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甲醛是室内装修污染的重要组分,已严重危害到人们身体健康,在室温条件下消除甲醛引起了人们的广泛兴趣.目前室温清除甲醛主要有物理吸附法、光催化法、等离子体技术及催化氧化技术.物理吸附法主要采用活性炭等作为吸附剂,其初期吸附效果较好,但当吸附饱和之后会重新释放甲醛造成二次污染;光催化法和等离子体技术需要特殊装置,不适合室内室温环境脱除甲醛;而催化氧化技术则可直接将甲醛转化为无毒无害的水和CO2,因而备受关注.Pt/TiO_2被认为是目前消除甲醛最有效的催化剂.为进一步降低贵金属Pt的用量及增强其稳定性(Pt被氧化后其活性会降低),本文首次采用稀土La掺杂锐钛矿型TiO_2,负载少量Pt后用于室内低浓度(0.5 ppm)甲醛的催化氧化.活性测试结果表明,纯TiO_2催化剂上甲醛转化率在5%以下,有可能是物理吸附或可见光催化所致.负载0.5%Pt后,Pt/TiO_2和Pt/La-TiO_2甲醛转化率均高于80%,尤其是La掺杂活性高达96%以上,且在连续反应8 h甚至延长至40 h后其活性均未见下降趋势.电镜结果表明,La掺杂Pt/La-TiO_2催化剂中Pt粒径从未掺杂的2.2 nm降至1.7 nm;CO程序升温脱附测试表明,Pt/La-TiO_2/Pt的分散度达66%,而未掺杂样品仅为51%;X射线光电子能谱测试表明,Pt/La-TiO_2的表面氧物种高于Pt/TiO_2催化剂,说明La掺杂增强了Pt和载体间的相互作用.为探讨Pt/La-TiO_2商业化应用前景,将粉体Pt/La-TiO_2涂覆在堇青石蜂窝陶瓷上制备成整体催化剂.该整体催化剂在容积为2 m3的密室测试中5 min内即可将浓度为0.5 ppm的甲醛将至0.02 ppm以下.该催化剂在存放3个月后活性略有下降,但在10 min内仍可将甲醛浓度降至0.08ppm,达到室内甲醛排放标准.综上,本文成功制备了La掺杂Pt/La-TiO_2用于室内低浓度甲醛催化氧化,该催化剂表现出优异的催化性能.通过多种表征手段表明,La修饰后贵金属Pt纳米粒子尺寸减小、分散度提高及Pt与载体间相互作用增强是其活性优异的主要原因.以Pt/La-TiO_2粉体制备的整体催化剂同样表现出了高的催化性能,具有工业应用前景.
Formaldehyde is an important component of indoor decoration pollution, has seriously endanger people’s health, eliminate formaldehyde at room temperature has aroused widespread interest.Currently there are physical removal of formaldehyde at room temperature adsorption, photocatalysis, plasma technology and catalytic Oxidation technology. Physical adsorption mainly uses activated carbon as adsorbent, the initial adsorption effect is better, but when the adsorption saturation will be re-released formaldehyde secondary pollution; photocatalytic and plasma technology requires special equipment is not suitable for indoor room temperature The environment to remove formaldehyde; and catalytic oxidation technology can directly convert formaldehyde into non-toxic and harmless water and CO2, therefore attracted much attention.Pt / TiO 2 is considered to be the most effective catalyst to eliminate formaldehyde.To further reduce the precious metal Pt Dosage and its stability (the activity of Pt oxidized will be reduced), the first time La-doped anatase TiO 2 with rare earth and a small amount of Pt was loaded for low concentration (0.5 ppm) of indoor formaldehyde oxidation test. The results show that the conversion of formaldehyde on pure TiO_2 catalyst is below 5%, which may be due to physical adsorption or visible light catalysis. After loading 0.5% Pt, Pt / TiO_2 The conversion of Pt / La-TiO 2 formaldehyde was higher than 80%, especially La-doped activity was higher than 96%, and the activity of La / TiO 2 was not decreased after continuous reaction for 8 h or even extended to 40 h.The results of electron microscopy showed that La The Pt particle size decreased from undoped 2.2 nm to 1.7 nm in the doped Pt / La-TiO 2 catalyst. The CO temperature-programmed desorption test showed that the dispersion of Pt / La-TiO 2 / Pt was 66% The results of X-ray photoelectron spectroscopy showed that the surface oxygen species of Pt / La-TiO_2 was higher than that of Pt / TiO_2, indicating that La doping enhanced the interaction between Pt and support. TiO 2 was coated on cordierite honeycomb ceramics to prepare a monolithic catalyst.The bulk catalyst in a volume of 2 m3 chamber test within 5 min to the concentration of 0.5 ppm The formaldehyde will be below 0.02 ppm.The activity of the catalyst decreases slightly after 3 months of storage, but the concentration of formaldehyde can still be reduced to 0.08 ppm within 10 min, which meets the indoor formaldehyde emission standards.In summary, La-doped Mixed Pt / La-TiO 2 is used in the indoor low concentration formaldehyde catalytic oxidation, the catalyst showed excellent catalytic performance.By means of a variety of characterization It is indicated that La-modified Pt nanoparticle decreases in size and dispersion degree and the interaction between Pt and support is the main reason for its excellent activity.The monolithic catalyst prepared by Pt / La-TiO_2 powder also shows high Catalytic performance, with industrial application prospects.