Preparation and Catalytic Performance of Au/3DOM Co3O4 for the Oxidative Removal of CO and BTX

Preparation and catalytic performance of Au/3DOM Co₃O₄ for the oxidative removal of CO and BTX

 

Yuxi Liu, Jiguang Deng, Hongxing Dai*

Department of Chemistry and Chemical Engineering, College of Environmental and Energy Engineering, Beijing University of Technology, Beijing 100124, PR China. E-mail: hxdai@bjut.edu.cn.

Co₃O₄ is catalytically active for the oxidation of CO and volatile organic compounds (VOCs) ^[1,2]. The Co₃O₄ material with a mesoporous structure possesses high surface area and developed porous structure, hence favoring the improvement in catalytic performance. In recent years, supported gold catalysts attract much attention. The factors, such as Au particle size and support nature, influence the catalytic activities of supported Au catalysts. Here, we report the preparation and catalytic applications of three-dimensionally ordered mesoporous (3DOM) Co₃O₄-supported gold catalysts for the oxidation of CO and BTX (benzene, toluene, and xylene).

3DOM Co₃O₄ and xAu/3DOM Co₃O₄ (x = 3.7-9.0 wt%) catalysts were prepared using the nanocasting strategy with KIT-6 as hard template and bubble-assisted polyvinyl alcohol-protected reduction method^[3] with NaBH₄ as reducing agent, respectively. Techniques, such as XRD, BET, TEM, XPS, and H₂-TPR, were used to characterize the physicochemical properties of the materials, and their catalytic activities were evaluated for the oxidation of CO and BTX. The feedstock was 1% CO + 99% air (space velocity (SV) = 60 000 mL/(g h)) or 1000 ppm BTX + O₂ + N₂ (balance) (SV = 20 000 mL/(g h)).

XRD results indicate that the 3DOM Co₃O₄ and xAu/3DOM Co₃O₄ samples exhibited a cubic crystal structure. The BET surface areas of 3DOM Co₃O₄ and xAu/3DOM Co₃O₄ were 94 and 91-93 m²/g, respectively. TEM results indicate that the 3DOM Co₃O₄ and 6.5Au/3DOM Co₃O₄ samples displayed a good quality of 3DOM architecture, a pore size of ca. 4 nm, and an Au particle size of 2-5 nm°£XPS and H₂-TPR results reveal that the surface Co²⁺/Co³⁺ and O_ads/O_latt molar ratios and low-temperature reducibility of 6.5Au/3DOM Co₃O₄ were higher or better than those of 3DOM Co₃O₄. Catalytic activity evaluation results show that the 6.5Au/3DOM Co₃O₄ sample performed the best, with the T_90% values being -45, 189, 138, and 162 ^oC, lower than those of 3DOM Co₃O₄ by 115, 50, 67, and 39 ^oC, respectively. Therefore, it is concluded that the excellent catalytic performance of 6.5Au/3DOM Co₃O₄ was associated with its larger surface area, developed pore structure, higher oxygen adspecies concentration, and better low-temperature reducibility as well as strong Au-3DOM Co₃O₄ interaction.

The work was financially supported by the NSF of China (Nos. 20973017 and 21077007).

References

[1] X. Xie, Yong Li, Z.Q. Liu, M. Haruta, Wenjie Shen. Nature, 2009, 458, 746-749.

[2] L.H. Hu, Q. Peng, Y.D. Li. J. Am. Chem. Soc., 2008, 130, 16136¨C16137.

[3] M. Comotti, W.C. Li, B. Spliethoff, F. Sch¨ıth. J. Am. Chem. Soc., 2006, 128, 917-924.