Nanocomposite-assisted ammonium hydroxide-cottonseed biodiesel emulsion for improved combustion, performance, and emission control in a diesel engine

Nanostructured catalysts play a key role in controlling reaction pathways, stability, and performance in emerging energy systems. This study investigates a carbon nanotube-magnesium oxide (CNT-MgO) nanocomposite as a fuel-borne additive in an ammonium hydroxide-containing cottonseed biodiesel-diesel emulsion. The focus is on its dispersion behavior and its influence on combustion, performance, and emissions. The nanocomposite was synthesized and characterized using scanning electron microscopy (SEM) and x-ray diffraction (XRD) to confirm its morphology and phase composition. Its role was evaluated indirectly through combustion and emission characteristics under engine operating conditions. Stable dispersion of the nanocomposite within the fuel blend ensured sustained activity during combustion. The CNT-MgO additive improved reaction behavior, reduced carbonaceous emissions, and enhanced thermal efficiency compared with nanoparticle-free fuels. The increased nitrogen oxide (Nox) emissions associated with intensified combustion were effectively controlled using exhaust gas recirculation (EGR), without compromising overall performance. The results suggest that the nanocomposite enhances combustion and energy utilization of the ammonium hydroxide-containing fuel, likely by promoting more effective decomposition and oxidation processes. Overall, this study demonstrates the practical potential of CNT-MgO nanocomposites as combustion-supporting additives for renewable fuel systems, while enabling emission control through EGR.