Kinetics of methyl esters production with dimethyl carbonate over niobium phosphate

The aim of this study is 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, molar ratio and catalyst concentration were investigated. At higher temperature conditions, higher FFA conversions were achieved. Molar ratio was not a significant factor to conversion of oleic acid. The catalyst concentration had a positive effect on esterification reaction, increasing reaction rate and conversion of oleic acid. Most suitable condition was at 3 h, FFA:DMC 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-homogeneous first order reaction in forward and backward directions was proposed to esterification of oleic acid. Activity of niobium phosphate was investigated in simultaneous esterification and transesterification reactions.