Studies on the Nature of Catalysis: Suppression of the Catalytic Activity of Leached Pd by Supported Pd Particles during the Heck Reaction

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• 作者：Lin Huang ; Pui Kwan Wong ; Jozel Tan ; Thiam Peng Ang ; Zhan Wang
• 刊名：Journal of Physical Chemistry C
• 出版年：2009
• 出版时间：June 11, 2009
• 年：2009
• 卷：113
• 期：23
• 页码：10120-10130
• 全文大小：657K
• 年卷期：v.113,no.23(June 11, 2009)
• ISSN：1932-7455

文摘

In the Heck coupling of bromobenzene and styrene over conventionally prepared Pd particles supported on SiO₂ at 135 °C under Ar with Na₂CO₃ as the base, the catalysis of 2−4 ppm of leached Pd in solution is considerably affected by the supported Pd particles. Although such low concentration leached Pd alone is very active for the Heck reaction, its catalytic activity is suppressed in the presence of the supported Pd particles. Despite this, the variation of TON with leached Pd concentration follows the same trend of a homogeneous Pd catalyst. Homogeneous catalysis in nature is suggested based on the fact that the solid−liquid reaction rate is dependent on the leached Pd concentration rather than the supported Pd loading. The change of homogeneous catalysis relating to the variation of active Pd fraction in the presence and absence of the supported Pd particles is discussed.