Work

Highly Stable Apatite Supported Molybdenum Oxide Catalysts for Selective Oxidation of Methanol to Formaldehyde: Structure, Activity and Stability

Year: 2021

Type: article

Abstract: Molybdenum oxide (5 to 20 wt.%) supported on calcium or strontium hydroxyapatite were investigated as catalysts for selective oxidation of methanol to formaldehyde. These catalysts were both active and selective, with a maximum yield achieved at 95 % conversion and 96 % selectivity. The main byproducts were CO (3.2 %) and dimethyl ether (DME, 0.7 %). The catalytic performance of the catalysts was measured for up to 600 h at 350 °C. Compared to an industrial iron molybdate catalyst, the hydroxyapatite based catalysts deactivated slower. The active species were found to be a surface layer of MoOx on the hydroxyapatite support, while excess molybdenum formed crystalline (Ca/Sr)MoO4, acting as a reservoir replenishing surface MoOx lost by volatilization with methanol. The excess molybdenum in the form of (Ca/Sr)MoO4 was found to volatilize significantly slower than the excess MoO3 in iron molybdate catalysts. The combination of high activity and selectivity with low rate of Mo volatilization makes this class of catalysts interesting for industrial production of formaldehyde.

Source: ChemCatChem

DOI: 10.1002/cctc.202101220