Mesoporous sulfated zirconia mediated acetalization reactions

A novel, convenient, one step synthetic procedure for the synthesis of mesoporous sulfated zirconia (m-SZ) using zirconium carbonate complex and its use as solid acid catalyst for the acetalization of different carbonyl compound is reported. The high specific BET surface area (234 m2 g−1) of m-SZ is achieved after the removal of the surfactant (cetyltrymethylammonium bromide, CTAB) through calcination at 550 °C for 6 h. Microscopic analysis indicated the presence of spherical particles with worm like pores. DRIFT (diffuse reflectance FTIR) of pyridine adsorbed m-SZ and NH3-TPD (temperature programmed desorption) analysis suggested the presence of appreciable amount of Brönsted acid sites. The synthesized m-SZ showed high catalytic activity towards protection of carbonyl compounds through acetal/ketal formation. For the open ketal (from cyclohexanone and methanol) 97% conversion with 100% selectivity was obtained in 1 h at room temperature under solvent free condition. The catalyst can be easily recycled after separation from the reaction system without considerable loss in catalytic activity.

Figure optionsDownload high-quality image (199 K)Download as PowerPoint slideHighlights
► Synthesis of mesoporous sulfated zirconia (m-SZ) with high specific surface area.
► Strong and high amount of acid sites are present.
► Highly active towards acetalization reactions.
► 97% yield of dimethyl ketal of cyclohexanone was obtained using methanol in 45 min.
► m-SZ is easily recoverable from reaction system and can reuse for at least 5 times.