Solvent-free preparation of nanosized sulfated zirconia with Brønsted acidic sites from a simple calcination.

Nanosized sulfated zirconia with Brønsted acidic sites has been prepared by a simple calcination in the absence of any solvent. XRD patterns reveal that the sulfated zirconia mainly consists of tetragonal crystalline zirconia with average size of about 7 nm, which is further confirmed by TEM images. N2 adsorption data show that the nanosized sulfated zirconia has high surface area (165-193 m2/g) and exhibits uniform pore distribution aggregated by zirconia nanoparticles. IR spectra of samples show that the sulfur species in the nanosized sulfated zirconia is a little different from that in conventional sulfated zirconia. Furthermore, IR spectra of adsorbed pyridine indicate that the nanosized sulfated zirconia contains relatively more Brønsted acidic sites than conventional sulfated zirconia. Catalytic tests show that the nanosized sulfated zirconia exhibits much higher activity than conventional sulfated zirconia in catalytic esterification of cyclohexanol with acetic acid.