Meso-macroporous zirconia modified with niobia as support for platinum-Acidic and basic properties

Meso-macroporous tetragonal zirconia synthesised hydrothermally within this work and containing ca. 60% of mesopores and a surface area of 84 m(2)/g is a highly basic material exhibiting both Breasted and Lewis basicities (BBS and LBS). Moreover, it has Lewis acid sites and very weak BAS (bridged hydroxyls). Such ZrO2 was used as a matrix for niobium oxide species loaded as 0.3 and 1 monolayers. NbOx loading decreases basicity (both LBS and BBS) and the number of Lewis acid sites (LAS) and leads to an increase in the number of Breasted acid sites (BAS). The loading with a 0.3 monolayer of NbOx leads to a very attractive support/catalyst because of the generation of active oxygen atoms at the interface between the NbOx and ZrO2 phases. Niobio-zirconia supports were modified by impregnation with chloroplatinic acid (1 wt% of Pt). Platinum modification further changes the acid-base properties of the supports, depending on the NbOx loading. The highest Pt dispersion is reached on the NbOx monolayer because of the strong metal-support interaction. Structure and surface properties (acid-base) of the supports and platinum catalysts were characterized in detail by N-2 adsorption, XRD, XPS, UV-vis, FTIR combined with the adsorption of probe molecules (pyridine, CO at room temperature and similar to 100 K, CO2), and by test reactions (acetonylacetone cyclization and 2-propanol dehydration/dehydrogenation). (C) 2009 Elsevier B.V. All rights reserved.