Effect of O_2 content during calcination of V_2O_5?WO_3/TiO_2 catalyst on selective catalytic reduction activity of NO by NH_3

摘要

Vanadium-titanium based catalyst has been widely used for abatement of NOxfrom flue gas, i.e. selective catalytic reduction (SCR) of NOx by NH_3. Although this catalyst hasbeen produced on a large-scale, fundamental research on calcination atmosphere is very little inthe literature. Since calcination atmosphere, especially O_2 content, may influence nature of theactive components and thus the activity, this work presents a systematic study in this aspect withthe aids of activity test, XPS, FTIR and NH3-TPO and NH3-TPD. The catalysts in this work aretermed according to the O_2 content during calcination, such as 47O or 10O. Results indicate that ahigher O_2 content during calcination has a positive effect on the SCR activity but little effect onthe mechanical strength. O_2 content during calcination does not influence the form of tungsten,which is WO3 in all the catalysts. Vanadium in all the catalysts is in two forms, V~(5+) and V~(4+). V~(5+)content in the fresh catalyst increases with an increase in O_2 concentration during calcination butthat in the used catalyst is reverse, indicating transformation of V~(5+) to V~(4+) for 47O catalyst andtransformation of V~(4+) to V~(5+) for 0O catalyst. A higher O_2 content during calcination yields acatalyst of a stronger acidity and stable NH3 adsorption. Excessive oxidation of NH3 is alsoinhibited with increasing O_2 content during calcination. These two aspects may account for thehigher SCR activity of 47O.