| Pharmaceutical production process usually generate many solvents. Some of these solvents are single solvent, but most of them are a mixture of different solvents. And these mixtures usually form azeotropic (e.g. a mixture of water and ethanol). It’s now a key problem for these azeotropic mixtures to be recovered and reused. Acetone and methanol are commonly used organic solvents in pharmaceuticals industry. However, there are byproducts containing a mixture of methanol and acetone. The boiling point of methanol and acetone are very similar. They can easily form azeotrope, which is very difficult to be separated using the general distillation method. Extractive distillation is the commonly used method to separate the azeotrope. However, the selection of extractant is very important in extractive distillation. This work is carried out according to the following items.1. Based on a bunch of literature, through comparison with screening, three commonly used extractants, monoethanolamine, N, N-Dimethylformamide (DMF), Dimethyl sulfoxide (DMSO), are selected as the extractants for the extractive distillation of acetone and methanol.2. Aspen simulations were carried out to study the extractive distillation of acetone and methanol using the above three solvents. The simulation parameters of the extractive distillation were obtained, such as the reflux ratio, the mass flow rate of the extractant, the extractant feed temperature, the position of the feed material etc. Simultaneously, the extractive distillation column vapor-liquid distribution, extractive distillation tower temperature distribution, and the distribution of extractive distillation tower vapor-liquid equilibrium constants are also studied by using simulation method. All these parameters are prepared for the pilot distillation experiments.3. Experiments were carried out in pilot extraction tower to collect the data of extraction separation with three extractants (monoethanolamine, DMF, DMSO). There are four variables in this process, including the reflux ratio, feed temperature of extractants, and the feed rate of the extractant and the mass fraction of the extractant. In this work, three of the four variables are fixed to measure the separation parameters of methanol and acetone. Determination of the mass fraction of the overhead of acetone with a reflux ratio, feed temperature of the extraction agent, the extraction agent, the mass fraction of the change, and the extractant feed rate is changed circumstances. The optimum operation conditions were obtained. 4. Based on the results from simulations and experiments, the best extractant is the DMF. And the optimal conditions are:the reflux ratio is2.3, the feed temperature of the extractant is25℃, the extractant feed composition is1, and the extractant flow rate is10ml/min. Three extraction solvent extraction efficiency of DMF> DMSO> monoethanolamine. The use of DMF as the extraction solvent can not only achieve good results, but the tower, tower reactor the temperature in the lower range, the smaller the power consumption, as described DMF acetone-methanol extractant is feasible system, which provides support for future industrialization. The experimental results with the simulation results do comparison aspen simulation results can be obtained in good agreement with the experimental values are not exactly the same figure for individual simulation and experimental trend is the case, you can follow through the vapor-liquid equilibrium experiments done to analyze whether the software because the aspen and NRTL parameter error factor between raw materials as a result.All the experimental results are in accordance with the Aspen simulations.Through the study of this article, it provides the theoretical basis of acetone methanol separation recycling reuse azeotropic system in the production process for traditional Chinese medicine. Also, it provides a reference for azeotrope separation recycling and reusing in other production process of traditional Chinese medicine. It can be used as a template or a new research idea. |
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