| Di tert butyl bicarbonate(Boc-anhydride)is a new type of amino protective agent,which is widely used in the synthesis of medicine,biochemistry,food,cosmetics and other products.In the production process of this product,a large amount of n-hexanetert-butanol-tetrahydrofuran-water quaternary mixed waste solvent will be produced,which needs to be separated and recycled by effective process methods to realize the recycling of this part of resources.The mixture has many components of Binary Azeotropic phenomenon,and it is difficult to realize the complete separation of components in raw materials by traditional distillation method.Based on the summary and analysis of the existing relevant separation processes,the paper considers the purity,yield and energy consumption of the products,and determines that the process method of liquid-liquid extraction-pervaporation membrane separation-distillation is used to separate the mixture The n-hexane,tert-butanol and tetrahydrofuran were recovered by mixing the solvent.Water was firstly selected as the extractant,and the mixed solvent was treated by liquid-liquid extraction.The extraction phase was tert butyl alcohol,tetrahydrofuran and water,and the raffinate phase was n-hexane.The effects of stirring time,stirring speed and standing time on the extraction efficiency were analyzed by single factor experiment.Based on this,the effects of solvent ratio and extraction stages were comprehensively considered.The results showed that the stirring time was 40 min,stirring speed was 500 r/min,standing time was 40 min,solvent ratio was 2:1,and extraction stage was two.Under this condition,the solid phase could be extracted by cross flow liquid-liquid extraction The n-hexane in the system is basically separated,and the n-hexane content in the raffinate is more than 99%,which realizes the effective recovery of n-hexane.Aiming at the ternary system of tert butyl alcohol tetrahydrofuran water in the extraction phase,the extraction phase was pretreated by flash evaporation process,then the residual water was removed by membrane separation,and finally the tert butyl alcohol and tetrahydrofuran were refined and separated by distillation process.That is,the extract phase after flash evaporation pretreatment uses Na A molecular sieve membrane to separate the remaining water by pervaporation.The experimental results show that the best dehydration effect is achieved when the separation temperature is set at 60 ? and the vacuum degree on the permeate side is 0.07 MPa.The water content in tert butyl alcohol tetrahydrofuran binary solvent can be reduced to below 0.01%.The dehydrated tert butyl alcohol tetrahydrofuran mixed solvent was separated by continuous distillation.On the basis of vapor-liquid equilibrium determination and correlation,the process parameters of distillation process were optimized by simulation combined with experimental process.The experimental results showed that Under the condition that the number of theoretical plates is 40,the reflux ratio is 5,and the raw material feed position is the 14 th block,the tetrahydrofuran content at the top of the tower reaches 99.02%,and the content of tert-butanol in the bottom of the tower reaches99.10%.In this paper,the liquid-liquid extraction-pervaporation membrane separationdistillation method was used to separate the waste solvent of n-hexane-tert-butanoltetrahydrofuran-water.Finally,99.12% n-hexane,99.02% tetrahydrofuran and 99.10%tert-butanol were obtained.All of the above achieved the standard of enterprise recycling.The separated water reached the enterprise takeover standard,and realized the recycling benefit of the waste solvent Use.The work in this paper provides technical reference for the treatment and recycling of the waste solvent. |
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