**3. Soybean oil and soybean biodiesel obtaining and characterization procedures**

The fuel blends used were prepared at the Thermo-sciences Laboratory of Mechanical Engineering Department at Fluminense Federal University (UFF).

It was used Oxx as the nomenclature to designate mixtures of soybean oil with diesel, being xx the percentage by volume of vegetable oil added to diesel. The following mixtures were used: O5; O10; O15 and O20, besides pure diesel (O0).

It was used Bxx as the nomenclature to designate mixtures of biodiesel with diesel, being xx the percentage by volume of biodiesel added to diesel. The following mixtures were used: B5; B10; B15; B20; B50 and B75, besides pure diesel (B0) and pure biodiesel (B100).

Diesel fuel used is from the Laboratory of Distributed Power Generation at Fluminense Federal University. This fuel is used as reference for the tests.

The soybean oil used in the tests was obtained in the food market and the biodiesel used was produced at the Thermo-sciences Laboratory of Mechanical Engineering Department at Fluminense Federal University.

Refined oils are free of substances inhibiting the transesterification process. They have low amount of free fatty acids, less than 0.5%. The beta-carotene and phosphatides of the raw material are eliminated in the process of bleaching and degumming the oil. Thus the processing of these oils for conversion to biodiesel is a process that does not present major technical difficulties. The process is performed at atmospheric pressure.
