还原条件对CO_2加氢用Fe/TiO_2催化剂结构的影响  

Influence of Reduction Conditions on Structure of Fe/TiO_2 Catalyst for Hydrogenation of Carbon Dioxide

作　　者：索掌怀[1,2] 寇元[3] 王弘立[3] 

机构地区：[1]烟台大学应用催化研究所 [2]中国科学院兰州化学物理研究所,兰州730000 [3]中国科学院兰州化学物理研究所

出　　处：《催化学报》2001年第4期348-352,共5页

摘　　要：考察了 5 %Fe/TiO2 催化剂在CO2 加氢制低碳烃中的催化活性 .最佳结果显示 ,CO2 转化率为 19 1% ,C2 +烃选择性为 5 0 1% .用X射线粉末衍射、激光拉曼光谱、穆斯堡尔谱及FeK 吸收边扩展X射线吸收精细结构等研究了该催化剂在还原条件下的体相及表面结构 .结果表明 ,在Fe/TiO2 中 ,主要存在超顺磁的Fe0 ,α Fe,配位不饱和的Fe2 +物种及体相FeTiO3.还原温度对Fe/TiO2 催化剂的体相和表面结构及催化性能有显著的影响 .高温还原会破坏催化剂的表面结构 ,导致催化活性显著下降 .将催化活性与体相及表面结构相关联 ,提出Fe0 与配位不饱和的Fe2 +物种之间的协同作用是催化剂显示较高活性的重要原因 .The titania-supported Fe catalyst samples, prepared by incipient wetness impregnation followed by reduction in hydrogen at different temperatures, have higher activity for synthesis of light hydrocarbons from carbon dioxide and hydrogen. The catalytic activity of the catalyst and the product distribution are distinctly affected by the pre-reduction temperature. The best result over 5% Fe/TiO2 reduced in H-2 at 773 K for 5 h shows 19.1% of CO2 conversion with 50.1% of C(2)similar toC(5) selectivity. XRD, laser Raman spectroscopy, Fe-57 Mossbauer spectroscopy and Fe K-edge EXAFS analyses were employed to study the structure of the catalyst. Superparamagnetic Fe-0, alpha -Fe, coordinatively unsaturated Fe2+ (A) cations and the Fe2+ (B) cations in FeTiO3 phase are present in the catalyst, and the catalyst surface is in oxygen-vacancy state. Under an optimum reduction in hydrogen at 773 K for 5 h, the synergy of both zerovalent iron and coordinatively unsaturated Fe2+ (A) cation is thought to be responsible for the higher activity of the catalyst.

关 键 词：氧化钛 氧化铁 二氧化碳 加氢 激光拉曼光谱 斯堡尔谱 扩展X射线吸收精细结构 体相结构 表面结构 负载型催化剂 低碳烃 

分 类 号：O643.3[理学—物理化学]