Research On The Recovery And Purification Of DMAC

As an important industrial solvent, N,N-dimethylacetamide(DMAC) is widely used in the manufacture of resins, rubbers and fibers for its strong ability of dissolution for many compounds. With the advancement of production process, a stricter quality requirement of dimethylacetamide is taken by consumers, especially the moisture and chrominance of the product. Hence, the high-quality DMAC enjoys a promising market. The process of vacuum distillation and extractive distillation for the recovery and purification of DMAC was studied, aiming to reduce production cost, protect environment and save resources. The feasibility and conditions of this technology were investigated, trying to control the thermal decomposition and hydrolysis into dimethylamine as a result of long-time heat in the practical production.Firstly, the data of both peak area and composition of DMAC-H2O were measured by GC-102M and regressed into correlations. Then, vapor-liquid equilibrium data for binary system of DMAC-H2O were measured at35.0kPa with a modified Ellis equilibrium still and GC-102M. The experimental data were checked by Herington method to satisfy the examination of the thermodynamic consistencies. The activity coefficients were correlated with two models, Van Laar and Wilson, in order to achieve the model parameters, providing the basic data for the distillation design of DMAC-H2O. Through comparison, both models were suitable for the binary system.Secondly, VLE data for binary systems of ethanol-acetic acid, acetic acid-water and acetic acid-DMAC were collected in this paper. The experimental data were regressed by Aspen Plus with Wilson model. Because of little deviation between estimated and experimental data, it was proved that Wilson was suitable for the whole process.Thirdly, according to the practical production problem, this paper provided the recovery process with two technical approaches:vacuum distillation and extractive distillation. Each column in the process was simulated and the optimized operation parameters were achieved with chemical software of Aspen Plus, such as column pressure, reflux ratio, total column stages and feed stage. Meanwhile, their effects on mass recovery and mass fraction of DMAC were also analysed in this paper.Based on the results of mono-column parameters, the simulation for refining tower in stream2was optimized by Aspen Plus, considering three factors:flow rate of water, energy consumption and mass recovery of DMAC. Through simulation and calculation, the optimized parameters of the whole process were determined, not only to meet the requirement of the separation, but also to save resouces and to decreace the production cost, providing the reliable process data for the factory.