Mota et al. explored this technology to separate CH 4 /CO 2 on activated carbon
using nitrogen as a carrier gas in a novel single-column setup with the asynchronous
shifting of the inlet/outlet ports. They also simulated an optimized four-column SMB
process experimentally to obtain both product streams with a high purity of
98% [80].
However, prior to implementing technology at the industrial scale, it is necessary
to go through a pilot scale. For a pilot-scale study to be successful, it is essential to
begin with the adsorbent characterization and followed by adsorption equilibrium
and dynamic studies for the target system. With this data, it becomes possible to
perform mathematical modeling and model validation. Finally, after gathering all the
necessary data, it is possible to design at pilot scale the technology most promising
for the systems under study.
3 From Laboratory to Industrial Scale
The success of an adsorptive separation process is closely related to the choice of a
suitable adsorbent for the mixture to be separated. The adsorbent should fulfill
specific characteristics such as high selectivity, high adsorption, and regeneration
capacity. The particle size, crystal and porous sizes, density, and other properties are
of the utmost importance to select the “ideal” adsorbent and also to perform
accurately process modeling, hence the need to conduct a careful characterization
of the materials. The characterization of these materials is thus necessary to obtain
the required physical properties, namely, the morphology, particle porosity, crystal
size, material strength, and densities, among others. Usually, scanning electron
microscopy (SEM) is performed to obtain high-resolution images of the solid surface
and provide the crystal size. SEM can be complemented with energy dispersive
spectroscopy (EDS) for the chemical characterization by detecting the chemical
elements locally present in the sample [81, 82]. The powder X-ray diffraction
(XRD) pattern is a useful tool to study crystal structures and atomic spacing; this
technique allows the determination of the phase and its crystallinity [83, 84].
The pore networks are classified, considering the presence of different adsorption
mechanisms. According to the International Union of Pure and Applied Chemistry
(IUPAC), micropores have sizes below 2 nm and higher adsorption enthalpies when
compared with mesopores (range 2 to 50 nm) and macropores (>50 nm). This
occurrence is due to the overlapping of adsorption potentials of the micropore
walls. Micropores play a more significant role in physisorption processes, while
meso- and macropores act as transport systems [85]. Nitrogen (N 2 ) adsorption at
77 K and argon adsorption at 87 K are standard characterization techniques, while
carbon dioxide (CO 2 ) adsorption at 273 K appears as a complementary technique to
evaluate the narrow microporosity. So, usually, the microporosity of each adsorbent
is assessed by physical sorption of N 2 at 77 K and by physical sorption of CO 2 at
273 K.
Perspectives of Scaling Up the Use of Zeolites for Selective Separations from. . .
153
using nitrogen as a carrier gas in a novel single-column setup with the asynchronous
shifting of the inlet/outlet ports. They also simulated an optimized four-column SMB
process experimentally to obtain both product streams with a high purity of
98% [80].
However, prior to implementing technology at the industrial scale, it is necessary
to go through a pilot scale. For a pilot-scale study to be successful, it is essential to
begin with the adsorbent characterization and followed by adsorption equilibrium
and dynamic studies for the target system. With this data, it becomes possible to
perform mathematical modeling and model validation. Finally, after gathering all the
necessary data, it is possible to design at pilot scale the technology most promising
for the systems under study.
3 From Laboratory to Industrial Scale
The success of an adsorptive separation process is closely related to the choice of a
suitable adsorbent for the mixture to be separated. The adsorbent should fulfill
specific characteristics such as high selectivity, high adsorption, and regeneration
capacity. The particle size, crystal and porous sizes, density, and other properties are
of the utmost importance to select the “ideal” adsorbent and also to perform
accurately process modeling, hence the need to conduct a careful characterization
of the materials. The characterization of these materials is thus necessary to obtain
the required physical properties, namely, the morphology, particle porosity, crystal
size, material strength, and densities, among others. Usually, scanning electron
microscopy (SEM) is performed to obtain high-resolution images of the solid surface
and provide the crystal size. SEM can be complemented with energy dispersive
spectroscopy (EDS) for the chemical characterization by detecting the chemical
elements locally present in the sample [81, 82]. The powder X-ray diffraction
(XRD) pattern is a useful tool to study crystal structures and atomic spacing; this
technique allows the determination of the phase and its crystallinity [83, 84].
The pore networks are classified, considering the presence of different adsorption
mechanisms. According to the International Union of Pure and Applied Chemistry
(IUPAC), micropores have sizes below 2 nm and higher adsorption enthalpies when
compared with mesopores (range 2 to 50 nm) and macropores (>50 nm). This
occurrence is due to the overlapping of adsorption potentials of the micropore
walls. Micropores play a more significant role in physisorption processes, while
meso- and macropores act as transport systems [85]. Nitrogen (N 2 ) adsorption at
77 K and argon adsorption at 87 K are standard characterization techniques, while
carbon dioxide (CO 2 ) adsorption at 273 K appears as a complementary technique to
evaluate the narrow microporosity. So, usually, the microporosity of each adsorbent
is assessed by physical sorption of N 2 at 77 K and by physical sorption of CO 2 at
273 K.
Perspectives of Scaling Up the Use of Zeolites for Selective Separations from. . .
153