**2.3 Sunflower oil**

The oil extracted from sunflower seeds is considered to be of high quality for a low percentage of saturated fatty acids and a high percentage of unsaturated fatty acids. It also contains essential fatty acids and a considerable amount of tocopherols that gives it stability. The acidic composition of the sunflower depends on the genotype and the environment. There are currently three groups of genotypes: traditional, oleic medium and oleic high.

#### **2.3.1 Characteristics of plant**

The sunflower belongs at the family "*Asteraceae*, whose scientific name is *Helianthus annuus*. It is an annual plant with a vigorous development in all its organs. Within this species there are many types or subspecies grown as ornamental plants, oilseeds and forage plants" (INFOAGRO, Consulted: http://www.infoagro.com/herbaceos/oleaginosas /girasol.htm ). Average sunflower cycle includes between 100 and 150 days according to genotypes, dates of planting, latitude and availability of water and nutrients. The "temperature is the most important factor in the control of the seeds germination being the optimal near to 26 °C with maximum temperatures of 40 °C and minimum from 3 to 6 °C. The threshold for soil temperature (0 to 5 cm) from which normally starts sowing is between 8 and 10 °C" (Diaz-Zorita et al, Consulted: http://www.asagir.org.ar /Publicaciones/cuadernillo\_web.pdf). The availability of water acts on the soaking of seeds, on the subsequent growth of the seedling. The water excess decreases the amount of air in the soil.

#### **2.3.2 Pests**

28 Biodiesel – Feedstocks and Processing Technologies

The seeds are spherical of 2 to 2.5 mm in diameter and when are mature have a reddish or black brown color. Rapeseed has a proportion (39%) of oil where there are a large number of fatty acids of long-chain, which quantitatively the most important is the erucic acid. The cultivation of rapeseed has ability to grow in temperate climates to temperate cold with good humidity. It adapts to different soil types, the ideals are the franc soils of good fertility

Rape stem weevil (Ceuthorrhynchus napi): the grub of this insect deforms the stem of

 Terminal bud Weevil (Ceuthorrhynchus picitarsis): adults do not cause damage, but the larvae destroy the terminal bud and force the plant to produce side shoots. The

 The siliques weevil (Ceuthorrhynchus assimilis): adults bite the young siliques and the larvae gnaw seeds causing a significant decrease in the harvest. Endosulfan and Fosalón

Cecydomia (Dasyneura brassiceae): The larvae of this insect destroy the siliques totally.

 Meligetos of the cruciferous (*Meligethes sp*): adults are in charge of gnawing the buttons of the rapeseed; these attacks are more important younger are the buttons. When begin

 Flea of rapeseed (Psyllodes chrysocephala): adults appear in autumn rape fields, generally shortly after birth gnawing the leaves and can destroy large number of plants.

Flea of the cabbage (*Phylotreta sp*): adult insects wintering in the soil in September and

The oil extracted from sunflower seeds is considered to be of high quality for a low percentage of saturated fatty acids and a high percentage of unsaturated fatty acids. It also contains essential fatty acids and a considerable amount of tocopherols that gives it stability. The acidic composition of the sunflower depends on the genotype and the environment. There are currently three groups of genotypes: traditional, oleic medium and oleic high.

The sunflower belongs at the family "*Asteraceae*, whose scientific name is *Helianthus annuus*. It is an annual plant with a vigorous development in all its organs. Within this species there

**COMPOSITION %**  Proteins 21,08 Fat 48,55 Fiber 6,42 Ashes 4,54 Nitrogen-free extracts 19,41 TOTAL 100,00

and permeable which is a very sensitive crop to the superficial flooding.

the rape, which is curved and often indenting in a certain length.

Karate to doses of 40-80 cc/hL is recommended for the treatment.

appear in April. Karate works very well against these insects.

treatments are made with endosulfan and Fosalón.

The endosulfan and fosalon control this plague.

the flowering the damage decrease.

Table 3. Rapeseed composition.

are used in treatments.

**2.3 Sunflower oil**

**2.3.1 Characteristics of plant** 

**2.2.2 Pests** 

Pests of early-onset (e.g. cutting caterpillars, leafcutter ants, velvety larvae, worm wire, tenebrionido of the sunflower, underground grille, weevils, black beetle, slugs, etc.) produce damage in seeds and seedlings. Slugs cause great damage to the leaves. The control is convenient with treatments of seeds or specific toxic baits.

#### **3. Biodiesel production process**

The biodiesel production is given by the transesterification reaction which consists of three consecutive and reversible reactions. First, the triglyceride is converted in diacylglycerol, and running at monoglyceride and glycerin. In each reaction one mole of methyl ester is released as shown in Figure 2.

Fig. 2. Stages of the transesterification reaction (Arbeláez & Rivera, 2007. pp 13)

Biodiesel Production from Waste Cooking Oil 31

viscosity not will be pulverized properly by injection systems that have diesel engines. Also increase the opacity of fumes which limits their application in automotive

In the reaction performance is feasible to reach "higher conversions with methanol, ethanol using the process is more complex, expensive, requires a higher consumption of energy and time"(EREN. 2003.pp 38). "We found that it requires less reaction time when using methanol rather than ethanol, either in acid or alkaline catalysis, reaching high yields"(Giron et al.

With the above, the methanol is selected to be used in the biodiesel production due to its

Homogeneous, heterogeneous or enzyme catalysts are used in the biodiesel production. Homogeneous catalysts are soluble in the middle of reaction, i.e. they are in a single phase either liquid or gaseous. "One of the advantages of homogeneous catalysis is the high speed of reaction, and moderate temperature and pressure conditions" (EREN. 2003.pp 4). The catalysts can be acids or alkalis, the acid catalysts are effective but require a time interval extremely long and temperatures exceeding 100 °C for its action. "Getting conversions of 99% with a concentration of 1% sulfuric acid in relation to the amount of oil, it takes about 50 hours" "(EREN. 2003.pp 13). We can use this catalytic process when the oils have a high degree of acidity and "harm the action of alkali catalysts with acidity greater than 10 %"(EREN. 2003.pp 39).We can use sulfuric acid (H2SO4), phosphoric acid (H3PO4), among others. When is used "acid catalysts with alcohol excess is that the recovery of glycerin is more difficult as the quantities of alcohol are quite large compared to other type of catalyst"

"Using HCl are achieved yields of 61% and with H2SO4 we can obtain 80%"(Liu et al. 2006a pp 186), but these "catalysts are more corrosive than alkali catalysts"(Errazu et al. 2005 pp 1305). In comparison with the acidic catalysts, the basic catalysts accelerate the reaction rate, the disadvantage of basic catalysts is that produces soaps due to the high amounts of free fatty acids and water by which we must add the appropriate amount of base to neutralize fatty acids free. The most commonly used are sodium hydroxide (NaOH), potassium hydroxide (KOH) and inappropriate for industrial application (CH3ONa) sodium methoxide since this is more expensive and "requires total absence of water" (EREN. 2003 pp 40). "The catalysts are dissolved in the reaction mixture alcohol-oil what does that not can be recovered at the end of the transesterification reaction" (Arbeláez & Rivera, 2007. pp13). "By using KOH as a catalyst we can produce potassium fertilizers such as potassium chloride, potassium sulphate and potassium nitrate if the product with phosphoric acid is

"The maximum yield found with NaOH is 85% at a sodium hydroxide concentration of 1,0%. Adding an excess in the amount of the catalyst, it gives rise to the formation of an emulsion which increases viscosity and leads to the gel formation" "(Cheng et al. 2008. pp 2210)."With regard to the use of catalyst as (NaOCH3) sodium methoxide and (KOCH3) potassium methoxide we can observe high efficiency compared with other alkali catalysts"(Cheng et al. 2008. pp 2210). The temperature of the transesterification reaction "should not exceed the boiling point of alcohol, because it vaporizes and forms bubbles which limit the reaction in the interfaces alcohol/oil/biodiesel"(Giron et al. 2009.pp 18)

lower cost, better performance and less time and energy during the reaction.

engines"(Benjumea et al. 2007. pp 149).

2009.pp 18).

**3.1.2 Catalysts** 

(Arbeláez & Rivera, 2007. pp13).

neutralized" (Arbeláez & Rivera, 2007. pp14).

Figures 3 and 4 show the secondary reactions that may occur: the saponification reaction and the neutralization reaction of free fatty acids.

Fig. 3. Saponification reaction (Arbeláez & Rivera, 2007. pp 13)

 *Fatty acid Sodium carboxylate* **RCOOH NaOH R COONa H O <sup>2</sup>**

Fig. 4. Neutralization reactions of free fatty acids (Arbeláez & Rivera, 2007. pp 13)

#### **3.1 Raw materials**

The biodiesel production comes mostly from oils extracted oilseed plants especially sunflower, soy, rapeseed and animal fats. However, any material that contains triglycerides can be used for the biodiesel production. "In addition to the oil or fat is needed an alcohol and catalyst to convert oils and fats in alkyl esters". (Arbeláez & Rivera, 2007. pp7)

#### **3.1.1 Alcohol**

"Primary and secondary alcohols with string of 1-8 carbons are used for the biodiesel production, among the alcohols that can be used in this process are: methanol, ethanol" (Cujia & Bula, 2010. pp 106), propanol y butanol. "When are used alcohols such as ethanol is more complicated the recovery of pure alcohol in the process because the azeotrope that forms with water"(Cheng et al. 2008. pp 4) and the performance of ethyl esters is less compared to the methyl esters due methanol has a lower molecular weight (32.04 g/mole) compared to ethanol (46.07 g/mole)."On the other hand if you use methanol, not would contribute to environmental issues and sustainability, biodiesel would not be completely bio, by having a fossil component provided by the alcohol, because methanol is made from natural gas, which is fossil" "(Cheng et al. 2008. pp 4).To use methanol or ethanol is needed "a mechanical agitation to encourage the transfer of mass"(Arbeláez & Rivera, 2007. pp 10)."In the course of the reaction form emulsions, using methanol is easy and quickly dissolved, forming a glycerol-rich bottom layer and a higher layer in methyl esters, while using ethanol these emulsions are more stable making the process of separation and purification of ethyl esters more difficult"(Arbeláez & Rivera, 2007. pp 10).

Is preferred to use methanol in the biodiesel production because of their low viscosity (0.59 m \* Pa \* s at 20 °C), because using alcohols such as ethanol with high viscosity (1,074 m \* Pa \* s at 20 °C), the biodiesel viscosity increases and as a result a "fuel of high viscosity not will be pulverized properly by injection systems that have diesel engines. Also increase the opacity of fumes which limits their application in automotive engines"(Benjumea et al. 2007. pp 149).

In the reaction performance is feasible to reach "higher conversions with methanol, ethanol using the process is more complex, expensive, requires a higher consumption of energy and time"(EREN. 2003.pp 38). "We found that it requires less reaction time when using methanol rather than ethanol, either in acid or alkaline catalysis, reaching high yields"(Giron et al. 2009.pp 18).

With the above, the methanol is selected to be used in the biodiesel production due to its lower cost, better performance and less time and energy during the reaction.

#### **3.1.2 Catalysts**

30 Biodiesel – Feedstocks and Processing Technologies

Figures 3 and 4 show the secondary reactions that may occur: the saponification reaction

*Fatty acid Sodium carboxylate* **RCOOH NaOH R COONa H O <sup>2</sup>**

The biodiesel production comes mostly from oils extracted oilseed plants especially sunflower, soy, rapeseed and animal fats. However, any material that contains triglycerides can be used for the biodiesel production. "In addition to the oil or fat is needed an alcohol and catalyst to convert oils and fats in alkyl esters". (Arbeláez &

"Primary and secondary alcohols with string of 1-8 carbons are used for the biodiesel production, among the alcohols that can be used in this process are: methanol, ethanol" (Cujia & Bula, 2010. pp 106), propanol y butanol. "When are used alcohols such as ethanol is more complicated the recovery of pure alcohol in the process because the azeotrope that forms with water"(Cheng et al. 2008. pp 4) and the performance of ethyl esters is less compared to the methyl esters due methanol has a lower molecular weight (32.04 g/mole) compared to ethanol (46.07 g/mole)."On the other hand if you use methanol, not would contribute to environmental issues and sustainability, biodiesel would not be completely bio, by having a fossil component provided by the alcohol, because methanol is made from natural gas, which is fossil" "(Cheng et al. 2008. pp 4).To use methanol or ethanol is needed "a mechanical agitation to encourage the transfer of mass"(Arbeláez & Rivera, 2007. pp 10)."In the course of the reaction form emulsions, using methanol is easy and quickly dissolved, forming a glycerol-rich bottom layer and a higher layer in methyl esters, while using ethanol these emulsions are more stable making the process of separation and

Is preferred to use methanol in the biodiesel production because of their low viscosity (0.59 m \* Pa \* s at 20 °C), because using alcohols such as ethanol with high viscosity (1,074 m \* Pa \* s at 20 °C), the biodiesel viscosity increases and as a result a "fuel of high

purification of ethyl esters more difficult"(Arbeláez & Rivera, 2007. pp 10).

Fig. 4. Neutralization reactions of free fatty acids (Arbeláez & Rivera, 2007. pp 13)

and the neutralization reaction of free fatty acids.

**3.1 Raw materials** 

Rivera, 2007. pp7)

**3.1.1 Alcohol** 

Fig. 3. Saponification reaction (Arbeláez & Rivera, 2007. pp 13)

Homogeneous, heterogeneous or enzyme catalysts are used in the biodiesel production. Homogeneous catalysts are soluble in the middle of reaction, i.e. they are in a single phase either liquid or gaseous. "One of the advantages of homogeneous catalysis is the high speed of reaction, and moderate temperature and pressure conditions" (EREN. 2003.pp 4). The catalysts can be acids or alkalis, the acid catalysts are effective but require a time interval extremely long and temperatures exceeding 100 °C for its action. "Getting conversions of 99% with a concentration of 1% sulfuric acid in relation to the amount of oil, it takes about 50 hours" "(EREN. 2003.pp 13). We can use this catalytic process when the oils have a high degree of acidity and "harm the action of alkali catalysts with acidity greater than 10 %"(EREN. 2003.pp 39).We can use sulfuric acid (H2SO4), phosphoric acid (H3PO4), among others. When is used "acid catalysts with alcohol excess is that the recovery of glycerin is more difficult as the quantities of alcohol are quite large compared to other type of catalyst" (Arbeláez & Rivera, 2007. pp13).

"Using HCl are achieved yields of 61% and with H2SO4 we can obtain 80%"(Liu et al. 2006a pp 186), but these "catalysts are more corrosive than alkali catalysts"(Errazu et al. 2005 pp 1305). In comparison with the acidic catalysts, the basic catalysts accelerate the reaction rate, the disadvantage of basic catalysts is that produces soaps due to the high amounts of free fatty acids and water by which we must add the appropriate amount of base to neutralize fatty acids free. The most commonly used are sodium hydroxide (NaOH), potassium hydroxide (KOH) and inappropriate for industrial application (CH3ONa) sodium methoxide since this is more expensive and "requires total absence of water" (EREN. 2003 pp 40). "The catalysts are dissolved in the reaction mixture alcohol-oil what does that not can be recovered at the end of the transesterification reaction" (Arbeláez & Rivera, 2007. pp13). "By using KOH as a catalyst we can produce potassium fertilizers such as potassium chloride, potassium sulphate and potassium nitrate if the product with phosphoric acid is neutralized" (Arbeláez & Rivera, 2007. pp14).

"The maximum yield found with NaOH is 85% at a sodium hydroxide concentration of 1,0%. Adding an excess in the amount of the catalyst, it gives rise to the formation of an emulsion which increases viscosity and leads to the gel formation" "(Cheng et al. 2008. pp 2210)."With regard to the use of catalyst as (NaOCH3) sodium methoxide and (KOCH3) potassium methoxide we can observe high efficiency compared with other alkali catalysts"(Cheng et al. 2008. pp 2210). The temperature of the transesterification reaction "should not exceed the boiling point of alcohol, because it vaporizes and forms bubbles which limit the reaction in the interfaces alcohol/oil/biodiesel"(Giron et al. 2009.pp 18)

Biodiesel Production from Waste Cooking Oil 33

Wastes containing these types of oils are products of decomposition that impair the oil quality causing reduction in productivity in the transesterification reaction and may also generate undesirable by-products which hurt the final product. For these reasons, it is important to refine the waste domestic oil for the biodiesel production. "This type of refinement has a right effect on the yield of the reaction from 67% to 87% after bleaching". (EREN. 2003. pp 36). For the treatment of adequacy of waste domestic oil, the operations that can be applied are filtration, de-acidification or neutralization and whitening. The processes of degumming and deodorization aren't needed because the oils have already been treated prior to use and although during degradation odors occur, the removal is not

 *Filtration.* The operation is for removing solids, inorganic material, and other contaminants in the oil. It can be carried out at temperatures higher than 60 °C, where substances carbonaceous produced from burnt organic material, pieces of paper, waste food and other solids are removed or occur at low temperatures which depend on the physical condition of the oil. In addition, we can delete solid fats or products of low

*Desacidification* It is the process by which free oils fatty acids are removed, various

b. Esterification with glycerin: seeks to regenerate the triglyceride.

removal of free fatty acids and the color of the oil is used.

Neutralization with dilute alkali: are used concentrations of 0.75 to 2 N.

temperature between 50 - 60 °C and addition of caustic soda between 70-80 °C.

generators. There are basically two procedures:

d. The distillation of fatty acids, this method requires a high energy cost.

a. Neutralization with alkaline solution: in this process the acids are removed in the

c. Extraction by solvents: where it is used ethanol in proportions 1.3 times the amount

e. Removal of fatty acids with ion-exchange: a resin of strongly basic character for the

Method that provides greater account of productivity in the removal of free fatty acids is the neutralization by caustic soda, since it not only are obtained high relations, but also helps in the bleaching of the oil, because made soaps help dragging the color

Neutralization with concentrated alkali, where the concentration of caustic soda vary

In each of the procedures mentioned above neutralization is carried out hot, with oil at a

Fig. 5. Sample of waste cooking oil **3.1.3.1 Domestic waste oil treatment** 

essential for the biodiesel production.

methods are used:

of oil.

between 2 and 5 N.

form of soaps.

melting points from the frying process.

"To be used as catalyst NaOH with methanol, has been found that the optimum temperature to achieve high yields was 60 °C, while using KOH to this same temperature not achieved such high yields and higher catalyst concentrations should be used to using NaOH" (Liu et al. 2006b pp 110). "In an alkali catalyzed process is reached high purity and yields in short periods of time ranging between 30 - 60 minutes" (Liu et al. 2006a pp 186).

Heterogeneous catalysts are found in two phases and a contact area, "the use of these catalysts simplifies and makes more economical the purification process due the easy separation of the products and reactants. The disadvantage is the difficulty to temperature control for very exothermic reactions, limitations on mass transfer of reactants and products, as well as high mechanical resistance to the catalyst" (Arbeláez & Rivera, 2007. pp12). Among the most common catalysts are the metal oxides (MgO, CaO), acids of Lewis (SnCl2), etc. For example, by using zinc oxide are obtained yields of 50.7%, when using Al2O3 is obtained 57.5% and using CaO yield of 65%"(Rojas & Torres. 2009 pp 15). "These catalysts have limitations on transfer of mass of reactants and products" (Arbeláez & Rivera, 2007. pp12), but they have the advantage that they are not corrosive to the reactor"(Guan et al. 2009 pp 520).The easy separation of the products generates a "simplification of the manufacturing process since the catalyst can be separate from the products of reaction with a simple filtration process"(Lles et al. 2008 pp 63). "Don't generate byproduct of soap by reaction with free fatty acids (AGL)". (Bournay et al. 2005. pp 191) "Using CaO is achieved a yield of 65% and by using MgO a yield of 64%"(Bournay et al. 2005. pp 192). To achieve high yields the reaction must be carried out "to a higher temperature increasing energy costs" (Bournay et al. 2005. pp 191).Reported high reaction times, because the "speed of transesterification reaction with these catalysts is lower in comparison with homogeneous catalysts, due to the mass transfer resistance" (Guan et al. 2009 pp 522).

Finally, the lipases being effective for the transesterification reaction can be used between the enzyme catalysts. "This type of catalysis has the advantage of allowing the use of alcohol with high content of water (more than 3%), low temperatures, which is an energy-saving and high degrees of acidity in oils" (EREN. 2003. pp 41).

### **3.1.3 Waste cooking oil**

The waste cooking oil is generated from the fried food, which need large amounts of oil because it requires the full immersion of food at temperatures greater than 180 °C. Accordingly to the high temperatures are generated changes in its chemical and physical composition, as well as in its organoleptic properties which affect both the food and oil quality.

Reuse of domestic oil has a high risk to the health of consumers as depending on the type of food subjected to frying, "this absorbs between 5% and 20% of the used oil, which can increase significantly the amount of hazardous compounds that provide degraded oil to food" (EREN. 2003. pp 31)."In an alkali catalyzed process is reached high purity and high yields in short periods of time ranging between 30 - 60 minutes"(Liu et al. 2006 pp 186).

Used cooking oil is normally black, a strong odor and does not have large amount of solids because its collection is passed through a fine mesh. In Figure 5, we can see a sample of used oil from the hotel sector.

"To be used as catalyst NaOH with methanol, has been found that the optimum temperature to achieve high yields was 60 °C, while using KOH to this same temperature not achieved such high yields and higher catalyst concentrations should be used to using NaOH" (Liu et al. 2006b pp 110). "In an alkali catalyzed process is reached high purity and yields in short periods of time ranging between 30 - 60 minutes" (Liu et al. 2006a pp

Heterogeneous catalysts are found in two phases and a contact area, "the use of these catalysts simplifies and makes more economical the purification process due the easy separation of the products and reactants. The disadvantage is the difficulty to temperature control for very exothermic reactions, limitations on mass transfer of reactants and products, as well as high mechanical resistance to the catalyst" (Arbeláez & Rivera, 2007. pp12). Among the most common catalysts are the metal oxides (MgO, CaO), acids of Lewis (SnCl2), etc. For example, by using zinc oxide are obtained yields of 50.7%, when using Al2O3 is obtained 57.5% and using CaO yield of 65%"(Rojas & Torres. 2009 pp 15). "These catalysts have limitations on transfer of mass of reactants and products" (Arbeláez & Rivera, 2007. pp12), but they have the advantage that they are not corrosive to the reactor"(Guan et al. 2009 pp 520).The easy separation of the products generates a "simplification of the manufacturing process since the catalyst can be separate from the products of reaction with a simple filtration process"(Lles et al. 2008 pp 63). "Don't generate byproduct of soap by reaction with free fatty acids (AGL)". (Bournay et al. 2005. pp 191) "Using CaO is achieved a yield of 65% and by using MgO a yield of 64%"(Bournay et al. 2005. pp 192). To achieve high yields the reaction must be carried out "to a higher temperature increasing energy costs" (Bournay et al. 2005. pp 191).Reported high reaction times, because the "speed of transesterification reaction with these catalysts is lower in comparison with homogeneous catalysts, due to the mass transfer resistance"

Finally, the lipases being effective for the transesterification reaction can be used between the enzyme catalysts. "This type of catalysis has the advantage of allowing the use of alcohol with high content of water (more than 3%), low temperatures, which is an energy-saving

The waste cooking oil is generated from the fried food, which need large amounts of oil because it requires the full immersion of food at temperatures greater than 180 °C. Accordingly to the high temperatures are generated changes in its chemical and physical composition, as well as in its organoleptic properties which affect both the food and oil

Reuse of domestic oil has a high risk to the health of consumers as depending on the type of food subjected to frying, "this absorbs between 5% and 20% of the used oil, which can increase significantly the amount of hazardous compounds that provide degraded oil to food" (EREN. 2003. pp 31)."In an alkali catalyzed process is reached high purity and high yields in short periods of time ranging between 30 - 60 minutes"(Liu et al. 2006 pp

Used cooking oil is normally black, a strong odor and does not have large amount of solids because its collection is passed through a fine mesh. In Figure 5, we can see a sample of used

186).

(Guan et al. 2009 pp 522).

**3.1.3 Waste cooking oil** 

oil from the hotel sector.

quality.

186).

and high degrees of acidity in oils" (EREN. 2003. pp 41).

#### Fig. 5. Sample of waste cooking oil

#### **3.1.3.1 Domestic waste oil treatment**

Wastes containing these types of oils are products of decomposition that impair the oil quality causing reduction in productivity in the transesterification reaction and may also generate undesirable by-products which hurt the final product. For these reasons, it is important to refine the waste domestic oil for the biodiesel production. "This type of refinement has a right effect on the yield of the reaction from 67% to 87% after bleaching". (EREN. 2003. pp 36). For the treatment of adequacy of waste domestic oil, the operations that can be applied are filtration, de-acidification or neutralization and whitening. The processes of degumming and deodorization aren't needed because the oils have already been treated prior to use and although during degradation odors occur, the removal is not essential for the biodiesel production.

	- a. Neutralization with alkaline solution: in this process the acids are removed in the form of soaps.
	- b. Esterification with glycerin: seeks to regenerate the triglyceride.
	- c. Extraction by solvents: where it is used ethanol in proportions 1.3 times the amount of oil.
	- d. The distillation of fatty acids, this method requires a high energy cost.
	- e. Removal of fatty acids with ion-exchange: a resin of strongly basic character for the removal of free fatty acids and the color of the oil is used.

Method that provides greater account of productivity in the removal of free fatty acids is the neutralization by caustic soda, since it not only are obtained high relations, but also helps in the bleaching of the oil, because made soaps help dragging the color generators. There are basically two procedures:


In each of the procedures mentioned above neutralization is carried out hot, with oil at a temperature between 50 - 60 °C and addition of caustic soda between 70-80 °C.

Biodiesel Production from Waste Cooking Oil 35

To select the best alternative for the biodiesel production are defined three ranges for the

Catalyst concentration (% w/w) 0.2% - 1% >1% - 3% >3% - 15% Molar ratio alcohol/oil 3:1 - 6:1 >6:1 - 12:1 >12:1 - 80:1 Temperature (°C) 50 - 60 >60 - 100 >100 – 200 Yield (%) 20 – 70 >70 - 90 > 90 – 100

Reaction time (hours) 0.16 – 1 >1 - 2 > 2 – 40

Table 6. Ranges established for the operation conditions of the transesterification reaction

It is a key to make a design from which the most appropriate values for each of the design factors can be established. The selected factors were: molar ratio alcohol/oil, percentage of catalyst, temperature and washing agent, where the first three are design variables and the latter is a design condition. Before starting the design is important defines the ranges and levels for these factors, for this reason, we search the experimental phase in scientific articles

> **DESIGN FACTORS RANGE**  Molar ratio alcohol/oil 6:1- 15:1 Catalyst Percentage (% wt.) 0,4-1 Temperature (°C) 40-70

> > Washing agent Water (40°C) - Acetic acid

Based on the ranges set out in table 7, we provide that the factorial design appropriate for the process is the factorial design 2k, which can be solved by the technique of Yate contrasts which establish two levels for each of the design factors, these levels are high (+) and low (-)

**Design Factor High level (+) Low level (-)** 

For the molar ratio alcohol/oil is found a ratio of 6: 1 that is optimum for achieving high conversions, some articles display that lower ratio not is possible to reach a complete transesterification reaction. There are also good results with ratios ranging between 9:1 and 12:1, while if we use higher than 15:1 molar ratio there are difficulties in the separation of

Molar ratio alcohol/oil 9:1 6:1 Catalyst Percentage(% wt) 0.7 0.5 Temperature(°C) 60 50 Washing agent Acetic acid Water (40°C)

**RANGES Low Middle High** 

operation conditions to be used in the transesterification reaction (table 6).

**SELECTION PARAMETERS** 

(Rojas & Torres. 2009. pp 18).

related to the project (table 7).

Table 7. Ranges for the design factors

Table 8. Levels for each design factor

glycerin and methyl esters.

(see table 8)

**4.1 Experimental design**
