Influence of Supports on Structure and Performance of Nickel Phosphide Catalysts for Hydrodechlorination of Chlorobenzene

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• 作者：Jixiang Chen ; Shaojun Zhou ; Donghui Ci ; Jianxiang Zhang ; Rijie Wang ; Jiyan Zhang
• 刊名：Industrial & Engineering Chemistry Research
• 出版年：2009
• 出版时间：April 15, 2009
• 年：2009
• 卷：48
• 期：8
• 页码：3812-3819
• 全文大小：205K
• 年卷期：v.48,no.8(April 15, 2009)
• ISSN：1520-5045

文摘

SiO₂, TiO₂, γ-Al₂O₃, and HY zeolite supported phosphide catalysts were prepared by the hydrogen temperature-programmed reduction method from phosphate precursors. The physicochemical properties of the catalysts were characterized by means of N₂ adsorption−desorption, hydrogen temperature-programmed reduction, X-ray diffraction, X-ray photoelectron spectroscopy, hydrogen temperature-programmed desorption, inductively coupled plasma atomic emission spectroscopy, energy-dispersion X-ray spectroscopy, and thermal gravimetric analysis. The catalyst performance in the hydrodechlorination of chlorobenzene was evaluated in a fixed-bed reactor at atmospheric pressure. It has been found that the support property remarkably affects the formation of nickel phosphides. With the same Ni/P molar ratio (about 0.7) in the precursors, Ni₂P is prepared on SiO₂ and TiO₂; however, Ni and Ni₃P form on γ-Al₂O₃ and Ni and Ni₁₂P₅ form on HY. This phenomenon is attributed to some phosphorus reacting with γ-Al₂O₃ and HY to form AlPO₄, and the phosphorus reacting with nickel is scarce. Under identical reaction conditions, the hydrodechlorination performance of the catalysts decrease in the order of SiO₂-supported N₂P, γ-Al₂O₃-supported Ni−Ni₃P, TiO₂-supported N₂P, and HY-supported Ni−Ni₁₂P₅. The catalyst performance is closely related to the properties of active phases and hydrogen species. Nickel phosphides have better performance than metallic nickel due to the electron deficiency of nickel, and the spilt-over hydrogen species also contribute to the hydrogenolysis of C−Cl bond. The chlorobenzene conversion exceeds 99% over SiO₂-supported Ni₂P during 130 h at 573 K. The excellent performance is ascribed to the strong poison resistance of Ni₂P to chlorine and the abundant hydrogen species. TiO₂-supported N₂P and HY-supported Ni−Ni₁₂P₅ have good initial activities; however, their deactivation is remarkable, especially HY-supported Ni−Ni₁₂P₅. Their deactivation is mainly owing to the carbonous deposition.