van Deelen Tom W, Nijhuis Jelle J, Krans Nynke A, Zečević Jovana, de Jong Krijn P
Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands.
ACS Catal. 2018 Nov 2;8(11):10581-10589. doi: 10.1021/acscatal.8b03094. Epub 2018 Oct 5.
Colloidal synthesis of nanocrystals (NC) followed by their attachment to a support and activation is a promising route to prepare model catalysts for research on structure-performance relationships. Here, we investigated the suitability of this method to prepare well-defined Co/TiO and Co/SiO catalysts for the Fischer-Tropsch (FT) synthesis with high control over the cobalt particle size. To this end, Co-NC of 3, 6, 9, and 12 nm with narrow size distributions were synthesized and attached uniformly on either TiO or SiO supports with comparable morphology and Co loadings of 2-10 wt %. After activation in H, the FT activity of the TiO-supported 6 and 12 nm Co-NC was similar to that of a Co/TiO catalyst prepared by impregnation, showing that full activation was achieved and relevant catalysts had been obtained; however, 3 nm Co-NC on TiO were less active than anticipated. Analysis after FT revealed that all Co-NC on TiO as well as 3 nm Co-NC on SiO had grown to ∼13 nm, while the sizes of the 6 and 9 nm Co-NC on SiO had remained stable. It was found that the 3 nm Co-NC on TiO already grew to 10 nm during activation in H. Furthermore, substantial amounts of Co (up to 60%) migrated from the Co-NC to the support during activation on TiO against only 15% on SiO. We showed that the stronger interaction between cobalt and TiO leads to enhanced catalyst restructuring as compared to SiO. These findings demonstrate the potential of the NC-based method to produce relevant model catalysts to investigate phenomena that could not be studied using conventionally synthesized catalysts.
纳米晶体（NC）的胶体合成，随后将其附着在载体上并进行活化，是制备用于研究结构-性能关系的模型催化剂的一条有前景的途径。在此，我们研究了该方法对于制备用于费托（FT）合成的定义明确的Co/TiO和Co/SiO催化剂的适用性，以高度控制钴颗粒尺寸。为此，合成了尺寸分布窄的3、6、9和12 nm的Co-NC，并将其均匀地附着在具有可比形态且钴负载量为2-10 wt%的TiO或SiO载体上。在H中活化后，负载在TiO上的6和12 nm Co-NC的FT活性与通过浸渍法制备的Co/TiO催化剂相似，表明实现了完全活化并获得了相关催化剂；然而，负载在TiO上的3 nm Co-NC的活性低于预期。FT反应后的分析表明，负载在TiO上的所有Co-NC以及负载在SiO上的3 nm Co-NC都已生长到约13 nm，而负载在SiO上的6和9 nm Co-NC的尺寸保持稳定。发现在H中活化期间，负载在TiO上的3 nm Co-NC已经生长到10 nm。此外，在TiO上活化期间，大量的Co（高达60%）从Co-NC迁移到载体上，而在SiO上仅为15%。我们表明，与SiO相比，钴与TiO之间更强的相互作用导致催化剂的重组增强。这些发现证明了基于NC的方法在生产相关模型催化剂以研究使用传统合成催化剂无法研究的现象方面的潜力。
