DE2236120A1 - Aminocarboxylic acid alkali metal salts - prepn from alkali hydroxide and amino alcohol contg at least one primary alcohol gp usi - Google Patents

Abstract

Reaction is effected in the liq. phase in a closed reaction zone at 199-288 degrees C with an amt. of alkali hydroxide in excess, with respect to the stoichiometric amt. equivalent to the no. of alcohol functions available in the amino alcohol, in the presence of 25-70% of water by wt. of the total initial charge, and as catalyst a metal deriv. of Cd, Ni, Pd or Zn. The press. in the reaction zone is kept at 8.5-120 atmost. such that the p.p. H2 in the same zone is less than half the total press. in the reaction zone. Layer yields in short reaction times are obtained. Thus nitrilotriethanol and sodium hydroxide are reacted in the presence of water and cadmium oxide catalyst to given a 90% yield of Na3NTA (sodium nitrolo acetate).

Description

Process for the preparation of aminocarboxylic acids from aminoalkanols The invention relates to an improved process for the preparation of alkali metal salts of aminocarboxylic acids from aminoalkanols. In particular, it relates to manufacturing of alkali metal salts of tertiary aminocarboxylic acids from tertiary aminoalkanols.

The synthesis of aminocarboxylic acid - alkali salts catalyzed by The reaction of amino-alkanols with alkali metal hydroxides in the aqueous phase is complete the publication by Dumas and Stas (Ann. 35, 129-173, 1840) is known per se. Later work in this area focused in particular on conversion of the amino alcohols ile alkali metal salts under mild conditions, with the The result was that the amino groups remained largely intact, and thereby the reaction in the carboxylic acid alkali salts was favored.

Among the alkali salts of the aminocarboxylic acids, the trisodium salt has The nitrilotriacetic acid is of particular interest as it is an effective substitute for all, or at least most of the phosphate-containing release agents in the combined Represents detergents. From the ecological From a standpoint, it is urgent necessary that phosphates no longer, or at least only reduced to a certain extent. Measure get into natural watercourses, thereby reducing what is currently observed exceptionally strong growth of certain, phosphate-loving plant organisms is achieved. The use of the trisodium salt of nitrilotriacetic acid as Part of detergents is an attempt to substantially reduce a possible pollution by phosphate.

waste.

While the previous processes for the production of A.inocarbonsäuresalze the way to a reasonably high standard of production is only seen in this have that one in the reaction of alkali metal hydroxides with aminoal -kanols the greatest possible yield is achieved, with relatively reasonable yields only thereby what could be achieved was that - according to current knowledge - the response times were extremely extended were roughly in the range of many hours to several days.

The present invention is based on the object of the greatest possible -Yields of more than 80% of the desired alkali metal salt of aminocarboxylic acid with reaction times of less than two hours.

It has now been found that in the manufacture of alkali metal salts of the aminocarboxylic acids from aminoalkanols by a process based on dehydrogenation is based on amino alcohols, a significantly better time-yield factor is achieved can be that an excess of the sttfltometric amount of alkali metal hydroxide and the presence of at least as much water as necessary is provided therewith the reactants reliably in solution under the relevant reaction conditions remain that the presence of a dehydrogenation catalyst is also provided and that the reaction conditions are influenced to the effect that the hydrogen partial pressure makes up less than 50% of the total pressure in the vapor phase of the reaction chamber.

See the reaction conditions and the proportions of the batch a liquid phase reaction, with the proportion of water in the system more than 25 percent by weight based on the total charge, and preferably between 30 and 70 percent by weight, based on the batch. The amount of trodium hydroxide, based on the amount of aminoalkanol present in the batch before the start of the reaction, must have an excess over the stoichiometric minimum, and is in the Usually in the range between 1.25 to 3 mol per equivalent of aminoalkanol. The catalyst Any metal from group II B and from group VIII of the Periodic Table and is preferably a cadmium-containing component, which is referred to below as "cadmium catalyst site. In the reaction mixture it in an amount which - based on metallic cadmium - generally in Range between 0.2 and 20 gram atom of cadmium per 100 moles of aminoalkanol, and preferably ranges between 1 and 10 gram atom of cadmium per 100 moles of aminoalkanol.

With such a composition of the reaction mixture it is achieved that the reaction takes place in the liquid phase, the loss of water is at a Minimum or kept at a negligibly small value and the reaction temperatures The range is between 1990 C (390 ° F) and 2880 C (5500 F) and preferably in the range between 2180 C (4250 F) and 260 ° C (500 ° F). To achieve that Hydrogen partial pressure less than 50% of the total vapor pressure in the reaction zone the pressure conditions in the reaction zone would correspond to the temperature -tur range in which the reaction is carried out, usually between 7.2 atll (125 psig) and 14.4 atmospheres (150 psig) for the lower temperature range and in the range between 30.3 atmospheres (525 psig) and 101.1 atmospheres (1750 psig) for a reaction temperature of 2880 C (5500 F) held. The preferred temperature range is between 2180 C (4250 F) and 260 ° C (5000 F), with pressures typically between 14.4 atmospheres (250 psig) and 17.3 atg (300 psig) for the lower temperature range and between 27.4 atg (475 psig) and 38; 1 atU (660 psig) for the higher temperature range. if the reaction carried out within the specified pressure and temperature range it leads to yields of at least two hours or less 80% of theory.

Although the features of the invention described above Process generally refers to the production of alkali metal salts of aminocarboxylic acids from aminoalkanols can be used, the following detailed description of the process for reasons of simplification mainly using the example of production of the trisodium salt of nitrilo-acetic acid.

The dehydration reaction of nitrilotriethanol with at least one The stoichiometric amount of sodium hydroxide goes through three stages to the desired one End product, the trisodium salt. So first the monosodium salt (Natri -um N, N-bishydroxyethylglycinate), then the disodium salt (disodium N-hydroxyäthylimlnodiacetat) and ultimately the trisodium salt, the desired end product is formed. At Sedem In these steps, two moles of hydrogen are exchanged for one mole of sodium; at the same time, each of these process steps is exothermic at higher pressures. Through this if the reaction tends towards higher temperatures on the one hand, on the other hand, towards the release of fairly large amounts of hydrogen to go through. So far, the regulation of the temperature has been through a regulation the speed of the reaction, i.e. the slower the reaction, the more The heat from the exothermic process can be dissipated more easily, this would speak on the other hand, that the reaction is carried out at a relatively high pressure, i.e. at 28.9 atm up to 144.5 atmospheres (500-2500 psig) in a closed system. The reaction tends to generally to run faster as the temperature rises. However There are more and more production impurities and other harmful effects on as soon as the Temperature above 260 ° C (500 F) and especially when it rises above about 2880 C (5500 F).

The prior art methods do not suggest that the pressure is a reaction parameter of particular importance. It was, however found that the hydrogen pressure is related to the rate of reaction and under special conditions also on the yield of the desired product particularly affects. High pressures, e.g. over 144.5 atü (2500 psig) in addition, that the cadmium-catalyzed dehydrogenation of triethanolamine with sodium hydroxide is inhibited or completely prevented. However, low pressure leads to one surprising and clearly recognizable increase in the reaction rate, in particular then when the hydrogen partial pressure in the reaction system is close to is reduced from practically zero.

In order to make the best possible use of the system and to produce To achieve nitrilo-acetic acid at the lowest possible cost must be the highest possible The speed of reaction with the necessary selectivity is aimed for Result can be achieved according to the invention that hydrogen from the reaction side Part of the plant as quickly as it is formed, is removed and in that the Hydrogen partial pressure across the reaction mixture as close to zero as possible is held. One measure to achieve this is to have the response is carried out under reflux conditions, so that the hydrogen formed quickly with the rising solvent, in this case water vapor will. The water vapor is condensed and returned to the reaction system, in order to maintain the water concentration at least with the minimum value described above, the hydrogen is blown off through a corresponding throttle valve System running. The reflux conditions must be chosen so that an excessive Water loss is prevented. II The reaction equilibrium of the reaction of alkali metal hydroxides with amno alcohol Formation of metal alkoxides and water is well known. To the extent that water is released from the reaction system, the reaction equilibrium is shifted in the direction of the end products and the components, that are necessary to carry out the desired reaction no longer remain in the system. More precisely, this means »a reaction participant has then been removed and the important stoichiometric ratio is no longer given. How to replace them of the water at periodic intervals allows a restart of the reaction, but only with a considerable amount of time lost. Therefore must the total pressure of the reaction system selected such that at the desired Reaction temperature the water content of the reaction mixture not less than Is 1 mole per mole of hydroxyethyl group to be reacted. Such prints lie generally above the 7.2 atmospheres (125 psig) mark.

On the other hand, the hydrogen pressure can usually be advantageous can be used to regulate or moderate the reaction rate, e.g. in Initial stage of a process that works with a very large batch, or during the start of a continuous process. The initially existing Possibility of training a very high reaction speed can be achieved by a higher hydrogen partial pressure are attenuated, at the same time also the Risk of the formation of a violent temperature surge is reduced. The heat of reaction can then also be distributed very effectively over the first part of the reaction, without extensive and subsequently superfluous measures to prevent the "Passing through" the temperature is necessary as a pole of an overly rapid reaction process are.

Another advantage of running the process at low hydrogen pressure results in the effective utilization of the cadmium catalyst. It was found, that an effective catalyst appears to be in the form of a soluble cadmium (II) complex must be present. The Rexdox potential of the pair cadmium (II) / cadmium (O) is in the temperature range in which the method is carried out, already in such a way low that / a relatively low hydrogen pressure is sufficient to generate cadmium (ii) to reduce to metal. Within the range that can be used in practice Process conditions sufficient hydrogen partial pressures of about 50% of the Total vapor pressure in the Realctionszone, so that the whole or at least essential certain parts of the cadmium catalyst content are reduced to metallic form, which in turn is catalytically ineffective. Accordingly, it would turn out to be a continuously run processes accumulate metallic cadmium in the reaction vessel 0 Although metallic cadmium tends to go back into solution in an alkaline environment to go, too high a partial pressure causes an opposing driving force The metallic stage then represents the equilibrium stage in it by the Cadmium as an accelerating agent makes ineffective and the sedimentation tendency reinforced. However, if the hydrogen partial pressure is less than 50% of the total pressure the equilibrium shifts from the metallic form of the cadmium towards the complex. The complex can dissolve and intervene in the reaction.

The exact mechanism by which cadmium acts in this reaction Accelerating effect is not known with absolute certainty. It is to assume that a soluble in the nitriloethanol-alkali hydroxide-water system Complex is formed with bivalent cadmium. It must be assumed that that bivalent cadmium when exercising its accelerating effect through reduction transferred to a lower valence state, thereby forming a carboxylate group will. The cadmium with the lower valence level is then immediately through Water re-oxydates with a thorough release of hydrogen and is available renewed complex formation available again, with the formation of Complexes with compounds is possible which contain carboxylate groups. Of the complex from nitrilotriacetic acid and sodium then predominates accordingly the law of mass action as the reaction approaches its end. Although this theory is quite plausible, it can only be seen as a possible one Explanation, but not serve as a basis for control measures. The complex from cadmium-NTA (nitriiotri-acetic acid) -sodium is under the reaction conditions something in the aqueous solution of the end product NTA (Na) 3 (trisodium nitrilotriacetate) soluble, but at normal temperatures it is essentially insoluble and can thus easily be removed from the end product by physical means, e.g. by filtration, Centrifugation or the like. To be deposited.

The cadmium-NTA-Na complex isolated in this way also has the advantage that it can be returned to the reaction system wherever it is not only found in the mixture of aqueous solutions of nitrate and triethanol Alkali hydroxide dissolves, but also directly the original cadmium (II) complex retreats, with its obviously fully restored acceleration effect versus the conversion of nitrilotriethanol / water / alkali hydroxide into NTA (Na) 3.

The examples below show this in many ways advantageous effects of the method according to the invention. These examples serve more about the explanation of characteristic or exemplary embodiments than the presentation of the scope.

Example 1 For the exemplary implementation of a discontinuous Procedure is an autoclave with about 3.8 1 volume with 300 g of nitrilotriethanol, 300 g of sodium hydroxide (excess 24 k), 550 g of water and 15 g of cadmium oxide are charged. The closed autoclave is then used with a water-cooled reflux condenser a proportionally adjustable pressure relief valve, that to about 28.9 atmospheres (500 psig), and then attached a hygrometer to it -sen. From the point in time from which the first gas escapes or the total pressure of 28.9 -atü (500 psig) is reached to the point where 133 liters (9.4 SCF) have escaped to gas (+99 ffi theory), it takes about 80 minutes. To cooling to room temperature turns water up to total weight about 1500 g added. The insoluble complex of C1-NTANa is filtered off (dry weight 32 g). After removal of the remaining cadmium by precipitation as sulfide and subsequent filtration is the filtrate with the help of nuclear magnetic resonance spectroscopy analyzed using sodium acetate as a standard. The spectrum shows that 97% of the hyd thyl groups were converted to carboxymethyl groups. This matches with a utilization of the batch of more than 90% and a yield of NTA (Na) 3 of 90% (without taking into account the proportion that was deposited with the catalyst2 Example 2 The following shows the inhibiting effect of high hydrogen pressures will.

A 300 cc autoclave was filled with 0.5 g of cadmium oxide for each batch 10 g each of nitriloethanol, sodium hydroxide and water are charged. The autoclave was then filled with hydrogen up to the pressure given in the table. Thereafter it was heated with the temperature control device set to 2050 C (4000 F) until no further increase in pressure could be observed.

Heat developments were observed in batches A and B, where the temperature briefly rose above 2050 C (400 F). The reaction products were dissolved in water, filtered and analyzed by evaluating the nuclear magnetic resonance spectrum.

On water end - - PH on the reverse - (time) composition.

set substance - pressure end set hour - of the reaction additive trietha- the product nolamin atü (psig) atü (psig) atü (psig)%% Mono +% Di ++% NTA +++ A - (-) 69.4 (1200) 57.8 (1000) 100> 8 - - 95 B 28.9 (500) 109.8 (1900) 98.5 (1700) 100 8 42 50 C 57.9 (1000) 132.9 (2300) 121.4 (2100) 100> 8 76 16 8 D 86.7 (1500) 156.1 (2700) 144.5 (2500) 46> 8 100 - -E - (-) 11.5 (200) ~ 96 (-10) 100 1.8 - - 95 F 11.5 (200) 11.5 (200) ~ 96 (~ 10) 100 1.9 - - 92 +% Mono means:% bishydroxyethylglycine as sodium salt, Di Di means:% Hydroxyäthyliminodi-acetic acid as sodium salt, +++% NTA means:% nitrilotriacetic acid as sodium salt.

Approaches v and F were used as comparative tests according to Conditions of the method according to the invention in the same way and with similar Cargo additives in the closed autoclave heated to 2050 C (4000 F), however with the difference that there is a reflux condenser and a pressure regulating valve in the autoclave closure and a hygrometer is interposed in the line leading away from the pressure regulating valve was.

Example 3 On a continuous procedure at 199 ° C (390 ° F) and for continuous discharge of hydrogen under controlled The apparatus used for certain pressure conditions will be the storage vessels for the supply of the starting materials in a ratio of three moles of sodium hydroxide and 20-50 moles of water per one mole of nitriloethanol charged. The cadmium is used as an oxide in an amount of 0.05 mole per mole of nitriloethanol was added. The normally insoluble orange-red solid @@@ mumoxid dissolves quickly and gives a colorless solution. In order to clearly show the effect of the influence of the hydrogen partial pressure, the residence time in the reaction zone is adjusted to about five minutes.

The general progress of the reaction and the speeds of the Individual reactions can be determined by determining the consumption of sodium hydroxide in the exiting Reaction mixture are followed. The influence of the hydrogen pressure on the reaction rate can be inferred from the following data that at a reaction temperature from 1990 C (3900 F).

Pressure +) partial pressure PH in% ratio H2 of total ve Re -ten pressure ++) actionatü (psig) atü (psig) atü (psig) speed F 11.5 (200) o.6 i10) 5% 11.4 1 G 15.0 (260) 3.5 (60) 23% 8.2 0.7 H 20, £ (360) 9.2 (160) 44% 3.5 0.3 +) total vapor pressure over the reaction system, ++) determined by consumption of sodium hydroxide.

In the aforementioned experiments, the flow rate and concentrations were kept constant. The data listed clearly show the advantage of the procedure at a low hydrogen partial pressure and justify in conjunction with corresponding other observations suggest trying to operate at partial hydrogen pressures less than 50% of the total steam pressure. The ones useful for this reaction Catalysts are not limited to starting initiation for the system depends exclusively on the cadmium (II) complex described above is. Cadmium in metallic form or the equivalent is also suitable Salt or complex with at least partial and sufficient solubility in the system triethanolamine / alkali hydroxide, in which case an effective amount of the cadmium (II) complex described above is formed. Show more metals' also the desired catalytic properties, but not necessarily with the same level of effectiveness, such as nickel, palladium and zinc. While sodium hydroxide is the most suitable alkali metal salt, but are other alkali and Earth metals suitable in the form of their hydroxides, e.g. lithium barium hydroxide hydroxide, Calcium hydroxide / and potassium hydroxide. Further experiments have shown that response times or residence times in the reaction zone in the range between ten minutes and ten Hours are possible, but the best results are achieved when these Times are less than two hours. The preferred response time is no more than thirty minutes.

Example 4 A copper-lined, approximately 3.8 liter capacity Autoclave is with 300 g of nitrilotriethanol, 300 g of sodium hydroxide, 425 g of water and 39 g of the crude cadmium-NTA (Na) complex from a previous experiment were charged. After the autoclave has been pressurized to 23.1 atmospheres (400 psig) and was brought to the reaction temperature, the pressure is proportional with the help of a acting pressure regulator at 23.1 atmospheres (400 psig). The hydrogen escapes through the pressure control valve and is passed through a hygrometer.

The reaction mixture is heated to 2180 C (4250 F) for 7 hours. A total of about 125 liters (E, 8 SCF) of hydrogen (93% of theory) are measured. After cooling, 857 g of water are added and the mixture is filtered. The catalyst precipitate weighs 31.5 g. The filtrate is then treated with sodium sulfide to remove any remaining Precipitate traces of cadmium, and then analyze for the content of NTA (Na3). The end product consists of 75% NTA (Na) 3 and 25% IDA (the sodium salt of iminodiacetic acid). It can be seen from this that a Procedure to a good degree of implementation, but despite the lengthened ones Reaction time leads to an unsatisfactory composition of the end product. The reaction time can be increased by carrying out the process at temperatures above 2180 C (4250 F) and shortened by a relatively low water content, like the results of further experiments shown in the table below demonstrate. The total pressure in these runs was 23.1 atmospheres (400 psig) in all Cases.

1.) reaction 2.) 2.) 1.) time rate water temperature yield Yield g Stung C (F) NTA (Na) 3 IDA (Na) 2 CDO den A 600 2050 (4000) 73s6 26; 4 7.5 20 B 375 232 ° (450 °) 87.9 21.1 5.0 22 C 375 233 ° (452 °) 89.8 10.2 8.5 22 There were some experiments were carried out in which the initial charge to the reaction zone It was composed of one part by weight of nitrilotriethanol and 3 parts by weight of NaOH and 3 parts by weight of water and a corresponding amount of cadmium catalyst. The total pressure was maintained during the entire reaction at a temperature of 2500 C (500 ° F) and held at about 27.4 atmospheres (475 psig) but with the escape the vapor phase was not selectively controlled. The loss of water that occurred in this way from the system resulted in the formation of a non-liquid cake in the reaction vessel. The trisodium salt content obtained after removing the cake and analyzing it nitrilotriacetic acid is far from satisfactory. Furthermore - regardless of the adhered to.

Time, temperature and pressure conditions - no further transformation to the desired product more observed after that originally in the reaction zone existing water had gone away. Further experiments showed that the cake formation occurs even if you have the desired reaction - at least partially - continues to run off »if the water content in the reaction system is less than 25%, based on the total weight of the reaction mass. It was in the same way found that the most practicable process conditions are given when the reaction mass has the consistency of a pumpable liquid retains, which in turn requires that water in an amount of about 30%, based to the weight of the total reaction mass, is present.

In these and similar experiments it was also observed that - although the rate of reaction then increases with temperature, - temperatures above 2600 C (500 ° F) significantly adversely affect the desired reaction and that at about 2880 C (5500 F) and above, degradation products and undesirable side reactions become as clear as completely unbearable.

In summary, it should be noted that the procedure within the certain limits and especially while maintaining a hydrogen partial pressure of less than 50% of the total pressure in the reaction zone lead to the desired Product in the minimum quantity specified at the beginning and in less than two hours can be obtained.

So the process can also be carried out in-house under similar conditions more reasonably extended periods of time can be continued without loss of material both in terms of quantity and in terms of the quality of the final product -duktes occur.

Examples 5 to 8 In experiments on other amino alcohols, e.g. on diethanolamine (5), mono- (6) and dipropanolamine (7) and HezaäthanoltrlAthylenetetramin (8) with appropriate adjustment of the amount of alkali hydroxide under the appropriate Consideration of the hydrogen to be exchanged for the respective amino alcohols in the respective composition of the reaction mixture, it was found that high Yields can be achieved with correspondingly shortened reaction times if the Conditions with regard to water content and partial pressure of water in 0 Example 9 I-i a nickel-lined, 300 ml autoclave sources 17.4 g Bishydroxyäthylpipey'azin »10 g sodium hydroxide, 0.5 g of cadmium oxide and 30 g of water were used 0 After a reaction at 11.5 atmospheres (200 psig) The end product was treated as described in Example 1 for two hours and isolated. The one carried out using sodium acetate as the standard substance Analysis by nuclear magnetic resonance spectroscopy showed essentially complete Conversion of the Bishydroxyäthylpiperazin and - based on the Bishydroxyäthylpiperazin a 96.1% yield of disodium salt.

Brief Summary of the Invention: The preparation of salts of the Aminocarboxylic acids from aminoalkanols and alkali metal hydroxides in the presence of a Catalyst is significantly improved in terms of higher yields at shortened Reaction times when the reaction is in the presence of higher water concentrations and significantly lower hydrogen partial pressure conditions. Particularly excellent results are achieved in the manufacture of the trisodium salt of nitrilotriacetic acid from nitrilotiethanol and aqueous alkali.

- Expectations

Claims (6)

Claims | 1.)) Process for the production of amino acid alkali salts By reacting alkali metal hydroxide with an amino alcohol with at least one primary alcohol group, characterized in that the reaction is completed in a Reaction chamber in the liquid phase and in the temperature range between 199 ° C (3900 F) and 2880 (5500 F) takes place, the approach the corresponding amino alcohol and, based on its primary alcohol groups, an excess over the stoichiometric Amount of alkali metal hydroxide, furthermore water in the range between 25 and 70 percent by weight, based on the entire approach, as well as an accelerating amount of one catalytically active metal content of the group cadmium, nickel, palladium and zinc and the following measures for improvement are observed a) Removal of a mixture of water and water vapor as overhead "vapor, b) Implementation of this mixture through a cooler and condensation of the water there, + c) recirculation of the condensed water into the reaction zone, d) throttling of the Vapor or gas discharge from the cooler in such a way that there is a pressure in the reaction zone in the range between 7.2 atmospheres (125 psig) and 101.1 atmospheres (1750 psig), and a partial pressure of hydrogen sustaining less than 50% of that pressure, with the result that the alkali metal salt of the corresponding amino acid in a yield based on the amino alcohol used, of at least 80% of the theoretically possible amount and is obtained with reaction times of less than 120 minutes. 2.) Method according to claim 1, characterized in that the alkali metal hydroxide Sodium hydroxide and nitrilotriethanol as the amino alcohol can be used. 3.) The method according to claim 1, characterized in that as catalytic effective metal content cadmium the approach in an amount of 0.2 to 20 gram atom, based on metal, per 100 mol of the corresponding amino alcohol are added. 4.) The method according to claim 1, characterized in that the water in amounts between 30 and 70 percent by weight, based on the total weight of the Charge, is used and during the reaction essentially in the reaction zone is held back. 5.) The method according to claim 2, characterized in that NaOH im Approach in an amount between; 25 moles and 3.0 moles per mole of nitrilotriethanol are. 6.) The method according to claim 5, characterized in that the pressure in ranges between 7.2 atmospheres (125 psig) to 8.6 atmospheres (150 psig) at 1990 ° C (390 ° P) and between 27.4 atmospheres (475 psig) to 38.1 atmospheres (660 psig) at 260 ° C (500 ° F).