Manuel Félix Alfaro García

Prediction of normalized biodiesel properties by simulation of multiple feedstock blends

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.

Methanolysis and ethanolysis of animal fats: a comparative study of the influence of alcohols.

Biodiesel from animal fats with methanol and ethanol was produced in the presence of sodium methoxide and sodium ethoxide as catalysts. Two samples of pork fats and one natural beef tallow were directly transesterified with a good final product yield; 87.7%, 86.7% and 86.3% for methanolysis and 78.4%, 82.6% and 82.7% for ethanolysis, respectively. Methyl ester content was also determined, being higher than 96.5 wt. % for all the samples prepared, the presence of natural C17:0 in animal fats makes it necessary to correct the method proposed in the standard EN 14103 (2003). Biodiesel density at 15 oC of the samples was between 870 and 876 kg/m3, within the acceptance range of standard EN 14214, dynamic viscosity at 40 oC of the produced biodiesels, in the range of 4.5 to 5.16 mm2/s, also fulfills requirements of EN 14214 standard. The iodine value is much lower than the superior limit established by EN 14214 standard but oxidation stability (OSI) is lower than the required limit, 6 h, of the standard, which can be attributed to the lack of natural antioxidants in tallows.

Sobolev orthogonal polynomials: balance and asymptotics

Let µ0 and µ1 be measures supported on an unbounded interval and Sn, n the extremal varying Sobolev polynomial which minimizes