What are the optimal calcination conditions?! V4+ → V4+/V5+ → V5+/V4+ Thermogravimetric analysis of VPO calcination A. Shekari, K. M. S. Hansen, C. Fankem, T. Tzakova and G.S. Patience Dép.Génie Chimique, École Polytechnique, C.P. 6079, Succ. “CV”, Montréal, Qc, Canada H3C 3A7 n-Butane partial oxidation to maleic anhydride over VPO: (VO)2P2O7 + ½ O2 2 VOPO4 14 VOPO4 + C4H10 C4H2O3 + 4 H2O + 7(VO)2P2O7 Catalyst synthesis from precursor (VPO hemihydrate): 2 VOHPO4.½H2O (VO)2P2O7 + 2 H2O Weight loss – 12-18% Carbon evolution – at ~260-300oC (most with air co-feed) Water evolution – at 100°C and 260°C Introduction Results Continuous uptake of oxygen happens after oxygen calcination Mass loss of water during argon calcination 480 °C Lattice water evolution 390 °C Surface water % Mass loss ~100 °C 260 °C Literature Time, minutes Catalyst Atmosphere What are the optimal conditions? Number Duration, hr Temperature, °C Combustion peaks during oxygen calcination Color change during calcination Precursor Partial pressures 390°C, 10 h in Air Temperature, °C 480°C, 10 h in Air 200 °C ~ 80 °C Two water peaks during argon calcination Time, minutes Partial pressure Conclusions Argon to oxygen switch at 450 °C Argon Oxygen 450 °C Time, minutes Partial pressures What are the optimal calcination conditions?! VPO precursor calcination steps: 1- Desorption of surface adsorbed water (~100°C) – Loosely bound and surface water 2- Solid transformation I (280-460°C) 2 VOHPO4.½H2O (VO)2P2O7 + 2 H2O Vanadyl hydrogen phosphate Vanadyl pyrophosphate, V4+ hemihydrate, V4+ 3- Solid transformation II ( ≥460 °C) (VO)2P2O7 + ½ O2 2 VOPO4 Acknowledgements: E.I du Pont de Nemours, NSERC – CRSNG, MDEIE