JPS6139932B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing pinacolon from 4,4,5-trimethyl-1,3-dioxane. The method of producing pinacolon by decomposing 4,4,5-trimethyl-1,3-dioxane, which is synthesized by the Prins reaction between 2-methylbutene-2 and formaldehyde, in the presence of a strong inorganic acid aqueous solution has been known for a long time. (for example, German patent no.
No. 714488). In addition, as an improvement to this method, by coexisting 2-methylbutene-2 in the reaction system, formaldehyde produced as a by-product in the reaction process is reactively captured, increasing the yield of pinacolon, and at the same time recovering formaldehyde and purifying pinacolon. It is disclosed in US Pat. No. 4,059,634 that this can be facilitated. On the other hand, it is well known that the concentration of the acid aqueous solution when producing pinacolon by decomposing 4,4,5-trimethyl-1,3-dioxane in the presence of an inorganic strong acid aqueous solution has a large effect on the yield of pinacolon. ing. For example, Chemical Abstract 78 71330d
(1973), the yield of pinacolon is only 2.3% when using 2.5% hydrochloric acid, and even when using 20% hydrochloric acid, the yield of pinacolon is only 34% at most. It has been reported. This means that in order to obtain pinacolon from 4,4,5-trimethyl-1,3-dioxane with a satisfactory reaction yield, it is necessary to use a strong inorganic acid aqueous solution at a high concentration of at least 20% by weight. do. However, the same report also states that 4,4,5-trimethyl-1.
It is described that the production of pinacolon by acid hydrolysis of 3-dioxane occurs via the dehydration reaction of the primary product, 2,3-dimethylbutane-1,3-diol. This suggests that since the same reaction conditions are also the conditions for the Prince reaction, there is a possibility that the intermediate of the reaction may react with the formaldehyde produced in the reaction system and change into a high-boiling point compound (Bull.Soc .Chim.France, 1964 (4)800～
811), by simply hydrolyzing 4,4,5-trimethyl-1,3-dioxane with acid, pinacolon cannot be obtained with a reaction yield that is industrially satisfactory even if a highly concentrated acid aqueous solution is used. means difficult. The invention of U.S. Pat. No. 4,059,634 was made in consideration of this fact. For example, in addition to hydrochloric acid at a concentration of 36% by weight, 2-methylbutene-2 is allowed to coexist to eliminate formaldehyde produced as a by-product in the reaction system. By reacting to produce pinacolon, the pinacolon yield was increased by 4.4.5-trimethyl-1.
This shows that the yield can be improved to 69% of the theoretical yield based on 3-dioxane. However, even in this case, the pinacolone yield is only 35% of the theoretical yield when converted to a yield that takes into account formaldehyde generated from the dioxane.
When this method is carried out on an industrial scale, there are considerable disadvantages not only in terms of the chemical consumption rate but also in terms of the separation and purification of the product pinacolon and the recycling and reuse of the highly concentrated hydrochloric acid used in the reaction. As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention found that 4,4,5-trimethyl-1,3-dioxane with the general formula () (In formula (), W and Z are hydrogen atoms, and either one of X and Y is OH, Cl or Br and the other is a hydrogen atom, or the adjacent one of W, X, Y and Z When thermal decomposition is carried out in the presence of a strong inorganic acid aqueous solution in the presence or absence of butenes or their derivatives (where two that match form a single bond and the remaining two represent hydrogen atoms), a small amount is added to the reaction system. By coexisting a salt of a strong inorganic acid that is partially soluble in both, the concentration and amount of the strong inorganic acid can be reduced, and the above-mentioned problems are not only alleviated, but also the yield of pinacolon is improved; In particular, it has been found that when the compound represented by the general formula () is coexisting, the formaldehyde by-produced during the reaction can be reused efficiently, and the yield of pinacolon can be dramatically increased. It came to this. Inorganic strong acids preferably used in the present invention include sulfuric acid,
hydrochloric acid, hydrobromic acid, phosphoric acid or perchloric acid;
Two or more of them may be used in combination. According to the method of the present invention, in which a salt of a strong inorganic acid is coexisting in the reaction system, even when using any of the above-mentioned acids, the concentration and amount are much lower than those required by the conventionally known methods described above. The reaction can be carried out in a high yield with a small amount. However, the acid concentration in the aqueous phase of the reaction system should be 0.5 mol/Kg (aqueous phase) or more, and the amount of inorganic strong acid used should be 4,4,5-trimethyl-1,3
- The amount is preferably maintained at 0.1 times or more, preferably 0.3 times or more by mole relative to dioxane. In the present invention, the salt of the inorganic strong acid to be used in combination with the inorganic strong acid must be at least partially soluble in the reaction system, and preferably has a solubility in water of 35 or more at 100°C. Both neutral and acid salts can be used, such as lithium, sodium, potassium, rubidium, cesium, copper (), magnesium, calcium, strontium, barium, zinc, cadmium, aluminum, scandium, zirconium, titanium ( ), tin (), manganese (), iron, cobalt (), chlorides and bromides such as nickel, ammonium, sodium, rubidium, cesium,
Magnesium, cadmium, zinc, aluminum, cobalt (), copper (), nickel (),
Sulfates such as manganese (), perchlorates such as calcium, silver, strontium, sodium, barium, magnesium, acid salts such as sodium hydrogen sulfate, potassium hydrogen sulfate, ammonium dihydrogen phosphate, sodium dihydrogen phosphate, Further examples include complex salts such as magnesium potassium chloride and sulfate. Among these, those having high molar solubility and high stability in the aqueous phase under reaction conditions are preferred, and in consideration of this point, salts of alkali metals and alkaline earth metals are most preferred. Although the acid group of the inorganic strong acid and the acid group of the inorganic strong acid salt used in the reaction do not necessarily have to be the same, combinations that would produce a poorly soluble salt under the reaction conditions must be avoided. Furthermore, two or more salts of inorganic strong acids may be used in combination within the range that satisfies the above-mentioned solubility, but in this case as well, combinations that would produce poorly soluble salts under the reaction conditions must be avoided. The amount of the inorganic strong acid salt to be used will depend on the concentration of the inorganic strong acid used together with the inorganic strong acid salt, and will be smaller if the inorganic strong acid concentration in the aqueous phase under the reaction conditions is high, and conversely if the acid concentration is low. It is controlled so that it is large, but it is used so that it is 1/10 or more of the saturated dissolution amount in the inorganic strong acid aqueous solution under the reaction conditions. The above general formula () coexisting in the reaction system in the present invention
Specifically, the butenes represented by are 2-methylbutene-1,2-methylbutene-2,3-methylbutene-1, and the butene derivative is 2-methylbutene-1.2-methylbutene-2,3-methylbutene-1.
2-chlorobutane, 2-methyl-2-bromobutane, 2-methyl-3-chlorobutane, 2-methyl-3-bromobutane, 2-methylbutanol-2
and 3-methylbutanol-2. Among these, butenes can be easily obtained industrially, for example, by partial hydrogenation of isoprene. Further, butene derivatives can be obtained industrially, for example, by adding hydrogen chloride, hydrogen bromide or water to the above-mentioned butenes. These butenes and their derivatives do not necessarily have to be pure, and may contain, for example, isoprene, methylbutane, or inorganic or organic acids. Butenes represented by the general formula () or derivatives thereof are used together with the raw material dioxane,
And if it contains a strong inorganic acid group,
Within the above acid amount ranges, relatively smaller amounts of acid are used. In addition to water, the reaction can also be carried out in the presence of a diluent inert to the reaction, such as saturated hydrocarbons, chlorinated hydrocarbons and ketones, such as methylbutane, hexane, cyclohexane,
Butyl chloride, 1,1,1-trichloroethane,
Hydrophobic compounds such as 1,1,1,2-tetrachloroethane, carbon tetrachloride, and pinacolone can be mentioned. However, no particular benefit is provided by the use of diluents. The reaction temperature is preferably in the range of 70 to 200°C, particularly 90 to 150°C. The reaction is also carried out at a pressure above atmospheric pressure, usually between atmospheric pressure and 30 kg/cm ² . When the reaction is carried out at a temperature higher than the boiling point of the reaction mixture, the appropriate reaction pressure is the autogenous pressure of the reaction mixture at the reaction temperature, and pressurization with nitrogen or other inert gas is not particularly necessary. The reaction method is as follows: (1) An aqueous solution containing a strong inorganic acid and a strong inorganic acid salt is kept at a predetermined temperature while stirring, and 4,4,5-trimethyl-1,3-dioxane or 4,4,5-trimethyl -1・
3-dioxane and the butenes represented by the above general formula () or their derivatives are reacted while continuously or intermittently added; (2) an aqueous solution containing a strong inorganic acid and a strong inorganic acid salt and 4,4,5-trimethyl; - In the method of (3) and (2), in which 1,3-dioxane is reacted by mixing and stirring at a predetermined temperature, the butenes represented by the above general formula () or its derivatives are added continuously or intermittently during the reaction. (4) an aqueous solution containing a strong inorganic acid and a strong inorganic acid salt, and 4.4.5
A method may be used in which -trimethyl-1,3-dioxane and the butenes represented by the general formula () or a derivative thereof are simultaneously mixed and stirred to react, but method (1) is generally preferred. The method of the present invention can be carried out by either a continuous method or a batch method, but since it is a heterogeneous phase reaction, the reaction must be carried out under vigorous stirring, and for the same purpose, a surfactant is present. The reaction can also be carried out below. The reaction time naturally varies depending on the amount of starting materials used, the concentration and amount of the aqueous solution of the inorganic strong acid and the salt of the inorganic strong acid, the reaction temperature, and other factors, but is usually 1 to 20 hours. Methods for obtaining pinacolon from the reaction mixture after the reaction include (a) separating the organic phase from the aqueous phase and then subjecting the organic phase to distillation as it is or after neutralizing if necessary; (b) reaction. Methods such as neutralizing the mixture and then subjecting it to distillation as it is or only the organic phase, and (c) subjecting the reaction mixture to distillation as it is, are used. If method (a) or (c) is used, it is possible to circulate all or part of the aqueous phase to the reaction system and reuse it, but from the standpoint of efficient separation and acquisition of pinacolon, (a) ) is preferred.
As the distillation method, steam distillation, normal pressure distillation, or vacuum distillation is used. The use of a salt of a strong inorganic acid in the present invention is advantageous in reducing the amount of organic matter partitioned into the aqueous phase when the reaction mixture is separated into an organic phase and an aqueous phase. Therefore, all or part of the aqueous phase separated from the organic phase can be re-supplied to the reaction system as it is or after being mixed with a dilute circulating aqueous phase, after concentrating and removing water if necessary. In addition, components with boiling points lower than pinacolone obtained when the organic phase of the reaction mixture is distilled are mainly 2-methylbutenes,
Since it is a precursor of 2,3-dimethylbutadiene and other reaction raw materials or pinacolon, it can be recycled to the reaction system as a mixture. The method of the present invention is applicable to the above-mentioned operation in which the organic phase is separated from the reaction mixture to obtain pinacolon, and at the same time, the inorganic strong acid aqueous solution is recovered, recycled, and reused. It is also advantageous because it is effective in suppressing the distribution of organic matter into the aqueous phase (reducing dissolved organic matter). Pinacolon obtained by the present invention is industrially useful as a solvent or as a synthetic intermediate for agricultural chemicals, rubber chemicals, etc. Next, the present invention will be explained in more detail with reference to Examples. Comparative Example 1 100 with stirrer, reflux condenser and thermometer
Purity 91.9 containing 7.8% 4-methyl-4-ethyl-1,3-dioxane in a ml three-necked flask.
% 4,4,5-trimethyl-1,3-dioxane and 36.5 g of hydrochloric acid with a concentration of 10% by weight.
The reaction was carried out under reflux for 3 hours while stirring. During the reaction, the reflux temperature decreased from 92.8℃ to 86.5℃.
The temperature reached 91.5℃. The reaction mixture was neutralized with calcium hydroxide while being cooled in an ice-water bath, then transferred to a separatory funnel with 50 ml of diisopropyl ether, shaken well, and then separated. Analysis of the organic phase by gas chromatography revealed that no raw material dioxane remained and the amount of pinacolon produced was 3.16 g. This is the preparation 4.4.5-trimethyl-1.
This corresponds to 34.4% of the theoretical yield based on 3-dioxane. In addition, products other than pinacolon include 3.
4-dimethyl-5,6-dihydro-2H-pyran and 2,3-dimethyl-1,3-butadiene were determined to be 8.0% and 1.7%, respectively. Example 1 The reaction and treatment analysis were carried out in exactly the same manner as in Comparative Example 1 except that 7.5 g of lithium chloride was added to the reaction system. The yield was 44.1%. 3,4-dimethyl-5,6-dihydro-2H
The amounts of -pyran and 2,3-dimethyl-1,3-butadiene produced were 1.0% and 0.2%, respectively. Example 2 Raw material dioxane with the same composition as used in Comparative Example 1 was placed in a pressure-resistant glass electromagnetic stirring reactor with an internal volume of 300 ml.
18.5g, 2-methylbutanol-213.7g, concentration
52.0 g of 10% by weight hydrochloric acid and 10.7 g of lithium chloride
was charged and kept at 100°C for 6 hours with vigorous stirring. After the reaction, the mixture was cooled in an ice-water bath, 70 ml of xylene was added, stirred again, and the organic phase was separated using a separatory funnel. The organic phase was washed once with 30 ml of a 10% sodium carbonate aqueous solution and twice with 30 ml of water, and then analyzed by gas chromatography. The yield was 112.3 mol%. Example 3 In the same apparatus as in Example 2, 52.0% hydrochloric acid with a concentration of 10% by weight was added.
g and 10.7 g of lithium chloride while stirring.
It was kept at 100℃. A mixed solution of 18.5 g of raw material dioxane and 13.7 g of 2-methylbutanol-2 having the same composition as used in Example 2 was introduced into the solution using a micro-metering pump and allowed to react over a period of 4 hours. After the introduction was completed, the mixture was stirred at the same temperature for another 2 hours, and then treated and analyzed in the same manner as in Example 2. The yield of pinacolon was 146.4 mol% based on the 4,4,5-trimethyl-1,3-dioxane charged. Ta. Comparative Example 2 The reaction was carried out in exactly the same manner as in Example 2 except that 100 g of 28 wt% hydrochloric acid was used instead of 52.0 g of 10 wt% hydrochloric acid and the addition of lithium chloride was omitted. Process analysis revealed that the yield of pinacolon was The rate is 4.
The amount was 87.1 mol% based on 4,5-trimethyl-1,3-dioxane. Example 4 80.3 g (0.11 mol) of hydrochloric acid with a concentration of 5% by weight and 43.2 g of magnesium chloride were charged into the same reaction apparatus as used in Example 3, and the temperature was raised to 400° C. while stirring. Next, in this state, 4,4,5-trimethyl-1,3-dioxane (composition: 4,4,5-
Trimethyl-1,3-dioxane 98.06%, 4-
Methyl-4-ethyl-1,3-dioxane 1.55
%) 14.3g (0.11 mol) and 10.5g of 2-methylbutanol-2 using a micro metering pump.
The reaction was carried out by keeping the same conditions for an additional 2 hours. The reaction mixture was treated and analyzed in the same manner as in Example 2, and the following results were obtained. Pinacolone yield 130.1 mol% 2,3-dimethylbutadiene yield 0.9 mol% However, the charge 4,4,5-trimethyl-1,3
- Mol% based on dioxane Example 5 Concentration 10 instead of hydrochloric acid and magnesium chloride
The reaction and analysis were carried out in exactly the same manner as in Example 4, except that 108 g (0.11 mol) of sulfuric acid and 71.9 g of sodium hydrogen sulfate were used, and the following results were obtained. Pinacolone yield 102.2 mol% 2,3-dimethylbutadiene yield 5.5 mol% However, the charge 4,4,5-trimethyl-1,3
-Mole% based on dioxane Examples 6 to 14 In a pressure-resistant glass electromagnetic stirring reactor with an internal volume of 300 ml, 52.0 g of hydrochloric acid with a concentration of 10% by weight and 10.7 g of lithium chloride
g was charged and kept at 100°C while stirring. Add 4-methyl-4-ethyl-1,3-dioxane to this.
18.5 g (0.131 mol) of 4,4,5-trimethyl-1,3-dioxane with a purity of 91.9% containing 7.8%
A mixed solution of 0.156 mol of butenes or a derivative thereof represented by the general formula () shown in Table 1 was introduced over a period of 4 hours using a micro-metering pump and allowed to react. After the introduction was completed, the mixture was stirred at the same temperature for an additional 2 hours. After the reaction, the mixture was cooled in an ice-water bath, 70 ml of xylene was added, stirred again, and the organic phase was separated using a separatory funnel. The organic phase was washed once with 30 ml of a 10% aqueous sodium carbonate solution and twice with 30 ml of water, and then analyzed by gas chromatography.
Table 1 shows the yield of pinacolone produced based on the 4,4,5-trimethyl-1,3-dioxane used. 【table】

Claims (1)

[Claims] 1 4,4,5-trimethyl-1,3-dioxane represented by the general formula () (In formula (), W and Z are hydrogen atoms, and either one of X and Y is OH, Cl or Br and the other is a hydrogen atom, or Pinacolon is produced by thermal decomposition in the presence of a strong inorganic acid aqueous solution in the presence or absence of butenes or their derivatives (two that match form a single bond and the remaining two represent hydrogen atoms). A method for producing pinacolon, which comprises coexisting at least a partially soluble salt of an inorganic strong acid in the reaction system.