Process Safety Assessment For The Synthesis Of HMX By Acetic Anhydride Method

Octogen(HMX) is used in the military as the best overall performance of explosives, and the most well-known synthesis method of HMX is acetic anhydride method. Current studies are mainly about how to improve the yields, few attention are paid to the process safety. However, the nitration reaction is an important field of chemistry industry, and it is famous as its high reaction heat generation and high risks. So, make the risk assessment of the process, and determine the risk rank will make a great sense in promoting safety production and inherent safety.Differential scanning calorimeter (DSC) was employed to study the decomposition kinetics of one of the raw materials-urotropin. The results showed that this reagent will decompose during the melting process, and the activation energy before and after melting were the same, indicated that the decomposition mechanism were the same. Accelerating rate calorimeter (ARC) was used to study the decomposition of urotropin as well, the results showed that the onset temperature of urotropin was 230.28℃, with a violent exothermic and large gas production reaction. Indicated that once the decomposition happens, it would be very difficult to control.After several small scale experiments, reaction calorimetry (OptiMax and RC1) were employed to do the synthesis reaction, the test results indicated that the process was sensitive to the feeding temperature, the yield was very low at high feeding temperature; stirring speed didn’t have much effect on the reaction heat release and yield; On the cooling step, if we added some water to the mixture to help cool down the mixture, it would affect the purity of the product. Moreover, the HPLC test indicated that the larger ratio of HAc, the higher purity of products will get, however, the higher ratio of HAc would result in lower yield.Safety diagram and risk assessment matrix were used to assess the process, if the feeding temperature was 45℃, the risk of the feeding step was ’acceptable’ by safety diagram, and the risk rank was ’2’ by risk assessment matrix, the two results matched very well. Meanwhile, the risk of the heating step was ’acceptable’ by safety diagram, and the risk rank was ’4’ by risk assessment matrix, which means we have to take appropriate measures to reduce or avoid the risk.