Alkali Metal Poisoning of a CeO₂–WO₃ Catalyst Used in the Selective Catalytic Reduction of NO_x with NH₃: an Experimental and Theoretical Study

Abstract

The alkali metal-induced deactivation of a novel CeO(2)-WO(3) (CeW) catalyst used for selective catalytic reduction (SCR) was investigated. The CeW catalyst could resist greater amounts of alkali metals than V(2)O(5)-WO(3)/TiO(2). At the same molar concentration, the K-poisoned catalyst exhibited a greater loss in activity compared with the Na-poisoned catalyst below 200 °C. A combination of experimental and theoretical methods, including NH(3)-TPD, DRIFTS, H(2)-TPR, and density functional theory (DFT) calculations, were used to elucidate the mechanism of the alkali metal deactivation of the CeW catalyst in SCR reaction. Experiments results indicated that decreases in the reduction activity and the quantity of Brønsted acid sites rather than the acid strength were responsible for the catalyst deactivation. The DFT calculations revealed that Na and K could easily adsorb on the CeW (110) surface and that the surface oxygen could migrate to cover the active tungsten, and then inhibit the SCR of NO(x) with ammonia. Hot water washing is a convenient and effective method to regenerate alkali metal-poisoned CeW catalysts, and the catalytic activity could be recovered 90% of the fresh catalyst.

Communication: Different behavior of Young's modulus and fracture strength of CeO2: Density functional theory calculations

“…We employed DMol 3 software package for these DFT calculations, which has been used for various investigations of CeO 2 such as surface defects, 31 water adsorption, 32 and catalytic reduction. 33 The validity of DMol 3 was already confirmed by the previous studies. We used the double-numeric polarized basis set with a globalspace cutoff of 5.8 Å and periodic boundary conditions with a Monkhorst-Pack grid of 4 × 4 × 4.…”

Selective catalytic reduction of NO with NH3 over CeO2–ZrO2–WO3 catalysts prepared by different methods

“…And the other peak located at 765 ºC can be considered as the reduction of W 6+ [29] . As for the other samples, the corresponding profiles, which is beneficial to the low-temperature activity.…”

Promotional effect of Nb additive on the activity and hydrothermal stability for the selective catalytic reduction of NO with NH3 over CeZrO catalyst

“…4. For the CeZr 2 O x catalyst, the reduction peak at about 510 • C was assigned to the reduction of surface Ce 4+ to Ce 3+ , and the peak at 736 • C could be attributed to the reduction of bulk CeO 2 [21][22][23]. In addition, the reduction peak of Nb 2 …”