CH668256A5 - METHOD FOR PRODUCING SALTS OF ETHYLENDIAMINE-TETRASSIC ACID-DINATRIUM SALTS. - Google Patents

Description

DESCRIPTION

The invention relates to a process for the preparation of salts of ethylenediamine-tetraacetic acid disodium salt.

Ethylenediamine tetraacetic acid (EDTA) is the most common chelating and complexing agent. It is valuable for controlling the concentration of metal ions in various media as well as for modifying, controlling and controlling reactions mediated by such controlled metal ions. For example, EDTA and its soluble salts are important additives in detergent compositions for the control of undesired calcium ions forming cheesy soap deposits by chelation.

Preferred EDTA metal chelates are also used in large quantities for agricultural applications as well as for pharmaceutical and pharmaceutical purposes.

The disodium zinc EDTA chelate is valuable in the agricultural sector. The disodium calcium EDTA che lat is used as a protective agent or preservative in pharmaceutical compositions and to prevent calcium depletion by diuretics in the human body.

The purified calcium chelate is also administered directly as a medicine for chelating lead in cases of acute and chronic lead poisoning and heavy metal intake. Iron, copper and manganese chelates have also been used in agriculture and in the oxidation and reduction of nitrogen oxides as well as for sweetening and improving the taste of acidic natural gases. EDTA's chelation activity is used to selectively concentrate and isolate valuable heavy metals such as uranium, plutonium and thorium, as well as rare earths.

These EDTA salts have hitherto been prepared according to the processes originally disclosed in US Pat. Nos. 2,407,645, 2,461,519 and 2,855,428. This latter is the basis for the present production of EDTA and takes place via the cyanomethylation in acidic solution in order to delay the polymerization of HCN. This synthesis via the hydrolysis of the nitrile primarily gives EDTA-tetranetrium salt (EDTA-Na4), which is then converted into the free acid EDTA (EDTA-AA). The desired salts have so far been produced from the latter by neutralization. Due to the limited solubility of the

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EDTA-AA, however, the reaction to form the salts was slow and resulted in varying products that required recrystallization and re-cleaning.

Since the desired products are required in large quantities, such cleaning processes are not economical or competitive.

The aim of the invention is a process for the preparation of EDTA salts of the formula

NaOOCH2Cv naooch2c

/

N-CH2-CH2-N

^ ch2coo-

10th

\

3-nm "- *

CH, COO-

(1)

to provide, where n is 1 or 2 and M is Na, K, Li, 15 Rb, Zn, Ca, Fe, Mn or Cu or, if one of the symbols M represents Na, K, Li or Rb, the other M also . H, which is characterized in that 1 mole of the wet cake of the EDTA salt of the formula 20 under vacuum

NaOOCH2C • NaOOCH2C-with

^ ch2cooh n-ch2-ch2-ncT (2)

^ ch2cooh

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(a) 1 or 2 moles of a compound of the formula m + oh-

wherein M + represents Na +, K +, Li + or Rb +, or

(b) 1 mole of a compound of the formula

3-nMn + mX3 "ra_

(3)

30th

(4)

35

where M is Li, Na, K, Rb, Ca, Mn, Fe, Cu or Zn, XO, OH or C03 and m and n are each independently 1 or 2, where, if M is Li, Na, K or Rb represents, X is not OH, mixes in the presence of sufficient water to ensure ionization, which removes the exothermic heat and the water vapor formed and finally collects the product obtained.

In the compounds of formula (4), X is O or CO3 when m is 1 and X is OH when m is 2. 45

The invention is based on mixing commercially available wet cakes of the ethylenediamine-tetraacetic acid re-disodium salt with the oxide, carbonate or hydroxide of the M component in a moist state until the exchange of hydrogen with the M component has ended, and 50 the subsequent extraction of the salt formed.

The commercially valuable salts produced by the process according to the invention and used on a ton scale for agriculture, pharmacy and the detergent and mining industries include Na3-EDTA, 55 Na4-EDTA, Na2Mn-EDTA or Na2Cu-EDTA.

The oxides, hydroxides and carbonates of the M components that can be used for the reaction are, for example, NaOH, Na20, Na2C03, ZnO, ZnC03, Zn (OH) 2, CuC03, CuO, CaO, Ca (OH) 2, CaC03, MnO, MnC03, KOH, K2C03 60 and FeC03. While the sodium, zinc, calcium and manganese salts are currently commercially available in very large quantities, other salts including the lithium, potassium and rubidium salts can be produced by the process according to the invention. 65

Since the reaction is essentially an ionically mediated reaction, it is accelerated by the presence of some water. Since the wet Na2EDTA cake is about 15%

Containing water, this is generally sufficient to initiate the reaction. However, since some of the oxide and hydroxide reactants require water of hydration to form ionic forms, it is desirable in certain circumstances to add more water to the reaction vessel. The need to add water is indicated if the combination of Na2-EDTA with the M components shows an exothermic course, but in the interest of economical production the stoichiometric amount should not be exceeded significantly. The water is added either in a stoichiometric amount or in portions until no further exothermic reaction takes place.

The mixing of the wet Na2-EDTA cake with the MOH or MX component should be done in a vessel that ensures intimate mixing and contact of the solid reactants. Twin drum mixers, conical mixers and similar vessels that either stir or keep moving due to the vessel rotation or the equipment with an internal stirrer are satisfactory. It is convenient to use vessels equipped with heat sources to raise the temperature within the vessels so that the reaction starts and proceeds at an appropriate rate. In general, the initiation temperature should be above 15 ° C, but should not exceed this temperature because the exothermic and hydration heat provide most of the heat required for the reaction.

Since the reactions taking place are ionic and require some water, in order to obtain a free-flowing end product, it is expedient to control the moisture of the reaction mixture when the reaction has ended and even during the reaction. This is easily achieved by withdrawing excess water from the inside of the reactor via a vacuum line. Since the temperature of the start-up rises to over 100 ° C due to the exothermic reaction, it is advisable to have a vacuum between 80 and 90 kPa. Moisture control reduces the size of the crystals formed in the end products, many of which are quite water soluble. The formation of large crystals is undesirable because it is incompatible with the free-flowing properties desired in the end product.

As mentioned above, stirring within the reaction vessel is advantageous for accelerating the reaction as well as for controlling the particle size of the end product. Careful stirring or keeping in motion as well as checking the stirring speed during the later reaction stages, during which a lot of moisture can be present, ensures a free-flowing, powdery product. Appropriate stirring ensures heat transfer to remove the water vapor and prevents crystallization at low temperatures and crystal growth beyond the desired size. It also helps to keep the products and reactants below their melting points, since melting or fusing within the mixture also leads to particle sizes outside the desired ones.

The completion of the reaction and the removal of the water vapor is achieved at a temperature in the range of 40 to 100 ° C and preferably 45 to 95 ° C.

Suitable commercially available reactors for "dry" or solid mixing and the reaction according to the invention include e.g. the Day Mark II mixer, which is a jacketed, conical vessel equipped with one or more screw-type internal stirrers that are parallel and closely spaced from the inner conical

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Rotate the surface of the vessel and at the end of which there is a 96 kPa vacuum source, the jacketed Patterson-Kelly mixer, which is equipped with amplifier baffles and has hollow support axes connected to vacuum sources, and the Stokes rotary vacuum dryer.

Such devices or equivalents thereof make it possible for the method according to the invention to run economically, even in large-scale processes.

The following examples illustrate the invention. The percentages are based on weight.

example 1

A jacketed Day Mark II conical mixer equipped with a screw stirrer was charged with 35.1 kg of wet Na2EDTA cake with a purity of 93%. The vessel was heated using oil in the jacket, heating the material to 15 ° C, after which 7.8 kg of zinc oxide (99%) was added. The heat released heated the mixture to about 40 ° C. 1.35 kg of water were sprayed onto the mixed mass. The vessel was closed and pumped to about 84.7 to 94.8 kPa vacuum. The batch was then further heated to about 82-85 ° C by the hot oil in the jacket. Vacuum pumping continued while heating. The heating was stopped and the batch temperature dropped to about 65 ° C. Stirring was continued for an additional hour and then the product was removed. The free-flowing, powdery product consisted of 45 kg Na2-Zn-EDTA with a purity of 85.5%.

Example 2

The procedure of Example 1 was repeated using 11.2 kg of zinc carbonate (ZnC03) instead of the zinc oxide, and 45 kg of NavZn-EDTA were obtained with a purity of 85 to 86%.

Example 3

45 kg of Na3-EDTA was prepared by adding 39.9 kg of Na2-EDTA (93%) to the day dryer of Example 1 and then 4.5 kg of NaOH flakes (98%) and 4.5 liters of water. After the exothermic reaction was completed and heated to 65.5 ° C, vacuum drying and stirring was continued until a free-flowing powder could be taken out (about 2 hours), whereby 45 kg of Na3-EDTA with a purity of 87% were obtained.

Example 4

The Day Mark II mixer was charged with 39.9 kg of wet Na2-EDTA cake. Over the course of half an hour, 8.7 kg of a 50% NaOH solution were sprayed uniformly under vacuum (94.8 kPa) to stop the reaction. After the exothermic reaction was completed and heated to 65.5 ° C, vacuum drying and stirring were continued until a free-flowing powder could be taken out (about 2 hours), whereby 45 kg of Na3EDTA with a purity of 87% were obtained.

Example 5

Na3EDTA is prepared by loading a 0.028 m3 Patterson Kelly twin vacuum mixer with 75.6 kg of 93% Na2-EDTA cake. 18.0 kg of NaOH (50%) was sprayed into this feed under a vacuum of 94.8 kPa. The exothermic reaction caused the temperature of the reaction mixture to rise to 37.8 to 46 ° C. Heating and vacuum drying continued for about 1 hour and 92.7 kg of Na2-EDTA were recovered as a product.

Example 6

The procedure of Example 4 was followed using 23.6 kg of a 50% solution of Na2CO3 instead of the 50% NaOH solution which was sprayed into the day reactor under vacuum (94.8 kPa) . After the exothermic reaction was complete, the mixture was heated to dryness in vacuo and the product removed to give 85% Na3-EDTA.

Example 7

The device of Example 1 was charged with 43.5 kg of Na2-EDTA and the charge was sprayed with 18 kg of 50% NaOH solution under vacuum (94.8 kPa). After the exothermic reaction was complete, the mixture was heated for about 1 hour. 45 kg of Na4EDTA with a purity of 91% were obtained.

Example 8

A Stokes-Pennwalt rotary vacuum dryer with a double spiral stirrer, which was heated with steam in the jacket at a pressure of 172.25 kPa, was charged with 1620 kg of moist Na2-EDTA cake and mixed to break up the lumps. 167.4 kg of NaOH beads (11% excess) were charged. 9 kg of water were sprayed in to rinse off the material on the stirrer. After mixing for half an hour with the flap open, the mixture was dried to a 90.2% Na3 EDTA sample. The pH of a 10% solution of the product was 8.2 and the color 15 APHA.

Example 9

The rotary vacuum dryer of Example 8 was charged with 1620 kg of wet Na2-EDTA cake after the previous batch had been removed. After mixing to break up the lumps, 72.3 kg of NaOH beads and 54 kg of water were added and the mixture was mixed with the dryer flap open. The material was removed after drying using steam in the jacket at a pressure of 172.25 kPa in the form of Na3-EDTA with a purity of 92%. The pH of a 10% solution of the product was 8.2 to 8.3 and the color 15 to 25 APHA.

Example 10

A clean rotary vacuum dryer was loaded with 1350 kg of wet Na2-EDTA cake. After mixing to break up the lumps, 45 kg of sodium sulfate and 264.6 kg of NaOH beads were added and mixed for about half an hour with the feed door open. The mixture was dried under vacuum to Na4-EDTA with a purity of 87.8% and removed. The powder was sieved and any lumps were ground to a uniform size.

Example II

A clean rotary vacuum dryer was loaded with 1350 kg of wet Na2-EDTA cake. After mixing to break up the lumps, 238.5 kg of CuO were added. 108 kg of water were then introduced and the reaction mass was heated to about 90 to 100 ° C. with 172.25 kPa water vapor in the jacket and the stirrer. After mixing for about two hours at about 90 ° C., the mixture was examined for an excess of Na2EDTA. 58.5 kg of CuS04-5H20 and 39.1 kg of NaHC03 were added to the reaction mass and mixed for 1 hour to reduce the free Na2-EDTA to small amounts. The reaction was then carried out under vacuum in the presence of steam in the jacket and stirring to a moist 5

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of about 10% dried. After drying, 900 kg of Na2-CuEDTA were removed.

Example 12

1350 kg of moist Na2-EDTA cake and 217 kg of zinc oxide were fed to a clean rotary vacuum dryer and mixed for half an hour. About 108 liters of water were added to obtain a moisture content of 30 to 35% in the reaction mass and the mixture was heated to 90 to 95 ° C. with steam in the jacket and shaft. After a reaction time of two hours, the paste was examined for free Na2-EDTA and adjusted with 4.5 kg of NaHCO3 and dried under vacuum. 90.75 kg of Na2-Zn-EDTA were obtained. The product was sieved and ground to a uniform size.

Example 13

After removal of the previous batch, 900 kg of moist Na2-EDTA cake and then 217 kg of ZnO were added. After mixing for 15 to 30 minutes, 1081 water was sprayed in and the dryer was heated to 90 to 95 ° C. The mixture was mixed for 2 hours and examined for free Na2EDTA. 4.0 kg of ZnS04-7H20 and 6.3 kg of NaHC03 were added to make up the excess Na2-EDTA

to decrease and adjust the pH. After the batch had been adjusted, it was dried under vacuum to give a 63% sample (EDTA base) and removed. 725.8 kg of Na2-Zn-EDTA were obtained.

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Example 14

202 kg of fine MnO and subsequently about 108 kg of water were added to 1350 kg of Na2EDTA, which had been fed to a clean rotary vacuum and mixed therein. The batch was heated to 90-95 ° C with stirring until the reaction mass became a flowable, thin slurry. After mixing for two hours at 90 to 95 ° C, a sample was examined for free Na2-EDTA. (The compensation settings were made as follows: Too high a free Na2-EDTA content is compensated using MnS04H20 and NaHC03. Excess MnO is corrected using Na2-ED-TA. The pH settings of the product are made using NaHC03 or dilute 20 H2S04). After the necessary adjustments (using 55.3 kg of wet Na2-EDTA cake, 7.2 kg of MnS04 H20 and 21.1 kg of NaHC03), the mixture was dried and 729 kg of product were removed and then ground to a uniform size.

C.

Claims (10)

668 256 1. Process for the preparation of salts of ethylenediaminetetraacetic acid of the formula NaOOCH2C ^ CH2COO- ^ N-CH2-CH2-N ^ 3-nMn + NaOOCH2Cx CH2COO- where n is 1 or 2 and M is Na, K, Li, Rb, Zn, Ca, Fe, Mn or Cu or, if one of the symbols M is Na, K, Li or Rb, the other M can also be H. , characterized in that under vacuum 1 mol of the moist cake of the EDTA salt of the formula NaOOCH2C «v. CH2COOH n-ch2-ch2-n cC NaOOCH2C - ^ "^ CH2COOH With (a) 1 or 2 moles of a compound of the formula M + OH- wherein M + represents Na +, K +, Li + or Rb +, or (b) 1 mole of a compound of the formula 2. The method according to claim 1 for the production of Na3-EDTA characterized in that a wet cake of Na2-EDTA is mixed under vacuum with 1 mol NaOH as compound MOH. 2nd PATENT CLAIMS 3. The method according to claim 1 for the production of Na4EDTA characterized in that a wet cake of Na2-EDTA is mixed under vacuum with 2 mol NaOH as the compound MOH. 3-nMn + mX3 ~ m_ where M is Li, Na, K, Rb, Ca, Mn, Fe, Cu or Zn, XO, OH or C03 and m and n each independently represent 1 or 2, where, if M is Li, Na, K or Rb represents, X is not OH, mixes in the presence of sufficient water to ensure ionization, which dissipates the resulting exothermic heat and the water vapor formed and finally collects the product formed. 4. The method according to claim 1 for the production of Na2-Zn-EDTA characterized in that a wet cake of Na2-EDTA is mixed under vacuum with 1 mol of ZnO as compound MX. 5. The method according to claim 1 for the production of Na4EDTA characterized in that a wet cake of Na2-EDTA is mixed under vacuum with 1 mol Na2C03 as compound M2X. 6. The method according to claim 1 for the production of Na2-Mn-EDTA characterized in that a wet cake of Na2-EDTA is mixed under vacuum with 1 mol of MnO as compound MX. 7. The method according to claim 1 for the production of Na2-Cu-EDTA characterized in that a wet cake of Na2-EDTA is mixed under vacuum with 1 mol of Cu (OH) 2 as compound MX2. 8. The method according to any one of claims 2 and 3, characterized in that NaOH is added as a 50% aqueous NaOH solution. 9. The method according to claim 1 for the production of Na3-EDPA, characterized in that a moist cake of Na2EDTA is mixed under a vacuum with 1 mol of Na2C03 as compound M2X. 10. The method according to claim 1, characterized in that the reaction mixture, in order to ensure completion of the reaction and removal of the water vapor, is heated to a temperature between 40 and 100 ° C.