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氟掺杂V2O5TiO2催化剂表面氧物种的EPR研究

时间:2017-05-17 21:57来源:毕业论文
制备了不同F/Ti摩尔比(RF/Ti×100) (0, 0.5, 1, 1.35 和 2)的V2O5/TiO2催化剂用于氨法选择性催化还原氮氧化物。实验发现,氟掺杂的V2O5/TiO2催化剂的活性优于未掺杂改性的
摘要氮氧化物是最主要的大气污染物,我国的氮氧化物90%来自煤炭的直接燃烧产生的烟气。选择性催化还原法是目前最有效地脱除氮氧化物的方法。
制备了不同F/Ti摩尔比(RF/Ti×100) (0, 0.5, 1, 1.35 和 2)的V2O5/TiO2催化剂用于氨法选择性催化还原氮氧化物。实验发现,氟掺杂的V2O5/TiO2催化剂的活性优于未掺杂改性的。
通过XRD, Raman,BET, TEM, H2-TPR,NH3-TPD和EPR表征分析,考察氟掺杂对催化剂的物化性质的影响。结果显示,氟掺杂改善催化剂活性的原因归因于:抑制颗粒增大、抑制锐钛矿向金红石的转化、提高了钒物种的还原能力和氧空位的生成。8788
    用EPR方法对催化剂样品进行了研究,实验表明,氧气能吸附于氧空位上,形成超氧自由基O2-,O2-为活性氧物种,其吸附量及配位环境可与催化活性相关联。
关键词  选择性催化还原;V2O5/TiO2;氟掺杂;超氧自由基
毕业设计说明书(论文)外文摘要
Title Investigation on selective catalytic reduction of NOX by V2O5/TiO2 and their electron spin resonance
Abstract
Nitrogen oxides (NOX) are one of the main pollutants in the atmosphere, and 90% of its emission in our country originates from flue gas due to direct coal combustion. Selective catalytic reduction (SCR), has been shown an effective post-treatment process to eliminate nitrogen oxides.
V2O5/TiO2 catalysts were prepared in the presence of (NH4)2TiF6 with controlled fluorine to titanium molar ratios (RF/Ti×100) (0, 0.5, 1, 1.35 and 2) for selective catalytic reduction of NOX by NH3 (SCR process). It was found that the NOX conversion over F-doping V2O5/TiO2 was greatly improved compared with pure V2O5/TiO2.
The effects of F-doping on the structure of the catalysts were systematically examined using XRD, Raman spectrum, BET, TEM, H2-TPR,NH3-TPD, XPS and EPR. These results showed that F ions were incorporated into TiO2 lattice. The presence of fluorine in the catalysts was confirmed using X-ray photoelectron spectroscopy (XPS). The high catalytic activity was ascribed to several beneficial effects produced by F-doping: preventing the grain growth, inhibiting the phase transformation from anatase to rutile, higher reducibility of dispersed vanadia species, creation of oxygen vacancies, and increase of active sites. It was interesting to point out that the catalytic activity of F-dopingV2O5/TiO2 was achieved by the creation of surface oxygen vacancies. 源自六/维"论\文|网.加7位QQ3249"114 www.lwfree.cn
By using electron paramagnetic resonance (EPR) method, the oxygen adsorbed on the catalysts has been investigated. The EPR results confirm that the oxygen adsorbed to the oxygen vacancies can form superoxide radicals (O2-). The species O2- is the catalytic active one. Its concentration correlates with the catalytic activity.
Keywords:  selective catalytic reduction; V2O5/TiO2; F-doping; superoxide radicals
 目录
1  绪论    1
1.1  课题研究背景    1
1.2  我国能源环境现状及目标    1
1.3  NOX污染危害及现状    2
1.4  煤炭燃烧时NOX生成机理及控制技术    4
1.5  选择性催化还原SCR脱除NOX技术简介    8
1.6  EPR简介    13
1.7  本课题研究目的及内容    14
2  实验部分    15
2.1  主要试剂与仪器    15
2.2  催化剂制备    16
2.3  催化剂活性测定    16
2.4  催化剂的表征方法综述    18
3  催化剂表征结果讨论及分析    18
3.1  XRD分析结果与讨论    18
3.2  Raman分析结果与讨论    20
3.3  SEM测试结果与分析    22 氟掺杂V2O5TiO2催化剂表面氧物种的EPR研究:http://www.lwfree.cn/cailiao/20170517/7247.html
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