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Abstract: A continuous process for biodiesel production has been simulated using Aspen HYSYS V7.0 software. As fresh feed, feedstocks with a mild acid content have been used. The process flowsheet follows a traditional alkaline transesterification scheme constituted by esterification, transesterification and purification stages. Kinetic models taking into account the concentration of the different species have been employed in order to simulate the behavior of the CSTR reactors and the product distribution within the process. The comparison between experimental data found in literature and the predicted normalized properties, has been discussed. Additionally, a comparison between different thermodynamic packages has been performed. NRTL activity model has been selected as the most reliable of them. The combination of these models allows the prediction of 13 out of 25 parameters included in standard EN-14214:2003, and confers simulators a great value as predictive as well as optimization tool. [Copyright &y& Elsevier]

Abstract: Biodiesel density is a key parameter in biodiesel simulations and process development. In this work we selected, evaluated and improved two density models; one theoretical (Rackett–Soave) and one empirical (Lapuerta’s method) for methanol based biodiesels (FAME) and ethanol based biodiesel (FAEE). For this purpose, biodiesel was produced from vegetable oils (sunflower, rapeseed, soybean, olive, safflower and two other commercial mixtures of vegetable oils) and animal fats (edible and crude pork fat and beef tallow) using both methanol and ethanol for the transesterification reactions, and blended to get 21 FAME and 21 FAEE, reporting their density and detailed composition. Bibliographic data have also been used. The Rackett–Soave method has been improved by the use of a new acentric factor correlation, whereas the parameters of the empirical one are improved by considering a bigger density data bank. Results show that the evaluated models could be used to estimate the biodiesel density with a good grade of accuracy but the performed modifications improve the accuracy of the models: ARD (%) for FAME; 0.33, and FAEE; 0.26, both calculated with the modification of Rackett–Soave method and ARD (%) for FAME; 0.40 calculated with the modification of Lapuerta’s method. [Copyright &y& Elsevier]

• Semichemical pulping straw black liquor depolymerization for antioxidant production. • Direct extraction of liquid produces the antioxidant with highest effect on biodiesel. • Antioxidant potential increases with temperature at 225–300 °C. • Biodiesel oxidation stability increased as much as 250% by adding 1 wt% additive. • Antioxidant effect is not explained by the volatile compounds identified. Black liquor obtained from semichemical pulping of barley straw was depolymerized in a stirred autoclave reactor, at temperature in the range of 250–300 °C while varying the amount of catalyst (zeolite Y). Three fractions were obtained from the depolymerized liquor: a fraction directly extracted from the liquid with isopropyl acetate (Lα), a second one which contains the heaviest compounds precipitated from the liquid at pH 1 (Lβ) and a third one obtained by extraction of the acidified liquid (Lγ). The three fractions were tested as antioxidant additives for biodiesel, blending them individually at a dosage of 1 wt%. The antioxidant activity was Lα > Lγ > Lβ. The Lα fraction showed the highest antioxidant activity, increasing the oxidation stability time over neat biodiesel from 150 to 250%. The phenolic volatile content of the fractions (measured by GC/MS) decreased in the same rank (Lα > Lγ > Lβ), so there doesn't seem to be correlation between the volatile content and the increase of antioxidant activity. Depolymerizarion temperature was the most influential parameter, showing a clear positive effect on the antioxidant activity for the three fractions. [ABSTRACT FROM AUTHOR]