SYNTHESIZING AN ORGANIC HIGH EXPLOSIVE IN A FLOW REACTOR

Abstract

A method of synthesising an organic high explosive includes the steps of i) providing a first solution A, ii) providing a second solution B, wherein the admixture of solution A and solution B are selected such that they are capable upon formation of the admixture of reacting together to provide an organic high explosive, and iii) causing the solution A and B to be mixed and passed through a flow reactor to create an admixture, wherein the flow reactor includes a pipe, wherein the internal diameter of the pipe is selected such that it is less than the critical diameter of the organic high explosive, thereby preventing detonation of the formed organic high explosive in said flow reactor.

Claims

1. A method of synthesizing an organic high explosive in a flow reactor including a pipe, the method comprising: combining a solution A comprising a nitrating agent with a solution B comprising an explosive precursor reagent to produce an admixture, wherein solution A and solution B are selected such that they are capable upon formation of the admixture of reacting together to provide the organic high explosive; determining a critical diameter of the organic high explosive; selecting an internal diameter of the pipe such that it is less than the critical diameter of the organic high explosive, thereby preventing detonation of the formed organic high explosive in said flow reactor; and causing the solution A and B to be mixed and passed through the flow reactor to create the admixture to provide the organic high explosive.

2. The method according to claim 1, wherein the nitrating agent comprises nitric acid and/or nitrites.

3. The method according to claim 1, wherein the organic high explosive is a nitramine.

4. The method according to claim 3, wherein the nitramine is RDX or HMX.

5. The method according to claim 1, wherein the explosive precursor reagent is selected from at least one of: cycloamine, Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (TAT), 1,3,5-triacetyl-1,3,5-triazacyclohexanes (TRAT), 1,5-Dinitroendomethylene-1,3,5,7-tetraazacyclooctane (DPT), and hexamethylenetetramine.

6. The method according to claim 1, wherein solution A and/or solution B and/or a solution C mixed to create the admixture further comprises catalysts, strong acids, de-hydrating agents, and/or acid anhydrides.

7. The method according to claim 1, wherein the flow reactor is temperature controlled.

8. The method according to claim 1, wherein after the admixture has transitioned through the flow reactor, a solution D is added to work up the reacted admixture to provide a precipitate of said organic high explosive or a salt thereof.

9. The method according to claim 8 wherein solution D may comprise cooled water.

10. The method according to claim 1, wherein the internal diameter of the pipe is less than 500 microns.

11. The method according to claim 1, wherein the organic high explosive is collected remotely from at least stored solutions A and/or B, such as to reduce the hazard of an event.

12. The method according to claim 11, wherein the collected remotely organic high explosive is behind a blast wall or within an explosive magazine.

13. An apparatus for carrying out the method of claim 1, comprising a plurality of flow reactors in parallel, each of said flow reactors comprising a pipe, wherein the internal diameter of the pipe is selected such that it is less than the critical diameter of the organic high explosive.

14. The apparatus of claim 13, wherein the internal diameter is less than 500 microns.

15. The method according to claim 2, wherein the organic high explosive is nitramine.

16. The method according to claim 15, wherein the nitramine is RDX or HMX.

17. The method according to claim 3, wherein the explosive precursor reagent is selected from: cycloamine, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (TAT), 1,3,5-triacetyl-1,3,5-triazacyclohexanes (TRAT), 1,5-dinitroendomethylene-1,3,5,7-tetraazacyclooctane (DPT), and/or hexamethylenetetramine.

18. The method according to claim 17, wherein solution A and/or solution B and/or the admixture further comprises catalysts, strong acids, de-hydrating agents, and/or acid anhydrides.

19. The method according to claim 17, wherein after the admixture has transitioned through the flow reactor, a solution D is added to work up the reacted admixture to provide a precipitate of said organic high explosive or a salt thereof.

20. The method according to claim 19, comprising collecting the organic high explosive remotely from stored solutions A and/or B and/or C, such as to reduce the hazard of an event.

Description

EXPERIMENT 1

[0055] Syringe A: Saturated hexamine in 90% HNO.sub.3 (roughly 1 g in 5 mL). [0056] Syringe B: 99% HNO.sub.3. [0057] Flow reactor used: 3222 Labtrix

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[0058] The concentration of the nitric acid in syringe A was 90% conc. The flow rate was set at 1:3 (A:B), however limited product formed. The flow rate of syringe B, 99% HNO.sub.3 feed was increased so that the A:B flow ratio was 1:9. When the sample was collected into water the solution became opaque indicating that RDX had been produced.

EXPERIMENT 2 ADDITION OF OLEUM

[0059] Syringe A: 0.5 g hexamine dissolved in 2.5 mL 90% HNO.sub.3. Solution cooled during hexamine addition. [0060] Syringe B: 0.95 mL 99% HNO.sub.3+0.05 mL oleum.

[0061] A series of experiments were carried out aimed at monitoring the influence of oleum on RDX formation. Experiments produced opaque solutions when collected into water indicative of RDX formation. The .sup.1H NMR spectrum showed that RDX exists in solution prior to precipitation using water as the quenching agent.

EXPERIMENT 3 INCREASED OLEUM ADDITION

[0062] Syringe A: 0.5 g hexamine dissolved in 2.5 mL 90% HNO.sub.3. Solution cooled during hexamine addition. [0063] Syringe B: 0.9 mL 99% HNO.sub.3+0.1 mL oleum.

[0064] The increase of oleum by 100%, led to formation of RDX precipitate when collected onto ice. Part of the solution before mixing with ice was collected into d.sup.6-DMSO, the .sup.1H NMR spectrum indicated the formation of RDX.

[0065] The use of further acids such as oleum, helps to keep that acid concentration in the reactor at a high level, and may assist in dehydration of the reaction. The use of nitration species such as NaNO.sub.2, can allow the use of lower total nitric acid concentrations.

[0066] It was found that low acidity in the reactor caused RDX to precipitate from the solution. It is essential to monitor the flow reactor paths for solidified product. Further, whilst it is desirable to increase the acidity of the nitric acid that comprises the hexamine, if the concentration is too high product starts to form, before mixing has commenced, again leading to likelihood of RDX product blocking the flow reactor. Preferably the hexamine is dissolved in the nitric acid, before use, and is not stored long term as a stock solution.

HMX Example

[0067] TAT can be readily synthesised from hexamine via DAPT as an intermediate. The main advantage of going through this route is that an 8-membered ring is formed therefore eliminating the possibility of forming RDX as a biproduct. The TAT can be directly converted to HMX, using nitration in a flow synthesis arrangement to control the rate of production of explosive material.

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EXPERIMENTAL 1

[0068] Line Asolution of 100 mg TAT, 1000 mg P.sub.2O.sub.5 and 2 mL of 99% HNO.sub.3 were premixed in a single solution and passed through a Labtrix reactor. The preferred reaction time of 120 seconds through the flow synthesis reactor provided sufficient time for nitration to occur. The flow synthesis was performed at a temperature greater than room temperature, it was found that a temperature of 75 C. provided a temperature which allowed the reaction to proceed, but not sufficient to cause an unwanted explosive event. HMX was isolated, without any RDX contamination being present.

EXPERIMENT 2 A SCALED UP PROTRIX REACTOR

[0069] Line A: 2.0061 g TAT and 20.0357 g of P.sub.2O.sub.5 were dissolved in 40 mL 99% HNO.sub.3 [0070] Line B was used as an emergency flush and was primed with 70% HNO.sub.3.

[0071] Line A and the Protrix were initially primed with 70% HNO.sub.3 followed by 99% HNO.sub.3. The reaction mixture was prepared in stages. Initially P.sub.2O.sub.5 is slowly dissolved into a stirred solution of 99% HNO.sub.3. This solution was kept in an ice bath. This resulted in an opaque-yellow solution. The addition of TAT to this solution reduced the opacity of the solution however, the reaction mix remained opaque.

[0072] Line A was then primed with the reaction mixture.

TABLE-US-00001 TEMP TIME FLOW EXP ( C.) (S) A (ML) P (BAR) OBSERVATION 0168 75 120 1.66 1.1 Collected for 12 minutes into ice.

[0073] The solution from the Protrix was left overnight, which resulted in the formation of crystals. These were isolated, washed with water followed by acetone and then analysed using NMR spectroscopy. The .sup.1H NMR spectrum of experiment 0168 shows that there are multiple species present in the sample. Some of these peaks correspond to unreacted TAT and partially nitrated TAT. These impurities are also observed in the industrial batch synthesis of HMX from TAT and can be removed by boiling the material in acetone followed by recrystallisation. In the 1H NMR spectrum, a peak at 6.02 ppm is characteristic of HMX.