JPH0830075B2 - Method for producing diacetone sorbose - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to 2,3,4,6-di-O-isopropylidene-L-, which is an important intermediate in the production of ascorbic acid.
The present invention relates to an industrially advantageous method for producing sorbofuranose (abbreviated herein as diacetone sorbose).

PRIOR ART Diacetone sorbose is obtained by reacting acetone and L-sorbose in the presence of a ketalization catalyst. The method of using concentrated sulfuric acid as the catalyst has been well known, but the amount of concentrated sulfuric acid used at this time is about 0.8 to 1 times by weight the amount of L-sorbose, which also serves as a dehydrating agent. is there. Therefore, in order to recover the produced diacetone sorbose, a step of neutralizing sulfuric acid with an appropriate alkali and a step of treating a large amount of salt generated by this neutralization are necessary.

On the other hand, a ketal comprising reacting a sugar with a ketone using perchloric acid, ferric chloride or ferric bromide as a ketalization catalyst and continuously removing water from the reaction medium during this reaction. A method for producing sugar is known (Japanese Patent Publication No. 49-8).
No. 36). In this case, as a method for removing water produced by the reaction by distillation, a method of removing by adding a water-immiscible organic solvent, that is, a method of removing by so-called azeotropic distillation, and a method of removing a mixture of acetone and water by distillation are mentioned. Has been. In the method of removing the water produced by the reaction by azeotropic distillation, acetone is added as a solvent to the reaction medium and a solvent other than water as a third component is added for the reaction, so that even an inert solvent has no adverse effect on the reaction. In addition, it becomes a three-component system of acetone-water-third solvent, and a recovery and purification device for solvents (acetone, third solvent) is required, and the operation becomes complicated. Further, in the method of removing the produced water by distilling a mixture of acetone and water, it is necessary to evaporate a large amount of acetone, that is, at least 250 times or more the amount of sorbose.
Therefore, large and expensive equipment is required to produce diacetone sorbose by this method,
Furthermore, a large amount of heat is required for the distillation of the acetone / water mixture.

Further, conventionally, the water content of acetone used in the production of diacetone sorbose has not been considered, and commercially available acetone is used as it is, and in this case, it generally contains about 1500 ppm or more of water. Further, even when the acetone distilled off from the reaction system is recirculated, at least 300 ppm or more is used in the conventional method.

Problems to be Solved by the Invention In the case of an acid catalyst that is used in large amounts also as a dehydrating agent such as concentrated sulfuric acid in the production of diacetone sorbose, the catalyst cost for the large-scale use and the cost and the large amount required for the neutralization step are required. There is a big problem in industrial implementation such as treatment of inorganic salt.

Further, in the case of the conventional method using perchloric acid, ferric chloride or ferric bromide as a catalyst, in order to remove the produced water by distillation, a solvent as a third component other than acetone and water is used as described above. Is inevitable, or the use of a large amount of acetone is unavoidable. In this case, the yield is not always sufficient, and there remains a problem to be improved industrially.

The above-mentioned problems are more or less observed when other ketalization catalysts are used, and it is desired to develop a production method that further improves the yield of diacetone sorbose in order to reduce the production cost of ascorbic acid. It is rare.

Means for Solving the Problems As a result of various investigations for solving the above problems, the present inventors have found that when highly dehydrated acetone is used as the raw material acetone for the reaction with L-sorbose, the catalyst or acetone is used. Use less amount of diacetone.
The present invention was completed by further finding out findings such as an improvement in the yield of sorbose.

That is, according to the present invention, when L-sorbose is reacted with acetone in the presence of a ketalization catalyst to produce diacetone sorbose, water produced is added to the reaction system while adding acetone having a water content of about 100 ppm or less. Diacetone characterized by reacting while distilling off with acetone
It is a method of manufacturing sorbose.

In carrying out the present invention, first, L-sorbose, acetone (initially charged acetone) and a ketalization catalyst are charged into a reactor to start the reaction. This initially charged acetone generally has a water content of about 100 ppm or less, and preferably about 100 ppm or less, similar to the acetone added during the reaction (added acetone).
The use of 50 ppm or less is further advantageous in achieving the object of the present invention. The amount of initial charged acetone is generally about 6 to 25 times the weight of L-sorbose, preferably about 10 to 14 times the weight.

As the ketalization catalyst used in the method of the present invention, various acid catalysts used in the production of diacetone sorbose may be used as long as they do not interfere with the method of the present invention. For example, concentrated sulfuric acid, hydrogen chloride, perchloric acid, ferric chloride, ferric bromide,
Cupric chloride and cupric bromide described in JP-A-58-55494,
58-167583, copper, iron or their oxides or salts, hydrogen halides, iodine-based catalysts such as iodine and hydroiodic acid described in JP-A-58-167582, JP-A-60-69092 Examples are catalysts such as antimony pentafluoride and antimony pentachloride. Among these, concentrated sulfuric acid, perchloric acid or iodine-based catalysts can be preferably used.

The amount of the catalyst used may be, for example, about 3 to 10% by weight based on the amount of L-sorbose in the case of concentrated sulfuric acid.
Approximately 1/10 compared to the case of using 1500ppm acetone
Or less. In the case of a catalyst such as perchloric acid or iodine type, it is selected from the same range as the conventional one,
Under other reaction conditions similar to the conventional method, the catalyst amount is about 1 /
Even if it is reduced to about 5, diacetone sorbose can be obtained with a similar yield.

Next, in the present invention, the added acetone has a water content of about
Less than 100ppm is used, especially water content is about 50pp
Those of m or less are preferably used. Usually, commercially available acetone contains 1,500 ppm or more of water, and in the present invention, it is dehydrated by an appropriate method to about 100 ppm or less, preferably about 50 ppm or less before use. As this dehydration method, for example, a method in which acetone having a high water content is treated with zeolite having an average pore size of about 3Å and a water content of about 4% or less can be preferably adopted. As the zeolite, one obtained by contacting with heated air or an inert gas (eg, nitrogen, carbon dioxide, argon) and heat-treated at about 200 to 300 ° C. can be advantageously used.

Acetone having a water content of about 100 ppm or less can be obtained by filling the column or tower with the zeolite treated as described above and passing acetone having a high water content. At the time of this contact, in order to increase the contact efficiency between acetone and zeolite, for example, in the case of a zeolite having a water adsorption capacity of 10% by weight, the packing amount should be about 20% by weight or more of the dehydration load in a column or the like. Fill. In this case, the shape of the column is usually such that the adsorbent has a length that allows liquid to pass through at a linear velocity (LV) of 2 to 4 m / hour, and thus the length of the adsorbent does not become too large, so that the dehydration treatment can be performed efficiently. Things are selected.
The flow rate of acetone is selected so that the contact efficiency with the zeolite is high, but it is usually performed at a space velocity (SV) of 2 or less.

In the method of the present invention, the rate of distilling off the produced water together with acetone becomes higher as the rate becomes higher, but a moderate rate is required because the removal efficiency of water decreases. Generally, it is preferable to distill the water-containing acetone in the reaction system at a rate corresponding to about 0.5 to 2 times the amount of initially charged acetone every hour, and more preferable to distill at a rate corresponding to about 0.8 to 1.2 times. Corresponding to this distillation amount,
Acetone with a water content of about 100 ppm or less is added to the reaction system.
The reaction temperature and pressure conditions are selected such that the water produced in the reaction can be efficiently removed. Generally, a temperature of about 30 to 50 ° C. and a condition of about 300 to 500 Torr are preferable, and 40 to 45 ° C.
The condition of 0 to 450 Torr is more preferable.

When the vapor recompression method is adopted for distilling off the produced water and acetone, the water removal efficiency is good, which is industrially advantageous.
As this method, a known method, that is, a method of recompressing the vapor generated in the evaporator and reusing it as a heat source from itself is adopted. The compression temperature at the time of vapor recompression is determined depending on the degree of boiling point increase of the reaction system and the mechanical efficiency at the time of compressing the vapor, but the compression ratio is usually about 2 or less, for example, about 1.4 to Often can be done with 1.6. A specific example of the case where the vapor recompression method is adopted will be described below with reference to FIG.

That is, each reaction raw material of acetone, L-sorbose, and a ketalization catalyst is charged into the reactor (1), and the reaction liquid is circulated through the evaporator (3) using the circulation pump (2). At the beginning of the operation, when the temperature of the circulating liquid is gradually raised by supplying, for example, steam to the shell side of the evaporator (3), the reaction begins to proceed and a part of acetone and a part of generated water are generated. Both start evaporation. Then, the evaporation amount gradually increases, and the temperature of the demister (4) and the compressor (5) is raised. Then, by stopping the supply of water vapor when the temperature of the compressor (5) has been raised to such an extent that it can be operated, the equipment shown in FIG. 1 functions as a normal vapor recompression type reaction evaporator. , The reaction is continued. This steam is a mixed steam containing water in acetone, and the content of water is usually about 200 to 5,000 ppm, although it varies depending on the reaction conditions or the state of the reaction.
Therefore, when forming an azeotropic system, the number can be increased more than this.

Next, this vapor is separated into gas and liquid by a demister (4) and then pressurized by, for example, a roots-type or turbo-type compressor (5) to the shell portion of the evaporator (3) with an increased enthalpy. After being supplied and supplying heat to the reaction solution, it is transferred to the dehydrator (6) as normal drain.

At this time, in order to keep the concentration of the reaction solution constant, an amount of acetone having a water content of about 100 ppm or less, which corresponds to the evaporated amount, should be supplied to the reactor (1) via the liquid feed pump (7) and the residual heat device (8). Thus, the reaction is stably continued. The inert gas contained in the reaction conditions is discharged by the vacuum pump (9).
Here, as the acetone to be added, it is advantageous to repeatedly use the one treated with the dehydration device (6) in the reaction process, and the method using zeolite as described above is advantageously applied to the dehydration treatment. It can be dehydrated to a water content of about 100 ppm or less, preferably about 50 ppm or less.

The vapor recompression type steam machine used in the present reaction method can be variously combined depending on its type, model and the like. For example, various types such as plate type and tube type for the evaporator, and the circulation method of the reaction solution,
A method such as forced flow or natural flow can be appropriately selected in consideration of the reaction characteristics and the physical properties of the reaction solution. It is also possible to select the concentration of the reaction solution and the reaction rate by increasing or decreasing the amount of acetone to be added. This method can be continuous by withdrawing the reaction solution from the system while continuing the reaction, or it is possible to perform the reaction batchwise, and it should be selected according to the characteristics of the reaction system and equipment. You can

In the present invention, recovery and purification of diacetone sorbose after completion of the reaction can be carried out by known methods. For example, after adding an alkali (eg, caustic soda) in an amount about 1.1 times the neutralization equivalent to the reaction-terminated solution, distilling off the contained acetone to form an aqueous solution, diacetone sorbose is extracted with benzene, and concentrated to dryness. By doing so, crystals of diacetone sorbose are obtained.

EXAMPLES The present invention will be described more specifically below with reference to Examples along with Comparative Examples.

Example 1 1.5 l of zeolite (manufactured by Toyo Soda Co., Ltd., Zeolum 3AGS) was thinly spread on a metal flat plate, air-dried for 1 day, and then heated in a constant-temperature electric dryer at 230 ° C. for 7 hours to have a water content of 2%. After cooling this zeolite to room temperature, put it on a glass column (30 mmφ x 2000 mm).
Fill with 1100g, commercial acetone (water content 2000ppm) 15l
Was passed through at a space velocity (SV) of 2 to obtain acetone having a water content of 40 ppm.

1,400 ml of the above dehydrated acetone, 100 g of L-sorbose and 4 ml of concentrated sulfuric acid were put into a 3 l flask equipped with a stirrer and a cooling tube, and the mixture was heated under a reduced pressure (480 Tor) in a warm bath (internal temperature 45 ° C).
In r), the produced water-containing acetone was distilled off at a rate of about 1.25 l / hr, while the above-mentioned dehydrated acetone (water content 40 ppm) was added at a rate of about 1.25 l / hr and maintained for 10 hours.

After completion of the reaction, the solution was neutralized with an aqueous solution of 30% caustic soda equivalent to 1.1 times mol of the added sulfuric acid, acetone was distilled off to give an aqueous solution, which was then extracted with benzene to obtain a benzene solution of diacetone sorbose. This is evaporated to dryness and diacetone.
127.1 g (yield 88.0%) of sorbose was obtained.

Example 2 The reaction was carried out in the same manner as in Example 1 except that the reaction temperature was changed to 30 ° C., 35 ° C. and 40 ° C. and the reaction time was 12 hours. As a result, the yield of diacetone sorbose is shown in Table 1. It was the street.

Comparative Example 1 When the reaction was carried out in the same manner as in Example 1 except that a commercially available product (water content 1,800 ppm, manufactured by Wako Pure Chemical Industries, Ltd.) was used as the added acetone instead of dehydrated acetone, diacetone.
The yield of sorbose was 113.5 g (78.6% yield).

Comparative Example 2 L-sorbose 100 g, acetone (water content 1,500 ppm) 140
0 ml and 30 ml of concentrated sulfuric acid were put into a 3 l flask and reacted at 30 ° C. for 1.5 hours while stirring. Then, when acetone sorbose was obtained by the same separation and purification method as in Example 1, the yield was 94.6 g (yield 65.5%). When the reaction was carried out in the same manner as above using 53 ml of concentrated sulfuric acid, the yield of diacetone sorbose was 115.5 g (yield 8
It was 0.0%).

Example 3 Acetone dehydrated according to the method of Example 1 (water content: 35
ppm) 1400 ml, L-sorbose 100 g and 0.44 ml of an aqueous solution containing 61% perchloric acid (0.4 g as perchloric acid) are placed in a 3 liter flask equipped with a stirrer and a cooling tube, and water is formed under reduced pressure in a warm bath. While the acetone was distilled off at a rate of about 1.25 l / hr, dehydrated acetone (water content 35 ppm) was added at a rate of about 1.25 l / hr, and the temperature was kept at 45 ° C for 9 hours.
After completion of the reaction, 4 ml of 30% aqueous sodium hydroxide solution was added to neutralize perchloric acid, acetone was distilled off to give an aqueous solution, which was then extracted with benzene to obtain a benzene solution of diacetone sorbose. This was evaporated to dryness and diacetone sorbose
131.0 g (yield 90.7%) was obtained.

Example 4 128.1 g of diacetone sorbose was reacted by the method of Example 3 except that 1.2 g of iodine was used in place of perchloric acid and the water content of dehydrated acetone was 50 ppm.
(Yield 88.7%) was obtained.

Comparative Example 3 10.0 g of L in 200 ml of commercial acetone (water content 1500 ppm)
-Add sorbose and 127 mg of iodine in a 60 ° C warm bath 6
Stirring was continued for hours. During this period, 30 g of Molecular Sieves 3A (manufactured by Wako Pure Chemical Industries, Ltd.) was incorporated between the reactor and the cooling tube (diameter 2 cm column, packing length 13 cm), and the reflux solvent was dried.

After completion of the reaction, 0.5 ml of a 30% aqueous sodium hydroxide solution was added, acetone was distilled off to form an aqueous solution, and this was extracted with benzene to obtain a benzene solution of diacetone sorbose. This was evaporated to dryness and diacetone sorbose 12.10 g (yield 83.8
%) Was obtained. In this experiment, the water content in acetone refluxed to the reactor was as shown in Table 2.

Example 5 740 kg of zeolite (Zeorum 3ASG, Toyo Soda) was packed in a dehydration adsorption tower (1000 mmφ × 1700 mm), and nitrogen gas preheated to 230 ° C. was blown at 500 Nm ³ for 4.5 hours for treatment.

Acetone (water content 200-3000pp
m) was passed at 1500 l / hr (SV = 1.5, LV = 2 m / hr) to obtain 6325 l of dehydrated acetone (water content of 50 ppm or less).

L-sorbose (50 kg) and iodine (0.6 kg) were added to the above dehydrated acetone (700 l) and the reaction was carried out at 46 ° C for 9 hours. For this reaction, as shown in FIG. 1, a reactor, a plate-type evaporator, and an apparatus in which a vapor recompression type evaporation facility is configured by connecting with a compressor are used. External steam was supplied at 1.9 kg / cm ² G and heated. As a result, the temperature inside the plate became about 55.5 ° C after about 60 minutes, and the plate was in a normal operating state. After this, water-containing acetone (water content 20
(0 to 3000 ppm) was distilled off, while the dry acetone obtained as described above was kept at 46 ° C. while being fed in the same amount as the distilled acetone, and the reaction was continued.

After completion of the reaction, the reaction solution was cooled and neutralized, then acetone was distilled off and benzene was extracted. Benzene was distilled off from this extraction, and the residue was diacetone sorbose 63.5 kg.
(88% yield) was obtained.

Effects of the Invention According to the present invention, diacetone sorbose useful as an intermediate for producing ascorbic acid can be industrially advantageously produced. That is, the production method of the present invention is characterized by using acetone having a water content of about 100 ppm or less when producing diacetone sorbose, and requires less ketalization catalyst or acetone than the conventional method. In addition, the effect of increasing the yield of the target product can be obtained.

For example, in the case of a catalyst that has been used also as a dehydrating agent, such as concentrated sulfuric acid, the amount used is about 1/10 or less of that used in the conventional method, and the produced water can be easily removed by distillation. . For this reason, the amount of alkali required for neutralization after the reaction may be extremely small, and the amount of salt produced may be small, which facilitates recovery and purification of the target substance. Further, since the produced water can be easily distilled off together with acetone, for example, when using perchloric acid as a catalyst, the total amount of acetone used is smaller than that in the conventional method, and a removal method by azeotropic distillation is not particularly required. This is also advantageous. Further, when other ketal catalyst is used, the yield of diacetone sorbose can be further improved as compared with the conventional method.

[Brief description of drawings]

FIG. 1 is an example of a process diagram for carrying out the method of the present invention, in which (1) is a reaction tank, (A) is a raw material charging port,
(2) is a circulation pump, (3) is an evaporator, (4) is a demister, (5) is a compressor, (6) is a dehydrator, (7) is a liquid feed pump, (8) is a preheater, and ( 9) shows a vacuum pump and (St) shows a steam supply port.

Claims (1)

[Claims] 1. When L-sorbose is reacted with acetone in the presence of a ketalization catalyst to produce diacetone sorbose, the initial charge of acetone is about 100 p water content.
Acetone below pm is used, and the water content of the reaction system is about 100p
A process for producing diacetone sorbose, which comprises reacting while distilling off produced water together with acetone while adding acetone at pm or less.