HCN production from formaldehyde during the selective catalytic reduction of NOx with NH3 over V2O5/WO3-TiO2

Raw exhaust gases may contain notable levels of formaldehyde that can negatively impact the efficiency after-treatment systems. In selective catalytic reduction (SCR) NOx over V2O5/WO3-TiO2, was found to react with NH3 produce HCN at concentrations above threshold limit value set by environmental/safety organizations. Due this side reaction, is consumed parasitically and conversion decreases up 15 %, even after compensating for fraction lost NH3. Under similar conditions, non-reducible TiO2 support also produced moderately, thereby showing redox sites promote reaction but are not a necessary condition. To understand chemistry responsible formation, roles temperature, water, oxygen were investigated. Our results suggest new pathway production through direct NH3, which active high temperature does proceed formate route previously proposed.