Catalytic performance of Pd–NiCo2O4/SiO2 in lean methane combustion at low temperature

In this paper, the catalyst of Pd–NiCo2O4/SiO2 was prepared and applied to the catalytic combustion of lean methane. Pd and NiCo2O4 nanoparticles were uniformly distributed on the SiO2 support, so that every Pd or NiCo2O4 nanoparticle was separated from each other by another component. Comparing with Co3O4/SiO2, NiCo2O4/SiO2, Pd–Co3O4/SiO2 and Pd#NiCo2O4/SiO2 (catalysts without uniform distribution of Pd and NiCo2O4 nanoparticles), Pd–NiCo2O4/SiO2 had the highest catalytic activity in the catalytic combustion of lean methane, with a methane total conversion temperature at 378 °C. In addition, the high activity did not decrease during the long time reaction, which showed good thermal stability. TEM and BET results showed that the nanoparticle sizes of Pd and NiCo2O4 were very small. The XRD patterns indicated that the Pd nanoparticles were highly dispersed on the surface of SiO2. The XPS spectra demonstrated the formation of NiCO2O4, the presence of enough active oxygen species on the catalyst surface and the high ratio of PdO/Pd0. The enhanced influence of Ni introduction was also proved by comparison tests. All these results indicated that the high catalytic activity of Pd–NiCo2O4/SiO2 mainly comes from the nanoparticle distribution and the Ni cation enhancement.