A Combined Experimental and Modeling Study on Isopropyl Nitrate Pyrolysis

Area of Science:

• Physical Chemistry
• Chemical Kinetics
• Combustion Chemistry

Background:

• Alkyl nitrates decompose at low temperatures via O-N bond homolysis, yielding radicals and nitrogen dioxide.
• This decomposition pathway allows for studying subsequent radical chemistry under mild conditions.

Purpose of the Study:

• To investigate the pyrolysis of isopropyl nitrate (iPN) in a tubular reactor.
• To identify major decomposition products and evaluate existing kinetic models.
• To refine kinetic models by incorporating new rate expressions for key reactions.

Main Methods:

• Pyrolysis of iPN in a tubular reactor at atmospheric pressure, temperatures from 373 to 773 K, and ~2 s residence times.
• Analysis of product yields including acetaldehyde, formaldehyde, methanol, and nitromethane.
• Testing and refinement of four nitrogen chemistry models, including iPN-specific reactions.

Main Results:

• iPN decomposition initiated at 473 K via O-N bond fission, forming isopropoxy radicals and NO2.
• Acetaldehyde was the most abundant product, followed by formaldehyde, methanol, and nitromethane.
• The Curran group's mechanism showed the best performance but underpredicted formaldehyde and methanol.
• New rate expressions for CH3 + NO2 reactions significantly improved model predictions.

Conclusions:

• The methyl radical + nitrogen dioxide reaction branching ratio is critical for accurate modeling.
• Updated kinetic models with new rate expressions show improved prediction capabilities for iPN pyrolysis.
• Further research is needed to achieve precise agreement between calculated and experimental species profiles.