Experimental and molecular dynamics study of fuel desulfurization process using deep eutectic solvent

The sulfur-containing compounds in China's crude oil mainly exist in the form of thiophene (TPs). More than 80% of TPs are composed of dibenzothiophene (DBT). The combustion of sulfur-containing fuel oil pollutes the air. Studies have shown that DES, as a new solvent similar to ionic liquids, has the advantages of simple preparation, easy availability of raw materials and high extraction rate. In this paper, experiments on DES synthesis were carried out to screen DES with the best extraction efficiency, and the effects of extraction operation temperature and initial sulfur concentration of raw oil on DES extraction and desulfurization were explored. The DES separation mechanism for DBT extraction from n-heptane-DBT was used as the simulated oil. Quantum chemistry was calculated for 9 commonly used DES, and the hydrogen bonding between DES-DET-n-heptane was analyzed by using the obtained σ-Profiles map information, and the selected DES was compared with the auxiliary experiment from the perspective of quantum chemistry. Then, the molecular dynamics (MD) simulation between different DES and raw oil was carried out, that is, the non-bond interaction energy, radial distribution function, spatial distribution function and mean square shift results of DBT-Heptane-DES calculated by molecular dynamics were used to deeply analyze the microscopic separation mechanism of DES extraction desulfurization. The results show that the DES composed of choline chloride/diethylene glycol can theoretically perform more efficient desulfurization operations, and this theoretical analysis method can provide a strong basis for the desulfurization of other types of DES and the separation of other systems.