Co3O4 Nanoparticle-Decorated SiO2 Nanotube Catalysts for Propane Oxidation

Improving the alkali metal resistance of catalysts as well their catalytic activity is of great importance in propane oxidation, but current studies are rarely reported. Herein, we fabricated a one-dimensional cowpea-like Co/SiO2–N catalyst with Co3O4 nanoparticles embedded in amorphous SiO2 nanotubes via a nanocasting method using Co-MOF (Co-CAT-1) as a template. The Co/SiO2–N catalysts with a high Co loading amount of ∼40 wt % exhibited superior catalytic performance and stronger resistance to alkali metal poisoning than traditional supported Co/SiO2–I catalysts in propane oxidation. The Co/SiO2–N, K–Co/SiO2–N, and Co/SiO2–I catalysts showed almost complete conversion of propane at 240, 330, and 330 °C, respectively, while K–Co/SiO2–I catalysts had an insufficient propane conversion of 68% at 390 °C. Various characterizations of physical–chemical properties, kinetic studies, and in situ diffuse reflectance infrared transform spectroscopy studies revealed that the amorphous SiO2 shell could provide confined effects for active sites and "shielding effects" for alkali metal poisoning. Alkali metals could restrain redox reactions of Co/SiO2–I catalysts by weakening oxygen mobility and inhibiting CO2 desorption. Furthermore, the propane oxidation reactions over Co/SiO2–N and K–Co/SiO2–N catalysts proceeded in accordance with the carbonate pathway and acrylate pathway, while the entire reaction pathways of Co/SiO2–I and K–Co/SiO2–I catalysts were related to carbonate species. Therefore, the developed one-dimensional cowpea-like catalysts have higher catalytic efficiency even after alkali metal incorporation.