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Catalysis Letters, 1999
ZnCl2–aluminosilicate catalysts were prepared via a sol–gel route involving fluoride‐catalyzed hy... more ZnCl2–aluminosilicate catalysts were prepared via a sol–gel route involving fluoride‐catalyzed hydrolysis of aluminum and silicon alkoxides in the presence of NaF, KF, NH4F and ZnF2. The catalysts were characterized by employing 29Si, 27Al and 19F solid‐state MAS NMR. The dependence of the activities of the catalysts on the nature and amount of fluoride present in the catalysts were investigated using Friedel–Crafts alkylation reaction of benzene with benzyl chloride.
Journal of Molecular Catalysis A-chemical, 2000
Sulfated Ce x Zr 1−x O 2 catalyst was found to exhibit solid super-acidity and good catalytic act... more Sulfated Ce x Zr 1−x O 2 catalyst was found to exhibit solid super-acidity and good catalytic activity for synthesis of -amino ketones by a threecomponent Mannich type reaction in the liquid phase under solvent free conditions at ambient temperature. To make the sulfated Ce x Zr 1−x O 2 catalyst, Ce-Zr hydroxide gel was prepared by a coprecipitation method and SO 4 2− ions were deposited by treating the gel with sulfuric acid and calcined at 923 K. Surface and bulk properties of the Ce x Zr 1−x O 2 and SO 4 2− /Ce x Zr 1−x O 2 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 SO 4 2− ions strongly influence the physicochemical characteristics of the Ce x Zr 1−x O 2 solid solution. Powder XRD profiles reveal the presence of cubic Ce 0.5 Zr 0.5 O 2 in the case of unpromoted sample and tetragonal Ce 0.16 Zr 0.84 O 2 phase along with zirconium sulfate compounds in the case of SO 4 2− promoted sample. In particular, the XRD and Raman results suggest a selective interaction of the sulfate ions with zirconia portion of the Ce x Zr 1−x O 2 solid solution leading to the formation of zirconium sulfate compounds. The NH 3 -TPD profiles indicate significant changes in the distribution of acid sites on the Ce x Zr 1−x O 2 upon sulfation. The SO 4 2− /Ce x Zr 1−x O 2 sample exhibits strong as well as super-acidic sites.
Journal of Molecular Catalysis A-chemical, 2001
Sol-gel derived titania based mixed oxides TiO 2 -SiO 2 and TiO 2 -ZrO 2 were used as supports fo... more Sol-gel derived titania based mixed oxides TiO 2 -SiO 2 and TiO 2 -ZrO 2 were used as supports for preparing a series of catalysts with vanadia contents varying between 1-25 wt.%. The supports and the catalysts were characterized by employing 51 V and 1 H solid-state MAS NMR, diffuse reflectance FT-IR, and BET surface area measurements. The partial oxidation activities of the catalysts were tested using ethanol oxidation as the model reaction. 51 V solid-state NMR studies of the calcined catalysts showed the peaks corresponding to the presence of polymeric tetrahedral vanadia species at low vanadia loadings and 51 V chemical shifts corresponding to amorphous V 2 O 5 like phases were observed in the catalysts with high V 2 O 5 contents. After outgassing the catalysts, a broadening of the peaks was observed indicating a change in the coordination environment around vanadium. DRIFTS studies of the catalysts indicated the vibrations corresponding to V=O bonds of V 2 O 5 agglomerates, in the catalysts with high vanadia loadings. Acetaldehyde was obtained as the major product with traces of ethylene, ether, acetic acid, ethyl acetate, and CO x during the ethanol partial oxidation activity studies of mixed oxide supported vanadia catalysts. (J.M. Miller).
Catalysis Letters, 1999
ZnCl2–aluminosilicate catalysts were prepared via a sol–gel route involving fluoride‐catalyzed hy... more ZnCl2–aluminosilicate catalysts were prepared via a sol–gel route involving fluoride‐catalyzed hydrolysis of aluminum and silicon alkoxides in the presence of NaF, KF, NH4F and ZnF2. The catalysts were characterized by employing 29Si, 27Al and 19F solid‐state MAS NMR. The dependence of the activities of the catalysts on the nature and amount of fluoride present in the catalysts were investigated using Friedel–Crafts alkylation reaction of benzene with benzyl chloride.
Journal of Molecular Catalysis A-chemical, 2000
Sulfated Ce x Zr 1−x O 2 catalyst was found to exhibit solid super-acidity and good catalytic act... more Sulfated Ce x Zr 1−x O 2 catalyst was found to exhibit solid super-acidity and good catalytic activity for synthesis of -amino ketones by a threecomponent Mannich type reaction in the liquid phase under solvent free conditions at ambient temperature. To make the sulfated Ce x Zr 1−x O 2 catalyst, Ce-Zr hydroxide gel was prepared by a coprecipitation method and SO 4 2− ions were deposited by treating the gel with sulfuric acid and calcined at 923 K. Surface and bulk properties of the Ce x Zr 1−x O 2 and SO 4 2− /Ce x Zr 1−x O 2 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 SO 4 2− ions strongly influence the physicochemical characteristics of the Ce x Zr 1−x O 2 solid solution. Powder XRD profiles reveal the presence of cubic Ce 0.5 Zr 0.5 O 2 in the case of unpromoted sample and tetragonal Ce 0.16 Zr 0.84 O 2 phase along with zirconium sulfate compounds in the case of SO 4 2− promoted sample. In particular, the XRD and Raman results suggest a selective interaction of the sulfate ions with zirconia portion of the Ce x Zr 1−x O 2 solid solution leading to the formation of zirconium sulfate compounds. The NH 3 -TPD profiles indicate significant changes in the distribution of acid sites on the Ce x Zr 1−x O 2 upon sulfation. The SO 4 2− /Ce x Zr 1−x O 2 sample exhibits strong as well as super-acidic sites.
Journal of Molecular Catalysis A-chemical, 2001
Sol-gel derived titania based mixed oxides TiO 2 -SiO 2 and TiO 2 -ZrO 2 were used as supports fo... more Sol-gel derived titania based mixed oxides TiO 2 -SiO 2 and TiO 2 -ZrO 2 were used as supports for preparing a series of catalysts with vanadia contents varying between 1-25 wt.%. The supports and the catalysts were characterized by employing 51 V and 1 H solid-state MAS NMR, diffuse reflectance FT-IR, and BET surface area measurements. The partial oxidation activities of the catalysts were tested using ethanol oxidation as the model reaction. 51 V solid-state NMR studies of the calcined catalysts showed the peaks corresponding to the presence of polymeric tetrahedral vanadia species at low vanadia loadings and 51 V chemical shifts corresponding to amorphous V 2 O 5 like phases were observed in the catalysts with high V 2 O 5 contents. After outgassing the catalysts, a broadening of the peaks was observed indicating a change in the coordination environment around vanadium. DRIFTS studies of the catalysts indicated the vibrations corresponding to V=O bonds of V 2 O 5 agglomerates, in the catalysts with high vanadia loadings. Acetaldehyde was obtained as the major product with traces of ethylene, ether, acetic acid, ethyl acetate, and CO x during the ethanol partial oxidation activity studies of mixed oxide supported vanadia catalysts. (J.M. Miller).