Performance of Au/M x O y /TiO 2 Catalysts in Water-Gas Shift Reaction
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Performance of Au/MxOy/TiO2 Catalysts in Water-Gas Shift Reaction Zhen Ma • Hongfeng Yin • Sheng Dai
Received: 7 October 2009 / Accepted: 19 October 2009 / Published online: 30 October 2009 Ó Springer Science+Business Media, LLC 2009
Abstract Our group recently developed a series of Au/ MxOy/TiO2 catalysts for CO oxidation, and demonstrated that some of these catalysts are still active after hightemperature treatment whereas Au/TiO2 deactivates significantly due to the sintering of gold nanoparticles at elevated temperatures (Ma Z, Overbury SH, Dai S (2007) J Mol Catal A 273:97). In the current work, the performance of Au/MxOy/TiO2 (M = Al, Ca, Fe, Zn, Ga, Y, Zr, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Yb) catalysts in water-gas shift (WGS) reaction was evaluated. The influences of different metal oxide (MxOy) additives and pretreatment temperatures were investigated, and the catalyst stability as a function of reaction time on stream was tested. Some of these novel gold catalysts, with high activity and stability in water-gas shift, furnish new possibilities for further fundamental research and industrial development. Keywords Gold catalysis Nanoparticles Titania Metal oxide Water-gas shift Promotion
1 Introduction H2 is a clean, efficient, and sustainable energy carrier and a basic chemical stock [1]. It is industrially produced via steam reforming (CH4 ? H2O ? CO ? 3 H2), partial
Electronic supplementary material The online version of this article (doi:10.1007/s10562-009-0201-y) contains supplementary material, which is available to authorized users. Z. Ma H. Yin S. Dai (&) Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA e-mail: [email protected]
oxidation (CH4 ? 1/2 O2 ? CO ? 2 H2), and coal gasification (C ? H2O ? CO ? H2). CO in the product streams influences the use of H2 in ammonia synthesis and fuel cells due to catalyst poisoning, so water-gas shift (WGS: CO ? H2O ? CO2 ? H2) is integrated [2, 3]. WGS is also crucial to automobile emission control, because the H2 generated on three-way catalysts can remove NOx by reduction. In industry the low-temperature shift is conducted at 160–270 °C using Cu–Zn–Al–O catalysts, and the high-temperature shift is carried out at 300– 450 °C on Fe–Cr–O catalysts [4]. These catalysts need special reduction treatment before reaction, and are sensitive to the exposure to air. With the recent global interest in hydrogen economy, new catalysts for WGS are in active pursuit [5, 6]. Since Haruta et al. reported that supported gold nanoparticles are active for CO oxidation, heterogeneous gold catalysts have found many applications in environmental control, energy-related processes, and chemical synthesis [7–11]. Gold catalysts for WGS include Au/TiO2 [12–14], Au/TiO2/C [15, 16], Au/Fe2O3 [17–23], Au/Fe2O3–ZrO2 [24], Au–Ru/Fe2O3 [25, 26], Au/CeO2 [27–37], Au/CeO2– Al2O3 [38, 39], Au/La–CeO2 [40–43], Au/Gd–CeO2 [44], Au/CeO2–ZrO2 [45–47], Au/ZrO2 [48–50], Au/ThO2 [51], Au/Ca10(PO4)6(OH)2 [52], and Au/zeolites [53]. Nevertheless, ther
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