【作者】 刘重洋；

【导师】 李立清；

【作者基本信息】 湖南大学 ， 环境工程， 2007， 硕士

【摘要】 如何有效地去除氮氧化物是目前空气污染治理的一个重点和难点,催化还原和催化分解时目前研究得比较多的去除氮氧化物的方法,但是这些方法普遍存在工程投资大,运行费用高、能耗高等缺点。已有研究表明:纳米二氧化钛是一种重要的无机物,具有无毒、价廉、光催化性能高等优点,能在紫外光的激发下对氮氧化物污染物进行光催化氧化作用从而将其转化为无毒无害的物质。利用纳米二氧化钛进行的光催化技术已经成为现在研究的主要方向,这对于今后解决大气氮氧化物污染,改善人类的生存环境有着非常深远的意义。本文对TiO2及Zn2+/TiO2纳米薄膜涂敷在载玻片上的制备方法及它们的光催化性能进行了研究。以钛酸四丁酯或者钛酸四丁酯和硝酸锌同为前驱物,利用溶胶凝胶法制备了TiO2以及Zn2+/TiO2溶胶,并采用溶胶体系,以浸渍提拉法对载玻片涂膜,制得均匀透明的TiO2及Zn2+/TiO2薄膜光催化剂。针对气相光催化氧化反应,我们自主设计了一套气固相的光催化反应装置。通过该套反应装置,在反应过程中NO气体能够充分的与光催化剂相接触,并且紫外光能很好的照射进反应装置内部,使得在紫外光的激发下,制备的薄膜光催化剂能充分的与反应装置内部的NO气体发生光催化氧化反应,实验条件考虑的比较充分。本文通过在不同的煅烧温度下(300℃-800℃)制备的TiO2薄膜光催化剂,对NO进行光催化氧化实验,实验表明,不同的煅烧温度能很大程度的影响TiO2薄膜的光催化活性,其中500℃时,TiO2薄膜光催化活性最好,NO去除率为43.2%,之后随着煅烧温度的增加对NO的光催化氧化效果逐渐减弱。对以上不同温度下制备的TiO2薄膜进行XRD检测,从晶型上分析光催化活性差异的原因。为了进一步提高TiO2光催化活性,我们加入硝酸锌作为Zn2+的前驱物,在500℃下煅烧制备出不同Zn2+掺杂浓度的Zn2+/TiO2薄膜光催化剂(2%、4%、6%),并考察了不同Zn2+掺杂浓度的对NO光催化氧化实验影响,通过研究结果表明,Zn2+的加入能较大程度的提高TiO2光催化活性,并且当Zn2+掺杂浓度为4%时对NO的去除率最高。通过SEM以及XRD方法的检测,发现Zn2+的加入能很好的改善TiO2颗粒之间的团聚现象,起到较好分散作用,从而减小粒径尺寸。我们还考虑了薄膜制备过程中的镀膜次数,以及反应过程中氧气含量对NO光催化氧化反应得影响,从而进一步优化实验条件。通过对这两个因素的实验研究发现:我们分别以1次-6次的镀膜次数制备出的4%Zn2+/TiO2薄膜光催化剂进行NO去除实验,实验结果表明当镀膜次数为4次时,对NO的去除率能的达到最高(89%)。另外,在固定其它气体流量而仅改变进气中氧气的进气量时,当进气量为80ml/min时能呈现最高的NO去除率(82.8%)。可见通过这组实验我们得知薄膜的最佳镀膜次数为4次,并且当氧气的最佳进气量为80ml/min。更多还原

【Abstract】 How to remove nitrogen oxides effectively is important and difficult points in the filed of protecting air pollution, catalytic reduction and catalytic decompose have attracted extensive attentions, but all of these technologies have some defects about large investment and high operation cost and high energy consumed. The research found out that nano-titanium dioxide is an important inorganic material, it has some advantages about innocuity, cheapness and high photocatalytic performance, it can remove nitrogen oxides with ultraviolet radiation. Photocatalytic which be used with nano-titanium dioxide has been becoming a major research project. It will be a far-reaching meaning to resolve nitrogen oxides pollution and improve the survival environmental of human race in the future.In this paper, the method of preparing TiO2 and Zn2+/TiO2 nano-film coated on the glass-plate and their photocatalytic performance are investigated. Using Ti(OC4H9)4 or Ti(OC4H9)4 and Zn(NO3)2 as precursor, TiO2 and Zn2+/TiO2 sol are prepared by sol-gel method. Then uniform transparent glass-plate thin film was prepared by dip-coating method.According to the air-solid photocatalytic, we designed a photocatalytic reaction set. In this set, it can be touched enough between NO and photocatalysts, and ultraviolet can also irradiate into the set very well, so that the photocatalysts will react with NO adequately with ultraviolet irradiation.TiO2 film photocatalysts were prepared in different calcine temperature, and were used to reacte with NO, the result showed that different temperature were able to influence TiO2 film’s activity. TiO2 had a good activity when the temperature was 500℃, and the NO removal rate was 43.2%, after 500℃, NO removal rate was decreased with increasing the calcine temperature. XRD was used to analysis the difference within crystal structure.For sake of improve TiO2 photocatalytic reactivity, Zn(NO3)2 was added as Zn2+’s precursor, and we prepared Zn2+/TiO2 photocatalysts which have different doping concentration of Zn2+ in 500℃(2%, 4%, 6%), and we researched the influence to the photocatalytic reactivity with different doping concentration of Zn2+, the result showed that addition of Zn2+ was able to improve TiO2 photocatalytic reactivity and there was a best NO removal rate (89%) when the dope concentration was 4%. SEM and XRD were used to analysis these reason, we found that from the analysis result, addition of Zn2+ had a good disperse ability, so it could improve the reunite phenomenon among TiO2 granules to minish the crystal size of TiO2.We also considered the influence of coating cycles (1 cycle - 6 cycles) and content of O2 to the photocatalytic activity, so that we can optimize the experimental condition. From the results, we found that there was a good NO removal rate of 89% when the coating time was 4 times, and when feed quantity of O2 was 80ml/min, there also revealed a good removal rate of 82.8%.更多还原