**3.1 Oil characterization**

Oil characterization before proceeding with the standardization of the raw material is a very important issue. Some properties remain in fact unchanged from the starting material to the finished biodiesel, or they are anyway predetermined. It is so important to check that the values of such chemical and physical oil properties are in range with those required by the standard regulations (see Table 3). The experimental procedures to get the values of such properties are also standardized and are indicated in the regulations. The following are parameters for starting oil that can affect the quality of the final biodiesel.

#### **Sulfur and phosphorous content:**

High sulphur and phosphorous content in the fuels cause greater engine wear and in particular shorten the life of the catalyst. Biodiesel derived from soybean, rapeseed, sunflower and tobacco oils are known to contain virtually no sulphur (Radich, 2004; Zhiyuan et al., 2008).

The authors have nevertheless found that the oil obtained from *B.juncea* seeds may contain high concentrations of sulphur due to the presence in the plant's tissues of glucosinolates, the molecules responsible for the biofumigation effect.

#### **Linoleic acid methyl ester, iodine value and viscosity**

Soybean, sunflower, peanut and rapeseed oils contain a high proportion of linoleic fatty acids, so affecting the properties of the derived ester with a low melting point and cetane number. Quantitative determination of linoleic acid methyl ester is accomplished by gas chromatography with the use of an internal standard after the substrate has been transesterificated and allows also the quantification of the other acid methyl esters (Environment Australia, 2003). The super-critical chromatography is another useful analytical technique, suitable for the direct analysis of the oils.

Non Edible Oils: Raw Materials for Sustainable Biodiesel 11

*Brassica juncea* Indian mustard 3.6 (16:0), 1.1 (18:0), 13.9 (18:1), 21.5 (18:2), 13.7 (18.3),

*Brassica napus* Canola 4.7 (16:0), 0.1 (16:1), 1.6 (18:0), 66.0 (18:1), 21.2 (18:2),

*Carthamus tinctorius* Safflower 0.1 (14:0), 6.4 (16:0), 2.2 (18:0), 14.1 (18:1), 76.6 (18:2),

*Elaeis guineensis* Palm 0.5 (12:0), 1.0 (14:0), 38.7 (16:0), 3.3 (18:0), 45.5 (18:1),

*Helianthus annus* Sunflower 6.6 (16:0), 3.1 (18:0), 22.4 (18:1), 66.2 (18:2), 1.0 (18:3),

*Jatropha curcas* Physic nut 0.1 (12:0), 0.2 (14:0), 14.8 (16:0), 0.8 (16:1), 4.2 (18:0),

*Nicotiana tabacum* Tobacco 6.6 (16:0), 3.1 (18:0), 22.4 (18:1), 66.2 (18:2), 1.0 (18:3),

Yellow grease - 1.0 (14:0), 23.0 (16:0), 1.0 (16:1) 10.0 (18:0), 50.0 (18:1),

Brown grease - 1.7 (14:0), 23.0 (16:0), 3.1 (16:1) 12.5 (18:0), 42.5 (18:1),

The iodine value (IV) is an index of the number of double bonds in biodiesel, and therefore is a parameter that quantifies the degree of unsaturation of biodiesel. Both EN and ASTM standard methods measure the IV by addition of an iodine/chlorine reagent. Biodiesel viscosity is directly correlated to the IV of biodiesel for biodiesel with iodine numbers of

One of the main reasons for processing vegetable oils for use in engines is to reduce the viscosity thereby improving fuel flow characteristics. High viscosities can cause injector spray pattern problems that lead to excessive coking and oil dilution. These problems are associated with reduced engine life. Nevertheless, the necessary characteristics depend also on the end use; the engines for the production of energetic power in fact allow the use of

Density dictates the energy content of fuel where high densities indicate more thermal

The authors have already published the results of the measurement of the IV obtained for some oils selected as potential raw materials for BD production (Pirola et al., 2011). In Table 5 the values of IV, viscosity and density found by the authors for waste cooking oil and its mixture with raw rapeseed oil are shown, demonstrating that the properties of the feedstock can be improved by the use of blends of different oils. The values reported in the Table 5

energy for the same amount of fuel and therefore better fuel economy.

Table 4. Indicative acidic composition of some raw materials for biodiesel production.

**Iodine value, viscosity and density** 

between 107 and 150 (Environment Australia, 2003).

fuels with higher viscosity (i.e. from palm oil).

Lard - 4.8 (14:0), 28.4 (16:0), 4.7 (16:1) 14.8 (18:0), 44.6 (18:1),

*Glycine max* Soybean 10.7 (16:0), 3.0 (18:0), 24.0 (18:1), 56.6 (18:2), 5.3 (18:3),

3.2 (22:0)

8.7 (20:1), 33.5 (22:1)

5.2 (18:3), 0.9 (20:0), 0.3 (22:0)

0.2 (18:3), 0.2 (20:0) 0.2 (22:0)

10.8 (18:2), 0.1 (18:3), 0.1 (20:0)

0.2 (20:0), 0.2 (22:0)

0.3 (20:0), 0.4 (22:0)

41.0 (18:1), 38.6 (18:2), 0.3 (18:3)

0.3 (20:0), 0.4 (22:0)

2.7 (18:2)

15.0 (18:2)

12.2 (18:2), 0.8 (18:3)

**Oil Comon Name Fatty acid composition, wt%**  *Arachis hypogea* Peanut 11.9 (16:0), 3.0 (18:0), 40.0 (18:1), 40.7 (18:2), 1.2 (20:0),


Table 3. European Standard specifications for biodiesel (automotive fuels).

An indicative fatty acid methyl esters composition of the raw oils typically used for biodiesel production and of the ones adopted by the authors, is given in Table 4 (Velasco et al., 1998; Tyson, 2002; Winayanuwattikun at al. 2008, Zheng & Hanna, 1996).

Ester content % (m/m) 96.5 EN 14103

Viscosity 40°C mm2/s 3.50 5.00 EN ISO 3104

(10% dist.residue) % (m/m) - 0.30 EN ISO 10370

Cetane number 51.0 - EN ISO 5165 Sulphated ash % (m/m) - 0.02 ISO 3987

Total contamination mg/kg - 24 EN 12662 Cu corrosion max - EN ISO 2160

Water mg/kg - 500 EN ISO 12937

110°C h (hours) 6.0 - EN 14112

Acid value mg KOH/g - 0.5 EN 14104 Iodine value gr I2/100 gr - 120 EN 14111 Linoleic acid ME % (m/m) - 12.0 EN 14103 Methanol % (m/m) - 0.20 EN 14110 Monoglyceride % (m/m) - 0.80 EN 14105 Diglyceride % (m/m) - 0.20 EN 14105 Triglyceride % (m/m) - 0.20 EN 14105 Free glycerol % (m/m) - 0.02 EN 14105 Total glycerol % (m/m) - 0.25 EN 14105

Sulphur mg/kg - 10.0 preEN ISO 20846

Density 15°C kg/m3 860 900

Gp I metals (Na+K) mg/kg - 5.0

Gp II metals (Ca+Mg) mg/kg - 5.0 EN14538 Phosphorous mg/kg - 5.0 EN 14538

An indicative fatty acid methyl esters composition of the raw oils typically used for biodiesel production and of the ones adopted by the authors, is given in Table 4 (Velasco et

Table 3. European Standard specifications for biodiesel (automotive fuels).

al., 1998; Tyson, 2002; Winayanuwattikun at al. 2008, Zheng & Hanna, 1996).

**limits** 

**Min Max** 

**Method** 

EN ISO 3675 EN ISO 12185

preEN ISO 20884

EN 14108 EN14109

**Specification Units** 

Carbon residue

Oxidation stability,


Table 4. Indicative acidic composition of some raw materials for biodiesel production.

### **Iodine value, viscosity and density**

The iodine value (IV) is an index of the number of double bonds in biodiesel, and therefore is a parameter that quantifies the degree of unsaturation of biodiesel. Both EN and ASTM standard methods measure the IV by addition of an iodine/chlorine reagent. Biodiesel viscosity is directly correlated to the IV of biodiesel for biodiesel with iodine numbers of between 107 and 150 (Environment Australia, 2003).

One of the main reasons for processing vegetable oils for use in engines is to reduce the viscosity thereby improving fuel flow characteristics. High viscosities can cause injector spray pattern problems that lead to excessive coking and oil dilution. These problems are associated with reduced engine life. Nevertheless, the necessary characteristics depend also on the end use; the engines for the production of energetic power in fact allow the use of fuels with higher viscosity (i.e. from palm oil).

Density dictates the energy content of fuel where high densities indicate more thermal energy for the same amount of fuel and therefore better fuel economy.

The authors have already published the results of the measurement of the IV obtained for some oils selected as potential raw materials for BD production (Pirola et al., 2011). In Table 5 the values of IV, viscosity and density found by the authors for waste cooking oil and its mixture with raw rapeseed oil are shown, demonstrating that the properties of the feedstock can be improved by the use of blends of different oils. The values reported in the Table 5

Non Edible Oils: Raw Materials for Sustainable Biodiesel 13

A remarkable aspect of the proposed process is represented by the mild operative conditions, i.e. low temperature (between 303 and 338 K) and atmospheric pressure. Moreover, the adopted working temperature is the same of the following transesterification reaction and of the methanol recovery by distillation. Each single reaction has been carried out for six hours withdrawing samples from the reactor at pre-established times and analysing them through titration with KOH 0.1 M. The percentage of FFA content per weight was calculated as otherwise reported (Marchetti & Errazu, 2007, Pirola et al. 2010). All the esterification experiments have been conducted using a slurry reactor as the one already described elsewhere (Bianchi et al., 2010). A slurry reactor is the simplest type of catalytic reactor, in which the catalyst is suspended in the mass of the regents thanks to the

Much attention has been paid by the authors to the use of acid ion exchange resins. Amberlyst ®46 (named A46 in this chapter), i.e. a commercial product by Dow Advanced Materials, and D5081, a catalyst at the laboratory development stage by Purolite® have been successfully applied in this reaction. The main features of the employed catalysts are

D5081 Styrene-divinylbenzene R-SO3- H+ 1,0 130 A46 Styrene-divinylbenzene R-SO3- H+ 0,60 120

The acid capacity of the catalysts, corresponding to the number of the active sites per gram of catalyst was also experimentally determined by the authors by ion exchange with a NaClsaturated solution and successive titration with NaOH (López et al., 2007). The values were

A distinguishing feature of A46 and D5081 is represented by the location of the active acid sites: these catalysts are in fact sulphonated only on their surface and not inside the pores. Consequently, A46 and D5081 are characterized by a smaller number of acid sites per gram if compared to other Amberlysts®, which are also internally sulphonated (Bianchi et al.,

In Fig. 3 the results from the esterification reaction performed on different raw oils are

From the graph it can be noticed that in almost all the cases it is possible to obtain a FFA concentration lower than 0.5% wt after 6 hours of reaction. The differences in the acidic composition seem not to affect the final yield of the reaction. What seems to influence the FFA conversion is the refinement degree of the oil. Waste cooking oil (WCO) is in fact more hardly processable with the esterification in comparison to refined oils, probably due to its higher viscosity which results in limitations to the mass transfer of the reagents towards catalysts. Indeed, the required acidity limit is not achieved within 6 hours of reaction. Adding rapeseed oil, less viscous, to the WCO in different ratios it is possible to increase the

Table 6. Main features of the ion exchange resins adopted as catalysts in the FFA

found to be in agreement with the ones provided by technical sheets.

**Group Ionic form Acid capacity** 

**(meq H+/g)** 

**Max. operating Temp (°C)** 

**3.2.1 Experimental details** 

agitation.

reported in Tab. 6.

esterification reaction.

**3.2.2 Deacidification results** 

2010).

shown.

**Resin Matrix Functional** 

evidences that with the dilution with rapeseed oil it is possible to decrease the viscosity of WCO but increasing the number of IV. Nevertheless also in the case of most diluited sample the IV value is lower than those of rapeseed oil.


Table 5. IV, viscosities and densities of some potential raw materials for biodiesel production.

It has to be taken into account that after the transesterification process the IV of the feedstock remain unchanged, the viscosity is reduced from 10 to 15 times, whereas density has been found to remain almost the same or to be reduced in some cases (Zheng & Hanna, 1996).

#### **3.2 Oil standardization: Free fatty acids esterification reaction**

As already mentioned in the introduction paragraph, the use of raw, non edible oils poses the problem of standardization before the transesterification process, especially with regard to acidity decrease. In fact oils, besides triglycerides contain also free fatty acids (FFA). These lasts are able to react with the alkaline catalyst used for the transesterification reaction yielding soaps which prevent the contact between the reagents. A FFA content lower than 0.5% wt is also required by the EN 14214.

Among the different deacidification methods listed in the introduction, the authors have recently paid attention to the pre-esterification process (Loreto et al., 2005; Pirola et al., 2010; Bianchi et al., 2010). This method is particularly convenient as it is not only able to lower the acidity content of the oils but also provides methyl esters already at this stage, so increasing the final yield in biodiesel. A scheme of the FFA esterification reaction is given in Fig.2.

$$\begin{array}{cccc} \mathsf{R}\mathsf{C}\mathsf{O}\mathsf{O} & \mathsf{+} & \mathsf{C}\mathsf{H}^{3}\mathsf{O}\mathsf{H} & \mathsf{\stackrel{\text{acid catalyst}}{\longleftrightarrow}} & \mathsf{R}\mathsf{COOC}^{3} & \mathsf{+} & \mathsf{H}^{2}\mathsf{O} \\ \end{array}$$

Fig. 2. Scheme of the Free Fatty Acid Esterification Reaction.

The use of heterogeneous catalysts (Sharma & Singh, 2011) is usually preferred to the use of homogeneous ones (Alsalme et al., 2008) as it prevents neutralization and separation costs, besides being not corrosive, so avoiding the use of expensive construction materials. Another important advantage is that the recovered catalysts can be potentially used for a long time and/or multiple reaction cycles.

In the recent years the authors have deepened the study of the pre-esterification process investigating the effect of the use of different kinds of oils, different types of reactors and catalysts and different operating conditions (Pirola et al., 2010; Bianchi et al., 2010; Pirola et al. 2011)

In the following paragraphs, the most relevant aspects of the experimental work and the results obtained by the authors for what concerns the pre-esterification process are reported.
