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

Authors: 
Pyrz, W. D., University of Delaware
Buttrey, D. J., University of Delaware
Blom, D. A., University of South Carolina
Vogt, T., University of South Carolina
Sadakane, M., Hiroshima University
Ueda, W., Hokkaido University


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.