Adsorption - Introduction to Carbon Capture and Sequestration - page 256

3.0

Simulations (Garcia-Perez et al .)
Experiments (Garcia-Perez et al .)
Experiments (Sun et al .)
Simulations (Lin et al .)

2.5

2.0

1.5

1.0

0.5

10 -3 10 -2 10 -1 10 0

10

Pressure (bar)

Figure 6.4.2 Comparison of experimental and simulated adsorption isotherms
Test of the reliability of the prediction through a comparison of the adsorption isotherms
of CO 2 in the zeolite MFI that have been predicted using molecular simulation with the
experimental.

Figure 6.4.3 indeed confi rms that there is an optimal CO 2 Henry
coeffi cient. If we have too low a Henry coeffi cient, the parasitic energy is
high because the working capacity of the material is too low. If the Henry
coeffi cient is too high, it takes too much energy to regenerate the
material.
Another important observation is that we have a broad optimum for
parasitic energy as a function of Henry coeffi cient. The reason for this
broad minimum is that the Henry coeffi cient shows a strong correlation
with the heat of adsorption, and the heat of adsorption has two opposing
contributions to the parasitic energy. A higher heat of adsorption
increases the working capacity, and while this reduces the parasitic
energy, it is offset by the requirement to supply more energy to desorb
CO 2 , which again increases the parasitic energy.
This computational screening shows a large set of zeolite structures
that have a parasitic energy well below the current MEA (monoethanola-
mine, see Chapter 5) technology (1,060 kJ/kg CO 2 ). Inspection of some
of these optimal structures shows that they are diverse: we fi nd one-,
two-, or three-dimensional channel structures, cage-like topologies, and