Structure determination of powder a-Bi₂Mo₃O₁₂ by joint refinements of its Cu and Co source x-ray and neutron diffractograms

H. Fansuri*¹, D.K. Zhang¹, M. Elcombe², A. Studer², D. French³

¹Centre for Fuels and Energy, Curtin University of Technology, Australia;

²Bragg Institute, Australia; ³CSIRO Division of Energy Technology, Australia

*hfansuri@vesta.curtin.edu.au

The [lattice?] structure of a-Bi₂Mo₃O₁₂, an active catalyst for partial oxidation of propylene to acrolein¸ has been refined using a combination of Cu and Co source of x-ray and high resolution neutron diffraction. 98 parameters were refined simultaneously using a RIETICA refinement software from three diffractograms, each of which has 5750, 2125, and 2900 contributed reflections. The structure has the same symmetry as two International Crystal Structure Database (ICSD) models for a-Bi₂Mo₃O₁₂ (nos. 2650 and 63640).

The unit cell parameters obtained from the refinement are a= 7.7120 (1), b= 11.5264 (2), c=11.9746 (2), b= 115.2816 (14), V= ?, and D_x= ?. The unit cell parameters, atomic coordinate and thermal factors are easily refined and the results are within the parameters in the two ICSD models with better or the same accuracy for all atoms, which is very difficult to achieve if the refinement is done only from either the x-ray or the neutron diffractogram. The information obtained from this study is very important as it serves as the starting point in the investigation into the real time structure dynamics of the catalyst in order to better understand the mechanisms of partial oxidation of propylene to acrolein on the catalyst.