Poisoning Process of the V2O5-CeO2/TiO2 Catalyst by the Cumulative Effect of CaO

The poisoning process for the selective catalytic reduction of NO with NH3(NH3-SCR) by the cumulative effect of CaO on the V2O5-CeO2/TiO2(V0.5Ce20Ti) catalyst is explored in this study. Experimental results show that the CaO cumulative effect varies with the temperature windows. In a low-temperature window of about 175 degrees C, the NO conversion increased from 8.63 to 15.53% before the Ca/V molar ratio reached 0.4. The increased amount of adsorbed NO2 species by CaO doping promotes the activity via the Langmuir-Hinshelwood mechanism. In a high-temperature window of about 300 degrees C, the NO conversion remained as high as approximately 96% before the Ca/V molar ratio reached 0.6 and then rapidly decreased to 81.1%. The CaO doping amount was inversely proportional to the Ce4+/(Ce4+ + Ce3+) and V5+/(V5+ + V4+) ratios. The catalyst activity was jointly affected by the redox activity, NH3 adsorption capacity, and NOx adsorption capacity. For SO2-poisoned catalysts, the NH3 oxidation reaction leads to a reduction in NO conversion on V0.5Ce20Ti. For CaO-poisoned catalysts, SO2 promoted Bronsted NH3 adsorption and offset the redox reduction to some extent; thus the NH3 SCR activity was increased