Molecular simulation and experimental study on thermal decomposition of N,N′-dinitrosopentamethylenetetramine
N,N′-dinitrosopentamethylenetetramine (DNPT), which is a widely used as blowing agent in the rubber industry, tends to be unstable when affected by high temperature and specific impurities. The runaway of DNPT has caused several accidents and led to enormous economic losses in the world. We determined its thermal hazard properties and decomposition paths for process safety. Characteristic parameters of pure and impure (added with water and nitric acid) DNPT were obtained under different heating rates by differential scanning calorimetry experiments. Those parameters were used to calculate the apparent activation energy with the Kissinger method. Thermogravimetry was used to obtain exothermic onset temperature and peak temperature under different heating rates. The apparent activation energy of DNPT decomposition reaction was achieved by model-free kinetics approach. Quantum mechanics model was used to explore the thermal decomposition reaction pathways of DNPT. DFT B3LYP density functional method, and the 6-311++G (D) basis set was selected for molecular simulation by Gaussian 09 software. The single point energy, zero-point energy, thermal energy, thermal enthalpy, and thermal free energy were acquired. The bond dissociation energy (BDE) at different excited states was calculated. By comparing BDE of different excited states, the thermal decomposition reaction pathways can be predicted. The results of experiments and simulations can be applied as safety guidance to deal with DNPT’s loss prevention during transportation, handling, and storage, even emergency response.
KeywordsCharacteristic parameters Model-free kinetics Quantum mechanics model Bond dissociation energy Thermal decomposition reaction pathway
List of symbols
Apparent activation energy, kJ mol−1
Total energy of free radicals or molecules at 0 K, kJ mol−1
DNPT sample mass, mg
Mass of the added water, mg
Mass of the added nitric acid solution, mg
Correlation coefficient, dimensionless
Thermodynamics temperature, °C
Exothermic onset temperature, °C
Maximum reaction temperature, °C
End temperature of reaction, °C
Single point energy variation, kJ mol−1
Zero-point energy variation, kJ mol−1
Heat of decomposing, J g−1
Difference between the total zero point of free radicals or molecules after dissociation and the zero energy before dissociation, kJ mol−1
Conversion degree, dimensionless
Heating rate, °C min−1
The authors gratefully acknowledge the financial support provided by the National Natural Science Foundation of China (Grant No. 5100-6122) and the National Key Research and Development Program of China (Grant No. 2016-YFC080-1500).
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