Evaluation of Four Inexpensive Extractants for Pyridine Separation from <i>n</i> -Heptane at 303.2 K: Liquid–Liquid Equilibrium and Thermodynamic Modeling

In order to reduce the impact of nitrogen-containing compounds in oil products on the environment, this paper selected n-heptane as the oil product model and pyridine as the nitrogen-containing compound. Four inexpensive extractants (furfuryl alcohol, 1,4-butanediol, N,N-dimethylacetamide, and dimethyl sulfoxide) were selected as the extractants to separate pyridine from the oil model at 303.2 K, and the liquid–liquid equilibrium (LLE) data were measured. The partition coefficients (D) and separation coefficients (S) of the extractants were calculated and used to evaluate the extractants. Based on the LLE data, correlations were performed using NRTL and UNIQUAC models, and the interaction parameters of the corresponding optimization models were obtained. The root-mean-square deviation (RMSD) values of the NRTL and UNIQUAC models were 0.98% and 1.09%, respectively. The GUI-MATLAB tool was selected to evaluate the accuracy of the binary interaction parameter regression by a Gibbs energy topology analysis. To probe the underlying mechanism of the extraction process between the extractants and pyridine, the σ-profile was used to analyze the interaction patterns between the extractants and pyridine. Given their high extraction efficiency, the studied extractants can be considered as potential extractants for extractive denitrification processes.