LAUSR

The use of biodiesel can reduce dependence on diesel, and the compression ignition (CI) engine's performance with biodiesel is substantially low but could be improved by emulsifying nano-additives. Biodiesel production and performance in CI engines using a homogeneous catalyst is less efficient, expensive, and time-consuming. In this research article, magnesium-doped calcium oxide (Mg–CaO), a novel heterogeneous nanocatalyst, was synthesized and then used to generate biodiesel from Sapindus trifoliatus seed oil. The catalyst surface characterization was analyzed using the surface imaging method, energy dispersive x-ray analysis, x-ray diffraction analysis, and Fourier-transform infrared spectroscopy. Then, the nanocatalyst (30 ppm Mg–CaO) is emulsified in its nano form with the Sapindus trifoliatus biodiesel (STBD) at B25 (STB25% + diesel75%) blend and investigated in the CI engine. The highest yield of 91.75% of biodiesel was achieved at 58 °C, 73 min, 4% catalyst concentration (w/w), and 15:1 methanol:oil molar ratio. The performance results were obtained using STBD25, STBD25 blended with CaO nano-additives (STBD25 + 30 ppm CaO) and STBD25 blended with Mg-doped CaO nano-additives (STBD25 + 30ppm Mg–CaO) are compared to the baseline values obtained from diesel. From the comparison, it is revealed that STBD25 + 30ppm Mg–CaO has a greater influence on combustion, performance, and emission characteristics as follows: (i) in-cylinder pressure increased by 3.22%, 6.24%, and 9.02%, (ii) heat release rate increased by 1.68%, 16.69%, and 32.5%, (iii) brake thermal efficiency is found to be increased by 4.56%, 8.23%, and 11.79%, (iv) hydrocarbon (HC) decreased by 21.12%, 6.06%, and 11.43%, (v) carbon monoxide (CO) decreased by 0.04%, 0.01%, and 0.01%, and (vi) smoke decreased by 22.61%, 8.11%, and 14.25%, compared with diesel, STBD25 + 30 ppm CaO, and STBD25 at full load conditions. Oxides of nitrogen (NOx) released while using STBD25+Mg-doped CaO in CI engine were observed to decrease compared with STBD25 and STBD25+CaO (by 10.72% and 18.64%) and an increase compared with diesel (by 8.64%).