EXAFS Characterization of PtNi Bimetallic Catalysts Applied in the Aqueous-phase Reforming of Glycerol

M. MIZRAHI; J.M. RAMALLO LOPEZ; M. L. BARBELLI; F. POMPEO; G. SANTORI; N. NICHIO

Congreso; 24ª Reunião Anual de Usuários do LNLS; 2014

LNLS-CNPEM

We present a structural characterization of the active phases of PtNi bimetallic catalysts supported on Ce-Zr-α-Al2O3 (CZA). The catalysts were evaluated in the liquid phase conversion of glycerol.  The Ni/CZA catalyst presents low conversion to gaseous products and low selectivity to H2, whereas the Pt/CZA catalyst presents higher selectivity to the glycerol reforming. The bimetallic catalyst PtNi/CZA presents the highest global activity and promotes the formation of liquid oxygenated hydrocarbons, mainly acetol and 1,2-propylene glycol, which are formed from glycerol hydrogenolysis. By means of Extended X-ray Absorption Fine Structure spectroscopy (EXAFS) studies, it was determined that in the PtNi/CZA catalysts three phases were present: nanoclusters of Pt-Ni alloy, unalloyed metallic Pt nanoclusters and unalloyed disc-shaped metallic Ni particles. The highest activity of the PtNi/CZA catalyst could be assigned to the presence of the Pt-Ni alloy which results in a more active phase than the Pt and Ni sites separately. However, the selectivity to the reforming is lower and the cleavage of C-O bond reactions are favored. The PtNi/CZA catalyst is the more stable and the EXAFS results show that this behavior would be associated to the high resistance to sintering of the metallic particles whose structure is stabilized during the first hour of the reaction.