Energy Fuels 2009, 23, 4209–4214 Published on Web 07/23/2009
: DOI:10.1021/ef9002523
Preparation of Ni2P/TiO2-Al2O3 and the Catalytic Performance for Hydrodesulfurization of 3-Methylthiophene Kaile Wang, Bolun Yang,* Yu Liu, and Chunhai Yi Department of Chemical Engineering, State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an, Shaanxi 710049, People’s Republic of China Received March 23, 2009. Revised Manuscript Received June 27, 2009
Composite TiO2-Al2O3 supports were prepared by the sol-gel technique using tetra-n-butyl-titanate and γ-Al2O3 as raw materials, and the Ni2P/TiO2-Al2O3 catalysts were obtained by incipient wetness impregnation of aqueous metal phosphate precursors, followed by temperature-programmed reduction of inflowing H2. The supports and catalysts were characterized by X-ray diffraction, infrared spectroscopy, transmission electron microscopy, and N2 adsorption. The hydrodesulfurization (HDS) activity was examined in a fixedbed reactor. Experimental results indicate that the composite support can effectively prevent the formation of aluminum phosphates based on the strong interaction between P and γ-Al2O3, overcome the disadvantage of low surface titania, and improve metal support interaction, which significantly increase catalyst activity and selectivity. The Ni2P/TiO2-Al2O3 catalyst exhibits good activity for the HDS of 3-methylthiophene (3-MT), used as a model compound. The activity and stability of the Ni2P/TiO2-Al2O3 catalyst are affected by the phosphorus content, both achieving a maximum with an initial Ni/P molar ratio of 1:2. The reaction temperature and the weight hourly space velocity (WHSV) show significant influence, but the reaction pressure and the volume ratio of hydrogen/oil have little effect on the HDS performance of the Ni2P/TiO2Al2O3 catalyst. The conversion of 3-MT is close to 100% when the reaction temperature reaches 603 K, reaction pressure reaches 2.0 MPa, WHSV reaches 1.275 h-1, and volume ratio of hydrogen/oil reaches 400.
supports for the preparation of Ni2P as a HDS catalyst in recent years. It can be known from the literature that other supports, such as Al2O3,7 SiO2,8 MCM-41,9,10 HZSM-5,11 KUSY,12 SBA-15,13 active carbon,14 TiO2,15 and SiO2-Al2O3,16 also have been reported as supports of the Ni2P catalysts. Whereas macroporous γ-Al2O3 is widely used as a support of the traditional oil desulfurization catalysts, if macroporous γ-Al2O3 is used as a support of Ni2P catalysts, it is well-known that phosphorus interacts strongly with γ-Al2O3, in many cases resulting in the formation of aluminum phosphates, such as AlPO4, at the surface of the support.17-19 It can cause the
1. Introduction Catalytic hydrodesulfurization (HDS) technology is a main method to reduce the sulfur contents in gasoline and diesel. Traditional HDS catalysts are alumina-supported Mo or W sulfides promoted by Ni or Co. However, because of the introduction of strict environmental laws that require the sulfur contents in the fuel lower than 10 mg/kg,1,2 these HDS catalysts cannot meet the requirement of low-sulfur contents at the new standards. Thus, it is extremely important to develop new HDS catalysts with higher activity. It has been found that metal phosphides are a novel catalyst group for deep hydrotreating and have received much attention because of their high activity in the field of HDS.3-5 Among the metal phosphides studied, the Ni2P catalyst was found to be the most active one in the novel catalyst group.4 However, the surface area of unsupported Ni2P catalysts is rather low (
