Experimental and modeling study of the impact of interphase and intraphase diffusional limitations on the DeNOx efficiency of a V-based extruded catalyst for NH3–SCR of Diesel exhausts

The influence of inter- and intra-phase diffusional limitations on the DeNOx activity of an extruded V2O5–WO3/TiO2 SCR monolith catalyst was studied by both experimental and modeling tools over a wide temperature window and over the full range of NO2/NOx feed ratios. The comparison of the DeNOx activity of monolith and powdered catalyst enabled a direct evaluation of the mass transfer resistances. These were found to affect NH3 and NOx conversions to an extent depending on temperature and on NO2 feed content, and were satisfactorily predicted by a 1D + 1D mathematical model of SCR monolith converters.

• Mass transfer in extruded SCR monolith assessed by comparison with powdered catalyst. • Importance of mass transfer phenomena depends on temperature and NO2/NOx feed ratio. • 1D + 1D model provides good account of intra and interphase diffusional resistances. • Role of intra- and interphase limitations discriminated by model simulations.