1. What are the optimal calcination conditions?!
V → V4+/V → 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 O VOPO4
14 VOPO4 + C4H 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 ~ oC (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 ( °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 O VOPO4
Acknowledgements: E.I du Pont de Nemours, NSERC – CRSNG, MDEIE