Unique Compensation Effects of Heavy Metals and Phosphorus Copoisoning over NO_x Reduction Catalysts

Abstract

Selective catalytic reduction (SCR) of NO x from the flue gas is still a grand challenge due to the easy deactivation of catalysts. The copoisoning mechanisms and multipoisoning-resistant strategies for SCR catalysts in the coexistence of heavy metals and phosphorus are barely explored. Herein, we unexpectedly found unique compensation effects of heavy metals and phosphorus copoisoning over NO x reduction catalysts and the introduction of heavy metals results in a dramatic recovery of NO x reduction activity for the P-poisoned CeO2/TiO2 catalysts. P preferentially combines with Ce as a phosphate species to reduce the redox capacity and inhibit NO adsorption. Heavy metals preferentially reduced the Brønsted acid sites of the catalyst and inhibited NH3 adsorption. It has been demonstrated that heavy metal phosphate species generated over the copoisoned catalyst, which boosted the activation of NH3 and NO, subsequently bringing about more active nitrate species to relieve the severe impact by phosphorus and maintain the NO x reduction over CeO2/TiO2 catalysts. The heavy metals and P copoisoned catalysts also possessed more acidic sites, redox sites, and surface adsorbed oxygen species, which thus contributed to the highly efficient NO x reduction. This work elaborates the unique compensation effects of heavy metals and phosphorus copoisoning over CeO2/TiO2 catalysts for NO x reduction and provides a perspective for further designing multipoisoning-resistant CeO2-based catalysts to efficiently control NO x emissions in stationary sources.

Improved K-Resistance of a Cu-Modified TiO2/CeO2 Catalyst for SCR of NOx at Low Temperatures

“…For Ti/Ce, Lewis acid sites dominated the surface. CuO modification increased the acid intensity of the catalysts, and there appeared more Brønsted acid sites over TiCu/Ce . As for K-poisoned catalysts in Figure c,d, the NH 3 adsorption behavior on KTi/Ce and KTiCu/Ce catalysts was both inhibited by alkali metals.…”

“…CuO modification increased the acid intensity of the catalysts, and there appeared more Brønsted acid sites over TiCu/Ce. 48 As for K-poisoned catalysts in Figure 5c,d, the NH 3 adsorption behavior on KTi/Ce and KTiCu/Ce catalysts was both inhibited by alkali metals. However, it can still be observed that the modification of Cu protected the NH 3 adsorption and more and stabler acid sites were preserved for KTiCu/Ce.…”

Promotional Effect of Zirconium Doping on the NH3‐SCR Activity of CeO2 and CeO2‐TA Modified by Thiourea: A Comparative Study

“…Several Py‐IR peaks can be found and the peak located at about 1542 cm −1 is assigned to the C−N stretching of pyridine adsorbed to the Brønsted acid sites [59] . The peaks at about 1445 cm −1 , 1575 cm −1 , 1597 cm −1 , and 1606 cm −1 are attributed to Lewis acid sites [60] . In addition, the peak at about 1490 cm −1 is due to the interaction of pyridine molecules with both Brønsted and Lewis acid sites [61] .…”

“…[59] The peaks at about 1445 cm À 1 , 1575 cm À 1 , 1597 cm À 1 , and 1606 cm À 1 are attributed to Lewis acid sites. [60] In addition, the peak at about 1490 cm À 1 is due to the interaction of pyridine molecules with both Brønsted and Lewis acid sites. [61] In order to further explore the influence of thiourea modification and Zr doping on the acid sites of CeO 2 catalyst, the quantitative amounts of Lewis and Brønsted acid sites were calculated according to the Py-IR curves at 150 °C and 300 °C and the results are shown in…”

Extraordinary Detoxification Effect of Arsenic on the Cadmium-Poisoned V2O5/TiO2 Catalyst for Selective Catalytic Reduction of NOx by NH3

“…Previously, Zhang et al found that the copoisoning of K and phosphorus exhibited a detoxification effect on Fe 2 O 3 /TiO 2 catalysts due to the newly formed Brønsted acid sites provided by phosphate and the enhanced redox ability originated mainly from the Fe–O–P structure. The detoxification effects of heavy metals and phosphorus or SO 2 were also demonstrated on CeO 2 /TiO 2 catalysts. , However, the copoisoning mechanisms for V-based catalysts in the coexistence of arsenic and cadmium are barely explored.…”