Batch rectificationof an aqueous solution of ethanol containing 0.3 wt%furfural was carried out in a glass laboratory packed tower or an Oldershaw-type column. The distillation curves of ethanol and furfural were obtained under several conditions. The curves of the minor component (furfural) were found to show a sharp peak. The ratio of mole fraction of furfural in distillate to that in charge goes up to over 160. With some assumptions, a set of equations governing the behavior of ethanol and a minor component has been derived from the mass balances around a still, a typical stage and a condenser.It is shown that the results of numerical calculation are similar in shape and magnitude to the observed distillation curves. IntroductionThe simple distillation of an aqueous solution of ethanol containing a minor component was studied by one of the authors and his coworker1>2), where the behavior of the minor components 1-butanol and furfural was made clear. It was shown that when the ethanol concentration is relatively small the minor component appears in distillate at a concentration several times that in the charge, but it drops gradually with decrease of ethanol concentration in the still as distillation proceeds. Whenremoval of the minor componentis desired, simple distillation is useless. In this paper, the batch rectification of an aqueous solution of ethanol containing a minute amount of furfural was studied with a view to separate the impurity and obtain pure alcohol. A glass laboratory distillation apparatus was employed, shown in Fig. 1. The still consisted of a 1-liter flask with three necks and was heated by a heating mantle.The following two fractionating columns were used:(1) A packed column, about 2cm in diameter by 60 cm high, packed with 7 mmglass herics, (2) An Oldershow-type column, 2.5 cm in diameter by about 100 cm high, 34 stages. Thermocouplesfor temperature measurementwere located at two points on the column. The column ® \j~©AutoTimer was woundwith asbestos string and a nicrome wire, which was to compensate for heat loss.Product vapor from the top was condensed and then split periodically into reflux and overhead product stream by a device which is shown in Fig. 1 The weight of each fraction was about 4 grams. The fractions were weighed exactly and analyzed. Densities of the samples were measured at 20°C.The concentration of furfural was determined by the aniline method described in the preceding paper2\ From density and furfural concentration, the concentration of ethanol was determined by a diagram of constant-density lines which had been made previously. The diagram is shown in Fig. 2. Experimental ResultsFour typical sets of distillation curves are shown in Fig. 3. The experimental conditions of these runs are represented in Table 1.In contrast with the case of simple distillation reported in the previous paper2}, an ethanol solution which was in relatively high concentration and contained little furfural was obtained in the early period of distillation.When the ethanol concentration in...
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