Refined, bleached and deodorized (RBD) palm oil is one of the interesting renewable resources in biolubricant application. It is due to some advantages such as biodegradable, non-toxic, excellent lubricity and high viscosity index properties. However, direct application of RBD palm oil as biolubricant is restricted due to its poor low temperature property, which limits its use at low operating temperature. This drawback can be overcome by molecule structural redesign through chemical modification process. To produce palm oil based biolubricant with good pour point, epoxidized palm oil (EPO) was chemically modified via ring opening process. EPO was reacted with oleic acid in the presence of p-toluenesulfonic acid (PTSA) as catalyst. The molecular structure confirmation of ring opening product which is palm oil hydroxy oleate (POHO) was proven through the oxirane oxygen content (OOC) value, iodin value, hydroxyl value, Fourier transformation infra-red (FTIR), proton and carbon nuclear magnetic resonance (1 H-NMR and 13 C-NMR) spectroscopy analysis. The physicochemical properties of POHO were determined through its pour point and flash point values. The results showed that the ring opening process for putting bending and branching molecule structures of the oil have improved the pour point (-8.5 o C) and increased the flash point of the biolubricant (255 o C).
In the presence of a catalyst, p-toluenesulfonic acid (PTSA), the ring of epoxidized palm oil (EPO) was opened using oleic acid (OA). The optimization effects of different process variables including the mol ratio of EPO/OA, reaction temperature, PTSA percentage and reaction time was performed by response surface methodology (RSM). To assess the effects of process variables and interactions among them, a D-optimal design was used as an RSM tool to acquire the maximum response value. The following are the optimum conditions achieved at the reaction time of 4.73 h in the RSM study: 1.02% PTSA, 3 EPO/OA mol ratio and 119.14 ºC reaction temperature. These conditions resulted in 84% yield, 0.041% oxirane oxygen content (OOC), 59.4 mg/g iodine value (IV), and118.7 mg/g hydroxyl value (HV). The results are in a excellent agreement with the values predicted using a regression model.
The epoxidation process of RBD palm oil was carried out using in situ generated performic acid. The effect of various process variables such as the formic acid towards hydrogen peroxide mole ratio, the reaction temperature and the reaction time were optimized by using response surface methodology (RSM). The D-optimal design was used to evaluate the influence of process variables and their interaction in order to obtain the process optimum conditions. The results showed that the optimum conditions of the epoxidation process were at 5.91 mole ratio of formic acid towards 3.60 mole of hydrogen peroxide, reaction temperature of 40ºC and reaction time of 2.55 h. At the optimum condition, the epoxidised RBD palm oil (EPO) yield was 86% with oxirane oxygen content (OOC) of 3.46%. The results showed in good agreement with the predicted values from the RSM model.
Response surface methodology (RSM) is one of the statistical approaches that can be used to determine the correlation between extraction parameters and the extraction yield of bioactive compounds. Citrullus lanatus rind contains various therapeutic values but has often been discarded as waste. This study aims to find the optimum extraction conditions for the yield of C. lanatus rind extract, perform phytochemical screening, and determine the antioxidant activities. Extraction was carried out by maceration technique using methanol as a solvent with a solids-to-solvent ratio of 1:30 w/v. The extraction conditions of C. lanatus rind were optimized using RSM and the optimum yield of 37.24 % was predicted at 41.7 °C after 6 h of extraction. The average actual yield obtained at the optimum conditions was 37.01 % ± 0.66, indicating good agreement with the predicted value. The phytochemical screening of methanolic rind extract revealed the presence of alkaloids, saponins, glycosides, phenols, and flavonoids. The total phenolic content of methanolic rind extract ranging from 56.975 to 88.245 mg GAE/g using gallic acid as a standard, and the DPPH radical scavenging activity with IC50 value of 443.10 µg/mL was obtained. This study demonstrated that this unutilized C. lanatus rind contains bioactive substituents and can act as a promising natural antioxidant. HIGHLIGHTS Response surface methodology (RSM) was utilized to optimize the extraction conditions to achieve the highest extraction yield of Citrullus lanatus rind Both extraction parameters (time and temperature) had a significant effect on the extraction yield with time having a greater effect on extraction yield The methanolic extract of Citrullus lanatus rind revealed the presence of several classes of phytochemicals including alkaloids, saponins, glycosides, phenols and flavonoids Significant total phenolic content with the radical scavenging activity of more than 90 % at 1,000 ppm showed that the Citrullus lanatus rind may be a promising candidate for natural antioxidants GRAPHICAL ABSTRACT
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