Study on the solubilization mechanism between methanol and n-hexadecane by alcohol co-solvents based on quantum chemistry simulation

Methanol, as an ideal green oxygen-containing alternative fuel, is challenging to dissolve in non-polar diesel due to its strong polarity, which makes it prone to phase separation. This study aims to delve into the microscopic mechanisms behind the solubility and insolubility between methanol and diesel, as well as to thoroughly investigate the influence of butanol co-solvents on the solubility of methanol-diesel mixed fuels. The focus is on analyzing the effects of n-butanol and iso-butanol, complemented by an in-depth examination of intermolecular interactions using quantum chemistry simulation. The results of the miscibility experiments showed that n-butanol exhibited a better solubilizing effect compared to iso-butanol. However, the methanol ratio significantly influenced its solubility in the mixture, particularly when the volume ratio of methanol to n-hexadecane (the surrogate of diesel) was 1:1. In such cases, more solubilizers were required to maintain system stability. The partial charge on the hydroxyl group of n-butanol differs more significantly than that of iso-butanol, resulting in stronger intermolecular forces with the hydroxyl group of methanol. Furthermore, the analysis of intermolecular interactions revealed the crucial role of electrostatic forces in achieving mutual solubility. The molecular interaction strength of the mixed system with n-butanol was higher than that with iso-butanol (−38.75 kJ/mol compared to −37.10 kJ/mol), aligning with the experimental results and validating the accuracy of the quantum chemistry simulation. This study provides a theoretical basis for optimizing methanol-diesel blended fuel formulation and improving combustion characteristics, having significant practical implications for efficient, clean engine fuel development.