ZSM-5/MCM-41介孔硅铝分子筛担载Pd和Pt制备加氢脱硫催化剂

将ZSM-5溶于偏硅酸钠水溶液，以十六烷基三甲基溴化铵作模板剂，用水热合成法自组装合成了具有较强酸性和不同SiO₂/Al₂O₃摩尔比(n(SiO₂)/n(Al₂O₃))的ZSM-5/MCM-41介孔硅铝分子筛（记为ZM(x)，x=n(SiO₂)/n(Al₂O₃)）。以二苯并噻吩（DBT）质量分数为0.8%的十氢萘溶液为模型化合物，考察了Si-MCM-41和ZM(x)担载的Pd和Pt催化剂催化加氢脱硫（HDS）反应的活性。结果表明，担载Pt和Pd不会破坏ZM(x)的介孔结构；DBT在Pd催化剂上主要通过加氢路径脱硫，而在Pt催化剂上则直接脱硫和加氢2条反应路径并重；Si-MCM-41为载体的催化剂HDS活性较低并且失活较快，以ZM(x)为载体的Pd和Pt催化剂加氢活性、加氢脱硫活性、加氢裂化活性及稳定性都有显著提高；ZM(x)担载的Pt和Pd催化剂催化HDS反应的活性可能与其活性组分分散度以及载体的B酸和L酸比例（B/L）有关，具有较好的活性组分分散度和较高B/L比例的ZM(60)担载的Pd和Pt催化剂表现出最佳的加氢脱硫活性和稳定性。

Preparation of Pd and Pt Hydrodesulfurization Catalysts Supported on ZSM-5/MCM-41 Mesoporous Aluminosilicate Molecular Sieves

ZSM-5/MCM-41 mesoporous aluminosilicate molecular sieves with strong acidity and different SiO₂/Al₂O₃ molar ratios (denoted as ZM(x), where x represented the SiO₂/Al₂O₃ molar ratio of the mother liquid) were hydrothermally synthesized by assembling zeolite subunits, which were generated by the hydrolysis of ZSM-5 in a Na₂SiO₃ aqueous solution, in the presence of cetyltrimethylammonium bromide. The hydrodesulfurization (HDS) of dibenzothiophene (DBT) catalyzed by Pd and Pt catalysts supported on Si-MCM-41 and ZM(x) was studied by using a model feed containing 0.8% DBT in decalin. The results indicated that the mesoporous structure of ZM(x) was reserved after the loading of Pd and Pt. HDS of DBT over the supported Pd catalysts occurred mainly through hydrogenation (HYD) pathway, whereas both HYD and direct desulfurization(DDS) pathways played an important role in DBT HDS over the supported Pt catalysts. Si-MCM-41 supported catalysts exhibited low HDS performance and deactivation quickly. The hydrogenation activity, HDS activity, hydrocracking activity and stability of Pd and Pt catalysts were all improved when ZM(x) mesoporous aluminosilicate molecular sieves were used as the supports. The HDS performance of the Pt and Pd catalysts supported on ZM(x) could be affected by the metal dispersion and the ratio of Brønsted acid sites to Lewis acid sits (B/L ratio) of the supports. Therefore, ZM(60) supported Pd and Pt catalysts, which possessed high metal dispersion and B/L ratio, showed the best HDS performance among the catalysts studied.