Mechanism of Soot Formation in Acetylene-Oxygen Mixtures

Abstract

Abstract A computational study of the chemical kinetic effects of oxygen addition on the process of soot formation from hot acetylene is reported. The results, which are supported by trends observed in shock-tube experiments, reveal that the reaction pathway to soot identified previously for acetylene pyrolysis remains essentially unchanged in an oxidative environment. The main effects of oxygen are: (1) promotion of fuel decomposition, which alters the initiation route to soot; (2) supplementary rapid production of hydrogen atoms in the initial, small-molecule reactions, which drives the concentration of hydrogen above the equilibrium value with respect to H2 and thus enhances polymeric growth of polycyclic aromatics; (3)oxidation of aromatic radicals by molecular oxygen, which removes them from the polymeric growth. The computational results indicate a crucial need for kinetic studies of high temperature reactions between molecular oxygen and hydrocarbon radicals.