CZ119195A3 - Process for preparing n-methylmorpholinoxide with a low content of nitrosomorpholine - Google Patents

Abstract

A method of preparing a 45 to 70% aqueous solutions of N-methylmorpholine oxide with a low content of nitrosomorpholine of up to 50 ppb by oxidising of N-methylmorpholine in an aqueous hydrogen peroxide solution at a temperature of 60 to 75 degrees C with a molar ratio of H2O2/amine=0.5 to 0.9. Hydrogen peroxide acts on N-methylmorpholine, which contains at least one of three hydrogen peroxide stabilisers from a group including sodium pyrophosphate, sodium salt of ethylenediaminetetraacetic acid, sodium stannate at a total concentration of 0.01 to 0.05 % by weight calculated on the basis of the amount of changed amine and common commercial form of the added stabilisers including crystalline water content. It is an advantage to use N-methylmorpholine as an azeotropic mixture with water.

Description

FIELD OF THE INVENTION The present invention relates to a process for the preparation of low nitrosomorpholine (NOMOR) solutions of N-methylmorpholine oxide (NMMO), which is used to prepare cellulosic fibers. A solution containing 50 to 60% by weight of N-methylmorpholine oxide containing up to 300 ppb of nitrosomorpholine is used for this purpose.

The physical dissolution of cellulose together with the simple and quantitative solvent recovery is a radical innovation compared to the viscose fiber production technology, especially in terms of protection of the working and environmental environment.

BACKGROUND OF THE INVENTION

NMMO is produced by reacting N-methylmorpholine (NMM) with hydrogen peroxide according to Equation I.

The reaction proceeds with respect to both reactants in an almost quantitative yield. The patent literature therefore focuses on the quality of NMMO produced.

In the Eastman Kodak Co. patent (US 3,447,939, Germany 1694048 September 2, 1966) directed to the use of cyclic amine oxides as a solvent for macromolectilic agents, the preparation of cyclic tertiary amine oxides, among them NMMO, is described. The oxidation of the amine is carried out with an H2O2 / amine ratio of 0.98. In the example of the preparation of NMMO, the peroxide weighing data is wrong, according to which the molar ratio H2O2 / amine = 0.83, with the yield of oxide per peroxide being highly over 100%. All other data in the patent suggest the application of an almost equimolecular ratio of reactants.

To NMM containing 8% wt. of water is added over 4 to 5 hours with a 35% H 2 O 2 solution at a temperature of 67 to 72 ° C. The mixture was then kept at the reaction temperature for 2 hours and after cooling the excess peroxide was decomposed by the catalase enzyme. The yellow oil was drained by azeotropic rectification with benzene and the anhydrous NMMO was

- and 1 ~ I '' · S - σ '.. i

Λ, Š ^- O ~ '-í> ° I 22'<

The mixture was then poured into acetone, whereby crystals of N, N-10 were obtained in a yield of 89.6% calculated on NMM. The rest of the NMMO and impurities are likely to remain in the mother liquor.

A similar procedure is described in Cs. AO 218 714, where H2O2 / amine ratio = 0.98 and 67-72 θθ are also used. Unlike the Eastman Kodak Co. patent it is only that the reaction mixture is first extracted with acetone, free of unreacted NMM and then dewatering with benzene. This, however, loses the effect of purifying NMMO by crystallization.

For the production of fibers, aqueous NMMO solutions are used and it is therefore advisable to avoid dewatering and crystallization in the preparation of NMMO.

However, a sufficiently pure NMMO solution should be prepared without crystallization.

One of the requirements for NMMO quality is the coloring of the solution. The procedure of US 3,447,939 gives an orange NMMO solution. NDR 254 199 emphasizes that in the preparation of a light colored NMMO solution, the reaction temperature must be kept within + 1 K and the H 2 O 2 solution must be finely dispersed into the reaction mixture, for example by means of a nozzle. The equimolecular ratio of the reactants is at a temperature of 69-72 θθ.

According to another patent of the same group of authors (GDR 259 863) up to 90 wt. The NMM was introduced over 3.5 hours with a 48% H 2 O 2 solution at 75 ° C and then stirred for an additional 5 hours. The stoichiometric ratio of the reactants is used. The reaction mixture is then passed through four cation exchange columns, and phosphoric acid is added to the reaction mixture before entering the 4th column. Unreacted NMM appears to be trapped on the cation exchanger.

Huls AG (EP 0 254 803) discloses that the purity of NMMO is increased if the starting NMM is first rectified if it is oxidized. rectification of NMM prior to oxidation to NMM purity is understandable because NMM, like other tertiary amines, yellows upon storage under the influence of atmospheric oxygen. The question is, however, whether the purification of the starting material before the chemical reaction is even patentable. In the example, the NMM is rectified. with the same amount of water on the column. The resulting azeotropic mixture was charged with 35% by weight of F 2 Cl 2 in a ratio of 1 C 2 / amine = 0.82 over two hours. The mixture was then stirred at 68 ° C for 6 hours. Finally, unreacted NMM and some of the water were distilled off under vacuum so that the solution contained 60 wt. NMMO. The NMMO solution obtained contains 2 ppm H ₂ O ₂ , 0.1 wt. NMM and the acid number is 0.1 mg KOH / g. The solution is yellowish. The cited patent protects the molar ratio H ₂ O ₂ / NMM = 0.75 to 0.90, which ensures complete peroxide reaction. Removal of unreacted NMM by vacuum distillation is easy. . As early as 1967, a process for the production of trialkylamine oxides, in particular triethylamine oxide, was patented in which amine oxides were hydrogenated with an alkali hydrogen carbonate and an alkaline polyphosphate. Polyphosphates and other chelating agents prevent the breakdown of peroxide into water and oxygen. When triethylamine was oxidized without the catalyst system, the yield of H ₂ O _{2 was} only 30.8%, in the presence of catalysts the yield was theoretical.

Of particular importance are the single long carbon chain tertiary amine oxides (especially dimethyllaurylamine) used as surfactants. It has been found that in the oxidation of these amines of hydrogen peroxide, the carbon dioxide has a greater catalytic effect than bicarbonate (US 4,247,480, 1981). C0 ₂ content should be 0.01 to 2% by weight. calculated on tertiary amine. At the same time peroxide stabilizers such as polyphosphates, ethylenediaminetetraacetic acid (EDTA), stalates etc. are added. The H ₂ O ₂ / amine ratio - 1.05 to 1.1 is used because the fatty amine cannot be separated from the oxide solution and has to react completely .

French Patent 2,632,638 (1988) protects the use of CO ₂ as a catalyst in the oxidation of tertiary amines with hydrogen peroxide, the first aspect of the invention being identical to US 4,247,480, which is not disclosed in the prior art. Examples are directed to triethylamine oxide.

More recently, the quality of oxides has been evaluated according to the nitrosamine content, which varies between 50 and 10,000 ppb. Oxidation of dimethyllaurylamine results in carcenogenic dimethylnitrosamine and N-nitroso-N-methyllaurylamine. Nnitrosomorpholine (NOMOR) is mainly produced in the preparation of NMMO.

A first procedure for the preparation of low nitrosamine amine oxides is described in EP307184 (8.9.1987) from Ethyl Corporation.

According to the patent, tertiary amines are oxidized with hydrogen peroxide in the presence of CO2 at a temperature below 45 ° C. While in the presence of CO 2 at 65 ° C and a 10% excess of H 2 O 2, a product containing 96 ppb dimethylnitrosamine was obtained, at a temperature below 40 ° C the nitrosamine content was below the detection limit. 3 to 7 wt. CO2 per amine weight. It can be argued that already U.S. Pat. No. 4,247,480 describes the preparation of oxides in the presence of CO2 at 40 to 80 ° C.

Next

22.11.1988) presence of synergistic ratio H2O2 temperature is concentration patent of Ethyl Corporation (EP 320 694, protects the preparation of tertiary amine oxides

CO2 and ascorbic acids, both having a reduced nitrosamine content. / Amine = 1.0 to 1.5 is preferred, 1.1 to 1.2 is preferred. Reaction to 100 ° C, preferably 45 to 75 ° C,

CO2 0.05 to 5% calculated on the weight of the amine, and the content of ascorbic acid is the same. Three comparative experiments are presented.

only CC &gt; 2 only AK both dimethylnitrosamine 96 37 not detectable.

methyldodecylnitrosamine nedetek. 216 nedetek.

Another patent by Ethyl Corporation (EP 356,918, Aug 29, 1988) protects the preparation of nitrosamine-free amine oxides by oxidation of tertiary amines with hydrogen peroxide in the presence of titanium metal. Both titanium-free and CO2-free are obtained from dimethyllaurylamine a 30% oxide solution containing about 700 ppb of both nitrosamines, in the presence of a titanium plate containing 310 ppb of nitrosamines, in the presence of CO 2 96 ppb, and both.

The latest in a series of patents by Ethyl Corporation (EP 426 084,

30, 10, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9 and 9. With a content of 60 wt. CO2 and more in the gas above the reaction mixture gave an orange product, using a gas containing 20-40% by weight. The carbon dioxide solution was only yellowish.

Albright and Vilson Limited protects (GB 2,252,320,

Stabilization of amine oxide solutions against formation of nitrosamines during production and storage by addition of 2.5 to 20 wt.

bicarbonate or carbonate, calculated on the weight of the amine. Carbon dioxide does not protect against the formation of nitrosamines perfectly, especially when storing solutions, to add chelating agents to hydrogen. In the examples it is given

The oxidation is recommended to prevent the decomposition of peroxide NO group content · When oxidizing a tertiary amine of the trade mark Empigen AB at the H 2 O 2 / amine ratio

= ·. 0.9- at 40 9c, with an addition of 0 4 wt . sodium salts EDTA was the following dependency % wt. NaHCOj na amine. 0 0.71 1.8 3.6 7,15 10 ppb NO _________ 314 611 406 237 64 66 Another patent of the same company (EP 553 800Γ3Ϊ (1992) describes

synergistic effect of bicarbonate or carbonate and organic phosphonate. The patent protects the bicarbonate concentration from 0.05 to 20% by weight and the phosphonate from 0.005 to 5% by weight. by weight of the tertiary amine. Effective phosphonates include aminotrismethylene phosphonate, ethylenediaminotetrakismethylene phosphonate and the like. In oxidation, it is useful to add chelating agents that stabilize hydrogen peroxide and accelerate oxidation but do not affect the formation of nitrosamines. Dimethyl lauryl amine oxide having a nitroso group content of 34 ppb was obtained at a KCl content of 1% by weight of phosphonate-1 to 1% by weight of NaHCO 3 per amine and a stoichiometric ratio of F 2 Cl 2 / amine.

In its patent (EP 545,208, Dec. 6, 1991), BASF states that the nitrosamine content of an oxide solution depends on the content of primary and secondary amines in the starting tertiary amine. The patent protects a process starting from tertiary amines containing less than 0.05% by weight. primary and secondary amines. Preferably, unwanted amines are removed by the addition of reagents such as acyl halides, acid anhydrides, sulfonyl halides, etc. The BASF patent alone describes the preparation of a low nitrosamine-containing NMMO. In a comparative experiment, methylmorpholine was oxidized with a content of. primary and secondary amines. 70% wt. The solution was CH ^ with a molar ratio H2O2 / NMM = 0.9. The mixture was then stirred at 70θϋ for 7 hours. The unreacted NMM was distilled off at 10 kPa to give 57 wt. NMMO solution containing 3100 ppb of nitrosamines. When NMMO was prepared from NMM purified by distillation to a content of 0.02 wt. primary and secondary amines, then contained below ppb nitrosamines.

The same effect was achieved if, prior to oxidation, acetic anhydride was added to the starting N-methylmorpholine in an amount of 0.0045 mol per 1 mol of NMM and the mixture was allowed to react for 1 hour.

Current knowledge on the preparation of NMMO solutions with low nitrosomorpholine content can be summarized as follows:

In the oxidation of tertiary fatty amines with hydrogen peroxide, it has been found that carbon dioxide effectively catalyzes the reaction while reducing the nitrosamine content. It is expedient to combine the action of CO2 with other substances such as titanium metal, ascorbic acid and aminophosphonates. Sodium bicarbonate has a similar effect to CO2. In the patents describing the effect of CO 2 and bicarbonates in the oxidation of tertiary amines with hydrogen peroxide, there is no example of NMM oxidation. Our experiments have confirmed that CO2 increases the rate of NMM oxidation by 10 to 100 times (depending on CO2 concentration) ^{and order of} magnitude reduces nitrosomorphine formation.

The data from the BASF patent (EP 545 208) that NMMs with primary and secondary amines below 0.05% yield a NMMO solution with a very low nitrosamine content during oxidation were not confirmed by our experiments.

NMM behaves differently than trialkylamines when oxidized with hydrogen peroxide. Even without the addition of chelating agents, a high yield of NMMO on hydrogen peroxide is obtained. The reaction proceeds at a sufficient rate even without catalysts such as CO 2 or sodium bicarbonate. Although patents for the preparation of oxides of surfactants usually also include NMMs in the overview of the starting amines, these processes employing a stoichiometric amount of H2O2 are not suitable for the preparation of NMMOs.

SUMMARY OF THE INVENTION

The method of preparing a NMMO solution having a very low NOMO content and at the same time a very slight coloration (colorless or only yellowish) by oxidation of NMM with hydrogen peroxide at a temperature of 60 to 75θΟ and a molar H2O2 / NMM ratio of 0.5 to 0.9 according to the invention is 0.01 to 0.05 wt. hydrogen peroxide stabilizer from the group consisting of sodium pyrophosphate, sodium ethylenediaminetetraacetic acid σ

ο

(EDTA) or sodium state, or a combination thereof, based on the mass of NMM. The concentration refers to the commercial form of the substances, including any crystal water.

In the patent literature, in the case of the oxidation of fatty tertiary amines, it is explicitly stated that chelating agents prevent the decomposition of H ₂ O ₂ and accelerate the oxidation process, but do not affect the nitrosamine content (EP-553,800). Oxidation proceeds NMM j otherwise: when J ^E_ it without oxidation H202nerozkládá chelating stabilizers and chelating agents does not accelerate oxidation. According to our experimental findings, chelating agents reduce the formation of nitrosamines by an order of magnitude. However, stabilizers contained in a commercial solution are not enough to suppress the formation of nitrosamines Η ₂ Ο ₂ ·

The advantage of chelating agents over CO ₂ is that it is easier to handle and, in particular, to better color the product. Since CO ₂ strongly catalyzes oxidation, it is recommended to operate below 40 θθ, which is disadvantageous in terms of heat dissipation.

A stabilizer is added to the present NMM, preferably in the form of an azeotrope with water, and a solution of H 2 O 4, preferably 35%, is added for 2-5 hours at the reaction temperature, and then a further 2.5 hours are allowed to react. up to 5 hours. Unreacted NMM is separated by vacuum rectification as an azeotrope with water.

Mostly in commercial solution of n ₂ 0 ₂ added combination of one or more stabilizers. The concentration of the stabilizer in commercial hydrogen peroxide at 35 wt. H ₂ 0 ₂ tends to be 100 to 200 ppm, which is not sufficient to suppress the formation of NOMOR below 100 ppb in the final NMMO solution. Based on the NMM employed, it is only 0.005 to 0.01% by weight with a H2O2 / NMM molar ratio = 0.6.

stabilizer.

The peroxide stabilizer is added to the present NMM, but can also be added to the H ₂ O ₂ solution, which however gives less effect. Therefore, the stabilizer contained in commercial peroxide reduces NOMOR formation relatively little. '

Of the three stabilizers mentioned, sodium ethylenediaminetetraacetate has the best properties, which not only radically limits the formation of NOMOR. but at the same time it provides an almost colorless NMMO solution.

When using a state with a concentration according to the invention, the final NMMO solution has a white tin hydroxide opalescence. However, the solution is λ ť A also colorless. Therefore, it is preferred to use a combination of stabilizers, e.g. % sodium ethylenediaminetetraacetate and 10 wt. sodium stearate.

It has been found that the NOMOR content of the oxide increases with increasing H2O2 / NMM molar ratio and it is therefore recommended to work with a ratio of 0.4 to 0.7. This knowledge can be used also when working with the addition of stabilizer, which allows to reduce the concentration of stabilizer. However, the effect of the stabilizer on suppressing NOMOR formation is so strong that it allows the oxidation of NMM with a molar ratio of up to 0.9. The higher the molar ratio, the higher the stabilizer concentration must be within the range of the invention.

Example 1.

Four comparative experiments on the oxidation of azeotropic NMM-water mixture (73 wt% NMM) with unstabilized 30% hydrogen peroxide and one trial with standardly stabilized 35% peroxide were performed. Solution containing 35 wt. H2O2 was stabilized at the manufacturer by sodium pyrophosphate decahydrate at a concentration of 150 ppm and 3 ppm sodium stearate.

Into a 1 L sulfonation flask equipped with a stirrer and placed in a thermostat, 400 g of NMM azeotrope containing 0.01 wt. morpholine. In experiments with individual stabilizers, 0.1 g of stabilizer was added to the azeotrope. At 65, a solution of H2O2 was uniformly fed for 3 hours with a H2O2 / NMM molar ratio of 0.6.

After the peroxide was introduced, the mixture was stirred at the reaction temperature for 3 hours while the peroxide concentration dropped to about 50 ppm. The non-reactive NMM was then distilled off under vacuum using an 8 theoretical plate efficiency column and

solution NMMO thickened to 60 + 1 wt. Experiment results summarizes these- bulka. č.pok. stabilizer peroxide NOMOR content coloring PPb NMMO 49 none 30%, nestab. 292 yellow-orange.

50 51 52 53 Na ₄ P ₂ 0 ₇ .10H ₂ 0 Na ₂ Sn (0H) ₆ EDTA none ti 35%, stabil. 19 Dec <10 <10 200 yellowish colorless opalescence colorless yellow Example

The NMM-water azeotropic mixture was oxidized with a commercial stabilized solution of H 2 O? (pyrophosphate + stearate) at 65 θθ with a molar ratio of H ₂ O ₂ / NMM = 0.9. 0.04 wt.% Was added to the present aZeotrope. sodium ethylenediaminetetraacetate (dihydrate) calculated on NMM. Peroxide was dosed for 3.5 hours, the reaction time was 5 hours. After the unreacted NMM was distilled off, a colorless 60% NMMO solution containing 20 ppb NOMOR was obtained.

Example 3.

Azeotropic -mixture -NMM-water. .byla. oxidized at 65 ° C commercially stabilized 35% H ₂ O ₂ at a H ₂ O ₂ / NMM molar ratio of 0.6. 0.017 wt.% Was added to the present azeotrope. EDTA (dihydrate) and 0.006% sodium stearate. The peroxide was metered in for 3 hours and then the reaction mixture was stirred for another three hours at the reaction temperature. After the unreacted NMM was distilled off under vacuum, a colorless solution of 60% by weight was obtained. NMMO containing 10 ppb NOMOR.

Industrial applicability

The invention is applicable to the production of low nitrosomorpholine-containing N-methylmorpholine oxide which is used for the preparation of cellulose fibers. ~ ““ “..................

Claims (2)

Patent claims A process for the preparation of low-nitrosomorpholine N-methylmorpholine oxide solutions by oxidizing N-methylmorpholine with an aqueous hydrogen peroxide solution at a temperature of 60 to 75 with a molar ratio H 2 O 2 / amine = 0.5 to 0.9, characterized in that hydrogen peroxide is treated with N-methylmorpholine containing at least one of the three hydrogen peroxide stabilizers consisting of sodium pyrophosphate, sodium ethylenediaminetetraacetate, sodium stearate in a total concentration of 0.01 to 0.05 wt. based on the amine employed and the conventional commercial form of added stabilizers, including crystalline water. 2. A process comprising treating hydrogen peroxide with Nmethylmorpholine in the form of an azeotrope with water.