Flame soot generated under controlled combustion conditions: Heterogeneous reaction of NO₂ on hexane soot

We used a Combustion Aerosol Standard burner unit that affords controlled and adjustable flame conditions, and adapted it for use with liquid fuel. We prepared samples of hexane soot under different well‐defined combustion conditions, and probed the chemical properties of hexane soot by using its heterogeneous interaction with NO 2 in a Knudsen flow reactor. Soot generated under conditions of fuel to oxygen ratio near stoichiometry (λ = 0.82) produced HONO as the main product. Yields of HONO decreased for soot generated under lean conditions (λ = 0.16). Finally, NO was the principal product of the reaction for soot generated under extremely lean conditions (λ = 0.09) corresponding to the lower flammability limit. We may conclude that the combustion conditions determined surface properties gauged by the heterogeneous NO 2 –soot interaction.