PbO对V_2O_5/TiO_2催化剂NH_3选择性催化还原NO的影响

THE EFFECT OF PbO ON A V_2O_5/TiO_2 CATALYST FOR SELECTIVE CATALYTIC REDUCTION OF NO WITH NH3

基于铅在中国燃煤和MSW焚烧烟气中的特点,采用静态N_2物理吸附、NH_3化学吸附、程序升温表面反应、傅里叶变换红外光谱和催化剂活性评价的方法,研究了PbO对1 wt.%V_2O_5/TiO_2催化剂NH_3选择性催化还原NO的影响。结果表明,PbO使SCR催化剂活性降低。对于燃煤锅炉,PbO对V_2O_5/TiO_2催化剂的影响可以忽略不计;对于MSW焚烧炉,PbO是使V_2O_5/TiO_2催化剂失活的重要铅化合物。Pb覆盖在TiO_2表面上,与V活性位覆盖在TiO_2表面上的方式类似。催化剂的失活主要是由于PbO中和了催化剂表面Brφnsted酸性位的酸性,Brφnsted酸性位对于NH_3的吸附和活化起重要作用。

Based on the characteristics of lead in flue gas from Chinese coal and MSW-fired plants, the effect of PbO on 1 wt.% V2O5/TiO2 catalyst for selective catalytic reduction of NO with NH3 is studied using static N2 physical adsorption, NHa chemisorption, temperature-programmed surface reaction, Fourier transform infrared spectroscopy and activity measurement. The results show that PbO deactivates the V2O5/TiO2 catalysts. For the V2O5/TiO2 catalysts used in coal-fired plants the effect of PbO can be neglected, while PbO is an important poison for V2O5/TiO2 catalysts in MSW-fired applications. Pb covers the surface of TiO2 sites, similar to active V sites. The deactivation is mainly caused by neutralization of the Brφnsted acid sites on the surface of a V2O5/TiO2 catalyst, which plays a key role on the absorption and activation of NH3.