本文第三章中以 TiO2/SiO2为光催化剂，在紫外光作用下，讨论了存在NO2时，庚烯在TiO2/SiO2上的吸附和光催化降解的作用。实验结果表明，TiO2/SiO2对庚烯的最大吸附量Mmax=3.10mg，当存在NO2（44.64 μmol/L）时Mmax=3.80mg。另外通过降解40.76 μmol/L 庚烯和163.04 μmol/L 庚烯，在不同的浓度的二氧化氮条件，研究了庚烯的降解和二氧化碳的生成，最后得到二氧化氮与庚烯的摩尔浓度比约为3：1时，庚烯降解速率达到最大。实验通过GC-MS、FT-IR，分别测定了三种不同体系的反应产物，发现C7H15NO2、C6H13ONO2、1,2-C7H14(OH)2、C7H15ONO2、C9H19ONO2等有机物，通过初步分析，已经推理了可能的反应机理。本论文还讨论了氧气和水蒸气不同含量及其光强等对光催化氧化降解庚烯与二氧化氮的影响。随着氧气含量增加，反应速率不断增大，氧量增至5％时，速率最大并趋于稳定。水分子含量对甲苯反应速率的影响也有最佳值15%（相对湿度）。甲苯反应速率随光强增加而增大。最后研究了光催化剂的失活，得到此种方法合成的催化剂有很好的反应耐受性。
The environmental pollution is getting worse day by day because of the rapid development of modern industry, especially the atmospheric pollution causing by NOx and VOCS, which has become the environmental protection question many countries urgent to solve. At present, people already have done some researches on photocatalysis degradation of micro-noxious gas in the atmosphere. In 1972, Fujishima discovered the photocatalytic splitting of water on TiO2 electrodes. This event marked the beginning of a new era in heterogeneous photocatalysis. In recent years, applications to environmental cleanup have been one of the most active areas in heterogeneous photocatalysis. This is inspired by the potential application of semiconductor metal oxides and sulfides photocatalysts for the entire destruction of organic compounds in polluted air and wastewaters. TiO2, ZnO, Fe2O3, WO3, CdS, etc, are semiconductors, Under illumination by photons of greater than band-gap energies, the valence band electrons can be excited to the conduction band, creating highly reactive electron-hole pairs. After migration to the solid surface, these may undergo electron-transfer processes with adsorbates of suitable redox potentials. At present, there are some researches on photocatalytic degradation of volatility organics, and the products are CO2 and H2O. The organics are transformed to N2 or NO3- when photocatalytic degradation of NOX. But studies involving heptheptence and NO2 photocatalysis are relatively few. In this paper, the reaction between heptheptence and NO2 is studied.
In this paper, firstly we prepare the TiO2-SiO2 catalyst by using a sol-gel method. Firstly we studied the effect of SiO2 concentration and TiO2-SiO2calcination temperature. The results showed that the catalyst with little particle size, uniform distributing, and good dispersing was gained after adding SiO2, all of this advantages will increase the catalyzing activity. But the unformed catalyst that lack of activity will be made if adding too much SiO2. Hence through a series experiments we conclude the highest catalyst activity would be achieved when about 9.1 % SiO2 was added. The heat stability was improved in evidence when SiO2 was added. The defect of body appearance will be eliminated effectively, the transformation of crystal type will be restrained and the surface area will be reduced obviously under the process of calcination. Hence through the degradation experiment we achieved the best calcinations temperature was 600℃.
In this paper, the adsorption and photocatalytic degradation of heptheptence over TiO2/SiO2 photocatalyst with the aid of UV light were investigated carefully in the presence of NO2. The experiment data indicated that Mmax (the maximum adsorption amount of TiO2/SiO2 towards heptheptence) is 3.10 mg, and is increased to 3.80mg in the presence of NO2（44.64 μmol/L）. In the photocatalytic reaction process of heptheptence (40.76 μmol/L and 163.04 μmol/L), the degradation of heptheptence and creation of CO2 under different NO2 concentrations, the results indicated that when initial concentration of CO2 was equal to 3 times initial concentration of heptheptence (3:1), the degradation of heptheptence was the best. Through GC-MS and FT-IR we respectively determined the intermediate products of three different reaction systems, such as the organic matters C7H15NO2、C6H13ONO2、1,2-C7H14(OH)2、C7H15ONO2、C9H19ONO2 et al., and accordingly deduced the possible reaction mechanism.
In this paper, we also studied the effects of different oxygen and vapor concentration on photocatalyst degradation heptheptence and NO2. The reaction speed increased along with the increase of oxygen concentration. Especially when the oxygen concentration was 5％ the speed was the most and close to steady. The best concentration of vapor was 15% that influenced CH3-C6H6 reaction speed. The reaction speed of CH3-C6H6 was increased along with the increase of light strength. Finally the activity losing and regeneration was investigated, and the results showed the synthetic catalyst possess outstanding reaction enduring characteristic.