JP2863296B2 - Method for producing dipentaerythritol - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing dipentaerythritol, and more particularly, to a method for producing dipentaerythritol (hereinafter referred to as dipentaerythritol (hereinafter referred to as “dipentaerythritol”) by a dehydration condensation reaction of pentaerythritol using an acid catalyst.
D-PE).

[Prior Art] D-PE is produced as a by-product during the synthesis reaction of pentaerythritol (hereinafter abbreviated as PE), that is, when PE is produced by reacting formaldehyde with acetaldehyde in the presence of an alkali. Is a general method obtained by separating and purifying. To increase the by-product rate of D-PE in this reaction, (1) the molar ratio of formaldehyde to acetaldehyde charged to the reaction system is made smaller than 4 which is the theoretical molar ratio.

(2) The reaction is carried out by increasing the concentrations of formaldehyde, acetoaldehyde and alkaline agent.

(3) The reaction is performed by adding and dissolving PE in an aqueous formaldehyde solution.

Are proposed, but the methods (1) and (2) are
Since the total yield of PE and D-PE is poor and the quality of the main product, PE, is poor, (4) a part of formaldehyde, alkali, and acetaldehyde is charged in advance, and Formaldehyde,
A method has been proposed in which an alkali and acetaldehyde are simultaneously added dropwise while maintaining the respective molar ratios at or above the theoretical ratio and the reaction temperature is maintained at 50 ° C. or lower (Japanese Patent Publication No. 1-44689).

Also known is a method of synthesizing polypentaerythritol using PE with phosphoric acid, sulfuric acid or the like. (USP 246204
7) However, the method for producing D-PE by the reaction between acetaldehyde and formaldehyde still has the following problems.

PE and D-PE must be separated and recovered from impurities such as by-product sodium formate, bispentaerythritol monoformal, and excess formaldehyde or self-condensate of acetaldehyde / formaldehyde, which complicates the purification process.

The amount of D-PE that can be produced depends on the amount of PE that is produced.
15% is the limit and cannot meet recent demand growth.

On the other hand, known methods for synthesizing a polypentaerythritol mixture from PE using phosphoric acid, sulfuric acid, etc.
No means for selectively synthesizing PE is described.

According to the findings of the present inventors, when PE is dehydrated and condensed using an acid catalyst, D-PE is produced, and the produced D-PE is successively tripentaerythritol (hereinafter, abbreviated as T-PE). , And further into high molecular weight polypentaerythrylol. Alternatively, an intramolecular condensate may be generated, and this cannot be put to practical use as it is. Therefore, the present inventors first performed a condensation reaction of PE in the liquid state molten state at a temperature of 200 to 260 ° C in the presence of an acid catalyst, and the temperature of the reaction solution was reduced to 195 ° C or lower before the conversion of PE became 25%. And a method of removing a reaction solution having a higher concentration of D-PE by crystallizing a part of PE.

[Problems to be Solved by the Invention] However, the D-PE production method by the condensation reaction of PE in the presence of the above acid catalyst still has the following problems. Since PE is reacted in a liquid-phase molten state, the reaction temperature is inevitably higher than the melting point of the reaction mixture, and particularly high at 240 ° C. or more in the early stage of the reaction. Although it is possible to lower the temperature as the reaction proceeds, the initial high temperature may increase the generation of impurities other than T-PE. After the reaction, a part of the unreacted PE is crystallized, and a reaction solution having a high D-PE concentration is taken out. In this method, the eutectic composition of PE and D-PE (D-PE
/ PE = 20/80) with a melting point of about 185 ° C. At such a high temperature, it is extremely difficult to perform filtration with strict temperature control, and the filter is likely to be clogged during the filtration operation, or the concentration of D-PE tends to be insufficient. In addition, the recovery rate of the produced D-PE is not satisfactory.
-The concentration of PE cannot be higher than 20%.

[Means for Solving the Problems] The present inventors have conducted intensive studies in order to solve the above problems, and conducted a dehydration condensation reaction of PE using an acid catalyst.
Before the concentration of T-PE formed sequentially after the formation of D-PE increases, the temperature of the reaction solution is lowered to stop the reaction,
If a method of crystallizing a part of the solution and taking out a reaction solution in which D-PE is concentrated is performed in the presence of a polar solvent, impurity by-products in the reaction are reduced, and the reaction in which D-PE is concentrated is performed. The present inventors have found that the filtration operation for removing the liquid is facilitated and that the concentration of D-PE is further advanced, thereby completing the present invention.

That is, the method for producing dipentaerythritol of the present invention, when synthesizing dipentaerythritol by performing a condensation reaction of pentaerythritol in a liquid phase state with an acid catalyst,
The reaction is carried out in the presence of a polar solvent, and before the conversion of pentaerythritol becomes 25% or more, the temperature of the reaction solution is lowered to crystallize a part of pentaerythritol,
It is characterized in that a reaction solution having an increased concentration of dipentaerythritol is taken out.

The polar solvent used in the present invention refers to a solvent composed of molecules having a dipole moment, and has a dielectric constant of 15 at room temperature.
That's all. For example, dimethylformamide, dimethyl sulfoxide, tributyl phosphate, sulfolane, 1,3-dimethyl-2-imidazolidinone, water and the like. Of these, a sulfonane having a high boiling point and being stable to an acid, 1,3-dimethyl-2-imidazolidinone, is also preferable. However, surprisingly, even if water is used in the reaction, D
-It was also found to be excellent in the step of concentrating and recovering PE.

The amount of these polar solvents used in the reaction is 5 to the reaction solution.
It is about 70%, more preferably about 10-30%.

The acid catalyst used in the present invention refers to a substance which is usually used as a catalyst in the dehydration condensation reaction of alcohol, and examples thereof are shown in "Catalyst Lecture Vol. 8, page 278, Table 13.3". For example, mineral acids such as phosphoric acid and sulfuric acid, inorganic salts such as metal sulfates and metal phosphates, and clay minerals such as montmorillonite are preferred, and phosphoric acid and metal phosphates are particularly preferred. As the metal species of the metal phosphate, for example, Al, B, Fe, Cr, Ti, Cu, Ni,
Zn, Zr and the like.

The optimal amount of the catalyst varies depending on the type of the catalyst. For example, in the case of phosphoric acid, 0.01 to 3%, preferably 0.1 to 2%
It is. When the amount is small, the reaction rate is low, and when the amount is large, by-products of impurities increase.

In this reaction, PE is reacted in a liquid phase state, and it is preferable that all PEs are in a liquid phase under the reaction.

In the present invention, since the reaction is performed in the presence of a polar solvent,
The temperature at which all the PEs are in the liquid phase dissolved state varies considerably depending on the type and amount of the solvent used. However, considering the reaction rate and impurity by-product, the reaction temperature is preferably about 180 to 230 ° C.

As described above, PE undergoes a dehydration condensation reaction by an acid catalyst to produce D-PE. However, once the D-PE is formed, even higher molecular weight polypentaerythritol is formed, and it is essentially difficult to prevent these series of sequential side reactions. In order to prevent this side reaction, it is most effective to lower the D-PE concentration in the reaction solution. Therefore, in the present invention, the reaction solution temperature is lowered before the PE conversion reaches 25% or more. To stop.

Here, the conversion rate of PE will be described. Commercially available PEs generally include D-PE and bispentaerythritol monoformal (hereinafter abbreviated as B-PE) in the range of 3 to 3 respectively.
B-PE contains one molecule of B by this reaction.
-It is considered that two molecules of PE and one molecule of formalin are generated from PE. Therefore, the conversion rate of PE in the present invention is based on the sum of the moles of PE before the reaction and 2 moles of B-PE,
Since it is represented by the ratio of the number of moles of PE consumed in the reaction, Becomes

In the present invention, D-PE in the reaction solution is reduced by reducing the conversion rate of PE.
However, it is difficult to separate and recover D-PE from a reaction solution having such a low concentration, and the cost is increased. Therefore, in the present invention, the reaction solution is cooled after the reaction, the temperature of the solution is lowered, a part of the unreacted PE in the solution is crystallized, and the solid is separated into a solid and a liquid to obtain D.
The above problem could be solved by taking out the reaction solution having a higher PE concentration.

By this operation, it is possible to recover a reaction solution in which D-PE is increased to 0.25 or more from a solution in which the weight ratio of D-PE / PEs is about 0.1. (PEs indicate the sum of PE, D-PE, T-PE and other products.) The optimal temperature for solid-liquid separation is the composition of the reaction solution, the type of polar solvent used, the amount used, etc. Temperature is about 40 to 160 ° C. The optimum amount of the polar solvent used in this step is preferably larger than 10 to 30% of the optimum amount in the reaction from the viewpoint of operability of filtration, and is preferably about 30 to 70% with respect to the total liquid amount.

A filter is generally used as a solid-liquid separation method for taking out a liquid in which D-PE is concentrated. As the reactor type, a stirred tank type batch type, a tube type flow type, etc. are considered, and any type can be adopted.For example, if a stirred tank type reactor having a filter inside the reactor is used, solidification after solid-liquid separation is performed. Phase PE
Has the advantage that it remains in the reactor and can be directly used for the next reaction.

Thus, from a reaction solution having a conversion rate of PE of about 13%, a D-PE concentration of about 10% by weight, and a T-PE concentration of about 1% by weight based on PEs in the reaction solution, D-PE was increased to about 25% by weight or more. A concentrated liquid can be obtained. The D-PE thus obtained is separated and purified by a general separation means such as fractional crystallization to give a product,
Unreacted PE can be circulated again to the reactor and used as a raw material.

[Examples] Hereinafter, the present invention will be described with reference to examples.

Example 1 A reactor equipped with a stainless steel inner volume 1, a thermometer, a pressure gauge, a heating / stirring device, and a stainless steel 5 μm mesh filter and a liquid outlet at the bottom was charged with 400 g of raw material pentaerythritol and water. 100g was charged.
The composition of this raw material is 91.4% by weight of PE (hereinafter, the composition is
), D-PE3.8%, B-PE4.0%, T-PE0.2
%Met. The temperature was raised to 220 ° C. in an N ₂ atmosphere, 3.0 g of 85% phosphoric acid was added thereto, and the mixture was reacted at 220 ° C. for 140 minutes. During this time, the pressure showed 8 kg / cm ² G.

After the reaction, when a part of the reaction solution was taken out and analyzed,
It was 65.3% PE, 10.1% D-PE, 1.3% T-PE, and 2.7% other products. B-PE was not detected.

As a result, the conversion of this reaction was 13.8%, and the selectivity for D-PE was 72.3%. Next, 300 g of water was fed to the reactor by using a pump in one hour, and the liquid temperature was adjusted to 60 ° C. As a result, a part of the unreacted PE was crystallized and the liquid phase was extracted through a filter at the bottom. As a result, 18.7% of PE and 8.4 of D-PE were obtained.
%, T-PE 0.9% and other products 2.6%
8 g were obtained.

As a result, the recovery rate of D-PE was 86%, and the ratio of D-PE / PEs was 28%.

Example 2 A reaction operation was carried out in the same manner as in Example 1 except that sulfolane was used instead of water. After the completion of the reaction, a part of the reaction solution was taken out and analyzed. As a result, PE 63.4%, D-PE 10.8%, T-PE
It was 1.4% PE and 3.4% other products. B-PE was not detected.

Thus, the conversion of this reaction was 16.3%, and the selectivity for D-PE was 67.2%. Next, 300 g of sulfolane was added to the reactor.
Was sent for 1 hour using a pump, and the liquid temperature was set to 150 ° C. As a result, a part of the unreacted PE was crystallized, and the liquid phase was extracted through a filter at the bottom.
524 g of a liquid having a composition of 8.7% of D-PE, 1.3% of T-PE and 3.4% of other products was obtained.

From this, the recovery of D-PE was 84%, and the ratio of D-PE / PEs was 28%.

Comparative Example 1 A reaction was carried out in the same manner as in Example 2 except that the reaction time was changed to 200 minutes and the reaction temperature was set to 230 ° C., and 52.2% of PE, 12.3% of D-PE,
A reaction solution having a composition of 5.0% PE and 9.3% of other products was obtained.

The results of this reaction were as follows: conversion rate 31.1%, D-PE selectivity 42.2%.
%Met.

Comparative Example 2 500 g of pentaerythritol as a raw material, 85 g of phosphoric acid content of 3 g without adding a solvent, and a reaction temperature of 240 ° C.
After reacting for 5 minutes, the temperature was lowered to 230 ° C. and the reaction was carried out for 1 hour. As a result, a reaction solution containing 80.7% of PE, 11.4% of D-PE, 1.3% of T-PE, and 5.4% of other products was obtained.

The conversion of this reaction was 14.8% and the D-PE selectivity was 58.3.
%Met. The reaction solution was cooled to 188 ° C. and the liquid phase was extracted. As a result, 65.4% of PE, 19.5% of D-PE, 2.6% of T-PE,
160 g of a liquid having a composition of 11.4% of other products were obtained. The recovery of D-PE was 55%.

Example 3 Except for using 10 g of Ti phosphate instead of phosphoric acid as a catalyst,
The reaction operation was performed in the same manner as in Example 1. After the reaction was completed, a part of the reaction solution was taken out and analyzed.
It was 9.2% PE, 1.0% T-PE, and 2.4% other products. B-PE was not detected.

As a result, the conversion of this reaction was 12.5%, and the selectivity for D-PE was 69.1%. Next, 300 g of water was sent to the reactor using a pump in one hour, and the liquid temperature was adjusted to 60 ° C. A portion of the unreacted PE was crystallized in this manner, and the liquid phase was extracted through a filter at the bottom. As a result, 19.7% of PE and 7.8 D-PE were obtained.
%, 1.0% of T-PE and 2.0% of other products
3 g were obtained.

From this, the recovery of D-PE was 82%, and the ratio of D-PE / PEs was 25%.

[Effects of the Invention] According to the method of the present invention, dipentaerythritol, which was conventionally produced only as a by-product, can be efficiently produced mainly, and the concentration of tripentaerythritol and other impurities is low and purification is easy. Thus, a high-quality product can be obtained, which is extremely advantageous industrially.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-261736 (JP, A) JP-A-4-208242 (JP, A) JP-A-57-139028 (JP, A) 501470 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) C07C 43/13, 41/09, 41/40

Claims (1)

(57) [Claims] (1) When synthesizing dipentaerythritol by subjecting pentaerythritol to a condensation reaction in a liquid phase state with an acid catalyst, the reaction is carried out in the presence of a polar solvent, and before the conversion of pentaerythritol becomes 25% or more. A method for producing dipentaerythritol, wherein the temperature of the reaction solution is lowered to partially crystallize pentaerythritol, and a reaction solution having a higher concentration of dipentaerythritol is taken out.