Deactivation Mechanism of Potassium on the V₂O₅/CeO₂ Catalysts for SCR Reaction: Acidity, Reducibility and Adsorbed-NO_x

Abstract

A series of V2O5/CeO2 catalysts with different potassium loadings were prepared to investigate alkali deactivations for selective catalytic reduction of NOx with NH3. An alkali poisoning mechanism could be attributed to surface acidity, reducibility, and NOx adsorption/desorption behaviors. The detailed factors are as follows: (1) decrease of surface acidity suppresses NH3 adsorption by strong bonding of alkali to vanadia (major factor); (2) low reducibility prohibits NH3 activation and NO oxidation by formation bonding of alkali to vanadia and ceria (important factor); (3) active NOx(-) species at low temperature diminish because of coverage of alkali on the surfaces (minor factor); and (4) stable, inactive nitrate species at high temperature increase by generating new basic sites (important factor).

Experimental and DFT studies on Sr-doped LaMnO3 catalysts for NOx storage and reduction

“…Another new peak centered at 293°C appeared for LSM3 and grew considerably for LSM4. The total NO x desorption significantly decreased 38,39 In comparison to the peaks for LSM4 and LSM3, the intensity of the low temperature NO peak increased significantly. Previous work on a comparative study on α-Mn 2 O 3 and β-MnO 2 obtained similar TPR peaks at approximately 300°C on pure β-MnO 2 material.…”

New insight into the promoting role of process on the CeO2–WO3/TiO2 catalyst for NO reduction with NH3 at low-temperature

“…From the above catalytic test results, we could conclude that the WO 3 species could improve the SCR catalytic reaction for CeO 2 /TiO 2 catalyst and the CeO 2 -WO 3 /TiO 2 catalyst had high catalytic activity, especially at low-temperature. 3 were not observed. It indicated that TiO 2 consisted of anatase as the unique phase and WO 3 species were well-dispersed over the support by calcination at 500°C.…”

“…CeO 2 and WO 3 of CeO 2 -WO 3 /TiO 2 had strong hybridization between the orbitals of W5d and Ce5d. The interaction decreased the level of the CB bottom and VB top of CeO 2 in CeWTi catalyst.…”

“…Selective catalytic reduction (SCR) of NO with ammonia is the most efficient technique for abating NO emission from power plants. Commercial catalysts for the above reaction are based on V 2 O 5 -WO 3 /TiO 2 or V 2 O 5 -MoO 3 /TiO 2 [3]. However, these catalysts are efficient only within a narrow temperature window of 320-400°C, and the loss of V 2 O 5 species at high-temperature is hazardous to environment and to human health.…”

Rational Design of Alkali‐Resistant NO Reduction Catalysts using a Stable Hexagonal V‐Doped MoO3 Support for Alkali Trapping

“…Selective catalytic reduction (SCR) of NO with NH 3 over supported V 2 O 5 catalysts is efficient for controlling NO emissions from coal‐fired power plants,, but it is different to be applied in industrial glass and cement boilers, steel furnaces, and bio‐fueled boilers, because high‐concentration alkali metal ions in the stack gases often lead to severe deactivation of such SCR catalysts . Thus, it is desirable to develop SCR catalysts with strong resistance against alkali poisoning for controlling NO emissions especially in China, because some related regulations have been increasingly stringent.…”