Biodiesel de óleo residual : produção através da transesterificação por metanólise e etanólise básica, caracterização físico-química e otimização das condições reacionais

Abstract

Today's environmental problems require action on the part of mankind to minimize environmental pollution. One way to slow down such disturbance is the use of "clean" fuels like biofuels. Within this scope this work contributes by studying the production of biodiesel through the reuse of frying oil, which generates harmful waste. The present work was the transesterification of biodiesel from used frying oil by basic catalysis, via ethyl and methyl routes. Biodiesel has its physico-chemical variables studied and their optimal reaction. Through the technique of thermal expansion coefficients of methyl and ethyl biodieseis and the corresponding mathematical algorithms for each of biodieseis can observe significant differences between the mathematical models established assumptions compared to the results by EN 14214. The optimization of reaction conditions studied the variables: molar ratio (RM), speed, reaction time, catalyst type, catalyst concentration and temperature. Methylic biodiesel from frying oil (BMR) for the last two mentioned are the ones that were more operational importance, while for the ethylic biodiesel from frying oil (BER) of catalyst concentration and time are more relevant. The conditions of maximum yield were determined by factorial design: potassium hydroxide (KOH) as catalyst; RM de 7:1 alcohol:oil; rotation of 80 rpm, catalyst concentration of about 1.7% (m/m), temperature 48 ° C for the BMR, and 30 oC for the BER, and reaction time of 30 minutes for BER, and 60 minutes for BMR. The process sets a tolerance for the variables of greatest influence on the reaction, which means that small quantitative variations of individual conditions do not affect the overall yield. The content of free fatty acids changes the reaction yield, ethanolysis being more sensitive to this variable. The characterizations made to specifications for both biodiesel met the requirements of National Petroleum Agency (ANP). The thermogravimetric analysis showed the weight loss along with the volatilization and decomposition of the sample. The infrared showed the main bands related to methyl and ethyl esters. Chromatography confirmed the transformation of triglycerides into esters with high ester content of 99.99%. As the main composition of linoleic acid esters of about 46%, similar to soybean oil.