Catalytic combustion of lean methane over different Co(3)O(4) 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.