Continuous And Electrochemical Preparation Of Typical Energetic Compounds

2,2’,4,4’,6,6’-hexanitrostilbene,abbreviated as hexanitrostilbene（HNS）,is a widely used high-energy,low sensitivity and heat-resistant explosive.In order to improve the yield of HNS produced by one-step process,it is proposed to use a static mixer as a material mixing tool to continuously mix the materials;and further convert the HNBB in the by-product into HNS through electrocatalysis,so that the yield and purity of HNS are improved.Nitropyrazole has good compatibility with most energetic materials and is a kind of energetic catalyst with potential application value.In this paper,a green and efficient method for the preparation of nitropyrazoles is provided by the electrosynthesis method,using Fe（NO₃）₃·9H₂O as the nitro source,and combining with the rearrangement reaction.First,a one-step continuous preparation of HNS was carried out using a static mixer,and the best process conditions were obtained through a single-factor control method:the static mixer was selected SK type,the solvent feed ratio was tetrahydrofuran:methanol=2:1,TNT and sodium hypochlorite the material molar ratio of the solution is n（TNT）:n（Na Cl O）=1:1.2（the flow rate of TNT solution is 6 m L/min）,the reaction temperature is kept at about 15℃,and the reaction duration is preferably 1.5 h;the effective chlorine content of sodium hypochlorite is5%;25wt%H₂SO₄ and 6wt%Na OH adjusts the p H of the system to keep it between 10 and10.5.The crude product is digested with acetone and recrystallized for refining.Determine the product by nuclear magnetic resonance analysis,infrared analysis,etc.Under these conditions,the yield of the reaction was 47%,the purity is 96.7%.Secondly,the factors affecting the continuous preparation of HNS assisted by electrochemistry were studied,and the best process conditions for the electrocatalytic process were obtained:tetrabutylammonium perchlorate was used as the electrolyte,and DMSO was used to dissolve the HNBB in the by-products,and the experimental temperature was maintained at 25℃around.A graphite rod（（37）=6 mm）was installed on the three-necked flask as the anode,and the platinum electrode（10 mm×10 mm）was used as the cathode.Using tertiary amine as a dehydrogenating agent,the reaction mixture was electrolyzed at a constant current of 8 m A for 0.6 h.Determine the product by nuclear magnetic resonance analysis,infrared analysis,etc.Under these conditions,the yield of the reaction was 53%,the purity is98%.And the process of 10 g level experiment has been stable.Finally,the influencing factors of the electrochemical synthesis of nitropyrazole are studied,and the best process conditions are obtained:（1）4-NP nitration—reaction time is 8 h,graphite is used as anode,platinum plate is used as cathode,and the reaction temperature is kept at Around 80°C,the reaction constant current is preferably 15 m A;the electrolyte is tetrabutylammonium tetrafluoroborate,the solvent is acetonitrile,and the metal nitrate is Fe（NO₃）₃.9H₂O.Under these conditions,the reaction yield is 86%;（2）1,4-DNP rearrangement—rearrangement agent is o-dichlorobenzene,the reaction temperature is 175℃,and the reaction is heated to reflux for 8 hours.The amount of Fe（NO₃）₃·9H₂O is 2.4 mmol.Under these conditions,the reaction yield is 65.3%;（3）3,4-DNP nitration-reaction time is 8h,graphite as anode,platinum sheet as cathode,the reaction temperature is kept at about 85℃,and the reaction constant current is preferably 20 m A;the electrolyte is tetrabutyltetrafluoroethylene borate ammonium,the solvent is acetonitrile,and the metal nitrate is Fe（NO₃）₃.9H₂O.Under these conditions,the reaction yield is 80%.Nuclear magnetic resonance analysis,infrared analysis,mass spectrometry,liquid phase analysis,etc.are used to determine the above products.The mechanism of electrochemical preparation of N-nitropyrazole was speculated reasonably by cyclic voltammetry combined with free radical capture experiment.