Catalytic performance of MoVTeNbO catalyst supported on SiC foam in oxidative dehydrogenation of ethane and ammoxidation of propane
Résumé
MoVTeNbO catalysts have been supported on pre-oxidized SIC foam by dip coating from slurry containing the precursors for all constituents and tested as catalysts for the oxidative dehydrogenation of ethane and the ammoxidation of propane. The characterization of the coating obtained by different techniques showed that a one layer coating contained almost no active M1 phase and mainly M2 phase whereas a two layers coating presented a significant amount of M1 phase. The structured catalyst thus obtained with two layers appeared highly efficient and stable in both reactions between 380 and 420 degrees C and the oxide coating exhibited fairly good mechanical properties. When compared to the most efficient powdered pure M1 phase in the case of ethane oxidative dehydrogenation and M1 + M2 phase mixture in the case of propane ammoxidation, the coated foam appeared less active; the reduced activity was attributed to the lower content in M1 phase of the supported catalyst. The selectivity to ethylene was lower, that to acrylonitrile was comparable; the decrease in ethylene selectivity was due to the presence of other active but not selective phases like TeMo5O15 and Mo0.97V0.9O5. In the case of acrylonitrile the synergy effect that takes place between the M1 and M2 phases also took place between the Mo0.97V0.95O5 phase and the M2 phase and maintained the selectivity to acrylonitrile. Improvements in preparation conditions are still possible to open the door to intensification and miniaturization on the process of propane ammoxidation on these efficient coated SIC foam structured reactors. (C) 2012 Elsevier B.V. All rights reserved.