钼改性页硅酸镍催化剂催化顺酐加氢性能

通过蒸氨法合成了一系列钼改性的页硅酸镍催化剂, 考察了钼含量对催化剂结构及其催化顺酐液相加氢性能的影响. 采用氮气物理吸附-脱附、 X射线衍射(XRD)、 傅里叶变换红外光谱(FTIR)、 透射电子显微镜(TEM)、 氢气程序升温还原(H₂-TPR)、 氨气程序升温脱附(NH₃-TPD)、 吡啶吸附红外光谱(Py-IR)和原位X射线光子能谱(XPS)等手段对催化剂的结构和形貌等进行了表征. 结果表明, 助剂Mo的引入对催化剂结构形貌及其催化性能影响显著. Mo的引入提高了活性金属Ni的还原度, 增加了催化剂表面金属Ni⁰的数量, 金属Ni在还原过程产生氢溢流, 溢流氢将部分MoO₃还原为具有酸性的MoO_x物种, 由于金属Ni⁰与具有Lewis酸(L酸)特性的MoO_x及Ni^σ+的协同效应, 显著提高了催化剂对顺酐C≡C和C≡O的加氢活性. 当Mo含量(质量分数)为3%时, 其催化活性最高, 在160 ℃和5 MPa H₂气条件下, 反应3 h顺酐的转化率为100%, 产物γ-丁内酯的选择性为27%.

Molybdenum Modified Nickel Phyllosilicates Catalyst for Maleic Anhydride Hydrogenation†

A series of molybdenum-modified nickel phyllosilicates was synthesized by ammonia evaporation method. The effects of molybdenum content on the structure and catalytic performance of the catalyst for the liquid phase hydrogenation of maleic anhydride(MA) were investigated. The structure and morphology of the catalysts were characterized by N₂ adsorption-desorption, XRD, FTIR, TEM, H₂-TPR, NH₃-TPD, Py-IR and in situ XPS. The results displayed that the introduction of molybdenum has a remarkable influence on the morphology of the catalysts and its catalytic properties. The reduction degree of the active metal Ni and the sites of Ni⁰ on the surface of the catalysts were increased with the addition of Mo. Meanwhile, the hydrogen spillover was generated during the Ni reduction process. Such overflowing active hydrogen have super reduction ability, which can promote partial of MoO₃ to be reduced to MoO_x species that possesses Lewis acid properties. Due to the synergistic effect between the surface Ni⁰ and the Lewis acid sites induced from partially reduced Ni(Ni^σ+) and MoO_x, the catalytic performance of the catalyst was significantly improved for the hydrogenation of C≡C and C≡O groups in MA. The sample with the Mo doping content of 3% exhibits the highest activity. A 100% conversion of MA together with a γ-butyrolactone(GBL) selectivity of 27% was achieved within 3 h at 160 °C and the H₂ pressure of 5 MPa.