Oxydehydrogenation of propane over Mg-V-Sb-oxide catalysts. I. Reaction network
Magnesium vanadates have been shown by various groups to be active oxydehydrogenation catalysts for the conversion of light paraffins to the corresponding olefins. The olefins produced have significant commercial value in petroleum and petrochemical industry. Recently, we reported that doping of the magnesium vanadates with antimony, antimony-phosphorus, or boron, produces catalysts with significantly better selectivities to olefins than those of the parent undoped catalysts. Among these, the composition Mg4V2SbOx was selected for further study of propane oxydehydrogenation and its reaction network. At 500°C and atmospheric pressure, the selectivity to propylene decreases monotonically from 75% to 5% as propane conversion is increased from 2% to 68%. An analysis of the reaction network reveals, that propylene is the only useful first formed product, that COx is produced largely by sequential oxidation of the in situ formed propylene, but also to a lesser extent direct from propane by a deep oxidation route. The presence of two parallel pathways for COx formation is of interest, as it suggests that partial and deep oxidations may occur at different surface sites or involve different forms of reactive oxygens. Both of these might be amenable to electronic modification by substitution or doping to achieve higher propylene selectivities and yields at higher propane conversions, or their catalytic behavior might be advantageously alterable through site isolation of the paraffin activation centers.
KeywordsOxydehydrogenation propane propylene Mg-V-Sb-oxide catalyst reaction network
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- F. Cavani and F. Trifïró, Catal. Today 24 (1995) 307.Google Scholar
- M.A. Char, D. Patel, M.C. Kung and H.H. Kung, J. Catal. 105 (1987) 483Google Scholar
- aM.A. Char, D. Patel and H.H. Kung, J. Catal. 109 (1988) 463.Google Scholar
- D.S.H. Sam, V. Soenen and J.C. Volta, J. Catal. 123 (1990) 417.Google Scholar
- D.L. Stern, J.N. Michaels, L. DeCaul and R.K. Grasselli, Appl. Catal., in press.Google Scholar
- N.A. Bhore, M.T. Klein and K.B. Bischoff, I&EC Res. 29 (1990) 313.Google Scholar
- J.N. Michaels, D.L. Stern and R.K. Grasselli, Catal. Lett. 42 (1996) 139.Google Scholar
- J.L. Callahan and R.K. Grasselli, AIChE J. 9 (1963) 755Google Scholar
- aR.K. Grasselli and D.D. Suresh, J. Catal. 25 (1972) 273Google Scholar
- bJ. Nilsson, A.R. Lana-Canovas, S. Hansen and A. Andersson, J. Catal. 160 (1996) 224.Google Scholar