New insights into the promotional mechanism of ceria for activity and ammonium bisulfate resistance over V/WTi catalyst for selective catalytic reduction of NO with NH3

The promotion of Ce-doped V/WTi for NH3-SCR performance and ammonium bisulfate (ABS) resistance is fully illustrated. The V2O5/CeO2/WTi-2 presents an excellent NOx conversion at 280 degrees C in the presence of 1000 ppm SO2. The introduction of ceria contributes to the vanadia species agglomeration into the oligomeric V-O-V structures and tight connects with the adjacent vanadium species to form the redox structure of Ce4+-O-Ce3+-O-V5+-O-V5+-O-Ce3+-O-Ce4+, which facilitates the electronic conduction between ceria and vanadia species. The electronic interaction via the redox structure promotes the activation of ammonia adsorbed on vanadia and nitrate species on ceria, which lowers the apparent activation energies (Ea) and significantly improves the NOx conversion rate. The addition of ceria protects active V sites poisoning and improves the stability of the adsorbed NOx species, which prevents VOSO4 formation and competitively inhibits the adsorption of SO2 with less metal sulfate formation on ceria. In addition, the electrons donating from vanadia to ceria species via the redox structure could make ceria species existing in electron enrichment state and boost the electrons around ceria deviating towards sulfates and strengthen the bonding between ceria and as-formed ABS species, which weakens the stability of ABS and promotes to initiate NH3-SCR reaction between the NH4+ species of ABS and NO + O-2. The faster NH3-SCR conversion rate promoted by the redox structure further suppresses the competitive reaction between sulfate and ammonia species, which results in no ABS formation over V/Ce/WTi-2.