Preparation of Au/Mg_xAlO hydrotalcite catalysts for CO oxidation

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• 作者：Ching-Tu Chang ; Biing-Jye Liaw ; Ching-Tsuen Huang ; Yin-Zu Chen
• 关键词：CO oxidation ; Catalyst preparation ; Gold catalysts ; Hydrotalcite ; Mg_xAlO
• 刊名：Applied Catalysis A ; General
• 出版年：2007
• 期刊代码：4_0926860x
• 类别：ch
• 出版时间：20 November 2007
• 卷：332
• 期：2
• 页码：216-224
• 文件大小：1141 K

摘要

Gold catalysts of CO oxidation, supported on a solid base of Mg_xAlO (x = Mg/Al molar ratio) hydrotalcite, were prepared by a modified deposition precipitation method. The effect of various parameters that are involved in the preparation of catalysts were studied, including the pH and the concentrations of HAuCl₄ in the initial solution, the Mg/Al molar ratio and the calcination temperature of the Mg_xAlO support as well as the calcination temperature of the Au/Mg_xAlO catalyst. The catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet–visible (UV–vis) and X-ray photoelectron spectroscopy (XPS) analyses. The pH and the HAuCl₄ concentrations in the initial solution, and the Mg/Al molar ratio of Mg_xAlO affected the pH in the final solution, and determined the real gold loading in the resulting catalyst. The calcination temperatures of the Mg_xAlO support and the Au/Mg_xAlO catalyst dominated the ratio of gold states (Au³⁺/Au⁰) on the catalyst. The optimal catalyst, 2%Au/Mg₂AlO(100), was obtained using the following preparation parameters: (1) 1 × 10⁻³ M HAuCl₄, (2) pH 2 (without adjusting pH) in the initial solution, (3) Mg/Al = 2 (Mg₂AlO) calcined at 100 °C as a support and (4) 2%Au/Mg₂AlO catalyst calcined at 100 °C. This investigation confirms that not only gold loading of the catalyst is important, the ratio of gold states (Au³⁺/Au⁰) is also critical in determining the activity of the catalyst for CO oxidation.