Microwave-assisted acid-catalyzed synthesis and analysis of biodiesel using multiple feedstocks

Fatty acid alkyl esters (FAAE) were synthesized under microwave-assisted acid-catalyzed transesterification using various feedstocks (canola, castor, coconut, corn, ghee, olive, palm olein, peanut, soybean, sunflower oils, and waste vegetable oil (WVO)) with methanol and ethanol and H2SO 4 as a catalyst. Biodiesel is a good alternative to petroleum diesel fuel because it is renewable, biodegradable, and nontoxic. In this study, microwave-assisted transesterification (MAT) was used to expedite the reaction time using acid catalysts. FAAE were synthesized by MAT using oil/alcohol volume and molar ratios, MAT using high temperature for canola and soybean oils, and MAT using SiO2/ 50% H2SO4 as solid catalyst for castor oil. Reaction parameters such as oil/alcohol ratio, reaction temperature, reaction time, and catalyst loading were optimized for each oil. All FAAE were analyzed using 1H--NMR spectroscopy and GC/MS. Experimental results showed that MAT is energy efficient compared to CHT (conventionally-heated transesterification) using volume ratios. Also, MAT using molar ratios showed better conversion for most of the oils compared to volume ratios. Castor oil was the best oil to produce FAME (fatty acid methyl esters) using both methods. Complete conversions were observed for elevated temperature experiments for 10 min and more than 80% conversions were obtained using solid catalyst for 45 min.