煤焦油中萘系烃类化合物通过加氢转化为氢化芳烃或环烷烃可显著增强喷气燃料的热安定性，该加氢过程实现的关键在于如何有效研制高选择性芳烃加氢催化剂。针对商业用金属硫化物催化剂尚不足以控制芳烃加氢选择性的问题，Ni2P催化剂因其具有特殊的晶体形貌和电子结构表现出很高的本征加氢活性，有望成为新一代高效芳烃加氢催化剂。但由于非负载型Ni2P催化剂存在比表面积小、活性相分散度、机械强度及散热性不佳的问题，研究者大多借助载体的高比表面积分散活性组分，而不同载体对Ni2P的生成、分散度和催化剂的活性都有着重要影响。因此，采用次磷酸盐歧化法制备了不同SiO2包覆量的Ni2P/Al2O3催化剂(Cat-xSi)以期调变前驱体中镍物种、催化剂中Ni2P与载体之间的相互作用，使得在适宜的载体与金属相互作用下生成更多Ni2P物种并实现更高的分散，同时系统考察了SiO2包覆对Ni2P/Al2O3催化剂结构和萘加氢性能的影响。结果表明:当反应温度为340 ℃，氢气压力为4 MPa，氢油比(反应原料中氢气与3%(质量分数)萘/四氢萘的正癸烷溶液的体积比)为600，重时空速为20.8 h-1时，所有SiO2包覆的Cat-xSi催化剂萘转化率(>65%)均高于未包覆SiO2的催化剂(萘转化率56%)，其中，Cat-16.0Si催化剂的萘转化率为72%，这是因为Cat-16.0Si催化剂中更小的Ni2P颗粒(4.0 nm)和更多的Ni2P数量使得催化剂中暴露出更多活性位点(CO吸附量为26.8 μmol/g)，而稳定存在的缺电子程度更高的Niδ+及催化剂表面更多的B酸位点进一步促进了芳烃的吸附。

The thermal stability of jet fuel could be significantly improved by hydrogenated aromatics or cycloal-kanes,which might be derived from the hydrogenation of naphthalene aromatics existing in coal tar.The key point for realizing this chemical process is to develop a kind of catalyst for aromatics hydrogenation with high selectivity.The commercial metal sulfide catalyst is generally used in this process,but it is hard to control the selectivity of aromatic hydrogenation.In recent year,Ni2P catalysts are found to present application potential in the field of catalytic hydrogenation due to their special crystal structure and electronic property.However,the unsupported Ni2P catalysts generally possess low specific surface area,poor dispersion of active components,less mechanical strength and poor heat dissipation,which result in low activity.Thus,a support is widely employed to disperse Ni2P particles,furthermore,different supports could greatly affect the formation,size distribution and activity of Ni2P.In this study,a series of Ni2P/Al2O3 catalysts with SiO2 coating on Al2O3 surface (Cat-xSi) was prepared using hypophosphite disproportionation method so as to adjust the interaction among Ni species in the precursors,Ni2P and the support,leading to the formation of more Ni2P and higher dispersion of Ni2P.Meanwhile,the influence of SiO2 coating on its structure and hydrogenation performance were investigated.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,all the Cat-xSi catalysts showed a better naphthalene conversion (higher than 65%) than that of Cat-0Si catalyst (56%),which highlights the importance of SiO2 coating.The coating of SiO2 over γ-Al2O3 not only promotes the formation of more Ni2P particles in the Cat-xSi catalyst,but also achieves the better dispersion of Ni2P sites.Furthermore,the SiO2 coating leads to the formation of small-sized Ni2P particles with the more exposed Ni(2) sites and appearance of higher-level electron deficiency of Niδ+ in Ni2P.The Cat-16.0Si catalyst contains more Ni2P particles with smaller size and the stable highest-level electron deficiency of Niδ+,which contribute to a better aromatic hydrogenation activity (72%) than that of the other catalysts in this study.

1 实验部分

   1.1 SiO2-Al2O3载体的制备

   1.2 Ni2P/SiO2-Al2O3催化剂的制备

   1.3 Ni2P/SiO2-Al2O3催化剂结构表征

   1.4 催化剂的活性评价

2 结果与讨论

   2.1 Cat-xSi催化剂微观性质表征

   2.2 Cat-xSi催化剂的活性评价

3 结论