5 research outputs found
On the adsorption of toluene on amorphous mesoporous silicas with tunable sorption characteristics
On the Adsorption of Gaseous Mixtures of Hydrocarbons on High Silica Zeolites
An
experimental study of the interactions of an equimolar binary gaseous
mixture of toluene and <i>n</i>-hexane, model molecules
of aromatic and aliphatic fuel-based pollutants, with two dealuminated
high silica zeolites is here presented for the first time. Zeolites
Y and ZSM-5 with diverse textural and surface properties were chosen
as adsorbents, and the effects of their physicochemical features (predominantly
the pore size architecture and silanol content) on sorption capacity
were studied. The host–guest (i.e., sorbent-molecules) interactions
were studied by FTIR and SS-NMR spectroscopies. IR optical adsorption
isotherms of both toluene and <i>n-</i>hexane coadsorbed
on the zeolites allowed the determination of the concentration of
the adsorbed molecules. Variable temperature SS-NMR spectroscopy allowed
the description of the mobility of the pollutant molecules when coadsorbed
at the interface of the zeolites micropores. Finally, we describe
how the proposed innovative approach can be of general use to determine
the selectivity of adsorbent materials for a mixture of hydrocarbons
Interactions of Toluene and <i>n</i>‑Hexane on High Silica Zeolites: An Experimental and Computational Model Study.
The knowledge of host–guest
interactions occurring in confined
space between porous solids and embedded molecules of different origin
is an important task to improve adsorption properties of materials,
thus extending their application fields. In this work, the interactions
of toluene and <i>n</i>-hexane molecules (selected as models
of organic pollutants coming from industrial waste of oil refineries
and gas stations) on different dealuminated high silica zeolites were
studied by means of both experimental and computational approaches.
Zeolites with different textural and surface features were selected
as adsorbents and the effect of their physicochemical properties (i.e.,
pore size architecture and type and amount of surface OH sites) on
sorption capacity were studied. High silica Y and ZSM-5 zeolites (with
a SiO<sub>2</sub>/Al<sub>2</sub>O<sub>3</sub> ratio of 200 and 280,
respectively) were selected as model sorbents. FTIR and SS-NMR spectroscopy
were used to study the type and strength of the host−guest
interactions between the molecules and the zeolite surface. Gravimetric
analysis allowed the determination of the sorption capacity of both
zeolites and their affinity to pollutants. The interactions between
the silica surfaces and pollutants molecules computed at the DFT level,
and supplemented by empirical formulation of dispersion energies,
led to estimate the intensity of hydrogen bonding and cooperative
van der Waals interactions