Resumo:
Ethanol has been proposed for many years as an alternative substitute to petrochemical processes. It can be produced from renewable resources such as sugar of cane. However, the product of fermentation is a dilute solution of less than 10% of ethanol in water. Thus, the development of the efficient separation processes to remove water from ethanol are important. In this work, an investigation was carried out on ethanol-water separation, in the gas phase, employing the hydrophilic graft copolymer poly (propylene-graft-methylmethacrylate) (PP-G-MMA) as adsorbent. The sorption behavior of water and ethanol on PP-G-MMA has been investigated in relation to the adsorptive separation of water from ethanol. The adsorption isotherms of PP-G-MMA/water, PP-G-MMA/EtOH and PP-G-MMA/EtOH-water were evaluated using Fick law’s. From the water-ethanol sorption data the Arrhenius activation parameter (Ea) was determined. The activation parameter was found to be dependent of the ethanol concentration in the binary mixture. The experimental results showed that ethanol as well water can adsorb on PP-G-MMA graft copolymer. The adsorption rate of ethanol, however, is much slower than that of water. This suggest that the selective removal of water from ethanol vapor in a packed-bed adsober is likely a rate dependent, not a equilibrium-dependent processes. This interpretation is supported by a relatively greater affinity of PP-G-MMA for water, which is estimated with the δs and δp solubility parameters of the solvent and polymer, respectively. The proposed mechanism considers a particular orientation of ethanol molecules in the swollen phase which would be favorable to the transfer of ethanol molecules. The transfer capability of the PP-G-MMA packing was expressed as the height equivalent to a theoretical plate (HETP). The HETP decrease with the height of packing indicating an increasing efficiency of the packed bed distillation column.
