碳纳米管负载Mo-Co-S基HDS/H DN催化剂的制备及其表征研究

用自行制备的多壁碳纳米管(简写为CNTs)作为载体制备负载型Mo-Co-S催化剂,记为:m%MoiCoj/CNTs(m%为质量百分数),用噻吩加氢脱硫(HDS)和吡咯加氢脱氮(HDN)作为探针反应,XRD、XPS和H2-TPD作为表征手段,考察Co/Mo摩尔比、MoiCoj负载量及Co和Mo的浸渍顺序对所制备催化剂的结构和催化性能的影响.研究结果表明,对于本文自行制备CNTs负载的Mo-Co-S催化剂,最佳的Co/Mo摩尔比为1:3,最适宜的Mo3Co1负载量为～7.2%(质量百分数),Co和Mo的浸溃顺序以"先浸渍Co、经干燥焙烧后浸渍Mo"为佳.与AC负载的参比体系相比,CNTs负载催化剂较易于被还原,工作态催化剂表面具有催化活性的Mo物种(Mo4 )在总负载Mo量中所占份额较高;在另一方面,在HDS/HDN反应条件下,作为载体的CNTs的表面存在着数量更加可观的吸附氢物种,这些活泼氢物种通过"溢流"容易传输至Mo-Co-S催化活性位,于是有助于提高表面加氢反应的速率.以上两方面因素对CNTs负载Mo-Co-S催化剂上高的HDS/HDN反应活性都有重要贡献.

Preparation and Characterization of MWCNT-supported Mo-Co-S Catalyst for HDS and HDN

With home-made multi-walled carbon nanotubes(CNTs) as support,CNT-supported Mo-Co-S catalysts,symbolized as m%(mass percentage)Mo_iCo_j/CNTs,were prepared.The effects of Co/Mo molar ratio and Mo_iCo_j-loading amount as well as impregnation sequence of Co and Mo on the catalyst performance were investigated by means of XRD,XPS and H_2-TPD methods and(using) thiophene HDS and pyrrole HDN as probe reactions.The obtained results indicated that the Co/Mo molar ratio at 1:3 and the Mo_3Co_1-loading amount at ~ 7.2(mass)%,as well as the impregnation order of Mo added after Co,were optimal.Compared to the AC support,the CNTs with highly graphitized surface seems to be more effective in mitigating chemical interactions between the supported Mo_iCo_j components and the support to inhibit formation of some of Mo_iCo_j species very stable and difficult to be reduced,so that more Mo~(n+)-species in the total amount of the supported Mo were reduced to the valence-state active catalytically,Mo~(4+),at the surface of the functioning CNT-supported catalyst.On the other hand,the CNT-supported catalyst could reversibly adsorb a greater amount of hydrogen under the reaction condition of HDS and HDN.This helps to generate microenvironments with higher stationary-state concentration of active hydrogen-adspecies on the surface of the functioning catalyst.Both factors mentioned above contributed to the enhancement of the reaction activities of thiophene HDS and pyrrole HDN.