ASADES Progress on Renewable Energy and the Environment

Vol. 12, 2008. Printed in Argentina. ISSN 0329-5184

CRUDE OIL TREATMENT FOR COTTON TRANSESTERIFICATION ALKALINE

W. Morales, P. Dagnino, A. Sequeira, A. Diaz, E. Chamorro

Research Group on Biological Organic Chemistry (QUIMOBI)

Regional Faculty Resistance - UTN - French 414 CP 3500 - Resistance

Tel 03722-432928 - Fax 03722-432683 e-mail:. wmorales@frre.utn.edu.ar

SUMMARY: The cotton plantation is characteristic of the northeast of Argentina, being the one of the Chaco largest

producers. After the seed is deslinte a selected part thereof is used for planting and a large ratio discarded. These seeds

contain 19% oil whose characteristics make it very unattractive for use edible. In this paper we study its use as a

feedstock for biodiesel. It was found that it is not feasible to use it directly, as crude oil it is necessary to pre-treat the

oil to remove high rubber content, moisture and reduce acidity. Assays were performed using 15 oil samples varying

conditions for all three processes. It was possible to obtain oil with the necessary features to conduct a alkaline

transesterification.

Keywords: biodiesel, esterification, cottonseed oil, triglycerides.

INTRODUCTION

The great strength that represents the biodiesel fuel is the possibility of being generated from cultures that in our country

are plentiful as cotton, particularly in the NEA region.

Cottonseed oil has very distinct characteristics in terms of their odor and color, reddish brown substance itself colored

present in it. Its quality depends on weather conditions have supported the plant. By This is why oil properties vary in

a single location, from one year to another. Acquiring its worst characteristics in wet seasons or when the seed has been

stored in a humid environment. In these conditions the newly extracted oil can contain up to 5% of free fatty acids

(Bailey, 1984). This oil contains a cidosgrasos high number of congested which brings some difficulties when the

temperatures drop. This oil state Crude is typical for its large number and variety of non-oily substances, up to 2% or

more, including substances mucilaginous, phosphatides and resins (Bailey, 1984) these are the tires that must be

removed for any process to This oil is intended.

Features fresh oil obtained by cold pressing, you can see the need for three treatments, degummed, dried and reduced

content of free fatty acids, all interfering at some stage of the biodiesel.

It is first necessary to remove phosphatides, lecithin and other mucilages which form gums are solubilized or in stable

suspension in oil, it is for making the hydrated insoluble in the oil and separating by precipitation. The non-hydratable

phospholipids are separated by an improved hydration, this is achieved with diluted phosphoric acid solution, the

difficulty with this method is that the oil is saturated with moisture, hampered later stages either esterification or produce

biodiesel. Another method used is the acid precipitation concentrates, which insolubilized gums without hydrate, for

example 85% phosphoric acid. This method appropriate, since oil has no residual moisture, but gums coagulated take a

long time decanting, centrifugation so required and moreover the necessary minimum amount of acid to be used for

achieve effective coagulation of the gums without oil remain acidified. Cotton crude oil it gets dark gum resin,

unmarketable.

Removing water from the oil is required as it interferes with subsequent steps, both of esterification as transesterification

(J. Seed, 2005). The first generation is reversible with water, so it is necessary to prevent presence in the reaction mass

and the second water producing undesirable hydrolyzed oil soaps. Drying carried out by evaporation under vacuum.

The esterification of free fatty acids in the cottonseed oil is performed in order to reduce the content free fatty acid,

which in the subsequent alkaline transesterification generate soaps. The same is done using acid catalysis and methanol

as esterifying agent. This treatment is indispensable when the fatty acid content free, in oil, oleic exceeds 2 g / 100 g

acid sample.

In previous work the possibility of using crude oil was studied, without any treatment, to obtain biodiesel reaching good

results in the laboratory (Sequeira et al., 2007). But the industry is necessary to have a process standardized feedstock

requires constant characteristics. Therefore, since the crude they vary

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It rubber content, moisture and acidity, in the present work the standardization of the quality of oil that was studied

will enter the transesterification reactor. These conditions allow access to automated production processes.

MATERIALS AND METHODS

Characterization of crude cottonseed performed, consisting of the following determinations Analytical: relative density

according IRAM 5504, viscosity using digital viscometer NDJ-8S models Brookfield LDV-E according to IRAM

5506; Refractive index, according to IRAM 5505: 2005 (ISO 6320: 2000); determination of moisture and volatile matter,

according to IRAM 5510: 2005 (ISO 662: 1998); acidity, according to Norma IRAM 5512/1998; gums content

determination by acid precipitation of the gums present in the sample (Lee R., 1969).

Degummed

Degumming was tested by two methods, the method of coagulation with concentrated acid (85% phosphoric acid) and

hydration method using a dilute phosphoric acid solution.

In the first method was proceeded by adding an amount of acid was determined according to the content test gums,

0.1% (wt) phosphoric acid to a concentration of 3.5% gums (Bailey, 1984). The oil was carried 40 and the drip acid was

added, increasing the agitation and temperature to 65-75 C for 30 minutes. This method only removes non-hydratable

gums, phosphatides. Although good results were obtained, these depend on Careful determination of gums, since a small

excess of acid increases the acidity of the oil complicating the subsequent steps.

The second method, which is a modification of the method of hydration, add a solution consisting of 10% of acid

phosphoric. Degumming was performed by heating the oil to 40 C with low agitation and the solution was added in a

proportion 5% of the mass of oil, with good stirring is carried at 70 C for 30 minutes. This method removes both

gums hydratable and non-hydratable, is achieved removing more gums to acid method has the difficulty that the oil is

saturated with moisture.

Drying oil

Two methods were tested, heating the oil to 80 C with stirring in an open container of large area for a period 15

minutes. The other method is a vacuum distillation at 70 C for 15 minutes. The last essay provided best results, lower

residual moisture and oil deterioration.

Esterification

The effectiveness of the esterification reaction was assessed by determining the acidity (as mentioned standard) oil

after sedimentation and decanting. To find the best conditions of the esterification reaction was carried for ward two

designs of experiments.

The first was carried out in a two-necked reactor of 250 ml, 120 g of degummed oil was placed, is He was preheated to

40 C and the proportion of methanol was added to the test and finally the catalyst, sulfuric acid 98%. 10, 12 and 15

were used in molar excess of methanol over the stoichiometrically required mass acids initially present in free fatty

oil. The amounts of catalyst tested were 0.2, 0.5 and 0.8% over the oil mass. With the combination of the three varying

concentrations of methanol and catalyst is obtained a total of Nine trials for each treated oil.

The temperature was kept constant at 70 for one hour with vigorous stirring.

Elapsed time of reaction proceeded to the phase separation. The phase containing the excess methanol, the catalyst and

water formed, depending on the amount of methanol used was found in the bottom or top of blister. This is blackish and

must be separated from the phase slightly lighter color containing oil esterified fatty acids.

RESULTS

Degummed:

The method of degumming by coagulation with concentrated acid worked well in the laboratory, stirring average less

than 1% of the initial mass. But these results depend on careful determination of gums, and a small excess of acid

increases the acidity of the oil complicating subsequent steps; transfer to industry I was hampered.

Given this fact the second method was rehearsal, trying oil with a solution of phosphoric acid was observed higher

removal of gums, was removed from 2 to 4% of the initial mass, as may be observed from figure 1. These have an aspect

totally different acid coagulation method, the gums are whitish, almost liquid very viscous, difficult to separate by

sedimentation, centrifuging the sample is required because the phosphate gums get stuck on the walls of the container.

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Drying

Of the two methods used to remove moisture in oil, the most efficient was made with vacuum that could be observed

in the esterification. It began with oil with average moisture content of 0.33 g / 100 g sample, getting down to 0.10 g /

100 g sample, vacuum was applied to 80 mm Hg.

Esterification:

In the early stages of experimental tests they were conducted esterification without oil degumming, as always the aim

had been to work with crude oil, the reaction showed some drawbacks, this was due to the consumption of catalyst

(sulfuric acid) by the present gums. As a result, the decrease was observed in the content free fatty acids (Table

1). Another analysis extracted from the same table is the difficulty of reaching temperaturas reaction, since the greater

the proportion of lower alcohol is the possibility of raising the reaction temperature.

After degumming step include good results were obtained, it was possible to reduce the acidity of samples oil to desired

values.

Tests carried out with 10 moles of excess alcohol does not reach the desired value of acidity below 2 g of acid oleic /

100 g oil. The results obtained in terms of initial and final acidity in one of the 15 trials oils can seen in Fig. 1, it is noted

that the results in the remaining 14 are similar. While the temperatura reaction is easily achieved when 10 to 12 mole

excess methanol is used, not to use the highest proportion alcohol.

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Design experiments to extract the most effective assays are those obtained with 0.2% and 0.5 mass% 15 moles of catalyst

and excess methanol therefore shown in greater detail in Figure 2, lower acidity for these conditions. It is noted that

with 15 moles excess of methanol decrease acidity is achieved below the value desired in both cases, but more efficient

results are obtained using 0.5% by mass of 98% sulfuric acid.

CONCLUSIONS:

The analysis is extracted that characterize the perfect starting raw material is needed to define the treatments needed to

obtain a good quality biodiesel. You can not avoid degumming step if the rubber content exceeds 3.5%, otherwise no

esterification achieves its objectives and biodiesel production has very low yields. Containing more free fatty acids to

oleic 2g / 100 g oil acid reduction step is necessary for thereof. The best results were obtained when using 0.5% sulfuric

acid and 15 moles of methanol. With the incorporating these steps to the process for obtaining biodiesel excellent results

are achieved in the quality.

REFERENCES

A. Sequeira, Chamorro E., Morales W, and et al. (2007). Experimental study on optimizing conversin cottonseed oil into biodiesel. ASADES 2007

B. Germ JV (2005). Biodiesel processing and production. Fuel Processing Tecnology 86, 1097-1107 Issariyakul T. (2007) Production of biodiesel from waste fryer grease using mixed methanol / ethanol system. Fuel

Processing 88. Technology 429-436

C. Lees, R., (1969). Food Analysis Manual, 1st edition, pp. 188-189. Editorial ACRIBIA. Spain

D. Bailey EA (1984). Industrial oils and greases, 2nd edition, pp. 122-125. Editorial Reverte, SA, Spain

ABSTRACT

Cotton plantation is a characteristic from the North East of Argentina, Being Chaco, one of the major Producers. After

the the seeds separation stand, a selected part of them is used to sow and a huge portion is wasted. These sedes Contain

19% Which Characteristics of oil do not let them to be used for food. In the present work the use of it as row materials

to Obtain bio-diesel. It was found That it can not be used in a direct way, as untreated oil, but it is Necessary pre-treat

the oil to low down the high levels of rubber, the humidity and to reduce the acidity. Tests Were Done with 15 examples

changing the conditions Mentioned of the three processes. It was possible to Obtain oil with the needed Characteristics

Which allow Alkalin transesterification.

Keywords: biodiesel, esterification, cotton seed oil, triglycerides.

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