Department of Chemical and Biological Engineering, Tufts University, Medford, MA 02155, USA.
Phys Chem Chem Phys. 2013 Aug 7;15(29):12187-96. doi: 10.1039/c3cp51538a. Epub 2013 Jun 24.
We report a novel synthesis of nanoparticle Pd-Cu catalysts, containing only trace amounts of Pd, for selective hydrogenation reactions. Pd-Cu nanoparticles were designed based on model single atom alloy (SAA) surfaces, in which individual, isolated Pd atoms act as sites for hydrogen uptake, dissociation, and spillover onto the surrounding Cu surface. Pd-Cu nanoparticles were prepared by addition of trace amounts of Pd (0.18 atomic (at)%) to Cu nanoparticles supported on Al2O3 by galvanic replacement (GR). The catalytic performance of the resulting materials for the partial hydrogenation of phenylacetylene was investigated at ambient temperature in a batch reactor under a head pressure of hydrogen (6.9 bar). The bimetallic Pd-Cu nanoparticles have over an order of magnitude higher activity for phenylacetylene hydrogenation when compared to their monometallic Cu counterpart, while maintaining a high selectivity to styrene over many hours at high conversion. Greater than 94% selectivity to styrene is observed at all times, which is a marked improvement when compared to monometallic Pd catalysts with the same Pd loading, at the same total conversion. X-ray photoelectron spectroscopy and UV-visible spectroscopy measurements confirm the complete uptake and alloying of Pd with Cu by GR. Scanning tunneling microscopy and thermal desorption spectroscopy of model SAA surfaces confirmed the feasibility of hydrogen spillover onto an otherwise inert Cu surface. These model studies addressed a wide range of Pd concentrations related to the bimetallic nanoparticles.
我们报告了一种新型纳米粒子 Pd-Cu 催化剂的合成方法，该催化剂仅含有微量的 Pd，可用于选择性加氢反应。Pd-Cu 纳米粒子是基于模型单原子合金（SAA）表面设计的，其中单个孤立的 Pd 原子作为氢吸收、解离和溢出到周围 Cu 表面的位点。Pd-Cu 纳米粒子是通过在 Al2O3 负载的 Cu 纳米粒子上添加微量 Pd（0.18 原子%），通过电置换（GR）制备的。在分批式反应器中，在环境温度下，在氢气（6.9 巴）的头压下，研究了所得材料对苯乙炔部分加氢的催化性能。与单金属 Cu 相比，双金属 Pd-Cu 纳米粒子在苯基乙炔加氢反应中的活性要高出一个数量级，同时在高转化率下保持对苯乙烯的高选择性数小时。在所有时间点都观察到超过 94%的苯乙烯选择性，与具有相同 Pd 负载量的单金属 Pd 催化剂相比，这是一个显著的改进，在相同的总转化率下。X 射线光电子能谱和紫外可见光谱测量证实了 GR 完全吸收和 Pd 与 Cu 的合金化。模型 SAA 表面的扫描隧道显微镜和热脱附光谱证实了氢溢出到原本惰性的 Cu 表面的可行性。这些模型研究涉及到与双金属纳米粒子相关的各种 Pd 浓度。
