CeTiOx脱硝催化剂的抗硫中毒性能

分别以Ce₂(C₂O₄)₃和Ce(SO₄)₂为Ce前驱体, 采用固相球磨法制备了Ce基选择性催化还原(SCR)脱硝催化剂CeTiO_x-A以Ce₂(C₂O₄)₃为前驱体]和CeTiO_x-B以Ce(SO₄)₂为前驱体]. 将2个催化剂分别在体积分数为0.15%的SO₂的气氛下反应40和60 h, 得到高硫条件下SCR反应后的CeTiO_x催化剂, 分别记为40CeTiO_x-A, 60CeTiO_x-A, 40CeTiO_x-B和60CeTiO_x-B. 考察了反应前后催化剂的NH₃-SCR反应活性. 采用X射线衍射(XRD)、 X射线荧光光谱(XRF)、 比表面积(BET)测试、 H₂程序升温还原(H₂-TPR)、 X射线光电子能谱(XPS)、 NH₃程序升温脱附(NH₃-TPD)及SO₂程序升温脱附(SO₂-TPD)等技术对样品进行了表征. 结果表明, CeTiO_x-A系列催化剂比CeTiO_x-B系列催化剂具有更高的NH₃-SCR反应活性和更好的抗硫抗水性能. 与CeTiO_x-B系列催化剂相比, CeTiO_x-A系列催化剂具有更大的比表面积和孔容, 更多的Ce³⁺和吸附氧(O_α)物种有助于NO的吸附和活化; CeTiO_x-A系统催化剂还具有更多的Lewis强酸性位数量, 可以吸附更多的NH₃分子, 有利于催化剂上NH₃-SCR反应的进行, 提高了CeTiO_x-A系列催化剂的NO转化率.

Sulfur Tolerance of the CeTiOx Catalysts for Selective Catalytic Reduction of NO with NH3†

Ceria-based catalysts(CeTiO_x-A and CeTiO_x-B) were prepared by solid state ball milling method with Ce₂(C₂O₄)₃ and Ce(SO₄)₂ as precursors, respectively. Then, the prepared ceria-based catalysts were treated in reaction atmosphere consisted of 0.15%SO₂ for 40 and 60 h, respectively. The obtained catalysts were designated as 40CeTiO_x-A, 60CeTiO_x-A, 40CeTiO_x-B and 60CeTiO_x-B. The performances of fresh and used catalysts for selective catalytic reduction(SCR) of NO with NH₃ as the reductant were investigated. The catalysts were also characterized using X-ray diffraction(XRD), X-ray fluorescence spectra(XRF), Brunner emmet teller(BET), H₂-temperature programmed reduction(H₂-TPR), X-ray photoelectron spectra(XPS), NH₃-temperature programmed desorption(NH₃-TPD) and SO₂-temperature programmed desorption(SO₂-TPD) techniques. The results indicated that the NH₃-SCR activity, SO₂ and H₂O resistance over the CeTiO_x-A catalysts were better than over the CeTiO_x-B samples. The reasons for this phenomenon are that CeTiO_x-A catalysts possess larger specific surface area and pore volume than CeTiO_x-B catalysts. Besides, CeTiO_x-A catalysts have plenty of Ce³⁺ and the surface adsorbed oxygen, which would benefit the adsorption and activation of NO. Furthermore, CeTiO_x-A catalysts also have numerous strong Lewis acid sites, which lead to the increasing adsorption of NH₃. Therefore, the NH₃-SCR reaction rate and the NO conversion of CeTiO_x-A catalysts was improved.