导　　师： 邓谦

学科专业： 070304

授予学位： 硕士

作　　者： ;

机构地区： 湖南科技大学

摘　　要： 生活和工作环境中存在的各种对身体有毒害作用的挥发性有机污染物,严重影响着人们的身体健康和工作效率。能使污染物能在低成本、低耗能的光催化下消除是一项非常有意义的工作。 /(1/)采用溶胶凝胶法制备N-Fe共掺杂TiO/_2催化剂,以催化剂制备过程中的活化温度、活化时间、铁的掺杂量、氮的掺杂量等影响因子进行正交实验,用紫外光催化消除正丁醇作为探针实验,筛选高催化活性的催化剂。用红外光谱、差热-热重、X-射线衍射、扫描电镜、荧光光谱、氮气吸脱附等表征手段系统研究了催化剂的光谱性质以及结构形态。深入讨论了催化剂的本征性能与其光催化反应活性之间的关系。结果表明:在紫外光照射下,Fe3+含量为0.15/%,N含量为10/%在400℃下活化3h的催化剂对正丁醇的消除效果最好;在正丁醇浓度大于12.1g·m~/(-3/)时,正丁醇在紫外光催化消除过程中有有机副产物乙醛产生,当浓度在12.1 g·m~/(-3/)以下时光催化过程中未检测到有机副产物。 对催化剂光催化消除甲醇、乙醇、丙酮的反应动力学进行了研究。动力学研究表明,在考察温度范围内,催化剂对甲醇、乙醇、丙酮的光催化消除反应均符合一级动力学规律,测得甲醇、乙醇、丙酮的光催化反应活化能分别为50.817 kJ·mol~/(-1/)、24.331 kJ·mol~/(-1/)、18.17kJ·mol~/(-1/)。而且,催化剂在对甲醇、乙醇、丙酮光催化消除时,均可将其完全矿化,反应过程未检测到其他有机副产物的生成。研究表明氮、铁的掺杂一定程度上拓展了二氧化钛的光响应波长范围,增加了其对可见光的吸收强度,从而使其在可见光下也有了一定的光催化活性。在可见光照下,反应温度为66℃,0.15g的催化剂可将初始浓度为0.76 g·m~/(-3/),流速为10mL·min~/(-1/)的丙酮100/%消除,但其可见光催化寿命有限,仅可持续10h左右。在可见光催化反应过程中,随着丙酮浓度的增大,其光催化消除反应的瞬时消除量出现最大值,这说明,底物的浓度对催化剂的光催化光催化活性有一定影响。/(2/)在N-Fe共掺杂TiO/_2催化剂的基础上制备了N-Fe-H3PW12O40共掺杂TiO/_2,对其结构形态进行了表征,以丙酮为底物考察了催化剂的可见光催化活性,实验表明H3PW12O40含量为0.05/%时催化剂的可见光催化活性最好。磷钨酸的引入使得原催化剂在紫外光下失去活性,但可见光催化活性有所提高。磷钨酸降低了光催化反应温度,在其他条件相同的情况下,在反应温度为40℃时即可将1.10 g·m-3丙酮完全矿化,但催化剂寿命缩短,仅可保持7h左右。催化剂本征性能的表征结果表明,磷钨酸的引入,改变了催化剂的表面性状,使得催化剂的比表面积显著增大,吸附性能明显增强。结合光催化实验结果分析可知该催化剂对丙酮的可见光催化的主导反应机制为间接性氧化机制。 /(3/)用水热法制备了CdS掺杂TiO/_2催化剂。用正交试验发考察了各因素对复合催化剂光催化活性的影响的大小,其顺序为:CTAB用量>硫化镉掺杂量>焙烧温度>水热温度>水热时间。各种表征结果表明,此催化剂颗粒细小粒径为6-7nm,具有较大的比表面积和较强的吸附性能。以丙酮、甲醇为底物测试了其光催化反应活性,发现CdS在紫外光催化条件下,其对丙酮的紫外光催化消除活性明显增加,而且在大浓度条件下也较难失活。但CdS掺杂TiO/_2催化剂对甲醇的光催化消除活性相对于纯TiO/_2并未有明显增强,这说明催化剂对丙酮和甲醇的表面作用力存在差别。这种差别的存在导致甲醇紫外光催化反应消除量达到最大值的浓度远小于丙酮。还发现CdS的掺杂未能提高TiO/_2的可见光催化活性。 Toxic volatile organic pollutants in the living and working environment have serious impact on people's health and work efficiency. It is very meaningful job that toxic volatile organic pollutants are photocatalytic eliminated in the lower cost, lower energy consumption. /(1/) N-Fe doped TiO/_2 catalysts are synthesized by sol-gel method. To activation temperature, activation time, iron and nitrogen doped quantity as influence factors design the orthogonal experiment plan. The ultraviolet catalytic elimination n-butanol is used as the probes experiment, screening high catalytic activity catalyst. The spectral properties and the morphology of the catalyst is systematically studied by FT-IR, TG-DTA, XPS, SEM, PL, nitrogen adsorption-desorption. The relationship between the intrinsic properties of the catalyst and its photocatalytic activity has been discussed. The results show that: under UV-irradiation , the composite catalysts doped with Fe3+ /(0.15/%/), N /(10/%/) and activated at 400℃for 3h demonstrate the highest activity. The main products are carbon dioxide and water, but when concentration of n-butanol is higher than 12.1g·m~/(-3/), the organic by-product acetaldehyde is found in the process of photocatalytic eliminating n-butanol. The kinetic behaviors of the photocatalytical elimination of methanol, ethanol and acetone over the N-Fe doped TiO/_2 catalysts have been studied. The results show that in the tested temperature range, the photocatalytical elimination reaction of methanol, ethanol, acetone are all conform to first order reaction. The apparent activation energy of methanol, ethanol, acetone are 50.817 kJ·mol~/(-1/), 24.331 kJ·mol~/(-1/) and 18.17kJ·mol~/(-1/) respectively. Moreover, the methanol, ethanol, acetone can be completely mineralized without by-products. The research show that nitrogen and ferric expand the wavelength range of light response of titanium dioxide and increase its absorption intensity of visible light, which make it has photocatalytical activity under visible light. When the temperature is 66℃, acetone with initial concentration of 0.76g·m~/(-3/) and flow rate of 10.0 mL·min~/(-1/) can be completely eliminated over 0.15g catalysts under the visible light, but only about sustainable 10h. With the increase of acetone concentration in the process of photocatalytic reaction, the instantaneous eliminated amount of the photocatalytic elimination reaction will has a maximum value, which shows that the photocatalytic activity of catalysis is influenced by the substrate concentration in a certain degree. /(2/) The N-Fe-H3PW12O40 doped TiO/_2 catalysts are prepared on the basis of the N-Fe co-doped TiO/_2 catalysts. The visible photocatalytical activity of the catalyst are observed using acetone as the substrate. The results show that visible light photocatalytical activity of the catalysts /(H3PW12O40 0.05/%/) are the best. The catalyst has no photocatalytic activity under UV as the introduction of H3PW12O40, but the photocatalytic activity visible light has increased. Phosphotungstic acid decreases the required photocatalytic reaction temperature. Under the same other conditions, 1.10 g·m~/(-3/) acetone can be mineralized completely at the reaction temperature 40℃, but the catalysts activity can only maintain about 7h. Results of the characterization of intrinsic properties of the catalyst indicate that by introduction of phosphorus acid, the surface characteristics of the catalyst is changed, the catalyst surface area is significantly increased and the adsorption performance is enhanced. The experimental results show that the dominant mechanism of the photocatalytic elimination acetone over this catalyst is the indirect oxidation mechanism. /(3/) CdS doped TiO/_2 mesoporous catalysts were prepared by hydrothermal. The influence factors of photocatalytic activity in the process of catalysts preparation are investigated by orthogonal experiments. The impact factor order is: CTAB amount > the intermingled quantity of CdS > calcination temperature > hydrothermal temperature > hydrothermal time. Various characterization results show that the catalysts have small particle size /(only 6~7nm/), the large surface area and strong adsorption capacity. Photocatalysis activity of acetone and methanol are tested, the results show that the elimination activity of acetone increase significantly under the UV light, and the catalyst can keep it’s its activity even at large substrates concentration. But compare with the pure TiO/_2, the methanol photocatalytic eliminated activity of the CdS doped TiO/_2 catalyst is not significantly increaseed. This phenomenon shows that the interaction force between acetone and catalyst surface is different from which between methanol and catalyst surface. As the existence of this difference, the maximum eliminated concentration of methanol is far less than that of acetone. The tests show that the the catalytic activity of TiO/_2 haven’t been improved by CdS dopping, under the visible light.

关 键 词： 二氧化钛 磷钨酸 硫化镉 掺杂 光催化

分 类 号： [X511]

领　　域： [环境科学与工程]