X-Ray Diffraction Characterization of Grain Sizes of Ce-Zn Nanocomposite Catalyst Supports

R.E. BOLMARO; C. E. BARRIOS; M. A. BALTANÁS; A. L. BONIVARDI

Joinville

Congreso; Congresso Brasileiro de Ciência e Engenharia dos Materiais; 2012

CBECIMAT

Two methods to prepare Ce-Zn-O support materials were developed: (i) co-precipitation of mixed oxalates in a microemulsion of n-hexanol in water (H2O/n-hexanol= 2.5; dimethyloxalate concentration= 4% w/v; T= 333 K, 2h), coded OC, and (ii) co-precipitation of carbonates using ammonium carbonate (final pH= 7.1), coded CC. The theoretical Zn/Ce atomic ratio was varied between 0 and 100%. The washed precipitates were dried at 323 K under vacuum during12 h. The decomposition of the dried solids was performed under flowing 20%O2/N2 air (W/F= 10-3 g h cc-1) heating at 723 K (4h). The ZnO, CeO2 or a mixture of both oxides was obtained, without evidence of solid solution formation. For the complete set of oxide nanocomposites the BET surface areas (SBET) were in the range of 6-90 m2 g-1, increasing with the cerium content. This properties were in agreement for applied as catalyst supports. The particle size characterization of both series of nanocomposites with varied contents of Ce and Zn oxides were performed by XRD experiments performed on a Panalytical MPD X-ray diffractometer equipped with Cu tube, X-ray lens, graphite monochromator and parallel plates (Soller plates) on the out going beam on a parallel beam arrangement. The machine peak broadening was determined with a Si standard and the Cagliotti formula coefficients were used for later subtraction and calculation of domain sizes of CeO2 and ZnO particles. The whole process was performed as implemented on MAUD software. The results will be analyzed and correlated with ZnO content and synthesis procedure.