Investigating the Impact of Curry Leaf Oil Blending with Diesel on Soot Nanostructure and Its Oxidative Reactivity

Particulate matter (PM) from diesel combustion poses significant health and environmental risks, prompting strict regulations. Converting carbonaceous PM into CO₂ is an effective mitigation strategy. Biodiesels and renewable bio-additives have gained ground over the last two decades and have behaved as promising solutions to surpass the regulatory standards set by administrative bodies. This study evaluates the impact of blending a novel bio-additive, i.e. curry leaf oil (CLO), with diesel to reduce soot emissions. Soot generation was assessed using a smoke point apparatus with a wick-fed laminar diffusion flame. The nanostructural characteristics of the collected soot were analysed using HRTEM, XRD, Raman, and BET surface area analysis. CLO addition reduced the soot particle size with enhanced soot nanostructural disorder and greater fringe tortuosity. The disordered soot exhibits significantly enhanced reactivity with O₂, lowering the activation energy for oxidation to CO₂ by ∼30 kJ/mol compared to pure diesel soot. The GCMS analysis identified dioctyl phthalate (DOP) along with other components of CLO, suggesting its role as an oxygen-rich fuel additive, possibly enhancing the soot oxidation rates during combustion. Such a bio-additive strategy, therefore, may prove to be highly beneficial in reducing the carbonaceous PM emissions from varied combustion systems to the environment.