How to select ionic liquids as extracting agents systematically: a special case study for extractive denitrification processes

Shurong Gao; Jiaxin Jin; Masroor Abro; Ruozhen Song; Miao He; Xiaochun Chen

doi:10.1039/d0ra09316e

How to select ionic liquids as extracting agents systematically: a special case study for extractive denitrification processes

RSC Adv. 2020 Dec 24;11(2):700-710. doi: 10.1039/d0ra09316e.

Authors

Shurong Gao^{1

2

3}, Jiaxin Jin^{1

2}, Masroor Abro³, Ruozhen Song³, Miao He⁴, Xiaochun Chen³

Affiliations

¹ State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University Beijing 102206 China gaoshurong@ncepu.edu.cn +86-10-6443-3570 +86-10-6443-3570.
² Research Center of Engineering Thermophysics, North China Electric Power University Beijing 102206 China.
³ Beijing Key Laboratory of Membrane Science and Technology, College of Chemical Engineering, Beijing University of Chemical Technology Beijing 100029 PR China chenxc@mail.buct.edu.cn.
⁴ Office of Laboratory Safety Administration, Beijing University of Technology Beijing 100124 China.

Abstract

Extractive denitrification (EDN) of shale oil using ionic liquids (ILs) as the extracting agent has good industrial prospects. In such processes, ILs with higher selectivity to N-compounds and lower solubility in shale oil are desired to improve the EDN efficiency, and reduce the loss of ILs and the contamination of shale oil. In the present study, we employed COSMO-RS to calculate the selectivity of 70 ILs to the typical N-compounds (pyridine, quinoline and indole). The influence of the IL structural characteristics, composition of shale oil and properties of N-compounds are investigated from a micro-level view with the σ-surface and σ-profile. The selectivity strongly depends on anionic species and it is greatly influenced by hydrogen bonding (HB) and π-π interaction between N-compounds and ILs. ILs composed of [H₂PO₄]^- and [MeSO₃]^- with larger HB donor energy show higher selectivity to the basic N-compounds, while ILs composed of [Ac]^- with larger π-electron cloud density show higher selectivity to the non-basic N-compounds. Anions with stronger polarity have lower solubility in shale oil. Moreover, experimental determinations of EDN indicated that [C₄py][H₂PO₄]/[C₄mim][H₂PO₄] and [C₂mim][Ac]/[C₂py][Ac] have good EDN performance for quinoline/pyridine with efficiency of 100% and for indole with efficiency of 91%, respectively. This work presents a theoretical basis to design and select ILs having higher selectivity for N-compounds and lower solubility in shale oil for use in denitrification.