{"title":"Liquid–Liquid Equilibrium Data and Mechanism for Separating Thiophene from Heptane Using Mixed Solvents","authors":"Chong Yang*, Shimin Xu, Yuyao Xie, Yepeng Xiao, Lihua Cheng and Xinping Ouyang, ","doi":"10.1021/acs.jced.4c00154","DOIUrl":null,"url":null,"abstract":"<p >Solvent extraction is a promising method for removing organic sulfides from fuel oils in refineries. However, selecting an appropriate extractant requires a fundamental understanding of liquid–liquid equilibria. In this study, we collected liquid–liquid equilibrium (LLE) data for ternary heptane + thiophene + solvent systems at 298.2 K and 101.3 kPa. The extraction capabilities of the selected solvents (ethylene glycol (EG), <i>N</i>-formylmorpholine, 1,3-propanediol, 1,4-butanediol, 1,2-propanediol, <i>N</i>-methyl-2-pyrrolidone (NMP), <i>N</i>,<i>N</i>-dimethylacetamide, and benzyl alcohol) for separating heptane and thiophene were assessed based on the distribution constant (<i>D</i>) and separation factor (<i>S</i>). NMP exhibited the highest <i>D</i> value, whereas EG exhibited the lowest. In contrast, the EG had the highest <i>S</i> value. Therefore, to balance <i>D</i> and <i>S</i> simultaneously, mixtures of EG and NMP at different molar ratios were used as extractants. Molecular-level investigation into the separation mechanism was conducted via molecular dynamics simulations and density functional theory calculations. The enhanced <i>S</i> value of EG was attributed to a significant difference in its interaction energies with thiophene and heptane, whereas the enhanced <i>D</i> value of NMP resulted from a more negative solvation-free energy upon binding thiophene. Finally, a comparison of the thermodynamic models showed that the nonrandom two-liquid (NRTL) model and the universal quasichemical (UNIQUAC) model were equally suitable for correlating the experimental data for the ternary and quaternary heptane + thiophene + solvent systems; the root-mean-square deviation (RMSD) values for the NRTL model were all <1%, whereas the maximum RMSD value for the UNIQUAC model was 1.57%. The obtained liquid–liquid equilibrium data and mechanistic insights can aid in improving extractive desulfurization using conventional organic solvents toward the efficient, low-cost, and simple production of clean fuel oils with ultralow sulfur contents.</p>","PeriodicalId":42,"journal":{"name":"Journal of Chemical & Engineering Data","volume":null,"pages":null},"PeriodicalIF":2.0000,"publicationDate":"2024-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Chemical & Engineering Data","FirstCategoryId":"1","ListUrlMain":"https://pubs.acs.org/doi/10.1021/acs.jced.4c00154","RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"CHEMISTRY, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
Solvent extraction is a promising method for removing organic sulfides from fuel oils in refineries. However, selecting an appropriate extractant requires a fundamental understanding of liquid–liquid equilibria. In this study, we collected liquid–liquid equilibrium (LLE) data for ternary heptane + thiophene + solvent systems at 298.2 K and 101.3 kPa. The extraction capabilities of the selected solvents (ethylene glycol (EG), N-formylmorpholine, 1,3-propanediol, 1,4-butanediol, 1,2-propanediol, N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide, and benzyl alcohol) for separating heptane and thiophene were assessed based on the distribution constant (D) and separation factor (S). NMP exhibited the highest D value, whereas EG exhibited the lowest. In contrast, the EG had the highest S value. Therefore, to balance D and S simultaneously, mixtures of EG and NMP at different molar ratios were used as extractants. Molecular-level investigation into the separation mechanism was conducted via molecular dynamics simulations and density functional theory calculations. The enhanced S value of EG was attributed to a significant difference in its interaction energies with thiophene and heptane, whereas the enhanced D value of NMP resulted from a more negative solvation-free energy upon binding thiophene. Finally, a comparison of the thermodynamic models showed that the nonrandom two-liquid (NRTL) model and the universal quasichemical (UNIQUAC) model were equally suitable for correlating the experimental data for the ternary and quaternary heptane + thiophene + solvent systems; the root-mean-square deviation (RMSD) values for the NRTL model were all <1%, whereas the maximum RMSD value for the UNIQUAC model was 1.57%. The obtained liquid–liquid equilibrium data and mechanistic insights can aid in improving extractive desulfurization using conventional organic solvents toward the efficient, low-cost, and simple production of clean fuel oils with ultralow sulfur contents.
期刊介绍:
The Journal of Chemical & Engineering Data is a monthly journal devoted to the publication of data obtained from both experiment and computation, which are viewed as complementary. It is the only American Chemical Society journal primarily concerned with articles containing data on the phase behavior and the physical, thermodynamic, and transport properties of well-defined materials, including complex mixtures of known compositions. While environmental and biological samples are of interest, their compositions must be known and reproducible. As a result, adsorption on natural product materials does not generally fit within the scope of Journal of Chemical & Engineering Data.