(670c) Using Aberration-Corrected STEM Imaging to Explore Chemical and Structural Variations in the MoVNbTeO Oxidation Catalyst

Selective oxidation catalysis is used in production of roughly 25% of all important organic chemicals and intermediates used for making consumer and industrial products [1]. Current processes used to produce high-demand C3 derivatives, namely acrylic acid and acrylonitrile, make use of multicomponent bismuth molybdate catalysts with propene feeds [1-2]. Significant cost savings exist if propene can be replaced by propane as the feedstock. The dominant candidate for this process is based on the multiphase MoVTeNbO complex oxide system [1-3]. The best MoVTeNbO catalysts with respect to selectivity and activity are two-phase mixtures comprised of an orthorhombic network bronze phase (M1) and a hexagonal tungsten bronze (HTB)-type phase (M2) [2-3]. Structural models currently exist for both phases based on simultaneous Rietveld refinement of high-resolution synchrotron X-ray and neutron powder diffraction data [2]. Recently, we have used aberration-corrected STEM methods to image M1 and M2 phase preparations. Structural models based on HAADF images are developed and compared to the Rietveld-refined model developed by DeSanto et al.[2-5].

As an extension of this work, we have characterized a number of compositional and structural variants. These include omission of Te and/or Nb, replacement of Nb with Ta [6,7], Te with Sb [8], and changing the basic framework structure. Understanding the relationship between crystal chemistry, stucture, and catalyst performance is central to the development of these catalysts.

References

[1] R. K. Grasselli, Top. Catal. 21 (2002) 79.

[2] P. DeSanto, D. J. Buttrey, R.K. Grasselli, , C. G. Lugmair, A. F. Volpe Jr., B. H. Toby, and T. Vogt, Z. Krist. 219 (2004) 152.

[3] W. D. Pyrz, D. A. Blom, T. Vogt, and D. J. Buttrey, Angew. Chem., Int. Ed. 47 (2008) 2788.

[4] W. D. Pyrz, D. A. Blom, V. V. Guliants, T. Vogt, and D. J. Buttrey, J. Phys Chem C 112 (2008) 10043.

[5] D. A. Blom, W. D. Pyrz, T. Vogt, and D. J. Buttrey, J. Electr. Micr. Online: doi: 10.1093/jmicro/dfn025

[6] P. DeSanto, D. J. Buttrey, R. K. Grasselli, W. D. Pyrz, C. G. Lugmair, A. F. Volpe, B. , T. Vogt, and B. H. Toby, Top. Catal. 38 (2006) 31.

[7] W. D. Pyrz, D. A. Blom, R. Shiju, V. V. Guliants, T. Vogt, and D. J. Buttrey, Catal. Today 142 (2009) 320.

[8] M. Sadakane, K. Yamagata, K. Kodato, K. Endo, K. Toriumi, Y. Ozawa, T. Ozeki, T. Nagai, Y. Matsui, N. Sakaguchi, W. D. Pyrz, D. J. Buttrey, and W. Ueda, Angew. Chem. Int. Ed. 48 (2009) 3782.