分子筛负载掺杂型氧化钛催化剂制备与性能研究

发布时间：2018-01-22 22:52

  本文关键词： 光催化 溶胶—凝胶法 共掺杂 HZSM-5 甲基橙　出处：《沈阳理工大学》2016年硕士论文　论文类型：学位论文

【摘要】：纳米TiO_2光催化剂因其具有化学稳定性好、无污染、较高的比表面积以及较高的光催化活性等优点,受到广泛关注。但是TiO_2存在禁带较宽(3.2 e V),光响应范围窄,光量子效率低,悬浮态的TiO_2易凝聚、分离回收困难等问题,极大的限制了其在实际中的应用。针对以上存在的问题,本文拟通过单一金属离子掺杂和两种金属离子共掺杂以及负载的方法对TiO_2进行优化改性,以提高TiO_2的光催化效率及回收重复利用率。并利用XRD、SEM、FT-IR、XPS、UV-Vis DRS以及N2吸附-脱附等手段对复合光催化剂进行表征,同时以甲基橙为目标降解物考察不同制备条件对光催化活性的影响。本实验主要分为以下三个部分:1采用溶胶-凝胶法制备x%In-0.1%Gd-TiO_2复合光催化剂。结果表明,所制备的催化剂在不同In掺杂浓度和煅烧温度下均为锐钛矿相,Gd~(3+)、In~(3+)以取代Ti~(4+)的方式进入TiO_2晶格中,使晶格发生畸变,膨胀,导致晶格参数变大。适量的掺杂抑制了TiO_2晶粒的生长,使催化剂平均孔径减小,比表面积增大,3%In-0.1%Gd-TiO_2催化剂的比表面积最大,为122.7 m2/g。同时,掺杂使TiO_2吸收边带发生红移,带隙减小。随着煅烧温度的升高,TiO_2晶粒不断增大,比表面积逐渐减小。当煅烧温度为400 ℃时3%In-0.1%Gd-TiO_2的光催化活性最好,达63%。光照60 min后,3%In-0.1%Gd-TiO_2对甲基橙的降解率达到90%,而0.1%Gd-TiO_2对甲基橙的降解率只有70%。本实验催化剂的最佳投入量为200 mg/L。2采用溶胶-凝胶法合成x%In-0.05%Sm-TiO_2复合材料。结果表明,在不同In掺杂量和煅烧温度下所制备的样品均为锐钛矿相,适量共掺杂抑制了二氧化钛晶粒的生长,使晶粒尺寸减小,TiO_2吸收边界红移,表面羟基数量增加。掺杂增加了催化剂的比表面积,5%In-0.05%Sm-TiO_2催化剂的比表面积最大,为113.1 m~2/g。随着煅烧温度的升高,样品晶粒逐渐增大,比表面积逐渐减小。煅烧温度为400 ℃时,5%In-0.05%Sm-TiO_2具有最强的光催化能力,降解率高达69.8%。光照60 min后,5%In-0.05%Sm-TiO_2对甲基橙的降解率高达97.7%,几乎使甲基橙完全脱色。3以钛酸四丁酯为钛源,HZSM-5分子筛为载体,采用溶胶-凝胶法制备不同负载量的In-TiO_2(x%)/HZSM-5复合光催化剂。结果表明,负载后TiO_2仍保持了锐钛矿晶体结构,负载抑制了TiO_2颗粒的生长,使其晶粒尺寸减小。随着TiO_2负载量的增加,比表面积逐渐减小,In-TiO_2(20%)/HZSM-5的比表面积最大,可达253.3m2/g。由甲基橙光降解实验知,In-TiO_2(50%)/HZSM-5的光催化活性最高,为60%。采用同样的方法制备3%In-0.1%Gd-TiO_2(x%)/HZSM-5,3%In-0.05%Sm-TiO_2(x%)/HZSM-5复合光催化剂。结果表明,与3%In-0.1%Gd-TiO_2,5%In-0.05%Sm-TiO_2相比,负载后光催化活性降低。
[Abstract]:Nanocrystalline TiO_2 photocatalysts have the advantages of good chemical stability, no pollution, high specific surface area and high photocatalytic activity. However, there are some problems in TiO_2, such as wide band gap, narrow optical response range, low optical quantum efficiency, easy aggregation of suspended TiO_2 and difficulty in separation and recovery. In view of the above problems, this paper intends to optimize the modification of TiO_2 by single metal ion doping, two metal ions co-doping and loading methods. In order to improve the photocatalytic efficiency and recycle efficiency of TiO_2. The composite photocatalysts were characterized by UV-Vis DRS and N2 adsorption-desorption. At the same time, the effects of different preparation conditions on photocatalytic activity of methyl orange were investigated. 1Sol gel method was used to prepare x In-0.1 Gd-TiOs _ 2 photocatalyst. The prepared catalyst is anatase phase at different concentration of in doping and calcination temperature. The catalyst enters the TiO_2 lattice in the way of replacing Ti~(4). The crystal lattice is distorted and expanded, and the lattice parameters become larger. Proper doping inhibits the growth of TiO_2 grains, decreases the average pore size and increases the specific surface area of the catalyst. 3In-0.1 and Gd-TiO-2 catalysts have the largest specific surface area of 122.7 m2 / g. At the same time, doping results in red-shift of the absorption sideband of TiO_2. With the increase of calcination temperature, the grain size of TiO2 increases. The photocatalytic activity of 3In-0.1Gd-TiO-2 was the best at the calcination temperature of 400 鈩，

本文编号：1455947