SECONDARY-ION MASS-SPECTROMETRY AND X-RAY PHOTOELECTRON-SPECTROSCOPY OF NA2MOO4/SIO2 CATALYSTS FOR METHANE OXIDATIVE COUPLING

A series of Na2MoO4/SiO2 catalysts with Various loadings of Na2MoO4 have been characterized using secondary ion mass spectrometry (SIMS), X-ray photoelectron spectroscopy (XPS), FTIR and X-ray diffraction (XRD). Their catalytic activity for methane oxidative coupling (MOC) has been tested. The results revealed some type of interaction between Na2MoO4 and SiO2, which leads to a high dispersion of NaMoO4 at the support surface. The highly dispersed species covering the catalyst surface favour the formation of surface sites of low coordination. The relationship between catalytic performance and the amount of surface sites of low coordination was discussed.