Metal Phosphides Derived from Hydrotalcite Precursors toward the Selective Hydrogenation of Phenylacetylene

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• 作者：Yudi Chen ; Changming Li ; Junyao Zhou ; Shitong Zhang ; Deming Rao ; Shan He ; Min Wei ; David G. Evans ; Xue Duan
• 刊名：ACS Catalysis
• 出版年：2015
• 出版时间：October 2, 2015
• 年：2015
• 卷：5
• 期：10
• 页码：5756-5765
• 全文大小：752K
• ISSN：2155-5435

文摘

We report a new synthetic strategy for the fabrication of several supported nickel phosphides (Ni₁₂P₅, Ni₂P, and NiP₂) with particle size ranging from 5 to 15 nm via a two-step procedure: preparation of supported Ni particles from layered double hydroxide precursors, followed by a further reaction with a certain amount of red phosphorus. The selective hydrogenation of phenylacetylene over these metal phosphides was evaluated, and the as-prepared Ni₂P/Al₂O₃ catalyst shows a much higher selectivity to styrene (up to 88.2%) than Ni₁₂P₅/Al₂O₃ (48.0%), NiP₂/Al₂O₃ (65.9%), and Ni/Al₂O₃ (0.7%) catalysts. EXAFS and in situ IR measurements reveal that the incorporation of P increases the bond length of Ni鈥揘i, which imposes a key influence on the adsorption state of alkene intermediates: as the Ni鈥揘i bond length extends to 0.264 nm, the alkene intermediate undergoes di-蟺(C鈺怌) adsorption, facilitating its desorption and the resulting enhanced selectivity. Moreover, electron transfer occurs from Ni to P, as confirmed by EXAFS, XPS, and in situ CO-IR experiment, in which the positively charged Ni reduces the desorption energy of alkene and thus improves the reaction selectivity.