焙烧及还原条件对Ni2P/TiO2-Al2O3催化剂加氢脱硫性能的影响

采用溶胶-凝胶法制备了TiO₂-Al₂O₃复合载体, 以柠檬酸(CA)为络合剂采用浸渍法制备了Ni₂P负载的TiO₂-Al₂O₃复合载体催化剂, 并用 X 射线衍射(XRD)、N₂吸附比表面积(BET)测定技术对催化剂的结构和性质进行了表征, 考察了载体焙烧温度、催化剂焙烧温度、还原温度、还原压力对其进行的二苯并噻吩(DBT)加氢脱硫(HDS)性能的影响。结果表明, 升高载体焙烧温度有利于催化剂表面上活性物种的分散, 但焙烧温度过高会导致催化剂烧结, 适宜的载体焙烧温度为550℃。当还原温度为500～550℃时, 磷化镍主要以Ni₁₂P₅相形式存在, 且随着还原温度的升高, Ni₁₂P₅的衍射峰强度逐渐增强, 还原温度为700℃时, 可得到单一的Ni₂P物相。载体焙烧温度为550℃, 催化剂焙烧温度为500℃, 还原温度为700℃, 常压还原制备的Ni₂P/TiO₂-Al₂O₃催化剂具有最好的活性。在360℃、3.0MPa、氢油体积比500、液时体积空速2.0h^-1的条件下, 反应4h时, DBT转化率为99.5 %。

Effect of calcination and reduction conditions on hydrodesulfurization performance of the Ni2P/TiO2-Al2O3 catalyst

The TiO₂-Al₂O₃ complex support was prepared by sol-gel method. A nickel phosphide catalyst, Ni₂P/TiO₂-Al₂O₃ with citric acid (CA) as chelating agent, was prepared by the impregnation method. The catalysts were characterized by X-ray diffraction (XRD) and N₂-adsorption specific surface area measurements (BET). The effects of calcination temperature of support, calcination temperature of catalyst, reduction temperature, reduction pressure and calcination time of catalyst on catalyst activity for dibenzothiophene (DBT) hydrodesulfurization (HDS) were studied. The result showed that increasing the calcination temperature of support favored dispersion of active species on catalyst surface. The optimal calcination temperature of support was 550℃ because of catalyst sintered by excessive temperature. When reduction temperature was in the reange of 500—550℃, the active phase was mixed phases of Ni₁₂P₅ and Ni₂P. The peak intensities of Ni₁₂P₅ increased with the reduction temperature increasing. At reduction temperature of 700℃, the single Ni₂P phase was observed. The Ni₂P/TiO₂-Al₂O₃ catalyst prepared under a support calcination temperature of 550℃, a catalyst calcination temperature of 500℃, a reduction temperature of 700℃ under atmospheric pressure was found to be optimal. At reaction temperature of 360℃, pressure of 3.0MPa, hydrogen/oil ratio of 500 (V/V), and liquid hourly space velocity of 2.0h^-1, the conversion of dibenzothiophene HDS was 99.5% in 4h.