Mechanism of the action of iron-bearing additives on soot formation behind shock waves

Experiments on soot formation kinetics in ethylene pyrolysis were carried out behind both incident and reflected shock waves by laser-absorption technique at a wavelength of 632.8 nm. The mixtures being investigated consisted of 7000 and 30000 ppm ethylene and 200 and 1000 ppm iron pentacarbonyl diluted in argon. The temperature range was 1400 to 2700 K and the pressure 6 and 55 bar. The significant influence of the iron-bearing species on carbon particle growth was revealed. The iron clusters play an important role for the promotion effect of additives during soot formation. Based on the hierarchy of the characteristic times of the main kinetic processes with iron participation, an interpretation of the action of iron additives action is proposed.