Nanosized aluminum derived oxides catalysts prepared with different
methods for styrene production
CHEMICAL ENGINEERING JOURNAL, (2012)DOI: 10.1016/j.cej.2012.07.094
Abstract
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.