Estudo da eterificação catalítica de glicerol em reator contínuo

Abstract

Catalytic etherification of glycerol with short-chain alcohols to obtain mono, di and trialkyl glyceryl ethers, which can be applied as valuable fuel additives, shows a promising route in the solution problem of glycerol excess on the market. The knowledge of the phase behavior for alcohol and glycerol mixtures under high pressure is a key step in the development of the etherification process using pressurized reagents. Thus, in this work, phase equilibrium measurements of the ethanol (1) + glycerol (2) system were performed at temperatures ranging from 150 to 250 °C. The phase equilibrium data were correlated using the Peng Robinson equation of state coupled to the van der Waals mixing rules at quadratic level for composition. Subsequently, a continuous reactor was selected to evaluate the etherification reactions of glycerol with ethanol conducted under atmospheric pressure and under high pressure. The catalytic performances of Amberlyst 15, beta zeolite and niobic acid were compared and the best result in terms of ethers yield was selected for further investigation. The process parameters for atmospheric and high pressure reactions were defined as: temperature (160 to 210 ° C and 180 to 250 °C), ethanol: glycerol molar ratio (4:1 to 16:1 and 4:1 to 20:1) and amount of catalyst (0 to 0.8 g for both cases). The effect of each parameters as well as their interactions on glycerol conversion and yield to ethers was evaluated using experimental design. In addition, the response variables were optimized using canonical analysis. Amberlyst 15 showed the best performance among the catalysts tested. The most promising results were achieved in reactions conducted under high pressure. The maximum yield to ethers was 56% observed at the temperture of 238 °C, ethanol/glycerol molar ratio of 16/1 and 0.61 g of catalyst. Conditions with high glycerol conversion (97%) were also identified. Finally, the continuous reactor operated under high pressure proved to be an excellent alternative to convert glycerol into ethers.