The selective oxidation of methanol to formaldehyde using novel iron molybdate catalysts prepared by supercritical antisolvent precipitation†

Iron molybdate catalysts have been extensively explored for the oxidation of methanol to formaldehyde. However, low surface area catalysts are typically formed, and iron-rich phases still exist from common preparation methods, leading to lower selectivity. The use of supercritical antisolvent precipitation to form novel precursors led to catalysts with improved productivity compared to alternative precipitation techniques. Using isoconversion studies, new structure–performance relationships have been uncovered. The novel iron molybdate catalysts provided an improved formaldehyde production of 42.5 mmol_CH2O g_cat⁻¹ h⁻¹ for the best performing catalyst, whilst specific productivity was used as a descriptor to probe intrinsic properties of the catalysts. Improved performance was achieved by increased agglomerate size and by phase purity, both controlled by the precursor structure. Both properties improve the supply of oxygen to the amorphous MoO_x surface phase from the reducible crystalline phase.