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Prediction of Density and Kinematic Viscosity of Biodiesel Fuels Produced from Rubber Seed Oil, International Journal of Renewable Energy and Environmental Engineering
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New evidence on the thermal decomposition of fatty acid methyl esters during biodiesel synthesis in supercritical conditions is presented. Thermal decomposition products were detected chromatographically, by applying the UNE-EN 14105:2003 standard, as a broad single peak during the determination of glycerides in the reaction samples. These degradation products could be quantified chromatographically by the above standard because the area of the peak was proportional to the disappearance of the polyunsaturated fatty acid methyl esters, which contain two or more double bonds (methyl linoleate and linolenate), generated during biodiesel synthesis from soybean oil. In the experimental conditions tested, thermal decomposition reactions of these unsaturated fatty acid methyl esters began to appear at 300°C/26MPa, and were more intense as the temperature rose. For its part, the main saturated fatty acid methyl ester (methyl palmitate) generated during the reaction was hardly decomposed at all in the experimental conditions tested and only began to disappear at 350°C/43MPa.
The densities and viscosities of the methyl esters of hexanoic, heptanoic, octanoic, decanoic and dodecanoic acids were determined
at temperatures ranging from 10 to 80C at 5C intervals. The densities of the methyl esters vary linearly with temperature.
When fluidities were plotted against molal volumes of the esters, smooth curves were obtained. Intrinsic volumes were determined
by extrapolation to zero fluidity. Based upon Hildebrand's equation, the B values, which represent a measure of the molecules
resisting transport of momentum, were calculated for each ester and found to be exponentially related to the temperatures.
A modified equation relating the fluidity with temperature was formulated. Excellent agreement was obtained between calculated
and experimental fluidities.
In this study, optimization of non-catalytic supercritical methanol reaction via response surface methodology analysis was carried out. Subsequently, the results obtained were compared with reported results of supercritical ethanol in order to investigate the effect of alcohol in supercritical alcohol reaction. Important variables such as reaction time, reaction temperature and molar ratio of alcohol to oil were optimized in order to obtain the optimum yield of biodiesel. Apart from single-parameter effect, response surface methodology also considered the influence of variable interactions in the experimental design. Hence, this method of analysis allows a comprehensive understanding of the process by minimal number of experimental runs. Results obtained from optimization studies showed that supercritical methanol reaction can achieve optimum yield (81.5%) at relatively lower reaction time compared to supercritical ethanol process (79.2%).
Transesterification of Jatropha oil using supercritical methanol and in absence of a catalyst has been studied under different conditions of temperature (from 512 to 613K), pressure (from 5.7 to 8.6MPa) and molar ratio of alcohol to oil (from 10 to 43 mol alcohol per mol oil). The reaction products were analyzed for their content of residual triglycerides, glycerol, monoglycerides, diglycerides, esters and free acids by high performance liquid chromatography (HPLC), thin layer chromatography (TLC) and titration against KOH.The results have revealed that 100% yield of esters can be obtained using super critical methanol within four min only, at a temperature of 593K and under a pressure of 8.4MPa pressure. The molar ratio of methanol to oil was 43:1.
In the present study, non-catalytic supercritical methanol (SCM) reaction was utilized to produce biodiesel from palm oil. The effects of free fatty acids and water content on the yield of biodiesel were investigated and subsequently compared with conventional catalytic reaction. In addition, the feasibility of utilizing co-solvents to reduce the operating conditions needed in SCM was carried out as well. Results show that catalytic reaction suffers from low yield with the presence of high water content in oil. However, it was found that the yield of SCM did not drop but instead increased with the increment of water content. Hence, SCM has been shown to have a high tolerance for water content in oil, which is important in order to utilize other sources of triglycerides such as waste cooking oil. On the other hand, non-polar solvents such as heptane were found to have potential to decrease the temperature required in the reaction.
Saturated fatty acid methyl esters from acetate to arachidate, methyl oleate, linoleate, linolenate, and erucate have been
prepared in high purity. Densities, refractive indices, dispersions, ultrasonic sound velocities, and dielectric constants
have been measured in the liquid state at 20 and 40C. In this first communication, the densities of the saturated compounds
have been correlated with the Smittenberg relation. The following relations were derived: d
20
4
= 0.85407 + 0.18494/ (n + 0.096) and d
40
4
= 0.84225 + 0.12904/(n-0.408). Molar volumes have been computed and checked for additivity.
Equations have been developed for the calculation of molar refraction, molar volume or density, and refractive index for liquid
fatty acids and fatty acid derivatives in relation to two parameters, carbon chain length, and unsaturation. Particular attention
has been given to the applicability of the equations to families of compounds in which the unsaturated members contain onlycis double bonds and in which the ethylene units of the polyene members are interrupted by methylene groups. The equations are
sufficiently accurate to have considerable utility in establishing the identity, purity, or structure of various fatty acid
derivatives.
It was indicated that, with more data, similar relationships may be developed which will be useful in characterizing some
types of mixtures of fatty acid derivatives.
An approximate relationship between molar volume and temperature for fatty acids and derivatives was also devised.
To develop reliable models for the densities and viscosities of biodiesel fuel, reliable data for the pure fatty acid esters are required. Densities and viscosities were measured for seven ethyl esters and eight methyl esters, at atmospheric pressure and temperatures from (273.15 to 363.15) K. A critical assessment of the measured data against the data previously available in the literature was carried out. It is shown that the data here reported presents deviations of less than 0.15 % for densities and less than 5 % for viscosities. Correlations for the densities and viscosities with temperature are proposed. The densities and viscosities of the pure ethyl and methyl esters here reported were used to evaluate three predictive models. The GCVOL group contribution method is shown to be able to predict densities for these compounds within 1 %. The methods of Ceriani and Meirelles (CM) and of Marreiro and Gani (MG) were applied to the viscosity data. It is shown that only the first of these methods is able to provide a fair description of the viscosities of fatty acid esters.
Currently, most of the biodiesel is produced from the refined/edible type oils using methanol and an alkaline catalyst. However, large amount of non-edible type oils and fats are available. The difficulty with alkaline-esterification of these oils is that they often contain large amounts of free fatty acids (FFA). These free fatty acids quickly react with the alkaline catalyst to produce soaps that inhibit the separation of the ester and glycerin. A two-step transesterification process is developed to convert the high FFA oils to its mono-esters. The first step, acid catalyzed esterification reduces the FFA content of the oil to less than 2%. The second step, alkaline catalyzed transesterification process converts the products of the first step to its mono-esters and glycerol. The major factors affect the conversion efficiency of the process such as molar ratio, amount of catalyst, reaction temperature and reaction duration is analyzed. The two-step esterification procedure converts rubber seed oil to its methyl esters. The viscosity of biodiesel oil is nearer to that of diesel and the calorific value is about 14% less than that of diesel. The important properties of biodiesel such as specific gravity, flash point, cloud point and pour point are found out and compared with that of diesel. This study supports the production of biodiesel from unrefined rubber seed oil as a viable alternative to the diesel fuel.