【作者】 薛宝永；

【导师】 徐自力；

【作者基本信息】 吉林大学 ， 环境科学， 2004， 硕士

【摘要】 本文以TiO2和SnO2为大气中半导体的代表，对大气中复合半导体的光催化氧化进行初步研究。分别采用共沉淀工艺和溶胶-凝胶工艺制备了TiO2-SnO2复合半导体，并以庚烷为代表，在C7H16(0.1%)-O2(20%)-N2- TiO2-SnO2体系中考察了利用不同工艺、不同制备条件、不同前驱体制备的复合半导体的光催化活性，优化了复合半导体的制备条件。大量实验的结果表明，采用溶胶-凝胶法制备的样品活性优于共沉淀工艺；在溶胶－凝胶工艺中最佳的制备条件是：以SnCl2·2H2O为引入Sn的前驱体，水解抑制剂HCl的 用量为5.28mL，n(Sn):n(Ti)=0.06，溶胶陈化时间为132h，直接将干凝胶在300℃下焙烧2h。根据制备优化实验确定的溶胶－凝胶工艺的条件，按照大气中Sn和Ti 元素的实际含量范围，制备了一系列不同Sn、Ti比值的TiO2－SnO2复合半导体，并运用TG-DTA、UV-vis、XRD、XPS和红外光谱等手段对它们进行了表征。实验发现，当Sn和Ti比例为0.53以上时，复合半导体获得最佳活性的焙烧温度升高为400℃，这是因为复合SnO2的增多抑制了TiO2的晶型转变。在C7H16(0.1%)-O2(20%)-N2- TiO2-SnO2体系中对同一样品进行多次重复测试，发现其光催化活性没有明显变化。分别探讨了此系列复合半导体对庚烷、甲苯、SO2的光催化降解情况，比较它们的反应速率；并以生成的CO2浓度变化情况为指标，分析了它们对有机物的光催化降解时的矿化情况；最后还对这些反应的动力<WP=83>学进行了初步探讨。对三种污染物的降解研究都表明：不同Sn和Ti比例的复合半导体的光催化活性变化很大，当n(Sn):n(Ti)=0.06时样品活性最好；随着SnO2的复合量的提高，反应活性越来越低，高复合量的比低含量的复合半导体差很多。这是因为一方面，称取催化剂的量保持0.1g不变，造成样品中具有光催化活性的TiO2量随着SnO2的复合量的提高在减少；另一方面，SnO2增多，对样品的光催化活性起到了负面影响也逐渐增强。另外，动力学研究表明，大多数样品催化反应符合一级反应动力学规律，而且活性越好的样品，反应的表观速率常数越大，个别活性非常差的样品催化反应符合零级反应动力学规律。更多还原

【Abstract】 In this paper, we chose TiO2 and SnO2 as the representative semiconductor oxides to study the photocatalytic reactions in the atmosphere. TiO2－SnO2 compound semiconductor was prepared by co-precipitation method and Sol-Gel method. We investigated the photocatalytic activities of samples prepared by different methods and different conditions and different predecessors in the system of C7H16 (0.1%)-O2(20%)-N2-TiO2 by the photocatalytic degradation of heptane. From the repeated experiments, we concluded that activities of samples prepared by Sol-Gel method are better than those of co-precipitation method and the optimal conditions to prepare TiO2-SnO2 compound semiconductor by Sol-Gel method：Use SnCl2·2H2O as the predecessor of Sn; The level of HCl is 5.28mL; n(Sn):n(Ti)=0.06; The aging stage of sol is 132h; Calcinate the dry gel powders at 300℃ for 2h directly.According to the conditions of above and the actual concentration range of Sn and Ti element in the atmosphere, compound semiconductor samples of different Sn/Ti specific values were prepared and they were characterized by XRD 、TG-DTA、UV-vis spectrum、XPS and IR spectrum. Experiment results indicate that when the value of n(Sn)/n(Ti) is higher than 0.53, the best calcination temperature of samples should be 400℃ . This is because excessive SnO2 in the samples can inhibit the transition of TiO2 from undefined structure to anatase phase. In the system of <WP=85>C7H16(0.1%)-O2(20%)-N2- TiO2-SnO2 , the same sample was used for many times and we found the photocatalytic activity of the sample has no change.We studied the photocatalytic degradation of heptane and methylbenzene and SO2 separately, checked the reaction rates; Use the increased concentration of CO2 as the index to assessment the nineralization of heptane and methylbenzene. We also studied the kinetic indexes of those reactions preliminarily. All the degradation reactions of the three pollutants showed that the photocatalytic activities of different samples vary within a large range, the sample of n(Sn):n(Ti)=0.06 has the highest photocatalytic activity and the more SnO2 in compound semiconductor, the lower photocatalytic activity it would be. One reason is the catalyst use level was fixed to 0.1g, so the value of TiO2 will be decreased as the value of SnO2 increased; the other is as SnO2 increased in sample the negative effect for photocatalytic activity increased correspondingly. The results of kinetic analyses showed that most of the reactions match the first-order reaction and the value of the apparent rate constant increased as the photocatalytic activity got higher, a few reactions of samples with low activities match the zero order reaction.更多还原