Adsorption of alcohols from aqueous solution by ZSM-5

Isotherms have been measured for the adsorption from aqueous solution of water soluble alcohols onto the zeolite ZSM-5. For methanol and ethanol the amount of alcohol adsorbed increases with increasing percentage of Al₂O₃, whereas for n-butanol the amount adsorbed decreases as the amount of Al₂O₃ increases. Adsorption of alcohols is also dependent on the cation form. For the alkali metal ion forms, the amount of alcohol adsorbed decreases as the ionic size increases, the effect being particularly pronounced for Cs⁺. Subsequent alcohol desorption was studied by thermogravimetry and mass spectrometry which showed that the zeolite retained a portion of the alcohol to temperatures (ca 250°C) sufficiently high that catalytic breakdown occurred. This reduces its likely potential for commercial alcohol concentration.