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___________________________________* Corresponding author. Email: miguel2@eq.uc.pt

Biodiesel alternative fuel

Pedroso1*

, L.M., Ferreira1, J. L., Falco

2, J., Simes

1, P.N., Simo

2, A.V., Portugal

1, A.

1Grupo de Computao, Estatstica e Materiais (CEM),

Departamento de Engenharia Qumica

Universidade de Coimbra, Plo II, Pinhal de Marrocos, 3030-290 Coimbra, Portugal2Cmara Municipal de Coimbra, Praa 8 de Maio, 3000-300 Coimbra, Portugal

Keywords: Biodiesel, Fuel, Pilot Plant, Vegetable Oil Recycling

Topic: Chemical Engineering and Quality of Life Sustainable and Clean Technologies

Abstract

Biodiesel is a methyl-ester produced from vegetable or animal oil, of diesel quality, which can be used

as biofuel. In this work we introduce a project for the design and construction of a biodiesel

production plant, at pilot scale. The synthesis of biodiesel is then studied at different temperatures. Forthe determination of the percentage of biodiesel and soybean oil in a mixture, two mathematical

models based on FTIR analysis were developed and evaluated. We used partial least squares

regression to build the models from the absorbance in predetermined spectral ranges of the calibration

mixtures. This technique proved to be effective and simpler than other conventional methods. The

syntheses of biodiesel were monitored by this method. It was found that after 10 minutes of reaction

the oil percentage in the samples was less than 5% and biodiesel percentage higher than 95%. These

results were attributed to the fast reaction of the oil and to the discarding of mono and di-glycerides in

the washing step. SEC chromatography and viscosity tests confirmed the results. The acid value of the

synthesized biodiesel was also measured, resulting in a low value. Finally, a test of the use of biodiesel

(B20) in vehicles is presented. Although some problems found in the rubber seals of one of the

vehicles, due to its age, the other two vehicles had no problems and engine wear was not apparent. A

decrease in fuel consumption was observed, which resulted in economical benefits from the use ofbiodiesel.

1 Introduction

A biofuel is a liquid or gaseous fuel for transport produced from biomass. Biodiesel is a methyl-ester

produced from vegetable or animal oil, of diesel quality, to be used as biofuel (Directive 2003/30/EC

2003). The European Directive 2003/30/EC promotes a proportion of 2% of biofuels in petrol and

diesel for transports placed in market by December 2005. The reference value for December 2010 is

5.75%. These milestones allow the Member States to keep sustainable farming and forestry practices,

and lead to new market-oriented opportunities to agriculture. Of utmost importance to the EU

countries is to reduce the dependence on oil and comply with Kyoto Protocol. In March 2005 Portugal

still had not reported to European Union the target values of biofuels placed in the market for 2005

(Pblico 2003).

Biodiesel can be produced by different processes. The most common use vegetable oil that is

converted to biodiesel by a transesterification reaction. Vegetable oil reacts with methanol in the

presence of a basic catalyst (eg. NaOH), an acid catalyst (eg. sulfuric acid) or enzymes (Zhang, Dub,

McLean and Kates 2003). Acid and basic catalysts can also be used in the same process. The reaction

products are biodiesel, glycerine and a residue that can be used as fertilizer. The yield of the processes

ranges from 94.1 to 97% with basic catalysts and 97.8 to 98.4% with acid catalysts (Kusdiana and

Saka 2004). The produced biodiesel should meet the EN14214 norm of the European Committee for

Standardization (CEN). Germany has also used the DIN 51606 norm.

Biodiesel is used in diesel engines or heaters. Normally it is blended with diesel due to some different

properties between the two fuels. Mixtures up to 5% of biodiesel can be used without any modificationof the engine. When compared to diesel, biodiesel reduces the emissions of total unburned

hydrocarbons, carbon monoxide and particulate matter, and sulfur emissions are essentially eliminated

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(National Biodiesel Board 2005).

In this work we introduce a project from the University of Coimbra, PRODEQ and Cmara Municipal

de Coimbra (CMC) to design and implement a biodiesel pilot plant. The production of biodiesel is

then studied at a laboratory scale, where FTIR, GC and viscosity tests are used to evaluate the reaction

extent in time. Two mathematical models based on FTIR are developed and evaluated. A study of the

use of biodiesel in CMC vehicles is finally presented.

2 Project for the design and implementation of a pilot plant

A consortium between the University of Coimbra, PRODEQ and CMC Department of Ambient and

Quality of Life (DAQV) was established to create a biodiesel production facility at pilot plant scale.

The project aims at the design, construction and demonstration of the plant. The unit will be designed

to produce 1000 litres of biodiesel per batch. Waste vegetable oil, from University of Coimbra

(SASUC), recycling stations and other producers will be collected and used to produce biodiesel. The

study of the availability of waste vegetable oils in Coimbra is also of importance. The synthesis of

biodiesel at laboratory scale will be studied in more detail to obtain the necessary data for plant design.

This comprises all the parts of the process, being the transesterification reactor the main unit. Theentire process will be controlled by computer, both to simplify the operation of the pilot plant and to

ensure consistent results. After the construction of the plant, an optimization study will be made to

define the optimum operation points and tune the control system to different types of oil. The

produced biodiesel will be tested in water heaters and vehicles. These tests will show in detail the

differences between biodiesel or diesel systems. In the final part of the project, the pilot plant will be

presented to AREAC (Regional Agency of Energy and Ambient of the Centre) to show the advantages

of recycling the oil and of the use of the biofuel. The advantages of biodiesel will be also

demonstrated in schools of the district of Coimbra.

3 Study of the synthesis of biodiesel

3.1 Materials and equipment

Reagents: refined soybean oil containing 0.102% of free fatty acids (w/w), methanol (pure, Pronalab)

and sodium hydroxide (>98%, Fluka).

FTIR spectra were collected in a Nicolet Magna IR 750 equipment, using a Golden Gate ATR

accessory from Specac, where the samples were analysed as prepared. The resolution was 1 cm-1

and

the number of scans 32. Viscosity was measured in a Brookfield DVII+ equipment, using a small

sample adapter.

3.2 Syntheses

The syntheses of biodiesel were carried out in a 250 ml glass reactor equipped with a magnetic stirrer

and reflux condenser. A temperature controlled oil heating bath, with a Omron E5CK PID digitalcontroller with parameters adjusted to the oil bath system, was used to control the reaction

temperature.

A molar ratio of methanol to oil of 6:1 was used, with 1% of NaOH catalyst in relation to the oil.

Reactions were carried out at 55 and 65C, during 120 min. Aliquots of the reaction mixtures were

collected at various times of the reaction. These were centrifuged to separate the glycerol, and washed

several times with water. Finally, the samples were then centrifuged to separate the water and were

dried.

3.3 Calibration of FTIR

The FTIR spectra of oil and biodiesel, shown in Fig. 1, are as expected very similar since the two

compounds have almost the same chemical groups. However, some differences are detectable. Theposition of the carbonyl band in FTIR is sensitive to substituent effects and to the structure of the

molecule (Pasto et al. 1992). The methoxycarbonyl group in biodiesel shows a different band position

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concentration of biodiesel and oil in the samples. Fig. 2 a) shows the obtained results. The sample

taken at 10 minutes of reaction shows a percentage of oil of 1% (model 1) or 5% (model 2). To

confirm these results SEC chromatography was used. The approximate oil content found was 6%. This

indicates that model 2 is more accurate in this concentration range than model 1. The samples with

higher reaction times showed lower oil content.

The FTIR models are based on the concentration of the chemical groups in oil and in biodiesel.

However, mono and di-glycerides should also be observed by FTIR. The low concentration of oil

found in the first sample (10 min) does not confirm this, and suggests that the models do not take

mono and di-glycerides into account. However, it should be noted that the washing of the samples may

have separated the mono and di-glycerides, leading to a product with only oil and biodiesel. This is

confirmed by the fact that mono and di-glycerides form an emulsion with water.

Time/ min

0 20 40 60 80 100 120

%

0

20

40

60

80

100

Oil - model 1

Oil - model 2Biodiesel - model 1

Biodiesel - model 2

a) Time/ min0 20 40 60 80 100 120

Viscosity/

cP

4

5

6

30

35

40

45

55C

65C

b)

Fig. 2: a) Percentages of oil and biodiesel during the reaction at 55C, in the washed samples, using the

FTIR models 1 and 2; b) viscosity of the washed samples during the reactions. The points shown for

the initial time are from the soybean oil.

Fig. 2 b) shows the viscosity of the samples for the reactions carried out at 55 and 65C. The

viscosities of the samples taken at 10 minutes of reaction were already similar to the viscosity of the

product at the end of the reaction, of around 4.5 cP. The low oil content and the separation of

intermediate products in the washing step is again the probable cause of these results. These show that

the initial stage of reaction, where tri-glycerides are converted into di-glycerides, is fast. The viscosity

of a commercial biodiesel was also measured, with values of 5.08 and 4.06 mPa s at 30 and 40C,

respectively. The norm EN 14214 defines the biodiesel viscosity between 3.5 and 5.0 mm2/s at 40C.

The obtained values were all between these two limits. To convert the dynamic into kinematic

viscosity we used a mean value of 0.88 g cm-3

for the density of biodiesel, taken from the norm EN

ISO 3675.

The acid value was measured by potentiometric titration. Samples of the biodiesel synthesized at 55and 65C showed an acid number lower than 0.07 mg KOH/g biodiesel. A commercial biodiesel was

also tested, with a result of 0.46 mg KOH/g biodiesel. The maximum acid value in norm prEN 14104

for biodiesel is 0.5 mg KOH/g biodiesel.

4 Results from tests in vehicles

For a period of four months three vehicles from DAQV were tested with biodiesel, with a mixture B20

(20% biodiesel and 80% diesel). The vehicles were a Peugeot Partner and two trucks a Volvo FL7

and a Mercedes 1922. Globally, no anomalies or any other signs of different behaviour were detected.

However, the Volvo FL7 have shown problems in the rubber seals and tubes in the systems in contact

with the B20 mixture. This was attributed to the age of the vehicle, built in 1988. Table 2 shows theconsumptions and economical analysis.

The oil of the Mercedes 1922 engine was tested before and after the use of biodiesel. Several chemical

and physical tests were performed, as well as concentration of metals that indicate wearing of the

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engine or the presence of contaminants. The tests before and after the use of biodiesel gave similar

results. This showed that this engine was not affected by the use of the B20 mixture.

Table 2: Comparison of the consumption and economical analysis of the use of B20

Consumption (l/km)

Vehicle

Number of

km in the

testDiesel B20

Variation

(%)

Savings of the

use of B20 ()(1)

Peugeot Partner 3820 0.0785 0.0699 -11.0 27.82

Mercedes 1922 11758 0.6176 0.5986 -3.1 227.31

Volvo FL7 8949 0.6269 0.6110 -2.5 151.97

(1)Based on mean diesel price during the period of test of 0.7875 , and price of biodiesel of 0.751 , prices

per litre.

5 Conclusions

This work presents a method for the determination of the quantities of oil and biodiesel in a mixture.

The method was based on FTIR and provides these measurements with a convenient technique. It was

applied to monitor the reaction of synthesis of biodiesel. It was found that after 10 minutes of reaction

oil percentage in the samples was less than 5% and biodiesel percentage was higher than 95%. This

shows that the initial stage of the reaction is fast. However, the mono and di-glycerides were separated

during the washing step and thus were not detected by FTIR. The viscosities and acid number of the

synthesized biodiesel were also measured, and low values were obtained. The test of B20 in vehicles

showed some problems in the older truck, but the mixture can be used with advantage in newer

vehicles.

ReferencesNational Biodiesel Board (2005), http://www.biodiesel.org, March 2005.

Directive 2003/30/EC of the European Parliament and of the Council of 8 May 2003, Office Journal

of the European Union, 17 May 2003, L123/42L123/46.

Kusdiana, D. and Saka, S. (2004), Effects of water on biodiesel fuel production by supercritical

methanol treatment, Bioresource Technology, 91, 289295.

Pasto, D., Johnson, C. and Miller, M. (1992). Experiments and Techniques in Organic Chemistry.

Prentice Hall, New Jersey.

Pblico (2003),Bruxelas notifica Estados membros por atrasos na legislao sobre biocombustveis,

Jornal Pblico, 16 de Maro.

Quercus (2003), in http://gaia.org.pt/pipermail/gaia-geral/2003-January/msg00047.html, May 2004.

Roeges, N. P. G. (1994).A guide to complete interpretation of infrared spectra of organic structures.

John Wiley & Sons, Chicester.Zhang, Y., Dub, M.A., McLean, D.D. and Kates, M. (2003), Biodiesel production from waste

cooking oil: 1. Process design and technological assessment, Bioresource Technology, 89, 116.