自蔓延高温燃烧合成法制备CeWTiO_x催化剂及其NH_3-SCR性能

采用自蔓延高温燃烧合成法制备了CeWTiO_x系列催化剂并考察了其氨选择性催化还原NO_x(NH_3-SCR)性能。利用X射线衍射、N_2吸附-脱附、H_2程序升温还原、X射线光电子能谱、NH_3程序升温脱附表征和分析了催化剂晶相、结构、氧化还原能力和酸性强度与其活性之间的关系。结果表明,Ce_(40)W_(10)TiO_x催化剂在150-430℃NO转化率可达80%以上,含硫条件下200℃NO转化率可保持在97%左右。结果表明,该催化剂的低温活性和抗硫性能主要与W的掺杂有关。钨的存在减弱了Ce-O键的强度,降低了CeO2的结晶度和减小了晶粒粒径,增加了催化剂表面活性氧含量和酸量,提高了其性能。

Preparation of CeWTiOx catalysts via self-propagating high temperature synthesis and its NH3-SCR performance

A series of CeWTiO_x catalysts were prepared by self-propagating high-temperature synthesis method, and their NH₃-SCR activities were evaluated. X-ray diffraction, N₂ adsorption-desorption, H₂-temperature-programmed reduction, X-ray photoelectron spectroscopy and NH₃-temperature-programmed desorption were performed to investigate the relationship between the catalyst activity and its physicochemical properties such as crystalline phase, specific surface area, redox ability and acidity. The results showed that 80% of NO conversion could be reached on the Ce₄₀W₁₀TiO_x catalyst sample in a range of 150-430 ℃. NO conversion of Ce₄₀W₁₀TiO_x could be kept above 97% in SO₂ atmosphere. The characterization indicated that the excellent low temperature activity and SO₂ resistance of Ce₄₀W₁₀TiO_x were mainly associated with the tungsten doping. The existence of tungsten weakened the strength of Ce-O bond, lowered the crystallinity and crystal size of CeO₂, increased the surface active oxygen content and the acid sites, thus improved the NH₃-SCR performance of the catalyst.