Study On The Synthesis Of Hmx With N₂O₅

1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane(HMX) has the best overall performance in high explosives applied.3,7-dinitro-1,3,5,7-tetraaza-bicyclo[3.3.1]nonane(DPT) is an important intermediate for the preparation of HMX. Presently the method of using urea, formaldehyde, ammonia as raw materials to prepare HMX through DPT is widely used, which has the advantages of no need of acetic anhydride, cheap raw materials, less side product, safe processes and so on.In this paper, a one-pot method of DPT preparation has been investigated by using urea as the starting material and N2O5/HNO3as the nitrating agent. Urea (2g) was added under stirring at-5℃to0℃to a mixture of10mL of anhydrous nitric acid and5.5g of N2O5. The mixture was stirred for90min at5℃and poured into15mL of an ice-water mixture to react for90min at20℃, and16mL of a37%formalin solution and40mL H2O was added. The mixture was heated to40℃, stirred for40min, cooled, and neutralized to pH7.0with25%aqueous ammonia at20℃. It was then stirred for60min at20℃, and the precipitate was filtered off, washed with water, and dried at room temperature until constant weight.2.286g of DPT was obtained (31%yield). This novel process has not been reported before and has the prospect of practical appliction.The direct ammonium nitrate-free nitrolysis of DPT to synthesize HMX with ionic liquids was investigated. The result showed that ionic liquids [Et3NH]TsO was the best one among ionic liquids used. The yield of HMX was up to49.7%with ionic liquids against26.3%without ionic liquids under the optimal reaction condition:the molar ratio of [Et3NH]TSO to DPT is1:1, the mass ratio of nitric acid to DPT is10.5:1, reacting for40min at25℃. It also showed that [Et3NH]NO3was the most effective ionic liquids in this system with N2O5, which yield HMX up to60.0%under the optimal reaction condition:the molar ratioof [Et3NH]NO3to DPT is0.75:1, the mass ratio of nitric acid to DPT is10.5:1, the mass ratio of N2O5to DPT is1:1, reacting for40min at25℃. In addition, ionic liquid could be conveniently recovered by distillation in vaeuum and reused without any apparent loss of activity even after five runs.