Investigation into the desorption equilibrium of esters in activated carbon using supercritical CO2

Calabro, John R. (2004). Investigation into the desorption equilibrium of esters in activated carbon using supercritical CO2 MPhil Thesis, School of Engineering, The University of Queensland.

       
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Author Calabro, John R.
Thesis Title Investigation into the desorption equilibrium of esters in activated carbon using supercritical CO2
School, Centre or Institute School of Engineering
Institution The University of Queensland
Publication date 2004
Thesis type MPhil Thesis
Supervisor Professor Suresh Bhatia
Total pages 78
Collection year 2004
Language eng
Subjects L
290000 Engineering and Technology
670700 Industrial Chemicals and Related Products
Formatted abstract
The analysis of supercritical desorption isotherms of flavour esters from activated carbon have been carried out in this study. Ethyl isovalerate and ethyl propionate were chosen as the esters due to their differing affinity to both supercritical carbon dioxide and activated carbon. Both binary (one ester and carbon dioxide) and ternary (two esters and carbon dioxide) isotherms were measured. The desorption experiments were carried out at temperatures of 309 K, 313 K and 318 K and a pressure of 90 bar. Supercritical desorption can be seen as competitive adsorption between the solvent (carbon dioxide) and the solute. Two multi component models have been used to describe the experimental data with varying results. A modified version of the vacancy solution theory failed to correlate the data even when it was modified to consider lateral interactions. The Heterogeneous Fowler Guggenheim equation, which considers lateral interactions, fit the data well although the parameters obtained were not meaningful for ethyl propionate. This was explained by both the model underestimation of the stronger interactions between carbon dioxide and ethyl propionate and the nonideality of the bulk phase. This led to the subsequent failure of the ternary model. A model that can adequately describe the strong interactions involved is needed. The structural damage to the carbon caused by exposure to the high pressure in supercritical desorption was also studied. While there appeared to be a small amount of damage in the 5-6 A region, the pore size distribution was generally not affected. Repeated desorption appeared to increase the damage slightly, if at all in the 5-6 A region.
Keyword Supercritical fluid extraction
Carbon, Activated
Esters
Liquid-liquid equilibrium
Liquid carbon dioxide

Document type: Thesis
Collection: UQ Theses (RHD) - UQ staff and students only
 
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Created: Fri, 24 Aug 2007, 18:33:39 EST