Synergistic effects of TiO2 nanoparticles and isopropanol–butanol–ethanol (IBE)-enriched biodiesel blends on combustion and emission performance in diesel engines equipped with diesel oxidation catalyst and selective catalytic reduction

Increasingly stringent emission regulations necessitate integrated strategies to improve combustion efficiency and reduce exhaust emissions in compression-ignition engines. The combined effects of titanium dioxide (TiO 2 ) nanoparticles and isopropanol–butanol–ethanol (IBE)-enriched biodiesel–diesel blends were experimentally investigated in a diesel engine equipped with a diesel oxidation catalyst (DOC) and selective catalytic reduction (SCR) aftertreatment system. Diesel, 30 vol% biodiesel (B30), and B30–IBE blends containing 30, 60, and 90 ppm TiO 2 were evaluated under different engine loads. IBE generally improved fuel–air mixing, whereas its high latent heat of vaporization tended to increase fuel consumption under certain conditions. TiO 2 exhibited concentration-dependent behavior, with 30–60 ppm providing a balanced overall response. Oxygenated blends reduced carbon monoxide (CO) and hydrocarbon (HC) emissions, while TiO 2 further promoted oxidation. The integrated DOC + SCR system achieved CO, HC, and nitrogen oxides (NO x ) conversion efficiencies of up to 100%, 76%, and 59%, respectively.