Synthesis of CeO2 and CeZrO2 mixed oxide nanostructured catalysts for the iso-syntheses reaction
The different CeO2 oxides and mixed oxide CeZrO2 showed nanosized structures and morphologies in particular distinct structural and surface properties. These catalysts were effective in the iso-synthesis reaction. The flowerlike CeO2 (F) and the mixed oxide (CeZrO2) showed the highest selectivity toward isobutene and isobutene and low methane formation. The turnover frequency (TOF) related to the total basicity and total acid sites are equal for all catalysts within a factor less than 2 and did not change with the oxygen lattice capacity (OSC), which confirms that the reaction is structure insensitive. The selectivity of total hydrocarbon and of CO2 are independent of the basic sites. However, the selectivity of total iso-C4 exhibits a linear relationship with the basic sites. The mixed oxide (CeZrO2) presented the strongest basic sites and thus the highest selectivity to iso-C4. Significant is the influence of Lewis acid sites on the selectivity of isobutene increasing and isobutane decreasing both linearly with Lewis acid sites. The ratio isobutene/isobutane presented a linear relationship with the Lewis acid sites which are directly related to OSC capacity of reducible oxides.
Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (157 K)Download as PowerPoint slideHighlights► Selective conversion of synthesis gas on metal oxides producing isobutene/ane. ► Preparation methods of nanosized structure of CeO2 and mixed oxide CeZrO2. ► Mixed oxide presented the strongest basic sites and the highest selectivity to iso-C4. ► Ceria and ceria doped with zirconia promoted different Brönsted and Lewis sites. ► Significant is the influence of Lewis acid sites on the selectivity of isobutene and isobutane.
Journal: Applied Catalysis A: General - Volume 450, 15 January 2013, Pages 131–142