Estudo cinético da produção de ésteres metílicos com dimetil carbonato catalisada por fosfato de nióbio

Abstract

The aim of this study was to evaluate commercial niobium phosphate as heterogeneous catalyst in biodiesel production from oleic acid and low-cost raw materials using dimethyl carbonate as acyl receptor. Catalyst was characterized and textural and structural properties were obtained. Effect of temperature (180°C-250°C), dimethyl carbonate molar ratio (1:5, 1:10, 1:15) and catalyst concentration (2%, 5%, 10%) were investigated. Reactions at 180ºC and 200ºC, in 6 hours, achieved 57% and 75% conversion oleic acid, respectively. Reaction showed a higher reaction rate at 225ºC and 250ºC, reaching equilibrium conversion in about 3 and 2 hours, respectively. At 225 and 250ºC, maximum conversion achieved to oleic acid was 84%. For the range studied, molar ratio was not a determinant variable to increase the oleic acid conversion. Catalyst concentration had a positive effect on esterification reaction, increasing reaction rate and conversion of oleic acid. Most suitable condition was at 3 hours, molar ratio of 1:5, 5% catalyst based on FFA mass and 250°C. Catalyst could be reutilized for up to 5 cycles without significant loss of activity. A pseudo first order model was proposed to esterification of oleic acid. Niobium phosphate activity was carried out for biodiesel production with raw materials of high and low acidity.