**2.2 Thermal extraction of coconut oil**

The larvae of Pachymerus nucleorum are washed thoroughly with clean water in a 1.00 mm sieve. They are then added to an aluminum tank with a capacity of 2000 mL and heated to about 120°C, until they release all the oil contained in them. After cooling, the oil is filtered and stored in polyethylene bottles and made available for physical–chemical characterization.

The extractive performance of gong oil is evaluated as a function of the refined oil mass and the mass of oil used throughout the extraction. The yield was calculated using the following equation.

$$\text{INCOME} = \frac{\text{OL}\_{\text{produced}(\text{g})}}{\text{Gongo}\_{\text{used(g)}}} \cdot \mathbf{100} \tag{1}$$

#### **2.3 Physical-chemical characterization of the oil extracted from the gong**

The oil extracted from Pachymerus nucleorum larvae was physicochemically characterized in terms of acidity index (A.I.), free fatty acids (FFA), moisture content (%H2O), density (D) and saponification index (Is) as recommended [17–19].

*Processing of Gong Oil (*Pachymerus nucleorum*) to Obtain Biodiesel by Methyl Route DOI: http://dx.doi.org/10.5772/intechopen.97721*

The acid value is defined as the number of milligrams of potassium hydroxide (mm KOH/g of sample) sufficient to neutralize the fatty acids present in a given quantity of oil or fat. This parameter is determined by the neutralization titrimetric method. In a typical assay, approximately 2.0 g of the sample is weighed into a 250 mL conical flask and 25 mL of neutralized alcohol (96°GL ethanol + ethyl ether in a 1,2 ratio) and 3 to 5 drops of the phenolphthalein indicator are added. This mixture was titrated with 0.1 Mol. L�<sup>1</sup> until it turned from colorless to pink. The acidity index was expressed in mg KOH/g of sample and calculated using the equation below:

$$IA = \frac{V\_{spend} \cdot [NaOH] \cdot f\_c \cdot \text{56, 1}}{P\_{sample}} \tag{2}$$

Where, Vgasto is the volume of NaOH spent in the titration; [NaOH] is the molar concentration of NaOH; fc is the correction factor of the NaOH solution; 56.1 milliequivalent gram of KOH and Pamsample is the weight of the sample.

The content of free fatty acids (FFA) contained in the samples is determined analogously to the acid value. The percentage of free fatty acids in terms of oleic acid (O.A.) was calculated according to the following equation.

$$\text{AGL} = \frac{V\_{spend} \cdot [\text{NaOH}] \cdot f\_c \cdot \text{28, 2}}{P\_{sample}} \tag{3}$$

Where, 28.2 corresponds to the milliequivalent gram of oleic acid.

The determination of the water content consists of the difference between the mass of the sample considered wet (Aúmida) and the mass of the dry sample (Aseca) after being submitted to drying in an oven for a period of 3 hours at 110 � 5°C. The percentage of water contained in the samples was determined by the following equation.

$$\%H\_2O = \frac{Peso\left(A\_{wet} - A\_{dry}\right)}{Peso\left(A\_{wet}\right)} \times 100\tag{4}$$

The saponification index (Is) is defined as the number of milligrams of potassium hydroxide required to neutralize the fatty acids, resulting from the hydrolysis of one gram of the sample. The saponification index is determined by the Koesttstafer method, and consisted of heating a mixture containing 2.0 g of the sample and 25 mL of 4% alcoholic KOH solution, with a reflux cooler, for 30 minutes at a mild temperature (approximately 50°C), followed by titration with hydrochloric acid at 0.5 Mol. L-1. Analogously, a blank sample is carried out. The saponification index was determined by the following equation.

$$I\_s = \frac{\left(V\_{white} - V\_{sample}\right) \times f\_C \times 28}{\text{Weight}\_{sample}} = mg\text{KOH}/g\_{sample} \tag{5}$$

Where, Vsample is the volume of HCl spent in the titration of the treated sample; Vblank is the volume of HCl spent in the titration of the blank sample; fc is the correction factor and SampleWeight is the weight of the sample used during the analysis.

Density is the mass per unit volume at a specified temperature. Parameter determination was performed by the pycnometry method. In a typical analysis, a 5 mL capacity pycnometer was weighed dry (m1). Vegetable oil was then added

until it reached its maximum capacity. The system was weighed (m2) again and by mass difference (m2- m1) the mass of the oil and its density (D) were determined using the following equation:

$$D = \frac{mass\_{oil}}{Volume\_{pyccounter}}\tag{6}$$

#### **2.4 Heterogeneous acid esterefication from gong oil**

The gong oil samples containing high free fatty acid (FFA) content are previously treated by the homogeneous acid esterification method, in order to reduce the acidity content and make it suitable for homogeneous alkaline transesterification. In this step the homogeneous acid catalyst, sulfuric acid (H2SO4) is used.

The homogeneous acid esterification reactions are carried out in a round bottom flask of 500 mL capacity, coupled to a reflux system kept under rigorous stirring at 70°C for 3 hours.

In a typical experiment, 0.018 mol of gong oil is added 0.142 mol of methanol and 0.4% catalyst relative to the base mass of the oil, with a molar ratio of 1:8 (one to eight) between the oil and methanol. The system is kept in rigorous stirring throughout the process. The reaction time consisted of 240 minutes and temperature around 90°C. The product is recovered using the centrifugation technique, rotating at 2500 rpm, for 15 minutes. The oily part is subjected to heating at 100°C, to eliminate water and methanol residues and destined later for physicalchemical characterization, to measure the efficiency of the esterification process and also for biodiesel production by conventional alkaline transesterification methylation route.

## **2.5 Basic trasnesterification of esterified gong oil**

The esterified gong oil containing reduced free fatty acid content is subjected to the traditional basic transesterification process to obtain biodiesel.

The biodiesel production is carried out in a flat-bottomed flask containing three mouths and 250 mL capacity, coupled to a reflux system.

In a typical experiment, 5.0 g (0.018 mol) of the starting vegetable oil is added to 4.6 g of methanol (0.144 mol) and 0.05 g of alkaline catalyst, NaOH, (1% relative to the base mass of the oil), with a molar ratio of 1:8 (one to eight) between the oil and methanol. The system is kept under strict magnetic stirring throughout the process. The reaction time consisted of 120 minutes and temperature of 90°C. The reaction mixture is added into a settling funnel for phase separation. The lower, glycerinous phase (by-product) was discarded and the upper phase (methyl ester mixture) was washed with acidulated sulfuric acid water (H2SO4 at 0.01 Mol. L�<sup>1</sup> ) and subsequently with heated water until the final product was clear. **Figure 3** shows the traditional alkaline transesterification process of obtaining biodiesel from esterified gong oil.

### **2.6 Characterization of gongo biodiesel**

Different electroanalytical techniques are currently used to quantify and qualify biodiesel aiming the knowledge of the physical–chemical profile of this energy input and also to adapt it to the specifications required by the National Agency of Petroleum, Natural Gas and Biofuel (ANP), the Brazilian agency responsible for the quality control of petroleum products and biofuels. In this specific case, biodiesel was characterized in terms of spectroscopy in the infrared region (IR) and gas chromatography (GC) [21].

*Processing of Gong Oil (*Pachymerus nucleorum*) to Obtain Biodiesel by Methyl Route DOI: http://dx.doi.org/10.5772/intechopen.97721*

**Figure 3.** *Basic homogeneous transesterification process of gong oil [20].*

### *2.6.1 Fourier transform infrared spectrocospy*

Fourier transform infrared spectroscopy (FTIR) is a widely used technique in qualitative analysis, synthesis, and biochemical transformations. FTIR measures the vibrational transition when a material absorbs energy in the infrared (IR) region. Different functional groups and their bond types exhibit infrared absorption frequencies and intensities. This electroanalytical technique is a highly relevant tool for identification and structural elucidation of a chemical substance, in addition to enabling the control and monitoring of reactions [22].

The absorption spectra in the infrared region with Fourier transform (FTIR) for the esterified gong oil and biodiesel were recorded in the range of 400–4000 cm<sup>1</sup> , using a KBr tablet. The tests were performed at the Institute of Chemistry, UFRJ, in a PerkinElmer spectrophotometer, model spectrum 100 with spectral resolution of 4 cm<sup>1</sup> .

#### *2.6.2 Gas chromatography with flame ionization detector*

The chromatography technique with flame ionization detector (GC-FID) is used for the determination of the total content of fatty acid methyl or ethyl esters (FAME) from the transesterification reaction of vegetable oils and/or animal fats. The ANP specifications contained in Resolution No. 45 of August 2014 (ANP 45/2014) for analysis of the content of esters present in biodiesel were constituted based on the EN 14103 and ANBT 15342 standards. The technique of gas chromatography with flame ionization detector (GC-FID) for determination of the total ester content requires analytical standards of each FAME to confirm the results [22].

Compositional analysis of the constituent methyl esters of biodiesel produced from esterified gong oil was performed using a gas chromatograph 7890A CG series from Agilent Technologies coupled with a flame ionization detector (GC-FID). This equipment used a CPWAX 52CB capillary column 30 m long, internal diameter 0.25 mm, film thickness 0.25 μm, under the following conditions: injection volume = 0.5 μL, oven at 175°C, injector temperature at 250°C, detector temperature = 390°C, hydrogen pressure = 200 kPa, flow rate of 2 mL min<sup>1</sup> and analysis time of 20 minutes. After obtaining the chromatogram the composition was calculated from the area of each of the respective fatty acid esters. The characterization

of the biodiesel fat profile of gong by GC-FID was performed at the School of Chemistry, Federal University of Rio de Janeiro.
