制备方法对Ni2P/SiO2催化剂结构及萘加氢性能的影响

采用程序升温还原法和次磷酸盐歧化法制备了Ni_2P/SiO_2催化剂,结合现代仪器分析表征技术,研究了制备方法对Ni_2P/SiO_2催化剂结构和萘加氢性能的影响。结果表明,两种方法均可制备出仅含Ni_2P活性相的Ni_2P/SiO_2催化剂,在反应温度340℃、氢气压力4 MPa、空速为20.8 h~(-1)下,程序升温还原法制备的Ni_2P/SiO_2催化剂表现出更高的萘加氢活性,这主要是因为程序还原法制备的Ni_2P/SiO_2催化剂中有更多Ni_2P物种生成,提供了较多的活性位点(CO吸附量21.6μmol/g);且催化剂表面弱酸位点多,有利于芳烃吸附。当选用程序升温还原法制备Ni_2P/SiO_2催化剂时,在保证生成纯相Ni_2P的前提下,较低的Ni/P比更有利于合成高加氢活性的Ni_2P/SiO_2催化剂。

Effect of preparation methods on the structure and naphthalene hydrogenation performance of Ni2P/SiO2 catalyst

Ni₂P/SiO₂ catalysts were prepared by temperature-programmed reduction method and hypophosphite disproportionation method to investigate their naphthalene hydrogenation performance. The prepared catalysts were characterized by ICP-OES, X-ray diffraction, H₂ temperature-programmed reduction, N₂ adsorption-desorption method and transmission electron microscopy, etc. Results showed that Ni₂P/SiO₂ catalyst with pure Ni₂P crystal phase could be successfully prepared by the temperature-programmed reduction method and hypophosphite disproportionation method. When the naphthalene hydrogenation reaction was performed at 340℃, 4 MPa, H₂/oil volume ratio of 600, and a weight hourly space velocity (WHSV) of 20.8 h^-1, Ni₂P/SiO₂ catalyst prepared by the temperature-programmed reduction method possessed superior hydrogenation activity. This result was ascribed to the advantages of temperature-programmed reduction method. It not only installed the higher number of Ni₂P species (CO adsorption amount 21.6 μmol/g) over SiO₂, but also obtained more weak acid sites on the catalyst surface, which promoted the adsorption of aromatic hydrocarbons and subsequently resulted in the higher hydrogenation activity. Furthermore, when the temperature-programmed reduction method was used to prepare Ni₂P/SiO₂ catalyst, the lower Ni/P molar ratio was more beneficial to enhance the naphthalene hydrogenation activity of the as-prepared catalyst.