JPH0920736A - Biodegradable chelating agent using acrolein as a raw material, method for producing L, L-propanediaminedisuccinic acid and its alkali metal salt - Google Patents

Abstract

(57) [Summary] (Revised) [Purpose] L, L-propanediaminedisuccinic acid, which has excellent biodegradability, is made from easily available acrolein and L-aspartic acid as raw materials. Provide high yield and high purity. [Structure] After adding L-aspartic acid to acrolein under alkaline conditions and further condensing one molecule of L-aspartic acid, a Schiff base produced by contact hydrogenation in the presence of a catalyst is reduced by L, L. A method for producing an alkali metal salt of propanediaminedisuccinic acid (PDDS). Further, a method for producing L, L-PDDSs, wherein the produced Schiff base is reduced by catalytic hydrogenation in the presence of a catalyst, and then crystallized by acid precipitation with a mineral acid. And L, L-PD for reducing the generated Schiff base with a metal hydride
A method for producing an alkali metal salt of DS.

Description

Detailed Description of the Invention

[0001]

The present invention relates to acrolein and L-
The present invention relates to a method for producing L, L-propanediaminedisuccinic acid and its alkali metal salt from aspartic acid.

[0002] L, L-propanediamine disuccinic acid and its alkali metal salts are widely used as a biodegradable chelating agent in detergent compositions, detergent builders, heavy metal sequestering agents, peroxide stabilizers and the like.

[0003]

2. Description of the Related Art A method for producing L, L-propanediaminedisuccinic acid (hereinafter referred to as L, L-PDDS) is as follows.
Some are known from the past. For example, one molecule of 1,3
-A method for adding two molecules of L-aspartic acid to dichloropropane (Zhurnal Obschei Khimii 1978, 49, 3
No. 663), and as a conventional technique for producing a stereoisomeric mixture of PDDS, a method of adding two molecules of maleic acid to one molecule of 1,3-propanediamine (Zhur
nal Obschei Khimii 1978, Volume 49, Issue 3, page 669). The problems of these conventional techniques will be described below.

The conventional technique using 1,3-dichloropropane is accompanied by by-products in addition to L, L-PDDS.
The target product has not yet been obtained in a practical reaction yield. Further, the reaction yield is greatly influenced by minute fluctuations in the pH of the reaction solution, reaction temperature, dropping rate, etc., and thus it is difficult to obtain a reproducible and easy process. Moreover, since the chlorinated compound is discharged after the reaction, a serious problem remains in the treatment of the waste liquid.

Further, the conventional technique for producing a stereoisomer mixture of PDDS gives the D, D-form and PD, L-form of PDDS in a production ratio higher than the intended L, L-PDDS. A problem remains in the practicality of PDDS as a biodegradable chelating agent. That is, D, D-PDDS is poor in biodegradability, and when a large amount is released into the environment, there is a fear of a serious situation.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve these problems of the prior art, and L, LP
The purpose of the present invention is to provide an industrially advantageous method for producing DDSs and alkali metal salts thereof, and specifically,
L, L, which has extremely excellent biodegradability, using acrolein and L-aspartic acid as raw materials
-Providing PDDSs in a high yield and a high purity in an easy process with good reproducibility.

[0007]

Means for Solving the Problems As a result of intensive research to solve the above-mentioned problems, the present inventors have found that 3-oxopropyl-L-aspartic acid can be easily prepared by a conjugate addition reaction of acrolein with L-aspartic acid. Found to generate. It was also found that the 2-oxopropyl-L-aspartic acid thus obtained further easily undergoes a dehydration condensation reaction with one molecule of L-aspartic acid to form a Schiff base. It was found that when this Schiff base is subjected to catalytic hydrogenation or a reduction reaction with a metal hydride, the desired L, L-PDDS can be obtained in high yield and high purity without racemization. It was also found that 2-methyl-L, L-propanediaminedisuccinic acid (hereinafter referred to as L, L-MePDDS) can be obtained in the same manner even when acrolein is replaced with methacrolein.

That is, the present invention relates to acrolein
-L, L-, characterized in that after adding aspartic acid under alkaline conditions, a Schiff base produced by further condensing one molecule of L-aspartic acid is reduced by catalytic hydrogenation in the presence of a catalyst. The present invention relates to a method for producing an alkali metal salt of propanediaminedisuccinic acid.

Further, the present invention further comprises adding 1-L-aspartic acid to acrolein under alkaline conditions, and further adding 1-
A Schiff base produced by condensing a molecule of L-aspartic acid is reduced by catalytic hydrogenation in the presence of a catalyst, and then acidified and crystallized with a mineral acid.
-Propanediamine disuccinic acid production method.

Further, the present invention relates to acrolein-based L-
L, L-propanediamine disuccinic acids, characterized in that after addition of aspartic acid under alkaline conditions, a Schiff base produced by further condensing one molecule of L-aspartic acid is reduced with a metal hydride. Relates to a method for producing an alkali metal salt.

The case of producing L, L-PDDS and its alkali metal salt using acrolein as a raw material will be described below. However, L, L-MePDDS and its alkali metal can be produced by the same operation using metaacrolein. Salts can be produced.

The method of the present invention comprises a conjugation addition step of conjugating one molecule of acrolein to the amino group of one molecule of L-aspartic acid under alkaline conditions to produce 3-oxopropyl-L-aspartic acid. A Schiff base generation step of dehydrating and condensing one molecule of the amino group of L-aspartic acid to the aldehyde group of 2-oxopropyl-L-aspartic acid which is the reaction product, and the Schiff base which is the reaction product thereof. Schiff base reduction step of hydrogenating a base by catalytic hydrogenation or metal hydride, and adding a mineral acid to the reaction product to obtain the desired L,
It consists of an acid precipitation crystallization step to isolate L-PDDS.

Alternatively, one molecule of acrolein is conjugatedly added to one molecule of the amino group of L-aspartic acid under alkaline conditions to produce 3-oxopropyl-L-aspartic acid, and a reaction product thereof. The compound of 3-oxopropyl-L-aspartic acid, which is an aldehyde group, is dehydrated and condensed with one molecule of the amino group of L-aspartic acid to form a Schiff base, and the reaction product of the Schiff base is contacted. Schiff base reduction step of hydrogenation by hydrogenation or metal hydride, and concentration of the reaction product to obtain the desired L, L-PD
It consists of an evaporation to dryness step to isolate the alkali metal salt of DS.

Acrolein used in the present invention is widely used as a raw material for medicines, fiber treating agents, cross-linking condensing agents, allyl alcohol, glycerin, etc.,
It is extremely easily available as an industrial raw material. Similarly, methacrolein is also easily available as an industrial raw material. As a form used in any case, an aqueous solution having a weight concentration of 20 to 100%, preferably 80 to 90% is generally used.

The aspartic acid used in the present invention is the same in terms of chemical reaction regardless of the D-form, L-form and racemic form, but L, L which is extremely excellent in biodegradability. Only the L-form is preferably selected for the purpose of obtaining PDDS. At that time, L-aspartic acid is industrially available with a purity of 70% or more, preferably 8%.
A solid content of 5% or more can be used, but an alkali metal salt obtained during the production or an aqueous solution of the alkali metal salt can also be directly used.

The amount of L-aspartic acid used in the conjugate addition step of the present invention is as follows:
It is appropriately selected within a range of 1.8 to 2.6 times mol, preferably 1.9 to 2.2 times mol. The amount used is based on the presence of approximately twice the molar amount of L-aspartic acid in advance with respect to acrolein in order to continuously carry out the Schiff base production step of the next step. However, when the step of producing the Schiff base in the next step is carried out stepwise, it is 0.8 to 1.6 times mol, preferably 0.9 to 1.2 times the mol of acrolein.
It is desirable to use double moles of L-aspartic acid.

The pH condition in the conjugate addition step is set to neutral to weakly alkaline by adding an alkali metal hydroxide or an aqueous solution thereof. As an alkali metal,
Li, Na, K, preferably Na is used. Instead of the alkali metal hydroxide, L-aspartic acid alkali metal salt or its aqueous solution may be used directly.

The set pH in the conjugate addition step is 7-1.
3, preferably selected in the range of 8 to 12 as appropriate. pH
When it is 13 or more, the coloring caused by the polymerization decomposition of acrolein is remarkable, and even when the pH is 7 or less, the production of 3-oxopropyl-L-aspartic acid does not proceed smoothly due to the decrease in reactivity, and as a result, acrolein is produced. Leads to polymerization decomposition of. In this way, the set pH in the conjugate addition step is
Although an extremely important factor, the advantage of this method is that the pH value once set remains almost constant during the process due to the strong buffering action of L-aspartic acid, which is present at a high concentration in the reaction solution. Is to be done.

The mixing method in the conjugate addition step is as follows:
The most commonly employed method is to add acrolein to an alkaline aqueous solution of L-aspartic acid at such a rate that it does not accumulate in the reaction solution. A method in which an alkaline aqueous solution of L-aspartic acid is added dropwise to the aqueous acrolein solution is also possible, but it may unnecessarily cause polymerization decomposition of acrolein present in a large excess in the reaction solution during the addition.
In any case, heat is generated during dropping. It is desirable that the temperature of the reaction liquid at the time of dropping is 0 to 60 ° C., preferably 0 to 50 ° C. The rapid temperature rise at the time of dropping causes remarkable coloration of the reaction solution, and the reaction yield of the desired 3-oxopropyl-L-aspartic acid in the conjugate addition step is greatly reduced.

The aging temperature in the conjugate addition step is 0 to 6
It is appropriately selected in the range of 0 ° C, preferably 0 to 50 ° C.
The aging time is appropriately selected within the range of 1 to 24 hours, preferably 1 to 4 hours. In order to prevent the vaporization loss of acrolein, it is necessary to attach a cooling pipe to the reaction apparatus through dropping and aging in the conjugate addition step in order to allow the reaction to proceed efficiently and from the viewpoint of safety.

The Schiff base production step in the present invention is advantageously carried out continuously with the conjugate addition step which is a preceding step. That is, in the conjugate addition step, when acrolein is reacted in the presence of about twice the molar amount of L-aspartic acid, another molecule of L-aspartic acid is dehydrated after the production of 3-oxopropyl-L-aspartic acid. The condensation proceeds to produce the Schiff base. In this continuous process, the conjugate addition proceeds irreversibly, whereas the Schiff base formation is reversible, so even if the Schiff base formation may precede the conjugate addition, 3-oxopropyl-L -The production of the Schiff base of aspartic acid proceeds largely and preferentially.

When the Schiff base production step is carried out continuously with the conjugate addition step, the set pH is preferably in the range of 7 to 13, preferably 8 to 12. The aging temperature is 0 to 60 ° C, preferably 0 to 50 ° C. The aging time is 0
It is appropriately selected within the range of -24 hours, preferably 0-4 hours.

It is also possible to divide the Schiff base generation step into the conjugate addition step in stages. At that time, the amount of aspartic acid to be added stepwise is 0.8 to 1.6 times mol, preferably 0.9 to 1.
It is preferable to use 2 times the molar amount. In that case, the reaction solution may have a sudden p
In order to suppress H fluctuation, 7 to 13, preferably 8 to 12
It is preferable to use as an alkali metal salt in the range of.

When the Schiff base production step is carried out stepwise with respect to the conjugate addition step, the aging time is appropriately selected within the range of 2 to 24 hours, preferably 1 to 4 hours. Thus, the stepwise implementation of the two steps is disadvantageous in that the steps are complicated and the aging time is prolonged, but 3-oxopropyl-L-aspartic acid or its alkali metal salt is isolated depending on the purpose. It is adopted when trying.

The hydrogenation reaction carried out in the Schiff base reduction step of the present invention is achieved by a catalytic hydrogenation reaction using a catalyst or a reduction reaction with a metal hydride.

As the catalyst used in the catalytic hydrogenation reaction in the Schiff base reduction step, heavy metals such as nickel, palladium, rhodium, ruthenium and platinum are used as a heterogeneous catalyst. Of these, nickel has the highest reactivity and availability of raw materials, and is used as Raney Ni. Also, other heavy metals can be used, but from the viewpoint of availability of raw materials, Pd-C, Rh-C, Rh-A
It is desirable to collect and reuse as l ₂ O ₃ , PtO ₂ or the like.

The catalyst used in the catalytic hydrogenation reaction in the Schiff base reduction step is used in an amount of 1 to 30 mol%, preferably 5 to 10 mol% based on the acrolein used in the Schiff base production step.

The catalytic hydrogenation reaction in the Schiff base reduction step is started by directly adding a catalyst to the reaction product after the Schiff base production step and vigorously stirring in a hydrogen atmosphere. The hydrogen pressure is 0 to 100 atm, preferably 20.
It is appropriately selected within the range of 50 atm.

The reaction temperature in the catalytic hydrogenation reaction in the Schiff base reduction step is 20 to 100 ° C., preferably 40 to
It is appropriately selected within the range of 70 ° C. The aging time is 1
It is appropriately selected within the range of -24 hours, preferably 2-5 hours. After the reaction, the catalyst used is promptly separated by gradient filtration after stationary settling or filtration using a filtering agent such as Celite. The filtered off catalyst is preferably recycled after washing and activation.

The obtained filtrate is a colorless or slightly brownish, slightly viscous, transparent liquid, which is directly used in the next step of evaporation to dryness or the acid precipitation crystallization step.

In the evaporation-drying step of the present invention, when the catalytic hydrogenation reaction is carried out in the Schiff base reduction step and the reaction yield is high, the desired L, L-PDD is obtained.
The purpose is to directly obtain the alkali metal salt of S.

The evaporation to dryness process of the present invention is obtained by subjecting the slurry obtained by heating and concentrating the reaction product after the Schiff base reduction process by the catalytic hydrogenation reaction to powder crystallization by the spray drying method. At that time, prior to the heat concentration, an aqueous solution of an alkali metal hydroxide is added to the reaction product after the Schiff base reduction step, and the pH is appropriately adjusted to produce 2 to 4 alkali metal salts of L, L-PDDS. It is possible.

Next, the case of carrying out the reduction reaction with a metal hydride in the Schiff base reduction step of the present invention will be described.

Examples of the metal hydride used in the Schiff base reduction step include NaBH ₃ CN, NaBH ₄ and N.
Although aH ₂ PO ₂ or the like is used, the set pH during the reaction is different. When NaBH ₃ CN is used, the set pH is 5 to 12, preferably 5 to 7. NaBH ₄
When using, the set pH is 9 to 13, preferably 10
~ 12 is good. When NaH ₂ PO ₂ is used,
The set pH is 8 to 13, preferably 10 to 12. Whichever metal hydride is used, the higher the alkalinity side, the higher the reduction potential and the higher the reactivity.However, if the alkaline conditions are too strong, the by-products increase and the coloration increases. It should be avoided that it is carried out out of the set pH range because it will seriously reduce the yield when the target substance is obtained later.

The reaction temperature in the Schiff base reduction step using a metal hydride is 0 to 100 ° C., preferably 20 to
It is appropriately selected within the range of 50 ° C. The aging time is 1
To 36 hours, preferably 4 to 8 hours. The obtained reaction liquid is a yellowish brown or dark brown liquid, which is directly used in the subsequent acid precipitation crystallization step.

The acid precipitation crystallization step in the present invention is achieved by adding a mineral acid to the reaction solution obtained after the Schiff base reduction step. Examples of the mineral acid used include sulfuric acid, hydrochloric acid, nitric acid and the like, and sulfuric acid is particularly preferably used. Sulfuric acid is selected from industrially available ones having a purity of 60 to 98%, and the reaction liquid obtained by the hydrolysis step has a pH of 1.0 to 3.0, preferably 1.5 to 2.5.
The required amount to adjust to is used. The temperature at the time of dropping sulfuric acid is preferably 10 to 100 ° C., preferably 40 to 80 ° C., and the dropping time is 0.5 to 3 hours, preferably 1 to 2 hours.

The desired product, L, L-PDDS, is obtained by aging the reaction product after addition of sulfuric acid at 0 to 50 ° C., preferably 10 to 40 ° C. for 0 to 72 hours, preferably 1 to 5 hours,
The precipitated crystals are obtained by suction filtration or centrifugal filtration.

The crystals of the target substance to be obtained are usually of sufficiently high purity without recrystallization, except that the mother liquor containing a trace amount of sulfate on the crystal surface is washed with a small amount of water.

When the catalytic hydrogenation reaction is used in the Schiff base reduction step, it is particularly advantageous that no by-products other than sodium sulfate produced by the neutralization reaction are generated in the acid precipitation crystallization step, This is an extremely advantageous process when considering waste liquid treatment in industrial production.

[0040]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited to the following examples.

Example 1 An autoclave type reactor equipped with a stirrer, a thermometer, a dropping funnel and a distillation apparatus was charged with water (1,079 kg), 48 wt% NaOH aqueous solution (1,254 kg, 15.1 kmol), and then L-asparagine. The acid (1,000 kg, 7.52 kmol) was continuously dissolved under stirring. 30% by weight of acid-converted L prepared in this way
-To the aqueous disodium aspartate solution, 97 wt% acrolein (210 kg, 3.67 kmol) was added dropwise over 1.5 hours while stirring the reaction solution at 40 ° C and stirring. After the completion of dropping, the reaction solution was stirred at a temperature of 40 to 50 ° C. for another 4.5 hours.
Raney nickel (W6, 50 wt% suspension, 42
kg, 0.37 kmol), and after thoroughly replacing the air in the reaction vessel with hydrogen gas, the apparatus was sealed and the hydrogen pressure was raised to 50 atm, and then the reaction solution temperature was raised from 25 ° C under vigorous stirring. After gradually raising the temperature to 75 ° C over 1 hour, at 50 ° C
Vigorous stirring was continued for 5.5 hours. During this period, hydrogen was replenished to 100 atm every time the hydrogen pressure dropped to 75 atm. After allowing the reaction solution to cool to room temperature and allowing it to stand, the supernatant is put on a suction filtration device, and the residue is also put on a suction filtration device with water (15
It was washed with 0 kg) to obtain a filtrate (3,690 kg). A slurry (2,897 kg) obtained by heating and concentrating this filtrate was powder-dried at 120 ° C. by a spray-dry method to obtain L, L-PD.
Tetrasodium salt of DS (1,593kg, 3.85kmol, crude yield 1
05%) was obtained as light brown powder crystals (melting point: 200 ° C.). As a result of HPLC analysis using a chiral column, the generated L,
The optical purity of L-PDDS was 99% or more. Also,
The components in the crude crystals were L, L-PDDS 98.3 acid% by weight and L-aspartic acid 1.7 acid% by weight.

Example 2 Hydrogenation reaction was carried out with Raney nickel in the same manner as in Example 1 to obtain a filtrate (2,700 kg). 98 wt% sulfuric acid (1,310 kg, 13.1 kmol) was added dropwise to the filtrate over 1.5 hours.
During this time, the temperature of the reaction solution was raised to 80 ° C. The reaction solution again
The mixture was allowed to cool to 33 ° C., and the precipitated L, L-PDDS crystals were filtered by centrifugation. Further, it was washed twice with water (40 kg) at 20 ° C. to obtain wet crystals (1,392 g). L, L- after blast drying
PDDS (988 kg, 3.22 kmol, 88% yield) was a uniform white crystal. As a result of HPLC analysis, the produced L, LP
The chemical purity and optical purity of DDS were both 99% or higher.

Example 3 In the same manner as in Example 2, the conjugate addition reaction and the Schiff base formation reaction were continuously carried out. NaBH ₄ (43 kg,
A suspension prepared by dissolving 1.13 kmol) in water (400 kg) in advance was added to the reaction solution at 10 ° C under stirring for 0.5 hours. Then, raise the temperature of the reaction solution to 45 ° C,
Stirring was continued for another 5.5 hours. 98% by weight of this reaction solution
Sulfuric acid (1,540 kg, 15.4 kmol) was added dropwise over 1.5 hours. During this time, the temperature of the reaction solution was raised to 80 ° C. The reaction solution was cooled to 33 ° C. again, and the precipitated L, L-PDDS crystals were filtered by centrifugation. Further, it was washed twice with water (40 kg) at 20 ° C. to obtain wet crystals (1,341 g). L after blast drying
L-PDDS (999 kg, 3.27 kmol, yield 89%) was a uniform white crystal. As a result of HPLC analysis, the produced L, L
-The chemical and optical purities of PDDS are both 99%.
That was all.

Examples 4 to 6 The same operations as in Examples 1 to 3 were carried out except that 99 wt% methacrolein (259 kg) was used instead of 97 wt% acrolein (210 kg), and L, L-MePDDS and The 4
The sodium salt was obtained. The results are shown in Table 1.

[0045]

[Table 1]

According to the method of the present invention, acrolein and L-aspartic acid, which are industrially very easy to obtain, are used as raw materials, and L, L-PDDS and its alkali metal salt having excellent biodegradability are prepared. It can be obtained in high yield and high purity. The present invention also has the following advantages. (1) Acrolene and methacrolein are extremely easily available general-purpose industrial raw materials and are suitable as raw materials for mass industrial production of L, L-PDDS and L, L-MePDDS. (2) In the process, all of the steps of conjugate addition, Schiff base generation, and Schiff base reduction proceed under mild conditions, so the reaction can be easily controlled. Especially, due to the buffering effect of L-aspartic acid, which is used as a raw material in high concentration,
Since the fluctuation of pH is kept small, complicated pH adjustment is unnecessary. (3) In the Schiff base reduction step, especially when a catalytic hydrogenation reaction is used, the main by-product in the acid precipitation crystallization step is only sodium sulfate, and L, L-PDDS and L, L
-A very advantageous process when considering waste liquid treatment in the mass industrial production of MePDDS.

Claims (4)

[Claims] 1. A Schiff base produced by adding L-aspartic acid to acrolein under alkaline conditions and further condensing one molecule of L-aspartic acid to reduce the Schiff base by catalytic hydrogenation in the presence of a catalyst. Characterized by,
A method for producing an alkali metal salt of L, L-propanediaminedisuccinic acid. 2. A Schiff base produced by adding L-aspartic acid to acrolein under alkaline conditions and further condensing one molecule of L-aspartic acid is reduced by catalytic hydrogenation in the presence of a catalyst, Then, a method for producing L, L-propanediaminedisuccinic acid, which comprises crystallizing by acid precipitation with a mineral acid. 3. A Schiff base produced by adding L-aspartic acid to acrolein under alkaline conditions and further condensing one molecule of L-aspartic acid is reduced with a metal hydride. , A method for producing an alkali metal salt of L, L-propanediaminedisuccinic acid. 4. The production method according to claim 1, 2 or 3, wherein the acrolein is acrolein or methacrolein.