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Thermophysical Properties of Biofuels


The Thermophysical Properties Division has begun a program to develop thermophysical property data for the biofuels. Transportation fuels will undergo major changes in the coming years, and the thermophysical properties of biofuels are required for the efficient design of every step in their production, distribution, and utilization. The objective of this work is to provide reliable consensus data to help enable this major transition. In the current period, we hosted a workshop among stakeholders to help establish priorities. We have initiated work in the three major areas of the research program, namely data, measurement, and modeling. Our work will ultimately lead to at least two SRD databases for the biofuels.



Our focus will be on properties relevant to the refining, blending, and engine performance areas; thus, our data, models, and software tools will be useful to a broad range of scientists and engineers. Many of these properties will also be important for flow metering (i.e., legal metrology). Our work will be enabling. It will establish a thermodynamic foundation for the biofuels, and will thus impact the billions of dollars the U.S. spends each year on transportation fuels. More significantly, the widespread adoption of biofuels would reduce the emissions of global warming gases. Policy and economic decisions require accurate and consensus thermophysical property data.

Objective and Goals

Transportation fuels will undergo major changes in the coming years, and liquid fuels derived from biological materials have very bright prospects. The thermophysical properties of biofuels are required for the efficient design of every step in their production, distribution, and utilization. These properties include the thermodynamic properties (density, heat capacity, enthalpy, etc.) and the transport properties (viscosity, thermal conductivity, etc.). There is presently no comprehensive, consensus source of reliable property data for use by industry, and that is the void we propose to fill.

Research Activities and Technical Approach

The technical plan is based on three areas of activity, proceeding in parallel. The end products will be disseminated as SRD databases, including the collection and evaluation of existing literature data. Feeding into the databases will be the modeling of biofuel blends and their constituent pure components. An experimental effort will provide data needed to develop and refine the models.

The modeling will be based on the concept of a "surrogate blend," i.e., a blend of 10 to 20 components that captures the essential characteristics of a complex fuel. Surrogate blends will be formulated from a "suite" of well-characterized pure compounds, including alcohols and esters from biological sources as well as hydrocarbons representative of petroleum or synfuels. To define a suitable surrogate, a fuel must be characterized in terms of its distillation curve, combustion characteristics, and other behaviors. The simple distillation curve measurement has been extended recently at NIST to include much more quantitative information.

Models are based on experimental data. Extensive measurements on reference systems will provide the high-quality data needed for model development. Rapid measurements will characterize the many types of mixture interactions present in the fluid suite.

We have begun work in all three areas. In the "Data" area we have collected the literature data for the five most important fatty acid methyl esters (FAMEs) that comprise biodiesel derived from vegetable oils. These data have been incorporated into Thermo Data Engine (TDE-SRD 103), and are part of the TDE evaluations..

In the "Measurements" and "Modeling" areas we made initial measurements for the five fatty acid methyl esters (FAMEs) that are the primary constituents of soy-based biodiesel fuel, namely, methyl palmitate, methyl stearate, methyl oleate, methyl linoleate, and methyl linolenate. The measurements of density, speed of sound and boiling point were combined with literature data to develop an equation-of-state approach to modeling the thermodynamic properties of a soy-derived biodiesel. Preliminary experimental measurements of two actual biodiesel fuel samples were compared with the results of the model.

To help prioritize our efforts, the Division organized and hosted a workshop July 10–11, 2008 in Boulder entitled "Properties Needs for Biofuels and Blends: Production, Distribution, and End Use." The 44 attendees included representatives from industry, academia, professional groups, and other federal labs. The workshop focused on what property data were needed to assist industry in deploying biofuels across the economy. A wide range of needs were identified, reflecting the broad diversity of the attendees. The fluids of interest ranged from the current ethanol and biodiesel products, to other alcohols, to synthetic gasoline and diesel, and to fuels derived from algae. Blends were very important, since ethanol and biodiesel are almost always mixed with petroleum fuels for retail sale. The most wide-ranging and demanding needs were for properties needed in chemical process design. A consistent theme was that better knowledge of fuel properties would lead to better designs and shorter development times of everything from production facilities to emissions control systems.

Additional Technical Details:

NIST Tech Beat Article:
New NIST Method Accelerates Stability Testing of Soy-Based Biofuel


Associated Publications:

Ott, L.S., Huber, M.L., and Bruno, T.J., "Density and Velocity of Sound Measurements on Five Fatty Acid Methyl Esters at 83 kPa and Temperatures from (278.15 to 338.15) K", J. Chem. Eng. Data, 53, 2412–2416 (2008).

Huber, M. L., Lemmon, E.W., Kazakov, A., Ott, L.S., and Bruno, T. J., "Model for Thermodynamic Properties of a Biodiesel Fuel", work in progress, for submission to Energy&Fuels

Bruno, T. J., Wolk, A., and Naydich, A., "Stabilization of Biodiesel Fuel at Elevated Temperature with Hydrogen Donors: Evaluation with the Advanced Distillation Curve Method", Energy & Fuels 2008, in press.

Bruno, T. J., Wolk, A., and Naydich, A., "Composition-explicit Distillation Curves for Mixtures of Gasoline with Four-carbon Alcohols (Butanols)" Energy & Fuels 2008, in preparation.

Ott, L. S., Smith, B.L., and Bruno, T.J., "Advanced Distillation Curve Measurement: Application to a Bio-derived Crude Oil Prepared from Swine Manure", Fuel 2008, 87, 3379-3387.

Ott, L. S., Smith, B.L., and Bruno, T.J., "Composition-explicit Distillation Curves of Mixtures of Diesel Fuel with Biomass-derived Glycol Ester Oxygenates: A Fuel Design Tool for Decreased Particulate Emissions", Energy and Fuels 2008, 22, 2518-2526.

Ott, L. S., and Bruno, T.J., "Variability of Biodiesel Fuel and Comparison to Petroleum-derived Diesel Fuel: Application of a Composition and Enthalpy Explicit Distillation Curve Method", Energy & Fuels 2008, 22, 2861-2868.

Smith, B. L., Ott, L.S., and Bruno, T.J., "Composition-explicit Distillation Curves of Commercial Biodiesel Fuels: Comparison of Petroleum Derived Fuel with B20 and B100", In. Eng. Chem. Res. 2008, 47, (16), 5832-5840.

Major Accomplishments:

  • Hosted a workshop to consider property needs for biofuels.
  • Performed limited property measurements on five fatty acid methyl esters.
  • Made advanced distillation curve measurements on multiple types of biofuels.
  • A preliminary REFPROP model for soy biodiesel is in development.
Earth and Fuels

End Date:


Lead Organizational Unit:


Source of Extramural Funding:


Thomas J. Bruno
Marcia L. Huber
Andrei Kazakov
Arno Laesecke
Eric W. Lemmon
Mark O. McLinden
Stephanie Outcalt
Richard A. Perkins
Jason Widegren


General Information:
Thomas Bruno
303-497-497-5158 Telephone

Marcia Huber

Mark McLinden

325 Broadway
Mailcode 838.07
Boulder, CO  80305-3328