Impacts of calcination on surface-clean supported nanoparticle catalysts
Impacts of calcination on surface-clean supported nanoparticle catalysts
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DOI：
10.1016/j.apcata.2019.04.016
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发表时间：
2019-06
期刊：
影响因子：
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通讯作者：
K. Bryant;Christy Wheeler West;S. Saunders
中科院分区：
文献类型：
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作者：
K. Bryant;Christy Wheeler West;S. Saunders
制备尺寸受控的负载型纳米颗粒催化剂的传统方法通常需要使用钝化纳米颗粒表面以防止过度生长和聚集的稳定化配体。这些配体在催化表面上的存在可能对活性有害，并且通常通过高温退火步骤除去，这最终导致纳米颗粒形态的变化，从而降低活性。我们先前证明了甲硅烷基胺可切换表面活性剂可用于合成高活性纳米颗粒并将其存款到载体表面上，同时保持单分散性。在这里，我们使用XPS证明，以这种方式制备的负载型纳米颗粒在沉积后是表面清洁的，无需传统的活化步骤。此外，它表明，即使是低温煅烧对催化剂性能的不利影响，包括在纳米粒子形态的变化，导致活性的显着降低，表面亲水性的变化，活化能的变化，并导致在形成的诱导时间，当用于4-硝基苯酚的氢化。虽然煅烧仍然是一种广泛使用的催化剂活化方法，但高温对催化剂性能的不利影响往往被忽视。
Traditional methods of preparing size-controlled supported nanoparticle catalysts typically require the use of stabilizing ligands that passivate the nanoparticle surface to prevent overgrowth and aggregation. The presence of these ligands on catalytic surfaces can be detrimental to activity and are typically removed via a high-temperature annealing step, which ultimately results in changes to nanoparticle morphology and thus, reduced activity. We previously demonstrated that silylamine switchable surfactants can be used to synthesize and deposit highly active nanoparticles on to a support surface while preserving monodispersity. Here, we demonstrate using XPS that supported nanoparticles prepared in this manner are surface-clean after deposition, eliminating the need for traditional activation steps. Further, it is shown that even low-temperature calcinations have detrimental effects on the catalyst properties including changes in nanoparticle morphology that result in a significant decrease in activity, a change in surface hydrophilicity, a change in activation energy, and results in the formation of an induction time when utilized in the hydrogenation of 4-nitrophenol. While calcination remains a widely used method of catalyst activation, the detrimental effects of high temperatures on catalyst properties are often overlooked.