Effective silica supported Sb–V mixed oxide catalyst for selective oxidation of methanol to formaldehyde

Silica supported Sb–V mixed oxide catalysts (VSbOx/SiO2) were prepared and evaluated in methanol selective oxidation. One-pass yield of formaldehyde at 91% was obtained on one VSbOx/SiO2 catalyst. The active phase of VSbOx/SiO2 catalysts is found to be Sb–V mixed oxide, in which isolated VOx species can be stabilized. The relative amount of monomeric VOx species in VSbOx/SiO2 catalyst is higher than pure supported VOx catalyst. On VSbOx/SiO2 catalyst, the deep oxidation of intermediates is greatly depressed because the formation of adsorbed acyl species, which leads to COx, is not favored. The average oxidation state of the vanadium in VSbOx/SiO2 catalysts increases with decreasing Sb/V ratio. Higher oxidation state of the vanadium in VSbOx/SiO2 catalysts is found to be relevant to higher activity while V4+ species are more selective to formaldehyde. Sb–V mixed oxide catalyst provides a possibility to adjust the production distribution in methanol selective oxidation by changing Sb/V ratio.