磷化镍催化剂的制备机理及其加氢脱氮性能

采用热重-质谱联用技术研究了次磷酸盐在氮气中的热分解过程,探讨了次磷酸盐热分解法制备磷化镍的反应机理:次磷酸镍中的Ni²⁺能够"催化"H₂PO₂^-低温发生歧化反应生成PH₃,继而还原Ni²⁺得到Ni₂P。制备了不同负载量的Ni₂P/SiO₂催化剂,用X射线衍射(XRD)、低温N₂吸附-脱附、高分辨透射电镜(HRTEM)等分析技术对催化剂结构进行表征。结果表明,Ni₂P活性组分在SiO₂载体上具有良好的分散性,颗粒粒径为5～8 nm。以喹啉为加氢脱氮模型化合物,在高压微型固定床反应器上对催化剂活性进行评价,在反应温度为360℃、氢气压力为2.0 MPa、液时空速为2.0 h^-1、氢油体积比为500:1时,Ni₂P(20%)/SiO₂催化剂的加氢脱氮率为41.5%。

Preparation mechanism and hydrodenitrogenation performance of nickel phosphide catalyst

Thermal decomposition of nickel hypophosphite precursor into nickel phosphide (Ni₂P) was studied using thermogravimetry-mass spectrometry analysis. The results indicated that nickel ion (Ni²⁺) influenced the decomposition pathway of hypophosphite, because it might catalyze the reaction of hypophosphite to produce PH₃ at lower temperature. Silica-supported Ni₂P catalysts with different loadings were prepared and characterized using X-ray diffraction, N₂ adsorption-desorption, and high resolution transmission electron microscopy. It was indicated that Ni₂P was well dispersed on the support with a particle size of 5～8 nm. The catalytic performance of as-prepared catalysts was evaluated in a fixed-bed reactor for hydrodenitrogenation of quinoline. Under the reaction temperature of 360℃, hydrogen pressure of 2.0 MPa, LHSV of 2.0 h^-1, and H₂/oil volume ratio of 500:1, the conversion of quinoline over Ni₂P(20%)/SiO₂ catalyst reached 41.5%.