Synthesis and Characterization of Ti-HMS and CoMo/Ti-HMS Oxide Materials with Varying Ti Content
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- 作者：T. A. Zepeda ; J. L. G. Fierro ; B. Pawelec ; R. Nava ; T. Klimova ; G. A. Fuentes ; and T. Halachev
- 刊名：Chemistry of Materials
- 出版年：2005
- 出版时间：August 9, 2005
- 年：2005
- 卷：17
- 期：16
- 页码：4062 - 4073
- 全文大小：236K
- 年卷期：v.17,no.16(August 9, 2005)
- ISSN：1520-5002
文摘
Hexagonal mesoporous materials with wormhole framework structures having Si/Ti molar ratios of80, 40, and 20 (Ti-HMS) were used as supports of CoMo HDS catalysts. The supports and catalystswere characterized by N2 adsorption-desorption (SBET), X-ray diffraction (XRD), UV-vis diffusereflectance spectroscopy (DRS UV-vis), X-ray photoelectron spectroscopy (XPS), 29Si nuclear magneticresonance (29Si NMR), FT-IR of adsorbed NO, and reactivity. The catalysts were tested in the reactionof hydrodesulfurization (HDS) of dibenzothiophene (DBT). The incorporation of titanium into theframework of HMS did not change its mesoporous character but modified the surface properties. Thepresence of Ti impedes the formation of Co2SiO4 and of 
beta2.gif" BORDER=0 ALIGN="middle">-CoMoO4 phases and increases the amount ofoctahedral Co species. The incorporation of titanium into the HMS framework led to an increase in thecatalytic activity in comparison to that of the Ti-free catalyst. All Ti-containing catalysts manifest higheractivity than that of a conventional CoMo/Al2O3 catalyst. The effect of Ti is not linear, the highest activitywas observed for the sample with Si/Ti = 40 atomic ratio. This catalyst demonstrated to be 30% moreactive than the conventional industrial catalyst and 50% more active than the Ti-free catalyst. It is suggestedthat the higher activity of this catalyst is related to the higher value of the Co/Mo ratio in the sulfide stateof the catalysts, to the larger amount of exposed Co species and to the specific degree of sulfidation ofthe Co species, characterized by specific electronic properties, which promote both the DDS and theHYD routes of HDS of DBT. The large pore diameter of this sample should also contribute to theelimination of possible diffusion effects.
beta2.gif" BORDER=0 ALIGN="middle">-CoMoO4 phases and increases the amount ofoctahedral Co species. The incorporation of titanium into the HMS framework led to an increase in thecatalytic activity in comparison to that of the Ti-free catalyst. All Ti-containing catalysts manifest higheractivity than that of a conventional CoMo/Al2O3 catalyst. The effect of Ti is not linear, the highest activitywas observed for the sample with Si/Ti = 40 atomic ratio. This catalyst demonstrated to be 30% moreactive than the conventional industrial catalyst and 50% more active than the Ti-free catalyst. It is suggestedthat the higher activity of this catalyst is related to the higher value of the Co/Mo ratio in the sulfide stateof the catalysts, to the larger amount of exposed Co species and to the specific degree of sulfidation ofthe Co species, characterized by specific electronic properties, which promote both the DDS and theHYD routes of HDS of DBT. The large pore diameter of this sample should also contribute to theelimination of possible diffusion effects.