Authors:V. Rac, Vesna Rakić, S Gajinov, Vera Dondur, and Aline Auroux
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.
Authors:S. Marković, Vera Dondur, R. Dimitrijević, and S. Macura
the present study, we performed an investigation of phase transformation of
zeolite Na-GIS in temperature interval from room temperature up to 1300C.
The collapse of S4R and S8R (secondary building units in zeolite Na-GIS) and
the forming of pure sodium nepheline phase, consists of S6R, was examined.
During the thermal transformation of Na-GIS zeolite symmetry of rings was
changed and their deformation increases. The irregularity of rings causes
the appearance of defect modes in the IR spectra of amorphous precursors.
Investigated phases were characterized by XRPD, IR, NMR and DSC methods. A
semiempirical method AM1 was used for calculation of vibrational spectrum
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.