Pressure Swing Adsorption with Cassava Adsorbent for Dehydration of Ethanol Vapor

Ethanol has become more attractive in fuel industry either as fuel itself or an additive that helps enhancing the octane number and combustibility of gasoline. This research studied a pressure swing adsorption using cassava-based adsorbent prepared from mixture of cassava starch and cassava pulp for dehydration of ethanol vapor. The apparatus used in the experiments consisted of double adsorption columns, an evaporator, and a vacuum pump. The feed solution contained 90-92 %wt of ethanol. Three process variables: adsorption temperatures (110, 120 and 130°C), adsorption pressures (1 and 2 bar gauge) and feed vapor flow rate (25, 50 and 75 % valve opening of the evaporator) were investigated. According to the experimental results, the optimal operating condition for this system was found to be at 2 bar gauge for adsorption pressure, 120°C for adsorption temperature and 25% valve opening of the evaporator. Production of 1.48 grams of ethanol with concentration higher than 99.5 wt% per gram of adsorbent was obtained. PSA with cassavabased adsorbent reported in this study could be an alternative method for production of nearly anhydrous ethanol. Dehydration of ethanol vapor achieved in this study is due to an interaction between free hydroxyl group on the glucose units of the starch and the water molecules.

Authors:

• Chontira Boonfung
• Panarat Rattanaphanee

Keywords:

• Adsorption
• PSA
• Ethanol
• Dehydration
• Cassava.

References:

[1] M. Ladisch and K. Dyck, "Dehydration of Ethanol: New Approach
Gives Positive Energy Balance," Science, vol. 205, pp. 898-900, 1979.
[2] M. Ladisch, M. Voloch, J. Hong, P. Blenkowski and G. Tsao,
"Cornmeal Adsorber for Dehydrating Ethanol Vapors," I&EC Proc. Des.
Develop., vol. 23, pp. 437-443, 1984.
[3] H. Chang, X. Yuan, H. Tian and A. Zeng, "Experiment and Prediction of
Breakthrough Curves for Packed Bed Adsorption of Water Vapor on
Cornmeal," Chem. Eng. Process., vol. 45, pp. 747-754 ,2006.
[4] J. Hong, M. Voloch, M. Ladisch and G. Tsao, "Adsorption of Ethanol-
Water Mixtures by Biomass Materials," Biotech. Bioeng., vol. 24, pp.
725-730, 1982.
[5] P. Bienkowski, A. Barthé, M. Voloch, R. Neuman and M. Ladisch,
"Breakthrough Behavior of 17.5 mol% Water in Methanol, Ethanol,
Isopropanol, and t-Butanol Vapors Passed over Corn Grits," Biotech.
Bioeng., vol. 28, pp. 960-964, 1986.
[6] L. Anderson, M. Gulati, P. Westgate, E. Kvam, K. Bowman and M.
Ladisch, "Synthesis and Optimization of a New Starch-Based Adsorbent
for Dehumidification of Air in a Pressure-Swing Dryer," Ind. Eng.
Chem. Res., vol. 35, pp. 1180-1187, 1996.
[7] M. Ladisch, "Biobased Adsorbents for Drying of Gases," Enzyme
Microb. Tech., vol. 20, pp. 162-164, (1997).
[8] T. Benson and C. George, "Cellulose Based Adsorbent Materials for the
Dehydration of Ethanol Using Thermal Swing Adsorption," Adsorption,
vol. 11, pp. 697-701, 2005.
[9] G. Vareli, P. Demertzis and K. Akrida-Demertzi, "Effect of
Regeneration Thermal Threatment of Cellulosic and Starchy Materials
on Their Capacity to Separate Water and Ethanol," J. Cereal Sci., vol.
31, pp. 147-154, 2000.
[10] X. Han, X. Ma, J. Liu and H. Li, "Adsorption Characterisation of Water
and Ethanol on Wheat Starch and Wheat Gluten Using inverse Gas
Chromatography," Carbohydrate. Polym., vol. 78, pp. 533-537, 2009.
[11] A. Al-Asheh, F. Banat and N. Al-Lagtah, "Separation of Ethanol-Water
Mixtures Using Molecular Sieves and Biobased Adsorbents," Trans
IChemE, Part A, Chem. Eng. Res. Des., vol. 82(A7), pp. 855-864, 2004.
[12] K. Beery, and M. Ladisch, "Chemistry and Properties of Starch Based
Desiccants," Enzyme Microb. Tech., vol. 28, pp. 573-581, 2001.
[13] K. Beery, and M. Ladisch, "Adsorption of Water from Liquid-Phase
Ethanol-Water Mixtures at Room Temperature Using Starch-Based
Adsorbents," Ind. Eng. Chem. Res., vol. 40, pp. 2112-2115, 2001.
[14] Chontira Boonfung, Panarat Rattanaphanee, Cassva-based adsorbent for
ethanol dehydration, J. KMUTNB.,vol. 20, No. 2, pp. 196-202, 2010.