【作者】 张媛；

【导师】 谢峻林；

【作者基本信息】 武汉理工大学 ， 材料学， 2012， 硕士

【摘要】 随着水泥行业的快速发展,水泥窑尾气NOx的排放占NOx总排放的比例不断增大,水泥窑尾气的脱硝迫在眉睫。而低温选择性催化还原(SCR)脱硝技术具有较高的脱硝率和节能的特点,非常适合水泥窑尾气NOx的脱硝。但是,目前研究的低温SCR脱硝催化剂在低温范围内脱硝率不是很高、反应机理及毒化机理还不十分明确,使得低温SCR脱硝技术迟迟未能应用在水泥行业NOx的脱除上。本论文针对以上问题,研究了以P25纳米TiO2为载体,MnOx为活性负载的低温SCR脱硝催化剂的催化性能,并初步探究了其反应机理。本文采用浸渍法制备了一系列以P25纳米TiO2为载体、不同前驱体、不同Mn/Ti和不同焙烧温度的低温SCR脱硝催化剂。通过测试其脱硝率。得到了一种催化活性较好的低温SCR脱硝催化剂,以醋酸锰为载体,Mn/Ti为0.4、焙烧温度为500℃时催化剂的催化活性最好,180℃时脱硝率可以达到91.2%。结合XRD、XPS、TEM和BET等测试手段初步研究了催化剂的反应机理。研究发现,催化剂表面MnOx的存在形式及分散度、比表面积和晶格O浓度等都会影响催化剂的催化活性。此外,还研究了反应空速、O2浓度和NH3浓度等反应参数对催化剂活性的影响,并通过动力学方程计算了催化剂的表观活化能,从能量的角度比较了催化剂活性的优劣。为了进一步提高催化剂的脱硝性能,在制得的催化剂中掺杂过渡金属铁。采用浸渍法制备了以P25纳米TiO2为载体,以MnOx为主要活性组分、以FeOx为活性助剂的复合低温SCR脱硝催化剂。通过脱硝率测试发现：少量的Fe的加入可以很大的提高催化剂的低温催化活性。此外,制备了一系列不同Fe/Ti和不同焙烧温度的复合催化剂,通过测试其脱硝率,得到了最佳掺杂量和最佳焙烧温度。当Fe/Ti为0.05、焙烧温度为500℃时催化剂脱硝率在80℃时可以达到50%以上。结合XRD、BET和TG-DSC等测试手段研究了Fe掺杂和焙烧温度对催化剂活性的影响机理。研究发现,Fe的加入可以使催化剂表面活性主份更加分散,还可以增大催化剂的比表面,使其孔结构更加丰富。此外,Fe的加入还可以与Mn产生协同作用,从而大幅度提高催化剂的低温催化性能。更多还原

【Abstract】 With the rapid development of cement industry, the emission of NOX from the cement exhaust gas accounted for the total emission of NOX increases continuously, and then finding a way to control NOX from cement industry must be solved. Because low-temperature selective catalytic redution(SCR) of NOX has attracted interests for its high catalytic activity and energe efficiency, it is very suitable for cement industry to control NOx.However now the activity of low-temperature SCR catalysts is not very high in low-temperatuer range.Furthermore, the reaction and poison mechanisms are not very clear.These lead the SCR can not been used to control NOX from cement plant. In order to solve these problems,the activity and reaction mechanism of the catalyst which used P25nano TiO2as the carrier and MnOx as the active component was investigated.A series of catalysts with different precursors、ratios of Mn/Ti and calcination temperatues were prepared by impregnation method. And then their catalytic activity were compared to choose the highest. At last, we the best catalyst which used Mn(CH3COOH)2as the precursor the ratio of Mn/Ti as0.4calcinated at500℃was got. The91.2%NOX conversion was obtained at180℃.From the characterization of the catalysts by XRD、XPS、TEM、BET and so on, it was found that axsiting form and dispersion of MnOX、surface area and the concentration of lattice oxygen would effect the catalytic activity. Furthermore, the effects on space velocity、concentration of O2and NH3also were investigated and the kinetic study was used to calculate the activity energe which could compare the activity of catalysts.In order to improve the catalytic activity, the transition metel Fe was added to the catalyst. The catalyst was prepared by impregnation method with used P25nano TiO2as the carrier、MnOX as the active componen and FeOx as the catalytic promoter. It was found that the addition of Fe could deeply improve the catalytic activity. Furthermore, a series of catalysts with diffierent ratios of Fe/Ti and calcination temperatues were prepared to find the best. At last, the best catalyst was been found which had ratio of Fe/Ti as0.05calcinated at500℃, above50%NOX conversion was obtained at80℃.From the characterization of the catalysts by XRD、BET and TG-DSC, it was found that addtion of Fe could improve the nano-structure and the dispersion of the active component, which contributed to higher NO removal. Meanwhile, Fe had the cooperation with Mn which could also improve the catalytic activity.更多还原