A study of chemical aging effects on HDD Fe–zeolite SCR catalyst

Kinetic modeling of Fe‐BEA as NH3‐SCR catalyst—effect of phosphorous

“…Furthermore, the results show that the monomeric iron species are not as sensitive to phosphorous as the dimeric iron species but the negative impact of phosphorous exposure on the SCR activity at lower temperatures is higher for the monomeric iron sites. It should be added that in a study by Silver et al, it was shown that there is a temperature dependence of the ageing of Fe‐zeolites due to phosphorous exposure. However, in this study, the phosphorous exposure was performed at constant temperature, and therefore, possible effects of the temperature of poisoning were not included.…”

“…There is still a possibility that there are mass‐transfer limitation in the washcoat under our reaction conditions, and therefore, the received parameters should be considered as apparent rate parameters. Furthermore, in an experimental study by Silver et al, axial gradients of phosphorous were observed after exposure to phosphorous‐doped diesel fuel exhaust gases of an iron‐exchanged zeolite. However, using X‐ray Photoelectron Spectroscopy (XPS) at three locations on our phosphorous poisoned catalyst, we did not observe any gradients.…”

Impact of sulfur oxide on NH3-SCR over Cu-SAPO-34

“…Cuzeolites offer a higher activity compared to Fe-zeolites at low temperatures and a sub-optimal NO 2 /NO x ratio [11]. Unfortunately, these catalysts possess drawbacks such as a susceptibility towards hydrothermal conditions [12][13][14][15] besides hydrocarbon and chemical poisoning [16][17][18][19].…”

Emerging Applications of Environmentally Friendly Zeolites in the Selective Catalytic Reduction of Nitrogen Oxides

“…Reduced surface acidity and NH 3 storage capacity could also be observed after the deactivation of Fe-zeolite catalysts by alkali metals. Silver et al [65] concluded that P, originating mainly from lube oil, could deactivate the Fe-zeolite monolith catalysts by physically blocking the adsorption sites for NH 3 . Shwan et al [66] also investigated the chemical deactivation mechanism of Fe-BEA by P using phosphoric acid as poison, and they proposed that the deactivation proceeded in two steps: (1) short duration phosphorous exposure resulted in the information of phosphorous pentoxides (P 2 O 5 ) with a relatively low amount of metaphosphates (PO 3− ), which did not affect the NO x conversion but resulted in an increased amount of strongly adsorbed NH 3 not active in the SCR reaction; and (2) longer duration phosphorous exposure resulted in the continuous increase of PO 3− replacing the hydroxyl groups on the active Fe species, which led to the significantly decreased NO x conversion, especially in the low-temperature NH 3 -SCR process.…”