane (b.p. 83 °C) versus cyclohexane (b.p. 80 °C) as the solvents (both reactions performed at reflux) allows speculation on this matter. For the nitration of naphthalene with 10 mol% ytterbium(III) triflate a 78% conversion of naphthalene to mononitronaphthalenes occurred over 0.5h in 1,2-dichloroethane whereas for cyclohexane only a 24% conversion was observed. Based on this result it seems reasonable to conclude that the electrophilic substitution process transpires in the organic phase. 

AZOTE (French) (10102-44-0) A powerful oxidizer. Reacts with water, forming nitric acid and oxygen. Violent reaction with strong reducing agents, anhydrous ammonia, alcohols, chlorinated hydrocarbons, cyclohexane, ethers, fluorine, formaldehyde, fuels, nitrobenzene, oxygen difluoride, petroleum, sodium, toluene. Incompatible with combustible materials, red phosphorus, petroleum products. Forms explosive material with propylene. Vapor reacts violently with phospham. Attacks many metals in the presence of moisture. 

METHYLCYCLOHEXANONE or o-METHYLCYCLOHEXANONE or 1-METHYL-CYCLOHEXAN-2-ONE (583-60-8) Forms explosive mixture with air (flash point 118°F/48°C cc). Violent reaction with oxidizers, aldehydes, nitric acid, perchloric acid. A variety of unstable peroxides may be formed from the reaction with hydrogen peroxide. Incompatible with aliphatic amines, strong bases, hydrogen peroxide, perchloric acid. Attacks some plastics, rubber, and coatings. 

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