Study On The Separation Of Octanol-Nonanol-Dodecane-Tridecane Mixture

The components of Fischer-Tropsch synthesis products are complex,most of which are n-alkanes and primary alcohols.Primary alcohols especially higher alcohols have high commercial value,which are widely used as raw materials of fine chemical products.Due to the azeotropy between n-alkanes and alcohols,it is difficult to separate by normal distillation,while extraction is considerd as an effective and economical separate method.In this paper,octanol-nonanol-dedocane-tridecane mixture was seperated by combination of extraction and distrillation,and a process of treating 2000 t/a octanol-nonanol-dodecane-tridecane mixture was designed and optimized.In this paper,firstly,the LLE data of ethanol-octanol-dodecane-water,ethanol-octanol-tridecane-water,ethanol-nonanol-dodecane-water,ethanol-nonanol-tridecane-water at 293.15K,298.15K and 303.15K under atmospheric pressure were obtained experimentally.The NRTL equation was used to correlate the LLE data and the binary interaction parameters were acquired to predict the LLE data of ethanol-octanol-nonanol-dodecane-tridecane-water system.The predicted data agreed with the experimental data well,which indicated the binary interaction parameters acquired from LLE data of four quaternary systems could be used to predict LLE data of six-component system.The data of six-component system were evaluated by distribution coefficient and selectivity,which showed that 75%ethanol aqueous solution was suitable for separating octanol and nonanol from octanol-nonanol-dodecane-tridecane mixture.298.15K was the suitable temperature for extraction operation.Secondly,n-hexadacane was selected as reverse-extraction solvent.The LLE data of ethanol-octanol-nonanol-dodecane-tridecane-water-hexcadacane at 298.15K,303.15K and 308.15K under atomosphic pressure were obtained experimentally,and the LLE data was regressed by NRTL model.Comparing with default parameters in Aspen Plus database,the regressed parameters were more accurate.The results showed that the regressed parameters could be used in separation process simulation and optimization.By comparing distribution coefficient and selectivity at different temperatures,and considering higher temperature would give a higher mass transfer rate.Comprehensively,298.15 K was the suitable temperatureFinally,a separation process of treating 2000t/a octanol-nonanol-dodecane-tridecane mixture was designed and optimized by Aspen Plus.75%ethanol aqueous solution was selected as extractant,the raffinate phase was purified and 99.8%dodecane-tridecane product was obtained.Extract phase was reverse-extracted by hexcadacane,and the 99.5%octanol-nonanol product was obtained by a series of distillation operation.Extractant and reverse-extraction solvent were recycled.