The study of thiophene adsorption onto La(III)-exchanged zeolite NaY by FT-IR spectroscopy

Zeolites NaY and LaNaY (ion-exchanged with aqueous lanthanum nitrate solution) were used as adsorbents for removing organic sulfur compounds from model gasoline solutions (without and with toluene) and fluid catalytic cracked gasoline in fixed-bed adsorption equipment at room temperature and atmosphere pressure. The adsorptive selectivity for organic sulfur compounds was significantly increased when Na+ ions in zeolite NaY were exchanged with lanthanum ions. IR spectra of thiophene adsorption indicate that thiophene is adsorbed onto La3+ ions via direct S-La3+ interaction and Na+ ions via pi-electronic interaction for La3+-exchanged zeolite NaY, but only via pi-electronic interaction with Na+ ions for NaY. The amount of adsorbed thiophene on La3+-exchanged zeolite Y was slightly decreased by coadsorption of benzene, but greatly reduced on NaY. The adsorption of thiophene via interaction with La3+ on La3+-exchanged zeolite Y is hardly replaced by benzene coadsorption. The direct S-La3+ interaction might be the essential reason for the evidently improved adsorptive selectivity of LaNaY for removing organic sulfur compounds from solutions containing large amount of aromatics. (c) 2006 Elsevier Inc. All rights reserved.