JP2841696B2 - Method for producing cyclohexanone and cyclohexanol - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for industrially advantageously producing cyclohexanone and cyclohexanol by subjecting cyclohexane to liquid phase oxidation with molecular oxygen.

Cyclohexanone and cyclohexanol are used as raw materials for producing ε-aminocaprolactam.

(Prior Art) Method for producing cyclohexanone and cyclohexanol by oxidizing cyclohexane with molecular oxygen or a gas containing molecular oxygen in the liquid phase in the presence of 0.1 to 100 ppm of cobalt as a soluble cobalt salt as a catalyst Is known. (Chemistry Handbook, Applied Chemistry, p. 536
5) Maruzen, edited by The Chemical Society of Japan) (Problems to be Solved by the Invention) However, the conventional method has a large amount of by-products and a low proportion of cyclohexanone.

Industrially, a mixture of cyclohexanone and cyclohexanol is mainly used as a raw material for producing ε-aminocaprolactam. When used for the production of ε-aminocaprolactam, cyclohexanone is required, and cyclohexanol requires a step of dehydrogenation and conversion to cyclohexanone. Therefore, it is preferable that the production ratio of cyclohexanone is high.

In view of such circumstances, as a result of intensive studies on a method for producing cyclohexanone and cyclohexanol by oxidizing cyclohexane, the concentration of the cobalt catalyst was found to be lower than that in the case where the reaction apparatus for performing the oxidation reaction was a single tank, When connected continuously in a tank or more, in the final reaction apparatus, that is, by oxidizing at a final concentration of 0.01 ppm or more and 0.1 ppm or less as cobalt, the selectivity of cyclohexanone and cyclohexanol, especially the selectivity of cyclohexanone And high quality cyclohexanone can be obtained, and the present invention has been completed.

(Means for Solving the Problems) That is, in a method for producing cyclohexanone and cyclohexanol by oxidizing cyclohexane with molecular oxygen or a gas containing molecular oxygen in the presence of a cobalt catalyst in a liquid phase, A method for producing cyclohexanone and cyclohexanol, wherein the final concentration of the catalyst is 0.01 ppm or more and less than 0.1 ppm as cobalt.

The present invention is carried out in the same manner as in the conventional method except for the amount of the catalyst used. That is, cyclohexane is heated in the presence of a cobalt catalyst at a temperature of about 80 to 200 ° C. and a pressure of about 1 to 20 atm.
The reaction mixture containing hydroperoxides such as cyclohexanone, cyclohexanol, cyclohexyl hydroperoxide, acids, and esters is obtained by liquid phase oxidation with molecular oxygen or a gas containing molecular oxygen under the following conditions. Can be

The cyclohexane is preferably industrially pure cyclohexane, but may contain a small amount of cyclohexanone, cyclohexanol, acids, esters, water and the like.

Molecular oxygen or a gas containing molecular oxygen is oxygen,
Examples include air, a gas obtained by diluting air with an inert gas such as nitrogen, a gas obtained by adding oxygen to air, and a gas obtained by adding oxygen to an inert gas such as exhaust gas in an oxidation reaction step.

The reaction temperature is about 80-200 ° C, preferably 100-160 ° C. Below about 80 ° C, the oxidation of cyclohexane is slow,
At 0 ° C. or higher, the selectivity from cyclohexane to cyclohexanone and cyclohexanol decreases.

The reaction pressure is about 1-20 atm. This pressure is the pressure that keeps the reaction mixture in the liquid phase. Although a higher pressure may be used, there is no particular effect if the pressure is higher than 20 atm.

The reaction time is about 1 to 120 minutes. At about 1 minute or less, the reaction rate of cyclohexane is small, and at about 120 minutes or more, the effect is hardly changed.

The type of the oxidation reaction used in the present invention is a batch type, a continuous type, or a semi-batch type.

As the oxidation reactor, a generally used spherical or cylindrical reactor is used. Although there is no need for a special device inside, there may be a device such as a draft that controls mixing inside, or a device such as a perforated plate that divides the inside into multiple chambers. There may be mechanical stirring devices such as stirring blades. In a continuous or semi-batch reactor, only one or each of cyclohexane and molecular oxygen or a gas containing molecular oxygen is supplied from one or more places. At this time, the supply port may be formed as a nozzle to improve the mixing. The reactor may be connected in one tank or in two or more tanks continuously.

In the present invention, the conversion of cyclohexane is about 1-15.
% Is preferable. If it is less than about 1%, a large amount of energy is required for recovering unreacted cyclohexane.
Above 15%, the selectivity from cyclohexane to cyclohexanone and cyclohexanol is low.

The cobalt catalyst is not limited as long as it is a cobalt compound that is active in cyclohexane oxidation.Carboxylates, sulfonates, organic phosphates, sulfates, nitrates,
Phosphates, complexes, halides, oxides and the like can be mentioned. As the carboxylate, acetate, propionate, 2
-Ethyl hexanoate, octanoate, naphthenate, etc., as the sulfonate, p-toluene sulfonate,
Dodecylbenzenesulfonate and the like, and organic phosphates include monododecylphosphate, didodecylphosphate and the like. Examples of the complex include complexes such as acetylacetone, phthalocyanines, 1,3-bis (2-thiazolylimino) isoindoline, 1,3-bis (2-pyridylimino) isoindoline, porphyrins, and bipyridyl.

In the present invention, the final concentration of the cobalt catalyst refers to the concentration of the cobalt catalyst in the oxidation reactor when the oxidation reactor is a single vessel, and when the oxidation reactor is continuously connected to two or more vessels. The concentration of cobalt in the last oxidation reactor. Actually, the cobalt contained in the supplied cyclohexane or the effluent from the previous oxidation reactor or the effluent from the previous oxidation reactor that has been subjected to a post-treatment such as washing with water is newly supplied. This is a concentration suitable for cobalt. The cobalt concentration in the cyclohexane supplied or in the effluent from the previous oxidation reactor can be measured directly, but can also be obtained indirectly from the analysis of the amount of cobalt contained in the wastewater from the subsequent washing step. it can.

The final concentration of the cobalt catalyst used in the present invention is 0.01 ppm or more and less than 0.1 ppm as cobalt based on the reaction mixture. When the concentration is higher than 0.1 ppm, the amount of by-products generated is large, and the generation ratio of cyclohexanone is low. Concentration is 0.01pp
If it is less than m, the quality of the produced cyclohexanone is poor and cannot be used as a raw material for producing ε-aminocaprolactam. Although the cause is not clear, if the amount of cobalt catalyst is small, the peroxide generated in the oxidation reaction step is not sufficiently decomposed in the oxidation reaction step, so that a large amount of peroxide remains in the oxidation reaction mixture and the peroxide or peroxide is post-treated. It is considered that products such as the acid changed in the above cannot be separated by rectification and remain in cyclohexanone, which may adversely affect the quality of cyclohexanone.

After the oxidation reaction, it may be washed with water to remove impurities such as acids in the oxidation reaction mixture. In addition to water, an aqueous phase after a subsequent alkali treatment or a thin alkali may be used.

After the oxidation reaction, metal treatment or the like may be performed by a known method in order to decompose cyclohexyl hydroperoxide in the oxidation reaction mixture into cyclohexanone and cyclohexanol. That is, the oxidation reaction mixture, a cobalt catalyst exemplified as a cobalt catalyst used in the oxidation reaction step, iron, nickel, vanadium, chromium, molybdenum, ruthenium, the presence of about 0.01 to 100 ppm of a metal compound catalyst such as a salt or complex such as manganese. By treating at a temperature of about 80 to 200 ° C. and a pressure of about 1 to 20 atm, all or part of cyclohexyl hydroperoxide is decomposed into cyclohexanone and cyclohexanol.

In the present invention, after the oxidation reaction, the oxidation reaction mixture may be treated with an alkali. That is, the reaction mixture of the oxidation reaction step, alkali metals such as sodium and potassium,
Treated at a temperature of about 80 to 200 ° C and a pressure of about 1 to 20 atm in the presence of alkali such as hydroxides, carbonates, bicarbonates, etc. of alkaline earth metals such as magnesium and calcium, and alkalis such as ammonia. This neutralizes acids and the like in the reaction mixture in the oxidation reaction step and saponifies esters and the like.

After the oxidation reaction and the above-mentioned post-treatment, the reaction mixture is subjected to removal of unreacted cyclohexane by distillation or the like to obtain a mixture of cyclohexanone and cyclohexanol.

(Effects of the Invention) According to the method of the present invention, the selectivity between cyclohexanone and cyclohexanol, particularly the selectivity for cyclohexanone is high, the oxidation reaction can be performed stably, and high-quality cyclohexanone can be obtained.

(Example) The method of the present invention will be described in detail with reference to examples below, but the present invention is not limited thereto.

The selectivity used in the description is a value calculated from the number of moles of each component using the following equation.

The pH value used for evaluating the quality of the mixture of cyclohexanone and cyclohexanol is such that 5 g of the mixture of cyclohexanone and cyclohexanol is obtained by adding water / methanol (1/1) 9
This is a value obtained by measuring the pH of a solution dissolved in 5 ml at room temperature. If this value is small, the content of acidic impurities is large, so that the quality of cyclohexanone obtained by rectification is deteriorated.

Example 1 Internal volume 1 equipped with a gas inlet tube, a reflux condenser, and a water separator
The oxidation reaction was performed using a liter autoclave made of SUS. As the first oxidation reaction, cyclohexane 5.56
mol, 0.01 mol of cyclohexanone, and 0.32 ppm of cobalt octanoate as cobalt with respect to the whole charged liquid. While stirring at 500 rpm, nitrogen was flowed at a flow rate of 75 / hour, and the temperature was raised to 140 ° C. Nitrogen was changed to an oxygen-nitrogen mixed gas (oxygen: 5 vol%), and the reaction was performed for 1 hour. Thereafter, the oxygen-nitrogen mixed gas was returned to nitrogen, cooled to room temperature, and washed twice with 2 wt% water to obtain an oxidation reaction mixture.

As a second oxidation reaction, the same operation was repeated with the first oxidation reaction mixture and 0.24 ppm of cobalt octoate as cobalt being charged into the oxidation reactor.

Further, as a third oxidation reaction, the second oxidation reaction mixture was charged into an oxidation reaction apparatus, and the same operation was repeated. No cobalt catalyst was charged, but due to the cobalt contained in the second oxidation reaction mixture, the charged mixture contained 0.03 ppm cobalt. The resulting oxidation reaction mixture was cyclohexyl hydroperoxide 1.
It contained 10% by weight.

The oxidation reaction mixture was alkali-treated by a conventional method, and cyclohexane was distilled off to obtain a mixture of cyclohexanone and cyclohexanol. The pH value of the resulting mixture is 7.0
Met. The conversion of cyclohexane is 5.9 mol%,
Selectivity for cyclohexanone and cyclohexanol is 71.7
The yield of mol% and cyclohexanone was 0.74.

Example 2 The same operation as in Example 1 was carried out except that in the first and second oxidation reactions, 0.32 ppm and 0.08 ppm of cobalt octanoate were charged as cobalt, respectively. In the third oxidation reaction, no cobalt catalyst was charged.
Due to the cobalt contained in the second oxidation reaction mixture, the charged reaction mixture contained 0.02 ppm cobalt. The oxidation reaction mixture contained 1.45% by weight cyclohexyl hydroperoxide. The pH value of the mixture of cyclohexanone and cyclohexanol obtained from the oxidation reaction mixture is
It was 6.9.

The conversion of cyclohexane is 5.8 mol%, the selectivity of cyclohexanone and cyclohexanol is 71.5 mol%,
The production ratio of cyclohexanone was 0.83.

Example 3 The same operation as in Example 1 was performed, except that cobalt octanoate of 0.15 ppm, 0.08 ppm, and 0.07 ppm as cobalt was charged in the first, second, and third oxidation reactions, respectively. . In the third oxidation reaction, the charged reaction mixture contained 0.09 ppm of cobalt due to the cobalt contained in the second oxidation reaction mixture.

The oxidation reaction mixture is cyclohexyl hydroperoxide
It contained 0.72% by weight. The pH value of the mixture of cyclohexanone and cyclohexanol obtained from the oxidation reaction mixture is 7.
It was five.

The conversion of cyclohexane is 5.9 mol%, the selectivity of cyclohexanone and cyclohexanol is 71.6 mol%,
The production ratio of cyclohexanone was 0.74.

Example 4 The same operation as in Example 1 was performed except that cobalt octanoate of 0.17 ppm, 0.07 ppm, and 0.07 ppm as cobalt was charged in the first, second, and third oxidation reactions, respectively. . In the third oxidation reaction, the charged reaction mixture contained 0.09 ppm of cobalt due to the cobalt contained in the second oxidation reaction mixture.

The oxidation reaction mixture is cyclohexyl hydroperoxide
0.82% by weight. The pH value of the mixture of cyclohexanone and cyclohexanol obtained from the oxidation reaction mixture is 7.
It was five.

The conversion of cyclohexane is 5.9 mol%, the selectivity of cyclohexanone and cyclohexanol is 71.5 mol%,
The production ratio of cyclohexanone was 0.72.

Comparative Example 1 The operation was performed in the same manner as in Example 1 except that 0.17 ppm and 0.07 ppm of cobalt octoate were charged as cobalt in the first and second oxidation reactions, respectively. In the third oxidation reaction, no cobalt catalyst was charged.
Even with the cobalt contained in the second oxidation reaction mixture, the charged reaction mixture only contained 0.007 ppm of cobalt.

The oxidation reaction mixture is cyclohexyl hydroperoxide
It contained 1.64% by weight. The pH value of the mixture of cyclohexanone and cyclohexanol obtained from the oxidation reaction mixture is 5.
Since it was 3, cyclohexanone obtained by rectification cannot be used as a raw material for producing ε-aminocaprolactam.

The conversion of cyclohexane is 6.0 mol%, the selectivity of cyclohexanone and cyclohexanol is 71.1 mol%,
The production ratio of cyclohexanone was 0.84.

Comparative Example 2 The operation was performed in the same manner as in Example 1 except that 0.32 ppm, 0.24 ppm, and 0.18 ppm of cobalt octoate were charged as cobalt in the first, second, and third oxidation reactions, respectively. . In the third oxidation reaction, the charged reaction mixture contained 0.20 ppm of cobalt due to the cobalt contained in the second oxidation reaction mixture.

The oxidation reaction mixture is cyclohexyl hydroperoxide
It contained 0.59% by weight. The pH value of the mixture of cyclohexanone and cyclohexanol obtained from the oxidation reaction mixture is 7.
It was five.

The conversion of cyclohexane is 5.9 mol%, the selectivity of cyclohexanone and cyclohexanol is 71.0 mol%,
The production ratio of cyclohexanone was 0.68.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C07C 27/12 310 C07C 35/08 C07C 49/403

Claims (1)

(57) [Claims] 1. A process for producing cyclohexanone and cyclohexanol by oxidizing cyclohexane with molecular oxygen or a gas containing molecular oxygen in a liquid phase in the presence of a cobalt catalyst, wherein the final concentration of the cobalt catalyst is cobalt. A process for producing cyclohexanone and cyclohexanol, wherein the content is 0.01 ppm or more and less than 0.1 ppm.