铈钛复合氧化物催化剂的改性及选择性催化还原NO性能研究

发布时间：2018-05-04 08:00

  本文选题：脱硝 + 选择性催化还原　； 参考：《大连理工大学》2016年硕士论文

【摘要】：随着我国经济的快速发展以及工业化进程的加快,对化石燃料的消耗量不断加大,导致NOx排放量逐年增加,因此引发了严重的大气环境污染。氨选择性催化还原技术被认为是最为有效的去除氮氧化物的方法,而合成低毒性高活性且温度窗口较广的催化剂在脱硝领域越来越受到关注。本文基于铈钛金属氧化物催化剂催化效果的不足,采用浸渍及浸渍-共沉淀联用的方法,在铈钛金属氧化物催化剂的基础上,成功地制备出不同比例的钼铈钛及铈铝钛复合金属氧化物脱硝催化剂,结合比表面积、X-射线光电子能谱、氢气程序升温还原等表征手段以及原位红外分析技术对催化剂的催化活性和物理化学性质进行分析,并对其反应机理进行了探讨。具体研究内容如下：(1)采用浸渍法制备了Mo-Ce-Ti复合氧化物催化剂,并研究了Mo负载量对NH3-SCR活性的影响,对其进行活性测试发现在200～440℃温度范围内25%Mo-Ce-Ti催化剂表现出90%以上的脱硝效率,SCR活性最佳；相较于Ce-Ti催化剂,Mo的掺杂增加了催化剂的氧化还原能力,同时提高了催化剂表面化学吸附氧含量,因而使该催化剂的脱硝性能得到显著增强。(2)在最佳反应温度条件下,对Mo-Ce-Ti体系催化剂进行红外吸附及瞬态反应测试。结果显示Mo的掺杂增加了2.5%Mo-Ce-Ti催化剂表面Lewis酸性位上和Br(?)nsted酸性位上吸附的NH3物种及NH2物种,NH2与气相NO反应生成NH2NO,最终转化为N2和H2O,反应主要遵循E-R机理。(3)采用浸渍-共沉淀法联用制备了Ce-Al-Ti体系催化剂,并研究了Al:Ti掺杂比例对NH3-SCR活性的影响。结果显示Al:Ti摩尔比为1：3的Ce/Al1Ti3催化剂在200～475℃之间可以达到95%以上的NOx转化率。Al与Ti元素的充分掺杂增加了催化剂的比表面积、表面吸附氧含量及反应活性位点,从而提高了该催化剂的脱硝性能。(4)在最佳反应温度条件下,采用原位红外光谱技术研究了Ce/Al1Ti3催化剂的反应机理。相较于Ce-Ti催化剂,Al的掺杂增加了催化剂表面Br(?)nsted酸性位点,使得氨更易吸附在催化剂表面,且生成了反应的主要活性物种-NH2,加速了反应控速步骤的进行。该催化剂表面发生的NH3-SCR反应遵循E-R机理。
[Abstract]:With the rapid development of China's economy and the acceleration of industrialization, the consumption of fossil fuels is increasing, which leads to the increase of NOx emissions year by year, thus causing serious air pollution. Ammonia selective catalytic reduction is considered to be the most effective method to remove nitrogen oxides. However, the synthesis of catalysts with low toxicity and high activity and wide temperature window has attracted more and more attention in the field of denitrification. In this paper, based on the lack of catalytic effect of cerium titanium metal oxide catalyst, the methods of impregnation and impregnation and coprecipitation are adopted, on the basis of cerium titanium metal oxide catalyst. The catalysts for denitrification of molybdenum, cerium, titanium and cerium-aluminum-titanium composite metal oxides have been successfully prepared, and the specific surface area has been determined by X- ray photoelectron spectroscopy. The catalytic activity and physicochemical properties of the catalyst were analyzed by means of hydrogen temperature-programmed reduction and in situ infrared analysis, and the reaction mechanism was discussed. The main contents are as follows: (1) Mo-Ce-Ti composite oxide catalyst was prepared by impregnation method, and the effect of Mo loading on NH3-SCR activity was studied. It was found that the 25%Mo-Ce-Ti catalyst exhibited the best denitrification efficiency and the best catalytic activity in the temperature range of 200 鈩，

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