Cs取代对Ni-H3PW12O40/SiO2催化剂结构性质和催化性能的影响

采用两步浸渍法和载体上的原位反应制备了一系列Cs部分取代的Ni-Cs_xH_3-xPW₁₂O₄₀/SiO₂催化剂,并用N₂吸附比表面积测定(BET)、电感耦合等离子体发射光谱(ICP)、X射线衍射(XRD)、拉曼光谱(Raman)、原位X射线衍射(in situ XRD)、NH₃程序升温脱附(NH₃-TPD)、H₂程序升温还原(H₂-TPR)、H₂程序升温脱附(H₂-TPD)、吡啶吸附傅里叶变换红外(FTIR)光谱等分析测试技术对催化剂进行了表征. 以正癸烷为模型化合物,对催化剂的加氢裂化性能进行了评价. 结果表明,8%Ni-50%Cs_1.5H_1.5PW/SiO₂催化剂具有最高的C₅₊收率,明显优于8%Ni-50%H₃PW/SiO₂催化剂和工业催化剂. 随着Cs 在Cs_xH_3-xPW中比例的增加,正癸烷的转化率逐渐降低,而C₅₊选择性则逐渐提高. 当催化剂具有合适的孔径时,选择性的提高是由于催化剂酸性的减弱,而转化率的降低则是由于催化剂加氢能力的减弱.

Influence of Cs Substitution on the Structural Properties and Catalytic Performance of Ni-H3PW12O40/SiO2 Catalysts

Cs-substituted Ni-Cs_xH_3-xPW₁₂O₄₀/SiO₂ catalysts were prepared by two-step impregnation and in situ reaction on the support. The catalysts were characterized by N₂ adsorption measurements, inductively coupled plasma atomic emission spectrometry, Raman spectroscopy, in situ X-ray diffraction, NH₃-temperature programmed desorption (TPD), H₂-temperature programmed reduction, H₂-TPD, and Fourier transform infrared spectroscopy. The hydrocracking of n-decane was used to study the catalytic performance of the Ni-Cs_xH_3-xPW₁₂O₄₀/SiO₂ catalysts. The highest C₅₊ yield obtained for 8%Ni-50%Cs_1.5H_1.5PW/SiO₂ was superior to those of 8%Ni-50% H₃PW/SiO₂ and an industrial catalyst. The conversion of n-decane slightly decreased and the C₅₊ selectivity increased with increasing Cs content in the Cs_xH_3-xPW catalysts. Ni-Cs_xH_3-xPW₁₂O₄₀/SiO₂ catalysts possessed relatively large pore sizes, so the improved selectivity might have been due to a weaker acidity of the catalysts. The reduced conversion might have been due to a weaker hydrogenation ability.