The Mechanism of Alkane Selective Oxidation by the M1 Phase of Mo–V–Nb–Te Mixed Metal Oxides: Suggestions for Improved Catalysts

Abstract

We report here first principles predictions (density functional theory with periodic boundary conditions) of the structures, mechanisms, and activation barriers for the catalytic activation and functionalization of propane by the M1 phase of the Mitsubishi-BP America generation of Mo–V–Nb–Te–O mixed metal oxide (MMO) catalysts. Our calculations show that the reduction-coupled oxo activation (ROA) principle, which we reported at Irsee VI to play the critical role for the selective oxidation of n-butane to maleic anhydride by vanadium phosphorous oxide, also plays the critical role for the MMO activation of propane, as speculated during Irsee VI. However for MMO, this ROA principle involves Te=O and V rather than P=O and V. The ability of the Te=O bond to activate the propane CH bond depends sensitively upon the number of V atoms that are coupled through a bridging O to the Te=O center. Based on this ROA mechanism, we suggest synthetic procedures aimed at developing a single phase MMO catalyst with dramatically improved selectivity for ammoxidation. We also suggest a modified single phase composition suitable for simultaneous oxidative dehydrogenation of ethane and propane to ethene and propene, respectively, which is becoming more important with the increase in petroleum fracking. Moreover, we also suggest some organometallic molecules that activate alkane CH bonds through the ROA principle.