Abstract:

A series of modified alumina supports with different SiO₂ contents were prepared by neutralization method. NiMo/Al₂O₃ catalysts were obtained by impregnating the modified Al₂O₃ into nickel-molybdenum precursor solution. The catalysts were characterized by XRD, BET, NH₃-TPD, Py-IR, H₂-TPR, HRTEM and XPS. The results showed that the introduction of silicon weakened the metal-support interaction, changed the porous structure and surface acidity of the catalysts. It also improved the active phase dispersion and metal sulfidation, thereby promoted the formation of more Type II NiMoS active phases. With DBT as a model compound, the hydrodesulfurization (HDS) performance of the catalysts were evaluated on a fixed-bed reactor. The reaction activity evaluation results indicated that the introduction of silicon reduced the reaction activation energy of DBT and increased the reaction rate constant, resulting in the increase of the hydrodesulfurization catalysis activity. The comparison of the desulfurization products distribution at DBT conversion of 50% showed that the introduction of silicon significantly affected the reaction selectivity, and the DDS selectivity increased from 83.69% to 92.89%. The characterization conclusions of the catalysts were confirmed by the evaluation results.

Key words: catalyst, silica, NiMo/Al₂O₃, DBT, HDS

摘要：

以中和法合成的不同SiO₂含量的改性氧化铝为载体，本文制备系列Si改性的NiMo/Al₂O₃催化剂，采用X射线衍射（XRD）、N₂物理吸附（BET）、程序升温脱附（NH₃-TPD）、吡啶吸附红外光谱（Py-IR）、程序升温还原（H₂-TPR）、高分辨透射电镜（HRTEM）和X射线光电子能谱（XPS）等分析手段进行详细表征。表征结果显示，引入Si减弱了活性金属与载体之间的相互作用，改善了催化剂的孔结构与表面酸性分布，提高了活性相分散度和金属硫化度，促使形成更多的II类NiMoS活性相。以二苯并噻吩（DBT）为模型化合物，在固定床加氢装置上考察了系列催化剂的加氢脱硫（HDS）性能，结果表明，引入Si可降低DBT的加氢反应活化能，提高反应速率常数，进而提高催化剂的加氢脱硫活性。对比DBT转化率在50%时的脱硫产物分布表明引入Si可影响催化剂的反应路径选择性，直接脱硫路径（DDS）选择性从83.69%增加至92.89%，证实了催化剂的表征规律。

关键词: 催化剂, 二氧化硅, NiMo/Al₂O₃, 二苯并噻吩, 加氢脱硫