Understanding of the effect of oxygen on soot formation during non-catalytic partial oxidation process

Non-catalytic partial oxidation (NC-POX) process is a promising technology for hydrogen and syngas production, but the generation of soot hinders its development. In this study, the yields of soot and its precursors under different working conditions are quantified by experiments. When the O2/CH4 ratio is more than 0.6, the soot yield can be controlled below 1.07% from 2.53%. The soot precursor evolution mechanism in NC-POX is analyzed through the quantification of polycyclic aromatic hydrocarbon (PAH) compounds. It is found that hydrogen abstraction vinyl radical addition (HAVA*) and methyl addition cyclization (MAC) are the main growth pathways of PAHs. The concentration of H2O, CO2, and oxygenated hydrocarbons increase with O2/CH4, which further inhibit the soot generation reactions and reduce the degree of graphitization of soot particles through surface reactions. A soot formation mechanism is proposed. This study provides a quantified reference for soot modeling and the elimination of soot in industry.