Iliopoulou Eleni F, Pachatouridou Eleni, Lappas Angelos A
Chemical Process and Energy Resources Institute, Centre for Research and Technology Hellas (CPERI), CERTH, Thermi, GR-57001 Thessaloniki, Greece.
Nanomaterials (Basel). 2024 Jan 4;14(1):124. doi: 10.3390/nano14010124.
Cobalt-doped alumina catalysts were prepared using different methods, either conventional wet impregnation (WI) and/or advanced spray impregnation (SI), and they were evaluated as novel oxidation catalysts for CO and MeOH oxidation. The spray impregnation technique was used with the aim of achieving the synthesis of core-shell catalytic nanostructures to secure the chemical/thermal stability of active sites on the catalyst carrier. The catalysts were further promoted with a low Pd content (0.5 wt.%) incorporated via either incipient wetness impregnation (DI) or spray impregnation. The results revealed the superior performance of the spray-impregnated catalysts (Co/γ-AlO-SI) for both reactions. The deposition of Co oxide on the outer surface of the alumina particle (SEM images) and the availability of the active Co phase resulted in the enhancement of the Co/γ-AlO catalysts' oxidation activity. Pd incorporation increased the catalysts' reducibility (TPR-H) and improved the catalysts' performance for both reactions. However, the Pd incorporation method affected the catalytic performance; with the SI method, the active phase of CoO was probably covered with PdO and was not available for the oxidation reactions. On the contrary, the incorporation of Pd with the DI method resulted in a better dispersion of PdO all over the Co/Al catalyst surface, maintaining available Co active sites and a better Pd-Co interaction. MeOH desorption studies revealed the methanol oxidation mechanism: the Co/Al catalysts promoted the partial oxidation of MeOH to formaldehyde (HCHO) and dehydration to dimethyl ether (DME), while the Pd-based Co/Al catalysts enhanced the complete oxidation of methanol to CO and HO.
采用不同方法制备了钴掺杂氧化铝催化剂，即传统的湿浸渍法（WI）和/或先进的喷雾浸渍法（SI），并将它们作为用于CO和甲醇氧化的新型氧化催化剂进行了评估。使用喷雾浸渍技术的目的是实现核壳催化纳米结构的合成，以确保催化剂载体上活性位点的化学/热稳定性。通过初湿浸渍法（DI）或喷雾浸渍法掺入低含量的Pd（0.5 wt.%）对催化剂进行进一步促进。结果表明，喷雾浸渍催化剂（Co/γ-AlO-SI）在这两种反应中均表现出优异的性能。氧化钴在氧化铝颗粒外表面的沉积（扫描电子显微镜图像）以及活性Co相的存在导致Co/γ-AlO催化剂氧化活性的增强。掺入Pd提高了催化剂的还原性（程序升温还原-氢气），并改善了催化剂在这两种反应中的性能。然而，Pd的掺入方法影响了催化性能；采用SI方法时，CoO的活性相可能被PdO覆盖，无法用于氧化反应。相反，采用DI方法掺入Pd导致PdO在整个Co/Al催化剂表面更好地分散，保持了可用的Co活性位点以及更好的Pd-Co相互作用。甲醇脱附研究揭示了甲醇氧化机理：Co/Al催化剂促进甲醇部分氧化为甲醛（HCHO）并脱水为二甲醚（DME），而基于Pd的Co/Al催化剂增强了甲醇完全氧化为CO₂和H₂O。
