**2. Theoretical foundations**

All vegetable oils consist primarily of triglycerides. The triglycerides have a three-carbon backbone with a long hydrocarbon chain attached to each of the carbons. These chains are attached through an oxygen atom and a carbonyl carbon, which is a carbon atom that is double-bonded to second oxygen. The differences between oils from different sources relate to the length of the fatty acid chains attached to the backbone and the number of carbon– carbon double bonds on the chain. Most fatty acid chains from plant based oils are 18 carbons long with between zero and three double bonds. Fatty acid chains without double bonds are said to be saturated and those with double bonds are unsaturated (Misra & Murthy, 2010).

In general, vegetable oils are made especially of fatty acids with chains between 12 and 24 carbons: Lauric (C12:0); Myristic (C14:0); Palmitic (C16:0); Palmitoleic (C16:1); Stearic (C18:0); Oleic (C18:1); Linoleic (C18:2); Linolenic (C18:3); Arachidic (C20:0); Gadoleic (C20:1); Behenic (C22:0); Erucic (C22:1); Lignoceric (C24:0). The proportions of the fatty acid composition can be determined by gas chromatography method.

Triglycerides are hydrocarbons with physical and chemical characteristics that can be classified as liquid fuels in the majority.

Vegetable oils have a high heating value, near the heating value of conventional diesel fuel, which makes them an important energy resource.

To improve the properties of vegetable oils and in order to use them as substitutes for diesel fuel, triglycerides are converted into esters (biodiesel) by transesterification process, modifying the composition of molecules and changing the characteristics of the fluids. The composition of the resulting esters has approximately the same proportion of fatty acids present in oils before the transformation process.

The regulations for biodiesel have been developed in different countries where its use is permitted. In the U.S. the standard for biodiesel is set by the technical standard ASTM D 6751, the European Union is related with the standard EN 14214 and in Brazil is set in the

Biodiesel can be produced from different oilseeds, according to the design of the plant, market conditions and availability of raw material in the region. Each oilseed production has a different culture method and a different destination. The disposal of oils for biodiesel production must take into account beyond the capacity of oil production, market competitiveness in relation to the cost of oil and the price of a barrel of fuel. Biodiesel can be

Just as vegetable oil, the use of biodiesel as fuel in partial or total replacement to diesel has many advantages that have been highlighted in the literature (Demirbas, 2009b; Pereira et

Environmental advantages of biodiesel are: greenhouse gas reductions; biodegradability; higher combustion efficiency; improved land and water use; carbon sequestration; lower

Energetic advantages of biodiesel are: supply reliability; higher flash point; reducing use of

Social-economic advantages of biodiesel are: sustainability; fuel diversity; increased number of rural manufacturing jobs; increased income taxes; increased investments in plant and equipment; agricultural development; international competitiveness; reducing the

All vegetable oils consist primarily of triglycerides. The triglycerides have a three-carbon backbone with a long hydrocarbon chain attached to each of the carbons. These chains are attached through an oxygen atom and a carbonyl carbon, which is a carbon atom that is double-bonded to second oxygen. The differences between oils from different sources relate to the length of the fatty acid chains attached to the backbone and the number of carbon– carbon double bonds on the chain. Most fatty acid chains from plant based oils are 18 carbons long with between zero and three double bonds. Fatty acid chains without double bonds are said to be saturated and those with double bonds are unsaturated (Misra &

In general, vegetable oils are made especially of fatty acids with chains between 12 and 24 carbons: Lauric (C12:0); Myristic (C14:0); Palmitic (C16:0); Palmitoleic (C16:1); Stearic (C18:0); Oleic (C18:1); Linoleic (C18:2); Linolenic (C18:3); Arachidic (C20:0); Gadoleic (C20:1); Behenic (C22:0); Erucic (C22:1); Lignoceric (C24:0). The proportions of the fatty acid

Triglycerides are hydrocarbons with physical and chemical characteristics that can be

Vegetable oils have a high heating value, near the heating value of conventional diesel fuel,

To improve the properties of vegetable oils and in order to use them as substitutes for diesel fuel, triglycerides are converted into esters (biodiesel) by transesterification process, modifying the composition of molecules and changing the characteristics of the fluids. The composition of the resulting esters has approximately the same proportion of fatty acids

composition can be determined by gas chromatography method.

ANP (National Petroleum Agency) No. 07 from 19.03.2008.

obtained, too, from used cooking oil, animal fats and algae.

sulfur content; lower aromatic content; less toxicity.

fossil fuels; ready availability; renewability.

dependency on imported petroleum.

classified as liquid fuels in the majority.

which makes them an important energy resource.

present in oils before the transformation process.

**2. Theoretical foundations** 

Murthy, 2010).

al., 2007).

Biodiesel is known as monoalkyl, such as methyl and ethyl, esters of fatty acids. Biodiesel can be produced from a number of sources, including recycled waste vegetable oil, oil crops and algae oil. Biodiesels play an important role in meeting future fuel requirements in view of their nature (less toxic), and have an edge over conventional diesel as they are obtained from renewable sources (Demirbas, 2009b).

The transesterification process is used to transform triglycerides into esters, or biodiesel. In the process of transesterification, the triglycerides found in different kinds of oils and fats react with alcohol, usually methanol or ethanol to produce esters and glycerin. For the reaction to occur it is necessary to use a catalyst. Processes performed the supercritical conditions of methanol transesterification can be conducted without the catalyst. (Demirbas, 2003; Saka & Kusdiana, 2001)

In the transesterification process, a triglyceride molecule reacts with an alcohol molecule causing the separation of one of the fatty acids of the triglyceride, producing a diglyceride and an ester. This diglyceride reacts with a second molecule of alcohol that takes another fatty acid, forming a second ester and a monoglyceride. Finally a third molecule of alcohol reacts with the monoglyceride, forming the third ester and a molecule of glycerin. The reactions occurring are reversible, and the stoichiometric ratio is three moles of alcohol for each mole of oil being processed. The reaction can be carried out with concentrations of alcohol in excess, as this reduces time and increases the conversion efficiency of the process. (Lang et al., 2001)

The transesterification process using methanol and base catalyst is the most commonly used to produce biodiesel. The catalysts commonly used are sodium hydroxide (NaOH) or potassium hydroxide (KOH). The catalyst is diluted in alcohol and then added the oil. The product is the ester (biodiesel) and crude glycerin. The glycerin is separated from the ester by decanting or centrifuging.

Repeated washing processes are performed by adding acidified water in the reaction products. This mixture is stirred lightly and serves to remove residual glycerine soap, catalyst and serves as a neutralizing agent of the fuel. The washing process is repeated until the biodiesel becomes clear. The main drawbacks of the process are the presence of water on some of the reagents and the high level of free fatty acids in the raw material. In both cases, the transesterification reaction is replaced by a saponification reaction.

The transesterification process can also be developed using acid catalysts and no homogeneous catalysts. In the case of acid catalysts, the process times are longer, but do not have drawbacks with the water content and free fatty acids. In the case of no homogeneous catalysts, these bring benefits in: reducing the washing process; product separation and reuse of catalysts.

Methanol and ethanol are produced on an industrial scale and their use in transesterification reactions has been reported.

The biodiesel used in several countries of Europe and in the United States is a mixture of methyl esters. Methanol is usually obtained from non-renewable fossil fuels, but can also be obtained by distillation of wood; this route, however, produces smaller quantities. The technology of biodiesel production using methanol is fully understood, however, this route has the disadvantage that methanol is extremely toxic.

The transesterification using ethanol is more difficult because the use of alcohol, even if anhydrous, involves problems in the separation of glycerin from the reaction medium. However, the use of ethanol is advantageous, since it is produced on a large scale in

Use of Soybean Oil in Energy Generation 307

7. After checking the reaction, put the fluid in the decanting funnel, allow the glycerin settle for a period exceeding 30 minutes. Separate the glycerin and ester (biodiesel)

8. Wash the decanting funnel to remove the glycerin stuck on the walls and then fill with

9. Perform the washing process of ester, adding 30 mL of water, preferably hot (50-60°C),

11. Perform the washing process three more times to ensure complete removal of the

12. Perform the drying process putting the ester in an oven, heating up to 110 º C for 10

**3.2 Characterization of soybean oil and soybean biodiesel and stationary engine tests**  The properties of soybean oil, soybean biodiesel and diesel were determined at the Thermosciences Laboratory and Rheology Laboratory of Fluminense Federal University. The heating values were determined at the Laboratory of fuels at the National University of

The tests conducted in the stationary engine were made at constant speed of 3600 rpm and

For each fuel tested, a test was performed and repeated. Performance data and emissions were measured continuously during the test and the series of data were analyzed to obtain

Viscosity ASTM D 445 Standard Test Method for Kinematic

Density ASTM D 4052 Density and Relative Density of Liquids

Flash point ASTM D 93 Standard Test Methods for Flash Point by

Pour point ASTM D97 Test Method for Pour Point of Petroleum

Cloud point ASTM D2500 Test Method for Cloud Point of

Copper strip corrosion ASTM D130 Test Method for Copper strip corrosion of

Heat of combustion ASTM 240 Test Method for heat of combustion of

The stationary engine used (Figure 1) is formed by an engine, a generator and a control panel, with the possibility of producing electricity at 115V and 230V. The generator has a control system to regulate the motor rotation. The characteristics of the diesel engine are: 3600rpm; four-stroke; direct injection; one cylinder; air cooling system; 0.211L displacement

Table 1. Technical standards associated with the characterization tests

Viscosity of Transparent and Opaque Liquids

by Digital Density Meter.

Pensky-Martens Closed Cup Tester

Petroleum Products

Products

Petroleum Products

Petroleum Products.

Colombia. The characterization tests followed the standards, as detailed in Table 1.

PROPERTY STANDARD

inside the funnel, stirring to ensure the contact of two fluids;

10. Decant the water and remove it from the funnel;

variable power in the Fluminense Federal University

values representative of engine performance

13. Cool and bottle the product (biodiesel)

produced in clean containers;

the ester obtained;

glycerin;

minutes

countries like Brazil and the United States, being from a renewable source of energy, resulting in environmental gains could generate carbon credits. As for the difficulties in the separation of phases in reactions employing ethanol in biodiesel synthesis, they can be bypassed by adjustments in reaction conditions.
