Selective orthobutylation of phenol over sulfated Fe2O3–TiO2

Abstract

Sulfated Fe₂O₃–TiO₂ (SFT) has been synthesized by an organic-free method employing ilmenite ore. Various SFT samples were prepared by drying and calcining over 100–900 °C. The XRD patterns of the system showed the presence of anatase and rutile phases of TiO₂ and Fe₂O₃. The XRF analysis and DRIFT spectra demonstrated the presence of sulfate moieties, with their content being ≥8.1 wt% for samples calcined at ≤500 °C. The number of Brønsted and Lewis acid sites of the samples calcined at ≤500 °C was found to be nearly the same as that observed from pyridine adsorption measurements. The SFT samples were found to be thermally stable up to 500 °C. The SFT samples exhibited catalytic activity for the ortho-alkylation of phenol with tert-butanol. The activity for the SFT samples calcined at ≤500 °C was 5–8 times greater than that for the samples calcined at 700 and 900 °C. The decrease in the catalytic activity of the samples in the latter cases is due to the decreased acidity of the catalysts arising from the removal of sulfate species on calcination. The sulfated Fe₂O₃–TiO₂ catalyst exhibited greater activity than similar higher surface area materials.