Nickel niobia interaction in non-classical Ni/Nb2O5 catalysts

Non-classical Ni/Nb2O5 catalysts [Ni introduced by the simple (SIM) or EDTA-double impregnation (DIM) methods] were prepared by aqueous hydrazine reduction at 353 K. Their structural and surface properties were investigated by XRD, TEM, XPS techniques, and by H2-TPR, H2- or O2-adsorption and isopropanol decomposition measurements. The results obtained confirmed that niobia is a typical SMSI oxide. Indeed, the hydrazine reduced the support and not the supported Ni2+ ions due to the SMSI effect. Reduction proceeded only in case of a layer of Ni2+ ions weakly bonded to a sub-layer of Ni2+ ions strongly attached to the support. This was achieved by stepwise impregnation with the nickel precursor. A very strong nickel–niobia interaction plays a crucial role in the passivation phenomenon of nickel active sites towards hydrogen or in gas phase hydrogenation of benzene. The SMSI effect was in parallel studied on classical catalysts prepared by the SIM or DIM method for comparison.

Graphical abstractHydrazine non-classical Ni/Nb2O5 catalyst preparation and properties confirmed that niobia is a typical SMSI oxide, e.g.: (i) precursor hydrazine reduction proceeded only in case of Ni2+ ions weakly bonded to a layer of Ni2+ ions strongly attached to the support; (ii) nickel active sites were passivated in the final material. SMSI in classical Ni/Nb2O5 catalysts was in parallel studied. Figure optionsDownload full-size imageDownload as PowerPoint slide