Reaction Characteristics of Monolithic Catalysts with Different Size of Channels for NOₓ Reduction

Abstract

The NOₓ reduction with carbon and NH₃ on various monolithic catalysts was investigated over a wide range of space velocity. A three-component composite catalyst, Co-La₂O₃-Pt, supported on active carbon (DIAHOPE 008) was used. It was pulverized into fine powder, and after mixing with hydrogel of aluminum hydroxide, this was molded into cylindrical forms with an inner channel of three sizes along the axial direction. The maximum limit of space velocity (SVₘₐₓ) to achieve a 100% NO conversion was mainly discussed. The same catalyst components were extensively supported on substrates having various channel structures of ceramic honeycomb. For these substrates, the effects of alumina sol-precoating and thermal treatment on the NO-NH₃ reaction were studied. The 0.93% Co-0.51% La₂O₃-1.6% Pt catalyst supported on the honeycomb precoated with 9.2% AI₂O₃ and calcined at 600°C for 1 hour gave the best performance among the various catalyst components. It also showed the best performance among the various structures from the viewpoint of SVₘₐₓ for achieving a 100% NO conversion.