Removal of Refractive Sulfur and Aromatic Compounds from Straight-Run, Fluidized Catalytic Cracking, and Coker Gas Oil Using <i>N</i>-Methyl-2-pyrrolidone in Batch and Packed-Bed Extractors

Abstract

In the present study, removal of sulfur and aromatic compounds from straight-run gas oil (SRGO), light cycle oil (LCO), coker gas oil (CGO), and their mixture, termed as mixed gas oil (MGO), was studied using N-methyl-2-pyrrolidone (NMP) solvent in a single-stage batch extractor and continuous countercurrent packed-bed extraction column. The effect of the extraction temperature (TE), solvent/feed ratio (S/F), and antisolvent concentration (Wc) on the degree of sulfur removal (Dsr), yield of extracted gas oil (Y%), and performance factor (Pf,α), which combines both Dsr and yield, was studied in a single-stage batch extractor. After optimization of the operating conditions for SRGO, LCO, and CGO in a single-stage batch extractor, studies on MGO were carried out in both a single-stage batch extractor and continuous countercurrent packed bed at estimated optimized values of TE, S/F, and Wc. Issues related to the loss of valuable hydrocarbons with extract and value addition to extract hydrocarbon have been addressed in the present study by performing quantitative evaluation of distillate products from processing of the pseudo-raffinate (generated from the extract phase using antisolvent) in hydrocracker and fluidized catalytic cracking (FCC) processes. The present study also demonstrates the approach for improving the quality of extract as a carbon black feedstock (CBFS). The benefits and befitting of disposal of extract hydrocarbon in a delayed coker as a blending stream with vacuum residue (VR) is also discussed in detail.