High rates of catalytic hydrogen combustion with air over Ti 0.97Pd 0.03O 2 - δ coated cordierite monolith

Abstract

Abstract: Ti 0.97Pd 0.03O 2 - δ was coated on γ - Al 2O 3-coated honeycomb structured cordierite monolith (AHCM) by solution combustion method using dip-dry-heat process. This is a modified conventional method to coat the catalysts on honeycomb structured cordierite monolith (HCM). Formation of Ti 0.97Pd 0.03O 2 - δ on AHCM was confirmed by XRD. The XPS spectra of Pd(3d) core level confirmed Pd ion in Ti 0.97Pd 0.03O 2 - δ is in the form of +2 state. The surface morphology of coated catalyst was unchanged by long time exposure to hydrogen combustion reaction; i.e., H 2+ O 2 recombination reaction which indicated the stability of coating on monolith. Ti 0.97Pd 0.03O 2 - δ showed high rates of H 2+ O 2 recombination compared to 2 atom% Pd(metal)/γ - Al 2O 3, Ce 0.98Pd 0.02O 2 - δ, Ce 0.98Pt 0.02O 2 - δ, Ce 0.73Zr 0.25Pd 0.02O 2 - δ, Ti 0.99Pd 0.01O 2 - δ and Ti 0.98Pd 0.02O 2 - δ. The activation energy of H 2+ O 2 recombination reaction over Ti 0.97Pd 0.03O 2 - δ is 7.8 kcal/mol. The rates of reaction over Ti 0.97Pd 0.03O 2 - δ at 60∘C are in the range between 10 and 20 μ mol/g/s. The rate of reaction over Ti 0.97Pd 0.03O 2 - δ increased with increase in the concentration of H 2. For 50 mL of H 2, it showed rates of the reaction around 36.45 μ mol/g/s at room temperature and 230 μ mol/g/s at 60∘C. It was found that the rate of reaction due was lower due to hindering effect by adsorption of other gas molecules on the catalytic site. Finally, we propose a mechanism of hydrogen and oxygen recombination reaction over Ti 0.97Pd 0.03O 2 - δ. Graphical Abstract:: Ti 0.97Pd 0.03O 2 - δ catalysts were coated by solution combustion method on γ - Al 2O 3 coated honeycomb structured cordierite monolith. Among the catalysts, Ti 0.97Pd 0.03O 2 - δ coated monolith showed high catalytic activity for hydrogen combustion with air. The proposed mechanism of H 2+ O 2 reaction clarified that Pd + 2 ion state is unaltered in Ti O 2 lattice.[Figure not available: see fulltext.].