Product Separation after Chemical Interesterification of Vegetable Oils with Methyl Acetate. Part II: Liquid–Liquid Equilibrium

Abstract

The aim of this work was the removal of diacetin, monoacetin, and glycerol from biodiesel−triacetin mixtures using liquid−liquid extraction with water. Liquid−liquid equilibrium was predicted using UNIFAC based models for the activity coefficient calculations. These data have been corroborated with experimental information from all possible binary, ternary (water, triacetin, and biodiesel), and overall (diacetin, monoacetin, glycerol, water, triacetin, and biodiesel) mixtures. The experimental determination of the diacetin, monoacetin, and glycerol distribution factor and their selectivity with respect to triacetin allows the operating temperature set at 27.5 °C. After that, it was determined that three washing steps, with a water to feed mixture mass ratio of 0.05 (per stage), were necessary for the effective elimination of these compounds. The final composition of the raffinate phase was 94.6 wt % biodiesel and 5.1 wt % triacetin. The extract phase consisted of a mixture of 59.2 wt % acetins and glycerol and 40.7 wt % water.

Liquid‐Liquid Phase Equilibrium of Glycerolysis Precursors: Experimental and Modeling Study

“…This justification is in agreement with the results of Gomes et al. 10, where the authors attributed MO to behave as a phase transfer agent, which necessarily aims towards the formation of associated or dissociated molecules in the solution.…”

“…Upholding the above two empirical evidences, it can be concluded that the mutual presence of hydroxyl groups in glycerol and MO in the present investigated system might promote the formation of an associated or dissociated complex between these species, favoring the glycerol solubility in the fatty phase. This justification is in agreement with the results of Gomes et al [10], where the authors attributed MO to behave as a phase transfer agent, which necessarily aims towards the formation of associated or dissociated molecules in the solution.…”

“…One of the key requirements to get good system predictions is the use of precise models. Similar systems have been described by some authors using UNIFAC [10,11], while others have applied UNIQUAC [12], NRTL [13,14], and COSMO-SAC [15]. Although the NRTL and UNIQUAC models provide good data correlation, the UNIFAC-LLE model has higher predictive power, as it describes the interaction between functional groups, providing the model with more versatility for data prediction [16,17].…”

Biodiesel at the Crossroads: A Critical Review

“…About the economic viability of the process of interesterification of triglycerides with methyl or ethyl esters Authors studied several reaction conditions, i.e., oil/methyl acetate molar ratio in the range 1:3 to 1:9, and temperatures in the range of 40-200 • C. This biofuel exhibited similar properties as biodiesel, although the obtention process of Gliperol improves the yield, the efficiency, and the economic feasibility of the conventional biodiesel obtention process. After Gliperol was patented, a lot of subsequent studies that use homogeneous basic catalysts, such as potassium hydroxide, potassium methoxide, and polyethylene glycolate have been carried out [56][57][58][59][60][61][62][63][64][65][66][67]. These studies manifested that the reaction conditions to obtain Gliperol are similar to that for the production of Biodiesel.…”