Separation of sulphur compounds from vacuum gas oil distillates by ligand exchange chromatography

For characterizing the sulphur components present in vacuum gas oil (VGO) distillates, it is essential to develop and standardize a procedure to separate the sulphur components present in the fraction before applying any techniques for structural elucidation. Ligand exchange chromatography (LEC) has been reported for the separation of sulphur compounds (SCs) from petroleum distillates and shale oil. Therefore, in the present study, the LEC technique was applied using four metals: Cu++, Ag+, Hg++, and Pd++. These metal salts (5 wt%) were impregnated onto grade-12 silica gel in aqueous phase or in dichloromethane. All of them were tested to form complexes with different types of SC in subfractions of VGO from Kuwaiti crude oils. The efficiency of the ions in separating the SCs, was in the order of PdCl2 (aqueous) <AgNO3 < HgCl2 < CuSO4 < PdCl2(dichloromethane). Palladium chloride impregnated over grade 12 silica gel in aqueous phase was very effective in separating the SCs from complex mixtures of aromatics. The methodology was optimized, and it was found that a 30: 1 ratio of the adsorbent to the sample was effective for the separation of SCs.