Thermodynamics of biofuels: Excess enthalpies for binary mixtures involving ethyl 1,1-dimethylethyl ether and hydrocarbons at different temperatures using a new flow calorimeter (original) (raw)
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Experimental Study of Thermodynamic Properties of Biofuel Components
2024
The density () and speed of sound (u) of two main components of biofuels, methyl laurate and methyl stearate, were measured at temperatures from (283 to 353) K and from (313 to 353) K at atmospheric pressure, respectively. An Anton Paar DSA 5000 М sound-speed analyzer, has been used to simultaneously measurements of the density and speed of sound of the methyl laurate and methyl stearate as the primary components of biodiesel fuel. The measured values of density and speed of sound were used to calculate other derived thermodynamic properties such as adiabatic coefficient of bulk compressibility, coefficient of thermal expansion, isothermal coefficient of bulk compressibility, isochoric and isobaric heat capacities, enthalpy and entropy difference, partial temperature derivative of enthalpy, entropy, and the partial specific volume derivatives of internal energy (internal pressure), of the methyl laurate and methyl stearate as a function of temperature. The overall uncertainties (at the 95 % confidence level) of the reference correlations of the density and speed of sound of methyl laurate and methyl stearate are 0.025 % and 0.045 %, respectively.
Standard Reference Data for the Thermophysical Properties of Biofuels
Journal of ASTM International, 2010
The thermophysical properties of biofuels are required for the efficient design of their chemical processing, distribution, and utilization. We provide a review of biofuel properties research at the National Institute of Standards and Technology ͑NIST͒. We are expanding two Standard Reference Databases to include biofuels. The ThermoData Engine will collect and evaluate all published property data on biofuel components. The NIST Reference Fluid Thermodynamic and Transport Properties database is a calculational database providing properties of biofuel components and blends based on thermodynamic and transport models. The property models in the databases implement an equation of state approach based on well defined reference fluids. Complex mixtures, including blends of biofuels with conventional fuels, are modeled as "surrogate blends," i.e., a blend of perhaps a dozen components that captures the essential characteristics of a complex fuel. Surrogate blends are formulated from a "suite" of wellcharacterized pure compounds. Property measurements for the pure compounds in the surrogate suite include but are not limited to density, speed of sound, and viscosity. We have also carried out measurements on actual biofuel samples. A recent extension of the distillation curve that we have developed at NIST is proving very valuable in characterizing fuels. This "advanced distillation curve method" provides much more quantitative information than the traditional method, including chemical characterization of the different "cuts" as the distillation proceeds. We present examples of our measurements and models completed to date and outline future plans.
Journal of Chemical & Engineering Data, 2009
Experimental excess enthalpies of the ternary system dibutyl ether (DBE) + cyclohexane + 1-butanol and the corresponding binary systems at 298.15 K are reported. A quasi-isothermal flow calorimeter has been built and tested to make the measurements. All the binary and the ternary systems show endothermic character. The experimental data have been fitted using a polynomial equation for the binary and ternary systems. The values of the standard deviation indicate good agreement between the experimental results and those calculated from the equation. † Part of the special section "2008 European Conference on Thermophysical Properties".
Journal of Chemical & Engineering Data, 2000
Experimental data are reported at 298.15 K of excess molar volumes V E and of excess molar enthalpies H E for binary and ternary mixtures of an alkanol (1-propanol or 1-butanol), an ether (diisopropyl ether or dibutyl ether), and an alkane (heptane). A vibrating-tube densitometer was used to determine V E. H E was measured using a quasi-isothermal flow calorimeter. The experimental results are used to test the applicability of the modified UNIFAC model for correlating H E and of the ERAS model for describing both V E and H E of binary mixtures as well as for predicting the excess properties of ternary mixtures containing an alkanol, an ether, and an alkane. For all investigated binary systems, a better description of the experimental data was achieved with the ERAS model in comparison with the modified UNIFAC model.
Energetic Efficiency of Biofuel Production
Green energy and technology, 2018
Both primary and secondary biofuels have to assure specified requirements concerning their properties. Since the biofuels can exist in solid, liquid, and gaseous forms, some of the characteristics are very different, some are universal for all types of fuels. The variety of properties for technical, as well as market purposes are carefully standardized [1]. The most important property is calorific value (heating value). As shown in numerous research the calorific value results of chemical composition of a fuel. Many formulas have been proposed to describe the correlation between heating value, and elemental or on proximate data on the fuel composition. Two main cases of calorific value are distinguished: the higher heating value (also called gross calorific value) and low heating value (also called net calorific value). Those calorific values differ because the majority of fuels contain hydrocarbons, which causes the combustion gases to contain water. Evaporation of this water consumes some part (dependent upon hydrogen content) of energy released during combustion of the fuel. High calorific value is determined in such a way that the corresponding amount of latent heat of evaporation is not subtracted from reaction heat. Low calorific value, in turn, corresponds to this amount of energy, which remains after evaporation of water, and is available to the user. Another contribution of the same type comes from moisture-the molecules of water absorber by the fuel. The methods of determination of both calorific values as well as their precise definitions are given in appropriate standards (e.g., ISO1213-2:1992) [2]. Correlation between the chemical composition of a fuel and its calorific value was first studied by Dulong, whose historical equation can be written in the following form [3]:
Industrial & Engineering Chemistry Research, 2009
This work has been undertaken to obtain new thermochemical data for ethanediol and propanetriol acetates and to improve the group contribution methodology for the prediction of the thermodynamic properties of compounds relevant to biodiesel. Standard molar enthalpies of formation in the gaseous state of a series of 1,2-ethanediol monoacetate, 1,2-ethanediol diacetate, and 1,2,3-propanetriol triacetate have been obtained from combustion calorimetry and results from the temperature dependence of the vapor pressure measured by the transpiration method. To verify the experimental data, ab initio calculations of all compounds have been performed. Enthalpies of formation derived from the Gaussian 03 second-order Møller-Plesset (G3MP2) method are in good agreement with the experimental results. The strength of the hydrogen bond in 1,2ethanediol monoacetate and in 1,2-ethanediol have been obtained using ab initio calculations and the group additivity method.