A Green Hybrid Extraction Process For Thiophene, Quinoline And Indole Recovery From Light Hydrocarbon Fractions

"Green" extraction technologies are fundamental to many processing plants in order to improve the deteriorating environmental situation in the world. This work presents a combination of two "green" extraction technologies: liquid extraction based on water-soluble polymers, as an environmentally attractive method for the isolation, separation and concentration of substances, and supercritical fluid extraction, as an environmentally safe method for the isolation of valuable components from aqueous polymer solutions. Polyvinylpyrrolydone 3500 (PVP-3500) has demonstrated high extraction ability for quinoline and indole with one-step extraction efficiency up to 82% and 94% respectively from solutions simulating light hydrocarbon fractions. Concomitant versatile research allowed building the dependences between quantitative quinoline and indole extraction characteristics and such process parameters as: the phases contact time, the extraction system composition, the initial concentration of nitrogen-containing compounds in n-hexane, the volume fraction of the extractant and the process temperature in the heterogeneous system PVP-3500 - n-hexane - water. It was found that PVP-3500 possesses weak extraction affinity for sulfur-containing compounds, which makes it promising for use in the separation of S- and N-containing heterocyclic compounds. In addition, we propose a new environmentally friendly approach for the purification of polymers used in the study based on the countercurrent extraction with supercritical carbon dioxide. Particularly, using the latter method instead of static supercritical purification mode leads to significant increase in quinoline and indole extraction efficiency from an aqueous solution of PVP-3500. (c) 2023 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.