Oxidative dehydration of glycerol over alternative H,Fe-MCM-22 catalysts: Sustainable production of acrylic acid

Gas-phase oxidative dehydration of glycerol to generate acrylic acid has been studied on bifunctional H,FeMCM-22 catalysts aiming at the use of glycerol obtained as co-product during transesterification of vegetable oils to produce biodiesel. In this work, MCM-22 zeolite was submitted to consecutive ion exchanged with Fe+ solutions for three times to obtain different iron loadings. The samples were calcined, characterized and evaluated in the gas-phase oxidative glycerol dehydration at 320 degrees C. The increase of iron content resulted in a decrease of acid sites density and textural properties. Fe3+ oligomers and iron oxide clusters were identified as the main iron species. The catalyst containing the lowest iron content has shown better activities and yields to acrylic acid. Higher glycerol conversion was favored by a balance between acid and textural properties. Acrylic acid yield increased with the reaction time, reaching 57% after 10 h on the catalyst containing 1.2 wt% of iron. These results suggest that H,Fe-MCM-22 are promising catalysts for a sustainable production of acrylic acid in substitution of vanadium based catalysts.