TiO2-Al2O3载体的制备方法对其负载的磷化镍催化剂加氢脱氮反应性能的影响

采用共沉淀法和原位溶胶-凝胶法制备了TiO₂-Al₂O₃复合载体，其负载的磷化镍催化剂采用等体积浸渍法和H₂原位还原法制备. 通过N₂吸附（BET）、X射线衍射（XRD）、透射电镜（TEM）、程序升温还原（TPR），X射线光电子能谱（XPS）和等离子体发射光谱（ICP-AES）表征技术对催化剂进行了表征，并通过喹啉的加氢脱氮反应评价了催化剂的加氢脱氮性能. 结果表明，原位溶胶-凝胶法制成的复合载体基本保留了原有的γ-Al₂O₃的孔特征，具有较大的比表面积和较宽的孔分布，TiO₂主要以表面富集的形式分散在管状的γ-Al₂O₃表面，其负载的磷化镍催化剂还原后所形成的活性相为Ni₂P和Ni₁₂P₅；而共沉淀法制成的复合载体比表面积较小，孔径分布更加集中，TiO₂趋于在块状的Al₂O₃表面均匀分散，其负载的磷化镍催化剂具有更好的可还原性，还原后所形成的活性相为Ni₂P. 不同的载体制备方法和不同的钛铝比对催化剂加氢脱氮性能影响较大，当n（Ti）/n（Al）=1/8时，共沉淀法载体负载的催化剂表现出最佳的加氢脱氮性能，在340 ℃，3 MPa，氢油体积比500，液时空速3 h^-1的反应条件下，喹啉的脱氮率可以达到91.3%.

Effect of TiO2-Al2O3 Support Preparation Technique on Hydrodenitrogenation of Ni2P/TiO2-Al2O3 Catalysts

TiO₂-Al₂O₃ composite supports were prepared by in situ sol-gel and co-precipitation methods, and the supported nickel phosphide catalysts were prepared by incipient wetness impregnation and the in situ H₂ reduction method. The catalysts were characterized by X-ray diffraction (XRD), N₂ adsorption (BET), transmission electron microscopy (TEM), temperature-programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), and inductive couple plasma atomic emission spectrometry techniques (ICP-AES). The hydrodenitrogenation (HDN) activity of the supported nickel phosphide catalysts were evaluated on a continuousflow fixed-bed reactor using quinoline as the model molecule. The results showed that the composite support prepared by the in situ sol-gel method basically retained the original pore properties of γ-Al₂O₃ but with a larger surface area and decentralized pore size distribution, and TiO₂ was enriched on the tubular γ-Al₂O₃ surface. The composite support prepared by the co-precipitation method had a smaller surface area and a centralized pore size distribution, and TiO₂ was evenly dispersed on the massive γ-Al₂O₃ surface. The main active phases after reduction were Ni₂P and Ni₁₂P₅ for the catalyst supported on sol-gel prepared TiO₂-Al₂O₃, but only Ni₂P for the catalyst supported on co-precipitated TiO₂-Al₂O₃. Different TiO₂-Al₂O₃ preparation techniques and different Ti/Al atomic ratios had a great effect on the HDN activity of the catalysts. The catalyst supported on co-precipitated TiO₂-Al₂O₃ exhibited better reducibility and HDN activity than the catalyst supported on in situ sol-gel prepared TiO₂-Al₂O₃. The optimal HDN activity occurred for the catalyst supported on co-precipitated TiO₂-Al₂O₃ with an initial Ti/Al atomic ratio of 1:8. At a reaction temperature of 340 ℃, pressure of 3 MPa, hydrogen/oil volume ratio of 500, and liquid hourly space velocity of 3 h^-1, the HDN conversion of quinoline was 91.3%.