摘要
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,Ni_(2)P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Ni_(2)P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Ni_(2)P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SiO_(2)包覆量的Ni_(2)P/Al_(2)O_(3)催化剂(Cat-xSi)以期调变前驱体中镍物种、催化剂中Ni_(2)P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Ni_(2)P物种并实现更高的分散,同时系统考察了SiO_(2)包覆对Ni_(2)P/Al_(2)O_(3)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SiO_(2)包覆的Cat-xSi催化剂萘转化率(>65%)均高于未包覆SiO_(2)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Ni_(2)P颗粒(4.0 nm)和更多的Ni_(2)P数量使得催化剂中暴露出更多活性位点(CO吸附量为26.8μmol/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,Ni_(2)P 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 Ni_(2)P 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 Ni_(2)P particles,furthermore,different supports could greatly affect the formation,size distribution and activity of Ni_(2)P.In this study,a series of Ni_(2)P/Al_(2)O_(3)catalysts with SiO_(2)coating on Al_(2)O_(3)surface(Cat-xSi)was prepared using hypophosphite disproportionation method so as to adjust the interaction among Ni species in the precursors,Ni_(2)P and the support,leading to the formation of more Ni_(2)P and higher dispersion of Ni_(2)P.Meanwhile,the influence of SiO_(2)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 SiO_(2)coating.The coating of SiO_(2)overγ-Al_(2)O_(3)not only promotes the formation of more Ni_(2)P particles in the Cat-xSi catalyst,but also achieves the better dispersion of Ni_(2)P sites.Furthermore,the SiO_(2)coating leads to the formation of small-sized Ni_(2)P particles with the more exposed Ni(2)sites and appearance of higher-level electron deficiency of Niδ+in Ni_(2)P.The Cat-16.0Si catalyst contains more Ni_(2)P 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.
作者
荆洁颖
李泽
杨志奋
王九占
刘道诚
李文英
JING Jieying;LI Ze;YANG Zhifen;WANG Jiuzhan;LIU Daocheng;LI Wenying(State Key Laboratory of Clean and Efficient Coal Utilization,Taiyuan University of Technology,Taiyuan 030024,China)
出处
《煤炭学报》
EI
CAS
CSCD
北大核心
2021年第4期1088-1098,共11页
Journal of China Coal Society
基金
国家自然科学基金资助项目(21978190,22038008)。
关键词
Ni_(2)P
萘加氢
SiO_(2)包覆
次磷酸盐歧化法
nickel phosphide
naphthalene hydrogenation
SiO_(2)coating
hypophosphite disproportionation method
