impacts of temperature and loading over both the diffusive and affinity properties of
a zeolitic adsorbent can be observed. As a consequence, works rationalizing the
impact of the use of the new available synthetic routes [46, 47] can significantly help
improving the development of adsorbents and their associated industrial
performances.
5.4 Ensuring the Continuous Regenerability
and Thermochemical and Mechanical Properties
of the Adsorbent
During the operating life, the adsorbent is exposed to tens of thousands of production/regeneration cycles. Either in the case of cyclic or countercurrent adsorption
processes, the employed zeolitic materials are exposed to severe mechanical and/or
thermal evolutions. In the case of PSA, both pressure and temperature (at a lesser
extent) continuously evolve during the different cycle phases (pressurization,
adsorption, blowdown, or purge). For TSA processes, the associated temperature
operating range is larger than in the case of PSA. Finally, SMB operation is
characterized by the use of significantly different linear velocities between the
different adsorption zones. This fact usually results in important pressure shocks at
some critical steps during the cycle. Although the selected employed technologies
are chosen to minimize such effects, the adsorbent must present excellent mechanical and thermochemical properties. From the point of view of the mechanical
resistance, the use of a binder during the agglomeration is the generalized technical
solution. Nevertheless, the introduction of the mentioned binder results in a reduction of the volumetric adsorption capacity of the adsorbent. To palliate to this
reduction, strategies like zeolitization allow an almost complete recovery of the
original capacity [48, 49]. By means of the mentioned strategies, the mechanical
resistance is considerably improved and values higher than 4 MPa can be obtained in
the crushing strength test [50]. As a consequence, the production of fine particles by
mechanical attrition is minimized and potential dramatic impacts during the operation avoided. Notwithstanding, the adoption of the before-mentioned or similar
strategies is not always fully understood. Most of the related available information
is found in the form of patents, and a lack of detailed studies exists [51, 52]. Indeed,
the introduction of the binder as well as its ultimate transformation implies the
modification of both the porous network and the surface nature. These impacts are
not innocuous in the case of separations where the mass transfer in the meso-/
macroporous network governs the performance of the adsorbent. In an analogous
way, separation driven by kinetic effects can be impacted if the pore mouth is
modified at the moment of binder crystallization. Comparable effects are associated
with the adsorbent shaping operations where the surface barrier phenomena can be
altered.
Industrial Zeolite Applications for Gas Adsorption and Separation Processes
221
a zeolitic adsorbent can be observed. As a consequence, works rationalizing the
impact of the use of the new available synthetic routes [46, 47] can significantly help
improving the development of adsorbents and their associated industrial
performances.
5.4 Ensuring the Continuous Regenerability
and Thermochemical and Mechanical Properties
of the Adsorbent
During the operating life, the adsorbent is exposed to tens of thousands of production/regeneration cycles. Either in the case of cyclic or countercurrent adsorption
processes, the employed zeolitic materials are exposed to severe mechanical and/or
thermal evolutions. In the case of PSA, both pressure and temperature (at a lesser
extent) continuously evolve during the different cycle phases (pressurization,
adsorption, blowdown, or purge). For TSA processes, the associated temperature
operating range is larger than in the case of PSA. Finally, SMB operation is
characterized by the use of significantly different linear velocities between the
different adsorption zones. This fact usually results in important pressure shocks at
some critical steps during the cycle. Although the selected employed technologies
are chosen to minimize such effects, the adsorbent must present excellent mechanical and thermochemical properties. From the point of view of the mechanical
resistance, the use of a binder during the agglomeration is the generalized technical
solution. Nevertheless, the introduction of the mentioned binder results in a reduction of the volumetric adsorption capacity of the adsorbent. To palliate to this
reduction, strategies like zeolitization allow an almost complete recovery of the
original capacity [48, 49]. By means of the mentioned strategies, the mechanical
resistance is considerably improved and values higher than 4 MPa can be obtained in
the crushing strength test [50]. As a consequence, the production of fine particles by
mechanical attrition is minimized and potential dramatic impacts during the operation avoided. Notwithstanding, the adoption of the before-mentioned or similar
strategies is not always fully understood. Most of the related available information
is found in the form of patents, and a lack of detailed studies exists [51, 52]. Indeed,
the introduction of the binder as well as its ultimate transformation implies the
modification of both the porous network and the surface nature. These impacts are
not innocuous in the case of separations where the mass transfer in the meso-/
macroporous network governs the performance of the adsorbent. In an analogous
way, separation driven by kinetic effects can be impacted if the pore mouth is
modified at the moment of binder crystallization. Comparable effects are associated
with the adsorbent shaping operations where the surface barrier phenomena can be
altered.
Industrial Zeolite Applications for Gas Adsorption and Separation Processes
221