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In order to test the effect of molecular sieves and ion-exchange resins on the separation of ethanol and water in the adsorption distillation column, a set of experimental apparatus was established and shown in Fig. 2. The column was composed of two sections, ( I) 30 mm (diameter) x 600 mm (height) and (II) 30 mm (diameter) * 600 mm (height). The first section was firstly filled with stainless steel ring-shape packing with the size of 3 mm width and 3 mm height, then filled with 3 A sphere-shape molecular sieves with the diameter of 4-6 mm, and finally filled with ion-exchange resins (the type is D072 Styrene-DVB composed of the anion RSO3" and the cation Na+.) with the diameter of 1.20 - 1.30 mm. The second section was always filled with stainless steel ring-shape packing with the size of 3 mm width and 3 mm height in both experiments. In the beginning the feed mixture entered into the bottom tin with 2500 ml. Then the batch distillation column started to run. In the experiment it was assumed that the bottom and top concentration was keep constant because the operation time wasn't too long and concentration change in the bottom tin was negligible.

The feed mixture

The top product

The first section

The second section

The bottom product

Fig. 2. The experimental apparatus used for separating ethanol and water by adsorption distillation.

The organic solvents, ethanol, was of analytical purity. Ethanol and 3 A molecular sieves were purchased from the Beijing Chemical Reagents Shop, Beijing, PRC. Ion-exchange resins were purchased from the Chemical Plant of Nankai University. Water was purified with ion-exchange resins. Composition analyses of the samples withdrawn from the top and bottom were done by a gas chromatography (type GC4000A) equipped with a thermal conductivity detector. Porapark Q was used as the fixed agent of the column packing, and hydrogen as the carrier gas. The column packing was 160 °C and the detector 160 °C. The data were dealt with by a BF9202 workstation. In terms of peak area of the components, the sample compositions could be deduced.

Under the infinite reflux condition, the experimental results are given in Table 2 where xi and X2 are molar fraction of ethanol and water in the liquid phase, respectively, and T is temperature (K). The fresh molecular sieves and ion-exchange resins are used and not replaced during the operation.

Table 2

The experimental results of adsorption distillation

Table 2

The experimental results of adsorption distillation

The top of the column

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