Systems and methods for separation and extraction of heterocyclic compounds and polynuclear aromatic hydrocarbons from a hydrocarbon feedstock

A method of extracting 1-4 cycle heterocyclic compounds and 2-5 cycle polynuclear aromatic hydrocarbons from a hydrocarbon feedstock, the method comprising:

• providing a hydrocarbon feedstock containing crude oil fractions comprising 1-4 cycle heterocyclic compounds and 2-5 cycle polynuclear aromatic hydrocarbons;
• determining an A/R ratio and an asphaltene concentration of the hydrocarbon feedstock;
• treating the hydrocarbon feedstock based upon the determination of the A/R ratio and asphaltene concentration to form a treatable hydrocarbon feedstock comprising fractions with a boiling point range of greater than 360° C.;
• cracking the treatable hydrocarbon feedstock in a cracker to form a treated hydrocarbon feedstock comprising fractions having a boiling point range of 165° C. to 470° C.;
• fractionating the treated hydrocarbon feedstock into a first fractionated stream having a boiling point range of less than 165° C., a second fractionated stream having a boiling point range of 165° C. to 470° C., and a third fractionated stream having a boiling point range of greater than 470° C.;
• extracting at least one targeted portion of the 1-4 cycle heterocyclic compounds from the second fractionated stream with an aqueous solvent comprising an ionic liquid formed from pressurized carbon dioxide and water;
• transferring to a PAH extractor a 1-4 cycle heterocyclic compound-lean stream containing the 2-5 cycle polynuclear aromatic hydrocarbons after all targeted portions of the 1-4 cycle heterocyclic compounds have been extracted from the second fractionated stream;
• and
• extracting the 2-5 cycle polynuclear aromatic hydrocarbons from the heteroatom-lean stream in the PAH extractor with a solvent system comprising an aprotic solvent.