Study of the Salt-Adding Extractive Distillation of Cyclopentane-2,2-dimethylbutane Using Composite Extract for the Production of High-Pure Cyclopentane

Abstract

Cyclopentane is an important organic raw material for the production of refrigerants and foaming agents. The relative volatilities of 2,2-dimethylbutane (DMB) and cyclopentane were determined in the presence of four extractants including dimethyl formamide (DMF, 100 wt %), N-methyl pyrrolidone (NMP, 100 wt %), DMF (80 wt %) + NMP (20 wt %), and DMF (79 wt %) + NMP (19 wt %) + sodium acetate (AcONa, 2 wt %). The results showed that the complex solvent containing AcONa provided a good separation effect, and the accuracy of the relative volatility determination was verified by the extractive distillation experiment. The process conditions for separating DMB and cyclopentane by extractive distillation with DMF (79 wt %) + NMP (19 wt %) + AcONa (2 wt %) as the extractant were systematically discussed. At the mass percentage of AcONa in DMF and NMP of ~2.0–2.5 wt %, mass ratio of solvent of about 6, the number of theoretical plates of about 30, the reflux ratio of about 3, and the solvent feed temperature of about 50°C, the composite extract (DMF (79 wt %) + NMP (19 wt %) + AcONa (2 wt %)) exhibited a better separation efficiency of the cyclopentane–DMB azeotropic system. According to the calculations of the process simulation, under the same operating conditions, the reboiler energy consumption could be reduced by 25.1% and the energy consumption for cooling could be reduced by 28.4% compared to that for the DMF solvent only.