Study On Separation Of Isopropanol-water Azeotrope Using The Coupling Process Of Biomass-based Fixed-bed Adsorption And Distillation

Synthesized crude isopropanol is inevitably accompanied with water in form of isopropanol aqueous solution. The popular way to obtain pure isopropanol product is to separate the solution by azeotropic distillation, including at least a third substance.In this paper, a new coupling process of biomass-based fixed-bed adsorption and normal distillation is assembled for isopropanol dehydration. The first distillation column, researched by computational simulation, drives the mixture to its azeotropic point. Then the fixed-bed adsorber with compound starch adsorbent ZSG-1 to get anhydrous product or just helps to surpass the azeotropic point to facilitate another distillation to obtain pure product. That is, a new process of effectiveness, feasibility and low energy consumption can be developed by combing the fixed-bed adsorption and distillation. Lab research focused on the adsorption process.Inverse gas phase chromatography was firstly used to study the adsorption selectivity of ZSG-1 to water and isopropanol in this study. The internal structure, pore size distribution and surface area were characterized and calculated.The study about adsorption of isopropanol-water in the fixed-bed by ZSG-1 was made by the method of orthogonal experiments, and the optimum adsorption conditions were fixed through the breakthrough curve under different bed depth, bed temperatures and kettle temperatures.The adsorption module was established after the regression of data and the selection of right adsorption rate formula under the optimum adsorption conditions. A new process of low energy consumption was then got by the method of software simulation through combing adsorption and distillation module and its energy consumption was estimated.The results showed that the retention time of water is significantly longer than that of isopropanol and so is adsorption free energy. These features qualify the starch adsorbent ZSG-1 to get anhydrous isopropanol. As the column temperature gets higher, the retention time of water decreases faster than that of isopropanol. It can be inferred that lower temperature is more favorable for adsorption. The adsorption heat of water is -55.73kJ/mol, which indicates that the adsorption of ZSG-1 to water is physical adsorption. The optimum adsorption conditions for adsorption in the fixed-bed are as follows: the water bath temperature is 89℃, the bed temperature is 88℃and the bed height is 26cm. The impact of various factors on the concentration of isopropanol is different, which is water bath temperature> bed depth > bed temperature.Bangham adsorption module was selected to describe the process and the coupling process of biomass-based fixed-bed adsorption and distillation was simulated. Its energy consumption was estimated at 8.4×106 J/kg isopropanol.