商业V_2O_5-WO_3/TiO_2烟气SCR脱硝催化剂CaSO_4中毒机理研究

Mechanism of CaSO_4 poisoning commercial V_2O_5-WO_3/TiO_2 catalyst for flue gas selective catalytic reduction of NO_x with NH_3

基于商业V_2O_5-WO_3/Ti O_2脱硝催化剂,设计了两种模拟Ca SO_4中毒的方法,通过比表面积测定(BET)、X射线衍射(XRD)、程序升温还原(H_2-TPR)、扫描电子显微镜(SEM)、原位漫反射傅里叶变换红外光谱(in situ DRIFTS)等表征技术并结合固定床脱硝性能测试平台,对中毒前后催化剂的微观结构、氧化还原能力及表面性质的变化与脱硝活性进行了对比研究,探索硫酸钙中毒机理。研究表明,Ca SO_4会堵塞催化剂孔径,孔径小于2.7 nm和孔径大于17.8 nm时Ca SO_4的影响更大,从而使催化剂的比表面积和孔体积变小;Ca SO_4中毒会导致Brnsted酸位数量和强度的降低,同时Lewis酸强度也会减弱,从而阻碍了NH_3的吸附,Ca SO_4引起催化剂氧化还原能力的降低。

Based on commercial V2O5-WO3 /TiO2 catalyst, two methods to simulate CaSO4 poisoning were designed,and the physico-chemical properties of fresh and poisoned catalysts were investigated by BET specific surface area measurement,X-ray diffraction（ XRD）,H2 temperature-programmed reduction（ H2-TPR）,scanning electron microscope（ SEM） and in-situ diffuse reflectance infrared spectrometry（ in situ DRIFTS）. Meanwhile,the catalytic performance for selective catalytic reduction of NO with NH3（ NH3-SCR） in a fixed bed was also explored comparatively. SEM results show that CaSO4 plugs the small hole（ pore width smaller than 2.7 nm） and big hole（ pore width bigger than 17.8 nm）,causing the loss of surface area and pore volume. CaSO4 could weaken the intensity of both Brnsted acid Sites and Lewis acid sites,particularly the active centers of Brnsted acid sites,which hinders the absorption of NH3 and reduces the redox abilities.