Studies on the dissolution of glucose in ionic liquids and extraction using the antisolvent method.

Biomass, the fibrous material derived from plant cell walls, is a potentially clean and renewable nonfood feedstock for liquid fuel and chemical production in future biorefineries. The capability of ionic liquids to act as selective solvents and catalysts for biomass processing has already been proven. Thus, they are considered as an alternative to conventional solvents. Nevertheless, phase equilibria with biomass derived compounds is still lacking in the literature. To overcome the lack of experimental data on phase equilibria of biomass carbohydrates in ionic liquids, the solubility of d-glucose in four ionic liquids was measured within a temperature range from 283 to 373 K. Solubility data were successfully correlated with local composition thermodynamic models such as NRTL and UNIQUAC. In this work, the possibility of extracting glucose from these ionic liquids using the antisolvent method has been also evaluated. The parameters affecting the extraction process are the ionic liquid type, ethanol/ionic liquid ratio, temperature, water content, and time. Results indicate that ethanol can be successfully used as an antisolvent to separate glucose from ionic liquids.

Effect of preadsorbed water on the adsorption of p-xylene and m-xylene mixtures on BaX and BaY zeolites.

Adsorption of an equimolar p-xylene/m-xylene mixture on partially hydrated barium-exchanged X and Y zeolites is studied at 423 K in the pressure range 10(-2)-8 hPa by differential calorimetry coupled with manometry and chromatography. Results are consistent with structural studies and Monte Carlo simulations of the literature. The presence of preadsorbed water in supercages increases the adsorption selectivity toward p-xylene to the detriment of the adsorption capacity and the adsorption affinity, as indicated by a sharp decrease of the Henry constants. However, the coadsorption heats at zero filling are not influenced by the presence of water. Therefore, entropic effects seem to play an important role in the coadsorption process. Two adsorption sites whose energy differs are identified by calorimetry. The more energetic site could correspond to the p-xylene or m-xylene molecule in interaction with the compensation cation located in sites II in the supercage, the less energetic to the adsorption of p-xylene molecule in the 12-ring window joining two supercages. The presence of this second site for p-xylene could be at the origin of the selectivity.