Today, the energy required is constantly increasing. Diesel engines are one of the important energy production methods. Diesel engines will continue to be used for many years due to their efficiency and long life. However, fossil fuels used in diesel engines have disadvantages such as being harmful to the environment and decreasing reserves. In this work, boron oxide (B2O3) nanoparticles were added to diesel fuel and their effects on emissions and engine performance were examined in an effort to prevent these drawbacks and improve the sustainability of diesel fuel. Three distinct B2O3 concentrations (10, 20, and 30 ppm) were added to diesel fuel for the investigation. Six distinct loads, ranging from 0.5 to 3 kW, were used to test the fuels while a four-stroke, single-cylinder diesel engine ran at a steady 3000 rpm. Response surface methodology (RSM) was used to optimize the experimental study's results in order to determine the ideal operating parameters. The findings of the study showed that 1.5 kW load and 9 ppm B2O3 added fuel were the ideal operating conditions. Carbon monoxide (CO) was estimated to be 0.0459%, hydrocarbon (HC) to be 24.2915 ppm, carbon dioxide (CO2) to be 5.0699%, nitrogen oxide (NOx) to be 522.5814 ppm, brake specific fuel consumption (BSFC) to be 384.7523 g/kWh, and brake thermal efficiency (BTE) to be 22.96% at these operating conditions. When these values are compared with D100, CO decreased by 39.61%, HC by 13.17%, and BTE by 14.14%, while CO2 increased by 11.68%, NOx by 15.87%, and BSFC by 23.33%. In the RSM study, the minimum correlation coefficient (R2) value belongs to BSFC with 91.34%. All error rates in the study are below 10% and vary between 1.69% and 6.47%.

The catalytic modification of combustion processes using nanoparticle additives has emerged as a promising strategy to improve fuel oxidation and reduce pollutant formation in compression ignition (CI) engines. In this study, the catalytic effects of nano-sized boron oxide (B₂O₃) on biodiesel combustion were systematically investigated. Jojoba oil, a non-edible and drought-resistant feedstock, was transesterified to produce second-generation biodiesel and blended with diesel fuel. Among the tested blends, J10 (10% biodiesel and 90% diesel) was selected as the base fuel blend due to its favorable combustion and emission characteristics. To explore catalytic enhancement mechanisms, B₂O₃ nanoparticles were introduced at concentrations of 25, 50, and 75 ppm. The high surface area and oxygen buffering capacity of B₂O₃ nanoparticles are expected to enhance oxidation reactions and promote radical formation during combustion. This catalytic effect contributes to improved combustion efficiency, as evidenced by a significant reduction in incomplete combustion products. Compared with diesel fuel (D100), HC emissions were reduced by up to 53.34%, while CO emissions decreased by 24.42–41.98% depending on the operating conditions and fuel blends. In addition, a noticeable improvement in combustion quality was reflected in the brake thermal efficiency (BTE), where variations of up to 11.61% were observed across different fuel blends. Response Surface Methodology (RSM) was employed to quantify the interaction between nanoparticle concentration and engine load and to identify optimal catalytic operating conditions. The optimal parameters were determined as 12.14 ppm B₂O₃ and 1.36 kW load, yielding a desirability of 0.7128. Under these conditions, the engine achieved a BSFC of 458.83 g/kWh and BTE of 22.01%, with emissions reduced to 0.041% CO, 14.29 ppm HC, and 346.44 ppm NO_x. The results demonstrate that nano B₂O₃ functions as a combustion catalyst by enhancing oxidation pathways and improving fuel-air interaction, thereby increasing combustion efficiency and reducing harmful emissions.