Continuous catalyst free production of biodiesel from agro industrial waste with green solvents

Dissertação para obtenção do Grau de Mestre em Engenharia Química e Bioquímica

The aim of this thesis consists in the study of the production of biodiesel via catalyst free direct transesterification of spent coffee ground oil with supercritical methanol in a continuous process. Supercritical methanol is passed through a packed bed reactor with the spent coffee grounds. Inside the reactor supercritical methanol extracts the triacylglycerols, which are immediately transesterified into fatty acid methyl esters. Therefore, the extraction and transesterification processes take in a single step. It was demonstrated that, at the optimal conditions of operation of 533 K, 10 MPa and solvent flow of 1 ml/min, the maximum yield for the total process was 83%. The effect of supercritical CO2 (ScCO2) as co-solvent was also studied. When using carbon dioxide as co-solvent at supercritical conditions, higher yields were obtained at milder temperature conditions. A maximum yield for the total process of 86% was obtained at 314 K for extraction of oil, 473 K for the reaction into FAME, 10MPa, solvent flow of 4.13 ml/min and a volume fraction of ScCO2 in the solvent feed of 27%.