STUDIES ON SOL-GEL DERIVED CATALYTIC FILTERS

Catalytic filters were prepared by depositing a gamma-Al2O3 layer on the pore walls of high-temperature resistant alpha-Al2O3 porous candles by a sol-gel procedure. Once activated with suitable catalytic principles such filters might outperform conventional technologies in the treatment of flue gases since they enable simultaneous dust removal and catalytic abatement of gaseous pollutants (NOx, VOCs, etc). The obtained filters were characterised from either a structural or a catalytic viewpoint, employing in this last case isopropanol dehydration (catalysed by the acidity of gamma-Al2O3 itself with no need of further deposition of catalytic principles) as a model reaction to simulate the capability of the filter of catalytically abating noxious gases. The effect of the amount of catalyst added on the pressure drops and the attainable catalytic conversions is studied. It is demonstrated that nearly complete catalytic conversion of isopropanol (feed concentration: 1600 ppmv in He) can be achieved for superficial velocities of industrial interest (>10(-2) Nm(3) m(-2) s(-1)), and with acceptable pressure drop increases compared with the virgin filters. Model calculations, based on a pseudo-homogeneous approach with no use of fitting parameters, are in good agreement with the experimental data.