Hydrocarbon and Soot Oxidation over Cerium and Iron Doped Vanadium SCR Catalysts

Abstract

V2O5−WO3/TiO2 (VWTi) catalysts are widely employed for selective catalytic reduction (SCR) of NOx. However, due to their poor thermal stability the application in diesel particulate filters (DPFs), i. e. 2‐way SCRonDPF is limited. In this study, the potential of Ce‐ and Fe‐doped VWTi systems for hydrocarbon and soot oxidation in addition to the SCR activity was systematically investigated for fresh and thermally aged samples. The formation of metal vanadates upon thermal aging, as identified by X‐ray diffraction, Raman and X‐ray adsorption spectroscopy, prevents drastic sintering of the support and maintains a high NOx−SCR and hydrocarbon oxidation activity. Additionally, the doped VWTi catalysts show a slight increase of the CO2 selectivity during hydrocarbon oxidation, which represents an important aspect for such multifunctional catalysts. Despite of the advantages, the formation of metal vanadates hinders the mobility of vanadium species and decreases the soot oxidation ability of the doped catalysts. Interestingly, a promising soot oxidation activity was identified for the VWTi−Fe sample after aging at 650 °C, which resulted in decomposition of the iron vanadate and generation of highly dispersed and mobile V2O5.

Impact of gas phase reactions and catalyst poisons on the NH3-SCR activity of a V2O5-WO3/TiO2 catalyst at pre-turbine position

“…At atmospheric pressure, the short chain model compound propylene had a minor effect on NOx reduction up to 400 °C. These findings agree with our previous studies [17,29] and also with those of Watling et al, [30] who showed an influence on NOx conversion only above the onset temperature of propylene oxidation. Hence, with increasing the temperature and especially the pressure, the negative impact on NOx conversion was enhanced.…”

Review of Hydrocarbon Poisoning and Deactivation Effects on Cu-Zeolite, Fe-Zeolite, and Vanadium-Based Selective Catalytic Reduction Catalysts for NOx Removal from Lean Exhausts

“…In this context, several literature works reported that long-chain HCs are more effectively oxidized. 26,31,32 Even in the case of C 12 H 26 oxidation, from HC oxidation was higher than that of CO 2 (not shown in the figure). 31 As observed from Figure 21a, the introduction of dodecane under Standard SCR conditions led to a more pronounced inhibition effect of DeNOx activity with respect to what was previously described in the of C 3 H 6 .…”

“…Several studies evaluated the DeNOx performances of typical V-based catalysts in the presence of C 3 H 6 . 11,25,28,31,32 In the work of Heo et al, 11 a commercial V 2 O 5 −TiO 2 sample had been tested. Figure 20 shows the effect of the cofeed of C 3 H 6 Different from Fe-and Cu-ZSM-5 (section 2 of this review), no significant effects of the cofeed of propylene were detected on the DeNOx activity at low temperature of the tested vanadiabased catalyst; however, at temperatures higher than 350 °C, NO conversion decreased with increasing C 3 H 6 concentration in the fed gas mixture.…”

“…However, Heo et al found lower NOx conversions at high temperature in the presence of C 3 H 6 , probably due to the presence of intermediates formed by HC oxidation . Moreover, several studies suggested that long-chain HCs are more easily oxidized, ,, leading to a decrease in DeNOx performance. In this context, the tolerance to HCs and the simultaneous NOx and HC removal activity of vanadia catalysts will be analyzed in the present review, in comparison with that achieved over metal-based zeolites.…”

Soot Oxidation in a Plasma-Catalytic Reactor: A Case Study of Zeolite-Supported Vanadium Catalysts

“…Since the discharge characteristics for all four V/M catalyst-packed DBD reactors are quite similar, it can be deduced that the physicochemical properties of V/M catalysts would play a significant role in plasma-catalytic soot oxidation in this work. A V/M catalyst with a higher SBET value would provide more adsorption and active sites for the heterogeneous catalytic reactions [35]. As the average diameter of soot in this work is much larger than the pore diameters of V/M catalysts, the active sites on the external surfaces of the V/M catalysts would be of great significance in soot oxidation.…”