Solar Microwave-Assisted Synthesis of Modified Alkaline Catalysts for Biodiesel Production

The global demand for eco-friendly energy sources has intensified the need for sustainable methods to synthesise modified alkaline catalysts for biodiesel production. Traditional methods are often costly and environmentally harmful. This study aims to develop high-efficiency, waste-based, modified alkaline catalysts using solar microwave-assisted synthesis. The focus is on optimising catalyst activity to enhance biodiesel yield from sunflower and waste cooking oil. Using the coprecipitation method, caO-rich hydrotalcite-like compounds (HLCs) were synthesised by impregnating Mg-Al hydrotalcite (HT Mg-Al) with 40 wt% eggshell-derived CaO. The study compared different drying methods, times, energy consumption, and costs involved in synthesising the catalysts. Characterisation techniques such as X-ray diffraction, BET, and SEM were used to analyse the catalysts’ physicochemical properties. The catalytic activity was tested by transesterifying sunflower and waste cooking oil with methanol under microwave heating. Results showed that microwave drying significantly increased biodiesel yield compared to conventional methods. This study explores the originality of using a solar microwave-assisted method for catalyst synthesis and a conventional microwave for transesterification. The microwave-assisted technique achieved a 93.2% yield of fatty acid methyl esters (FAME) with a 30-minute reaction duration, 700 W microwave power, methanol-to-oil ratios of 6:1 and 9:1, and catalyst loading of 4 and 12 wt%. The catalysts were dried in 30 minutes, consuming only 0.9 kWh, demonstrating substantial energy savings when using a solar microwave power rating of 900W. In conclusion, this study successfully developed high-efficiency, waste-based, modified alkaline catalysts using solar microwave-assisted synthesis. This method enhances sustainability and economic viability in biodiesel production by promoting waste valorisation and reducing environmental pollution using waste-based materials.