助剂Ni与载体的相互作用及其对NiMo/γ-Al_2O_3催化剂加氢脱硫性能的影响

Interaction between Ni promoter and Al_2O_3 support and its effect on the performance of NiMo/γ-Al_2O_3 catalyst in hydrodesulphurization

以γ-Al_2O_3为载体,制备了一系列不同NiO负载量的NiMo/γ-Al_2O_3催化剂,利用XRD、^(27)Al-MAS NMR、Py-FTIR和HRTEM等技术对其进行了表征;在高压微反装置对该系列催化剂的加氢脱硫性能进行了评价,研究了助剂Ni与载体γ-Al_2O_3中不饱和铝间的相互作用及其对催化剂活性相结构形貌和催化活性的影响。结果表明,助剂Ni优先作用于γ-Al_2O_3表面的四配位不饱和铝原子位置;随着NiO负载量的增加,硫化态NiMo/γ-Al_2O_3催化剂中MoS_2活性相的长度变短、堆垛层数增加。Ni的引入能明显提高NiMo/γ-Al_2O_3催化剂的加氢脱硫活性,但其加氢选择性则有所降低。

A series of NiMo/γ-Al2O3 catalysts with different NiO loadings were prepared and characterized by XRD, BET, 27 Al-NMR, Py-IR and HRTEM. The activity of these NiMo/γ-Al2O3 catalysts in the hydrodesulphurization （ HDS） of dibenzothiophene （ DBT） was evaluated in a high pressure micro reactor; the interaction between Ni promoter and γ-Al2O3 support as well as its effect on the nanostructure of active MoS2 phase and HDS performance was then investigated. The results indicate that Ni promoter prefers to interact with the tetra-coordinated unsaturated aluminum sites on the support surface. With the increase of NiO loading, the average number of stacking layers for the MoS2 clusters in the sulfided NiMo/γ-Al2O3 catalysts is increased at the expense of the average length. As the slim MoS2 clusters are more active for the HDS of DBT, the addition of Ni promoter is then effective to enhance the catalytic activity of NiMo/γ-Al2O3 in HDS, but may lead to a slight decrease in the hydrogenation selectivity.