Tungstate promoted vanadium phosphate catalysts for the gas phase oxidation of methanol to formaldehyde

Formaldehyde is an important intermediate in the pharmaceutical, plastic and automobile industries which is produced commercially via methanol oxidation. A series of tungstate promoted vanadium phosphate catalysts were prepared and characterised using a combination of XRD, UV-vis spectrometry, XPS and ammonia TPD. The 25 wt% WO3-VPO catalyst exhibited good activity for the selective gas phase oxidation of methanol with 490% conversion at around 250 degrees C. This is a considerably lower temperature than used in the current industrial process using either silver or iron molybdate catalysts. This increased activity at low temperatures is ascribed to the increase in Bronsted acidity and redox properties of the tungstate doped materials.