ACS Omega. 2022 Jun 8;7(24):20619-20633. doi: 10.1021/acsomega.2c00682. eCollection 2022 Jun 21.
Utilization of agricultural waste such as nonedible seed oil for the synthesis of biodiesel via catalytic transesterification is one of the effective ways for the partial replacement of petroleum-based fuels in the area of renewable energy development and is beneficial to CO, CO2, and unburned hydrocarbon (HC) emission reduction to the environment. In this regard, the current study investigates the synthesis of fatty acid methyl esters (FAMEs) from Croton macrostachyus kernel oil by considering parameter interaction and optimization to maximize the yield of fatty acid methyl esters (FAMEs). The response surface methodology-central composite design (RSM-CCD) was applied to optimize the C. macrostachyus fatty acid methyl ester (CMKO-FAME) synthesis process by varying the process parameters such as reaction time (1-2 h), molar ratio (6:1-12:1), and catalyst loading (1-2 wt %). The optimum conditions for the transesterification of C. macrostachyus kernel oil (CMKO) were found to be a methanol to oil ratio of 11.98:1, catalyst loading of 1.03 wt %, and reaction time of 2 h, resulting in the conversion of 95.03 wt % C. macrostachyus kernel oil into its mono FAMEs. The fuel properties of CMKO and its FAMEs were determined based on ASTM D6751 and EN 14214 standards. Further, the CMKO and its FAMEs were characterized using Fourier transform infrared (FT-IR), gas chromatography-mass spectrometry (GC-MS), and nuclear magnetic resonance spectroscopy (NMR). The fatty acid composition of CMKO was myristic acid (1.36%), palmitic acid (11.35%), stearic acid (5.11%), oleic acid (18.64%), gadoleic acid (0.34%), linoleic acid (49.084%), and linolenic acid (14.1%). The purity of the produced methyl esters was determined by 1H NMR and found to be 95.52%, which was quite in good agreement with the experimentally observed yield of 95.39 wt %. The produced CMKO-FAME was blended with diesel fuel at various ratios (B5, B10, B15, and B20) to evaluate the engine performance and emission characteristics in a diesel engine. The engine brake thermal efficiency is lower, the brake-specific fuel consumption (BSFC) using CMKO-FAME blends is higher, and the temperature of exhaust gas emitted after combustion also increased as compared to diesel fuel. Similarly, using produced FAME blends, the emission emitted such as HC, NOx, and CO is reduced. However, the engine fueled with the produced FAME blends increased the level of CO2 into the atmosphere when compared to diesel fuel. The performance and emission characteristics of diesel engine result show that the blend of CMKO-FAME and diesel can be used as a fuel in a diesel engine without any modification of the engine.