Preparation and Characterization of Mesoporous MoO 3 /TiO 2 Composite with High Surface Area by Self-Supporting and Ammo
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Preparation and Characterization of Mesoporous MoO3/TiO2 Composite with High Surface Area by Self-Supporting and Ammonia Method Licheng Li • Yanfang Wang • Kangzhong Shi • Shanshan Chen • Zhuhong Yang • Xiaohua Lu
Received: 28 November 2011 / Accepted: 6 January 2012 / Published online: 22 February 2012 Springer Science+Business Media, LLC 2012
Abstract A mesoporous MoO3/TiO2 composite was prepared from titanate derivative by consecutive self-supporting and ammonia method. All samples were characterized by X-ray Diffraction, N2 adsorption–desorption, Raman Spectra and Field-Emission Scanning Electron Microscopy. The results showed that mesoporous MoO3/ TiO2 composite had a higher surface area (173 m2/g) and a better MoO3 dispersion than that prepared by traditional impregnation (90 m2/g). As for hydrodesulfurization tests, mesoporous MoO3/TiO2 composite in this case presented a better catalytic performance, attributed to its high surface area and good dispersion of MoO3. It can be found that self-supporting played a key role in preparing mesoporous MoO3/TiO2 composite with high surface area. Additionally, aqueous ammonia could effectively dissolve excess MoO3, which helped to obtain mesoporous MoO3/TiO2 composite with better dispersion of MoO3. Keywords Titanium oxide Molybdenum oxide Self-supporting High surface area Hydrodesulfurization
1 Introduction MoO3/TiO2 composites have attracted much attention in many industrial reactions, such as hydrodesulfurization L. Li Y. Wang K. Shi Z. Yang (&) X. Lu State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology, Nanjing 210009, China e-mail: [email protected] S. Chen State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
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(HDS), selective reduction, and isomerization [1–5]. Due to the synergetic effect between TiO2 and molybdenum species, MoO3/TiO2 composites present excellent catalytic performance compared with other molybdenum composites [2, 6, 7]. Furthermore, catalytic efficiency of composites also depends on their structure that is greatly influenced by the preparation process [8–10]. Generally, the composites with high surface area and mesoporous structure are considered to have better catalytic performance, especially in catalytic reactions of large molecules [11, 12]. However, TiO2 usually has a lower surface area (\50 m2/g) than other conventional support materials (such as SiO2 and Al2O3) [13, 14]. This means that the amount of MoO3 species on TiO2 is severely limited. As a result, the activity of MoO3/TiO2 can’t be improved much because of its poor textural properties. To overcome this disadvantage, some efforts have been focused on to improve textural properties by various methods. For instance, good results have been obtained by sol–gel technique [15, 16], although this technique needs to be carried out under strict conditions. Another is template method [17–20], including soft template and hard template. By template method,
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