Catalytic Activity and Selectivity of Perovskites La1-Xsrxv1-X3+Vx4+O3 for the Transformation of Isopropanol
(EN)
Trikalitis, P. N.
(EN)
Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείας
(EL)
Trikalitis, P. N.
(EN)
The catalytic decomposition of isopropyl-alcohol (IPA) was studied over the perovskite series La1-xSrxV1-x3+Vx4+O3 (x=0.0, 0.05, 0.1, 0.2, 0.4, 0.6, 0.8, 0.9, 0.95, 1.0) in the range 200-300 degrees C. Catalyst characterization by XRD shows that gradual substitution of La3+ by Sr2+ transforms the LaVO3 structure to SrVO3, both of cubic symmetry. ESR spectra at 13 K shows that the V4+ (d(1)) centers are localized in the form of vanadyl groups up to x approximate to 0.6, while thereafter they become delocalized. The catalytic transformation of IPA over these solids shows that the products obtained are propene and acetone. The selectivity of the reaction for x=0.0 is ca. 15% for acetone (85% propene) and increases linearly with the substitution of La by Sr reaching at x=1.0 the value of 40% (60% propene). The total reaction rate was maximum at x=0.0 and drops up to x=0.2, thereafter remaining almost steady. The apparent activation energies calculated for the total conversion of IPA (E(tot)) according to the first order kinetics are clustered around 120 kJ/mol. These values are almost similar to those found for the acetone formation (E(acet)) while those estimated for the propene formation (E(prop)) are lower by an amount of 10-15 kJ/mol on average. A common compensation effect observed for the production of propene and acetone is explained by the variation of the heats of adsorption of the product. The reaction route seems negligibly influenced by electronic effects of the solids and it is mainly controlled by the acid/base function of the solid surface.
(EN)
