Study of aromatic extraction from light cycle oil from the viewpoint of industrial applications

Abstract

Light cycle oil (LCO) is a significant products of fluid catalytic cracking (FCC) process in refineries. Increasing the output of high-value chemicals from LCO is an important step towards achieving ‘dual carbon’ targets. Separating aromatic and non-aromatic components in LCO is crucial to producing valuable products. Extraction is a promising process for separating these components based on the principle of “polar similarity and solubility”. From the perspective of industrial applications, this study explores the development and application of novel functionalized extractants to produce valuable products. Ionic liquids (ILs) with alkyl-substituted imidazoles [CnMIM]+ and alkyl-substituted pyridines [CnMPy]+ as cations and tetrafluoroborate [BF4]− and hexafluorophosphate [PF6]− as anions were used. The effects of extraction temperature, IL-oil ratio, number of extraction stages, and reusability were systematically investigated. In addition, the basic physical properties data of ILs and residues in oil were studied in detail. The suitability of ionic liquids for industrial applications was evaluated based on their solubility with hydrocarbons, physical and chemical properties, selectivity for aromatics, and residues in oil. Following a thorough examination of the performance of ionic liquids for the extraction of aromatics from LCO, [C6MIM][PF6] was identified as the most suitable extractant. A multi-stage countercurrent extraction process was established and the conditions systematically studied. The results demonstrate that the aromatic content of the extracted oil is greater than 95 wt%, which can be utilized for producing BTX products. Meanwhile, the aromatic content of the raffinate oil is less than 10 wt%, which can function as a clean diesel blending component or as steam cracking feedstocks. This study has successfully promoted the industrial application of functionalized ionic liquids for the LCO dearomatization process and provided an essential reference for developing new functionalized extraction solvents.