Meng Lingqian, Zhu Xiaochun, Hensen Emiel J M
Inorganic Materials Chemistry, Schuit Institute of Catalysis, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands.
ACS Catal. 2017 Apr 7;7(4):2709-2719. doi: 10.1021/acscatal.6b03512. Epub 2017 Mar 10.
Fe/ZSM-5 nanosheet zeolites of varying thickness were synthesized with di- and tetraquaternary ammonium structure directing agents and extensively characterized for their textural, structural, and catalytic properties. Introduction of Fe ions in the framework of nanosheet zeolites was slightly less effective than in bulk ZSM-5 zeolite. Steaming was necessary to activate all catalysts for NO decomposition and benzene oxidation. The higher the Fe content, the higher the degree of Fe aggregation was after catalyst activation. The degree of Fe aggregation was lower when the crystal domain size of the zeolite or the Fe content was decreased. These two parameters had a substantial influence on the catalytic performance. Decreasing the number of Fe sites along the -direction strongly suppressed secondary reactions of phenol and, accordingly, catalyst deactivation. This together with the absence of diffusional limitations in nanosheet zeolites explains the much higher phenol productivity obtainable with nanostructured Fe/ZSM-5. Steamed Fe/ZSM-5 zeolite nanosheet synthesized using C·Br (domain size in -direction ∼3 nm) and containing 0.24 wt % Fe exhibited the highest catalytic performance. During the first 24 h on stream, this catalyst produced 185 mmol g. Calcination to remove the coke deposits completely restored the initial activity.
采用二元和四元铵结构导向剂合成了不同厚度的Fe/ZSM-5纳米片沸石，并对其织构、结构和催化性能进行了广泛表征。在纳米片沸石骨架中引入铁离子的效果略低于在块状ZSM-5沸石中的效果。需要进行蒸汽处理以激活所有用于NO分解和苯氧化的催化剂。铁含量越高，催化剂活化后铁的聚集程度越高。当沸石的晶畴尺寸或铁含量降低时，铁的聚集程度较低。这两个参数对催化性能有重大影响。沿z方向减少铁位点的数量强烈抑制了苯酚的二次反应，因此也抑制了催化剂失活。这与纳米片沸石中不存在扩散限制一起解释了纳米结构的Fe/ZSM-5可获得更高的苯酚生产率。使用C₄H₉Br合成的（z方向晶畴尺寸约为3 nm）且含有0.24 wt%铁的蒸汽处理后的Fe/ZSM-5沸石纳米片表现出最高的催化性能。在运行的前24小时内，该催化剂产生了185 mmol g。通过煅烧去除焦炭沉积物可完全恢复初始活性。
