JPS628419B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing trimethylolheptane by methylolating n-octylaldehyde with formaldehyde.

It has already been known that when an aliphatic aldehyde represented by the general formula RCH ₂ CHO (R: aliphatic hydrocarbon group) is reacted with formaldehyde in the presence of a base, a trimethylolalkane represented by RC (CH ₂ OH) ₃ is obtained. well known. In particular, the production of trimethylolpropane from n-butyraldehyde is carried out on a large scale industrially, and the trimethylolpropane is used as a raw material for alkyd resins, polyurethanes, polyesters, and the like. n-
Since both butyraldehyde and trimethylolpropane have high solubility in water, the synthesis reaction of trimethylolpropane by methylolation of n-butyraldehyde can be carried out while maintaining a homogeneous system throughout in an aqueous solution.
Trimethylolheptane obtained from n-octylaldehyde has many superior basic physical properties compared to trimethylolpropane, but n-octylaldehyde is expensive and n-octylaldehyde and the product trimethylolheptane are Trimethylolheptane has not yet been produced on an industrial scale because it is substantially insoluble in water and its production method involves many problems.

Conventionally, as a method for producing trimethylolheptane, a method of methylolizing n-octylaldehyde in the presence of a surfactant [J.Amer.Chem.Soc.
, 76 , 1697-9 (1954)], a method for methylolating n-octylaldehyde while keeping the reaction system homogeneous by coexisting ethanol [Acta.Chem.Scand., 16 , 1062 (1962)] have been proposed, but in either method the yield of trimethylolheptane is at most about 60%, which is not industrially satisfactory.

The present inventors have previously discovered an advantageous method for producing n-octylaldehyde using butadiene, water and hydrogen as starting materials (Japanese Patent Application No. 56-204997). From this point of view, the present inventors conducted intensive research to develop an industrially advantageous method for producing trimethylolheptane from n-octylaldehyde, and as a result, they arrived at the present invention. That is, according to the present invention, (1) trimethylolheptane is produced by reacting n-octylaldehyde and formaldehyde in the presence of an alkali metal hydroxide or an alkaline earth metal hydroxide in tetrahydrofuran or dioxane. (2) Distill the reaction mixture obtained in step (1) to remove tetrahydrofuran or dioxane, and then maintain the distillation residue at a temperature of 60°C or higher to separate the organic layer. (3) After heat-treating the organic layer obtained in step (2) in the presence of an acid catalyst and water, the
By adding aromatic hydrocarbon No. 9 and crystallizing and separating trimethylolheptane crystals, trimethylolheptane can be produced in high yield and purity.

In the method of the present invention, an aqueous formaldehyde solution is usually used as formaldehyde. As the formaldehyde aqueous solution, an industrially available 5 to 50 wt.% formaldehyde aqueous solution can be used as it is. The concentration of n-octylaldehyde in the reaction solution is preferably in the range of 2 to 20 wt.% based on the reaction mixture.
The amount of formaldehyde used is 3/1 to 6/1 in molar ratio to n-octylaldehyde, especially
The ratio is preferably 3.3/1 to 4.2/1. If the molar ratio is less than 3/1, the amount of unreacted n-octylaldehyde remaining will increase, and the proportion of by-products such as di-trimethylolheptane will increase, which is not preferable. Moreover, if the molar ratio exceeds 6/1, the amount of by-products of various formals will increase, and the cost of recovering unreacted formaldehyde will increase, which is industrially undesirable.

Specific examples of alkali metal hydroxides and alkaline earth metal hydroxides include lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, etc., but reaction results and prices may vary. In consideration of this, sodium hydroxide is particularly preferred. The amount of these alkali metal or alkaline earth metal hydroxides to be used is expressed as a molar ratio to n-octylaldehyde.
The range of 1.0/1 to 1.5/1 is preferable. The reaction temperature is in the range of about 5 to 100°C, particularly preferably 30°C.
A temperature within the range ~50°C is chosen.

The methylolation reaction of n-octylaldehyde according to the method of the invention is carried out in tetrahydrofuran or dioxane, which can increase the reaction rate and the yield of trimethylolheptane. Conventionally, it has been proposed to use lower alcohols as reaction solvents in the methylolation reaction of n-octylaldehyde, but according to detailed studies by the present inventors, when the reaction is carried out in these lower alcohols, are various formals,
It was found that hemiformals were produced as a by-product and the yield of trimethylolheptane was significantly reduced. In addition, hydrocarbons, halogenated hydrocarbons, and ethers other than tetrahydrofuran and dioxane are chemically stable under the reaction conditions, but the reaction rate, trimethylolheptane yield, and the complexity of the trimethylolheptane separation process, etc. Considering this, these are unsuitable as reaction solvents. Tetrahydrofuran or dioxane is used in an amount ranging from 0.05 to 0.9 by weight relative to the reaction mixture. If the weight ratio of these solvents to the reaction mixture is less than 0.05, the reaction rate will be slow, and if the weight ratio exceeds 0.9, the cost of recovering the solvent will increase, which is not preferable.

A specific method for carrying out the methylolation reaction of n-octylaldehyde is (i) simultaneously adding n-octylaldehyde, an aqueous formaldehyde solution, and an aqueous solution of an alkali metal or alkaline earth metal hydroxide to an aqueous solution containing tetrahydrofuran or dioxane; How to react while
b) A method of reacting a mixture of an aqueous formaldehyde solution and tetrahydrofuran or dioxane while simultaneously adding n-octylaldehyde and an aqueous solution of an alkali metal or alkaline earth metal hydroxide; c) A method of reacting an aqueous formaldehyde solution, tetrahydrofuran or dioxane, and There are three possible methods: a method of reacting while adding an aqueous solution of an alkali metal or alkaline earth metal hydroxide to a mixed solution consisting of n-octylaldehyde, but according to the studies of the present inventors, (b) The method was found to be most favorable for increasing the yield of trimethylolheptane. In addition, in the method (b), n-octylaldehyde can also be used after being partially diluted with tetrahydrofuran or dioxane. It goes without saying that the rate of addition of these reaction reagents is determined by the reaction temperature and the cooling capacity of the reactor.

After the methylolation reaction, unreacted formaldehyde remaining in the reaction mixture is usually converted to formate by heat treatment in the presence of an alkali.
After the reaction mixture after the heat treatment is neutralized with formic acid or mineral acid, most or all of the solvent is recovered by distillation. When the residual liquid after solvent distillation is maintained at a temperature of 60° C. or higher, the residual liquid is separated into an organic layer mainly consisting of trimethylolheptane and an aqueous layer mainly consisting of formate. In this case, if the holding temperature of the residual liquid is lower than 60°C, it is not preferable because some crystals may precipitate or the liquid separation properties of the organic layer may deteriorate. The resulting organic layer is heat treated in the presence of an acid catalyst and water, thereby hydrolyzing various formals present in small amounts in the organic layer. This treatment can improve the yield and purity of trimethylolheptane. Acid catalysts that can be used include sulfuric acid,
Mineral acids such as hydrochloric acid, organic acids such as formic acid, acetic acid, oxalic acid, benzenesulfonic acid, silica-alumina, silica
Examples include solid acids such as magnesia. Although the heating temperature varies depending on the type and concentration of the acid catalyst, a temperature within the range of 100 to 300°C is generally selected.

After the heat treatment, the organic layer is neutralized with an alkali if necessary, and then added to the organic layer with a carbon number of 6 to
Aromatic hydrocarbon No. 9 is added to crystallize and separate trimethylolheptane crystals. According to a detailed study by the present inventors, the solubility of trimethylolheptane in aromatic hydrocarbons is strongly dependent on temperature;
At temperatures below 60°C, it is virtually insoluble, while at temperatures above 60°C, it exhibits high solubility. Therefore, by utilizing this principle, highly purified trimethylolheptane can be efficiently obtained. mentioned above
Acta.Chem.Scand., 16 , 1062 (1962) describes the precipitation of trimethylolheptane as crystals from a chloroform solution; There is no solubility phenomenon of trimethylolheptane as in the case of hydrocarbons, and both the yield and purity of trimethylolheptane are low. Aromatic hydrocarbons having 6 to 9 carbon atoms include benzene, toluene, xylene, ethylbenzene,
Specific examples include propylbenzene and trimethylbenzene. The amount of these aromatic hydrocarbons used is 1 to 50 in weight ratio to the organic layer.
, particularly preferably from 5 to 20.

Prior to crystallizing and separating trimethylolheptane from the organic layer, water and formate present in the organic layer are each subjected to azeotropic dehydration treatment, filtration, sedimentation,
It can also be removed in advance by centrifugation, etc.
In this case, higher purity trimethylolheptane can be obtained. The temperature used for crystallization separation of trimethylolheptane is 20 to 50.
A temperature within the range of °C is chosen. After crystallizing and separating trimethylolheptane, the aromatic hydrocarbon is recycled to the step of crystallizing and separating trimethylolheptane from the organic layer described above and is reused.

The method of the present invention will be specifically explained below using Examples.

Example 1 500 g of a 12 wt.% formaldehyde aqueous solution (2.0 mol as formaldehyde) and 500 g of tetrahydrofuran were placed in a flask with content 2, and while stirring the internal temperature was maintained in the range of 35 to 40°C, n-
70.4g (0.55mol) of octylaldehyde and 40wt.
% aqueous sodium hydroxide solution (0.66 mol as sodium hydroxide) was simultaneously and continuously added over 5 hours. After the addition was complete, stirring was continued for an additional 2 hours at the same temperature. Next, 10 g of 40 wt.% aqueous sodium hydroxide solution was added, and the mixture was further stirred under reflux for 4 hours. After the reaction mixture was adjusted to pH 6.8 by adding formic acid, tetrahydrofuran was distilled off under normal pressure. When the residual liquid after tetrahydrofuran was distilled off was kept at 80°C, it was separated into two layers. The organic layer was taken out, 100 g of sulfuric acid aqueous solution (PH: 1.0) was added, and the mixture was kept at around 100° C. for 8 hours with stirring. After neutralization with sodium hydroxide, extraction was performed at 70°C using 1000ml of toluene. After water and salts were removed from the toluene solution by azeotropic dehydration and filtration, the solution was cooled to room temperature, and white crystals were precipitated. The obtained crystals were collected and dried to obtain 84 g of trimethylolheptane. The yield of trimethylolheptane was 80.4% based on n-octylaldehyde.

Comparative Example 1 Trimethylolheptane was synthesized in the same manner and under the same conditions as in Example 1, except that 500 g of ethanol was used instead of 500 g of tetrahydrofuran. The yield of trimethylolheptane was 55 g, and various ethyl ether derivatives were produced as by-products. The yield of trimethylolheptane was 52.6% based on n-octylaldehyde.

Example 2 375 g of 16 wt.% formaldehyde aqueous solution (2.0 mol as formaldehyde) and 500 g of dioxane
Pour g into a flask with contents 2 and bring the internal temperature to 35-40.
A dioxane solution containing 70.4 g (0.55 mol) of n-octylaldehyde under stirring while maintaining the range of ℃
350 g and 66 g of a 40 wt.% aqueous sodium hydroxide solution (0.66 mol as sodium hydroxide) were simultaneously and continuously added over 5 hours. After the addition was complete, stirring was continued for an additional 2 hours at the same temperature. Next, 10 g of 40 wt.% aqueous sodium hydroxide solution was added, and the mixture was further stirred for 4 hours under reflux. By adding formic acid to the reaction mixture
After adjusting the pH to 6.8, dioxane was distilled off under normal pressure. When the residual liquid after dioxane was distilled off was kept at 80°C, it was separated into two layers. The organic layer was taken out, 100 g of a sulfuric acid aqueous solution (PH: 1.0) was added, and the mixture was kept at around 100° C. for 8 hours with stirring. After neutralization with sodium hydroxide, an extraction operation was performed at 70°C using 1000 ml of xylene. After water and salts were removed from the xylene solution by azeotropic dehydration and filtration, white crystals were precipitated when the liquid was cooled to room temperature. The obtained crystals were collected and dried to obtain 83 g of trimethylolheptane.

Comparative Example 2 Trimethylolheptane was synthesized in the same manner and under the same conditions as in Example 2, except that 1000 ml of chloroform was used instead of xylene and the extraction operation was performed at 50°C. The yield of trimethylolheptane was 64 g. When the same reaction was carried out using n-butyl acetate instead of chloroform, the yield of trimethylolheptane was 62 g.

Claims (1)

[Claims] 1. Trimethylolheptane is synthesized by reacting n-octylaldehyde and formaldehyde in the presence of an alkali metal hydroxide or alkaline earth metal hydroxide in tetrahydrofuran or dioxane, 2. The reaction mixture obtained in step (1) is subjected to distillation to remove tetrahydrofuran or dioxane,
Next, the distillation residue is separated into an organic layer and an aqueous layer by maintaining the temperature above 60°C, and the organic layer obtained in step (2) is heat-treated in the presence of an acid catalyst and water. , this has 6 to 9 carbon atoms
A method for producing trimethylolheptane, comprising: adding an aromatic hydrocarbon to crystallizing and separating trimethylolheptane crystals.