DD301829A7 - Process for increasing the yield in the single-stage, pressureless synthesis of the sodium salt of nitrilotriacetic acid - Google Patents

Abstract

The invention relates to a process for increasing the yield in the single-stage, pressureless synthesis of trisodium nitrilotriacetate from an aqueous formaldehyde solution and an aqueous sodium cyanide solution. The degree of conversion of sodium cyanide to trisodium nitrilotriacetate is increased to at least 80% when the sodium cyanide solution used contains sodium formate. The aqueous solution of trisodium nitrilotriacetate prepared in this way is free of corrosive ions and can be used without further treatment to remove contaminants from heat exchangers or as an additive to detergents {trisodium nitrilotriacetate; Increase in yield; Formaldehyde; sodium cyanide; sodium; Solution, aqueous; Ions, corrosive; Detergent additive; Wärmeübertragerreinigung; Reaction, one-step}

Description

Characteristic of the known state of the art

It is known that the synthesis of the sodium salt of nitrilotriacetic acid by reacting monochloroacetic acid, ammonia and sodium hydroxide succeeds (DD-PS 156259) The disadvantage of the method described is that, based on trisodium nitrilotriacetate, the triply molar amount of sodium chloride forcibly incurred that a complex purification procedure is followed to remove the sodium chloride or that, if the purification is omitted due to the high chlondion concentration, a high corrosivity to metals results. It is furthermore known that trisodium nitrilotriacetate can be prepared in a two-stage process (DE AS 1 768 937, DE-AS 1499391, US Pat. DE-AS 1 618 002, DE-AS 1768257, DE-AS 1805404, DE AS 1913853). The nitrile of nitrilotriacetic acid is prepared in a first stage at pH values of less than 3 from formaldehyde, ammonia or ammonium salts and hydrocyanic acid also in situ from an alkali cyano The disadvantage of the process described is that the acidic reaction medium must be neutralized by additional Natriumhydroxidgaben that it thereby to the formation of foreign salts and the Contamination of the end product by this comes that a complex two-stage technology is necessary and that it comes as a result of the use or release of the blue acid emissions of highly toxic blue-acid into the environment It is also known that in the reaction of formaldehyde, sodium cyanide, ammonia and sodium hydroxide in the alkaline Medium, the sodium salt of nitrilotriacetic acid is produced in a direct way (DE AS 1643232 DE-AS 1643238 DE-AS 1643415 DE-AS 1793227 DE-AS 2049223, DE-AS 2062435, DE-AS 2124329, DD PS 72011, DD PS 89 849)

In order to achieve high conversions to the sodium salt of nitrilotriacetic acid, very expensive processes are used in DE-AS 1 643232 formaldehyde with Natriumcyanidlosung and 30 times the amount of ammonia are reacted at pressures of 30 at DE in a multi-stage process in DE-AS 1 643238 is Ѵз the Natriumcyaηidmenge replaced by 100% hydrogen cyanide in DE-AS 1 643 415 formaldehyde is mixed with sodium cyanide, which reaction take only 10-20 seconds soil, otherwise Umsatzvernngerung enters According to DE-AS 1 793 227 is carried out with at least a two step procedure in up to 200T and 50at pressure DE-AS 2062 435 refers to the concentration of trisodium nitrilotriacetatlosung prepared with reuse of the separated mother liquor In DE-AS 2,049,223 formaldehyde is presented in a solution of trisodium nitrilotriacetate and doses a Natriumcyanidlosung so that no free cyanide is present The determination of the cyanide content is successful The resulting ammonia is removed from the reaction solution by constant sucking off of air. DD-PS72011 produces trisodium nitrilotriacetate in several stages from sodium cyanide, formaldehyde and ammonia, with a concentration of sodium hydroxide which must be kept very precisely. In DD-WP 89849 The sodium salt of nitrilotriacetic acid is prepared by simultaneous dosing of formaldehyde and Natriumcyanidlosung, but also working in several stages This method also requires a constantly constant concentration of the reactants, since at a molar disproportion, the yield is very strong

A disadvantage of all the processes described above is further that, unless it is assumed that free blue acid is used, with pure or purest sodium cyanide

Object of the invention

The object of the invention is to improve the material economy of a one-stage technology for the preparation of the sodium salt of nitrilotriacetic acid

Explanation of the essence of the invention

The invention is based on the object in the implementation of equimolar amounts of aqueous sodium cyanide and formaldehyde solutions at 0-30 ° C and subsequent saponification at 80-100 ° C to the alkali metal salts of nitrilotriacetic acid to increase the yield to at least 80-85% in only one process step

According to the invention, the object is achieved by adding sodium formate to the aqueous sodium cyanide solution in a mass concentration of 5-40%, based on alkali ynamide. The mass concentration of sodium cyanide is 10-35%.

By adding sodium formate, the yield of trinatalnitrilotriacetate is increased and the formation of sodium formate is suppressed. The advantages of the process according to the invention are that the preparation of trinitrate nitrilotriacetate in a one-step saponification process is possible according to a simple technology, so that it can be converted by the addition of sodium formate A further advantage of the process according to the invention is that an inferior, sodium formate-containing sodium cyanide, a by-product of the production of sodium cyanide, can be used very cost-effectively as an input product. The utilization of the by-product leads to higher yields In addition to saving the cost of its destruction, avoids environmental damage to air and water, which may be caused by the waste products of detoxification

Exemplary embodiments

Example 1 (comparative example)

200 parts of an aqueous Formaldehydlosung (300g formaldehyde / uter) are added under vigorous stirring and cooling to 594 parts of an aqueous Natriumcyamdlosung (165g NaCN / liter) that the temperature is 0-10 ° C After a residence time of 1 hour at the same temperature The mixture is placed in a 2 r utes container containing 300 parts of water, dosed so that the temperature of 96 ± 2 ° C is maintained After the end of dosing is continued at the same temperature until the concentration of ammonia in the distilled ammonia-water Mixture below 100mg / liter decreases yield 55%

Example 2

Experimental procedure analogous to Example 1, wherein the aqueous Natriumcyamdlosung used 2% sodium formate, based on sodium cyanide, 12.1%, contains 80% yield

Example 3 (comparative example)

Analogously to Example 1 using 393 parts of an aqueous sodium cyanide solution (250 g NaCN / liter). Yield 57%

Example 4

Analogously to Example 1 using 393 parts of an aqueous Natriumcyamdlosung (250g / liter) containing 5% sodium formate (20%, based on NaCN) Yield 83%

Example 5

Analogously to Example 1, using 544 parts of an aqueous sodium cyanide solution (180 g NaCN / liter), which is the product of sodium cyanide production (solid) and contains 3.5% sodium formate (based on NaCN 35.7%). Yield 80%

Claims (1)

Process for increasing the yield in the single-stage, pressureless synthesis of the sodium salt of nitrilotriacetic acid by reacting aqueous sodium cyanide and formaldehyde solutions and subsequent saponification by equimolar amounts of the solutions of the starting materials are mixed at 0-30 ⁰ C and then stirred at 80-100 ⁰ C. , characterized in that the aqueous Natriumcyanidlosung with a mass concentration of 10-35% sodium formate in a proportion by mass of 5-40%, based on sodium cyanide added Field of application of the invention The invention relates to a process for increasing the yield in the synthesis of the sodium salt of nitrilotriacetic acid by reacting aqueous sodium cyanide and formaldehyde solution. The solution of tetrasodium nitrilotriacetate prepared in this way can be used immediately for removing contaminants on and in heat exchangers or as an additive to detergents without further purification