The effect of molar ratio substrate/oxidant in the catalytic oxidation of styrene with H2O2

CANDELARIA LEAL MARCHENA, CLARA SAUX, LILIANA B. PIERELLA

Rosario, Argentina

Workshop; 1st Argentinean Workshop in Environmental Science; 2009

The influence of substrate/oxidant ratio for partial oxidation of styrene towards benzaldehyde and other products with hydrogen peroxide as oxidant on pentasyl microporous zeolite modified with chromium (Cr-ZSM-5), was studied. The MFI zeolites, were obtained by hydrothermal crystallization in the Na2O-Al2O3-SiO2 system. Cr was incorporated to the matrix (NH4+-ZSM-5) by wetness impregnation technique followed by post-thermal treatments at 500°C (N2 at 10 ml/min and muffle). The analyses performed by Atomic Absorption revealed that a 3.0 Cr wt% was effectively incorporated in the samples. XRD and FTIR on the fingerprint zone showed a 98% and 97% of crystallinity. Structure and orthorhombic symmetry were confirmed. The reaction test were carried out at 60 ºC varying styrene to H2O2 molar ratio (between 0.45 and 3.2) at different reaction time (1, 3, 5 and 7 h), over 0.2 g of the catalyst and acetonitrile as solvent. The products were analyzed by GC-Mass spectrometry. As can see on figure, styrene conversion shows an increment when the styrene/H2O2 diminishes. The benzaldehyde selectivity has the same behavior.  This performance could be associated with the decrease of the oxidant agent in the reaction medium. Benzaldehyde was the main product, even though others could still be found, such as styrene oxide, phenylacetaldehyde, 1-phenyl, 1,2-ethanediol and benzoic acid.