Catalytic combustion of lean methane over different Co3O4 nanoparticle catalysts

Three types of Co 3 O 4 catalyst, namely Co 3 O 4 nanoparticles (denoted as Co 3 O 4 -NPs, ∼12 nm in diameter), Co 3 O 4 nanoparticles encapsulated in mesoporou s SiO 2 (denoted as Co 3 O 4 @SiO 2 ), and Co 3 O 4 nanoparticles inside microporous SiO 2 hollow sub-microspheres (denoted as Co 3 O 4 -in-SiO 2 ), were explored to catalyze the combustion of lean methane. It was found that the methane conversion over the three catalysts has the order of Co 3 O 4 -NPs ≈ Co 3 O 4 @SiO 2  > Co 3 O 4 -in-SiO 2 due to the different catalyst structure. The comparison experiments at high temperatures indicate the Co 3 O 4 @SiO 2 has a significantly improved anti-sintering performance. Combined with the TEM and BET measurements, the results prove that the presence of the mesoporous SiO 2 layer can maintain the catalytical activity and significantly improve the anti-sintering performance of Co 3 O 4 @SiO 2 . In contrast, the microporous SiO 2 layer reduces the catalytical activity of Co 3 O 4 -in-SiO 2 possibly due to its less effective diffusion path of combustion product. Thus, the paper demonstrates the pore size of SiO 2 layer and catalyst structure are both crucial for the catalytical activity and stability.