Biodiesel yield (%) = product yield×FAME yield ×100% (3) FAME yield is determined by Agilent 7890A gas chromatography (GC) equipped with Flame Ionization Detector (FID) at 260 °C and Agilent DB-23 column (50%-Cyanopropyl-methylpolysiloxane; 30 m length × 0.25 mm internal diameter × 0.25 µm thickness; high polarity). The carrier gas is helium and the oven temperature is initially at 190°C then increases to 250°C at a rate of 40°C/min and stays at 250°C for 3.5 minutes. About 25 mg biodiesel, which is dissolved in 1 mL hexane (>99%) and 1 uL sample with 40:1 split ratio, is injected into GC for FAME identification and quantification. Fatty acid methyl esters are identified based on the comparison between …show more content…
The excess methanol can push the transesterification reaction forward and produces extracts (glycerin and methyl esters) to recover the surface of the catalyst (Chin et al., 2009; Yan, Lu, & Liang, 2007). In contrast, at higher reaction temperatures (> 130 °C) and at higher amounts of catalyst with increased methanol to oil molar ratio, the biodiesel yield decreases (Chin et al., 2009). This is caused by the large amount of methanol diluting the oil and reducing the biodiesel yield (Gao et al., …show more content…
The biodiesel yield will raise if the reaction temperature increases with the low amount of catalyst and the low molar ratio of methanol to oil (Chin et al., 2009). The transesterification is an equilibrium reaction, the temperature and pressure can affect the equilibrium constant. Thus, increasing temperature improves the biodiesel yield. Besides, mass transfer can be promoted by high temperature (Gao et al., 2008). However, at high temperature with higher methanol to oil molar ratio and higher amounts of catalyst, the biodiesel yield drops down dramatically (Chin et al., 2009), which may be caused by the presence of solid catalyst, the reaction mixture constitutes a three-phase system, oil-methanol-catalyst, where the reaction would be slowed down due to the diffusion resistance between different phases (Liu et al., 2008). However, the temperature would not be considered as a variable in this project. The room temperature (22°C) is set up and used in the whole experimental combinations, which is using another observing angle to analysis the biodiesel yield of the WCO compared to the other