Determination And Correlation Of Liquid-Liquid Equilibrium Data For The Water-Dichloromethane-N,N-Dimethylacetamide-Sodium Carbonate System

N, N- dimethylacetamide, is a good industrial solvent. Because of its good solubility,high thermal stability and chemical stability, nothydrolysis and so on of the many advantages, it is widely used in industry. In organic synthesis, dimethylacetamide, as an excellent catalyst, can accelerate the reaction of cyclization, halides, cyanide, alkylation and dehydrogenationreaction, and improve the yield of the main product. In the preparation of pharmaceutical intermediates, dimethylacetamide, as an important pharmaceutical raw material, is widely be used in amoxicillin and cephalosporins drug manufacturing.Dimethylacetamide, as a solvent or co-catalyst, compared with conventional solvents, can improve the quality and yield of products. In polymer materials synthesis,dimethylacetamide is widely used in producing a polyimide film, a soluble polyimide, a polyimide-FEP composite film, polyimide(Al) film and so on.By measuring the distribution ratios of several low-boiling extraction agent(dichloromethane, chloroform, isopropyl ether, trichlorethylene) of DMAC, as a result,larger distribution ratios was obtained by using dichloromethane and chloroform. In order not to introduce impurities, we choose dichloromethane as the extractant to recovery DMAC. In order to reach the purpose of quick analysis, an ultraviolet absorption spectrophotometry for determining DMAC at wave length 198 nm was established.Correlation between the absorbency and composition of the binary solution is reported: A = 0.09515 C + 0.0286.By studying the effects of various factors on the extraction equilibrium, we chose to add alkali pretreatment to the waste liquids, then add extraction agent to extract and recovery the DMAC. In order to obtain basic data for further extraction of N,N-Dimethylacetamide from the waste liquor, the liquid-liquid equilibrium(LLE) data for the quaternary system water + N,N-Dimethylacetamide + dichloromethane + sodium carbonate were determined at(298.15 and 308.15) K and atmospheric pressure. The solubility data of ternary system water + N,N-Dimethylacetamide + dichloromethane were determined by using the cloud point titration method. The tie-lines had been drawn from the conjugate phase composition of the ternary system. The reliability of the measured LLE data was tested by the Othmer-Tobias, Bachman and Hand equation. As a result, the equation fits the experimental LLE data well. The experimental LLE data were correlated by using NRTL and UNIQUAC models for the activity coefficient calculation. Both models were able to correlate the experimental data well, with the maximum values of root mean square deviation(rmsd) of 1.01% and 0.99% for NRTL and UNIQUAC, respectively.Compare to use dichloromethane as the extractant merely, the selectivity and distribution ratio evaluated for the immiscible region was improved by using the composite extractant.The result shows that: at room temperature 25 to 35℃, adopting dichloromethane to extract and recover DMAC with alkali pretreatment, when waste and extraction solvent volume ratio of 1:l, added to the alkali amount from 2 to 5%, the distribution ratio and selectivity of solute DMAC has been significantly improved.