Low temprature and highly efficient oxiation of soot by O₂ over RU-based catalysts in fluidized bed reactor

The potentiality of Ru-based catalysts for soot oxidation by O₂ in fluidized bed reactor has been conducted with temperature programmed reaction (TPR) technique. Compared to Pt/SiO₂, Ru/SiO₂ exhibited a higher activity in fixed bed reactor. The catalytic activity increased further after other metal oxides loading as second carrier. Among the Ru/MO_x/SiO₂ (M=Al, Zr, Ti), Ru/TiO₂/SiO₂ showed the highest activity and its T₅₀ decreased to 435°C, which was 83°C lower than Ru/SiO₂. Two types of active sites, Ru_xTi_(1-x)O₂ and RuO_x, have been identified on the surface of Ru/TiO₂/SiO₂. Low temperature calcination for Ru/TiO₂/SiO₂ produced the well-dispersed active sites and benefited the soot oxidation. Compared with fixed bed reactor, Ru-based catalysts are capable of lowering considerably soot combustion temperature in fluidized bed reactor. T₅₀ of the soot oxidation reaction over Ru/TiO₂/SiO₂ decreased to 389°C. The increase in soot oxidation efficiency at low temperature active sites in the fluidized bed reactor is attributed to the easier migration of activated oxygen species between gas and solid since fluidization improved mass transfer.