Phase equilibrium data and modeling of ethylic biodiesel, with application to a non-edible vegetable oil

Abstract

a b s t r a c tContributing to extending the knowledge for the design and operation of biodiesel production processes, isobaric PTxy vapor-liquid equilibria data of ethanol + ethyl hexanoate, 1-pentanol + ethyl hexanoate and 1-pentanol + ethyl octanoate at two different pressures are reported for the first time. Consistency tests were applied to attest the quality of the collected data, for these especially complex measurements. Besides that, vapor pressures of the pure ethyl esters have also been measured. For modeling purposes, the Lyngby and Dortmund UNIFAC variants were used to predict the VLE phase diagrams. Generally, the predictions are of very good quality, being the UNIFAC-Do (Dortmund) better, as the deviations in temperature and vapor compositions are always lower to 1.0 K and 0.020, respectively. Checking for the viability for extrapolations in pressure, CPA EoS was also applied to the modeling of the experimental data with very good results. Finally, aiming at examining the model capabilities to describe multicomponent systems, VLE measurements involving two alcohols and the fatty acid ethyl ester mixture obtained from non-edible vegetable oil have been carried out showing the good performance of the predictive models.

Phase equilibria of mixtures involving fatty acid ethyl esters and fat alcohols between 4 and 27 kPa for bioproduct production

“…A detailed description of the ebulliometer of which a schematic diagram is provided in Fig. 1 is available in the paper by Muhammad et al [12]. The uncertainties on the measured temperature and pressure are, respectively, ±0.01 K and ± 0.013 kPa (±0.1 mmHg).…”

“…Indeed, cubic equations of state with GC-estimated binary iteraction parameters were applied successfully to systems involving molecules similar to biodiesel or biolubricants, but under moderate to highpressures with supercritical carbon dioxide [27][28][29]. Among the G E -GC approaches, namely original UNIFAC [30] and its variants (Lyngby modified UNIFAC [31], Dortmund modified UNIFAC [32][33][34], linear UNIFAC [35]), the regularly updated Dortmund modified UNIFAC model [32][33][34] was selected as it has yielded excellent VLE predictions for complex mixtures involving ethyl esters and alcohols [12,14,36]. Accordingly, the implicit γ-φ approach leads to express the vapor-liquid equilibrium condition by:…”

“…Robust process simulation of biolubricants production from biodiesel requires quantitative and reliable information about the vapor-liquid equilibria (VLE) of mixtures containing alcohols and fatty acid esters, as well as the liquid-liquid and vapor-liquid-liquid equilibria with the presence of glycerol, and eventually water, when dealing with the preliminary biodiesel production step [7,12,13]. Nevertheless, despite the recently published extensive work on phase equilibria involved in biodiesel production [7,13,14], VLE information for the biolubricant production operating under low pressure is still lacking.…”

“…Nevertheless, despite the recently published extensive work on phase equilibria involved in biodiesel production [7,13,14], VLE information for the biolubricant production operating under low pressure is still lacking. As an illustration, Table 1 [12,[15][16][17][18][19][20] gives an overview of the low-pressure VLE related to biodiesel components that were published over the past 10 years. No similar information was found for biolubricants.…”

Comparison Between Experimental and Simulated Results of Biodiesel Production by Reactive Distillation and Energetic Assessment

“…The group contribution method modified UNIFAC-Do (Dortmund) has been reported by a number of researchers to be adequate for a wide range of simulations. This is because it provides reliable results and comprises a significant range of applicability for solid-liquid equilibria, vapor-liquid equilibria, activity coefficients at infinite dilution, azeotropic data, and excess enthalpies (Gmehling et al, 2002;Kuramochi et al, 2009;Muhammad et al, 2017). Muhammad et al (2017) stated that, for biodiesel modeling purposes, the UNIFAC-Do usually provides good results because the deviations in terms of temperature and vapor compositions are lower than 1.0 K and 0.020, respectively.…”