Influence of V-sources on the catalytic performance of VMCM-41 in the selective oxidation of methane to formaldehyde

摘要

VMCM-41 catalysts from two different tetravalent vanadium sources, hydrothennally synthesized after a mild gelation step at room temperature, were used as catalysts for the selective oxidation of methane to formaldehyde. Vanadyl acetylacetonate as VMCM-41 precursor, facilitates highest VOX density with predominance of monomeric and a small portion of low-oligomeric VOX species. It produces CH2O in high yield and the highest space time yield (STYCH2O) reaches 5.3 kg(CH2O)center dot kg(cat)(-1).h(-1) at 600 degrees C (rate of formation, r(CH2O) of 363 h(-1)). VMCM-41 synthesized from vanadyl sulfate hydrate precursor contains a more significant portion of low-oligomeric species. With a lower V loading, these VOX species are significantly less active resulting in a maximum STYCH2O of 2.7 kg(CH2O)center dot kg(cat)(-1).h(-1) at 625 degrees C (r(CH2O) of 243 h(-1)).