Study of the oxidation of alkanes in their mixtures with oxygen and air under the action of a pulsed volume nanosecond discharge

The slow oxidation of alkanes (from methane to hexane) in their stoichiometric mixtures with oxygen or air under the action of nanosecond pulsed discharges was investigated. The discharges were excited in a tube of diameter 5 cm and length of 20 cm by 25-ns voltage pulses with an amplitude of 10 kV and a repetition rate of 40 Hz. The initial pressure in the mixture was varied in the range 0.76-10.1 torr. The current, the electric field strength, and the power deposited in a discharge were measured with a nanosecond time resolution. In time-resolved and time-integrated measurements, the intensities of the following bands were determined: CO₂⁺(B²Σ → X²Π, δv = 0), CH(A²Δ, v′ = 0 → X²Π, v″ = 0), OH(A²Σ, v′ = 0 → X²Π, v″ = 0), CO(B¹Σ, v′ = 0 → A¹Π, v″ = 2), NO(A²Σ → X ²Π, δv = 3), N₂(C³Π, v′ = 1 → B³Π, v″ = 7), N₂(B³Π, v′ = 6 → A³Σ, v″ = 3), and N₂ ⁺(B²Σ, v′ = 0 → X²Σ, v″ = 2). The methane concentration was measured from the absorption of He-Ne laser radiation. Based on the results of optical measurements, the times of the complete oxidation of hydrocarbons were determined.