JPS58121239A - Preparation of caprylic acid - Google Patents

Abstract

PURPOSE:To prepare caprylic acid useful as a raw material of metallic soap, desiccant, lubricating oil, etc., economically, in an industrial scale, by isomerizing 2,7-octadien-1-ol, hydrogenating the product, and oxidizing the hydrogenated product with oxygen in liquid phase. CONSTITUTION:Caprylic acid is prepared in high yield, by (1) isomerizing 2,7- octadien-1-ol to 7-octen-1-al in the presence of a catalyst selected from copper- based catalysts and chromium based catalysts, preferably at 130-220 deg.C, (2) hydrogenating the compound in the presence of known hydrogenation catalyst and hydrogen, and (3) oxidizing the resultant n-octylaldehyde with oxygen in a liquid phase in the presence of an oxidation catalyst preferably at 30-90 deg.C. The process is suitable for the industrial operation, because the starting material can be prepared from butadiene which is available easily at a low cost, the process consists of simple procedures, and the obtained caprylic acid has extremely high purity.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to the isomerization of a novel 7-octadiene of caprylic acid suitable for commercial practice to give 7-octen-1-al, and the hydrogenation of 7-octen-1-al. This invention relates to a method for producing caprylic acid, which comprises converting it into n-octylaldehyde and then oxidizing this.

Caprylic is a substance useful as a raw material for metal soaps, desiccants, lubricants, etc. Caprylic acid is found in small amounts in natural glycerides, but extremely complicated steps are required to separate and obtain it, and caprylic acid has not yet been mass-produced on an industrial scale. Aliphatic monocarboxylic acids are generally produced by combining an oxo reaction and an oxygen oxidation reaction, but 1-heptene, which is extremely difficult to obtain, is used as a starting material to produce caprylic acid. Due to the necessity, this method cannot be adopted for the production of caprylic acid. Under these circumstances, as a C-monocarboxylic acid, 2-ethylhexanoic acid, which has poor decomposition by microorganisms and poor oxidative stability, is currently used as a substitute for caprylic acid.

Previously, the present inventors discovered that 2゜7-octarenin-1-ol could be industrially advantageously produced by reacting butadiene and water in the presence of a palladium complex catalyst (Japanese Patent Application Laid-Open No. 1983-1993). (Refer to Japanese Patent Publication No. 138129) 0 Based on this background, the present inventors have conducted intensive studies on methods for synthesizing various useful derivatives using 2,7-octarenin-1-ol as the starting material I. As a result, 2,7-octarenin-1-ol is isomerized in the presence of a catalyst selected from the group consisting of a copper-based catalyst and a chromium-based catalyst, and the resulting 7-octen-1-al is The present inventors have discovered that caprylic acid can be produced in high yield by hydrogenating it to n-octylaldehyde in the presence of an oxidation catalyst and then oxidizing it with oxygen in the liquid phase in the presence of an oxidation catalyst, and have completed the present invention. This method is suitable for industrial implementation because 2,7-octarenin-1-ol is produced from easily available and inexpensive butadiene, the process is simple, and the purity of caprylic acid is extremely high. It has many advantages.

The copper-based catalyst and chromium-based catalyst used as a catalyst in the isomerization reaction of 2,7-octarenin-1-ol according to the method of the present invention include reduced copper, Raney copper, copper zinc oxide, copper chromium oxide, zinc Examples include chromium oxide. The above-mentioned metal oxide catalysts are commercially produced and can be easily obtained.
It can also be produced according to the method described on pages 5-567 (February 25, 1967, published by Chijinshokan Co., Ltd.). The above literature describes, for example, an example of producing copper chromium oxide by adding chromium trioxide to powdered or paste copper oxide, adding an appropriate amount of water to it, crushing the mixture for several hours, and then allowing it to dry. Are listed. These catalysts may be partially modified with other metal components selected from tungsten, molybdenum, rhenium, zirconium, manganese, titanium, iron, barium, and the like. Further, the catalyst supported on a carrier such as alumina, wrinkle strength, diatomaceous earth, etc. can also be used.

These catalysts may be used alone, or in combination of two or more. Catalyst activity may be improved if the catalyst is previously treated with hydrogen prior to use. When the reaction is carried out in a liquid phase, the catalyst is used at a ratio of α1-20]E amount percent to the reaction mixture in metal terms, and an appropriate amount of a sulfur compound, antimony compound, bismuth compound, or phosphorus compound is added to the reaction system. , when the isomerization reaction of 2,7-octarenin-1-ol is performed with the catalyst partially poisoned by the coexistence of a nitrogen compound, etc., the selectivity of 7-octen-1-al improves. There is. Is the sulfur compound sulfur, sodium sulfate, etc.? Examples of antimony compounds include antimony oxide, bismuth compounds include bismuth oxide, phosphorus compounds include phosphoric acid and triphenylphosphine, and nitrogen compounds include pyridine and aniline. The isomerization reaction of 2,7-octarenin-1-ol is preferably carried out under an inert gas atmosphere under reaction conditions such as nitrogen gas, carbon dioxide gas, helium gas, argon gas, etc. Part or all of it may be replaced with hydrogen gas. However, when the reaction is carried out in the presence of hydrogen gas, it is better to keep the partial pressure of hydrogen gas at 10 atmospheres or less. When the partial pressure of hydrogen gas exceeds 10 atmospheres, the rate of hydrogenation reaction increases and the selectivity of 7-octen-1-al decreases.

The reaction temperature is 100-250℃, especially 150-220℃
Select from the range of n. The reaction can be carried out in a stirred reactor, a bubble column reactor or a packed column reactor in the liquid or gas phase in a continuous or batchwise manner.

When the reaction is carried out in a liquid phase, the raw material 2,7-octarenin-1-ol or the product 7-octen-1-7-ol can also function as a solvent. This reaction can also be carried out using other organic solvents that are inert under the reaction conditions. Usable organic solvents include saturated aliphatic hydrocarbons such as hexane, octane, decane, and liquid paraffin, saturated alicyclic hydrocarbons such as cyclohexane and methylcyclohexanato, and aromatic solvents such as benzene, toluene, xylene, and biphenyl. Hydrocarbons, diimpropyl ether, dibutyl ether, dioctyl ether, diphenyl ether, tetrahydrofuran, diethylene glycol diethyl ether,
Examples include ethers such as polyethylene glycol dimethyl ether, alcohols such as ethanol, butanol, octatool, ethylene glycol, glycerin, and polyethylene glycol.

Since 7-octen-1-al produced in this reaction has a lower boiling point than 2.7-octarenin-1-ol, which is the reaction raw material, the reaction is carried out while distilling 7-octen-1-al out of the reaction system. (reactive distillation mode) is one of the particularly desirable features of the process of the invention, which further suppresses the formation of by-products. In addition, it is also possible to carry out the reaction in the gas phase or liquid phase while continuously flowing 2,7-octarenin-1-ol in a reactor filled with a shaped isomerization catalyst for a short contact time. octene
This is effective in increasing the selectivity of 1-R.

In the method of the present invention, the isomerization reaction mixture containing 7-octen-1-al after catalyst separation (in the case of a gas phase reaction, the flocculation liquid), or the 7-octen-1-al isolated from the reaction mixture by a conventional distillation operation. By hydrogenating octen-1-al in the presence of a hydrogenation catalyst and hydrogen, 7-octen-1-al has its C═C double bond hydrogenated and n
-converted to octylaldehyde. The catalyst used in the reaction is a hydrogenation catalyst known per se, and specific examples include palladium black, palladium catalyst supported on carbon, silica, or alumina, Zune nickel, modified Raney nickel, nickel diatomaceous earth, platinum black, Examples include supported platinum catalysts and supported rhodium catalysts. In addition, when the reaction is carried out under a hydrogen partial pressure of 10 atm or more, copper chromium oxide can also be used as the hydrogenation MW. Palladium catalysts supported on carbon are particularly preferred. The hydrogenation reaction of 7-octen-1-al is generally carried out in a liquid phase. In this case, n-octylaldehyde, which is the reaction raw material, by-product, or target product, or a mixture of these in arbitrary proportions functions as a solvent. Although it is industrially advantageous to have these functions also serve as solvents, solvents such as hydrocarbons, alcohols, esters, and ethers may be used in combination as necessary. Regarding hydrogen pressure and reaction temperature,
Since the optimum range varies depending on the type of catalyst, it cannot be unambiguously determined, but the conditions generally employed when hydrogenating compounds having a C═C double bond can be directly followed in the method of the present invention7- It is also applied to the hydrogenation reaction of octen-1-7-l. After separating the hydrogenation catalyst from the hydrogenation reaction mixture, high-purity n-octylaldehyde can be obtained in high yield by performing a conventional fractional distillation operation.Hydrogenation of 7-octen-1-al The by-product in the reaction is mainly n-octatool, but since it is extremely easy to separate n-octatool and n-octylaldehyde, the by-product of n-octanol does not pose a particular problem.

Ru.

N-octylaldehyde is converted to caprylic acid by oxygen oxidation by fusing kernels with oxygen gas or oxygen-containing gas in the presence of an oxidation catalyst and preferably an organic solvent. As the oxygen-containing gas, air, a mixed gas of nitrogen and oxygen in any proportion, or a mixed gas of these with helium gas, argon gas, carbon dioxide gas, etc. is used.

The reaction temperature is room fjA~120℃, especially 50~9
Temperatures within the range of 0°C are preferred. As the oxidation catalyst, metal salts known per se as aldehyde oxidation catalysts, such as cobalt salts, manganese salts, nickel salts, copper salts, and iron salts, can be used. Aliphatic monocarboxylic acid salts are preferable as metal salts in consideration of solubility in the reaction mixture, corrosiveness to the reaction equipment, and ease of availability. In consideration of solubility in the mixed liquid, copper or iron aliphatic monocarboxylate is particularly preferred as the oxidation catalyst. Each of these oxidation catalysts may be used alone or in combination of two or more. The oxidation catalyst is generally used at a concentration of 1 to 10 milligrams (LO) per 11 of the reaction mixture. It is industrially most desirable to use the desired product, cabryl IV. Instead of caprylic acid or together with caprylic acid, other carboxylic acids such as acetic acid, propionic acid, butyric acid, etc. may be used as an organic solvent. .

The oxygen oxidation reaction of n-octylaldehyde according to the method of the present invention is usually carried out by continuously or intermittently feeding oxygen gas or an oxygen-containing gas and n-octylaldehyde into a reaction solvent in which an oxidation catalyst is dissolved.

In this case, the reactor used is a stirred reactor, a bubble column reactor, a perforated plate column reactor, etc. which are usually used in gas-liquid contact reactions. The reaction pressure cannot be unambiguously determined because it varies depending on the oxygen concentration in the oxygen-containing gas, the reaction temperature, etc., but it is usually selected from within the range of 1 to 20 air pressures. Highly pure caprylic acid can be separated and obtained from the reaction mixture after the reaction by a normal distillation operation. Prior to the distillation operation, it is desirable to decompose minute amounts of peroxide contained in the reaction mixture by subjecting the reaction mixture to heat treatment and/or catalytic treatment.

The method of the present invention will be specifically explained below with reference to Examples.

Example 1 1) Synthesis of 7-octen-1-al and n-octylaldehyde 2.7-octarenine-1- was placed in a 100 m trizoro flask equipped with a stirring device, a liquid and gas feeder, and connected to a distillation device. All 30 fpIl and powdered copper chromium oxide catalyst2. Ofl (manufactured by 8 Volki Kagaku Co., Ltd., N-20
5) and immersed the flask in an oil bath maintained at 205°C. While stirring vigorously, add 25 to 40% nitrogen
2,7-octarenine-1- while flowing at a rate of hr.
Oars were continuously fed at a rate of 1'70v4/hr. The reaction was carried out in this manner for a total of 4 hours. Total 6
754 distillates were obtained. Analysis by gas chromatography revealed that 70 mol% of 7-octene was present in the distillate.
As soon as it was found that 1-R was present, ethyl alcohol, the above O distillate 150f and 596Pdy'C6 were added to an autoclave equipped with a magnetic stirrer, a gas inlet and a gas outlet. . After separating the catalyst from the reaction mixture and distilling off ethanol from the liquid, fractional distillation is carried out under reduced pressure.
N-octylaldehyde 929 was obtained as a 55V10mmHg fraction.

2) Synthesis of caprylic acid In a 100-meter four-bottle flask equipped with a humidity needle, a stirrer, a reflux condenser, a raw material feedlot, and an oxygen inlet, add 30 propionic acid, 1 ferrous acetate, and 32 capes (per 1 j of reaction mixture). 5.0217 mol) was added and the contents were heated with stirring to completely dissolve the ferrous acetate. A micro feeder connected to the raw material feeder was charged with 5 oppd of a 4 mot&/l propionic acid solution of n-octylaldehyde which had been previously purged with nitrogen. When the temperature inside the reactor became constant at 65℃, the contents were heated to 800γpm.
An oxidation reaction was carried out by continuously adding a propionic acid solution of mono-octylaldehyde at a feed rate of 10 d/hour from the raw material feeder over a period of 3 hours while stirring at a rotational speed of 10 and introducing oxygen gas at a flow rate of 1017 hours. I did this.

After the addition of n-octylaldehyde was completed, 1 was further added at the same temperature.
Stirring was continued for an hour. During the reaction period, the internal temperature was kept constant at 65°C. The conversion rates of n-octylaldehyde immediately after the end of n-octylaldehyde addition (3 hours after the start of the reaction) and during the oxidation reaction route Y (4 hours after the start of the reaction) were measured by gas chromatography and were 92% and 99%, respectively. Met. Furthermore, the selectivity to cafrylic acid (based on converted n-octylaldehyde) at the end of the reaction was 959.
It was 6. Carbon dioxide generation rate (based on converted n-octylaldehyde) was determined by off-gas analysis every hour from the start of the reaction.
After washing with 2.0 ml of distilled water and 120 ml of distilled water, fractional distillation was carried out under reduced pressure to obtain about 15 f of caprylic acid as a fraction of 98 to 100'C/2 mmHg.

In the same manner as above, 2,7-octarenin-1-ol was isomerized by variously changing the type of catalyst and the atmosphere in the reaction system. 7-octene-1 contained in distillate
-R selectivity is shown in Table 1. Note that the selectivity was expressed as the molar percentage of 7-octen-1-al to the changed 2,7-octarenin-1-ol. When the distillate containing unreacted raw materials obtained in the isomerization reaction was hydrogenated using a palladium catalyst supported on activated carbon Cζ in the same manner as in the above distribution, the results shown in Table 1 were obtained. It was done.

Table 1 Examples 2 to 8 N-octylaldehyde was produced in the same manner as in Example 1 of Practical Mi, and was treated in the same manner as in 2) of Example 1, except that the type and amount of catalyst and the type of solvent were changed. , oxidized and oxidized. The results are summarized in Table 2.

Table 2 I used the one from

5) Represents the conversion rate at the time of termination of the reaction.

Claims (1)

[Claims] 2. 7-octarenin-1-ol is isomerized in the presence of a catalyst selected from the group consisting of a copper-based catalyst and a chromium-based melt, and the resulting 7-octen-1-al is isomerized in the presence of a hydrogenation catalyst and hydrogen. A method for producing caprylic acid, which comprises hydrogenating to give n-octylaldehyde, which is then oxidized with oxygen in a liquid phase in the presence of an oxidation catalyst.