Amorphous vanadium phosphate catalysts from supercritical antisolvent precipitation

Crystalline vanadium phosphate catalysts (VPO) are the only example of a co mmercial heterogeneous partial oxidation catalyst for the activation of alk anes. The origin of activity is generally accepted as being associated with the crystallinity of the compounds. Here we describe a new preparative rou te to VPO using antisolvent precipitation with supercritical CO2 to generat e amorphous microspheroidal VPO, which produces a material with an activity per unit area comparable to those of conventional crystalline VPO catalyst s. This finding throws doubt on the currently accepted view for the origin of the activity of VPO catalysts and the role of crystalline phases. (C) 20 01 Academic Press.