Synthesis of biodiesel from Cocos nucifera copra oil, an agricultural residue / Mohd Idham Hakimi Razali

Mohd Idham Hakimi , Razali (2017) Synthesis of biodiesel from Cocos nucifera copra oil, an agricultural residue / Mohd Idham Hakimi Razali. Masters thesis, University of Malaya.

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Abstract

The residue, especially from the agricultural industry has the potential of being used as a value-added product such as biofuel, pharmaceutical compound and compost fertilizer. In addition, utilization of agricultural residue could reduce the amount of waste being sent to the landfill and contributes toward environmental sustainability. Therefore, this study will emphasize on the potential of matured Cocos nucifera copra residue as an alternative bioresource for second generation of biodiesel. The study was initiated by determining the optimum oil yield that can be extracted from copra residue by using three different techniques; Soxhlet extraction (SXE), ultrasonic-assisted extraction (UAE), and microwave-assisted extraction (MAE). In addition, the volume (mL) of hexane as solvent and extraction time (min (minute) / hour (hrs)) are also recorded. The results depicted that the copra residue oil (CRO) extracted using SXE (48 hrs/ 400 mL) produced the highest yield, compared to UAE (30 min/ 300 mL) and MAE (15 min/ 100 mL) which are 81.39%, 75.80%, and 62.97%, respectively. Then, the experiments were continued by analysing the free fatty acids (FFA) by using gas chromatography-mass spectrometer (GCMS), as the FFA content exceeding 5% would cause saponification during the transesterification process, which will affect the conversion of CRO to biodiesel. The results of the analysis showed UAE contained the lowest FFA concentration (0.18 - 0.27%) compared to SXE and UAE. Finally, transesterification is performed using methanol and potassium hydroxide (KOH) as a catalyst for converting CRO to biodiesel. The transesterification processes were designed using adaptive neuro-fuzzy inference system (ANFIS) and response surface methodology (RSM) to optimize biodiesel yields by comparing different methods (conventional and in-situ) and techniques (stirring hot plate-assisted (HT), ultrasonic-assisted (UT), and microwave-assisted (MT)). The transesterification results indicated that the highest biodiesel yield was synthesised using conventional method with HT technique of transesterification (3:1, methanol to oil ratio (v/w) / 1% catalyst to oil weight (w/w)) showing 96.85% biodiesel yield. Overall, it is observed that SXE method is more efficient in extracting oil from copra residue. On the other hand, CRO extracted using MAE and UAE are more suitable to be used for biodiesel synthesis since the content of FFA are lower compared to the one extracted using SXE. In addition, conventional method with HT technique of transesterification could be a better option for biodiesel synthesis from CRO.

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