Acidic Characterization of Copper Oxide and Niobium Pentoxide Supported on Silica–Alumina

Abstract

Copper oxide and niobium pentoxide were supported on silica–alumina with 2, 5, 10, 15 and 25 mass% loadings and 1:1 mass ratio of CuO:Nb2O5. XRD and BET measurements confirmed that monolayer coverage is reached with loadings between 5–10 mass%(~308 m2 g–1). The DRIFTS spectra of pyridine adsorbed catalysts showed bands associated with Bro¨nsted, Lewis and a combination of both acidic sites. Thermal analysis and liquid phase microcalorimetry provided the parameters for the best catalyst (10 mass%), which has the highest number of acidic sites (0.38 mmol g–1) and enthalpies of interaction with pyridine for Bro¨nsted and Lewis sites (DH1 = –107.5 and DH2 = –64.4 kJ mol–1, respectively).