Enhanced Surface And Channel Application Of Catalytic Materials In Hydrotreating Reactions

The production of high-quality and ultra-clean fuel from heavy crude oil is facing tremendous opportunities and challenges in recent years.As one of the key points for hydrotreating,which is one of the most important ways to improve the quality of oil,the optimization of support materials for hydrotreating catalysts has attracted wide attention.In this paper,the traditional industrial alumina and molecular sieve carriers has been redesigned or modified and the research contents are listed as follows:Firstly,a series of nano-alumina support materials with different morphologies were synthesized by a simple and efficient hydrothermal process.The effects of crystal surface exposure of alumina support on the physicochemical properties,active phase structure and hydrodesulfurization activity of the catalysts were investigated.The alumina nanorods support with highest dose of(111)constituent,though low in total surface area,is more active than other counterparts in HDS reactions of thiophene and dibenzothiphene.Characterization of the sulfided NiMo/AN catalyst showed the MoS2 nanoslabs were inclined to develop in the direction along the(111)facet of alumina nanocrystal in reduced stacking layers.The selective exposed of(111)surface played a decisive role in obtaining alumina-supported HDS catalysts with enhanced activity.Secondly,ZSM-5 nanocrystals with uniform distribution of framework Al were successfully synthesized by using using alumina nanorods(AN)as solid aluminium source.The AN with high crystalliniy leads to controlled release of A13+into the liquid phase of the synthesis system.This process can effectively prevent the occurrence of locally excessive amount of A13+in the liquid phase,the as-prepared ZSM-5 samples were nanocrystals with high crystallinity,good structural stability and large surface area,which optimized excellent catalytic performance over n-heptane isomerization reaction than ZSM-5 prepared with traditional aluminium sources.After reaction,the ZSM-5 catalyst with uniform distributed framework Al were selective etched and eventually creating uniformly arrayed pore structure.The hollow structure of the etched zeolite crystals can effectively reflect the carbon deposition position of the ZSM-5 nanocrystals,which in consist with the uniform distribution of framework Al in the zeolite crystals.Finally,hollow ZSM-5 nanocrystals with intact shell were successfully prepared by ammonia etching process,which is convenient to operate under mild conditions.Compared to the TPOAH etching process,hollow ZSM-5 nanocrystals with a similar shell thickness of ca.40 nm were successfully prepared in significantly shortened time.The intermediate products for ammonia etching process were throughly analysized at different time intervals,it is shown that the structure of ZSM-5 nanocrystals is composed of secondary structural units with pyramidal boundary,which is similar to that of ZSM-5 in micron scale.Ammonia etching can be further extended to preparing hollow Silicalite-1 and hollow S-1 encapsulated Pt(Pt@S-1)catalyst.The Pt@S-1 catalyst remains active for toluene hydrogenation with negligible conversion of mesitylene,which certificate the excellent shape selectivity of this encapsulated catalyst.