Study on transformation of sulfides in the process of deep hydrodesulfurization of diesel

The sulfides in diesel were analyzed by gas chromatography with a pulsed flame photometric detector,and the results show that two main types of sulfur compounds were found in diesel: benzothiophenes(BTs) and dibenzothiophenes(DBTs).The results show that BTs are easy to be removed and the sulfides are mostly DBTs when the total sulfur in hydrotreated diesel is below 500 μg/g.The hydrodesulfurization conversions for DBTs with different alkyl substituted are various in the following orders from easy to difficult: C1DBT,C2DBT,C3DBT,and the orders from easy to difficult for some individual sulfides are DBT,4-MDBT,2,4,6-TMDBT,4,6-DMDBT.The experiment results show that H2S in the hydrotreated diesel can be oxidized into elemental sulfur,which dissolves in diesel and affects the analytical result.The GC-PFPD can be used to analyze and identify sulfides and elemental sulfur effectively in the ultra low sulfur diesel(ULSD) with total sulfur as low as 520 μg/g,and the information is very helpful for the selection and optimization of the hydrotreating catalyst and technology.