Abstract:

Selective catalytic reduction by NH₃ (NH₃-SCR) has been considered as one of the most efficient and mature techniques to eliminate nitrogen oxides (NO_x) from coal-fired power plants. Therein, catalysts serve as the core of the whole system and study on their molding technology of the catalysts has become a hot topic. More and more attentions have been paid on how to mold a kind of catalysts with excellent deNO_x performance and facile practical application. In this work, molding technology of V₂O₅-WO₃/TiO₂ deNO_x catalysts was studied. Response surface methodology was used to investigate the regression models of mechanical strength and porosity of this kind of catalysts. The effects of pressing pressure and additive amount of PMMA microspheres on mechanical strength and porosity were evaluated and the significant regression models were obtained. High mechanical strength and porosity can be achieved when proper pressing pressure and additive amount of PMMA microspheres were chosen. It was shown by pore size distribution results that nano-micro hierarchical pores were obviously observed on the walls of catalysts. From XRD results, it was indicated that only anatase phase was found, possibly with high-dispersed V₂O₅ and WO₃ species with low contents which cannot be detected. 80-90 m²·g^-1 of surface areas can be obtained for this kind of catalysts by BET results. Micro pores were clearly observed by SEM after the addition of PMMA microspheres, which can increase the available surface area of catalysts, and thus decreasing the amounts and costs of catalysts. The results of activity tests showed that the honeycomb catalysts possessed excellent catalytic activity with high NO_x conversion and N₂ selectivity, which can meet the demands of deNO_x in recent industry.

Key words: selective catalytic reduction, deNO_x, catalyst, response surface methodology, mechanical strength, porosity

摘要：

氨气选择性催化还原技术(NH₃-SCR)是目前燃煤电厂消除氮氧化物(NO_x)最有效、最成熟的方法之一,其中催化剂作为技术体系的核心,其成型技术逐渐成为研究热点。本文针对V₂O₅-WO₃/TiO₂蜂窝式脱硝催化剂的成型工艺,通过响应曲面法对其机械强度和孔隙率进行研究,分别得出压制压力和聚甲基丙烯酸甲酯(PMMA)微球添加量对机械强度和孔隙率的显著回归模型。发现一定的压制压力和PMMA微球的添加可以使得压制而成的蜂窝式脱硝催化剂既能保持较高的机械强度,又能维持高的孔隙率。孔径分布及扫描电子显微镜(SEM)结果表明催化剂壁上存在明显的纳米-微米多级孔。活性测试结果显示:催化剂表现出了优良的NO_x转化率及N₂选择性,满足了目前工业脱硝领域的需求。

关键词: 选择性催化还原, 脱硝, 催化剂, 响应曲面法, 机械强度, 孔隙率