Effect of potassium chloride addition on soot formation during ethylene pyrolysis in a flow reactor

Abstract In this work, we investigated the effect of potassium chloride (KCl) addition on soot formation during ethylene pyrolysis in a flow reactor by using micro-orifice probe sampling in tandem with a series of systematic characterizations. The particle size distributions measured by a scanning mobility particle sizer showed that, with the addition of KCl, the nucleation of soot particles was not affected while the size growth of soot particles was inhibited. Then the morphology and mass of soot particles were examined by a transmission electron microscopy (TEM) and a centrifugal particle mass analyzer, respectively. The TEM images and mass-mobility relationship further showed that, soot particles were generally more compact and the primary particle size distributions were narrower when KCl was added. To understand what happened to the particle growth process, the charge characteristics were examined via tandem differential mobility analyzers. The number of particles with both double and triple positive charges was found to decrease with the increase of KCl concentration, indicating that the multi-charged particles were neutralized by KCl, which could lead to slower coagulation rates and thus smaller particles.