Análise da produção de biodiesel a partir da etanólise de óleo refinado e residual

Abstract

Biodiesel is chemically defined as alkyl esters of fatty acids derived from vegetable oils, animal fats or residual fats. However, the high cost of raw materials when using refined vegetable oils has made it economically unfeasible to produce this biofuel. In view of this, many studies have focused on the use of low value-added raw materials, such as frying waste oils, showing the technical feasibility and environmental benefits of using a waste as raw material. The most commonly used process for its production is transesterification in an alkaline medium. In this process, vegetable oils or animal fats react with alcohol, with methanol and ethanol being the most commonly used in alkaline media (usually NaOH or KOH) producing alkyl esters (biodiesel) and glycerin as a by product. In this work, the alcoholysis of refined soybean oil and frying oil was employed using ethanol as the transesterification agent with basic and enzymatic catalysis. Ethyl transesterification with enzymatic catalysis was performed under different experimental conditions: ethanol:oil of 1:1, 2:1, 3:1, 4:1, 5:1 and 6:1 molar rations (MR) and reaction times of 1, 2, 24, 48 and 72 hours, with a fixed amount of 10 g of residual oil, use of immobilized lipase (Candida antarctica) with a fixed amount of 5% in relation to the oil mass used, at a temperature of 30ºC and agitation of 200 rpm. The ethanolysis of refined soybean oil was analyzed through experimental planning whose variables were: molar ratios (MR) of 3:1, 6:1, 9:1 and 12:1 and temperatures of 30 and 40 ºC. The reactions were conducted in erlenmeyer’s with capacities of 150 mL containing 50 g of refined oil and 1 % of catalyst (sodium hydroxide) in relation to the measured oil mass, with quantities of alcohol determined by the planning of experiments, maintaining a fixed agitation of 200 rpm. The best results corresponded to conditions at a temperature of 30ºC and higher molar ratios, achieving 92.28 % ester yield using 9:1 and 30ºC MR. The two best results obtained in the transesterification of refined oil in the 30ºC condition, molar ratios of 9:1 and 12:1, were applied to the alkaline alcoolysis of the residual oil, with the use of 10 g of oil. Between the two applied experiments, the 9:1 molar ratio (MR) obtained the best residual oil ester yield (82.58%). Kinematic viscosity analyses of the ethyl ester samples obtained were performed to assess compatibility with the current quality specifications. The results of the procedures performed demonstrate that the ethanolysis of soybean oil and residual oil in alkaline media can be successfully conducted under the conditions studied.