JPH1052293A - Production of l-aspartic acid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an industrially advantageous L-aspartic acid producing process using butane, oxygen and ammonia as raw materials and not requiring purification process of intermediate raw material. SOLUTION: L-aspartic acid is obtained by the following steps, using butane, oxygen and ammonia as raw materials. A step 1 for obtaining maleic anhydride by carrying out vapor phase oxidation of butane in the presence of oxygen, a step 2 for obtaining maleic acid aqueous solution by absorbing maleic anhydride obtained by the step 1 into water, a step 3 for obtaining fumaric acid by isomerizing maleic acid obtained by the step 2, a step 4 for producing ammonium L-aspartate by subjecting fumaric acid obtained by the step 3 and ammonium fumarate from a step 6 and ammonia to enzymatic reaction in the presence of aspartase or a microorganism producing the aspartase in water solvent, a step 5 for obtaining L-aspartic acid crystals by adding fumaric acid obtained in the step 3 to a solution obtained in the steps 5 and 4, a step 6 for recovering L aspartic acid crystal obtained in the steps 6 and 5 and then recycling a mother solution containing ammonium fumarate to the step 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing L-aspartic acid. More specifically, using butane, oxygen and ammonia as raw materials, L
An industrially advantageous process for producing aspartic acid. The demand for L-aspartic acid is increasing as a pharmaceutical and food additive.

[0002]

2. Description of the Related Art Heretofore, as a method for producing L-aspartic acid, fumaric acid and ammonia have been used as raw materials, and aspartase or a microorganism producing the same has been used as the starting material to produce L-aspartic acid ammonium. A method of obtaining L-aspartic acid by adding an acid is known. However, the conventional method uses L
-The acid precipitation of ammonium aspartate with sulfuric acid or hydrochloric acid produces a large amount of inorganic acid ammonium salt of low economic value as a by-product, thereby increasing the production cost of L-aspartic acid.

As a method for improving the above disadvantage, a method has been proposed in which ammonium L-aspartate after enzymatic treatment is subjected to acid precipitation with fumaric acid (JP-A-8-3349).
2, JP-A-8-33493 and JP-A-6-234713). However, even in the above method, expensive and purified fumaric acid is used. Therefore, considering the implementation on an industrial scale, it was not satisfactory from the viewpoint of economic efficiency.

[0004]

SUMMARY OF THE INVENTION The present invention provides an industrially advantageous process for producing L-aspartic acid using butane, oxygen and ammonia as raw materials and which does not require a purification step for intermediate raw materials.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies in view of the above circumstances, and have found that a process for producing maleic anhydride from butane and oxygen, a process for isomerizing maleic acid to produce fumaric acid, and a process for producing fumaric acid. When the process for producing L-aspartic acid was combined by a specific method, surprisingly, fumaric acid contained various impurities, but the yield in the enzymatic reaction and the recovery in the crystallization, and the obtained The present inventors have confirmed the new fact that L-aspartic acid has almost no effect on the product purity and eliminates the need for a purification step between each process, thereby completing the present invention.

That is, the gist of the present invention resides in a method for producing L-aspartic acid, wherein L-aspartic acid is obtained from butane, oxygen and ammonia as raw materials by the following steps. Step: a step of obtaining maleic anhydride by vapor-phase oxidation of butane in the presence of oxygen to obtain maleic anhydride. Step: A step of absorbing the maleic anhydride obtained in the step with water to obtain a maleic acid aqueous solution. Isomerizing maleic acid to fumaric acid, step: Enzymatic reaction of fumaric acid obtained in the step and ammonium fumarate and ammonia from the following step in an aqueous medium in the presence of aspartase or a microorganism producing the same. And forming L-aspartic acid crystals by adding the fumaric acid obtained in the step to the solution obtained in the step to obtain L-aspartic acid crystals. Recovering the crystals and recycling the mother liquor containing ammonium fumarate to the above steps.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. (Step) The catalytic gas phase oxidation reaction for the maleic anhydride production process in this step can be carried out by employing known reaction conditions generally used in this field. The butane as the raw material may be composed of only n-butane, but may be isobutane, butynes, propanes,
It may contain a small amount of pentanes and the like. The composition of the source gas is usually a mixed gas consisting of 1 to 4% by volume of butane, 10 to 20% by volume of molecular oxygen, and 76 to 89% by volume of a diluent gas. The reaction conditions are usually 300
It is carried out at a temperature of 500 ° C. and a pressure of normal pressure ３3 kg / cm ² , and the space velocity is 300-5000 / at normal pressure.
Hr.

[0008] The catalyst used in the present invention includes phosphorus-
Vanadium-based catalysts can be suitably used. The phosphorus-vanadium-based catalyst contains phosphorus and vanadium, and has an element ratio (P / V) of 0.8 to 1.5, for example.
Those containing a phosphorus-vanadium-based crystalline composite oxide, which is preferably 1 to 1.4, as an active ingredient are preferred. The above-mentioned crystalline composite oxide can be produced by a known production method, for example, a method of reducing vanadium pentoxide with a reducing agent such as hydrazine in the presence of phosphoric acid, followed by a hydrothermal treatment, and a firing treatment of the produced precursor (particularly, No. 58-15313), a method in which vanadium pentoxide is reduced in a substantially anhydrous organic solvent, then heat-treated in the presence of phosphoric acid, and the resulting precursor is calcined (Japanese Patent Publication No. 57-8761). No. 1-50455
Publication) and the like.

Further, the above-mentioned phosphorus-vanadium catalyst is
As the binding component, the element ratio between phosphorus and vanadium (P /
V) may contain an amorphous phosphorus-vanadium composite oxide of 0.8 to 1.5, preferably 1 to 1.4. Such an amorphous phosphorus-vanadium composite oxide is formed from vanadium pentoxide, oxalic acid and phosphoric acid according to a known method. Further, the phosphorus-vanadium-based catalyst may contain inorganic fine particles such as silica as a carrier. The weight ratio (A / B) of the active component (A) to the binding component (B) is usually 1/2 to 1 / 0.03, preferably 1/1 to 1/0. 05, the weight ratio (A / C) of the active ingredient (A) to the carrier (C) is usually 1/2 to 1 / 0.0.
1, preferably selected so as to be in the range of 1/1 to 1 / 0.03. The reaction system may be any of a fixed bed system, a fluidized bed system, and a circulating fluidized bed system, but the fluidized bed system and the circulating fluidized bed system are more preferable because of easy removal of reaction heat.

(Step) In the above step, maleic anhydride is produced from butane and oxygen as raw materials.
The generated maleic anhydride is absorbed by water to obtain a maleic acid aqueous solution. As the absorption method, it is general to absorb the gas in the above step as it is with water, but after cooling the gas in the step to the dew point of maleic anhydride and partially collecting the liquid maleic anhydride, The remaining gas may be absorbed by the water.

The absorption temperature is usually from 40 to 95 ° C., preferably from 50 to 95 ° C., and the pressure is from normal pressure to 4 kg / c.
m ² , preferably normal pressure to 3 kg / cm ² . Also,
The maleic acid recovery concentration at this time is not particularly limited, but is preferably 5% by weight or more, and more preferably 10% by weight or more. Usually, the absorption operation is preferably carried out in an absorption tower composed of a gas-liquid contact tower. In this case, it is possible to increase the concentration of maleic acid by cooling and recycling the absorption liquid to the absorption tower.

The aqueous maleic acid solution thus recovered contains trace amounts of by-products such as acrylic acid and acetic acid generated in the above step. The water used for this absorption is not particularly limited, but it is industrially desirable to reuse the mother liquor obtained after fumaric acid isomerization described below because water in the system can be effectively used.

(Step) The maleic acid recovered in the above step is isomerized to fumaric acid. As the method of isomerization,
There are two methods, a thermal isomerization method and a chemical isomerization method in which an appropriate catalyst is used, and the chemical isomerization method is more preferable in consideration of the amount of by-products generated. As the catalyst used for the chemical isomerization, a known catalyst can be used. For example, thioureas (JP-A-48-30617), a bromine-supplying compound (eg, ammonium bromide) and an oxidizing agent (eg, ammonium persulfate) (JP-B-41-425), bromates or bromates And persulfate (US Pat. No. 2,291,455) can be used. In this case, the amount of the catalyst is usually from 0.001% by weight to 1% by weight of maleic acid present in the aqueous solution.
0% by weight, preferably 0.01% to 5% by weight. If the amount is less than this amount, the yield is low and a large amount of maleic acid remains in the aqueous solution, which is not preferable. If the amount is more than this amount, the amount of fumaric acid produced is undesirably increased.

As a method for adding the catalyst, a powder or a liquid may be added as it is to the reaction system, but it is preferable in terms of operation to dissolve it in an appropriate solvent in which the catalyst is soluble. The reaction temperature is 50-200 ° C, preferably 70-18.
0 ° C. If the reaction temperature is low, a large amount of maleic acid remains, which is economically unfavorable.

The concentration of the aqueous maleic acid solution during the reaction is usually 5 to 60% by weight, preferably 20 to 50% by weight. If the concentration is lower than the above, it is not economical and not practical,
If the concentration is higher than the above, a large amount of fumaric acid solidifies with the progress of the reaction, and the system cannot be stirred, which is not preferable.
The processing time of the step is usually about 0.5 to 5 hours.

In this step, since the solubility of fumaric acid is low, fumaric acid crystals are precipitated in a reaction crystallization form. The reaction crystallization is usually carried out using a stirring tank type crystallization tank. The catalyst may be added either in the crystallization tank or in a transfer pipe leading from step to step. In addition, the reaction crystallization is preferably a continuous type in which the aqueous solution of maleic acid obtained in the above step and the catalyst are continuously supplied, and the produced slurry is continuously extracted, but partially performed by intermittent operation. You may.

(Recovery of fumaric acid crystals from step) If necessary, a step of solid-liquid separation of the slurry obtained in the step is carried out. The temperature at this time is, for example, 0 to 80 ° C, preferably 10 to 50 ° C. It is. If the temperature is too low, the viscosity of the slurry becomes high and handling becomes difficult. If the temperature is too high, the solubility of fumaric acid increases and the recovery rate decreases. Further, a rinsing operation may be performed as necessary. The amount of rinsing water used is usually 5
It is not more than 3 times by weight, preferably not more than 3 times by weight. If the amount of rinse is too small, the rinsing effect is not sufficient, and if it is too large, the recovery of fumaric acid decreases. The temperature of the rinsing water is not particularly limited.

The separation operation is not limited, but
It can be performed by a conventional method such as Nutsche or centrifugation. The fumaric acid crystals obtained in this step usually have 3 to
It contains 20% water, maleic acid, malic acid, acetic acid, acrylic acid, isomerization catalyst and the like.

(Mother liquor recycling after solid-liquid separation) The mother liquor obtained by the solid-liquid separation of the slurry obtained in the step contains maleic acid and fumaric acid for the solubility. Therefore, it is preferable to recycle this mother liquor to the above step and / or step. When recycling mother liquor,
If necessary, water is removed by a concentration step, and the step and / or
Or it can be supplied to the process.

(Removal of solution of mother liquor after solid-liquid separation out of the system) When recycling the mother liquor after the recovery of fumaric acid crystals, bleeding is performed as necessary in consideration of accumulation of impurities and reaction by-products. It is desirable to perform The amount of bleed is usually from 1 to 80% by weight, preferably from 5 to 20% by weight, based on the volume of the mother liquor. If the bleed rate is low, the effect is small and meaningless, and if the bleed rate is high, the cost of wastewater treatment is high, which gives an economically disadvantageous process. The bleeding method may be continuous or intermittent as long as the bleed rate is satisfied.

The recovered fumaric acid is supplied to the following step and the following step. The method of supplying to these steps is such that the fumaric acid obtained in the above step is kept in a slurry state or by solid-liquid separation. The fumaric acid crystal obtained by this may be supplied. At this time, the supplied fumaric acid contains various by-products, and the total amount of these by-products and the total amount of fumaric acid added to the process are 0.001 to 1%.
It is desirable to maintain 0% by weight, preferably 0.001 to 5% by weight, more preferably 0.001 to 2% by weight.

(Step) In this step, the fumaric acid obtained in the above step and the ammonium fumarate from the following step are used as raw materials, and ammonium L-aspartate is produced by an enzymatic reaction in the presence of ammonia. In this step, fumaric acid is present as ammonium fumarate because of the presence of ammonia.

Aspartase for converting ammonium fumarate to ammonium L-aspartate or a microorganism producing aspartase used in the present invention may be a known one. The microorganism that produces aspartase is not particularly limited as long as it is a microorganism having the ability to produce L-aspartic acid from fumaric acid and ammonia. And the like. Specifically, Brevibacterium flavum (B
revibacterium flavum) MJ-2
33 (FERMBP-1497) and MJ-233-A
B-41 (FERM BP-1498), Brevibacterium ammoniagenes ATCC 6872, Escherichia coli
ATCC 11303 and ATCC 27325 can be exemplified.

The concentration of the raw material aqueous solution in the reaction of the process is as follows:
Usually, it varies depending on the concentration of the aqueous solution of ammonium fumarate recovered from the process described below, and usually 45 to 700 g / l, preferably 90 to 700 g as ammonium fumarate.
450 g / l. The reaction in the step can also be partially carried out under pH adjustment with an alkaline agent other than ammonia. The pH in the reaction system at this time is usually 7.5 to 7.5.
10 is preferred.

As the alkaline agent, sodium hydroxide,
Although not limited, such as potassium hydroxide, it is preferable in the present invention to use ammonia which is a raw material for the reaction for producing L-aspartic acid. When using ammonia alone as a raw material, the amount of ammonia to be used is 1.05 to 2.0, preferably 1.1 to 1.6 mol times, based on ammonium fumarate. When the alkaline agent is used in combination with ammonia, the amounts of the ammonia and the alkaline agent are adjusted so as to be within the pH range of the reaction system.

The temperature of the reaction is selected so that the enzyme reaction is carried out efficiently, and is usually 10 to 80 ° C, preferably 15 to 60 ° C. The reaction method of the enzymatic reaction in the step is usually a method in which a raw material aqueous solution is passed through a packed layer in which the cells are immobilized, or a method in which the raw material aqueous solution is suspended in a reactor in which the cells themselves or the immobilized cells are suspended. , While extracting the reaction solution, separating the cells using a separation membrane or a centrifuge, and returning the cells to the reactor.

The reaction solution obtained in this step may contain unreacted ammonium fumarate. In this case, it is desirable to control the content to 2 g / l or less, preferably 1 g / l or less. . (Monoammonium L-aspartate) If necessary, the reaction solution obtained from the step is subjected to a treatment for converting substantially all of the ammonium L-aspartate present in the reaction solution into a monoammonium salt. Is preferred. That is, 90 mol% or more, preferably 92 mol%, of the whole ammonium L-aspartate salt.
As described above, it is preferable that 95 mol% or more be monoammonium L-aspartate. in short,
Starting from excess free ammonia in the reaction solution, diammonium L-aspartate is present, but by changing this to a monoammonium salt, the amount of fumaric acid added in the following step can be reduced, Since the steps after crystallization can be reduced, a more efficient and balanced industrial process can be realized.

The treatment of monoammonium salt of L-aspartic acid is usually carried out by adding a deammonification step for distilling or stripping the reaction solution. The operating conditions may be under normal pressure or under reduced pressure.
It is carried out at a temperature in the range of 100 ° C, preferably 40 to 80 ° C. In order to perform the ammonia removing operation at a low temperature, the degree of pressure reduction must be increased, and the operational restrictions are increased.

On the other hand, a high temperature is not preferred because it causes thermal deterioration of the liquid composition. As the type of the ammonia distillation column, a usual tray column or packed column can be used. The aqueous L-aspartic acid aqueous solution obtained by the enzymatic reaction in the step is subjected to an ammonia removing operation by the above-described method, so that the distillation tank has a molar ratio of ammonia to L-aspartic acid of about 1.0, that is, L-aspartic acid. A residual liquid containing monoammonium aspartate can be obtained.

Only ammonia and water are separated as steam in the ammonia removal operation. If this steam is recovered as a liquid using a cooling pipe or the like, ammonia water can be obtained. The concentration of the obtained ammonia water is affected by the temperature, pressure, steam recovery temperature and the like of the ammonia removing operation. The residual aqueous solution after the above operation is sent to the step to recover L-aspartic acid crystals, and the concentration of ammonium L-aspartate in the aqueous solution to be supplied to the crystallization step is usually 5%.
It is 0 to 800 g / l, preferably 100 to 500 g / l. If this concentration is too low, the crystal recovery will be low,
Conversely, if the concentration is too high, the concentration of the recovered slurry becomes too high, which is not preferable in operation.

When performing the deammonification step,
The removed ammonia water can be recovered and reused according to the following method. The ammonia water separated as vapor by the above-described ammonia removal and collected by a cooling pipe or the like can be reused in addition to the mother liquor from the above or the step. The supply temperature in this case is usually 5 to 80 ° C, preferably 10 to 50 ° C in consideration of the reaction temperature. If the temperature is too high, the vapor pressure of ammonia increases, which is not preferable.

The ammonia obtained in the deammonification step may be absorbed in the mother liquor of the solid-liquid separation liquid in the step and / or the fumaric acid obtained in the step. The operating temperature at this time is usually 0 in consideration of the top temperature in the deammonification step.
-80 ° C, preferably 10-80 ° C. At a high temperature, the vapor pressure of ammonia is undesirably increased, and at a low temperature of 0 ° C. or less, the liquid may condense, which is not desirable. The operating pressure may be normal pressure or reduced pressure, but it is desirable to perform the operation at reduced pressure in order to keep the temperature of the mother liquor low at the bottom of the absorption tower. Examples of the ammonia absorbing device include a packed tower, a wet wall tower, and a spray tower.

As the operation method, either a batch method or a continuous method may be used, but a continuous method is industrially desirable. The ammonia-absorbed liquid may be recycled to the process after adjusting the pH by adding ammonia as needed. In addition, as a method of converting mono-ammonium L-aspartic acid, a part of the L-aspartic acid crystals obtained in the following step may be mixed in the reaction solution to convert di-ammonium L-aspartate into a monoammonium salt. .

For example, 1 to 80% by weight, preferably 10 to 70% by weight of the L-aspartic acid product obtained in the process
Weight% with the reaction solution obtained in the process, and p
It can be realized that H is adjusted to 5.5 to 7.5, preferably 6.0 to 7.0. For the above-mentioned monoammonium salification of L-aspartic acid, it is also possible to combine two processes of the deammonification step and the mixing treatment of L-aspartic acid crystals. In this case, either step may be performed first, but it is preferable to perform the deammonification step first.

(Step) From the solution containing the above-mentioned aqueous solution of ammonium L-aspartate, crystals of L-aspartic acid are crystallized by adding fumaric acid obtained in the step. The concentration of ammonium L-aspartate in the solution supplied to the crystallization step is usually from 80 to 800.
g / l, preferably 100 to 500 g / l. The amount of fumaric acid added in the step is such that the molar ratio of fumaric acid / ammonium L-aspartate is 0.1 to 0.85, preferably 0.1 to 0.8, more preferably 0.2 to 0.8.
8, particularly preferably 0.4 to 0.8. If this molar ratio is too small, the recovery of L-aspartic acid in the crystallization recovery is not sufficient, the aspartic acid concentration in the recycling system becomes high, and if it is too large, the number of moles of fumaric acid added becomes When the number of moles of L-aspartic acid recovered by crystallization exceeds the number of moles and the mother liquor obtained by crystallization and recovery is isomerized and recycled, L-aspartic acid corresponding to the difference in the number of moles is concentrated and recycled. The process cannot be maintained stably. In the crystallization of the present invention, good crystallization can be achieved by adding a relatively small amount of fumaric acid due to the acidity of fumaric acid.

Further, the fumaric acid is supplied in divided steps. In this case, the addition amount in the process is desirably 40% or more of the total addition amount, preferably 50% to 90%. If the amount added in this step is too small, the recovery rate of L-aspartic acid in the crystallization recovery is insufficient and the crystallization efficiency is low, and the L-aspartic acid is concentrated, stabilizing the recycling process. Cannot be maintained.
In this crystallization, the pH of the mother liquor is usually from 3 to
It becomes 6.

The crystallization temperature is usually from 0 to 90 ° C., preferably from 20 to 80 ° C. If the temperature is too low, the resulting crystals will be too fine, making the solid-liquid separation operation cumbersome,
Since the ammonium fumarate precipitates, the purity of the obtained L-aspartic acid decreases. That is, the mother liquor retention amount (water content) of the wet cake obtained by solid-liquid separation is large and a sufficient rinsing effect cannot be obtained, so that the crystal purity decreases or the rinsing amount is increased to increase the amount of L-aspartic acid. It is a situation of reducing the recovery. On the other hand, if the temperature is too high, not only the recovery rate of L-aspartic acid is low, but also thermal degradation of fumaric acid may occur, which is not preferable.

The processing time of the crystallization step is usually 0.5
About 5 hours. The crystallization is usually carried out using a stirring tank type crystallization tank. The fumaric acid may be added either in a crystallization tank or in a transfer pipe leading from step to step. In addition, the crystallization is preferably performed continuously while continuously supplying the solution containing the L-ammonium L-aspartate and fumaric acid, and continuously extracting the produced slurry. Is also good.

(Step) L-aspartic acid crystals are precipitated by the above crystallization. The slurry obtained here is subjected to solid-liquid separation, and if necessary, the recovered crystals are rinsed with water to obtain L-aspartic acid. Collect the acid crystals. The obtained crystals can be dried by a conventional method and recovered as a product having a purity of 99% or more. On the other hand, in the mother liquor obtained by the solid-liquid separation, the added fumaric acid is dissolved as ammonium fumarate, and ammonium L-aspartate corresponding to the solubility is also dissolved. Therefore, this mother liquor is recycled to the above process and used as a part of a raw material for producing L-ammonium L-aspartate by subjecting it to an enzymatic reaction.

The solid-liquid separation of the slurry is not particularly limited, but is carried out in a temperature range of 0 to 80 ° C., preferably 10 to 80 ° C.
Perform at 50 ° C. At low temperatures, the viscosity of the slurry is high and handling becomes difficult. At high temperatures, the solubility of L-aspartic acid increases, and the recovery rate decreases. The amount of water used for the rinsing operation performed as necessary is not particularly limited, but is performed at 5 times or less, preferably 3 times or less with respect to the wet cake. If the amount of rinsing is too small, the rinsing effect is not sufficient, and if it is too large, the recovery of L-aspartic acid decreases. The temperature of the rinsing water is not particularly limited.

The separation operation is not limited, but
It can be performed by a conventional method such as Nutsche or centrifugation. The mother liquor obtained by solid-liquid separation is an acidic aqueous solution having a pH of about 3 to 6. When recycling mother liquor,
If necessary, water is removed by a concentration step and / or ammonia is added to adjust the pH to the optimal pH of the step,
Preferably, the pH can be adjusted to 7.5 to 10, and fumaric acid which is insufficient for the reaction as a whole balance can be added and supplied. The addition of the insufficient fumaric acid is performed in the process, but this addition operation may be performed during the recycling of the mother liquor.

In the method for producing L-aspartic acid according to the present invention, since the accumulation of impurities and reaction by-products occurs due to the inclusion of the recycling step, the long-term continuous operation requires the in-system solution Is desirably bleeded out of the system. The bleeding position is not particularly limited, but a supply solution to the process or a subsequent process is suitable, and particularly, to a process in which L-aspartic acid can be easily recovered as crystals from the bleed solution. Is preferably bleed.

The amount of bleed is usually 2 to 30%, preferably 5 to 20%, based on the volume of the solution. If the bleed rate is low, the effect is small, and if the bleed rate is too high, the treatment of the bleed liquid is difficult, which is economically disadvantageous. The bleeding method may be continuous or intermittent as long as the bleed rate is satisfied.

(Recovery of L-aspartic acid from bleed solution) Since the bleed solution also contains ammonium L-aspartate in an amount corresponding to the solubility, it is usually crystallized to obtain L-aspartic acid.
It is preferred to recover the aspartic acid crystals; Usually, it is preferable to carry out the method by adding an inorganic acid such as sulfuric acid or hydrochloric acid. The amount of the inorganic acid added is at least equivalent to the amount of ammonium aspartate. That is, L-
It is desirable to add an inorganic acid to the bleed solution so that the isoelectric point of aspartic acid becomes 2.8 to improve the recovery.

The crystallization method and conditions for the above-mentioned recovery can be carried out in the same manner as in the above-mentioned crystallization of the main line. For example, the crystallization temperature is 10 to 100 ° C, preferably 20 to 80 ° C.
The slurry obtained by crystallizing the bleed solution is also subjected to solid-liquid separation in the same manner as in the main line, and then the obtained crystals are rinsed with water and then dried to obtain a product. Therefore, the crystals after solid-liquid separation may be mixed with the crystals in the main line after rinsing and dried together.

By the above-mentioned treatment of the bleed solution, the ammonium L-aspartate contained in the bleed solution can be recovered without loss, and the impurities accumulated in the system are purged by the bleed to give a favorable result. . The present invention provides a well-balanced, stable and continuous process by connecting the main line of the steps 1 to 3 and, if necessary, the monoammonium chloride of ammonium L-aspartate in the reaction solution, and further, the respective steps of the bleed solution treatment step. An operable industrially advantageous process can be provided, which enables the production of high-purity L-aspartic acid. In the present invention, the above-described steps and the like are sequentially performed, but each of these steps may be a batch method or a continuous method. Of course, when all the steps are performed by a continuous method, a balanced and stable process is obtained.

[0047]

EXAMPLES The present invention will be described more specifically with reference to examples, but the present invention is not limited to the description of the examples unless it exceeds the gist. In addition, L-aspartic acid (hereinafter abbreviated as ASP), fumaric acid (hereinafter abbreviated as FA), maleic acid (hereinafter abbreviated as MA), malic acid (hereinafter abbreviated as ML), acetic acid ( In the following, analysis of CA (hereinafter abbreviated as AA) and acrylic acid (hereinafter abbreviated as AA) is performed by high performance liquid chromatography, and analysis of ammonia (hereinafter abbreviated as NH ₃ ) content is performed by ion chromatography, and maleic anhydride (hereinafter abbreviated as NH3) is analyzed. Hereinafter, abbreviated as MAH) was determined by gas chromatography.

Example 1 (Step: catalytic gas phase oxidation reaction) 10 kg of a catalyst prepared by a known method was placed in a fluidized bed reaction vessel having an inner diameter of 82 mmφ and a height of 5 m, a pressure of 1.5 kg / cm ² and a reaction temperature of 4
The reaction was carried out at 40 ° C., a space velocity of 900 / Hr, and a butane concentration of 2.0%.
Was obtained with a yield of 55.0%.

(Step: absorption of water) The MAH produced in the above step was absorbed as MA with water at a temperature of 85 ° C. The absorbent was circulated and recycled about four times the amount withdrawn.
The composition of the aqueous solution obtained at this time was MA 54.0% by weight, FA 0.80% by weight, ML 0.70% by weight, CA
0.38% by weight and 0.24% by weight of AA.

(Step: Isomerization reaction) 383.5 g of water was added to 722.0 g of the absorbing solution obtained in the above step,
A 0 wt% MA aqueous solution was obtained. The temperature of the aqueous solution was raised to 80 ° C., and 12.27 g of a 10% aqueous solution of ammonium bromide and 1
72.2 g of a 0% ammonium persulfate aqueous solution was added over 1 hour. After the completion of the dropwise addition, the temperature of the reaction solution in a slurry state was lowered to 25 ° C., and the produced FA was collected by Nutsze. At this time, the recovered FA was 800.3 g, and the yield from the charged MA was 99.2%. The purity of the recovered FA was 99.7% (MA 0.05% by weight, ML 0.10% by weight, CA 0.05% by weight, AA
0.03% by weight, reaction catalyst 0.08% by weight), and the water content was 10% by weight.

(Step: Enzyme reaction) Brevibacterium flavum MJ-233-AB-41 (FERM B) having aspartase activity obtained by a usual culture method.
P-1498) ultrafiltration membrane (ACV-3 manufactured by Asahi Kasei Corporation)
050), 600 g of concentrated cells (about 50% by weight of wet cells), a raw material solution (600 g of FA obtained in the above step, and 885 ml of 25% NH ₃ water to which water was added to make a total volume of 3 liters, pH 9). 2) at 45 ° C
The reaction was performed for 4 hours. After completion of the reaction, the cells were removed by an ultrafiltration membrane, and the obtained filtrate was analyzed.
30 g / l (99% or more of theoretical yield), FA is 1.0 g
/ ₃ , NH ₃ 36.8 g / l, NH ₃ / ASP molar ratio is 1.26 (ie, A
The ratio of SP diammonium was 26%), and the pH was 9.

(Ammonia removal step) 3 liters of the enzyme reaction solution obtained in the step was charged into a 10-liter eggplant-shaped flask, and was heated at 80 ° C. using a laboratory evaporator.
Under the condition of 350 mmHg, ammonia was separated by distillation.
After 15 minutes, the pressure was returned to normal pressure, and the ammonia removal operation was completed. The residual liquid in the obtained distillation still has an ASP of 275 g / l,
NH ₃ is in the composition of 35.4 g / l, was the capacity of the 2470Ml. Distilled water was added to the remaining liquid, and ASP was 230
g / l and 29.2 g / l of NH ₃ (NH ₃ / AS
The P molar ratio was 1.0, that is, all were ASP monoammonium salts) to make up 8500 ml of the bottom liquid. This was used as a crystallization raw material.

(Step: Crystallization) An enzyme reaction solution (ASP ammonium aqueous solution) obtained in the ammonia removal step was placed in a separable flask with a 10-liter jacket, which had been kept at 60 ° C. by flowing hot water through the jacket in advance. In a 3 liter, 40 wt% FA slurry (slurried by adding water to the FA obtained in the above step).
g (FA 300 g, H ₂ O 450 g) was added. The added fumaric acid was added so that the molar ratio of fumaric acid / L-aspartic acid was 0.5 with respect to ammonium L-aspartate in the enzyme reaction solution. The crystallized liquid is 25
The temperature was lowered to ° C., and the ASP slurry was recovered.

(Step: Solid-Liquid Separation) The obtained ASP slurry was subjected to solid-liquid separation with Nutsche and further distilled water 1620
g, and dried at about 60 ° C. under reduced pressure.
50 g of a white solid was obtained. The resulting solid has an ASP of 9
9.3% by weight, containing 0.7% by weight of ammonium ammonium. The ASP recovery was 80.0%. On the other hand, the mother liquor obtained by solid-liquid separation had an ASP of 29.5 g /
1, FA was 76 g / l, NH ₃ was 23.5 g / l, pH was about 4.5, and volume was about 4.7 liters. Note that the FA ammonium obtained here is converted to its NH
_{From the three} balances, it was a mixture of a monoammonium salt and a diammonium salt.

(Recycling of mother liquor) A total of 4.7 liters of the mother liquor obtained by the above-mentioned solid-liquid separation was charged into a 10-liter eggplant-shaped flask, and reduced pressure (300 to 400 mmHg) at 80 ° C. using a laboratory evaporator. The water was distilled off under reduced pressure. The steam obtained here was collected by attaching a cooling pipe through which cooling water of 50% by weight of ethylene glycol was circulated at 0 ° C. In addition, the obtained concentrated solution is recycled for use as the next enzyme reaction raw material.Fumaric acid, which is insufficient for the required amount of the reaction, is added. A shortage of fumaric acid is added so that the total number of moles of unrecovered L-aspartic acid and fumaric acid becomes equal. Here, 450 g (180 g FA, 180 g FA) of the insufficient FA (a 40 wt% slurry obtained by adding water to the FA obtained in the above step) was added to the obtained concentrate.
H ₂ O (270 g), 380 ml of 25% aqueous NH ₃ and distilled water were added to make up a solution having a pH of 9.0 and a volume of about 3 liters. The composition of this makeup liquid is
ASP: 44.5 g / l, FA: 200 g / l, NH ₃
Was 65.7 g / l. The same operation as above was repeated three times without changing the conditions. The results are shown in Table 1.

[0056]

[Table 1]

Although the FA obtained in the process contained a small amount of impurities, as shown in the table, there was no change in the ASP yield, the crystallization recovery rate, and the purity of the obtained ASP product.
In other words, the present process is a process in which continuous operation can be performed efficiently and stably as a whole process, and high-purity L-aspartic acid can be obtained even when a recycle operation is performed.

[0058]

Industrial Applicability According to the present invention, an industrially advantageous process for producing L-aspartic acid using butane, oxygen and ammonia as raw materials and requiring no purification step for intermediate raw materials can be obtained.

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] October 14, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Brief description of drawings

[Correction method] Added

[Correction contents]

[Brief description of the drawings]

FIG. 1 is a block flow diagram showing an example of an embodiment of the present invention.

[Description of Signs]: Step: Step: Step: Step: Step: Step: Step

[Procedure amendment 2]

[Document name to be amended] Drawing

[Correction target item name] Fig. 1

[Correction method] Change

[Correction contents]

FIG.

Claims (7)

[Claims] 1. A method for producing L-aspartic acid, wherein L-aspartic acid is obtained from butane, oxygen and ammonia as raw materials by the following steps. Step: a step of obtaining maleic anhydride by vapor-phase oxidation of butane in the presence of oxygen to obtain maleic anhydride. Step: A step of absorbing the maleic anhydride obtained in the step with water to obtain a maleic acid aqueous solution. Isomerizing maleic acid to fumaric acid, step: Enzymatic reaction of fumaric acid obtained in the step and ammonium fumarate and ammonia from the following step in an aqueous medium in the presence of aspartase or a microorganism producing the same. And forming L-aspartic acid crystals by adding the fumaric acid obtained in the step to the solution obtained in the step to obtain L-aspartic acid crystals. Recovering the crystals and recycling the mother liquor containing ammonium fumarate to the above steps. 2. The method according to claim 1, wherein the fumaric acid produced in the step is once separated as a solid from the reaction solution and then supplied to the step. 3. The process according to claim 1, wherein the mother liquor obtained after separating the fumaric acid in the step is recycled to said and / or step. 4. The method according to claim 1, further comprising a deammonification step of converting substantially all of the ammonium L-aspartate obtained in the step into monoammonium L-aspartate. Method. 5. The process wherein the temperature of the aqueous solution is 50 to 200.
The method according to any one of claims 1 to 5, wherein the method is carried out at a temperature of 0 ° C. 6. The amount of fumaric acid added in the step is 4 parts by weight of aspartic acid contained in the aqueous solution obtained in the step.
The method according to any one of claims 1 to 6, wherein the amount is 0 mol% or more and less than 100 mol%. 7. The pH of the mother liquor in the above step is 3-6.
The method according to any one of claims 1 to 7, wherein