Pd模型催化剂上丙烯醛的选择性加氢：温度和粒度效应,Chemistry - A European Journal

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Pd模型催化剂上丙烯醛的选择性加氢：温度和粒度效应
Chemistry - A European Journal ( IF 3.9 ) Pub Date : 2016-09-13 , DOI: 10.1002/chem.201602021
Casey P. O'Brien ₁ , Karl-Heinz Dostert ₁ , Swetlana Schauermann _{1,

2} , Hans-Joachim Freund ₁

Affiliation

Fe ₃ O ₄上丙烯醛加氢的选择性在220–270 K的温度范围内，研究了纳米级Pd负载与纳米尺寸的关系。尽管Pd（111）对所需的C = O键加氢生成丙烯醇显示出近100％的选择性，但发现Pd纳米粒子对该产品的选择性低得多。使用红外反射吸收光谱法对表面物质的原位检测表明，对丙烯醇的选择性主要取决于氧丙基观众分子的形成。虽然在Pd（111）上有效形成了一层氧丙基丙基物种，从而使表面对丙烯醇的形成具有高度选择性，但丙烯醛分解导致CO形成，严重阻碍了该过程对Pd纳米颗粒的形成。我们表明，可以通过改变粒径和反应温度来调节丙烯醛分解的程度。结果，在250 K下，在12 nm Pd纳米颗粒上观察到大量的丙烯醇，而较小的（4和7 nm）纳米颗粒在所研究的任何温度下均未生成丙烯醇。讨论了丙烯形成的粒度依赖性的可能来源。这项工作表明，丙烯醛加氢的选择性受丙烯醛部分加氢到氧丙基表面种类和丙烯醛分解的相对速率的控制，这对合理的催化剂设计具有重要意义。而较小的（4和7 nm）纳米颗粒在任何所研究的温度下均不产生丙烯醇。讨论了丙烯形成的粒度依赖性的可能来源。这项工作表明，丙烯醛加氢的选择性受丙烯醛部分加氢到氧丙基表面种类和丙烯醛分解的相对速率的控制，这对合理的催化剂设计具有重要意义。而较小的（4和7 nm）纳米颗粒在任何所研究的温度下均不产生丙烯醇。讨论了丙烯形成的粒度依赖性的可能来源。这项工作表明，丙烯醛加氢的选择性受丙烯醛部分加氢到氧丙基表面种类和丙烯醛分解的相对速率的控制，这对合理的催化剂设计具有重要意义。

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Selective Hydrogenation of Acrolein Over Pd Model Catalysts: Temperature and Particle‐Size Effects

The selectivity in the hydrogenation of acrolein over Fe₃O₄‐supported Pd nanoparticles has been investigated as a function of nanoparticle size in the 220–270 K temperature range. While Pd(111) shows nearly 100 % selectivity towards the desired hydrogenation of the C=O bond to produce propenol, Pd nanoparticles were found to be much less selective towards this product. In situ detection of surface species by using IR‐reflection absorption spectroscopy shows that the selectivity towards propenol critically depends on the formation of an oxopropyl spectator species. While an overlayer of oxopropyl species is effectively formed on Pd(111) turning the surface highly selective for propenol formation, this process is strongly hindered on Pd nanoparticles by acrolein decomposition resulting in CO formation. We show that the extent of acrolein decomposition can be tuned by varying the particle size and the reaction temperature. As a result, significant production of propenol is observed over 12 nm Pd nanoparticles at 250 K, while smaller (4 and 7 nm) nanoparticles did not produce propenol at any of the temperatures investigated. The possible origin of particle‐size dependence of propenol formation is discussed. This work demonstrates that the selectivity in the hydrogenation of acrolein is controlled by the relative rates of acrolein partial hydrogenation to oxopropyl surface species and of acrolein decomposition, which has significant implications for rational catalyst design.

更新日期：2016-09-13

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