FLOW SYNTHESIS OF RDX

Abstract

The invention relates to a method for the flow synthesis manufacture of RDX, comprising the steps of preparing input flow reagent A, comprising hexamine dissolved in nitric acid with a concentration less than 92%, preparing input flow reagent B comprising 99% concentration nitric acid, causing the input flow reagents A and B to enter a flow reactor at a flow rate, so as to cause a total nitric acid concentration of greater than 93%, in said flow reactor, cooling the reaction chamber to less than 30 C., causing the output mixed flow to be quenched.

Claims

1. A method for the flow synthesis manufacture of RDX, the method comprising: preparing input flow reagent A, comprising hexamine dissolved in nitric acid with a concentration less than 92%; preparing input flow reagent B, comprising greater than 95% concentration nitric acid; causing the input flow reagents A and B to enter a reaction chamber of a flow reactor at a flow rate, so as to cause a total nitric acid concentration of greater than 93%, in said flow reactor; cooling the reaction chamber to less than 30 C.; and causing an output mixed flow to be quenched, to cause precipitation of RDX.

2. The method according to claim 1, wherein the hexamine is dissolved in nitric acid with a concentration in the range of from 88% to 90%.

3. The method according to claim 1, wherein the hexamine is dissolved in nitric acid to achieve a saturated solution.

4. The method according to claim 1, wherein the input flow reagent B is 99% concentration nitric acid.

5. The method according to claim 1, wherein the total nitric acid concentration is in the range of 90-99%, in said flow reactor.

6. The method according to claim 1, wherein the flow rate ratio of input flow reagent A to input flow reagent B (A:B) is greater than 1:3 (A:B).

7. The method according to claim 1, wherein the temperature in said flow reactor is in the range of from 20 C. to 27 C.

8. The method according to claim 1, wherein the nitric acid in input flow reagent B further comprises oleum or NaNO.sub.2.

9. The method according to claim 1, wherein the quench is caused by mixing the output mixed flow and a quenching agent.

10. The method according to claim 9, wherein the quenching agent is an aqueous solution, so as to cause precipitation of RDX.

11. The method according to claim 9, wherein the quenching agent is cooled below 10 C.

12. Apparatus for carrying out the process according to claim 1, wherein the apparatus is configured for explosive compatibility.

13. A method comprising the use of flow synthesis for providing explosive material from hexamine.

14. A method for the flow synthesis manufacture of RDX, the method comprising: preparing input flow reagent A, comprising hexamine dissolved in nitric acid with a concentration less than 92%; preparing input flow reagent B, comprising a nitration reagent; causing the input flow reagents A and B to enter a reaction chamber of a flow reactor at a flow rate, so as to cause nitration of RDX in said flow reactor; cooling the reaction chamber to less than 30 C.; and causing an output mixed flow to be quenched, to allow precipitation of RDX.

15. The method according to claim 14, wherein the nitration reagent is selected from at least 70% concentration nitric acid and NaNO.sub.2, or containing only 99% concentration nitric acid.

16. The method according to claim 14, wherein causing the output mixed flow to be quenched includes causing the output mixed flow to come into contact with an aqueous solution.

17. The method according to claim 14, wherein the nitration reagent comprises at least 70% concentration nitric acid and NaNO.sub.2.

18. The method according to claim 14, wherein the nitration reagent comprises 99% concentration nitric acid.

19. The method according to claim 1, wherein the total nitric acid concentration is in the range of 93% to 95%, in said flow reactor.

20. The method according to claim 1, wherein the total nitric acid concentration is in the range of 93% to 99%, in said flow reactor.

Description

EXPERIMENTAL

[0037] ##STR00001##

[0038] The general reaction is shown above, where the input flow reagent A comprises hexamine dissolved in nitric acid, and input flow reagent B comprises the nitrating agent, which may be higher concentration of nitric acid (than input flow reagent A), and/or a further nitrating agent, such as a metal nitrite, such as NaNO.sub.2. The input flow reagent A and input flow reagent B are caused to react in the flow reactor to furnish the product RDX.

[0039] RDX synthesis using a flow reactor poses more challenging design issues than simply pumping solutions from well-known and quantified batch chemistry. This is mainly due to the fact that the starting material hexamine is solid, and RDX can potentially precipitate out of solution during the reaction. Precipitation of the RDX during the transition through the flow reactor can happen as the acid concentration drops and water content increases, thereby leading to potential blockages in the flow reactor, this could lead to catastrophic events, and so the nitric acid concentration in the flow chemistry.

[0040] Before starting the experiment the reactor was prepared by flushing the system with methanol followed by water. Both input systems were then filled with 70% HNO.sub.3 which was passed through the reactor in order to fully prime the system.

Experiment 1

[0041] Syringe A: 0.1010 g hexamine in 5 mL 99% HNO.sub.3 [0042] Syringe B: 0.1079 g NaNO.sub.2 in 10 mL 70% HNO.sub.3

##STR00002##

[0043] Initial work focused on trying to translate the batch based synthesis directly to the flow reactor. The experiment involved making pre-mixed solutions of hexamine and 99% HNO.sub.3 (solution A) and NaNO.sub.2 in 70% HNO.sub.3 (solution B).

[0044] A sample of the initial hexamine stock solution was analysed using .sup.1H NMR. It was evident from this that the bulk of the reaction had already been completed in the initial hexamine HNO.sub.3 solution before it was passed through the reactor. Therefore, the experimental method was adapted so that the reaction occurs within flow reactor and not the initial solutions.

Experiment 2Saturated Hexamine Test

[0045] Syringe A: Saturated hexamine in 70% HNO.sub.3 (roughly 1 g in 5 mL). [0046] Syringe B: 99% HNO.sub.3.

[0047] It is desirable to use nitric acid as the only nitrating agent, rather than to introduce further reagents, such as for example NaNO.sub.2. Experiment 1 was repeated without the NaNO.sub.2, and using 99% concentration of nitric acid in syringe B to act as the sole nitrating agent.

[0048] No precipitate was obtained when the solution from the reactor was collected into water. It can be concluded that the overall acid concentration for the reaction is too low to produce RDX in sufficient quantities therefore focusing on the overall acid concentration of the reaction was investigated.

Experiment 3 Higher Acid Concentration Test

[0049] Syringe A: Saturated hexamine in 90% HNO.sub.3 (roughly 1 g in 5 mL). [0050] Syringe B: 99% HNO.sub.3.

[0051] The concentration of the nitric acid in syringe A was increased. 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 4 Addition of Oleum

[0052] Syringe A: 0.5 g hexamine dissolved in 2.5 mL 90% HNO.sub.3. Solution cooled during hexamine addition. [0053] Syringe B: 0.95 mL 99% HNO.sub.3+0.05 mL oleum.

[0054] 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 5 Increased Oleum Addition

[0055] Syringe A: 0.5 g hexamine dissolved in 2.5 mL 90% HNO.sub.3. Solution cooled during hexamine addition. [0056] Syringe B: 0.9 mL 99% HNO.sub.3+0.1 mL oleum.

[0057] 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.

[0058] 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.

[0059] 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.