Selective oxidation of methane to formaldehyde by oxygen over SBA-15-supported molybdenum oxides

The selective oxidation of CH4 to formaldehyde by oxygen and its kinetics studies were investigated over MoOx/SBA-15 under atmospheric pressure. The comparative studies on catalytic reaction showed that the activity of polymeric MoOx species was significantly higher than that of isolated MoOx. The maximum HCHO yield was achieved over 20 wt% MoOx/SBA-15 catalyst at 873 K. Although the studies on contact time effect indicated that HCHO was the primary product over both isolated and polymeric Mo species, the CH4 conversion followed different mechanisms: the reaction over isolated MoOx species was a first-order reaction, whereas the other was a higher-order reaction. The catalytic activity of SBA-15-supported Mo–V–O mixed oxide was also investigated in this study. Hydrogen temperature-programmed reduction (H2-TPR), UV–visible (UV–vis) spectroscopy and X-ray photoelectron spectra (XPS) studies were performed to characterize the supported MoOx species, results showed that the nature of MoOx species remained unchanged during the reaction.

Graphical abstractThe comparative studies on selective oxidation of methane to formaldehyde showed that the activity of polymeric MoOx species was significantly higher than that of isolated MoOx. The coordination between the neighboring Mo centers was one of the vital factors. The reaction over isolated MoOx species was a first-order reaction, whereas the other was a higher-order reaction. Figure optionsDownload full-size imageDownload as PowerPoint slide