CS224913B1 - The preparation of octanals by means of the isomerization of the octane-1,2-oxides under the catalytic action of the mineral acid - Google Patents

Description

BACKGROUND OF THE INVENTION The present invention relates to a process for the preparation of octane &

According to PV 7270, octanals can be prepared by isomerization of the corresponding octane-1,2-oxides in the presence of excess aqueous sulfuric acid solution at elevated temperature. Namely, the preparation of 2-ethylhexanol in water is described. 19.5% yield, and 2,4,4-trimethylpentanol in 5-5.2% yield; other eu products include the corresponding alkenols, alkanoids, alkylated 1,3-dioxolanes and other minor products. The presence of water in the system reduces the yield of the desired octanols, moreover the reactions take place in a liquid biphasic system requiring vigorous stirring. The product should be separated from the mixture by distillation.

The above disadvantages are substantially eliminated by the process for the preparation of octanes by the isomerization of octane-1,2-oxides under the catalytic action of a mineral acid according to the invention, characterized in that the mineral acid, preferably phosphoric acid or sulfuric acid, is deposited on silica gel and freed water, wherein the molar ratio of octane 1,2-oxide: mineral acid is 10: 1 to 300: 1, preferably 15: 1 to 100: 1, and isomerization takes place at a temperature of 20 to 1 * 50 ° C, in the presence of an organic solvent

224,913 atoms in the molecule equal to 5 to 9, which is an alkane, cyclone, aromatic, alkylaromate or a mixture of up to 100% octane-1,2-oxide conversion.

The catalyst may be reused after separation from the reaction mixture.

Mineral acids contain a certain proportion of water and are insoluble in the reaction system, adhere to the walls and give lower product yields. of water is applied to silica gel and dried at a temperature of 160 ° C to 0 ° C. The amount of phosphoric acid and the particle size of the eilicagel must be determined experimentally β in order not to reduce the flowability of the catalyst. phosphoric acid on silica gel, 0.08 to 0.16 mm, maintaining an anhydrous condition; however, it has strong hygroscopic properties and must therefore be weighed quickly and most effectively transferred to a pre-heated flask and immediately poured into the solvent. The catalyst thus prepared does not adhere to the stiff ^{from our} flasks and, with stirring, is well dispersed in the mixture and yields high octanol yields. An insufficient amount of catalyst results in a prolonged reaction time and gives the possibility of the formation of downstream products.

The completion of the reaction is generally signaled by complete conversion of octane-1,2-oxide, which also facilitates product isolation, and in some cases peak product content can be used practically without further treatment for the purpose.

During the reaction, and especially after the octane-1,2-oxide has reacted, conversions of reaction by-products such as octenols and alkylated 1,3-dioxolane into the desired octanal have been observed, which slightly increases yields. On the contrary, the formation of bituminous substances is not excluded in case of inappropriate choice of reaction conditions, especially

- 3,224,913 prolongation of reaction time resulting in yellowing of the reaction mixture · At temperatures up to 120 ° C the product in the reaction system is relatively stable, which allows its distillation to be separated without special demands on operational equipment. , it is advisable to add octane-1,2-oxide in portions for better control of the thermal regime.

Solvents which have proven to be the best are available hydrocarbons or mixtures thereof which, when refluxed, ensure the anhydrous system; Polar solvents such as water, ether, alcohols have not proven to be useful because some of the inorganic acid fixed on silica gel passes into them.

By using the catalyst carefully after filtering it out of the reaction system, the same result is obtained, and the course of the reaction is the same. The reused catalyst is slightly black but does not lose activity and retains the original grain and flowability. The formation of resins causing blackening and bonding of the catalyst depends on the temperature and the possible presence of alkeneic impurities which polymerize on the catalyst surface and, if more are formed, bond the catalyst particles.

The possibilities of the method of the invention are illustrated in the following examples:

Examples 1 to 33

In a three-necked 2-50 ml Erlenmeyer flask with a magnetic stirrer with heating, thermometer, reflux condenser and sampling equipment, the catalyst, solvent is mixed and isomeric octane-1,2-oxide is added after tempering. Neutralize the sample with an aqueous solution of sodium bicarbonate, dry with anhydrous sodium sulfate, analyze by GLC, and evaluate by direct calibration.

The conditions of experiments 1 to 33 and the results of the analyzes are shown in Table 1.

- 4,224

In experiments 1 to 2-5, where 2,4,4-trimethylpentane-1,2-oxide was used, the reaction product contains these;

octanal-2,4,4-trimethylpentanal, octenols 2,4,4-trimethyl-2-penten * 1-ol and

4,4-dimethyl-2-methylenepentaa-1-ol, alkylated 1,3-dioxolane ⁵⁵ 2- (1,3,3 * trimethylbutyl) -4-methyl * 4 * (2,2-dimethylpropyl) -1,3-dioxolane.

In experiments 26-33, where 2-ethylhexane-1,2-oxide was used, the reaction products were:

octanal = 2-ethylhexanal, octenols ⁼ 2-butyl-2-butene-1-ol and

2-ethyl-2-hexen-1-ol, alkyl 1,3-dioxolane = 2- (1-ethylpentyl) -4-ethyl-4-butyl-1,3-dioxolane.

In Experiment 9, the catalyst separated from Experiment 8 was used, in Experiment 10, the catalyst from Experiment 9 was used.

In experiments 17, 2-5 and 33, the liquid hetane catalyst formed a limited, miscible β organic liquid phase.

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Claims (1)

A process for the preparation of octanes by isomerization of octane-1,2-oxides under the catalytic action of a mineral acid, characterized in that the mineral acid, preferably phosphoric acid or sulfuric acid, is deposited on silica gel and dehydrated with water, the molar ratio of octane 1,2-oxide The mineral acid is 10: 1 to 300: 1, preferably 15: 1 to 100: 1 and isomerization takes place at a temperature of 20 to 150 ° C, preferably θθ to 140 ° C, in the presence of an organic solvent which is an alkane, eyclan , aromatic, alkylaromate or mixtures thereof with a number of carbon atoms in the molecule of -5 to 9, to 100% conversion of octane-1,2-oxide.