1309 - Characterization of Zr(SO 4 ) 2 /ZrO 2 and Acid...

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Unformatted text preview: Characterization of Zr(SO 4 ) 2 /ZrO 2 and Acid Catalysis Bull. Korean Chem. Soc. 2001 , Vol. 22, No. 12 1309 Characterization of Zirconium Sulfate Supported on Zirconia and Activity for Acid Catalysis Jong Rack Sohn, * Tae-Dong Kwon, and Sang-Bock Kim Department of Industrial Chemistry, Engineering College, Kyungpook National University, Taegu 702-701, Korea Department of Chemistry, University of Ulsan, Ulsan 680-749, Korea Received August 24, 2001 Zirconium sulfate supported on zirconia catalysts were prepared by impregnation of powdered Zr(OH) 4 with zirconium sulfate aqueous solution followed by calcining in air at high temperature. The characterization of prepared catalysts was performed using Fourier transform infrared (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and by the measurement of surface area. The addition of zirconium sulfate to zirconia increased the phase transition temperature of ZrO 2 from amorphous to tetragonal due to the interaction between zirconium sulfate and zirconia, and the specific surface area and acidity of catalysts increased in proportion to the zirconium sulfate content up to 10 wt % of Zr(SO 4 ) 2 . Infrared spectra of ammonia adsorbed on Zr(SO 4 ) 2 /ZrO 2 showed the presence of Brnsted and Lewis acid sites on the surface. 10-Zr(SO 4 ) 2 / ZrO 2 calcined at 600 o C exhibited maximum catalytic activities for 2-propanol dehydration and cumene dealkylation. The catalytic activities for both reactions were correlated with the acidity of catalysts measured by ammonia chemisorption method. Keywords : Zirconium sulfate, Acid catalysis, 2-Propanol dehydration, Cumene dealkylation. Introduction It is known that the activity of a catalyst is greatly influenced by the method of catalyst preparation and the conditions of pretreatment. 1-4 This is illustrated by the fact that the physical or chemical structure of a catalyst varies with the method of preparation, and that chemical species adsorbed on the surface affect the catalytic activity pro- foundly. The strong acidity of zirconia-supported sulfate has attracted much attention because of its ability to catalyze many reactions such as cracking, alkylation, and isomeri- zation. The potential for a heterogeneous catalyst has yield- ed many papers on the catalytic activity of sulfated zirconia materials. 5-9 Sulfated zirconia incorporating Fe and Mn has been shown to be highly active for butene isomerization, catalyzing the reaction even at room temperature. 10,11 It has been reported by several workers that the addition of platinum to zirconia modified by sulfate ions enhances cata- lytic activity in the skeletal isomerization of alkanes without deactivation when the reaction is carried out in the presence of hydrogen....
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1309 - Characterization of Zr(SO 4 ) 2 /ZrO 2 and Acid...

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