Process for the preparation of N-alkyl-nitratoethylnitramines

Abstract

The present invention relates to a continuous process for the preparation of N-alkyl-nitratoethylnitramines (e.g. NENA compounds, DINA).

Claims

1. A process for the preparation of a compound of the formula (I): ##STR00003## wherein R is an alkyl group having from 1 to 6 carbon atoms or a group of the formula CH.sub.2CH.sub.2ONO.sub.2, or of mixtures of two or more such compounds, which process comprises the reaction of a compound of the formula (II): ##STR00004## wherein R is an alkyl group having from 1 to 6 carbon atoms or a group of the formula CH.sub.2CH.sub.2OH, or the reaction of corresponding mixtures of two or more such compounds, with nitric acid and then with a mixture of at least one acid anhydride and a chloride-containing catalyst in a continuous process, characterised in that the reactions are carried out at a pressure of from 0.5 bar above atmospheric pressure up to a pressure of 80 bar above atmospheric pressure.

2. Process for the preparation of a compound of the formula (I): ##STR00005## wherein R is an alkyl group having from 1 to 6 carbon atoms or a group of the formula CH.sub.2CH.sub.2ONO.sub.2, or of mixtures of two or more such compounds, which process comprises the reaction of a compound of the formula (II): ##STR00006## wherein R is an alkyl group having from 1 to 6 carbon atoms or a group of the formula CH.sub.2CH.sub.2OH, or the reaction of corresponding mixtures of two or more such compounds, with nitric acid and then with a mixture of at least one acid anhydride and a chloride-containing catalyst in a continuous process, characterized in that the reactions are carried out at a pressure sufficient to prevent the formation of a gas phase within the reactor during the reactions.

3. The process according to claim 1, characterised in that after the reactions the reaction mixture is brought into contact with water or an aqueous alkaline solution.

4. The process according to claim 1, characterised in that R is a methyl, ethyl or butyl group or a group of the formula CH.sub.2CH.sub.2ONO.sub.2 and R is a methyl, ethyl or butyl group or a group of the formula CH.sub.2CH.sub.2OH.

5. The process according to claim 1, characterised in that the reactions are carried out in one or more continuous flow reactor(s).

6. The process according to claim 1, characterised in that the reactions are carried out in one or more tubular reactor(s).

7. The process according to claim 1, characterised in that the reactions are carried out in one or more microreactor(s).

8. The process according to claim 1, characterised in that the reactions are carried out at a pressure of from 0.5 bar above atmospheric pressure up to a pressure of 18 bar above atmospheric pressure.

9. The process according to claim 1, characterised in that the reaction with nitric acid is carried out at a temperature of from 20 C. to 30 C.

10. The process according to claim 1, characterised in that the reaction with a mixture of at least one acid anhydride and a chloride-containing catalyst is carried out at a temperature of from 20 C. to 60 C.

11. The process according to claim 1, characterised in that acetic anhydride is used as acid anhydride.

12. The process according to claim 1, characterised in that hydrogen chloride is used as chloride-containing catalyst.

13. The process according to claim 1, characterised in that the nitric acid used in the reaction is used with a concentration of from 75 to 96% in water.

14. The process according to claim 1, characterised in that a mixture of ethyl-NENA (R=ethyl) and methyl-NENA (R=methyl) is prepared.

15. The process according to claim 1, characterised in that a plurality of identical or different microreactors are connected one after the other in series.

16. The process according to claim 1, characterised in that the reaction between the compound of the formula (II) and nitric acid is carried out in a microreactor as a continuous process and the product from that microreactor is continuously transferred to a further microreactor, in which further microreactor at least one acid anhydride and the chloride-containing catalyst are added.

17. The process according to claim 8, characterised in that the reactions are carried out at a pressure of from 3 bar above atmospheric pressure up to a pressure of 12 bar above atmospheric pressure.

18. The process according to claim 9, characterised in that the reaction with nitric acid is carried out at a temperature range selected from 10 C. to 10 C. or 15 C. to 5 C.

19. The process according to claim 10, characterised in that the reaction with a mixture of at least one acid anhydride and a chloride-containing catalyst is carried out at a temperature range selected from 27 C. to 36 C. or 25 C. to 35 C.

20. The process according to claim 15, characterised in that at least three microreactors are connected in series.

Description

[0048] Preferably the first reaction between N-alkyl-ethanolamine and nitric acid is carried out in a microreactor (comprising at least one microreactor module) as a continuous process and the product from that microreactor is continuously transferred to a further microreactor (comprising at least one microreactor module), in which further microreactor acetic anhydride and the chloride-containing catalyst are added.

[0049] FIG. 1 shows a flow diagram of a preferred device for carrying out the process according to the invention.

[0050] A preferred embodiment of the process of the present invention is described in detail below. The compound of the formula (II) or the mixture thereof is referred to as amine below.

[0051] Nitric acid (65-100% in water, preferably 75-96% in water, especially preferably 80-90% in water) is pumped through a first microreactor (comprising at least one microreactor module 1) (flow rate: 10-50 ml/min, residence times of 0.1-1.1 min, preferably 0.4-0.7 min). The first microreactor serves for pre-cooling the acid to a temperature of from 20 C. to 20 C. (preferably from 10 C. to 10 C.).

[0052] In a second microreactor (comprising at least one microreactor module 2a and optionally one or more microreactor module(s) 2b), the acid thus cooled is brought to reaction with amine (concentration >50% in water, preferably >96%) with a constant flow of amine (3-20 g/min, preferably 5-15 g/min, residence time 0.1-0.7 min, preferably 0.2-0.5 min) at a temperature of from 20 C. to 20 C. (preferably from 10 C. to 10 C.).

[0053] The cooling of the nitric acid and the subsequent reaction is carried out at a pressure of from 0.5 bar above atmospheric pressure up to 18 bar above atmospheric pressure.

[0054] It is possible for more than one microreactor module 2a to be arranged in the second microreactor in order to distribute the metering of amine between a plurality of microreactor modules 2a. The metering can either be effected via individual metering pumps operating independently or via a pump and the corresponding number of metering valves.

[0055] The reaction mixture from the second microreactor is conducted into a next microreactor (comprising at least one microreactor module 3a and optionally one or more microreactor module(s) 3b) where it is mixed with acetic anhydride and the catalyst dissolved therein (preferred catalyst content for concentrated hydrochloric acid (>25%): 0.5-5.0% by volume, preferably 1-2% by volume; flow rate 40-120 g/min, preferably 55-95 g/min; residence time 0.1-1.1 min, preferably 0.3-0.8 min) and heated to from 20 C. to 40 C. (preferably from 27 C. to 36 C.) and brought to reaction.

[0056] In a fourth microreactor (comprising at least one microreactor module 4), the reaction solution can then be quenched with water or aqueous alkaline solution (preferably sodium hydroxide, sodium carbonate or sodium hydrogen carbonate solution in water; concentration 5-20% by weight) at from 0 C. to 20 C. and at from 0 to 18 bar and the crude product precipitated. The advantage of this variant lies in the better temperature control as well as in the quicker and more efficient mixing and quenching.

[0057] Alternatively the reaction mixture from the third microreactor can be quenched with water and the crude product precipitated outside the fluid channels (or reactant channels) at normal pressure, the crude product being obtained preferably in a yield of from 60 to >95 mol % based on the amine and with a purity (according to HPLC) of 92-100%.

[0058] In that case the reaction mixture from microreactor module 3b is quenched with water or dilute alkaline solution (for example carbonate solution) in a mixing chamber and the reaction interrupted, the temperature preferably being controlled to 5-20 C.

[0059] Unlike the first variant with the microreactor module 4, a larger amount of quenching medium can be supplied by means of a mixing chamber. It is also possible to operate at lower pressure. This improves droplet formation and facilitates outgassing of gases from the reaction or from the quenching that are bound in the solution, in this case especially when a carbonate solution is used.

[0060] The subsequent separation can be effected by means of cyclone separation, precipitation separation, membrane separation or other phase separation methods in order to separate the two resulting phases from one another.

[0061] The organic product phase from the separation can be washed by means of water or some other suitable washing medium (for example dilute alkaline solution or salt solutions) and separated by means of a second separating step (see first separation).

[0062] In addition to the adjustment of the flow rates, it is also possible for the residence time to be adjusted by modular lengthening of the fluid channels (or reactant channels) or installation of further microreactor modules.

EXAMPLES

[0063] Example 1: Synthesis of ethyl-NENA:

[0064] 87% nitric acid at a flow rate of 23 ml/min is cooled to 6 C. at a residence time of 28 sec and conveyed into the second microreactor where, at 6 C., 11.5 g/min of N-ethylethanolamine (EEA) are metered into the pre-cooled nitric acid. After a residence time of 30 sec, acetic anhydride with 1% by volume admixed hydrochloric acid (37% hydrochloric acid in water) is introduced into the resulting reaction mixture at a flow of 70 g/min. The mixture is maintained at 32 C. for a further 34 sec and quenched with an inflow of water of 155 g/min at 15 C. The crude product is obtained in a yield of 92 mol % (based on the amine) with a purity according to HPLC of 98%. The pressure in the entire reactor under these test conditions is between 4.5 and 11 bar, depending upon the measurement point.

[0065] Example 2: Synthesis of ethyl/methyl-NENA (42% ethyl-NENA, 58% methyl-NENA, MEN42):

[0066] 85% nitric acid at a flow rate of 30 ml/min is cooled to 6 C. at a residence time of 20 sec and conveyed into the second microreactor where, at 6 C., 9.5 g/min of N-methylethanolamine/N-ethylethanolamine (MEA/EEA: 60/40% by weight) are metered into the pre-cooled nitric acid. After a residence time of 15 sec, acetic anhydride with 1% by weight admixed zinc(II) chloride is introduced into the resulting reaction mixture at a flow of 85 g/min. The mixture is maintained at 32 C. for a further 29 sec and quenched with an inflow of water of 155 g/min at 15 C. over a period of 3 sec. The crude product is obtained in a yield of 90 mol % (based on the amines) with a purity according to HPLC of 98% and a ratio by weight of 42% ethyl-NENA to 58% methyl-NENA. The pressure in the entire reactor under these test conditions is between 4.5 and 12 bar, depending upon the measurement point.

[0067] Example 3: Synthesis of ethyl/methyl-NENA (52% ethyl-NENA, 48% methyl-NENA, MEN52):

[0068] 85% nitric acid at a flow rate of 30 ml/min is cooled to 6 C. at a residence time of 20 sec and conveyed into the second microreactor where, at 6 C., 10.0 g/min of N-methylethanolamine/N-ethylethanolamine (MEA/EEA: 50/50% by weight) are metered into the pre-cooled nitric acid. After a residence time of 15 sec, acetic anhydride with 1% by volume admixed hydrochloric acid (37% hydrochloric acid in water) is introduced into the resulting reaction mixture at a flow of 80 g/min. The mixture is maintained at 32 C. for a further 30 sec and quenched with an inflow of 8% sodium hydroxide solution, 150 g/min, at 20 C. for 3 sec. The crude product is obtained in a yield of 94 mol % (based on the amines) with a purity according to HPLC of 98.5% and a ratio by weight of 52% ethyl-NENA to 48% methyl-NENA. The pressure in the entire reactor under these test conditions is between 4.5 and 12.5 bar, depending upon the measurement point.

[0069] Alternatively, if dilute nitric acid is used, dilution of highly concentrated nitric acid (99-100% nitric acid) with water can be carried out upstream of the actual synthesis. This is described below:

[0070] Example 4: Synthesis of ethyl-NENA with integrated acid pre-mixing:

[0071] In the first microreactor, 99% nitric acid is cooled to 6 C. at a flow of 26 ml/min over a period of 24 sec. The cooled acid is then diluted with 6.0 ml of water at 6 C. over a period of 18 sec. The 87% nitric acid so mixed is then conditioned at 6 C. at a residence time of 19 sec and conveyed into the second microreactor where, at 6 C., 13 g/min of N-ethylethanolamine (EEA) are metered into the pre-cooled dilute nitric acid. After a residence time of 13 sec, acetic anhydride with 1% by volume admixed hydrochloric acid (37% hydrochloric acid in water) is introduced into the resulting reaction mixture at a flow of 80 g/min. The mixture is maintained at 33 C. for a further 29 sec and quenched with an inflow of water of 155 g/min at 20 C. over a period of 3 sec. The crude product is obtained in a yield of 90 mol % (based on the amine) with a purity according to HPLC of 97%. The pressure in the entire reactor under these test conditions is between 4.5 and 12.5 bar, depending upon the measurement point.

REFERENCE SIGNS

[0072] 1 Microreactor module of the first microreactor [0073] 2a Microreactor module of the second microreactor [0074] 2b Microreactor module of the second microreactor [0075] 3a Microreactor module of the third microreactor [0076] 3b Microreactor module of the third microreactor [0077] 4 Microreactor module of the fourth microreactor [0078] 5 Supply of nitric acid [0079] 6 Supply of amine [0080] 7 Supply of acetic anhydride and chloride-containing catalyst [0081] 8 Supply of water or aqueous alkaline solution (quenching solution) [0082] 9 Working-up/separation