CS274371B1 - Method of cyclohexanole and cyclohexanone mixture production - Google Patents

Abstract

The solution concerns a method of production of cyclohexanol and cyclohexanone based on oxidation of cyclohexane by molecular oxygen and on selective decomposition of cyclohexyl peroxide by mixed metallic catalysers. The principle of the solution consists in the fact that the oxidation process is catalysed by complete quantity of cobaltous catalyser and by at most 95 percent by weight of chromium and lithium salts of the whole quantity, soluble in the reaction environment. The remaining amount of chromium and lithium salts is used for selective decomposition of hydroperoxides present in oxidation product, which is performed at temperature of 60 to 125 degrees C in the processes of distillation separating of non-reacted cyclohexane from the reaction mixture.

Description

The invention relates to a process for the production of cyclohexanone and cyclohexanol based on the oxidation of cyclohexane by molecular oxygen and the selective decomposition of cyclohexyl hydroperoxide by mixed metal catalysts.

Cyclohexanone, an important intermediate for the production of caprolactam ea, is industrially produced from cyclohexone or phenol by hydrogenation and subsequent dehydrogenation of the resulting cyclohexanol. The cyclohexane is oxidized by air at a pressure to maintain both the liquid phase and to ensure the reaction heat circuit by evaporating the cyclohexone.

The reaction temperature depends on whether a metal catalyst is used or the reaction proceeds in the absence of the catalyst. Catalyst reactions take place at temperatures of 150-170 ° C with the amount of metal catalyst being very low, less than 8 ppm. An important requirement in the oxidation of cyclohexone is to achieve a high selectivity of the reaction. Due to the typical radical mechanism of oxidation of eyclohexone, this is ensured in practice by the fact that the reaction takes place only at low conversions of eyclohexone, usually less than 4-6%. Even they arise! Subsequent and side reactions in the amount of up to 25%. The main oxidation product is always a mixture of cyclohexanol and cyclohexanone. The ratio of these substances in the reaction mixture depends mainly on the type of metal catalyst. When using a cobalt catalyst, this ratio is about 2. In addition to the oxygen products mentioned, the reaction mixture also contains cyclohexyl hydroperoxide. Its concentration in the reaction mixture at the reactor outlet is dependent on several factors and ranges from 0.7% by weight. up to 1.2 wt. The concentration value is significantly influenced by the type of reactor used for oxidation, the composition and concentration of the metal catalyst, and the manner of its addition to the reactor during oxidation.

Since the decomposition of cyclohexyl hydroperoxide produces cyclohexanol and cyclohexanone is essential to ensure a high selectivity of its decomposition to the compounds from the point of view of the resulting selectivity of the production process. The thermal decomposition of this hydroperoxide is less selective than catalytic. The decomposition takes place during the working up of the reaction mixture, especially in the step in which the unreacted cyclohexane of the oxidation products is distilled off. In this separation, there must be no concentration of cyclohexyl hydroperoxide and therefore a process flow must be conducted to decompose the hydroperoxide.

The above drawbacks of producing a mixture of cyclohexanol and cyclohexanone based on oxidation of cyclohexane by molecular oxygen at temperatures of 150-165 ° C and a pressure of 0.8-1.0 MPa in the presence of catalysts based on a mixture of cobalt, chromium and lithium salts are eliminated according to the invention. which is characterized in that the process of oxidation, catalyze the whole amount of the cobalt catalyst and a maximum of 95-imino salt content of Cr ^'+ and L ^h soluble in the reaction medium, the remaining amount of the salts of Cr ^{J +} and Li is used for the selective decomposition of hyóroperoxidov contained with the oxidation product, which is carried out at temperatures of 60 to 125 ° C in processes of distillation of unreacted cyclohexane from the reaction mixture.

The amount of mixed catalyst used in the description process is 0.1 to 10 ppm based on the amount of liquid cyclohexane in the oxidation reactor. 2 of this amount is 30 already SO mass. cobalt salts and the remainder are Cr CrO Li ⁺ salts. The two metal ions in the form of salts which are soluble in the reaction system are used in a molar ratio of 100: 1 to 5: 1. They are added to the exidation reactor, but part is added to the rectification column, where unreacted is separated. cyclohexane from oxidation products. Any column or column can be added to the column. In the presence of these mixed catalysts, there is a selective decomposition of cyclohexyl hydroperoxide, whereby the ratio of formation of cyclohexanone to cyclohexanol is increased relative to thermal or decomposition in the presence of cobalt catalyst and the concentration of this hydroperoxide in the distillation outlet is reduced.

Z · I columns. Y the presence of Cr- ⁷ and Li salts does not support the course of subsequent non-caloric

CS 274371 B1 corresp. other reactions. The advantages of the process of preparing a mixture of cyclohexanol and cyclo hexanone according to the invention can be seen from the following examples.

Example 1

A scrubber is pumped into a reactor consisting of six cascade members

294.2 t / h of circulating cyclohexane, of which 293.2 t / h of cyclohexane, Ο, 3θ3 t / h of cyclohexanol, 0.206 t / h of cyclohexanone and 0.294 t / h of water. The liquid flowing through the reactor was bubbled through the air at 22.8 t / h. The oxidation is carried out at an average temperature of 157 ° C under the catalytic action of cobalt naphthenate, which is added in the form of a solution in cyclohexane containing 1.03 wt. % cobalt. The solution of cobalt catalyst is fed subsequently, the first member of the cascade 40 dm ^ ε in the second through fifth member of the cascade of the same at 6 hours dra ^ "\ La šieateho member of the cascade were added to 20 dm ^-1 h ^ O, 91% by weight. solution of chromium lithium salts in cyclohexane. The molar ratio of said metals is 17: 1. At the outlet of the reactor, the oxidation mixture contains cyclohexanol and cyclohexanone in a weight ratio of 1.45, where after separation of unreacted cyclohexane in a rectification column in which the temperature of 118 ° C remains in the distillation residue to 0, 67% wt. cyclohexyl.

Example 2

The procedure, conditions and amounts as in at? Ilade 1 except that the Cr-salt ^ ^+, and Li ⁺ in the form of 1.07% by weight. of the solution in cyclohexane are added to the fifth and sixth members of the oxidation reactor cascade in amounts after 6 dm h. The molar ratio of the metals is 59: 1 to the rectification column used but the separation of unreacted cyclohexane from the reaction mixture in which the temperature in the boiler is 109 ° C with a salt solution is added the Cr VI ⁺ and Li ⁺ at 15 h dm ^ ^- ^. The distillation residue contains 0.32% by weight of cyclohexyl hydroperoxide, the cyclohexanol to cyclohexanone ratio by weight being 1.40.

Claims (2)

OBJECT OF THE INVENTION Process for producing a mixture of cyclohexanol and cyclohexanone based on oxidation of cyclohexane by molecular oxygen at temperatures of 150 to 170 ° C and a pressure of 0.8 to 1.0 MPa in the presence of a catalyst based on a mixture of cobalt, chromium and lithium salts at 0.1 to 10 ppm based on the amount of liquid cyclohexane in the oxidation reactor, characterized in that the oxidation process is catalyzed by the total amount of cobalt catalyst and at most 95 wt. % of the chromium and lithium salts of the total amount soluble in the reaction medium, the remaining amount of chromium and lithium salts being used to selectively decompose the hydroperoxides present in the oxidation product at 60 to 125 ° C in the processes of distillation of unreacted cyclohexane from the reaction mixture.