This work focused on the development of the phase equilibria models required to describe the behavior of mixtures involved in the synthesis of tributyl citrate (TBC) via esterification of citric acid (CA) and butan-1-ol (BuOH). Vapor−liquid equilibrium (VLE) for the mixture TBC−BuOH, liquid−liquid equilibrium (LLE) for the ternary mixture TBC− H 2 O−BuOH, and solubility data for the mixture CA−BuOH−TBC were measured at different temperatures. The thermodynamic consistency was verified with the Wisniak test for VLE data, and the LLE data exhibited linear behavior in an Othmer and Tobias plot. Anhydrous citric acid was characterized by differential scanning calorimetry exhibiting a melting point of 424.9 K, an enthalpy of fusion of 59.2 kJ/mol, an average heat capacity of 255.48 J/mol•K in the evaluated temperature range (320−375 K), and a change of heat capacity from solid to liquid of 236 J/mol•K. Together with reported equilibrium data from the open literature, and the evaluated physicochemical properties, the measured equilibrium data were regressed with the UNIQUAC equation to fit the binary interaction parameters of the components in the mixture. The obtained model agrees well with the whole set of experimental data and can be used for further process design.
Dibutyl citrate (DBC) was synthesized via partial esterification of citric acid (CA) with n-butanol (BuOH) and characterized for the first time. Then, the monoacid diester was isolated from the reactive mixture by using a pH-controlled solvent extraction procedure. The identity of the obtained product was verified by NMR spectroscopy, finding that it corresponds to a mixture of asymmetric and symmetric isomers. The obtained product was characterized by thermogravimetric and differential scanning calorimetry analysis and by density and viscosity measurements. As per the calorimetric analysis, DBC exhibited a crystallization point below 213 K, a decomposition temperature of 541 K, and an average heat capacity of 2.461 kJ/kg K in the evaluated temperature range (320–375 K). The average liquid density and viscosity in the studied temperature interval (298–313 K) were 1.122 g/cm3 and 2.03 Pa·s, respectively. Additionally, isothermal vapor–liquid equilibrium data (P–x) in mixtures containing the obtained DBC and BuOH were measured at 313, 323, and 333 K. Experimental data were used to fit UNIQUAC interaction parameters for the binary DBC–BuOH. The regressed model showed good agreement with experimental results, making it suitable for further process design and simulation. The obtained data can be used in the development of processes for citrate plasticizer production and in the development of separation processes for DBC.
The transesterification reaction of sucrose and fatty acid methyl esters to produce sucroesters was experimentally evaluated using commercial emulsifiers as compatibility agents. Reactions were carried out at temperatures between 100 and 140°C, using emulsifier concentrations in the range of 5 to 15 %wt, and potassium carbonate as catalyst. Fatty acid methyl esters consumption and sucroesters production was monitored by HPLC analysis of samples. Methyl esters conversions around 40 % were obtained with 68 %wt monoester content in sucroesters mixture. Despite the reaction times were reduced by operating at high temperatures and high emulsifier's concentration, multiple substitution and color degradation were observed. Higher productivities of sucroester and higher selectivity to monoesters were obtained when potassium palmitate was used as contacting agent. The lower monoester content in the final product was obtained when using a commercial sucroester emulsifier. Results of this study can be used for preliminary process design in a solvent-free production of biobased sucroesters.Keywords: Sucroester, solvent-free, transesterification, emulsifiers, Heterogeneous. RESUMENEn este trabajo se evaluó experimentalmente la reacción de transesterificación entre sacarosa y ésteres metílicos de ácidos grasos para producir ésteres de sacarosa, usando emulsificantes comerciales como agentes de compatibilidad. Las reacciones se llevaron a cabo a temperaturas entre 100 y 140°C, usando concentraciones de emulsionantes en un rango entre 5 y 15%p, y carbonato de potasio como catalizador. El consumo de ésteres metílicos de ácidos grasos y la producción de ésteres de sacarosa fueron seguidos por HPLC. Se obtuvieron conversiones de palmitato de metilo alrededor del 40% y ésteres de sacarosa de 68%p de monoéster. A pesar de que los tiempos de reacción se reducen operando a altas temperaturas y altas concentraciones de emulsionante, se observó que el producto final sufría degradación de color. Las mayores productividades de ésteres de sacarosa y la mayor selectividad hacia monoésteres fueron obtenidas cuando se usó palmitato de potasio como agente de contacto. El menor contenido de monoéster en el producto final fue obtenido usando éster de sacarosa comercial. Los resultados de este estudio pueden ser usados por diseño conceptual preliminar en la producción libre de solvente de ésteres de sacarosa biobasados. How to cite: Gutierrez M. F., Orjuela A., Rivera J. L., Suaza A. (2018). Production of sucroesters using solvent-free reactive systems containing emulsifiers.
This work describes the conceptual design and a pilot-scale validation of a reactive distillation column for tributyl citrate (TBC) production by esterification of citric acid (CA) with n-butanol (BuOH). The conceptual design was carried out using novel reactive residue curve maps for mixtures of six components. Subsequently, a computational sensitivity analysis based on validated kinetic and phase equilibrium models enabled identifying critical design and operating variables to assess during experiments. Further pilot-scale experiments were performed according to a Box–Behnken design. The highest productivity at the pilot scale was obtained for a reflux ratio of 0.17, a CA/BuOH mole ratio of 1:13, and a feed flow of the reactive mixture of 4.9 kg/h. These conditions resulted in a CA conversion above 98.8%, a TBC yield of 52%, and a productivity of 24.4 kg/h/m3. It was verified that the process can successfully operate with azeotropic BuOH as feedstock and a prereactor, improving selectivity toward TBC.
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