| Abstract
| - In the framework of research considering adsorption for gasoline desulfurization purposes, dynamic adsorptionexperiments have been performed to study a comparison between thiophene and toluene affinities towardY-faujasite adsorbents (Si/Al = 2.4) exchanged with various alkali metal cations (Li+, Na+, K+, Rb+, Cs+).These experiments have been carried out at two concentration ranges in liquid n-heptane solutions: around25 mmol·L-1 for competitive adsorptions and around 1.25 mmol·L-1 for single-solute adsorptions.Complementary microcalorimetry studies have been carried out in order to investigate the interaction ofnucleophilic compounds toward alkaline Y zeolites, by measuring the adsorption enthalpy of CCl4 onto NaYand CsY sorbents. The results clearly exhibit two opposite trends for the adsorption of thiophene and toluenemolecules onto alkaline Y faujasites. The thiophene affinity increases with cation electropositivity, while thetoluene affinity decreases as the cations are more electropositive. Thus, from a favorable adsorption for tolueneonto the LiY zeolite (αthio/tol = 0.38 at ca. 26 mmol·L-1), the selectivities shift in favor of thiophene so thatthe αthio/tol value reaches 3.00 with the CsY zeolite. The calorimetry measurements of CCl4 adsorption haveexhibited an increase of the adsorption enthalpy with more electropositive cations, which seems to indicatethat thiophene molecules are adsorbed similarly to CCl4, i.e., by strong interaction between the nucleophilicS atom of thiophene and the cationic charge. However, toluene should be mainly stabilized on the adsorptionsites through other interactions, as combined attractions between the H atoms of toluene and the O atoms ofthe zeolite framework surrounding the SII cation can be suggested.
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