Improvement of NH3-SCR performance and SO2 resistance over Sn modified CeMoOx electrospun fibers at low temperature

Abstract

A series of novel Sn modified CeMoOx electrospun fibers were fabricated using a combination method of sol-gel process and electrospinning technique for the selective catalytic reduction (SCR) of NO with NH3. The performances of fresh and sulfated Sn modified CeMoOx catalysts in the presence of different amount of SO2 at low temperature were investigated. Characterization of these catalysts aimed at elucidating the effect of additive. The catalyst had a Sn/(Sn + Ce + Mo) = 0.2 M ratio showed the widest SCR activity improvement with near 100% NOx conversion at 225–450 °C with a gas hourly space velocity of 100 000 h−1. X-ray photoelectron spectroscopy (XPS) indicated that Sn modification significantly increases the chemisorbed oxygen species that may facilitate NO oxidation to NO2. H2-TPR and NH3-TPD characterization showed that the catalysts have better redox ability and higher Brønsted acid sites, which is also enhanced by Sn modification. Combined with the adsorption and transient reaction studied from in situ DRIFTs spectra suggested a “fast SCR” reaction route, i.e., the more active NH4+ ions react with gaseous NO2 molecules, which primarily occurred on the surface of either the fresh or sulfated Sn/0.2-CeMoOx. Furthermore, as compared to CeMoOx, the sulfated Sn/0.2-CeMoOx sample obtained even smaller grain size, better redox ability, higher Brønsted acid sites and more chemisorbed oxygen species, which were contributed to the excellent SO2 resistance.