Pt-Ru疏水催化剂制备及氢-水液相交换催化性能

Preparation of Pt-Ru Hydrophobic Catalysts and Catalytic Activities for Liquid Phase Catalytic Exchange Reaction

  • 摘要: 用乙二醇为还原剂和碳黑分散溶剂,微波快速加热,1~2 MPa压力下制备了Pt/C和Pt-Ru/C催化剂,用XRD、TEM和XPS对其进行了表征。Pt/C和Pt-Ru/C催化剂活性金属平均粒径为1.9~2.0 nm。随Ru的加入,活性金属粒子的面心立方结构逐渐不明显。Pt-Ru/C中Pt以Pt(0)、Pt(Ⅱ)和Pt(Ⅳ)形式存在,Ru以Ru(0)和Ru(Ⅳ)形式存在。再将Pt/C、Pt-Ru/C催化剂与聚四氟乙烯一起负载于泡沫镍,得到疏水催化剂,研究了其对氢水液相交换反应的催化活性。研究中观察到,Pt中掺入适量Ru可提高单一Pt基疏水催化剂的催化活性。其可能的原因是:水在Pt表面不解离,Pt表面氢气与水间同位素交换通过形成中间体(H2O)nH+(ads)(n≥2)进行,而水在Ru表面会发生解离,Pt-Ru疏水催化剂同时存在另一条反应路径。

     

    Abstract: Pt/C and PtRu/C catalysts with different ratios of Pt to Ru were synthesized, using ethylene glycol as both the dispersant and reducing agent at 1-2 MPa by microwaveassisted method. The catalysts were characterized by XRD, TEM and XPS. The mean particle sizes of the Pt/C and PtRu/C catalysts were 1.9-2.0 nm. Pt and Ru existed as Pt(0), Pt(Ⅱ), Pt(Ⅳ), Ru(0) and Ru(Ⅳ) for Pt-Ru/C catalysts, respectively. The facecentered cubic structure of the active mental particles would be changed upon the addition of Ru gradually. Then polytetrafluoroethylene and carbon supported Pt and Pt-Ru catalysts were supported on foamed nickel to obtain hydrophobic catalysts. The catalytic activity was increased for liquid phase catalytic exchange (LPCE) when uniform Pt based hydrophobic catalysts was mixed into appropriate Ru. Hydrogen isotope exchange reaction occurs between hydration layer (H2O)nH+(ads)(n≥2) and D atoms due to intact water molecules being on Pt surface for LPCE. Water molecules have a tendency to dissociate to OH (ads) and H (ads) on metal Ru surface, and there is the other reaction path for Pt-Ru binary catalysts, which is probably the main reason of the increase of the catalytic activity of the hydrophobic Pt-Ru catalyst.

     

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