JPS6345292A - Production of diacetone sorbose - Google Patents

Abstract

PURPOSE:To obtain the titled compound useful as an intermediate for ascorbic acid, etc., on an industrial scale at a low cost, by reacting L-sorbose under the addition of acetone having low water-content in the presence of a ketalization catalyst while distilling out produced water together with acetone. CONSTITUTION:The objective compound is produced by reacting L-sorbose with acetone in the presence of a ketalization catalyst (e.g. concentrated sulfuric acid, etc.). The reaction is carried out by charging dehydrated acetone having a water-content of <=100ppm, L-sorbose and concentrated sulfuric acid into a reactor, reacting the components in a hot bath of 45 deg.C under reduced pressure while adding dehydrated acetone having a water-content of <=100ppm to the system and distilling out acetone containing water produced by the reaction. The reaction product is neutralized with an aqueous solution of sodium hydroxide, acetone is distilled out, the obtained aqueous solution is extracted with benzene and benzene is distilled out to obtain the objective compound.

Description

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

PRIOR ART Diacetone sorbose is obtained by reacting acetone with L-sorbose in the presence of a ketalization catalyst. The method of using concentrated sulfuric acid as a catalyst is well known, but the amount of concentrated sulfuric acid used in this case is approximately 0.8 to 1 times as large as the amount of L-sorbose as it also serves as a dehydrating agent. is necessary. Therefore, in order to recover the produced diacetone sorbose, it is necessary to neutralize the sulfuric acid with a suitable alkali and to treat a large amount of salt produced by this neutralization.

On the other hand, ketalization is achieved by reacting sugars with ketones 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 (Special Publication No. 1973-
No. 836). In this case, methods for removing the water produced by the reaction by distillation include a method of removing by adding a water-immiscible organic solvent, that is, a so-called azeotropic distillation, and a method of removing a mixture of acetone and water by distillation. It is being The method of removing reaction product water by azeotropic distillation involves adding acetone as a solvent to the reaction medium and a third component outside of the water to stimulate the reaction, so even if the solvent is an inert solvent, it may have an adverse effect on the reaction. In addition, it is a three-component system of acetone, water, and a third solvent, which requires recovery and purification equipment for the solvents (acetone and third solvent), and the operation becomes complicated.

Furthermore, in the method of removing 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 the amount of sorbose m. Therefore, large and expensive equipment is required to produce diacetone sorbose by this method, and also a large amount of heat is required for the distillation of the acetone/water mixture.

Furthermore, conventionally, no consideration has been given to the water content of acetone used in the production of diacetone/sorbose, and commercially available acetone is used as is, and in this case, it generally contains about 1500 ppm or more of water.

Furthermore, even when acetone distilled off from the reaction system is recycled, in the conventional method, at least 300 ppm or more is used.

Problems to be Solved by the Invention In the case of acid catalysts such as sulfuric acid that are used in large quantities as a dehydrating agent in the production of diacetone/sorbose, the cost of the catalyst for its large fin' and the cost required for the neutralization process. However, there are major problems in industrial implementation such as processing of large amounts of inorganic salts.

In addition, in the case of conventional methods using perchloric acid, ferric chloride or ferric bromide as catalysts, distillation of the water produced requires the following steps:
As mentioned above, it is unavoidable to use a solvent as a third component in addition to acetone and water, or to use a large amount of acetone, and in this case, the yield is not necessarily sufficient and there is a need for industrial improvement. A scolding mark is left behind.

The above-mentioned problems also occur to a greater or lesser extent when other ketalization catalysts are used, and in order to reduce the production cost of ascorbic acid, it is desirable to develop a production method that further improves the yield of diacetone/sorbose compared to conventional methods. It is rare.

Means for Solving the Problems The present inventors have conducted various studies to solve the above problems, and have found that if highly dehydrated acetone is used as the raw material for the reaction with sorbose, the catalyst or They discovered that the amount of acetone used was small and the yield of diacetone/sorbose was improved, and after further research, they completed the present invention.

That is, in the present invention, when producing diacetone sorbose by reacting L-sorbose and acetone in the presence of a ketalization catalyst, the water content of the reaction system is about 100 pp.
This is a method for producing diacetone sorbose, which is characterized in that the reaction is carried out while adding m or less acetone and distilling off the water produced together with the acetone.

In practicing the present invention, sorbose, acetone (initial charge of acetone), and ketalization catalyst are first charged to a reaction vessel to initiate the reaction. This initial charge of acetone does not necessarily have a water content of about 100 ppm or less, as long as it is used within the range described below. However, in general, the water content is about lo o like the acetone added during the reaction (added acetone).
It is more advantageous to use less than ppm, preferably less than about 50 ppm, in order to achieve the objectives of the present invention. The amount of acetone initially charged is generally about 6 to 25 times the weight of the amount of L-sorbose charged, preferably about 10 to 1 = 1
It's twice as heavy.

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, cupric bromide as described in JP-A-58-55494,
Copper, iron or their oxides as described in JP-A-58-167583, salts, hydrogen halides, JP-A-58-16
Examples include iodine-based catalysts such as iodine and hydroiodic acid described in No. 7582, and catalysts such as antimony pentafluoride and andimony pentachloride described in JP-A No. 60-69092. Among these, concentrated sulfuric acid, perchloric acid or iodine catalysts are preferably used.

For example, in the case of concentrated sulfuric acid, the amount of catalyst used may be about 3 to 10% by weight based on the amount of L-sorbose, which is about 1/10 or more compared to the conventional case of using acetone with a water content of about 1500 ppm. The following is fine. In the case of perchloric acid or iodine-based catalysts, they are selected from the same range as conventional methods, but if other reaction conditions are similar to conventional methods, even if the catalyst amount is reduced to about 115%, diacetone/sorbose are obtained with similar yields.

Next, in the present invention, the added acetone has a water content of about 1
00 ppm or less is used, and in particular, one with a water content of about 50 ppm or less is preferably used. usually,
Commercially available acetone contains 1500 pp111 or more of water, and in the present invention, this is used after being dehydrated to about 100 ppm or less, preferably about 50 ppm or less, by an appropriate method. As this dehydration method, for example, a method of treating acetone with a high water content with a zeolite having an average pore size of about 3 and a water content of about 4% or less can be preferably employed. The zeolite can be brought into contact with heated air or an inert gas (e.g., nitrogen, carbon dioxide, argon) to produce a
Those heat-treated at 0° C. can be advantageously used.

Acetone with a water content of about 100 ppm or less can be obtained by filling a column or tower with the zeolite treated as described above and passing acetone with a high water content through the column or tower. During this contact, in order to increase the contact efficiency between acetone and zeolite, for example, in the case of zeolite with a water adsorption capacity of 10% by weight, the column should be packed so that the packing m is about 20 times the dehydration load or more. Fill. In this case, the shape of the column is usually linear velocity (LV) = 2 to 4
An adsorbent whose length is not too large and can be efficiently dehydrated is selected so that it has a cross-sectional area that allows liquid to pass through at m/hour. The flow rate of acetone is selected so as to increase the efficiency of contact with the zeolite, and is usually carried out at a space velocity (SV) of 2 or less.

In the method of the present invention, the reaction rate increases as the rate of distillation of the water produced together with acetone increases, but an appropriate rate is required because the water removal efficiency decreases. In general, it is preferable to distill off the water-containing acetone in the reaction system at a rate corresponding to about 0.5 to 2 times the amount of acetone initially charged per hour, and preferably at a rate corresponding to about 0.8 to 1.2 times the amount of acetone initially charged. It is even more preferable to remove it. Corresponding to this distilled amount, acetone with a water content of about 100 ppm or less is added to the reaction system. In addition, the reaction temperature and pressure conditions are selected such that the water produced in the reaction is efficiently removed, and generally a temperature of about 30 to 50°C and a condition of about 300 to 500 Torr are preferred, and a temperature of 40 to 450 Torr at 40 to 45°C is preferable. To
The conditions of rr are more preferred.

For the distillation of the produced water and acetone, a vapor recompression method is employed, which has good water removal efficiency and is industrially advantageous. This method itself is a known method, that is, a method of recompressing the steam generated in the evaporator and reusing it as its own heat source. The compression temperature during vapor recompression is determined each time based on the degree of rise in the boiling point of the reaction system and the mechanical efficiency when compressing the vapor, but the compression ratio is usually approximately 2.
Below, for example, it can often be implemented at about 1.4 to 1.6. A specific example of the case where the vapor recompression method is adopted will be explained below along with the process diagram shown in FIG.

That is, each reaction raw material of acetone, sorbose, and ketalization catalyst is charged into a reactor (1), and the reaction liquid is circulated via an evaporator (3) using a circulation pump (2). At the beginning of operation, on the shell side of the evaporator (3),
If the temperature of the circulating fluid is gradually increased, for example by supplying water vapor, part of the acetone and part of the produced water will both start to evaporate as the reaction begins to proceed.

Then, the amount of evaporation gradually increases, and the temperatures of the demister (4) and compressor (5) are raised. By stopping the supply of steam when the temperature of the compressor (5) has risen to a point where it can be operated, the equipment shown in Figure 1 will function as a normal vapor recompression type reaction evaporator. , the reaction continues. This steam is a mixed steam containing water in acetone, and the water content is usually about 200 to 5,000 ppm, although it varies depending on the reaction conditions and state of the reaction.
If an azeotropic system is formed, the amount can be increased further.

Next, this vapor is separated into gas and liquid in a demister (4), and then pressurized by a roots-type or turbo-type compressor (5), and is sent to an evaporator (3) with increased enthalpy.
), and after supplying heat to the reaction liquid, it is normally transferred to the dehydrator (6) as a drain.

At this time, in order to keep the concentration of the reaction solution constant, acetone m with a water content of about 100 ppm or less corresponding to the evaporated amount is supplied to the reactor (1) via the liquid feed pump (7) and preheater (8). This allows the reaction to continue stably. Inert gas included in the reaction conditions is exhausted by a vacuum pump (9). Here, the acetone to be added is the dehydrator (
It is advantageous in the reaction process to repeatedly use the product treated in step 6), and the method using zeolite as described above can be advantageously applied to the dehydration treatment, and the water content is about 100.
It is dehydrated to less than ppm, preferably less than about 50 ppm.

Regarding the vapor recompression type steam machines used in this reaction method, various combinations are possible depending on their types, models, etc. For example, various types of evaporators are available, such as plate type and tube type, and methods for circulating the reaction liquid, such as forced or gravity flow, are selected as appropriate, taking into consideration the characteristics of the reaction and the physical properties of the reaction liquid. can. It is also possible to select the concentration of the reaction solution and the reaction rate by increasing or decreasing the amount of acetone added. This method can be carried out continuously by drawing the reaction liquid out of the system while the reaction continues, or it can be carried out batchwise, and the method can be selected depending on the characteristics of the reaction system and equipment. Can be done.

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 (e.g., caustic soda) of about 1.1 times the mole of the neutralization equivalent to the reaction completed solution, the acetone contained is distilled off to form an aqueous solution, and diacetone/sorbose is extracted with benzene and concentrated. By drying, diacetone sorbose crystals are obtained.

EXAMPLES The present invention will be explained in more detail by giving examples as well as comparative examples.

Example 1 Zeolite (manufactured by Toyo Soda, Zeorum 3 AG S)1.
5Q was spread thinly on a metal flat plate, air-dried for one day, and then heated at 230° C. for 7 hours in a constant temperature electric dryer to reduce the moisture content to 2%. After cooling this zeolite to room temperature, a glass column (30
(mmφ
SV) 2 to obtain acetone with a water content of 40 ppm.

1.400 d of the above dehydrated acetone, 100 d of L-sorbose
g and concentrated sulfuric acid 4- were placed in a 3Q flask equipped with a stirrer and a condenser, and in a hot bath (inner temperature 45°C) under reduced pressure (480 Torr), acetone containing water was added every hour to 1.2512 kg. The mixture was distilled off at a rate of 1.25 f2 per hour, while the dehydrated acetone (water content 40 ppm) was added at a rate of 1.25 f2 per hour for 10 hours.

After the reaction, 30% equivalent to 1.1 times the mole of the added sulfuric acid.
After neutralizing with an aqueous caustic soda solution and distilling off acetone to obtain an aqueous solution, this was extracted with benzene to obtain a benzene solution of diacetone/sorbose. This was evaporated to dryness to obtain 1271 g (yield: 88.0%) of diacetone sorbose.

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 was the first. It was as shown in the table.

Table 1 Comparative Example 1 When reacted in the same manner as in Example 1 except that a commercially available product (water content t, soopm, manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of dehydrated acetone as added acetone, diacetone・What is the yield of sorbose? 13゜5g (yield 78.6
%)Met.

Comparative Example 2 100 g of L-sorbose, acetone (water content t, 5oo
400 d of pp 儂) l and 30 ml of concentrated sulfuric acid were placed in a 3Q flask and reacted for 1.5 hours at 30° C. with stirring. Hereinafter, acetone sorbose was obtained by the same separation and purification method as in Example 1, and the yield was 94.6 g.
(yield 65.5%). In the above, concentrated sulfuric acid 5
When reacting in the same manner using 3-, the yield of diacetone sorbose was 115.5 g (yield 80.0%)
Met.

Example 3 Acetone dehydrated according to the method of Example 1 (water content 35
pI)+m)l 400J, L-sorbose 1QQg and 0.44y4 (0.4g as perchloric acid) of an aqueous solution containing 61% perchloric acid were added to a container equipped with a stirrer and a cooling tube.
The hydrous acetone produced under reduced pressure in a warm bath is distilled off at a rate of 1.2 Fl per hour, while the dehydrated acetone (water content 35
The mixture was maintained at 15° C. for 9 hours while adding ppm). After the reaction was completed, 4 ml of a 30% aqueous sodium hydroxide solution was added to neutralize perchloric acid, and acetone was distilled off to obtain an aqueous solution, which was then extracted with benzene to obtain a benzene solution of diacetone/sorbose. This was evaporated to dryness to obtain 31.0 g (yield: 907%) of diacetone sorbose.

Example 4 Iodine instead of perchloric acid! , 2g was used and the water content of dehydrated acetone was 50 ppm.
28.1 g (yield 887%) was obtained.

Comparative Example 3 200 rni of commercially available acetone (moisture content 15 Q Opp
IO, Og of L-sorbose and 127 mg of iodine were added to m), and stirring was continued for 6 hours in a warm solution at 60°C. During this time, there is a molecular sieve between the reactor and the cooling tube.
Incorporating 30g of 3A (manufactured by Wako Pure Chemical Industries) (diameter 2CII)
1 column, packing length 13 cm), and the refluxing solvent was dried.

After the reaction is complete, add 0.5 d of 30% caustic soda aqueous solution,
After distilling off the acetone to obtain an aqueous solution, this was extracted with benzene to obtain a benzene solution of diacetone/sorbose. This was evaporated to dryness and 12.10 g of diacetone sorbose (
A yield of 83.8%) was obtained.

Further, in this experiment, the water content in the acetone refluxed to the reactor was as shown in Table 2.

Table 2 Example 5 Zeolite (Zeolum 3ASG, Toyo Soda) 740 kg
Dehydration adsorption tower (1000+l+mφx1700III
11) and treated by blowing nitrogen gas heated to 230°C in advance with 50ONi' for 4.5 hours.

Acetone (water content 200-300
0ppm) to 1500Q/hour (SV=1.5゜L V
= 2 m/hour) and dehydrated acetone (water content 5
0 ppm or less) was obtained.

50kg of L-sorbose in the above dehydrated acetone 700Q
and 0.6 kg of iodine were added, and the reaction was carried out at 46°C for 9 hours. As shown in Figure 1, this reaction uses an apparatus that is connected to a reactor, a plate-type evaporator, and a compressor to form a vapor recompression type evaporation equipment. External steam of 1.9 kg/cw"G was supplied to heat the plate. As a result, after about 60 minutes, the internal temperature of the plate reached about 55.5°C, and normal operation was achieved. After this, about 500 kg/11r of hydrated acetone (moisture 2
00 to 3000 ppm) was distilled off, and the reaction was continued while dry acetone obtained in advance as described above was kept at 16°C and supplied in an amount equal to the amount of acetone distilled off. .

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

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 manufacturing method of the present invention uses diacetone.
When producing sorbose, the water content is approximately 100 ppm.
The method is characterized by using the following acetone, and compared to conventional methods, the amount of ketalization catalyst or acetone used can be reduced, and the yield of the target product can also be increased.

For example, in the case of a catalyst such as concentrated sulfuric acid, which has traditionally been used as a dehydrating agent, the amount used is about 1/10 of the conventional method.
The water produced can be easily removed by distillation. Therefore, very little alkali is required for neutralization after the reaction, and a small amount of salt is produced, making it easy to recover and purify the target product. In addition, since the generated water can be easily distilled off together with acetone, for example, when perchloric acid is used as a catalyst, the total amount of acetone used can be smaller than in conventional methods, and there is no need for a special removal method by azeotropic distillation. This point is also advantageous. Furthermore, when using other ketal catalysts, the yield of diacetone sorbose can be further improved compared to the conventional method.

[Brief explanation of the drawing]

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 inlet, (
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, ( 9) is a vacuum pump and (
St) indicates a water vapor supply port.

Claims (1)

[Claims] When producing diacetone sorbose by reacting L-sorbose and acetone in the presence of a ketalization catalyst, acetone with a water content of about 100 ppm or less is added to the reaction system, and the water produced is distilled off together with the acetone. A method for producing diacetone sorbose, which is characterized by reacting the diacetone and sorbose.