Effects of Different Factors on Low-temperature NO Conversion of V₂O₅-WO₃/TiO₂ Catalysts

The effects of V₂O₅ loading, the volume fractions of O₂, NO, SO₂ and H₂O, n(NH₃)/n(NO), gas hourly space velocity and online heat regeneration on NO conversion of V₂O₅-WO₃/TiO₂ catalyst prepared by impregnation method were investigated. Combined with the experimental results, 3% V₂O₅ was selected as the optimal loading, and NO conversion of 3% V₂O₅-WO₃/TiO₂ catalyst was 93.7% at 160℃. The selectivity of N₂ was more than 98% and SO₂ oxidation was less than 1% in the range of 110-320℃. NO conversion of catalyst increased with the increase of the volume fraction of O₂, and decreased with the increase of the volume fraction of NO, however, the NO_x removal amount gradually increased. When n(NH₃)/n(NO) ≤ 1, the optimal activity of catalyst equalled the respective n(NH₃)/n(NO), and when n(NH₃)/n(NO)>1, the activity was barely improved. With the increase of the space velocity, the high activity temperature range of the catalyst was narrowed, and the activity decreased in varying degrees. The characterization results show that the morphology of catalyst is blurred and the surface covered with irregular flocs, specific surface area and pore volume decrease in different degrees, and tiny pores are preferred to be blocked after selective catalytic reduction (SCR) reaction containing SO₂ and H₂O. The contents of V₂O₅ are reduced 0.98% and WO₃ reduced 1.6%, the side reaction products include NH₄⁺ and SO₄^2-. During the process of online heat regeneration, catalyst delayed the decomposition of ammonium sulfate, which caused the catalyst's resistance to poisoning to be worse and the activity was difficult to be recover.