Effective recovery of heavy oil from tank bottom sludge and isolation of paraffins from the heavy oil

Tank bottom sludge (TBS), consisting of heavy oil (HO), sediment, and water, is one of liquid–solid wastes from petroleum production. Effective separation of HO from TBS and its isolation for value-added products are of great importance for avoiding the pollution from TBS and creating economic benefits. In this work, a two-step solvent extraction strategy is proposed to extract HO from TBS and enrich refined paraffin (RP) from HO. The effects of solvent type, extraction time, extraction times, and solvent volume on the HO extraction and RP enrichment were examined. The results show that more than 95% of HO was extracted using isometric carbon disulfide/acetone mixed solvent at room temperature and petroleum ether/acetonitrile (PE/AN) proved to be effective for enriching RP. The mechanism for the extraction with PE/AN is revealed by calculating the nonbonded interaction energy between PE/AN and selects model compounds at the molecular level. Independent gradient model isosurface and scatter plot prove the wide existence of van der Waals forces and X-H/Y···π bonds (X represents >CH or –O and Y denotes a cation or anion) between PE/AN and a model compound through molecular dynamics simulation. This work presents an environmentally friendly and feasible strategy for the clean production of RP from TBS.