CaY分子筛对乙二醇和1,2-丁二醇吸附分离性能的研究

Study on adsorptive separation property of CaY zeolite for ethylene glycol and 1,2-butanediol

利用装填有CaY分子筛的固定床对乙二醇和1,2-丁二醇吸附分离进行研究,从水、甲醇、乙醇和正丙醇中筛选出正丙醇为最佳洗脱溶剂,并探究了进样流速(0.4,0.8,1.2 mL/min)及操作温度(298,318,338 K)对穿透曲线的影响,对测得的穿透曲线采用Modified Dose-Response模型进行拟合,与实验结果能够高度吻合。并采用巨正则蒙特卡洛(GCMC)研究混合醇在CaY分子筛内部的竞争吸附,模拟了乙二醇和1,2-丁二醇在CaY分子筛内部的吸附位点,发现其吸附位点几乎重合,且CaY分子筛对乙二醇的吸附量要大于1,2-丁二醇,此模拟结果为实验结果提供了微观理论支撑。

Ethylene glycol is an important petrochemical basic organic raw material, mainly used in the production of polyester, antifreeze, membrane, etc. China has abundant coal resources, which makes coal to ethylene glycol technology increasingly valued. As more and more coal to ethylene glycol plants is successfully running in China, the separation problem of ethylene glycol and 1,2-butanediol is urgently waiting to be solved. Selective adsorption is considered the most promising method because of its environmentally friendly characteristic and low cost. In this work, a fixed-bed column was used to separate ethylene glycol and 1, 2-butanediol by using CaY zeolite as an absorbent, n-propanol was selected as the best eluent. In the fixed-bed column experiments, breakthrough curves were obtained and the dynamic adsorption characteristics were analyzed through breakthrough curves. The effect of operational conditions, such as flow rate and operating temperature were examined. The adsorption selectivity of ethylene glycol to 1,2-butanediol reached 1.90 at the temperature of 298 K and the flow rate of 0.8 mL/min. It can be found that the adsorption capacity of EG was much higher than 1,2-butanediol. The experiment results indicated that the breakthrough time and adsorption amount both decreased with increase of the flow rate and operating temperature. Modified Dose-Response models gave satisfactory fits to the experimental data of breakthrough curves in a fixed-bed column. At last, the adsorption sites of ethylene glycol and 1,2-butanediol were determined by Grand Canonical Monte Carlo(GCMC) simulation. It was found that the adsorption sites of ethylene and 1,2-butanediol almost overlapped, which meant ethylene glycol and 1, 2-butanediol were competitive adsorptions in CaY zeolite.Moreover, the adsorption capacity of ethylene glycol was greater than 1,2-butanediol, which was consistent with the experiment result. The simulation result provided microscopic theoretical support for the experimental results. From these studies, CaY zeolite had the potential to be used as an effective absorbent for the adsorption and separation of ethylene and 1,2-butanediol.