(621ad) A Study of M1/M2 Phase Cooperation in the Mov(Te, Sb)(Nb, Ta)O Catalysts for Propane Ammoxidation to Acrylonitrile

Jungwon Woo and Vadim V. Guliants

Chemical
Engineering, University of Cincinnati, Cincinnati OH 45221

Abstract

Selective
(amm)oxidation
of propane over the bulk mixed MoVTeNbO catalysts
containing so-called M1 and M2 phases has attracted significant attention of
the catalysis community in recent years. Although the M1 phase alone is capable
of activating propane to acrylic acid and acrylonitrile, the presence of the M2
phase was proposed to improve the selectivity to these products because it could
efficiently convert the propylene intermediate desorbed
from the M1 surface. While this phase cooperation effect was proposed for the MoVTeNbO system, other compositional variants in the M1/M2
catalytic system have not been systematically investigated.

In this
study, the M1 and M2 phases of MoV(Te, Sb)(Nb, Ta)O catalytic system were synthesized by the slurry
evaporation and hydrothermal synthesis methods. The M1 and M2 phases of the MoVSbTaO composition were synthesized for the very first
time. The M1/M2 phase mixtures and pure M1 and M2 phases were systematically
investigated in propane and propylene ammoxidation.
The results obtained indicated that the enhanced selectivity to acrylonitrile
observed for the M1/M2 phase mixtures may be explained by grinding the M1 phase
crystals that resulted in preferential exposure of the ab planes of this phase proposed
to contained the active and selective sites for propane (amm)oxidation.