Abstract:

In order to improve the resistance of Ce-V-W/Ti catalysts to alkali (earth) metal poisoning, TiO₂ supports were prepared by sol-gel method and then modified by SiO₂ doping, and Ce-V-W/Ti-Si catalysts were prepared by impregnation method. The impregnation method was employed to simulate the poisoning effect on alkali species such as CaCO₃ and K₂O. The influence of SiO₂-modified support on the denitration activity and resistance against alkali metal poisoning of the catalyst was investigated. Characterization techniques including X-ray photoelectron spectroscopy, N₂ adsorption-desorption, H₂-temperature programmed reduction, and NH₃-temperature programmed desorption were employed to analyze the catalysts. Experimental results indicated that the SiO₂ modification of the Ce-V-W/Ti catalyst support reduced its denitration activity at low temperatures but significantly enhanced the catalyst's tolerance against alkali species. Overall, Ce₁V₁W₇/Ti-Si₄ exhibited the best resistance against alkali species, with the poisoning severity of various alkali species ranked as K₂O>Na₂O>CaCO₃>CaO>CaSO₄. The characterization results showed that SiO₂ modification weakened the activity of Ce oxide on the surface of the catalyst, but significantly increased the specific surface area and the number of acidic sites of the catalyst, and protected the reducibility of the active metal oxide during alkalosis.

Key words: selective catalytic reduction, catalyst support, reactivity, SiO₂ modification, alkali poisoning

摘要：

为了提升Ce-V-W/Ti催化剂耐碱（土）金属中毒性能，本文使用溶胶-凝胶法制备了TiO₂载体并进行了SiO₂掺杂改性，通过浸渍法制备了Ce-V-W/Ti-Si催化剂。采用浸渍法模拟了CaCO₃、K₂O等碱物种中毒，探究了SiO₂改性载体对催化剂的脱硝活性和抵御碱（土）金属中毒性能的影响，并使用X射线光电子能谱、N₂吸附-脱附、H₂-程序升温还原、NH₃-程序升温脱附等表征手段对催化剂进行了表征分析。实验结果表明，对Ce-V-W/Ti催化剂载体进行SiO₂改性会降低其中低温段的脱硝活性，但能明显提升催化剂对碱物种的耐受性，总体上，Ce₁V₁W₇/Ti-Si₄对碱物种的耐受性最好，各类碱物种对其脱硝活性的毒害程度为K₂O>Na₂O>CaCO₃>CaO>CaSO₄。表征结果显示，SiO₂改性削弱了催化剂表面Ce氧化物活性，但显著增加了催化剂的比表面积和酸性位点数量，并在催化剂碱中毒时保护了活性金属氧化物的还原性。

关键词: 选择催化还原, 催化剂载体, 活性, SiO₂改性, 碱中毒