Purificação da glicerina obtida como coproduto na produção de biodiesel com óleo de soja refinado

Abstract

This study aims to develop methologies for purifying glycerin coproduct generated in the production of biodiesel by transesterification of refined soybean oil. It was performed pre-purification of glycerine by acid hydrolysis to remove the catalyst and impurities such as fatty acids testing for subsequent purification of this glycerine with different commercial adsorbents (activated carbon, bentonite clay and attapulgite). The first part of treatment consisted of the removal of biodiesel and the alcohol used in the transesterification reaction. The second step was based on the hydrolysis of glycerin as a pre-purification with the addition of concentrated phosphoric acid in a molar ratio phosphoric acid / catalyst ratio of 2:3. Acid hydrolysis was important in removing soaps, esters, fatty acids and residues of the basic catalyst. Analyzing the processes of purification can be seen that there was an increased glycerol content of 54.3% to 64.2% during the hydrolysis process for removal of catalyst residues and fatty acids. The process of stirring and heating at 80 ° C for 3 h showed an increase of 8.5% in glycerol content (72.7%). The highest levels of glycerol by purification with bentonite, attapulgite and activated carbon were 73.7 (1% m/m), 75.4 (1% m/m) and 95.8% (3% m/m) respectively. Increasing the amount of activated carbon 0.5% to 3% using a heating time of 1h caused an increase in the glycerol content of 76.0 to 95.8% respectively. Times higher than on hour did not indicate significant changes in the content of glycerol. The best glycerol content was obtained by using 3% activated carbon, 1 hour of stirring and heating to 80 ° C (95.8%).