Sol-gel derived Cr(III) and Cu(II)/γ-Al₂O₃ doped solids: Effect of the dopant precursor nature on the structural, textural and morphological properties

Powders of xerogel γ-Al₂O₃ doped with various concentrations of Cr³⁺ and Cu²⁺ (M/M + Al molar fraction = 0.75-10%) were prepared via a sol-gel method. Cr³⁺ and Cu ²⁺ precursors (acetylacetonate, nitrate or chloride) were added to 0.12 M 2-propanol solution of aluminum tri-sec-butoxide (ASB) and hydrolysis was performed using a H₂O/ASB molar ratio of 4.7. The effect of the dopant precursor on structural, textural and morphological properties was studied. Employing acac precursors resulted in unique properties after calcination at 500 °C including high surface areas, as high as 455 m ²/g, homogeneous mesopores, 3-12 nm, and amorphous powders (5-10 nm particles in diameter). On the other hand, the acac precursor enhanced the resistance to sintering mainly at higher metal loads (10%) and elevated temperature (800 °C). Nevertheless, the solids issued from nitrate and chloride precursors exhibited lower surface areas at high metal loads, and lower resistance to sintering.