Adsorption of tetrahydrothiophene on faujasite type zeolites : Breakthrough curves and FTIR spectroscopy study
Résumé
Adsorption of tetrahydrothiophene (THT) on NaX, CaX, AgX, and H-USY was studied by dynamic adsorption method and FTIR spectroscopy. The stoichiometric adsorption capacities are not very different for all materials, which is indicative of a complete micropore filling. In contrast, the overall rate constant of adsorption, determined from fitting the breakthrough curves with Bohart–Adams equation, is two times greater for H-USY than for type X zeolites. For NaX, CaX and H-USY, heating under N2 flow at 300 8C allows to restore completely their initial adsorption capacities. In the case of AgX the same treatment results in a twofold lose of capacity accompanied by a collapse of the zeolite structure as evidenced by XRD. The nature of interaction between THT molecules and zeolites was characterized by FTIR spectroscopy. Only a weak interaction through hydrogen bonding was observed for THTon H-USY leading to an almost complete desorption at 100 8C. For NaX and CaX adsorbed molecules are gradually eliminated when heated to 300 8C while completely different pattern was observed for THTadsorbed on AgX on which the amount of the adsorbate remains nearly constant between 25 and 200 8C, but rapidly decreases on further heating. Such a behavior is indicative of much stronger interaction between THT molecules and Ag+ cations in agreement with the data on the regeneration of the adsorbents.