Avaliação do catalisador 10% Co/Nb2o5 na Síntese de Fischer -Tropsch em reator de leito de lama agitado

Abstract

The goal of this work was to evaluate the performance of a 10% Co/NboOs catalyst for the Fischer-Tropsch Synthesis (FTS) by using an agitated slurry reactor. The author developed the reaction unit and the methodology to this evaluation and evaluated three possible FTS reaction models and the parameter estimation of the kinetic equations. The catalyst was prepared by the homogeneous precipitation method to obtain a 10%wt of cobalt supported on niobium pent oxide. The reactions were performed in a 500mL slurry reactor containing 20g of the 10% Co/Nb2O5 catalyst, which was ex-situ reduced at 500°C, and 150g of octacosane (C28H58) solvent. The reaction temperature varied from 180 to 220°C and the initial flow rate of the reaction mixture varied from 18 to 65 mL/min. The operating reaction pressures were 10, 20 and 28bar. The reaction selectivity was calculated through chromatographic analysis of gaseous effluent relating its molar fractions with the slurry composition by an asymmetric model of the liquid-vapor equilibrium (LVE). An estimative of the carbon chain growth probability parameter (a) for the total products and gaseous mixture was obtained by using the Anderson-Schulz-Flory (ASF) products distribution model. Parameters for the three kinetic models and a possible reaction mechanism were estimated by non-linear regression analysis. The results showed that the 10% Co/Nb2O5 catalyst presented a good stability within few hours of reaction, low selectivity to methane and carbon dioxide, and high selectivity to Cs+ hydrocarbons, especially in the range of gasoline (C5-C11) and diesel (C12-C20). The calculated values for a were all grater than 0.74, which demonstrate the potential of the FTS in slurry-type reactors. The parameters estimated for the kinetic models were slightly different than the others cobalt catalysts obtained from the literature. The adjustment of the models to the experimental data showed correlation coefficients grater than 0.94.