Nanosized aluminum derived oxides catalysts prepared with different methods for styrene production

Various MOx-Al2O3 binary oxides catalysts (M: Fe, Ti, La, and Zr) with MOx molar percentage of 20% were prepared via three different synthetic approaches, i.e., hydrothermal synthesis, nanocasting and sol-gel methods. Characterizations by XRD and TEM showed the existence of nanosized rutile TiO2, tetragonal ZrO2, 12203, gamma-Fe2O3, alpha-Fe2O3 and gamma-Al2O3 phases. Fe-57 Mossbauer showed that either gamma-Fe2O3 or alpha-Fe2O3 phases formation on alumina is likely over Fe sol-gel derived catalyst. All solids had elevated surface area and pore volumes, being well suited in mesoporous materials range. The results indicated that structure and texture of sol-gel derived solids resulted in solid solutions and/or nanoparticles dispersed on alumina compared to the other methods. Best performances in the oxidative dehydrogenation of ethylbenzene with CO2 were obtained over FeOx-Al2O3 and TiOx-Al2O3. The Fe-containing alumina had elevated ethylbenzene conversion whereas styrene selectivity was similar to their Ti-counterparts; however, coking resistance and thermal stability was higher over Fe-containing alumina obtained by sol-gel. This was attributed to the advantaged synergistic effect among gamma-Fe2O3, alpha-Fe2O3 and gamma-Al2O3 under reduction environments that resulted in stable FeAl2O4 formation during the reaction. (C) 2012 Elsevier B.V. All rights reserved.