KR950001677B1 - Process for producing dipentaerythritol - Google Patents

Abstract

No content.

Description

[Name of invention]

Method for preparing dipentaerythritol

Detailed description of the invention

[Technical Field]

The present invention relates to a method for preparing dipentaerythritol. More specifically, the present invention relates to a method for preparing dipentaerythritol (hereinafter referred to as "D-PE") by dehydration condensation of pentaerythritol (hereinafter referred to as "PE") under an acid catalyst.

Background Technology

D-PE, which is growing in demand as a raw material for polyesters, polyurethanes and polyvinyl chloride resins as a thermal stabilizer or lubricating oil, is used when synthesizing PE, that is, when PE is produced by reacting acetaldehyde with formaldehyde in the presence of alkali. Side product obtained. Using conventional customary methods, the minor product is isolated and purified to yield D-PE. In this process, the following methods have been proposed to increase the secondary formation ratio of D-PE.

(1) controlling the molar ratio of formaldehyde to acetaldehyde in the reaction system for PE synthesis to be smaller than the theoretical molar ratio 4; (2) the reaction is carried out with high concentrations of formaldehyde, acetaldehyde and alkaline reagents; And (3) the reaction is carried out by adding and dissolving PE in aqueous formaldehyde solution.

However, these methods have the disadvantage that PE and D-PE are obtained in low overall yield and the main product PE has poor quality. With the development of the methods; (4) The reaction is carried out by adding a small amount of formaldehyde, alkali and acetaldehyde in the reaction vessel in advance, and then simultaneously adding formaldehyde, alkali and acetaldehyde in excess of theoretical water while maintaining the reaction temperature below 50 ° C. Patent Publication No. 1-44689 is proposed. A method (5) of dehydrating condensation using PE such as phosphoric acid and sulfuric acid is also known (US Pat. No. 2,462,047). In addition, a method of separating D-PE from a mixture of PE and D-PE has also been proposed; (6) crystallizing D-PE from D-PE / PE mixed solution prepared at a ratio of 30/70 or more (US Pat. No. 2,448,566); And (7) D-PE is crystallized from a mixed solution having a specific PE concentration of PE / D-PE weight ratio of 16 or less (Japanese Patent Publication No. 2-10811). However, conventional methods for preparing D-PE by reaction with acetaldehyde and formaldehyde [Method (4) above) include PE and D-PE, sodium formate, bispentaerythritol monoformal (hereinafter "B-"). PE ") and the purification step must be complicated to separate sub-product impurities such as excess formaldehyde or acetaldehyde-formaldehyde self-polymerization product. In addition, since the possible production of D-PE depends on the production of PE and is limited to 10-15% of PE production, D-PE manufacturing has a problem that it cannot overcome the increasing demand.

The method of synthesizing polypentaerythritol mixtures [5] using such as phosphoric acid, sulfuric acid, aromatic sulfonic acid, etc. from PE has been aimed at synthesizing various polypentaerythritol mixtures. No method of synthesizing with The inventors have found that D-PE is first formed when PE is dehydrated condensed in the presence of an acid catalyst, but the D-PE formed is tripentaerythritol (hereinafter referred to as "T-PE") and then a high-molecular weight. This polypentaerythritol or into an intramolecular condensation product. Therefore, the inventors have found that the method is not practical for the D-PE production method unless other measures are taken.

US Pat. No. 2,448,566 [6] above describes a technique for separating D-PE from a PE and D-PE mixture, but D-PE from which a reaction mixture produced by self-condensation of PE is obtained. No synthetic method is described. Therefore, the method described in the United States patent can be referred to as a method for producing D-PE independent of the PE manufacturing method.

The method described in Japanese Patent Laid-Open No. 2-10811 [above (7)] not only has the same problems as the above methods (1) to (4) but also requires a cumbersome step of adjusting the PE concentration in a given range. .

It is an object of the present invention to solve the above problems and to produce D-PE with good efficiency, and to obtain a low concentration of impurities, easily identifiable, and a good quality product.

[Presentation of the present invention]

The present inventors have made intensive efforts to solve the above problem, so that when the dehydration condensation of PE is carried out in the presence of an acid catalyst, after the formation of D-PE and before the concentration of the continuously formed T-PE is excessively increased, The temperature was lowered to stop the reaction and simultaneously crystallize a portion of the PE to find that D-PE gave a reaction mixture concentrated to the desired concentration. Therefore, the first entity of the present invention is established.

That is, this invention shows the manufacturing method of dipentaerythritol which consists of the following.

The target pentaerythritol is condensed in a liquid state at a temperature of 200 ° C to 260 ° C in the presence of an acid catalyst; The temperature of the reaction mixture is lowered to crystallize a portion of pentaerythritol; The crystallized pentaerythritol is then removed from the reaction mixture to obtain a reaction mixture containing increased concentrations of dipentaerythritol.

The inventors have found that secondary formation of non-T-PE impurities produced when performing dehydration condensation of PE using an acid catalyst in a liquid-phase molten state can significantly reduce when the reaction is carried out in a polar solvent, moreover It was countered that the reaction mixture became easier to handle. Based on this finding, a second entity of the present invention is established.

Namely, the present invention condenses the target pentaerythritol in a liquid state in the presence of an acid catalyst; The condensation relates to a process for preparing dipentaerythritol, which is carried out in the presence of a polar solvent.

Best way for carrying out the invention

The first entity of the invention is described in detail below.

Acidic catalysts used in the present invention are materials that are commonly used as catalysts in the dehydration condensation of alcohols. An example is described in SHOKUBAI KOZA (Catalyst Course; Kodan-sha, published 1985), Vol. 8278, Table 13-3. Mineral acids such as, for example, phosphoric acid, phosphorous acid and sulfuric acid, inorganic salts such as metal sulfates and metal phosphates, clay minerals such as montmorillonite. Phosphoric acid and metal phosphates are particularly preferred. Metal species of metal phosphates include, for example, Al, B, Fe, Cr, Ti, Cu, Ni, Zn and Zr.

The optimum amount of catalyst can vary depending on the type of catalyst. In the case of phosphoric acid, for example, 0.01 to 3.0% by weight, preferably 0.1 to 1.5% by weight, more preferably 0.3 to 1.0% by weight, based on the reaction mixture. Extremely small amounts of catalyst appear to have a low rate of reaction, and extremely large amounts of catalyst result in increased secondary formation of impurities.

In the present invention, the PE is reacted in the liquid phase. For example in a liquid-phase molten state. For example, the reaction temperature needs to be higher than the melting point of the reaction mixture. Therefore, it is appropriate to carry out the reaction at a temperature of 200 to 260 ° C, preferably 230 to 250 ° C. Lowering the reaction temperature below this range undesirably results in the actualization of the reaction mixture and also significantly lowering the reaction rate.

The acid catalyst causes dehydration and condensation of the PE to first form D-PE. However, not only D-PE is formed but also T-PE is formed from D-PE once formed, and polypentaerythritol having a high molecular weight is formed as a result. It is basically difficult to completely prevent such continuous side reactions, but it is possible to some extent prevent side reactions.

More specifically, to prevent side reactions, it is most effective to lower the concentration of D-PE in the reaction mixture. However, if the concentration of D-PE is extremely low, the yield of D-PE itself will be reduced.

According to the invention, the reaction mixture is cooled by lowering the temperature to stop the reaction before the concentration of T-PE formed during the reaction increases. In order to prevent the concentration of T-PE from being excessively increased, the inventors of the present invention have a conversion rate of at least 25%, and a conversion rate of at least 2%, preferably 5 to 22%, and more preferably 8 to 18%. It was found that it was desirable to stop the reaction before the reaction occurred. This finding allows both secondary formation of impurities and formation of D-PE to be achieved in a well balanced state. When the conversion of PE is 25%, the weight ratio of D-PE / PE in the reaction mixture varies reasonably depending on the composition of the starting PE used, and the selectivity of the reaction. Omitted in the common example ranges from 0.18 to 0.22.

The reaction time can vary considerably depending on factors such as the amount and type of catalyst used and the reaction temperature. It may range from 10 to 600 minutes and preferably from 30 to 180 minutes.

Here, the conversion rate can be defined by the following formula.

In the above formula, the conversion rate is based on PE and B-PE. The conventionally useful PE contains 3 to 6% of D-PE and B-PE, and thus, in the present invention, 1 molecule of B-PE is 2 molecules of PE. And one molecule of formalin.

In the present invention, what is likely to occur is that if the concentration of D-PE in the reaction mixture is lowered by controlling the conversion of PE, preferably 25% or less, to control the concentration ratio of T-PE in the reaction mixture. It is difficult to separate and collect D-PE directly from the reaction mixture containing PE, which increases the manufacturing cost of D-PE.

According to the invention the reaction is stopped by cooling and then crystallized a portion of unreacted PE and removed from the reaction mixture to increase the concentration of D-PE in solution. According to the invention the concentration of D-PE in the weight ratio of D-PE / PEs (PEs refers to PE, D-PE, T-PE and other reaction products as a whole) is 3-25% and preferably 8-16% The concentration of D-PE may be increased to approximately 5-30%, preferably 16-23%, when crystallizing and removing a portion of PE from the reaction mixture with. The amount of PE removed after crystallization is approximately 5 to 35%, preferably 10 to 30%, and more preferably 23 to 28%.

In the present invention, the crystallized PE can be preferably separated from the reaction mixture in a liquid temperature of about 195 ° C. or less in the usual example. The optimum temperature may vary depending on the composition of the reaction mixture, the type and amount of catalyst used. Preferably it is 160-190 degreeC, More preferably, it is 176-188 degreeC. The temperature range is consistent with the temperature near the melting point of the common composition of PE and D-PE (D-PE / PE = 20/80).

In the present invention, in the step of cooling the reaction mixture and removing the PE, the PE can be selectively crystallized and then the crystallized product can be removed. Alternatively, the reaction mixture can be cooled to solidify completely, then heated again to melt a portion of it, and then remove the remaining crystals of PE. That is, both are the same.

Any of the above-mentioned methods known in the art can be used as a method of solid-liquid separation to remove the crystallized PE from the reaction mixture and to obtain a reaction mixture enriched in D-PE. Usually separation is done using filters. The shape of the filter is not particularly limited. It is preferable to use a sintered filter or a mesh filter made of metal in order to be able to perform filtration at a relatively high temperature.

There is no particular limitation as to the shape of the reaction vessel. Stirred batch batch or pipe flow type can be used. For example, in the case of a stirred crude batch reaction vessel with a filter in the reaction vessel, the solid PE may remain in the reaction vessel after solid-liquid separation and may be used to continuously react on its own.

According to the first embodiment of the invention, the liquid solution concentrated to 19-21% by weight of the D-PE group has a PE conversion of about 14-18%, a D-PE concentration of about 9-13% by weight, and a T-PE concentration. It can be obtained by cooling the reaction mixture having approximately 1 to 2% by weight to about 180 ℃. D-PE with high purity can be obtained by applying to the liquid solution in a conventionally useful separation method such as fractional crystals. PE that does not react can be circulated back into the reaction vessel and used as starting material. The second entity of the present invention is shown below.

As previously described, when performing dehydration condensation of PE using an acid catalyst in a liquid-phase molten state, secondary to high amounts of impurities such as polypentaerythritol or intramolecular condensation products having a higher molecular weight of T-PE Figured out the problem that is formed. It is not completely clear why this is happening but one reason is assumed that when the reaction temperature is necessarily above the melting point of the reaction mixture, the temperature of the initial stage of the reaction is above 240 ° C., especially when the reaction is carried out in a liquid-phase melting state. In the first embodiment of the present invention, the inventors filtered the PE from the reaction mixture to increase the concentration of D-PE near the melting point of the eutectic composition of PE and D-PE (D-PE / PE = 20/8). It was found that the filter at a temperature (approximately 160 ~ 190 ℃). Strictly controlling the temperature during filtration at such high temperatures is not easy. Filters often become obstructions during filtration, resulting in insufficient concentrations of D-PE. It has also been found that the concentration of D-PE in the reaction mixture is preferably adjusted to at least 20% by simple operation to increase the yield of D-PE formed.

The inventors have found that this novelty problem can be solved by carrying out the reaction in the presence of a polar solvent when the PE condenses in the liquid phase in the presence of an acid catalyst. In other words, although only the use of polar solvents in this type of reaction is explained, the use of polar solvents reduces the secondary formation of impurities during the reaction, facilitates the filtration of the reaction mixture in which D-PE is concentrated and We have found that it facilitates the effective advancement of the -PE concentration.

The polar solvent used in the second embodiment of the present invention is a molecule having a dipole moment, and has a dielectric constant of 15 to 100 at room temperature, and relates to a solvent that is stable under reaction conditions in the presence of an acid catalyst. Such polar solvents include dimethylformamide, dimethyl sulfoxide, tributyl phosphate, sulfolane, and 1,3-dimethyl-2-imidazolidinone, and water. In particular, sulfolane and 1,3-dimethyl-2-imidazolidinone can be preferably used because of their high boiling point and stability to acids. More surprisingly, the inventors have found that water can be preferably used as a polar solvent in the reaction step as well as in the continuous step of concentrating the D-PE.

The polar solvent may be used in the condensation in an amount of 5 to 70% by weight, preferably 10 to 30% by weight, based on the reaction mixture.

The acid catalyst used here may be the same as that used in the first embodiment of the present invention. The optimal amount of acid catalyst can vary depending on the type of catalyst used. For example, in the case of phosphoric acid, it may be an amount of 0.01 to 3.0% by weight, preferably 0.1 to 2% by weight based on the reaction mixture. Extremely small amounts of catalyst result in a lower reaction rate, and extremely large amounts of catalyst increase the secondary formation of impurities. In the second embodiment of the present invention, the PE is reacted in the liquid phase, and therefore it is preferable that the PE is in the liquid phase throughout the reaction. The reaction temperature is fixed to bring this state. To ensure that the PE is in the liquid phase throughout the reaction, the reaction temperature may vary depending on the type and amount of solvent used. Considering the rate of reaction and the secondary formation of impurities, it is appropriate to carry out the reaction at a temperature of 180-230 ° C, preferably 190-220 ° C. The reaction can also be carried out under pressure application.

In carrying out the second embodiment of the present invention, it is to provide a step of crystallizing a part of the PE by lowering the temperature of the reaction mixture before the concentration of T-PE formed during the reaction, such as the first embodiment of the present invention, is increased. In addition, it is also desirable to provide a step of removing the crystallized PE from the reaction mixture to obtain an increased concentration of the D-PE containing reaction mixture. The amount of PE removed after crystallization is determined according to the aforementioned amounts. Specifically, like the first entity of the present invention, the reaction temperature is reduced before the conversion of PE is greater than or equal to 25%, to stop the reaction and then crystallize and remove the PE. The reaction time can vary greatly depending on factors such as amount and form of solvent, catalyst used, reaction temperature and the like. It may range from approximately 30 to 900 minutes, preferably from 60 to 240 minutes.

The temperature at which the PE crystallizes (ie, the solid-liquid separation temperature) may vary depending on the composition of the reaction mixture, the amount and form of solvent used, the amount and form of catalyst used, and the like. The temperature may be in the range from 40 to 60 ° C., preferably in the range from 50 to 155 ° C. When filtering off the crystallized PE, a polar solvent in the same or different form as the polar solvent used during condensation may be added to the reaction vessel to improve the filtering. When additionally using a polar solvent, it is preferred to add an amount maintained at 30 to 70% relative to the total amount of the reaction mixture.

According to a second embodiment of the invention, the reaction mixture having a PE conversion of 10-15% and a D-PE concentration (D-PE / PEs) of 5-25% by weight and preferably 11-16% by weight is D- PE / PEs (previously described, PEs can be obtained from a starting material having a weight ratio of 1-5% by weight of PE, D-PE, T-PE and all other reaction products). From this reaction mixture a further liquid solution having a D-PE concentration (D-PE / PEs) of approximately 10 to 35% by weight, and preferably 24 to 28% by weight can be obtained. Commonly useful separation methods, such as fractional crystallization, can be applied to the liquid solution and therefore it is easy to obtain D-PE with high purity. Unreacted PE can be put back into the reaction vessel and used as starting material.

The invention is described in greater detail in the Examples below. The invention is not limited by the following examples. In the examples which follow the% used for the indication of the liquid solution composition relates to% by weight.

Example 1

500 g of starting material PE is placed in a reaction vessel made of stainless steel with a 1 µl internal volume, a thermometer and a heat-stirrer, a stainless steel bottom with a 5 μm mesh filter and a liquid outlet. The starting material consisted of 91.4% PE, 3.8% D-PE, 4.0% B-PE and 0.2% T-PE.

The temperature is raised to 240 ° C. to melt the mixture under N ₂ atmosphere, and then 1.5 g of 85% phosphoric acid is added to carry out the reaction at 240 ° C. for 1 hour. After the reaction, part of the reaction mixture was analyzed and found to consist of 79.7% PE, 11.6% D-PE, 1.6% T-PE and 6.2% other product, with no B-PE found. The analysis showed that the conversion of PE was 16.0% and the selectivity to D-PE was 55%.

The temperature of the reaction mixture is then lowered to 183 ° C. to crystallize a portion of the unreacted PE and the liquid phase portion flows out through a filter at the bottom of the reaction vessel. The result is 154 g of a liquid solution consisting of 64.6% PE, 19.6% D-PE, 3.0% T-PE and 11.7% other product.

The liquid solution is cooled to crystallize the whole. Then 330 g of water is added and the temperature is raised to 100 ° C. to dissolve the crystals. The solution is subsequently cooled to 42 ° C. to crystallize, and the resulting crystals are collected by filtration. As a result, the weight of the crystal excluding water content was 50.1 g, and the D-PE was 53.1% (weight ratio of PEs). 110 g of water was added to the product crystals to dissolve again, and the solution was cooled to 42 ° C to crystallize. The resulting crystals were collected by filtration to give 27.8 g of high purity D-PE crystals composed of 84.2% D-PE, 15.0% T-PE and 0.7% PE.

Example 2

20 g of zirconium phosphate was added to 500 g of molten PE in the same manner as in Example 1, and the reaction was performed at 240 ° C. for 1 hour. The result is a liquid solution consisting of 78.5% PE, 12.5% D-PE, 1.8% T-PE and 6.3% other product. B-PE could not be detected. As a result of the analysis, the conversion rate of PE was 17.6% and selectivity to D-PE was 55.7%.

The temperature of the reaction mixture is then lowered to 188 ° C. to crystallize a portion of the unreacted PE and the liquid phase flows out through a filter at the bottom of the reaction vessel. As a result, a liquid solution consisting of 63.8% PE, 20.0% D-PE, 3.3% T-PE and 11.1% other product is obtained.

Subsequently, crystallization by cooling was carried out twice using water in the same manner as in Example 1 to obtain a high purity D- consisting of 84.0% D-PE, 15.1% T-PE and 0.8% PE. 28.0 g of PE crystals are obtained.

Comparative Example 1

The reaction is carried out in the same manner as in Example 1 except that the reaction time is 2 hours. A reaction mixture is obtained consisting of 64.5% PE, 15.6% D-PE, 6.4% T-PE and 11.8% other product. As a result, the PE conversion was 32.3% and the selectivity to D-PE was 41.2%.

The temperature of the reaction mixture is then lowered to 180 ° C. to crystallize a portion of the unreacted PE and the liquid phase portion flows out through a filter at the bottom of the reaction vessel. As a result, 176 g of a liquid solution consisting of 46.0% PE, 22.6% D-PE, 10.8% T-PE and 20.1% other product are obtained.

Successively, crystallization by cooling was repeated twice with water in the same manner as in Example 1 to obtain 46.0 g of crystals composed of 61.8% D-PE, 35.0% T-PE and 0.7% PE. The resulting crystals appear as crystals containing high T-PE.

Therefore, this comparative example can only obtain crystals with high T-PE content and low purity D-PE when the reaction is carried out until the conversion of PE is 32.3%.

Comparative Example 2

The reaction was carried out in the same manner as in Example 1 except that the reaction temperature was fixed at 265 ° C. and the reaction time was 30 minutes. A mixed solution consisting of 56.9% PE, 14.9% D-PE, 8.3% T-PE and 18.5% other product is obtained. The results showed that the conversion of PE was 40.0% and the selectivity to D-PE was 31.2%.

The temperature of the reaction mixture is then lowered to 176 ° C. to crystallize some of the unreacted PE and some of the liquid phase flows out through a filter at the bottom of the reaction vessel. As a result, 188 g of a liquid solution consisting of 38.1% PE, 20.1% D-PE, 13.1% T-PE and 28.3% other product are obtained.

Subsequently, crystallization by cooling twice with water in the same manner as in Example 1, yielding 47.8% crystals consisting of 55.6% D-PE, 40.8% T-PE and 0.7% PE. . The resulting crystals appeared to have high T-PE content as in Comparative Example 1. Therefore, this comparative example can only obtain crystals with very high T-PE content and low purity D-PE when the conversion of PE is carried out up to 40.0%.

Example 3

3 g of 85% phosphoric acid was used, and the reaction temperature was initially fixed at 240 ° C. for 15 minutes, and then lowered to 230 ° C. for 1 hour, except that the reaction was carried out in the same manner as in Example 1. As a result, a liquid solution consisting of 80.7% PE, 11.4% D-PE, 1.3% T-PE and 5.4% other product is obtained. The results show that the conversion of PE is 14.8% and the selectivity to D-PE is 58.3%.

The temperature of the reaction mixture is then lowered to 188 ° C. to crystallize a portion of the unreacted PE and the liquid phase portion flows out through a filter at the bottom of the reaction vessel. As a result, 160 g of a liquid solution consisting of 65.4% PE, 19.5% D-PE, 2.6% T-PE and 11.4% other product are obtained. Subsequently, two recrystallizations by cooling with water were carried out in the same manner as in Example 1, with a high purity D- consisting of 86.0% D-PE, 13.1% T-PE and 0.7% PE. 27.0 g of PE crystals are obtained.

Example 4

The reaction is carried out in the same manner as in Example 1 except that it is used as a titanium phosphate catalyst. As a result, a liquid solution consisting of 82.9% PE, 10.2% D-PE, 1.1% T-PE and 5.3% other product is obtained. The results showed that the selectivity of D-PE with a conversion rate of PE of 13.0% was 55.4%.

The temperature of the reaction mixture is then lowered to 188 ° C. to crystallize a portion of the unreacted PE and the liquid phase portion flows out through a filter at the bottom of the reaction vessel. As a result, 145 g of a liquid solution consisting of 65.1% PE, 19.4% D-PE, 2.5% T-PE and 11.2% other product are obtained. Subsequently, a high purity D-PE crystal composed of 85.8% D-PE, 12.9% T-PE and 1.0% PE, twice with crystallization by cooling using water in the same manner as in Example 1. 22.9 g are obtained.

EXAMPLES 5-7

The reaction is carried out using several catalysts in the same manner as in Example 2. The results obtained are shown in Table 1.

TABLE 1

* Amount of liquid solution spilled

(A): reaction mixture

(B): spilled liquid solution

Example 8

400 g of starting material PE and 100 g of water in a reaction vessel made of stainless steel with a 5 μm mesh filter made of stainless steel and a liquid solution outlet at the bottom with an internal volume of 1 liter, equipped with a thermometer, a pressure gauge, a heating-stirring device Put it. The starting material consisted of 91.4% PE, 3.8% D-PE, 4.0% B-PE and 0.2% T-PE.

The temperature is raised to 220 ° C. to melt the mixture under N ₂ atmosphere, and then 3.0 g of 85% phosphoric acid is added to carry out the reaction at 220 ° C. for 1 hour. In the course of this reaction, the gauge shows a pressure of 8 kg / cm ² G.

Part of the reaction mixture after the reaction was analyzed and found to consist of 65.3% PE, 10.1% D-PE, 1.3% T-PE and 2.7% other products, and B-PE was undetectable. . As a result of the analysis, the conversion rate of PE was 13.8% and the selectivity to D-PE was 72.3%.

A pump is then used to add 300 g of water to the reaction vessel over 1 hour and to lower the temperature of the reaction mixture to 60 ° C. In this way a portion of the unreacted PE is crystallized and the liquid phase flows out through a filter at the bottom of the reaction vessel. The result is 518 g of a liquid solution consisting of 18.7% PE, 8.4% D-PE, 0.9% T-PE and 2.6% other product. The ratio of D-PE / PEs is 28%.

The solution is cooled to 42 ° C. to precipitate crystals. The resulting crystals are then collected by filtration. The resulting crystals are dissolved in 170 g of water and the solution is cooled to 42 ° C. for recrystallization. Then collected by filtration. The result is 34.5 g of D-PE crystals with high purity consisting of 85.3% D-PE, 13.4% T-PE and 1.0% PE.

Example 9

The reaction was carried out in the same manner as in Example 8 except that the water was changed to sulfolane. As a result, a liquid solution consisting of 63.4% PE, 10.8% D-PE, 1.4% T-PE and 3.4% other product is obtained. B-PE could not be detected. The analysis showed that the conversion of PE was 16.3% and the selectivity to DP-E was 67.2%.

300 g of sulfolane is put into the reaction vessel for 1 hour using a pump and the temperature of the reaction mixture is lowered to 150 ° C. In this way a portion of the PE which has not reacted is crystallized and the liquid phase flows out through a filter at the bottom of the reaction vessel. As a result, 524 g of a liquid solution consisting of 17.9% PE, 8.7% D-PE, 1.3% T-PE and 3.4% other product are obtained. The ratio of D-PE / PEs is 28%.

The liquid solution is cooled to room temperature to crystallize the PEs and the sulfolane is filtered off. As a result, 155 g of crystals are obtained. Continuously, crystallization by cooling was carried out twice using water in the same manner as in Example 1, with high purity D-PE consisting of 84.9% D-PE, 13.8% T-PE and 0.9% PE. 38.0 g of crystals are obtained.

Comparative Example 3

The reaction was carried out in the same manner as in Example 9 except that the reaction temperature was 230 ° C. and the reaction time was 200 minutes. The result is a reaction mixture consisting of 52.2% PE, 12.3% D-PE, 5.0% T-PE and 9.3% other product. The results showed that the conversion of PE was 31.1% and the selectivity to D-PE was 42.2%. The temperature of the reaction mixture is then lowered to crystallize some of the unreacted PE, and the liquid phase portion flows out through a filter at the bottom of the reaction vessel. The result is 552 g of a liquid solution consisting of 14.0% PE, 9.4% D-PE, 4.3% T-PE and 7.8% other product. The ratio of D-PE / PEs is 26.4%.

The crystals of PEs are separated from sulfolane in the same manner as in Example 9 and then recrystallized twice with water. As a result, 53.7 g of crystals consisting of 62.0% D-PE, 37.1% T-PE and 0.7% PE are obtained. The resulting crystals appeared to have crystals with high T-PE content.

Therefore, this comparative example could only obtain crystals with high T-PE content and low purity D-PE when the conversion of PE was carried out up to 31.1%.

Example 10

The reaction was carried out in the same manner as in Example 8 except that 10 g of titanium phosphate was used as a catalyst instead of phosphoric acid. The result is a reaction mixture consisting of 66.7% PE, 9.2% D-PE, 1.0% T-PE and 2.4% other product. The analysis shows that the conversion of PE is 12.5% and the selectivity to D-PE is 69.1%.

The pump is then used to place 300 g of water in the reaction vessel for 1 hour and to lower the temperature of the reaction mixture to 60 ° C. In this way, a part of the unreacted PE is crystallized and the liquid part is discharged through the filter at the bottom of the reaction vessel. The result is 483 g of a liquid solution consisting of 19.7% PE, 7.8% D-PE, 1.0% T-PE and 2.0% other product. 25% soap of D-PE / PEs.

Two successive crystallizations by cooling using water in the same manner as in Example 8 were carried out so that a high purity D-PE crystal composed of 85.5% D-PE, 13.8% T-PE and 0.9% PE was obtained. 30.7 g are obtained.

[Industrial use]

The process for preparing dipentaerythritol according to the present invention can prepare dipentaerythritol itself, which has been produced only by secondary formation, with remarkable and excellent efficiency. The above method provides high quality of dipentaerythritol in an industrial range and at a small cost, can be easily purified, and has a low concentration of impurities formed after dipentaerythritol synthesis reaction.

Claims (13)

Pentaerythritol is condensed in a liquid state at a temperature of 200 ° C to 260 ° C in the presence of an acid catalyst; Lowering the temperature of the reaction mixture to crystallize a portion of pentaerythritol; Removing the crystallized pentaerythritol from the reaction mixture to obtain a reaction mixture containing an increased concentration of dipentaerythritol. The method of claim 1, wherein the temperature of the reaction mixture is lowered to 195 ° C. or less before the conversion of pentaerythritol is 25% or more. The method of claim 1, wherein the temperature of the reaction mixture is lowered to 195 ° C. or less before the weight ratio of dipentaerythritol to pentaerythritol in the reaction mixture is at least 0.18. The method of claim 1, 2 or 3, further comprising separating dipentaerythritol from the reaction mixture containing increased concentrations of dipentaerythritol. Pentaerythritol is condensed in the liquid phase in the presence of an acid catalyst; A process for producing dipentaerythritol, wherein such condensation is carried out in the presence of a polar solvent. The method of claim 5, wherein the dielectric constant of the polar solvent has a value of 15 to 100 at room temperature. The method of claim 6, wherein the polar solvent is dimethylformamide, dimethylsulfoxide, tributylphosphate, sulfolane, 1,3-dimethyl-2-imidazolidinone, water or a mixture thereof. 8. The method of claim 7, wherein said polar solvent is sulfolane, 1,3-dimethyl-2-imidazolidinone, or water. The method of claim 5, wherein the polar solvent is in an amount of 5 to 70% based on the reaction mixture. The method of claim 5, wherein the temperature of the reaction mixture is lowered to crystallize a portion of pentaerythritol and the crystallized pentaerythritol is removed from the reaction mixture to obtain a reaction mixture containing an increased concentration of dipentaerythritol. How to have. The method of claim 10, wherein the portion of pentaerythritol is crystallized by lowering the temperature of the reaction mixture before the conversion of pentaerythritol is 25% or more. The method of claim 10, wherein the temperature of the reaction mixture is lowered to 40-60 ° C. The method of claim 10, further comprising separating dipentaerythritol from a reaction mixture containing increased concentrations of dipentaerythritol.