Influence of calcination temperature on catalytic, acid and textural properties of SO42−/La2O3/HZSM-5 type catalysts for biodiesel production by esterification

Abstract

In this study, the efficiency of catalysts based on La2O3/SO42− supported on HZSM-5 zeolites was evaluated for the biodiesel production by esterification. The effect of a prior dealumination of the zeolite on the prepared catalysts properties was analyzed, as well as the influence of the calcination temperature. These materials were characterized by TGA, XRD, N2 adsorption/desorption, FTIR, and FTIR with adsorption of probe molecules (pyridine and collidine) for the identification and quantification of acid sites. Model reaction of double bond position isomerization of 1-butene was also performed, in order to evaluate the acidity of the new catalysts produced. These solids were tested in the esterification reaction of oleic acid in presence of methanol and the influence of the molar ratio between the reactants was evaluated. The results indicate that HZSM-5 modified with La2O3/SO42− can be an efficient catalyst for the esterification reaction. Whatever the reactants molar ratio used, the sulfated catalysts were more efficient than the starting zeolite in the esterification of oleic acid. The dealumination of the zeolite prior to the impregnation with SO42−/La2O3 leads to materials with improved properties. Moreover, low temperature calcination (350 °C) was revealed to also produce catalysts with more interesting properties. The enhancement of the external surface properties (acidity and area) was the main parameter influencing the activity of the catalysts for the considered reaction.