铁改性多级孔丝光沸石在缩合胺化反应中的应用

Application of Iron Modified Hierarchical Mordenite in the Condensation Amination Reaction

为了明确铁物种及其分布对缩合胺化反应性能的作用机制,采用浸渍法、沉淀法、水热后处理法制备系列铁改性多级孔丝光沸石,考察其在乙醇胺(MEA)缩合胺化反应合成乙二胺(EDA)中的应用;结合XRD、N_(2)-吸脱附曲线、SEM、TEM、NH_(3)-TPD、Py-IR、UV-Vis等表征手段,探讨了改性方法对Fe物种、物相结构、表面酸性及催化反应性能的影响规律。结果表明,水热后处理法制备的Fe/M-MOR(H)中铁物种主要以孤立八面体Fe、低聚态Fe_(x)O_(y)及纳米Fe_(x)O_(y)簇形态存在,被定向锚定在分子筛外表面和介孔内;孤立八面体Fe会导致B酸酸量增多,B酸与L酸酸量比(B/L)升高,是EDA选择性增加的主要原因;低聚态Fe_(x)O_(y)和纳米Fe_(x)O_(y)簇对缩合胺化具有协同催化作用,有助于反应速控步骤的进行;在温度为310℃,压强为4.0MPa,NH_(3)、MEA和H_(2)O摩尔比为12.5:1:0.3,LHSV=4.58h^(-1)的反应条件下,Fe/M-MOR(H)催化性能最佳,转化率为52.8%,EDA选择性93.6%。

Iron modified hierarchical mordenite was prepared by using impregnation,precipitation,and hydrothermal post-treatment method,and the influence of these mordenites on the selective synthesis of ethylenediamine(EDA)was investigated to determine the catalytic performances of iron species and distribution in condensation amination of monoethanolamine(MEA).The structural,acidic,and catalytic properties of samples were systematically investigated by XRD,N_(2)adsorption/desorption isotherms,SEM,TEM,NH_(3)-TPD,Py-IR,UV-Vis,etc.The results indicate that most iron species of Fe/M-MOR(H)contain extra-framework octahedral Fe species,oligomeric iron species,and iron oxide nanoclusters,which are distributed on the external surface and inside of mesopore channels.The extra-framework octahedral Fe species lead to an increase in B acid sites and amount ratio of B/L,and it is the main reason to enhance the selectivity to EDA.The oligomeric iron species and iron oxide nanoclusters have a synergistic catalysis effect for the selective synthesis of EDA.Based on the suitable iron species and distribution,Fe/M-MOR(H)exhibits better performances than others.The Fe/M-MOR(H)exhibits the best catalytic performance when the reaction temperature is 310℃,pressure is 4.0MPa,NH_(3),MEA and H_(2)O molar ratio is 12.5:1:0.3,and LHSV is 4.58h^(-1),the conversion of MEA is 52.8%and the selectivity to EDA is 93.6%.