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Room-temperature interaction of n-hexane with ZSM-5 zeolites

Microcalorimetric and temperature-programmed desorption studies

Journal of Thermal Analysis and Calorimetry
Authors: V. Rac, Vesna Rakić, S Gajinov, Vera Dondur, and Aline Auroux

Abstract  

In this work, room temperature interaction of n-hexane with HZSM-5 (Si/Al=20) and ion-exchanged samples containing one (CuZSM-5, FeZSM-5 and MnZSM-5) or two transition-metal cations (Fe,CuZSM-5; Cu,MnZSM-5 and Fe,MnZSM-5) was studied by microcalorimetry and TPD methods. Both differential heats and the amounts of n-hexane adsorbed per one unit cell were quantitatively determined. Higher heats of adsorption and higher amounts of adsorbed gas were found for ion-exchanged samples than for HZSM-5. The experiments of n-hexane adsorption on hydrated samples were also performed. The amounts of n-hexane adsorbed on hydrated ZSM-5 were lower in comparison with dehydrated samples, while the energies of interaction were similar.

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Abstract  

Temperature-programmed desorption coupled with mass spectrometer as a detector (TPD), IR and 13C NMR measurements are used to study the adsorption of n-hexane on hydrated HZSM-5 and NH4ZSM-5 zeolites. The 13C NMR measurements show that n-hexane can access the pore structure of ZSM-5 zeolites previously saturated with water. TPD spectra of n-hexane are monitored in the temperature region 50–300C, in the case of fully or partially hydrated samples; two-stage desorption of n-hexane is found. Simultaneous desorption of water and n-hexane in the same temperature region are found, in all investigated samples.

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