表面磷酸化CeO2选择性还原NO及其碱金属耐受性

Alkali resistance of denitration catalyst phosphorylated cerium dioxide

摘要:

以Ce(NO3)3·6H2O和(NH4)3PO4·3H2O为原料，采用浸渍法制备了磷酸化CeO2催化剂，并考察了磷酸化CeO2催化剂以NH3为还原剂选择性催化还原NO（NH3-SCR）的脱硝性能。运用XRD、N2吸脱附、XPS、NH3-TPD、原位红外对催化剂的理化性质进行表征。结果表明，磷酸化CeO2催化剂在250~500℃范围内NO的转化率达到了90%以上，且在碱金属和碱土金属中毒后，磷酸化CeO2催化剂在300~400℃范围内NO的转化率仍保持在80%以上。磷酸化CeO2催化性能的增强可归因于酸位点数量的增加，尤其是布朗斯台德酸位点数量的增加，同时提高Ce物种的还原性并产生更多的化学吸附氧。当碱金属沉积在催化剂上时，碱金属将被诱导迁移到磷酸化CeO2的表面与Ce—O—P碱捕获位点结合，从而阻止碱金属攻击Ce活性位点。

Abstract:

Using Ce(NO3)3·6H2O and (NH4)3PO4·3H2O as raw materials, the phosphorylated CeO2 catalysts were prepared by impregnation method, and the denitration performance of phosphorylated CeO2 catalyst for selective catalytic reduction of NO by NH3 as reducing agent (NH3-SCR) was investigated. The physicochemical properties of the catalysts were characterized by XRD, XPS, N2 adsorption-desorption, NH3-TPD and in situ DRIFTS. The results show that the NO conversion rate of the phosphorylated CeO2 catalyst reaches more than 90% in the range of 250~500℃, and the NO conversion rate of the phosphorylated CeO2 catalyst remains above 80% in the range of 300~400℃ after poisoning by alkali metals and alkaline earth metals. The enhanced catalytic performance of phosphorylated CeO2 can be attributed to the increase in the number of acid sites, especially Bronsted acid sites, while improving the reducibility of Ce species and generating more surface adsorbed oxygen. When the alkali metal is deposited on the catalyst, the alkali metal will be induced to migrate to the surface of phosphorylated CeO2 to bind to the Ce—O—P base capture site, thereby preventing the alkali metal from attacking the Ce active site.