GB2218986A

GB2218986A - Preparation of 3-nitro-1,2,4-triazol-5-one

Info

Publication number: GB2218986A
Application number: GB8911095A
Authority: GB
Inventors: Eugene Francis Rothgery
Original assignee: Olin Corp
Current assignee: Olin Corp
Priority date: 1988-05-27
Filing date: 1989-05-15
Publication date: 1989-11-29
Anticipated expiration: 2009-05-15
Also published as: FR2631962A1; DE3917228A1; GB2218986B; DE3917228C2; FR2631962B1; GB8911095D0

Description

/., 1 1 W 1 1 2218986 C-9860 PROCESS FOR MAKING

3-NITRO-1r2#4-TRIAZOL-5-ONE

Field of the Invention

5- This invention relates to.a novel process for the production of 3-nitro- lt2p4-triazol-5-one ('NTOw) from 1,2,4,-triazol-5-one (wTOw). NTO is a high energy material characterized by low vulnerability to reaction caused by unplanned stimuli.

Background of the Invention

Up until recent years, high energy explosives and propellants such as RDX, HMX, and TNT were considered adequate for weaponry and rocketry applications. However, during the course of the last decader the problem of unwanted detonation of these high energy explosives and propellants has become of increasing concern to the military.

Thus, the military has had to turn to other. less sensitive materialst such as NTO, to provide a greater margin of safety against reaction to unplanned stimuli. NTO exhibits excellent physical properties, including a desired combination of high energy when detonated and relatively low sensitivity to unplanned detonation, making it a current candidate of choice for propellant and explosive applications. Background information on NTO is provided in a technical article by K. Y. Lee and M. D. Coburn entitled w3- Nitro-1,2,4Triazol-5-One, A Less Sensitive Explosive", Los Alamos National Laboratory (LA-10302-MS, Issued February, 1985).

There are several known procedures for making NTO involving the nitration of 1.2,4-triazol-5-one (TO). By way of illustration, the above cited Lee and Coburn article discloses the nitration of TO by a procedure involving adding solid TO to a mixture containing roughly 60 volume percent of 90 percent nitric acid and 40 volume percent of water. The reaction is effected at the boiling point of the mixture, providing a substantial exotherm. Moreover, it has been found by the present inventor that, when nitrating solid TO at these temperatures, the problem of frothing of the reaction mixture is frequently encountered. This frothing is unacceptable from a process engineering standpoint. In addition, the use of solid TO can lead to the formation of hot spotsw at the solid/liquid interface, causing increased by-product formation and reduced yield of the desired NTO.

As another illustration, European patent application 210,811, published on February 4, 1987, discloses a process which involves reacting TO with 98 percent nitric acid at relatively low temperatures and with relatively long reaction times (presumably to avoid a large exotherm and the associated frothing problem).

Specifically, TO is adged to the 98 percent nitric acid during an addition time of two hours.at 5 0 C to 100c, followed by a three hour holding period at ambient temperatures, followed by quenching with water at 0 0 C and holding for 12 hours. This process is clearly very time-consuming. In addition, 98 percent nitric acid is a c 1 a k relatively expensive starting-material that is sometimes scarce as a commodity chemical.

Based on the above illustrations, it is clear that there are problems associated with conventional processes for nitrating TO to produce NTO. Accordingly, a new process for effecting this nitration, that does not involve frothing of the reaction mixture and does not require the use of 98 percent nitric acid, would be highly desired by the militaryF par'ticularly the propellant and explosives communities. Heretofore, such a process was not known to the knowledge of the present inventor.

Summary of the Invention

In one aspect. the present invention relates to a process for making 3-nitro-lf2p4-triazol-5-one from aqueous 1,2,4- triazol-5-one which comprises reacting a reaction mixture of concentrated nitric acid and aqueous 1r2r4-triazol-5-one at a reaction temperature of between about 50 0 C and about 100 0 C for a reaction time of at least about one hour, said reaction mixture containing an amount of water of between about 20 and about 50 weight percentr based upon the total weight of the reaction mixture.

In another aspecti the present invention relates to a process for making 3-nitro-1,2,4-triazol5-one from aqueous 1, 2,4-triazol-5-one in high yield which comprises the steps of:

. (a) reacting in a reactor a reaction mixture of concentrated nitric acid and aqueous 1,2,4-triazol- 5-one at a reaction temperature of between about 500C and about 100 0 C for a reaction time of at least about one hour to provide 3-nitro-1,2,4- triazol-5-one and spent nitric acid, 4 1 (b) separating said 3-nitro-li2i4-triazol5-one from said spent nitric acid, (c) mixing said spent nitric acid with 1,2,,4-triazol-5-one to form a spent nitric acid/1,2p45 triazol-5-one solutiont (d) adding said spent nitric acid/1,2,4triazol-5-one solution to said reactor and adding sufficient concentrated nitric acid to replenish the reaction mixture, and (e) repeating at least said steps (a) and (b) at least once.

Detailed Description of the Invention

In accordance with the process of the present invention, TO is employed as a starting material. The TO can be prepared by any known procedure, such as, for example, (I) the reaction of ethyl ethoxymethylene carbamate with hydrazine, (II) the reaction of carbohydrazide with ethyl orthoformate, (III) the decarboxylation of 3-hydroxy-1,2,4-triazol-B-carboxylic acid or (IV) the reaction of 3-chloro-112,4-triazol with caustic. A particularly useful method for producing TO involves the reaction of semicarbazide hydrochloride or free base semicarbazide with formic acid.

The process for producing NTO from aqueous TO and 90 percent nitric acid is suitably effected at a reaction temperature of between about 50 0 C and about 1000Cp preferably between about 700C and about 800C. Generally. the reaction time employed is at least about one hourr preferably between about one hour and about five hours. The reaction pressure is preferably atmospheric, although superatmospheric pressure can be employed if desired.

i Before beginning the process of the invention, solid TO is typically dissolved in an amount of water (preferably hot water, more preferably water heated to between about 50 0 C and about 80OC) sufficient to solubilize or finely disperse the solid and water TO to make this solution or dispersion. Generallyi the amount of water utilized for this purpose is between about 50 and about 85 weight percent (preferably between about 50 and about 70 weight percent) based upon the amount of TO and water used to make this solution or dispersion. Additional water is provided to the reaction mixture by the 90 percent nitric acid reactant. In total, the amount of water employed in the reaction mixture is generally between about 20 and about 50, preferably between about 30 and about 40. weight percent based upon the weight of the reaction mixture.

The ratio of concentrated nitric acid to TO in the reaction mixture can vary over a wide range. Generally, sufficient nitric acid is provided in the reaction mixture to insure that the desired nitration reaction takes place. Preferably. the weight ratio of nitric acid to TO is between about 10:1 and about 1:10. more preferably between about 10:1 and-about 5:1.

The process of the present invention lends itself to a recycling operation. As part of this processr it is preferred that the spent nitric acid be recycled back into the mixing vessel wherein the next solid TO charge is dissolved in it. The spent nitric acid is thus used to replace water that would otherwise be employed as a solvent for the TO reactant. The recyC'iing of spent nitric acid is particularly advantageous since the product NTO dissolved therein tends to prevent further NTO from dissolving in the liquid reaction mixture. Thus. the recycling of spent nitric acid has the effect of enhancing product yield in 1 a this process. Note that the spent nitric acid is easily separated from the solid NTO product in step (b) above by filtration.

As used herein. the term concentrated nitric acid' is intended to designate an aqueous nitric acid mixture having an acid concentration of between about 80 weight percent and about 95 weight percent (preferably about 90 weight percent) of acid based upon the total weight of acid plus water in the aqueous acid mixture. The term spent acidw designates a used nitric acid mixture containing water plus dissolved NTO plus. optionally, minor amounts of dissolved reaction by-products. The spent acid is produced after at least one cycle of the process of the present invention.

The following examples are intended to illustrate, but in no way limit the scope of. the present invention.

v 1 el 1, 1 1 ll EXAMPLE 1

Preparation of NTO Prom Aqueous NTO and 90% Nitric Acid Twenty ml of 90 percent nitric acid was placed in a 50 ml flask and heated to 45 0 C. l#2j4-Triazol 5-one (5 9, 0.059 mole) was dissolved in 12 ml of hot water having a temperature of about 800C. The resulting solution was added to the acid through a long-stem funnel having its outlet below the acid surface. upon addition of the solution, the acid mixture exothermed to a temperature of 800C. The remainder of the solution was added at a rate which maintained the temperature at about 80 0 C due to the exotherm. The addition required about eight minutes. As the reaction progressed,, the solution became light yellow and solids began to form and rise to the surface of the reaction mixture. The temperature of the reaction mixture was maintained at 80 0 C for one hour, then the mixture was cooled to 30 0 C and filtered to remove the solids from the filtrate. The solids were washed with a small amount of ice water and dryed in a vacuum to give 4.3 g of product melting at 267 0- 269 0 C# amounting to a 56 weight percent yield of NTO based upon the reactant.

EXAMPLE 2

1 Preparation of NTO Using Recycle of Spent Acid From EXAMPLE 1 in Order to Increase NTO Yield Five grams of TO was dissolved in 25 9 of the dilute acid filtrate (i.e. the 'spent acid') from EXAMPLE 1 above. This required heating the mixture to 50 0 C. To the resulting solution was added 20 ml of 90 percent 30 nitric acid at a temperature of 45 0 C. The mixture exothermed slowly to 70 0 C. The addition was made at a rate to maintain the temperature due to the exotherm at 65 0- 70 0 C. The mixture was then heated to 80 0 C and held for one hour at that temperaturei and then cooled to 5 20 0 C,, filtered# washed with ice water and dried. Approximately 7.1 9 of product having a melting point of 2670-271 0 C was obtained amounting to a 92.5 weight percent yield of NTO based upon the TO reactant.

EXAMPLE 3

Preparation of NTO Using Recycle of Spent Acid Prom EXAMPLE 2 The procedure of EXAMPLE 2 was repeated, except this time the spent acid utilized as the TO solvent was the dilute acid filtrate from EXAMPLE 2. The resulting product amounted to 5.9 g of material melting at 2660-2690C.

The product of the above three examples were combined and recrystallized from a small amount of boiling water. The final product melted at 267 0268 0 C and weighed 16.3 g, thus prbviding a 71 weight percent overall yield of NTO.

Analysis of the product provided the following results:

Analysis for C HN 0 2 4 3 Calculated C, 18.57; H, 1.54 Found C, 18.41; H, 1.53 These numbers are weight percents based upon the total C 2 HN 4 0 3 Differential Scanning Calorimetry (DSC) product testing showed an exotherm onset upon heating of the product at a rate of 10 0 C/min at 269.50C.

-1 1 1 9

Claims

CLAIMS:

1. A process for making 3-nitro-1,2,4-triazol-5one from aqueous 1,2,4triazol-5-one which comprises reacting a reaction mixture of concentrated nitric acid and aqueous 1,2,3-triazol-5-one at a reaction temperature of between about 50t and about 100t for a reaction time of at least about one hour.

2. A process for making 3-nitro-1,2,4-triazol-5one from aqueous 1,2,4triazol-5-one in high yield which comprises the steps of:

(a) reacting in a reactor a reaction mixture of concentrated nitric acid and aqueous 1,2,4-triazol-5-one at a reaction temperature of between about 500C and about 100t for a reaction time of at least about one hour to provide 3-nitro-1,2,4-triazol-5-one and spent nitric acid, (b) separating said 3nitro-1,2,4-triazol-5-one from said spent nitric acid, (c) mixing said spent nitric acid with 1,2,4triazol-5-one to form a spent nitric acid/1 2,4-triazol5-one solution, (d) adding said spent nitric acid/1 2,4-triazol-5one solution to said reactor and adding sufficient corcentrated nitric acid to replenish the reaction mixture, and (e) repeating at least said steps (a) and (b) at least once.

3. The process of claim 1 or claim 2 wherein said reaction mixture has a total water content of between about 20 and about 50 weight percent based upon the total weight of the reaction mixture.

4. The process of claim 1 or claim 2 wherein said reaction time is no greater than about 5 hours.

5. The process of claim 1 or claim 2 wherein said concentrated nitric acid has an acid concentration of about 90 weight percent based upon the total weight of water and acid therein.

6. The process of claim 1 or claim 2 wherein said aqueous 1,2,4-triazol-5one is prepared by dissolving solid, 1,2,4-triazol-5-one in water to provide a solution. of aqueous 1,2,4-triazol-5-one.

7. The process of claim 6 wherein said solution comprises between about 50 and about 85 weight percent 1 z v ( t v - 11 of water based upon the weight of the solution.

8. The process of claim 6 wherein said solution comprises between about 50 and about 70 weight percent of water based upon the weight of the solution.

9. The process of claim 1 or claim 2 which is carried out at atmospheric pressure.

10. The process of claim 1 or claim 2 which is carried out at a reaction temperature of between about 70t and about 80t.

11. The process of claim or claim 2 wherein step (b) is effected using filtration.

Published 19M atThe Patent Office, State House, 66/71 High Holborn, London WC1R 4TP. Further copiesmaybe obtained from The Patent Office. Sales Branch, St Mary Cray, Orpington, Kent BR5 3RI). Printed by Multiplex techniques Rd, St Maxy Cray, Kent, Con- 1/87 v