Synthesis Of Pentazole Metal Salt And Its Catalytic Performance For Thermal Decomposition Of Ammonium Perchlorate

Polynitrogen energetic materials have the advantages of high density,high enthalpy of formation,high energy and decomposition products clean and pollution-free.This kind of compound has a very good application prospect in the field of explosives and propellants,and their research has important academic significance and national defence application value.In this paper,the synthesis process of pentazole sodium was enlarged,and three pentazolate metal salts Fe（N₅）₂,Co（N₅）₂and Zn（N₅）₂were prepared based on pentazole sodium.The thermal analysis kinetics of Fe（N₅）₂and Zn（N₅）₂were studied.The catalytic effect of Fe（N₅）₂,Co（N₅）₂and Zn（N₅）₂as energetic combustion catalysts on the thermal decomposition of ammonium perchlorate（AP）in composite solid propellant was studied.Firstly,the synthesis process of pentazolium sodium was amplified,and the yield of pentazolium sodium was expanded from 9.24 g to 51.07 g.The experimental results show that the yield of pentazolium sodium decreased from 13.22%to 12.17%,which indicates that the amplification effect is obvious.There is a multi-step rotating steaming process in the post-treatment part of the reaction,and the product pentazole sodium is decomposed to a certain extent due to vacuum and heating.There was also an incomplete reaction of the strong oxidant interchlorperoxybenzoic acid,which also caused the decrease of the yield of pentazole sodium.Secondly,thermogravimetry（TG）was used to study the thermal decomposition of Fe（N₅）₂and Zn（N₅）₂salt at different temperature rates,and the kinetic parameters and apparent activation energy of N₅^-were calculated using the Kissinger,Ozawa,Kissing-Akahir-Sunose（KAS）and Flynn-Wall-Ozawa（FWO）model-free method.The mechanism function and mechanism of thermal decomposition were determined by Coats-Redfern model method based on thermal analysis data.The thermal decomposition of Fe（N₅）₂starts at 102.02℃and ends at 135.31℃,and the weight loss in this stage is 25.76%.According to the calculation,the decomposition of Fe（N₃）₂and N₂is generated,the apparent activation energy is 113.63 k J·mol^-1.The thermal decomposition of Fe（N₅）₂is a two-dimensional diffusion process（2D,deceleratingα-T curve）,with the integral form of the reaction mechanism function given by G（α）=α+（1-α）ln（1-α）.The thermal decomposition of Zn（N₅）₂starts at 98.67℃and ends at 120.35℃,and the weight loss in this stage is 24.18%.According to the calculation,the decomposition of Zn（N₃）₂and N₂is generated,the apparent activation energy is 139.71 k J·mol^-1.The thermal decomposition of Zn（N₅）₂is a three-dimensional diffusion process（3D,n=1/2）,with the integral form of the reaction mechanism function given by G（α）=[1-（1-α）^1/3]^1/2.Finally,in order to study the catalytic effect of several representative pentazole metal salts（Fe（N₅）₂,Co（N₅）₂and Zn（N₅）₂）as energetic combustion catalysts on ammonium perchlorate（AP）,thermogravimetric（TG）and differential scanning calorimetry（DSC）experiments were carried out on ammonium perchlorate with different content of catalysts at different heating rates,the decomposition kinetic parameters of AP were obtained by Kissinger method and Ozawa method.The results show that with the increase of catalyst content,the catalytic effect on AP is more obvious.From the calculated decomposition kinetic parameters,it is found that the catalytic effect of three pentazole metal salts on AP is mainly in the high temperature decomposition stage.The addition of 5 wt.%Zn（N₅）₂has the best catalytic effect,which can combine the high and low temperature decomposition peaks of AP thermal decomposition,reduce the peak temperature to 287.3℃and the activation energy to 123.59 k J·mol^-1.Secondly,the addition of 5 wt.%Co（N₅）₂can reduce the decomposition peak temperature of AP to 296.3℃and the activation energy to 152.64k J·mol^-1.Finally,5 wt.%Fe（N₅）₂was added to reduce the decomposition peak temperature of AP to 368.4℃and the activation energy to 156.61 k J·mol^-1.