Abstract: Using caprolactam as hydrogen bond acceptor and lactic acid as hydrogen bond donor, a lactic acid based deep eutectic solvent(DES) was synthesized. The hydrogen bond interaction between caprolactam and lactic acid was determined by FT-IR and 1H NMR. Using dibenzothiophene (DBT) and n-octane as simulated oil,the lactic acid based DES as extractant and cocatalyst, hydrogen peroxide as oxidant and ammonium molybdate as catalyst, the effects of reaction temperature, n(H₂O₂) /n(DBT), catalyst dosage and volume ratio of lactic acid based DES to oil and sulfide type on the desulfurization rate of the simulated oil were investigated. The optimum reaction conditions were determined as follows: q reaction temperature of 70 ℃, a reaction time of 100 min,a n(H₂O₂)/n(DBT) of 6∶1, an ammonium molybdate dosage of 4 g/L and a volume ratio of DES to oil equalling 1∶10. Under the optimal reaction conditions, the desulfurization rates of the simulated oil of DBT, 4,6-dimethyldibenzothiophene and benzothiophene were 100%, 98% and 78%, respectively. After using for 5 times, the desulfurization rate of simulated oil by lactic acid based DES can still reach 95%, indicating the good reusability of DES.

Key words: deep eutectic solvents, ammonium molybdate, simulated oil, thiophene sulfides, desulfurization rate