A way to inhibit SO 2 poisoning of SCR catalysts by fine tuning of the composition and the preparation method of the support

Abstract

Two series of mixed SiO 2-TiO 2 and Al 2O 3-TiO 2 supports were prepared by the following methods : precipitation from TiCl 4 solution with aqueous ammonia, impregnation with titanium isopropoxide solution in isopropanol, and grafting by reaction of TiCl 4 with the hydroxyl groups of the main carrier (SiO 2 or A1 2O 3). 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 NH 3 in the presence of O 2. BET, XRD and XPS were used to characterise the samples. All these catalysts were less active than a standard TiO 2-V 2O 5 catalyst when tested with a SO 2-free feed. However, in the presence of 4000ppm SO 2 in the feed they were more resistant and more active than the TiO 2-V 2O 5 catalyst. Our results indicate that the dispersion of TiO 2 on the main carrier is a key factor for preparing a performant SCR catalyst. The grafting and impregnation methods for the Al 2O 3-TiO 2 and the impregnation for the SiO 2-TiO 2 supports were found to be the most effective preparation techniques for dispersing TiO 2, and for giving the most performant and resistant, towards S0 2 poisoning, catalysts.