Structured combustion catalysts based on sintered metal fibre filters

摘要

Novel efficient structured combustion catalysts based on sintered metal fibre filters (MFF) were developed. To increase specific surface area (SSA), metal fibres were coated by crack-free porous oxide films of SiO2, Al2O3, porous glass, and mesoporous SBA-15 silica. The composite materials presented uniform open macrostructure of the non-treated MFF filters and were suitable supports for deposition of catalytically active phases (Pd, Pt, and Co3O4). These catalysts were tested in hydrocarbon (CH4, C3H8) combustion. Co3O4 Supported on MFF without any coating (6.8% Co3O4/MFF) was the most active for propane total oxidation. At the same time in methane combustion the activity of this catalyst was relatively low. Pd supported on the MFF coated by mesoporous SBA-15 film (0.5% Pd/SBA-15/MFF) demonstrated the highest activity in methane total oxidation due to the high palladium dispersion. The SBA-15 film supported on MFF provided the highest dispersion of the deposited noble metals (Pd, Pt) with an average particle size similar to2.0 nm. The metal nanoparticles formed within the mesopore channels were stable against sintering during calcination and the particle diameter was observed not to exceed the diameter of the silica pores. These catalysts did not undergo deactivation under reaction conditions at temperatures up to 500degreesC. On the contrary, the Pd supported on MFF coated by the microporous SiO2 and Al2O3 films, Prepared by sol-gel technique, suffered from metal sintering during the calcination step and also during reaction, demonstrating strong catalyst deactivation. The catalytic filters are suitable materials for assembling different multiple layers to obtain structured catalytic beds with the composition/concentration gradients of active component in the axial direction. The enhanced overall catalytic performance was observed in adiabatic catalytic reactor during propane combustion due to a synergy of the 0.5% Pd/SBA-15/MFF and the 0.5% Pt/SBA-15/MFF catalytic layers assembled in the appropriate order forming gradient catalytic bed. (C) 2002 Elsevier Science B.V. All rights reserved. [References: 29]