Babassu activated carbon as catalyst for chalcone production by Claisen-Schmidt reaction: kinetic study, mechanism proposal and continuous flow bed reactor

摘要

Powdered and granulated activated carbons from babassu were submitted to alkaline treatment with 2 mol L-1 NaOH solution, washed with distilled water to pH 8 and dried. The prepared carbons were tested as catalysts in the Claisen-Schmidt reaction between acetophenone and 4-nitrobenzaldehyde using methanol as solvent at room temperature for 24 h. Babassu granular carbon (BGC) and basic babassu granular carbon (BBGC) exhibited the highest conversions, of 69.26% and 66.59%, respectively. The kinetic study was carried out with BBGC, which led to values of kinetic constant k of 5.26 L mol(-1) h(-1) at 35 degrees C and 7.35 L mol(-1) h(-1) at 50 degrees C. The activation energy of the reaction was 18.91 kJ mol(-1). This study proposes a second-order pseudo-homogeneous reaction catalyzed by BBGC. A continuous fixed-bed reactor operation was carried out with BBGC catalyst and the best conversion was 60% in 120 min using of 0.05 mol L-1 reactants concentration.