富氧条件下Co／ZSM-5催化剂对C3H8选择还原NOx的性能  

Performance of Selective Catalytic Reduction of NO_x by C_3H_8 over Co/ZSM-5 Catalysts under Excess Oxygen

作　　者：刘津[1] 唐富顺[1] 陈彦宏[1] 赵辉[1] 杨宏斌[1] 阮乐[1] 李凝[1] 

机构地区：[1]桂林理工大学化学与生物工程学院,广西矿冶与环境科学实验中心,桂林541004

出　　处：《无机化学学报》2014年第8期1790-1800,共11页Chinese Journal of Inorganic Chemistry

基　　金：广西科学研究与技术开发计划项目(No.12118022-6);桂林理工大学博士基金(No.002401003321)资助项目

摘　　要：采用多种物理化学手段研究了在模拟的轻型柴油车尾气中不同Co担载量及Cu掺杂的Co/ZSM-5催化剂的Co组分分散状态、可还原性、NO吸附脱附性质对C3H8选择性催化还原NOx性能的影响。结果表明,浸渍法制备的Co/ZSM-5催化剂上既有外表面上的Co3+和Co2+物种,也有孔内的Co2+离子。富氧条件下Co/ZSM-5催化剂上C3H8选择性催化还原NOx的活性主要与ZSM-5载体孔外表面分散的CoOx物种中的钴离子可还原能力和NO吸附脱附性能密切相关。Co/ZSM-5催化剂上适宜的Co担载量约为4.0wt%,低担载量时随Co担载量增加,表面CoOx物种中钴离子可还原能力增强,C3H8选择性催化还原NOx的低温转化活性增加;高担载量时,随Co担载量增加,单位Co离子的NO吸附量的减少以及催化剂表面活性中心数的减少,导致了Co/ZSM-5催化剂NOx的转化率和催化剂比速率(k)的下降。孔外表面Co3O4晶体的存在使催化剂表面产生较强的NO吸附,并在高温时有利于C3H8的氧化燃烧,使C3H8选择性催化还原NOx的活性降低。Under the simulated conditions of light-duty diesel vehicles exhaust, the effect of the dispersion state and surface property of supported cobalt on the selective catalytic reduction of NO, by C3Hs （C3Ha-SCR） over Co/ ZSM-5 and Co-Cu/ZSM-5 catalysts was studied by various experimental techniques. The cobalt existed and dispersed on the catalyst external surface in the form of Co3＋ and Co2＋ species, and located in the zeolite channels in the form of Co2＋ cations. The C3Hs-SCR activity of the Co/ZSM-5 catalysts was related to the reducibility, NO adsorption-desorption performance of the cobalt ions in external CoO, species dispersed on the catalyst surface. When Co loading was below 4.0wt%, the increase of Co loading would enhance the reducibility of the cobalt ions of CoO, species and NOx low-temperature conversion; when Co loading was above 4.0wt%, further increase of the Co loading led to the decrease of the ratio of exposed active centers on the surface of catalysts and the decrease of NO adsorption performance per cobalt ion, thus resulting in a decrease of NOx conversion and specific reaction rate at higher temperature. The optimum Co loading for the Co/ZSM-5 catalyst was about 4.0wt%. The formation of external Co304 bulk crystallites generated the strong NO adsorption on the Co/ZSM-5 catalyst and promoted C3H8 oxidizing combustion, and reduced the C3H8-SCR activity at high reaction temperature.

关 键 词：多相催化 氮氧化物 Co ZSM-5催化剂 柴油车尾气 选择性催化还原NOX NO-TPD 可还原性 

分 类 号：O643[理学—物理化学] O643.36[理学—化学]