CS196648B1 - Method of preparing hydroperoxides - Google Patents

Description

The present invention relates to a process for the preparation of hydroperoxides by catalyzing the oxidation of alkylaromatic and / or alkylaromatic compounds. cycloalkylaromatic hydrocarbons with molecular oxygen in the liquid phase.

Organic hydroperoxides are prepared predominantly by direct oxidation of hydrocarbons with oxygen or air. The reaction takes place in the liquid phase and proceeds through a free-radical mechanism. In order to increase the oxidation rates, substances which initiate a radical reaction are added to the starting hydrocarbons. Most often, they are thermally unstable organic compounds such as azo compounds, peroxides, hydroperoxides. Their initial concentrations are up to 5%. Higher initiator concentrations are not used because the velocities are already high enough and the selectivity of the reaction is also reduced. The hydrocarbon conversion is limited, and the oxidation is interrupted when the hydroperoxide content in the mixture reaches 20 to 35%. At higher peroxide concentrations, induced radical decomposition of the hydroperoxide under the reaction conditions leads to methanol, acetophenone, dimethylphenylcarbinol and methylstyrene, for example in the case of cumene hydroperoxide. Increasing the concentration of side products causes a reduction in the selectivity of the reaction. During production, care is taken that the hydroperoxide is not exaggerated anywhere, which would result in little explosion. Therefore, it is oxidized in a counter-current vertical or horizontal reactor inside a perfectly cooled reactor.

. These drawbacks are substantially eliminated by the process for the preparation of hydroproxides by oxidation of alkylaromatic or cycloalkylaromatic hydrocarbons with molecular oxygen in the liquid phase, which consists in the use of transition metals or transition metals or lanthanides in the form of polynuclear complexes, physically or chemically bound to the catalysts. inorganic carriers.

The effect of the catalysts can be increased by the presence of small concentrations of thermally low stable substances such as azo compounds, peroxides, hydroperoxides in the starting hydrocarbon. This does not reduce the overall process selectivity, but the oxidation rates increase substantially. The oxidation of the hydrocarbons takes place in well-cooled reactors with intense contact of the oxidizing gas and the liquid. The oxidation temperatures are dependent on the oxidizing hydrocarbon. Oxygen or air may be used as the oxidizing agent. To neutralize the acidic by-products which catalyses the heterolytic decomposition of peroxides to phenol, bases may be used to neutralize them. The choice of alkylaromatic or cycloalkylaromatic hydrocarbons is practically not limited. It is essential that the alkylaromatic hydrocarbon contain at least one hydrocarbon chain at the core in which the hydrogen atom is bonded to the tertiary carbon atom. In the case of cycloalkylaromatic hydrocarbons where the cyclanyl ring is oxidized, this condition is generally met, Example 1 '

A 150 ml glass reactor with vigorous liquid stirring is filled with cumene containing 0.1% w / w. cumene hydroperoxide as initiator. The mixture is oxidized at 110 ° C with oxygen. After 475 minutes, the reaction was stopped and the oxidation mixture was analyzed. Analysis revealed that it contained 27.1% by weight of cumene hydroperoxide, 2.25% by weight of cumyl alcohol and traces of acetophenone. The selectivity of the reaction was 92.4%.

Example 2

The procedure was the same as in Example 1, but the oxidation mixture contained a complex catalyst containing 0.95% iron and 0.15% media at a concentration of 0.23% by weight. After 400 minutes oxidation was formed

29.3% by weight of cumene hydroperoxide and 1.67% by weight of cumyl alcohol. The selectivity of the reaction was 94.6%.

Example 3

Conditions as in Example 2, _x, but the catalyst used is a complex of lead at a concentration of 0.27% by weight. The selectivity of the reaction was 92.3%.

Example. .4

It was oxidized with vigorous stirring

SUBJECT

Process for the preparation of hydroperoxides by liquid-phase oxidation of alkylaromatic or cycloalkylaromatic hydrocarbons with molecular oxygen, characterized in that the catalysts used are transition metals or transition metals or lanthanides in the form of polynuclear complexes, physically or chelated at 115 ° C. oxygen. To initiate the reaction, cumene hydroperoxide was initially added in an amount such that its concentration in the mixture was 0.3% by weight. After 370 minutes of oxidation, cyclohexylbenzene hydroperoxide was formed in an amount of 2.8% by weight.

Example 5

Conditions as in Example 4, but the antimony complex was added as a catalyst in an amount of 0.25% by weight. After 560 minutes of oxidation, cyclohexylbenzene hydroperoxide was formed in an amount of 10.1% by weight.

The advantages of the process for the preparation of hydroperoxides by catalytic liquid-phase oxidation of alkylaromatic or cycloalkylaromatic hydrocarbons with molecular oxygen are, inter alia, that the catalysts used in the process of the invention are chemically stable, readily storable and non-flammable substances. Solutions of peroxides and hydroperoxides in inert organic solvents at concentrations up to 50% by weight do not decompose even at temperatures above 100 ° C. They catalyze the oxidation of hydrocarbons to the corresponding hydroperoxides, increasing both reaction rates and selectivity of the reaction. Being heterogeneous forms of catalyst in their use, the advantage is that they largely remain in the oxidation reactor even after the oxidation mixture has been discharged, so that only one amount of fresh catalyst is used in the individual oxidation cycles to supplement losses from the catalyst. previous cycles.

Claims (2)

bonded to organic or inorganic carriers. 2. A process for the preparation of hydroperoxides according to claim 1, characterized in that the oxidation reaction is initiated by thermally poorly stable compounds such as azo compounds, peroxides, hydroperoxides.