Synthesis Of HMX By Green Nitrolysis Based On N₂O₅ And Ionic Liquids And Study On The Reaction Mechanism

1,3,5,7-Tetranitro-1,3,5,7-tetraazacyclootane(HMX) is one of the most powerful explosives and is widely used in military field.3,7-Dinitro-1,3,5,7-tetraazabicyclo[3.3.1]no-nane (DPT) is a key intermediate in the production of HMX. Using urea as starting material to prepare HMX through DPT is considered as a promising method.In this paper, a green one-pot method to prepare DPT was investigated by using urea as starting material and N2O5/HNO3 as nitrating agent. The reaction parameters were also optimized. N2O5(5.5g) was dissloved in 100% HNO3(11 mL), then urea (2 g) was added in portions, the reaction mixture was stirred at 5℃ for 90 min then poured into 30 g ice-water and hydrolyzed at 10～20℃. for 90 min, then 12 mL of 37%～40% formaldehyde and 15 g water were added. After the addtion the mixture reacted at 40℃ for 40 min, cooled and neutralized to pH 7 with aqueous ammonia, DPT was obtained in 33.0% yield. It was observed that the amount of formaldehyde was the main factor affecting the stability of the reaction system.The nitrolysis of DPT in HNO3-IL system was investigated. The results showed that the yield of HMX was greatly improved compared with the nitrolysis in HNO3. The reaction mechanism of ionic liquids was explored, both anions and cations of the ionic liquid affected the yield of HMX. [Et3NH]NO3 had the best perfermance among the ionic liquids uesd, HMX was obtained in 43.0% under the optimizd condions:m(DPT)=2 g, V(HNO3)=15 mL,n(IL): n(DPT)=1:1, reacting at 25℃ for 30 min. Ionic liquid could be efficiently recovered without any apparent loss of activity after five runs.Some N-hydroxymethyl tertiary amines were prepared and acetolyzed to prepare corresponding acetamides. It was found that the reaction occurred via N-attack instead of O-attack, then the N-hydroxymethyl group was removed to give N-acylated product. The role of ammonium nitrate was also investigated, and the results indicated that it reacted with some by-products in the reaction procedure and generated nitric acid to form dialkyl ammonium nitrate, which is deactivated for acetylation. The above results give direct evidence for the acetolysis mechanism of 3,7-diacetyl-1,3,5,7-tetraazabicyclo[3.3.1]nonane(DAPT) to produce 1,3,5,7-tetraacetyl-1,3,5,7-tetraazacyclootane (TAT).The nitrolysis of N-hydroxymethyl tertiary amines were investigated, it was found that N-hydroxymethyl group was removed to give corresponding N-nitroso compound instead of O-nitration, and ammonium nitrate facilitated this process. The results proved that the nitrolysis of DPT to synthesize HMX through a N-hydroxymethyl reactive intermediate. According to the experimental facts, the mechanism of HMX from DPT was proposed.A new green and stable preparing method of DPT was developed in this dissertation. The research results might provide new idea for investigating the synthetic mechanism of HMX and the affecting mechanism of ammonium nitrate in nitrolysis process.