(513eu) Impact of Structural Changes from Metal Deposition Method on the Catalytic Performance of Pt/Ceria Zirconia-Based Catalysts

The catalyst synthesis method could impact its performance due to differences in metal particle size, metal dispersion, and metal-support interaction that may arise. Our current work is on the influence of the metal impregnation strategy method on catalyst performance. A set of reforming catalysts containing Pt (0.16 wt%),Ni (2.7wt%) and/or Mg (0.50wt%) supported on ceria-zirconia (CZO) was synthesized. The metal composition was selected based on a previous study on impact of metal loadings on catalyst performance. The metals were co-impregnated unto the support or impregnated sequentially to form Pt-Ni-CZO and Pt-Mg-CZO samples. Powder X-ray diffraction presented peaks for cubic-fluorite structure of ceria and this was corroborated by the Raman spectra, which presented a band for the F2g vibration of the fluorite lattice of ceria. The temperature-programmed reduction results indicated a difference in reduction temperature of the metal oxides arising from different degrees of metal-support interaction. For the Pt-Ni samples, the degree of reducibility followed the trend 0.16Pt-2.7Ni-CZO-seq<2.7Ni-0.16Pt-CZO-seq<0.16Pt-2.7Ni-CZO-co and those of the Pt-Mg sample was 0.16Pt-0.50Mg-CZO-seq<0.16Pt-0.50Mg-CZO-co<0.50Mg-0.16Pt-CZO-seq.The impregnation effect on the nature of CO₂ dissociation on the catalyst surface was investigated using FTIR studies. The FTIR spectra presented bands of different intensities belonging to carbonates and formates. CH₄ decomposition experiments showed differences in the amounts of products formed. Temperature-programmed oxidation also showed differences in the amounts of CO₂ produced and their formation temperatures. Steady-state dry reforming tests indicated differences in catalyst activities with the CH₄ conversion rate at 470 ℃ being between 10.2-10.9 µmol/gcat/s for the Pt-Ni samples and between 0.9 - 1.6 µmol/g_cat/s for the Pt-Mg samples. The CH₄ apparent activation energies of the Pt-Mg were ranged between 30.7-38.4 kcal/mol, and that of the Pt-Ni samples ranged from 29.1-37.7 kcal/mol. This work provides information on how the metal-metal interactions and metal deposition method could impact the catalyst performance.