Synthesis and Physico-Chemical Characterization of CeO2/ZrO2-SO42- Mixed Oxides

Abstract

Environmentally friendly solid-acid catalysts CeO₂/ZrO₂-SO₄^2- 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 ZrO_2-SO₄^2- 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 ZrO_2-SO₄^2- 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 ZrO_2-SO₄^2-. 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/ZrO_2-SO₄^2- catalyst with the highest CeO₂ content was used.