Study on the Process and Mechanism of Removing Chloride Ions from Desulfurization Ionic Liquid by Modified Ion Exchange Resin

In the ionic liquid desulfurization system, the repeated circulation and regeneration of the ionic liquid lead to the continuous accumulation of Cl^-, resulting in decreased desulfurization performance, increased ionic liquid loss, and exacerbated equipment corrosion. Therefore, the effective removal of Cl^- from the desulfurization of ionic liquids is of great significance. This paper discusses the use of modified 717 resin for the removal of Cl^- from a desulfurization ionic liquid. First, the adsorption equilibrium, adsorption thermodynamics, and adsorption kinetics of the modified 717 resin for Cl^- were studied. The adsorption isotherm conforms to the Langmuir model, with an adsorption enthalpy of 1.971 kJ mol^-1, indicating that the process is a monolayer endothermic reaction. The adsorption kinetics follow a pseudo-second-order kinetic model, suggesting that the adsorption rate is controlled by chemical adsorption. Second, through dynamic adsorption experiments, it was determined that the optimal process parameters for Cl^- removal were: liquid flow rate of 2 mL/min, bed height of 10 cm, initial Cl^- concentration of 2300 mg/L, and reaction temperature of 45 °C. The dynamic behavior of the modified 717 resin in adsorbing Cl^- conforms to the Thomas model and the Yoon-Nelson model. Then, the equilibrium adsorption capacity of Cl^- of the modified 717 resin decreased by only 1.42 mg/g after five regeneration experiments, indicating that the resin has good renewability. Finally, the modified 717 resin removes Cl^- from the actual desulfurization ionic liquid with good results. This study provides a theoretical basis for the industrial application of ion exchange resins for the removal of Cl^- from desulfurization ionic liquids.