SPECIFIC ADSORPTION OF SACCHARIDES BY DEALUMINATED Y-ZEOLITES

Dealumination of Y-zeolites was shown to enhance their affinity to mono-, di-, and trisaccharides by hydrophobic interactions. Henry's adsorption constant increased according to K = b - a In x where x is the fraction of ionic centers inside an elementary cell and a and b represent the interaction with the SiO4 and the AlO4- units, respectively. The high selectivity or molecular recognition seems to be due to the ability of the carbohydrate molecule to change its tautomeric equilibrium and conformation, resulting as well in maximal contact between the CH moieties and the inner zeolite surface as an internal stabilization of the carbohydrate and water molecules inside the pores by hydrogen bonds. The affinity was correlated to the hydration of the adsorbed saccharide molecules. Shape selectivity was found to be superimposed.