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US-12617761-B2 - Process for producing hexahydro 1,3,5-trinitro-1,3,5-triazine and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine

US12617761B2US 12617761 B2US12617761 B2US 12617761B2US-12617761-B2

Abstract

Formation of methanoic acid, during the production of Hexahydro-1,3,5-trinitro-1,3,5-triazine and Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine via the legacy Bachmann nitrolysis process, is avoided when the workup is performed under neutralized, anhydrous conditions. The recovered anhydrous spent acid is used directly in successive nitrolysis batches with minimal processing. The yield and quality of the hexahydro-1,3,5-trinitro-1,3,5-triazine and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine thus produced is equal to the yield and quality of the legacy process hexahydro-1,3,5-trinitro-1,3,5-triazine and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine employing aqueous workup conditions.

Inventors

  • James E. Phillips

Assignees

  • James E. Phillips

Dates

Publication Date
20260505
Application Date
20230707

Claims (20)

  1. 1 . A methanoic acid free process for producing octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine, by nitrolysis of 1,3,5,7-tetraazatricyclo[3.3.1.1 3,7 ]decane, comprising: (a) while maintaining a temperature of about 30-80° C., concurrently introducing a stream of 1,3,5,7-tetraazatricyclo[3.3.1.1 3,7 ]decane in acetic acid (x moles 1,3,5,7-tetraazatricyclo[3.3.1.1 3,7 ]decane), a stream of ammonium nitrate in nitric acid, or sodium nitrate in nitric acid, and a stream of acetic anhydride into a starting heel, the starting heel containing a mixture comprising a majority of acetic acid with acetic anhydride, to produce a slurry, wherein the streams are in proportions greater than necessary for producing the octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine intermediates; (b) following the addition in step (a) and a pause of 0-20 minutes at 30-80° C., while maintaining a temperature of about 30-80° C., concurrently introducing a stream of ammonium nitrate in nitric acid, or sodium nitrate in nitric acid, and a stream of acetic anhydride into the slurry from step (a), to produce a slurry, wherein the streams are in proportions greater than necessary for producing the octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine intermediates; (c) following the addition in step (b) and a pause of 0-20 minutes at 30-80° C., while maintaining a temperature of about 30-80° C., concurrently introducing a stream of ammonium nitrate in nitric acid, or sodium nitrate in nitric acid, and a stream of acetic anhydride into the slurry from step (b), to produce a slurry, wherein the streams are in proportions greater than necessary for producing the octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine; (d) maintaining the resulting slurry from step (c) at about 30-80° C. for about 45 minutes to affect nitrolysis of the 1,3,5,7-tetraazatricyclo[3.3.1.1 3,7 ]decane to produce a slurry containing octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine and a spent acid mixture containing acetic acid, acetic anhydride, nitric acid, and ammonium nitrate; (e) adding ammonia or an ammonia source to the slurry of step (d) sufficient to neutralize the nitric acid; (f) quenching the neutralized slurry of step (e) with water to produce an anhydrous spent acid mixture containing about 0.0-20 wt % acetic anhydride; (g) separating the octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine and the ammonium nitrate from the anhydrous spent acid mixture of step (f); (h) stirring the octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine from step (g) in a 0.0-90 wt % nitric acid solution at reflux to destroy undesired linear nitramines to provide crude octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine; and (i) collecting the crude octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine from step (h) by filtration.
  2. 2 . The process of claim 1 comprising the further step of washing the octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine separated from step (g) with hot water to produce washed octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine prior to proceeding to step (h).
  3. 3 . The process of claim 1 comprising the further step (j) of washing the crude octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine from step (i) is washed with water.
  4. 4 . The process of claim 3 comprising the further step (k), or the further step (1) of recrystallizing the washed, or unwashed octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine from step (j) or from step (i) respectively, wherein the recrystallization is from a solvent selected from the group consisting of acetone, cyclohexanone, water, dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethyacetamide (DMAc), N-methylpyrrolidone (NMP), 2-Methylcyclohexanone, cyclohexyne, formamide, γ-butyrolactone, γ-valerolactone, δ-valerolactone, ε-caprolactone, and mixtures thereof.
  5. 5 . The process of claim 4 comprising the further step (1) of recrystallizing the washed or unwashed octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine from step (i) from a mixture of water and acetone.
  6. 6 . The process of claim 1 wherein the ammonia source of step (e) is ammonium acetate.
  7. 7 . The process of claim 1 wherein step (e) is performed by first cooling the slurry to about 20-60° C., or to about 25-55° C., or to about 45° C. prior to adding the ammonia or ammonia source.
  8. 8 . The process of claim 1 wherein in step (f) the mixture is subsequently cooled or warmed to about 20-90° C., or about 20-50° C., or to about 25° C. prior to filtration.
  9. 9 . The process of claim 1 wherein in step (a) the temperatures of one or more of step (a) and step (b) are independently maintained at about 40-75° C., or at about 44° C.
  10. 10 . The process of claim 1 wherein in step (f) the quenching of the neutralized slurry of step (e) with water is conducted to produce an anhydrous spent acid mixture containing about 0.0-10 wt %, or about 0.0-0.5 wt % acetic anhydride.
  11. 11 . The process of claim 1 wherein in step (h) the washed or unwashed octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine from step (g) is stirred in about 0-60 wt %, or about 0-40 wt %, or about 0-10 wt % nitric acid solution.
  12. 12 . The process of claim 1 , wherein at least a portion of the anhydrous spent acid mixture from step (e) is directly recycled.
  13. 13 . The process of claim 12 wherein a portion of the anhydrous spent acid mixture from step (e) is directly recycled via at least one of the following three means: (i) recycled to the heel, (ii) recycled to dissolve the 1,3,5,7-tetraazatricyclo[3.3.1.1 3,7 ]decane, and/or (iii) recycled through pre-distillation evaporators to provide acetic acid and a slurry of acetic acid, RDX, HMX, ammonium nitrate or sodium nitrate, and trace impurities.
  14. 14 . The process of claim 13 wherein the portion of the anhydrous spent acid mixture from step (g) that is directly recycled through pre-distillation evaporators is followed by conversion of the acetic acid obtained therefrom to acetic anhydride in a ketene furnace.
  15. 15 . The process of claim 13 wherein the slurry from pre-distillation evaporator is collected and recycled to the crude hexahydro-1,3,5-trinitro-1,3,5-triazine from step (g) from subsequent RDX batches.
  16. 16 . The process of claim 13 wherein the slurry from pre-distillation evaporator is collected and recycled to the crude octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine from step (g) from subsequent HMX batches.
  17. 17 . The process of claim 1 wherein the ammonium nitrate content in the 1,3,5,7-tetraazatricyclo[3.3.1.1 3,7 ]decane feed stream and/or the acetic acid in the heel are determined and the amount, in moles (y), is calculated, 0.0-0.50 equivalents, relative to (y), of 1,3,5,7-tetraazatricyclo[3.3.1.1 3,7 ]decane added to the heel prior the start of stage 1 while maintaining a temperature of 20-50° C., 0.0-1.0 equivalents, relative to (y), of nitric acid added to the heel prior the start of stage 1.
  18. 18 . The process of claim 1 , wherein the resultant aqueous filtrates from one or more of step (j) and step (k) are collected and recycled through pre-distillation evaporators followed by azeotropic distillation.
  19. 19 . The process of claim 1 , wherein while maintaining a temperature of about 20-45° C., to a standard starting heel, containing a mixture comprising a majority of acetic acid with acetic anhydride, are added 0.0-0.10× moles 1,3,5,7-tetraazatricyclo[3.3.1.1 3,7 ]decane, 0.0×-0.20× moles ammonium nitrate or sodium nitrate, and 0.0-0.20× moles nitric acid prior to commencing step (a).
  20. 20 . The process of claim 1 , wherein while maintaining a temperature of about 20-45° C., to a standard starting heel, containing a mixture comprising a majority of acetic acid with acetic anhydride, are added 0.10×-0.20× moles 1,3,5,7-tetraazatricyclo[3.3.1.1 3,7 ]decane, 0.20×-0.40× moles ammonium nitrate or sodium nitrate, and 0.20×-0.40× moles nitric acid prior to commencing step (a).

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation of International Patent Application No. PCT/US2022/012078, filed Jan. 12, 2022, which claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No. 63/136,931, filed Jan. 13, 2021, each of which are hereby incorporated by reference in their entirety herein. FIELD OF THE INVENTION The present invention provides improved nitrolysis processes for making the explosive compounds hexahydro-1,3,5-trinitro-1,3,5-triazine (“RDX”) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (“HMX”). These processes have the advantage of being substantially-free of methanoic acid (a.k.a formic acid), which is a highly-corrosive byproduct of conventional large-scale manufacturing processes. The present processes are achieved by a controlled quench of and without application of heat to the resultant product mixture to eliminate excess water while reducing residual levels of remaining acetic anhydride, and also by neutralizing excess nitric acid remaining in the resultant product mixture. In further aspects residual acetic anhydride is recovered for recycling back into the process. BACKGROUND Hexahydro-1,3,5-trinitro-1,3,5-triazine and Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine are high energy explosives produced on industrial scale by the Bachmann process, which is sometimes referred to as the legacy process. The Bachmann process involves the nitrolysis of 1,3,5,7-tetraazatricyclo[3.3.1.13,7]decane via a solution of nitric acid and ammonium nitrate in acetic acid in the presence of a dehydrating agent, acetic anhydride. The process is summarized in FIG. 1—Conventional Hexahydro-1,3,5-trinitro-1,3,5-triazine Flow Diagram and FIG. 2—Conventional Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine Flow Diagram. The reactor heel for the hexahydro-1,3,5-trinitro-1,3,5-triazine process contains acetic acid, ammonium nitrate, nitric acid and acetic anhydride. The reactor heel for octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine excludes ammonium nitrate and nitric acid. The reagents for the reaction are added concurrently via three feed streams; 1.) a solution of 1,3,5,7-tetraazatricyclo[3.3.1.13,7]decane in acetic acid, 2.) a solution of ammonium nitrate in nitric acid, and 3.) acetic anhydride. Upon complete addition of the feed streams, the resultant slurry is aged at a prescribed temperature for 45 minutes (hexahydro-1,3,5-trinitro-1,3,5-triazine: 65° C.; octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine: 44° C.) followed by quenching of the excess acetic anhydride with water to approximately 35 wt % water (20 wt % for octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine). The aqueous/acetic acid slurry is heated to 98-100° C. for a prescribed time (hexahydro-1,3,5-trinitro-1,3,5-triazine: 30 min.; octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine: 120 min.), followed by cooling and filtering. The crude product solids are dried and recrystallized. The aqueous spent acid is sent to evaporators to remove the nonvolatile components, such as the hexahydro-1,3,5-trinitro-1,3,5-triazine, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine, ammonium nitrate, remaining linear nitramines, various acetamides/formamides, various diamides/mixed formamides, and other products and biproducts. The resulting spent acid stream is then distilled to separate the water and methanoic acid from the spent acid stream to produce glacial acetic acid to complete the process cycle. A portion of the distilled glacial acetic acid is directed to ketene furnaces to regenerate the dehydrating agent acetic anhydride. The process requires the entire volume of glacial acetic acid be derived from the spent acetic acid recovered from the nitrolysis reactions. The inclusion of methanoic acid as a minor component in a water acetic acid mixture transforms a simple, economically viable distillation step into a more complicated, resource intensive process. If a distillation facility is not specifically designed to accommodate a feed stream of acetic acid and water with approximately 0.25-0.50 wt % methanoic acid, process difficulties are likely to arise. When such process problems have been encountered to date with an inadequate distillation design, the solutions to the problem have resulted in dramatically increased energy usage, reduced glacial acetic acid output and rapid corrosion of the distillation columns requiring increased maintenance and downtimes. Although patents and the scientific literature disclose processes for the preparation of hexahydro-1,3,5-trinitro-1,3,5-triazine and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine, these disclosed processes have limitations and disadvantages. According to U.S. Pat. No. 4,163,845, “Recycle of Spent Acid in Nitrolysis of 1,3,5,7-Tetraazatricyclo[3.3.1.13,7]decane to hexahydro-1,3,5-trinitro-1,3,5-triazine” by Brumley et al., West German Pat, No. 1939541 (“Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine from 1,3,5,7-Tetraazatric