Synthesis, characterization and activity study of SO₄²⁻/Ce_xZr_1−xO₂ solid superacid catalyst

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• 作者：Benjaram M. Reddy ; Pavani M. Sreekanth ; Pandian Lakshmanan and Ataullah Khan
• 关键词：Solid superacid ; Sulfated zirconia ; Ceria– ; zirconia ; Sulfated ceria– ; zirconia ; Mannich reaction ; Ammonia-TPD
• 刊名：Journal of Molecular Catalysis A: Chemical
• 出版年：2006
• 出版时间：1 February 2006
• 年：2006
• 卷：244
• 期：1-2
• 页码：1-7
• 全文大小：246 K

文摘

Sulfated Ce_xZr_1−xO₂ catalyst was found to exhibit solid super-acidity and good catalytic activity for synthesis of β-amino ketones by a three-component Mannich type reaction in the liquid phase under solvent free conditions at ambient temperature. To make the sulfated Ce_xZr_1−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 Ce_xZr_1−xO₂ and SO₄²⁻/Ce_xZr_1−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 Ce_xZr_1−xO₂ solid solution. Powder XRD profiles reveal the presence of cubic Ce_0.5Zr_0.5O₂ in the case of unpromoted sample and tetragonal Ce_0.16Zr_0.84O₂ 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 Ce_xZr_1−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 Ce_xZr_1−xO₂ upon sulfation. The SO₄²⁻/Ce_xZr_1−xO₂ sample exhibits strong as well as super-acidic sites.