Recycling Of Sulfolane Wastewater Of Polyarylether Production

The aprotic polar solvent sulfolane is a common solvent for the synthesis of high temperature resistant high performance polyarylether resin.Polyarylene resin synthesis equipment will produce a large amount of low-concentration sulfolane wastewater.With the increasing emphasis on environmental protection in our country,stricter environmental protection regulations have been introduced.At present,the industry often uses four-effect evaporation process,which cannot make the sulfolane wastewater meet the discharge standard,and is very energy-intensive.In this paper,1,2-dichloroethane,the solvent used in the synthesis of the special monomer DHPZ of polyarylethers,was selected as the extractant.And the sulfolane wastewater was treated by the extraction-distillation hybrid process to realize the recycling of sulfolane wastewater.Based on the determination of the liquid-liquid equilibrium data of the water-1,2-dichloroethane-sulfolane ternary system and the correlation of the thermodynamic model,the extraction-distillation hybrid process and the extraction-(four-effect evaporation)hybrid process were simulated and optimized,and compared with the four-effect evaporation process.First,the equilibrium kettle method was used to measure the liquid-liquid equilibrium data of the water-1,2-dichloroethane-sulfolane ternary system at 288.15 K,298.15 K,and308.15 K under atmospheric pressure.It was found that the water-1,2-dichloroethane-sulfolane ternary system exhibit the Treybal’s type I phase behavior.The values of the distribution coefficient(D)and selectivity(S)decrease with the increase of sulfolane concentration and temperature.The values of S in all cases are much greater than 1.0,which confirms that 1,2-dichloroethane is a feasible extractant for the separation of sulfolane from water.The Othmer-Tobias,Hand,and Bachman equations were utilized to verify the reliability and consistency of the experimental LLE data.The values of the determination coefficient(R~2)are all greater than 0.9981,which indicts that the LLE data measured herein are reliable.Secondly,the NRTL(nonrandom two-liquid)and UNIQUAC(universal quasi-chemical)model were utilized to correlate the experimental LLE data,and the binary interaction parameters of the two thermodynamic models and the calculated values of liquid-liquid equilibrium were obtained.The root mean square deviation(RMSD)are less than 0.0092,which indicates that the NRTL and UNIQUAC models fit successfully the experimental LLE data.The GUI-MATLAB software was used to verify the consistency of the binary interaction parameters of the NRTL model and the UNIQUAC model,which provided a basis for simulation calculation of process.Finally,Aspen Plus V8.4 was used to simulate and optimize the extraction-distillation hybrid process and the extraction-(four-effect evaporation)hybrid process.Compared with the four-effect evaporation process,using 1,2-dichloroethane as the extractant,the heat load of the extraction-distillation hybrid process is reduced by 17%,the mass concentration of sulfolane in the raffinate phase is reduced to 43.24 mg/L,and the purity of the recovered sulfolane reaches 96.44%.Both sulfolane and water can be recycled,which can achieve"zero discharge".In summary,extraction-distillation hybrid process is more suitable for treating sulfolane wastewater.