In Situ Cobalt Speciation on γ-Al2O3 in the Presence of Carboxylate Ligands in Supported Catalyst Preparation

Molecular-scale understanding of metal impregnation on a porous oxide support is a key step toward the development of optimized (and cost-effective) catalytic materials with enhanced activity, selectivity and time on stream stability. In the present contribution in situ ATR-IR and ex situ spectroscopic measurements (XPS, UV–vis DRS) have been performed in order to describe the influence of three different oxygenated organic molecules (acetate, citrate, and nitrilotriacetate) on cobalt sorption on a conventional γ-alumina support. Variation of the preparation conditions has been done by changing the pH of adsorption, and the nature of additives (organic molecules) as well as their concentrations. Different sorption mechanisms and cobalt speciation have been evidenced during in situ ATR-IR measurement through comparison with reference spectra of pure Co and organic additives solutions. More specifically, citrate and nitriloacetate additives leads to the formation of ternary surface complexes (alumina–ligand...