Experimental study on the effect of different CO2 concentrations on soot and gas products from ethylene thermal decomposition

► Soot can originate in oxy-fuel combustion processes. ► Thermal decomposition of ethylene-CO2 mixtures is studied as representative of soot precursors. ► Influence of different CO2 levels is studied on soot and gas products produced in the pyrolysis of C2H4. ► CO2 may inhibit or sensitize soot formation depending on its concentration. ► Main gas products (C2H2, H2, CO and H2O) in the C2H4-CO2 pyrolysis are related to soot-forming tendency.