A Way To Inhibit So2 Poisoning of Scr Catalysts By Fine-tuning of the Composition and the Preparation Method of the Support

Two series of mixed SiO2-TiO2 and Al2O3-TiO2 supports were prepared by the following methods : precipitation from TiCl4 solution with aqueous ammonia, impregnation with titanium isopropoxide solution in isopropanol, and grafting by reaction of TiCl4 with the hydroxyl groups of the main carrier (SiO2 or Al2O3). The vanadia catalysts, resulting from the impregnation of these mixed supports with an aqueous solution of vanadium oxalate, were tested in the selective catalytic reduction (SCR) of NO with NH3 in the presence of O2. BET, XRD and XPS were used to characterise the samples. All these catalysts were less active than a standard TiO2-V2O5 catalyst when tested with a SO2-free feed. However, in the presence of 4000ppm SO2 in the feed they were more resistant and more active than the TiO2-V2O5 catalyst. Our results indicate that the dispersion of TiO2 on the main carrier is a key factor for preparing a performant SCR catalyst. The grafting and impregnation methods for the Al2O3-TiO2 and the impregnation for the SiO2-TiO2 supports were found to be the most effective preparation techniques for dispersing TiO2, and for giving the most performant and resistant, towards SQ2 poisoning, catalysts.