Study On Synthesis Process And Performance Of 1-Methyl-3,4,5-Trinitropyrazole

1-methyl-3,4,5-trinitropyrazole（MTNP）was a kind of high-energy insensitive explosive with low melting point,and its detonation properties were similar to RDX and the sensitivity was close to B explosives.All these characteristics indicated that MTNP could be a potential energetic material as cast explosive carrier which would replace TNT.However,the synthesis process of MTNP is immature currently,which seriously hinders its widely application.Therefore,it has a certain practical significance and application value for the synthesis of MTNP.The synthesis process of one-step nitration of MTNP was studied with the raw material of N-methylpyrazole and the 20%fuming oleum and 98%nitric acid system.The synthesis process were optimized by single factor experiment and orthogonal experiment.And the best reaction conditions were obtained as follows:the volume ratio of 20%oleum（SA）and 98%nitric acid（NA）,v（SA）:v（NA）=3:1;the mole ratio of 98%nitric acid and N-methylpyrazole（N-MP）,n（HNO₃）:n（N-MP）=5:1;reaction temperature 110℃;reaction time 2 h;the yield of target products was up to 55.73%.In addition,the product could be obtained through direct filtration and its purity was 99.0%.The reaction products were characterized by melting point,FT-IR,¹HNMR,¹³CNMR,elemental analysis,MS and HPLC.In the 100-gram enlargement experiment,the yield of MTNP was decreased.The synthesis routes of MTNP in two steps was explored in this paper.And the single experiment was conducted to synthesize the optimal conditions in the first step:the mole ratio of N-methylpyrazole,nitric acid and sulfuric acid,n（N-MP）:n（HNO₃）:n（H₂SO₄）=1:2:4;reaction temperature 50℃;reaction time 1 h and the yield 90.53%.The first-step nitration product was characterized by melting point,TLC,HPLC and FT-IR.The best process conditions for the synthesis of MTNP in the second step conducted by the single experiment:the volume ratio of 20%oleum and 98%nitric acid,v（SA）:v（NA）=2:1;the mole ratio of 98%nitric acid and 1-methyl-4-nitropyrazole（1-M-4-NP）,n（HNO₃）:n（1-M-4-NP）=4:1;reaction temperature 120℃;reaction time 3 h and the yield of target products was up to 35.14%,the total yield of two steps was 31.81%.The solubility of MTNP in ten pure solvents and four binary solvents at different temperature was determined by the gravimetric method.The results showed that the solubility data increase with the increasing temperature in each solvent.And in the alcohol solvents,the solubility values in alcohols decreases as the increasing number of carbon atoms.Furthermore,the fitting equation were used to correlate the measured solubility data and obtained a reasonable solubility curve,and the dissolved thermodynamic properties of MTNP were calculated.In addition,benzene,methanol and ethanol were selected to crystallize according to solubility values,and the crystal morphology and safety performance of the product were characterized.The results showed that the crystals and angles of ethanol were small,the impact sensitivity was reduced by 24%compared with the crude product,and the size uniformity of product is better.The thermal performance of MTNP was measured in this paper.The DSC curve showed that the melting point was 91.9℃and the decomposition temperature was 272.0℃;the five seconds lag flashpoint was 274.9℃,indicated that MTNP had good exotherm in decomposition process and had good thermal stability.