无模板剂法制备Ce-Zr基多级孔氧化物及其催化脱除VOCs

发布时间：2018-06-09 17:14

  本文选题：Cu-Ce-Zr催化剂 + 催化氧化　； 参考：《天津科技大学》2017年硕士论文

【摘要】：挥发性有机物(VOCs)是造成严重灰霾天气的先导因子,给人体健康和环境带来巨大的危害。催化氧化法是有效降解挥发性有机物的方法之一,而催化剂性能的优劣直接决定着催化降解的效率和运行成本的高低。本文采用不同方法制备了复合氧化物催化剂CuCe0.75Zr0.25Oy和负载型催化剂CuCe0.75Zr0.25Oy/H-ZSM-5,通过 N2低温物理吸脱附、XRD、H2-TPR、NH3-TPD、02-TPD和Raman等手段对催化剂的物理化学等性质进行了表征,以甲苯和/或乙酸乙酯为VOCs目标污染物,在固定床反应器上评价了催化剂的性能,实验结果如下:(1)制备方法对催化剂性能的影响:采用溶胶-凝胶法、热分解法和固相反应法以及浸渍法分别制备了CuCe0.75Zr0.25Oy和CuCe0.75Zr0.25Oy/H-ZSM-5催化剂。结果表明,比表面积是影响负载型催化剂降解VOCs性能的重要因素之一,而比表面积对复合氧化物催化剂活性的影响并不明显。催化剂中体相CuO的存在,减弱了 CuO与Ce02之间的相互作用,降低了催化剂的反应活性。溶胶-凝胶法制备的CuCe0.75Zr0.25Oy催化剂的活性明显高于其它方法制备的催化剂,该催化剂较好的低温还原性和丰富的晶格氧促进了甲苯的催化降解反应,而大的孔径又有利于反应物和产物迁移和扩散,使其T1o (137℃)、T50 (183℃)和T90 (260℃)明显低于其它催化剂;在高温(300℃)72 h的稳定性实验中,未发现失活现象。(2)造孔剂对溶胶-凝胶法制备催化剂性能的影响:通过考察生物基造孔剂细菌纤维素(BC)和化学造孔剂草酸、柠檬酸以及草酸与乙二醇和环己烷混合液对溶胶-凝胶法制备催化剂性能的影响,得到采用生物基造孔剂BC制备的CuCe0.75Zr0.25Oy催化剂呈现出了最好的催化剂活性,甲苯转化率达到100%时的转化温度仅为220℃,明显低于其它催化剂,多级孔结构和高的相对氧空位浓度是催化剂具有高活性的主要原因。(3)细菌纤维素类型对CuCe0.75Zr0.25Oy催化剂性质的影响:以商品BC为造孔剂制备的催化剂(Com-BC)的活性明显高于以培养BC为造孔剂制备的催化剂(Cul-BC),Com-BC催化降解甲苯和乙酸乙酯的完全转化温度分别为220℃和170℃,分别比Cul-BC的低20℃和30℃,在甲苯和乙酸乙酯完全转化温度下对Com-BC进行的100h稳定性实验过程中,未发现失活现象。这主要是由于Com-BC催化剂具有微孔、介孔和大孔的多级孔结构,以及CuO在催化剂表面较好的分散性和较小的晶粒尺寸造成的。
[Abstract]:Volatile organic compounds (VOCs) are the leading factors causing severe haze weather, which bring great harm to human health and environment. Catalytic oxidation is one of the effective methods for the degradation of volatile organic compounds (VOCs), and the performance of the catalysts directly determines the efficiency and operation cost of catalytic degradation. In this paper, composite oxide catalyst CuCe0.75Zr0.25Oy and supported catalyst CuCe0.75Zr0.25Oy / H-ZSM-5 were prepared by different methods. The physicochemical properties of the catalysts were characterized by physical desorption and desorption of XRDX H2-TPRN NH3-TPD02-TPD and Raman at low temperature. Using toluene and / or ethyl acetate as the target pollutants of VOCs, the performance of the catalyst was evaluated in a fixed-bed reactor. The experimental results are as follows: the effect of preparation method on the performance of the catalyst is as follows: Sol-gel method is used. CuCe0.75Zr0.25Oy and CuCe0.75Zr0.25Oy / H-ZSM-5 catalysts were prepared by thermal decomposition, solid state reaction and impregnation, respectively. The results show that the specific surface area is one of the important factors affecting the catalytic performance of the supported catalysts for VOCs degradation, but the specific surface area has no obvious effect on the activity of the composite oxide catalysts. The presence of CuO in the catalyst weakens the interaction between CuO and Ce02 and decreases the catalytic activity of the catalyst. The activity of CuCe0.75Zr0.25Oy catalyst prepared by sol-gel method was obviously higher than that prepared by other methods. The catalytic degradation of toluene was promoted by the catalyst with good low temperature reductivity and abundant lattice oxygen. However, the large pore size is beneficial to the migration and diffusion of reactants and products, which makes the T1O ~ (137 鈩，

本文编号：2000504