Modelagem cinética da reação de conversão de etanol em butanol com catalisadores de mg/al derivados de hidrotalcitas

Abstract

Butanol has been suggested as possible substitute of gasoline or to be used as fuel additive. At the moment, its main production route is from fossil raw material, allowing renewable routes from bioetanol to be studies, one of them being the catalysis using heterogeneous catalysts. One type of catalyst are the mixed oxides of Mg/Al obtained from hydrotalcites, presenting high superficial area, low cost and easy synthesis. Studies about this catalyst present the formation of other compounds other than butanol, and suggest that the involved mechanism follows the Guerbet reaction, where multiple reaction occuring in steps. Beside many similar mechanisms have being proposed, there is a lack of kinetic analysis of the involved reactions. Using one catalyst of Mg/Al derived from hydrotalcites, catalystic tests were performed in various temperatures, and after data collection, multiple reactions were analyzed thermodynamically in order to propose a mechanism which is favorable for the butanol and the other compounds formation. After this thermodynamic analysis, favorable reactions were defined, allowing two different elementary reactions models and one heterogeneous model to be proposed. Kinetic parameters of these models were estimated using a particle swarm algorithm for objective function minimization, also performing the Fisher F test for statistical comparison between models. Results show that for the experimental data, the Guerbet reaction is not the most favorable reaction path, where the direct condensation of two ethanol molecules presents itself as the main reaction mechanism. Between the analyzed models, the heterogeneous was the one which presented the best results for the minimization of the objective function, and also the best model statistically according to the Fisher test.