Nitric oxide conversion to nitrogen on the W3O6 cluster through the ammonia selective catalytic reduction reaction: a DFT study

Abstract

Nitric oxide (NO), a harmful byproduct of fossil fuel combustion, can be effectively removed via the Selective Catalytic Reduction (SCR) process using ammonia (NH3), producing N2 and H2O. This study investigates the SCR mechanism of NO by NH3 over the W3O6 cluster using the DFT/M06-L/LANL2DZ-ECP/aug-cc-pVTZ method. Chemisorption of NO on W3O6 forms a stable W3O6–NO intermediate (−34.47 kcal·mol−1), initiating the reaction, followed by NH3 adsorption (−25.14 kcal·mol−1). The overall mechanism includes: (i) NH3 adsorption and dehydrogenation, (ii) NO adsorption and nitrosamine formation, (iii) nitrosamine rearrangement, (iv) N2 and H2O formation, and (v) gas desorption and catalyst regeneration. Nitrosamine formation is identified as the rate-determining step, with an activation barrier of 33.45 kcal·mol−1. The calculated rate constant (1.88 × 10−12 s−1) from Harmonic Transition State Theory (HTST) confirms its critical role in controlling the SCR reaction kinetics.