Post-synthesis alumination of mesoporous silica SBA-15 with high framework aluminum content using ammonium hexafluoroaluminate

Short-channeled mesoporous Zr–Al-SBA-15 as a highly efficient catalyst for hydroxyalkylation of phenol with formaldehyde to bisphenol F

“…3. According to the literatures [34,[39][40][41][42][43], bands at 1445 and 1595-1602 cm À1 can be assigned to the hydrogen-bonded pyridine. The bands at 1450 and 1620 cm À1 are attributed to the pyridine adsorbed onto Lewis acidic (L) sites, and the bands at 1545 and 1638 cm À1 are assigned to the pyridine adsorbed onto Brønsted (B) acidic sites, while the band at 1490 cm À1 is ascribed to the pyridine adsorbed onto both B and L acid sites.…”

Effect of aluminium incorporation by the “pH-adjusting” method on the structural, acidic and catalytic properties of mesoporous SBA-15

“…Hence, the incorporation of large amounts of Al atoms in a tetrahedral environment (Al IV ) seems essential to obtain highly acidic and active catalysts. Therefore, efforts have been made in introducing Al IV atoms in the neutral silica framework of SBA-15 to generate Brönsted acid sites by various synthetic strategies, which include ''direct synthesis'' [14][15][16][17][18], ''post-synthesis grafting'' [19][20][21][22][23] and ''pH-adjusting'' [24]. However, following the direct synthetic approach, aluminium atoms cannot be effectively incorporated in SBA-15 because of the strong acidic media required for the formation of the hexagonal mesophase (i.e., pH < 0).…”

Synthesis of tungsten carbide on Al-SBA-15 mesoporous materials by carburization

“…A smaller dP was determined for Al-SBA-15 (Si/Al ¼ 2) than for Al-SBA-15 (Si/Al ¼ 10). Studies on post synthesis alumination of SBA-15 in basic media reported by Kao et al [24] indicated a decrease in surface area with the increase of aluminum content which was attributed to the alkaline dissolution of the structure. Since both kinds of Alincorporated SBA-15 samples of this study were prepared by the same protocol steps than Kao et al [24] we could not discard the formation of segregated aluminum-containing phases.…”

“…Studies on post synthesis alumination of SBA-15 in basic media reported by Kao et al [24] indicated a decrease in surface area with the increase of aluminum content which was attributed to the alkaline dissolution of the structure. Since both kinds of Alincorporated SBA-15 samples of this study were prepared by the same protocol steps than Kao et al [24] we could not discard the formation of segregated aluminum-containing phases. Indeed, 27 Al solid state NMR performed on Al-SBA-15 (Si/Al ¼ 2) revealed the presence of extra-framework alumina (vide infra).…”

“…The mesoporous silica SBA-15 was synthesized under acid conditions using triblock copolymer P123 poly(ethylene oxide)/ poly(propylene oxide)/poly-(ethylene oxide), (EO20PO70EO20), as a template [2,24]. Typically, 4 g of P123 was dissolved in a solution of 100 mL of distilled water acidulated with 25 mL of HCl (37%, SigmaeAldrich).…”