Self-ignition and reaction promotion of H2 with CO2/O2 in Pt-Coated γ-Al2O3 bead reactor

• A fixed-bed reactor filled with catalyst beads is used for catalytic combustion.
• Self-ignition of hydrogen is observed in the stream of inert-diluted O2.
• Without preheating, self-ignition cannot be initiated if the fuel contains CO.

This paper presents an experimental study on the self-ignition of H2 under different oxidation conditions and to explore how H2 assists CO oxidation in a CO2-diluted stoichiometric stream via a catalytic reactor filled with lab-made catalyst. We characterize the light-off process by measuring the temperature time profile and radial temperature distribution at the reactor exit, the axial temperature distribution in the reactor, and the average reaction temperature for various fuel quantities under different oxidation conditions. The results show that hydrogen self-ignites in a stream of excess air, N2-, and CO2-diluted stoichiometric O2 without additional reactant preheating. However, self-ignition cannot be initiated if the fuel contains CO. The hydrogen mixed with CO2-diluted stoichiometric O2 can be used in the preheating of the catalytic reactor. After the temperature stabilizes, CO or syngas can be added and oxidized in the CO2-diluted stoichiometric O2 stream. However, because the volume fraction of CO is larger than that of H2 in the reactant stream, oxidation cannot be sustained in the present reactor. Moreover, the conversion ratio decreases as the volume fraction of hydrogen in the reactant mixtures increases in the cases of hydrogen oxidation with inert-diluted stoichiometric oxygen.