Solid/liquid equilibrium and flash point of fatty mixtures

Abstract

The study on the physicochemical properties of fatty materials has acquired a growing importance, mainly due to the incentive of their use in energy and nutrition. The efficient production and use of fatty compounds requires a good knowledge of their properties and phase behavior that are necessary for development of processes, especially in production steps such as extraction and refining, but also during storage of the final products. Solidliquid equilibrium data can be used to improve or propose new separation processes. Also the flash point is an important property that must be considered during storage, transportation and production of flammable compounds, such as biodiesel. This work aimed to study the solid-liquid equilibrium of binary mixtures consisting of fatty alcohols, fatty esters or fatty acids, and to evaluate the flash point of mixtures of ethyl esters, the major constituents of biodiesels, and ethanol, also present in biodiesel in residual levels. Flash points of ethyl esters, and also of the binary mixtures of ethyl esters with ethanol were determined experimentally. An empirical model for predicting the flash point of biodiesels as a function of composition and ethanol content was proposed. The solid-liquid phase diagrams of binary mixtures of fatty alcohol + fatty alcohol or fatty alcohols + fatty acid were determined experimentally by differential scanning calorimetry (DSC), using a linear heating rate, or by a stepscan DSC method, with the aim of investigating the occurrence of the eutectic, peritectic and metatectic reactions. X-ray diffraction and optical microscopy with temperature control techniques were applied to complement the understanding of the phase diagrams. The effect of pressure on the solid-liquid equilibrium was investigated for the binary mixtures of ethyl esters or fatty alcohols using an optical microscope coupled to a high pressure cell which allows the pressure increase up to 80 MPa. Margules 2 and 3-suffix and NRTL thermodynamic models were used for describing the liquidus line of the systems that presented peritectic point, and a predictive thermodynamic model was used to model the ESL function of pressure, which in both cases, gave a satisfactory fit compared to the experimental data.

Behavior analysis of the solid-liquid equilibrium of fatty systems through of the use diferential scanning calorimetry

“…Na indústria alimentícia é grande o número de misturas de óleos e gorduras utilizadas no processamento de alimentos cuja qualidade final está relacionada com as suas propriedades físico-químicas (COSTA, 2008) como a temperatura de fusão e a própria estrutura da fase sólida, ou seja, a forma polimórfica presente em determinda condição de temperatura e pressão. Sendo assim, o estudo do equilíbrio entre as diferentes fases sólidas e entre as fases sólida e líquida dos óleos e gorduras e de seus componentes é importante para o controle de qualidade, para desenvolvimento de produtos e de processos de separação, bem como para o dimensionamento de equipamentos de purificação de compostos através do processo de cristalização, por exemplo, cuja modelagem termodinâmica depende de informações do equilíbrio de fases sólido-líquido CARARETO, 2014). É devido ao significativo impacto desses compostos nos diferentes segmentos da indústria, diversos estudos buscam descrever a influência que os triacilgliceróis, ácidos graxos e álcoois graxos e alguns constituintes minoritários exercem sobre as propriedades físicas e químicas dos óleos e gorduras e de seus produtos finais (TH DE et al, 2004;COSTA et al, 2010;CARARETO et al, 2011;ZUO;WENG, 2011;.…”