Research On Thermal Stability Of 2-ethylhexyi Nitrate And Thermal Hazard In Its Synthesis Process

2-Ethylhexyl nitrate (EHN) is an important nitro compound for chemical industry, which is produced by concentrated HNO3-H2SO4 nitration process. However, many fire and explosion accidents have occurred in this nitration process due to thermal runaway of reaction and thermal decomposition of EHN. Therefore, it is very necessary to study the thermal hazard of this nitration reaction. In this paper, the thermal matrix method and runaway scenario analysis method were used to evaluate the thermal safety of this nitration reaction. It is very useful for the actual reaction if the fundamental reasons of thermal runaway were found.Firstly, based on the experiments of differential scanning calorimeter (DSC), the interruption and re-scanning method was used to determine the decomposition characteristic of EHN. EHN was measured by DSC under non-isothermal and isothermal conditions, then its thermal decomposition kinetics were calculated by Friedman method. The decomposition reaction model of EHN was determined by Malek method and verified by an isothermal method. According to the test results, it can be concluded that the decompositions of EHN accord with the law of "n-order". The results indicated that the values of activation energy (E) for EHN were almost same under non-isothermal and isothermal conditions.In addition, EHN with concentrated acid was measured by DSC and adiabatic accelerating calorimeter (ARC) under serious condition, and the results indicated that, concentrated sulfuric acid, concentrated nitric acid and mixed acid all could decrease the stability of EHN, especially for concentrate sulfuric acid.The reaction calorimeter (RCle) was used to analysis the exothermic characteristic of nitration reaction. The influence of each parameter for thermal safety was analyzed under different situation. Then the thermal matrix method and runaway scenario analysis method were used to evaluate the thermal safety of each reaction. The results showed that, temperature plays the most important role in the thermal runaway. The runaway reaction will be occurred when the reaction temperature was higher than 25℃. According to the results of the thermal matrix method and runaway scenario analysis method, the risk was not accepted when the reaction temperature was higher than 30℃.In addition, the by-product of runaway reaction was determined by Gas Chromatography-Mass Spectrometer (GC-MS) and Fourier Transform Infrared Spectrometer (FTIR). Based on the test results, the most probable by-product was formic acid isooctyl. According to the decomposition mechanism of EHN and by-product of nitration process, the most probable runaway pathway was concluded. The reaction phenomenon could also confirm with this probable runaway reaction well. In conclusion, the side reaction not only is decomposition reaction, but it contains some other complex reaction, such as oxidation reaction and substitution reaction.