Na+、K+离子交换对Co-Mo/MCM-41加氢脱硫催化剂的影响

 用偏硅酸钠和正硅酸乙酯作硅源制备了MCM-41（分别记作MCM-41(S)和MCM-41(T)）分子筛，并用Na₂C₂O₄和K₂C₂O₄对MCM-41(S)进行了碱金属离子交换改性。以质量分数0.8 %的二苯并噻吩（DBT）的十氢萘溶液为模型化合物，考察了不同MCM-41担载的Co-Mo硫化物催化剂对DBT的加氢脱硫反应性能。结果表明，MCM-41担载的Co-Mo催化剂加氢活性较低，DBT主要通过直接脱硫反应路径脱硫。其活性顺序为：Co-Mo/MCM-41(T)>Co-Mo/MCM-41(S)>Co-Mo/MCM-41(K)>Co-Mo/MCM-41(Na)。UV-Vis结果表明，部分Co与MCM-41(S)中少量Al发生相互作用，生成了CoAl₂O₄，是造成Co-Mo/MCM-41(S)活性降低的重要因素。而在Co-Mo/MCM-41(K)和Co-Mo/MCM-41(Na)中，除CoAl₂O₄物种之外，碱金属的引入还促进了Co₃O₄物种的形成，使其活性进一步降低。

EFFECT OF Na+, K+ ION EXCHANGE ON Co-Mo/MCM-41 HYDRODESULFURIZATION CATALYSTS

Two MCM-41 samples were synthesized using sodium silicate hydrate and tetraethylorthosilicatekinetics as silica source,denoted as MCM-41(S) and MCM-41(T) respectively.MCM-41(S) was then ion exchanged with Na_2C_2O_4 and K_2C_2O_4 to form MCM-41(Na) and MCM-41(K).The hydrodesulfrization(HDS) of dibenzothiophene(DBT) catalyzed by Co-Mo sulfides supported over different MCM-41 samples was studied by using a model fuel containing 0.8% DBT in decalin.The results indicated that Co-Mo sulfides supported over MCM-41 exhibited low hydrogenation activity and the desulfurization of DBT predominately took the route of direct desulfurization(DDS).Both the DDS and HDS activities of Co-Mo catalysts decreased in the same order: Co-Mo/MCM-41(T)>Co-Mo/MCM-41(S)>Co-Mo/MCM-41(K)>Co-Mo/MCM-41(Na).The UV-Vis results suggested that Co may interact with Al contained in MCM-41(S) sample to form CoAl_2O_4,resulting in the HDS activity decrease of Co-Mo/MCM-41(S).The introduction of alkali metal ion into MCM-41(S) also caused the formation of Co_3O_4,which significantly decreases the activity of Co-Mo/MCM-41(K) or Co-Mo/MCM-41(Na).