*3.3.1 Homogeneous acid esterification of gongo oil*

**Table 2** presents the results of the physicochemical characterization revealed for the esterified gong oil. Regarding the water content, when compared with **Table 1** (characterization of the oil in natura), it is observed that there was a significant increase (from 0.17 to 0.8) in the moisture content of sample 1 and for sample 2 there was a decrease, around 26% of moisture (from 0.19 to 0.14). The increase in water content in sample 1 may have occurred due to the inefficiency of the dehumidification stage, since during dehumidification water is formed as a byproduct. On the other hand, it is observed that sample 2 met the specification for biodiesel production since it revealed 0.14%.

The acidity index for both sample 1 and sample 2 showed significant reduction in the range of 46% (from 3.26 to 1.5 mg KOH/g) and 32% (from 4.41 to 1.09 mg KOH/g) respectively. However, these values are above the specification of RDC270 ANVISAMS, whose optimal limit is 0.6 mg KOH/g of the sample. Oil treatment by homogeneous acid esterification significantly improved the quality of gong oil for biodiesel production. The FFA content also significantly reduced around 52% for sample1 (from 1.63 to 0.35%) and 32% for sample 2 (1.74 to 0.55%). Although the reduction is significant the treatment of the crude oil did not reach the desired specification on the order of 0.5% in sample1, however, in the light of statistics this is a small difference that does not prevent the esterified gong oil from being used in the manufacture of biodiesel.

As for the saponification index (Is), it was observed that there was some stabilization of the said quality control parameter in the range of 103–108 mg KOH/g of the sample indicating that according to English quality standards gong oil is not considered first quality.

Regarding the density, it was observed that there was a stable density in the range of 905–908 km/m3 as the majority acid in gong oil is C12:0 containing greater


**Table 2.**

*Physical–chemical characterization of esterified gong oil [20].*

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

intermolecular interaction due to its simple bonds in the carbon chain the density becomes high and tends to reduce when the raw material is subjected to treatment involving high temperature, as occurred with the gong oil in the course of the acid homogeneous esterification process.

The results obtained after the esterification of the gong oil as shown in **Table 2** led us to infer that the esterification treatment of this oil was efficient because it significantly reduced the FFA content, but not effective enough to reach the desired level (0.5% FFA). **Figure 5** illustrates the physical aspect of Pachymerus nucleorum and its oils.

#### *3.3.2 Homogeneous transesterification of esterified oil*

The production of biodiesel from fresh gong oil was carried out in two steps: homogeneous acid esterification and homogeneous basic transesterification, using 0.018 mol of oil and 0.142 mol of transesterification agent (methanol), 1% alkaline catalyst (0.05 g NaOH), in relation to the mass of oil molar ratio between oil and methanol in the order of 1:8 (one to eight), reaction temperature of 90°C and residence time of 120 minutes.

When the feedstock for biodiesel production contains a high content of free fatty acid, the yield through alkaline homogeneous transesterification method is low with soap formation and deactivation of the catalyst. A viable alternative to adapt this oil to the biodiesel process is its treatment through homogeneous acid esterification aiming to reduce its free fatty acids. **Figure 6** shows the visual aspect from the extraction of gong oil to the biodiesel obtained on a laboratory scale from this esterified oil.
