Saponificação de ácidos graxos e triacilglicerídeos: avaliação por espectrometria de infravermelho

Abstract

Processing by flotation in mineral industry, mainly in the case of apatite phosphate ores, vegetable and mineral oils from surplus or waste from food industry, cosmetics and cellulose, have been used widely. These oils can be used as raw materials for the production of collectors, but it is necessary for them to be previously saponified. This work was conducted to develop an effective methodology for the saponification of fatty acids and triacylglycerides, because in Brazil there is a wide availability of renewable materials for the manufacture of soaps (vegetable oils and animal fats). Verification of the saponification efficiency was conducted by an instrumental method, infrared spectrometry (IRS). There are basically 5 methods of saponification of fats and oils, but in this work three of these were used, because they are extreme methods, in laboratory scale. Infrared spectrometry (FTIR) was used in the transmission method with a preparation variation using both the liquid and the solid phases. Method number 4, which utilizes hot NaOH ethanol solution under reflux was fully effective for the more difficult saponification, which it is for triglycerides (soybean oil). Other important results for this method were: 1. A small amount of water (around 5%) has no adverse effect on triglyceride saponification, so commercial alcohols can be used. 2. The drying temperature recommended for analysis of the produced soap by IRS is around 100°C and must be rapid. Method number 1, which uses aqueous NaOH solution at room temperature, was effective only for fatty acid (oleic acid) in short-term. For triglycerides, the saponification was only partial. However, after several days, keeping the same temperature, there is complete saponification. This can be interesting because it would reduce the cost of heating and the ethyl alcohol input, provided that the time factor was not critical. Method number 2 is similar to method 1, but the reaction is processed at 70-75°C; saponification results were practically the same as with this method.