DMAC水溶液中乙酸的吸附分离过程研究

发布时间：2018-11-18 15:54

【摘要】：针对N,N-二甲基乙酰胺(N,N-dimethylacetamide,即DMAC)水溶液中低浓度乙酸的分离问题,本文采用大孔弱碱性阴离子交换树脂为吸附剂,在乙酸质量浓度为0.6%-6.0%的范围内进行了吸附平衡、动力学和固定床动态吸附的研究。经过树脂选型确定出D301G树脂作为溶液中乙酸的吸附剂,通过静态实验,研究了溶液中DMAC的含量对吸附结果的影响,以及D301G树脂对乙酸的吸附热力学和动力学过程。结果表明,DMAC的存在,降低了树脂的平衡吸附量,但D301G树脂对于处理低浓度的乙酸仍具有良好的吸附与再生性能；D301G树脂对乙酸的吸附符合Langmuir等温吸附方程,在此基础上,通过热力学分析得到吸附热力学参数△Gθ0, △Hθ0,△Sθ0说明该吸附过程为自发进行、放热、熵减小的过程；吸附动力学结果符合准二级动力学模型,颗粒扩散是树脂吸附乙酸速率的主要控制步骤。室温(298K)条件下,在自制离子交换柱中,研究了进料流速、进口浓度及树脂装填量对树脂动态吸附穿透曲线的影响。根据吸附平衡数据及吸附穿透曲线,计算得到动态吸附工程参数(传质系数和传质区高度),优化吸附工艺条件。研究发现,随着进料流速的增加,传质系数和传质区高度增大,传质阻力减小,但吸附穿透点的时间提前,综合考虑选择进料流速4 mL/min较为适宜;乙酸初始浓度和树脂装填量,应根据实际实验装置大小和操作要求而定。在上述实验的基础上,建立数学模型,对树脂固定床动态吸附乙酸的穿透曲线进行模拟。结果表明该数学模型计算得到的吸附穿透曲线和实验得到的穿透曲线基本吻合,而且该模型的建立也为估算穿透点的时间提供了一条方便可靠的方法。
[Abstract]:To solve the problem of separation of low concentration acetic acid from aqueous solution of NN- dimethylacetamide (DMAC), macroporous weakly basic anion exchange resin was used as adsorbent. In the range of 0.6 ~ 6.0% acetic acid concentration, the adsorption equilibrium, kinetics and dynamic adsorption of fixed bed were studied. D301G resin was selected as the adsorbent of acetic acid in solution. The influence of DMAC content in solution on the adsorption results and the thermodynamic and kinetic process of adsorption of acetic acid by D301G resin were studied by static experiments. The results showed that the existence of DMAC reduced the equilibrium adsorption capacity of the resin, but D301G resin still had good adsorption and regeneration properties for the treatment of low concentration acetic acid. The adsorption of acetic acid by D301G resin accords with Langmuir isothermal adsorption equation. On this basis, the adsorption thermodynamic parameters G 胃 0, H 胃 0 and S 胃 0 show that the adsorption process is spontaneous, exothermic and entropy decreasing. The results of adsorption kinetics are in accordance with the quasi-second-order kinetic model. Particle diffusion is the main control step of the adsorption rate of acetic acid by resin. At room temperature (298K), the effects of feed flow rate, inlet concentration and resin filling amount on the dynamic adsorption penetration curves of resin were studied in a self-made ion exchange column. According to the adsorption equilibrium data and the adsorption penetration curve, the dynamic adsorption engineering parameters (mass transfer coefficient and mass transfer region height) were calculated and the adsorption process conditions were optimized. It is found that the mass transfer coefficient and the height of mass transfer zone increase with the increase of feed flow rate, and the mass transfer resistance decreases, but the time of adsorption penetration point is advanced, so it is more appropriate to choose the feed flow rate for 4 mL/min. The initial concentration of acetic acid and the filling amount of resin should be determined according to the size and operation requirements of the actual experimental device. On the basis of the above experiments, a mathematical model was established to simulate the breakthrough curve of dynamic adsorption of acetic acid on the resin fixed bed. The results show that the adsorption penetration curve calculated by the mathematical model is in good agreement with the experimental penetration curve, and the establishment of the model provides a convenient and reliable method for estimating the time of penetration point.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：O647.3;TQ225.122

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