Synthesis, characterization and activity study of SO42-/CexZr1-x O2 solid superacid catalyst

Sulfated CexZr1-xO2 catalyst was found to exhibit solid super-acidity and good catalytic activity for synthesis of P-amino ketones by a three-component Mannich type reaction in the liquid phase under solvent free conditions at ambient temperature. To make the sulfated CexZr1-xO2 catalyst, Ce-Zr hydroxide gel was prepared by a coprecipitation method and SO42- ions were deposited by treating the gel with sulfuric acid and calcined at 923 K. Surface and bulk properties of the CexZr1-xO2 and SO42-/CexZr1-xO2 samples were investigated by means of X-ray powder diffraction, thermogravimetry, ammonia-TPD, Raman spectroscopy and BET surface area methods. Characterization results indicate that impregnated SO42- ions strongly influence the physicochemical characteristics of the CexZr1-xO2 solid solution. Powder XRD profiles reveal the presence of cubic Ce0.5Zr0.5O2 in the case of unpromoted sample and tetragonal Ce0.16Zr0.84O2 phase along with zirconium sulfate compounds in the case of SO42- promoted sample. In particular, the XRD and Raman results suggest a selective interaction of the sulfate ions with zirconia portion of the CeZr1-xO2 solid solution leading to the formation of zirconium sulfate compounds. The NH3-TPD profiles indicate significant changes in the distribution of acid sites on the CexZr1-xO2 upon sulfation. The SO42-/CexZr1-xO2 sample exhibits strong as well as super-acidic sites. (c) 2005 Elsevier B.V. All rights reserved.