CS244986B1 - Process for producing cyclohexanol and cyclohexaaone - Google Patents

Abstract

Cyclohexanol and cyclohexanone are produced by oxidizing cyclohexane in the liquid phase with molecular oxygen at a temperature of 140 to 170° Celsius and a pressure at which the liquid phase is still preserved in the presence of a catalyst, which are salts of cobalt or cobalt and chromium. The essence of the solution is that a cocatalyst containing lithium in the form of Li+ cation is added to the reaction system, while the molar ratio of metals Li:Co is 1:25 to 0.3. Cyclohexanol and cyclohexanone are used as alcohol solvents or for the production of adipic acid and polyamide fibers.

Description

The present invention relates to a process for the catalyzed oxidation of cyclohexane in the liquid phase of nacyclohexanol and cyclohexanone.

Cyclohexanone as an intermediate in the production of caprolactam is prepared in either bulk or cyclohexane in bulk industrial processes. In cyclohexane processes, cyclohexane is oxidized in the liquid phase with air or oxygen at temperatures above 130 ° C and pressures at least as high as the cyclohexane vapor pressure at the appropriate temperature. The reaction is carried out in the absence of solvent. As the main oxidation intermediate, cyclohexane hydroperoxide is formed, which decomposes into cyclohexanol and cyclohexanone in the presence of metal catalysts. In that the oxidation takes place at higher temperatures, from 150 to 160 [deg.] C., the short-chain sequence is short, and so is the amount of cyclohexanol and cyclohexanone formed by the termination of the cyclohexyl peroxy radicals. The rate and direction of decomposition of the cyclohexane hydroperoxide are greatly influenced by the oxygenated reaction products, especially cyclohexanone and carboxylic acids. The carboxylic acids accelerate the radical decomposition of the hydro-peroxides. The major influence on the kinetics of peroxide resolution has salts and complexes of transition metals which significantly increase the rate of decomposition. This leads to a considerable reduction in the maximum concentration of hydro-peroxides in the cyclohexane oxidation process. In addition to cyclohexanol and cyclohexanone, for the decomposition of cyclohexane hydroperoxide, they also form other compounds, e.g. Although the mechanism of decomposition of cyclohexanhydroperoxide is complicated and depends on both the reaction conditions and the structural material of the reactor, they are cyclohexanol and cyclohexanone major products. However, these substances are still very easily oxidized and therefore, when oxidizing cyclohexane in industrial conditions, the conversion is limited to 4 to 10%. In continuous oxidation, the cascade coupling of the reactors is used, thereby suppressing subsequent reactions. Oxidation of cyclohexanol with molecular oxygen proceeds substantially faster than cyclohexane oxidation, whereby the C-bond in the geminal position of the -OH group is attacked. Kinetic data suggest that it is difficult to conduct cyclohexane oxidation only to the degree of oxidation-desirable intermediates of cyclohexanol and cyclohexanone, which are in practice desirable oxidation target products. Obtaining higher yields of these products at higher selectivity or conversion can be achieved by using suitable catalysts, optionally boronic acid or esters thereof. The use of various catalysts and catalytic systems, which are actively and selectively for the oxidation of cyclohexane, is described in the patent and literature literature. Thus, we use catalysts containing nickel, molybdenum, chromium and vanadium to describe Jap. U.S. Pat. No. 5,771,438, U.S. Pat. Nos. 1,005,888 and 929,213, further disclose the use of co-complexes with phosphine ligands (Eur. Pat. No. 63,931; U.S. Pat. in U.S. Pat. No. 4,341,907, Co (BuCHetCO2) 2 catalysts combined with pyridine or 4-cyanopyridine, or treatment of an oxidation mixture with CoSO4 and NaOH (Eur. Pat. Appl. 92 867). and, in the presence of boron compounds, also converts the formed cyclohexanol tricyclohexylborate to prevent further oxidation of the alcohol.

The above drawbacks can be avoided by the production of cyclohexanol and cyclohexanone by oxidation of cyclohexane in a liquid phase with a molecular oxygen at 140-170 ° C and such that a liquid phase is maintained in the presence of a cobalt or cobalt salt and a chromium-based addition of a lithium-containing cocatalyst in the form of a cation of Li 1 ', wherein the molar ratio of Li: Co is 1: 25 to 0.3 is added to the reaction system. Since either the highest selectivities of the formation of the desired products of cyclohexanol and cyclohexanone are achieved at low cyclohexane conversions, less than 10%, it is more preferable to conduct the process continuously in the reactors involved. It is important to ensure intensive contact of the reacting gaseous liquid phase. substances acting as inhibitors of radical reactions, for example sulfur compounds, phosphorus compounds, some nitrogenous compounds and the like. The metal catalysts are fed into the reactor in a reaction medium soluble form. Most commonly, these are salts of aliphatic and naphthenic acids or acetylacetonates. The concentration of the cobalt catalyst is selected according to the reaction conditions, but is usually low, about 2 to 5 ppm. The inactivating salts are influenced by the catalytic activity of the cobalt catalyst as well as by catalysts prepared from a mixture of cobalt and chromium salts. First, the concentration of peroxide compounds is reduced and the ratio of cyclohexanone formed to cyclohexanol is increased. With certain molar ratios of catalyst and lithium cocatalyst, the formation of secondary liquid products is also suppressed with unchanged cyclohexane and oxygen consumption rates. .

Claims (4)

EXAMPLE 1 152 g of cyclohexane and 2.7 ppm of cobalt in the form of the fatty acid salt of Ca to C10 were added to a pressure reactor of stainless steel equipped with air intake, condenser, heating, cooling and temperature control, air pressure and flow. After pressurizing the reactor to 1.0 MPa and letting air flow at 185 cm5. min "The reactor was heated to 155 ° C with vigorous stirring of the reaction mixture. The gaseous effluent from the reactor through the condenser and the flow meter was fed to continuous oxygen and carbon dioxide analyzers. At some time intervals samples of the oxidation mixture were taken from the reactor. The content of cyclohexanol, cyclohexanone and some by-products was determined by gas chromatography and the peroxide content was expressed by iodomeric titration, the content of cyclohexyl hydroperoxide was determined. in the 35 minute reaction The ratio of cyclohexanone to cyclohexanol formed in the first 50 minutes of the reaction was almost constant at 72. After 30 minutes of oxidation, 0.079 carbon dioxide and 0.187 g of carbon dioxide were obtained over 50 minutes. % by weight of cyclohexanol and 1.10% by weight of cyclohexanone 2 The conditions of the same alcohol in Example 1 as a cobalt catalyst were added lithium acetylacetonate in an amount corresponding to a common Li: Co ratio of 1: 5. Compared to Example 1, for 30 min. the reaction consumed 5.8% more oxygen. The maximum peroxide content of the reaction mixture was reduced to 0.45% by weight, and the ratio of cyclohexanone to cyclohexanol produced was increased to 0.82. After 30 minutes of reaction, 0.074 g was formed and 0.140 g of carbon dioxide was obtained in 50 minutes. Example The procedure and conditions are the same as in Example 1, but the cobalt catalyst in an amount of 2.7 ppm was added with chromium acetylacetoate and lithium octanoate in amounts corresponding to the Co: Cr molar ratio: Li = 15: 24: 1. After 30 minutes the oxidation consumed practically the same amount of oxygen as in Example 1, while the reaction mixture contained 1.44 wt. cyclohexanone and 1.57% by weight of cyclohexanol, indicating that the ratio of these compounds increased to 0.87. During this reaction, 0.063 g of carbon dioxide was liberated. The maximum peroxide content of the reaction mixture was 0.58% by weight. Example The procedure and conditions of Example 1, but to a cobalt catalyst of 2.4 ppm, were added chromium and lithium in the form of aliphatic carboxylic acid salts of Ca to C10 in an amount corresponding to the molar ratio of Co: Li: Cr = 1: 1: 0.039. By using said mixed catalyst, the maximum amount of peroxygen formed was only 0.44%. wt. and within 50 min. The reaction produced only 0.109 g of carbon dioxide at practically the same amount of reacted oxygen as in Example 1. The cyclohexane, cyclohexane, cyclohexanol and cyclohexanone oxidation products were used as solvents or for the production of adipic acid and polyamide fibers. BACKGROUND OF THE INVENTION The process for producing cyclohexanol and cyclohexanone by oxidizing cyclohexane in a liquid phase with molecular oxygen at a temperature of 140 to 170 and a pressure to maintain a liquid phase, in the presence of a catalyst, is a salt of cobalt or cobalt and chromium. of a lithium in the form of a Li + cation, the molar ratio of Li: Co metals is 1: 25 to 0.3.