INVESTIGADORES
BOIX Alicia Viviana
artículos
Título:
Experimental and theoretical studies about the adsorption of toluene on zeolites ZSM5 and mordenite modified with Cs
Autor/es:
SERRA, RAMIRO; MIRÓ, EDUARDO E.; BOLCATTO, PABLO; BOIX, ALICIA V.
Revista:
MICROPOROUS AND MESOPOROUS MATERIALS
Editorial:
ELSEVIER SCIENCE BV
Referencias:
Lugar: Amsterdam; Año: 2012 vol. 147 p. 17 - 29
ISSN:
1387-1811
Resumen:
In this work, we studied the adsorption capacity and thermal stability of toluene on ZSM5 and mordenite
zeolites with different exchange cations (H, Na and Cs). The interaction of the hydrocarbon molecules
with the adsorption sites was also addressed with both experimental and theoretical techniques. Flowadsorption
measurements were carried out in order to obtain breakthrough curves as well as TPD experiments.
Molecular simulations were performed using the Density Function Theory (DFT). The results
show that, in general, mordenite samples have a better adsorption capacity than ZSM5 samples and that
the thermal stability of the adsorbed toluene is more influenced by the exchanged cations than by the
zeolite structure. The overall basicity of the samples depends on the exchanged cations, following the
Cs > Na > H order. The main interaction of toluene takes place between the p electrons of the aromatic
ring and the Lewis sites generated, and another interaction takes place between C?H groups and the zeolite
network oxygen.
The increase of the Cs loading decreases the surface area and pore volume of the zeolites, thus decreasing
the available sites for the overall toluene adsorption at 100 _C. Through TPD experiments both the U
parameter, which represents the fraction of toluene retained at temperatures higher than 100 _C, and the
temperature at which the toluene desorbs were measured. It was observed that in the Cs exchanged samples,
U is higher but the thermal stability (temperature of the maximum desorption rate on TPD) follows
the order NaMOR = NaZSM5 > CsNaZSM5 > CsNaMOR > CsHMOR = CsHZSM5 > HMOR > HZSM5. The
molecular calculations for the NaMOR structure determined that the interaction energies were higher
for NaMOR when compared with the HMOR structure and increased even more when Cs was exchanged.
These facts are in line with the experimental results.