Nontemplate sol–gel synthesis of catalytically active mesoporous titanosilicates

Resumo

A method for the nontemplate sol–gel synthesis of micro-mesoporous and mesoporous titanosilicates is developed using commercially available raw materials (a mixture of oligomer esters of orthosilicic acid (Ethylsilicate-40) and a water–alcohol solution of titanium(IV) ethoxide). The effect of the pH values of the reaction mixture on sol–gel synthesis is studied using the characteristics of the porous structure of titanosilicates. Samples of amorphous structure with different textural characteristics are obtained by varying the pH in the range of 3–10: specific surface area, 320–740 m²/g; micropore volume, 0.04–0.15 cm³/g; and mesopore volume, 0–0.92 cm³/g. It is shown that a sample of mesoporous titanosilicate obtained with alternating pH values has maximum catalytic activity in the oxidation reaction of 4-tert-butylphenol (TBP) in aqueous solutions of hydrogen peroxide. (Conversion of 4-tert-butylphenol, 45 wt %; selectivity of the formation of 4-tert-butylcatechol, 66 wt %. Conditions: 10 wt % of titanosilicate; TBP/H₂O₂ = 1/2; 75°C; 1 h).