Combustion and Pyrolysis Kinetics of Chloropicrin

Area of Science:

• Chemical kinetics
• Combustion science
• Environmental chemistry

Background:

• Chloropicrin (CCl3NO2) is a widely used agricultural chemical with historical use as a chemical agent.
• Understanding its combustion and pyrolysis is critical for safety during storage, handling, and disposal.
• Accurate kinetic data is needed for modeling accidental fires and controlled destruction processes.

Purpose of the Study:

• To develop and validate a detailed chemical kinetic model for chloropicrin combustion and pyrolysis.
• To elucidate the primary degradation pathways and key intermediates.
• To compare combustion and pyrolysis behavior and assess the impact of oxygen.

Main Methods:

• Quantum chemistry calculations were employed to determine thermo-kinetic parameters.
• Reaction rate theory was used for parameter estimation.
• A detailed chemical kinetic model was constructed.
• The model was validated against experimental pyrolysis data.

Main Results:

• The C-N bond breaking is identified as the initial step in chloropicrin degradation.
• Oxidation of the trichloromethyl radical by NO2 forms CCl3ONO, leading to NO, Cl, and phosgene.
• Phosgene is a more stable decomposition product, requiring higher temperatures for further breakdown.
• Oxygen has minimal impact on reactivity and product distribution due to chloropicrin's lack of hydrogen.

Conclusions:

• The developed kinetic model accurately predicts chloropicrin pyrolysis.
• The degradation mechanism involves C-N bond scission and subsequent oxidation, producing phosgene.
• The absence of hydrogen atoms significantly influences combustion and pyrolysis behavior, making oxygen addition less impactful.