Preparation and characterization of Al2O3–MgO catalytic supports modified with lithium

Abstract

Al2O3–MgO catalytic supports were modified with different amounts of lithium in order to obtain novel Al2O3–MgO–Li(x) formulations containing basic sites. The basic sites on samples surface were identified and quantified through CO2 chemisorptions. It was found that total amount of basic sites increases as the Li content increases. The Li identification and its content were performed through Non-Rutherford Backscattering Spectroscopy (NRBS). The Li addition to the supports produce surface morphological changes as was observed with Scanning Electron Microscopy (SEM). The addition of lithium produces a decrease in specific surface area, changing the textural properties as N2-physisorption measurements reveal. Structural characterization by X-ray diffraction (XRD) suggests that Li addition changes the crystalline structure of Al2O3 from the γ to the δ phase; additionally, this technique indicate the presence of Li2CO3, which could be attributed to the preferential reaction of Li with environmental CO2. It was not found evidence of magnesium carbonates in the fresh samples by XRD. Raman spectroscopy shows bands attributed to the lithium carbonates species corroborating the found by XRD. The obtained results suggest that these materials could be potentially attractive as catalytic supports for reactions where the basic sites are useful such as selective hydrodesulphurization.