Synthesis and Physico-Chemical Characterization of CeO2/ZrO2-SO42- Mixed Oxides
Keywords:Mixed oxides, sol-gel method, sulfation, physico-chemical characterization, acid-base properties
AbstractEnvironmentally friendly solid-acid catalysts CeO2/ZrO2-SO42- were prepared by the sol gel method varying CeO2 content (10, 20 and 30 wt%) and using sulfation in situ, maintaining the sulfate ions amount present in the materials at 20 wt%. ZrO2 and ZrO2-SO42- were also prepared for comparison proposes using the same synthesis method. The materials were characterized by X-ray diffraction, nitrogen physisorption, potentiometric titration with n-butylamine, decomposition of 2-propanol and n-pentane isomerization. The specific surface area of ZrO2-SO42- was high (160 m2/g) compared with the unmodified ZrO2 (80 m2/g), however this area decreased with increasing the CeO2 content (37-100 m2/g). There was no significant effect of CeO2 on the tetragonal structure of ZrO2-SO42-. The variation of acid sites amount runs parallel to the change of specific surface area. The acid sites amount decreased with increasing cerium oxide content. The decomposition of 2-propanol results fundamentally in the formation of dehydration products such as propylene and diisopropyl ether, both involving acid sites. In addition, a good performance during the n-pentane isomerization was observed for these materials. The selectivity towards isopentane reaches 84% when the Pt/CeO2/ZrO2-SO42- catalyst with the highest CeO2 content was used.
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