Journal of Energy Bioscience 2024, Vol.15, No.2, 72-84 http://bioscipublisher.com/index.php/jeb 74 3 Production Processes of Biodiesel from Rapeseed Oil 3.1 Extraction of rapeseed oil The extraction of rapeseed oil is a critical initial step in the production of biodiesel. This process involves several methods, each with its own advantages and limitations. The primary goal is to obtain high-quality oil that can be efficiently converted into biodiesel. One common method for extracting rapeseed oil is mechanical pressing, which involves crushing the seeds to release the oil. This method is straightforward and does not require the use of solvents, making it environmentally friendly. However, the oil yield from mechanical pressing can be lower compared to other methods.Another widely used method is solvent extraction, which typically involves the use of hexane. This method can extract a higher percentage of oil from the seeds compared to mechanical pressing. However, it requires careful handling and disposal of the solvent to avoid environmental contamination. The use of hexane as a co-solvent has been shown to improve the conversion efficiency of the transesterification process, which is crucial for biodiesel production (Qiu et al., 2011). In-situ alkaline transesterification is another innovative approach that combines oil extraction and transesterification in a single step. This method has been shown to achieve high conversion rates of rapeseed oil into fatty acid methyl esters (FAME), which are the main components of biodiesel. For instance, a study demonstrated that in-situ alkaline transesterification with methanol could achieve a conversion rate of 98%, making it a highly efficient method for biodiesel production (Qian et al., 2013). 3.2 Transesterification process The transesterification of rapeseed oil is a pivotal step in converting the extracted oil into biodiesel. This process involves reacting the oil with an alcohol (commonly methanol or ethanol) in the presence of a catalyst to produce fatty acid methyl esters (FAMEs) or fatty acid ethyl esters (FAEEs), which are the chemical constituents of biodiesel. Several studies have explored different conditions and catalysts to optimize the transesterification process. For instance, the use of subcritical methanol conditions has been shown to yield high amounts of methyl esters even at relatively low pressures, which is advantageous for industrial applications (Encinar et al., 2012). The variables affecting the yield include the type and amount of catalyst, reaction temperature and pressure, and the methanol to oil molar ratio. The presence of co-solvents like hexane can also influence the reaction efficiency (Encinar et al., 2012). In another approach, in-situ alkaline transesterification has been employed, where the oil extraction and transesterification occur simultaneously. This method has demonstrated high conversion rates of rapeseed oil to FAMEs, with significant reductions in glucosinolate content, making the remaining rapeseed meal suitable for animal feed (Qian et al., 2013). The process parameters, such as the methanol to oil molar ratio and the reaction temperature, are crucial for achieving optimal conversion rates and product quality. Ultrasonic-assisted transesterification in supercritical ethanol conditions is another innovative method that has been investigated. This technique uses ultrasonic emulsification to enhance the reaction between rapeseed oil and ethanol, resulting in high yields of FAEEs under mild conditions. The use of heterogeneous catalysts, such as ZnO/Al2O3 and SrO/Al2O3, has been shown to further improve the efficiency of the process (Mazanov et al., 2016). The optimal conditions for this method include a high pressure of 30 MPa and a temperature range of 623 K to 653 K, with an ethanol to oil molar ratio of 12:1 to 20:1 (Mazanov et al., 2016). 3.3 Recent advancements in production technologies Recent advancements in the production technologies of biodiesel from rapeseed oil have focused on improving efficiency, reducing environmental impact, and optimizing reaction conditions. One notable advancement is the use of ultrasonic-assisted transesterification, which has been shown to significantly enhance the reaction rate and yield. For instance, a study utilizing ultrasonic-assisted biodiesel production from a specific genotype of rapeseed
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