Though the post – combustion capture process by absorption – regeneration is the more mature technology in Carbon Capture Utilization and Storage (CCUS), its cost reduction is still necessary and requires immediate attention. The high cost in the capture process relates principally to infrastructure, energy and disposal of the CO2 captured.

If some of the infrastructure with its ancillaries could be removed from the capture process, then the cost involved in the capture process could be drastically reduced and the only problem would be how to dispose of the CO2 captured without re-introducing it back into the atmosphere. This work seeks to solve both the issues of cost reduction and the disposal of CO2 captured in an environmentally friendly manner.

In this work, a catalyst is being developed to accelerate CO2 absorption to boost CO2 loading in a novel solvent that is also being developed by the group. This catalyst, which is alkaline, would generate a catalytic pathway where a lower activation energy is required for the absorption process and provide a large inter-facial area for mass transfer. This would help the system to approach equilibrium faster than the non-catalyzed reaction, which would enable the use of a much smaller absorber vessel and a higher CO2 uptake level in the solvent.

The rich solvent would be utilized in the making of concrete, mortar and grout after it has chemically absorbed CO2 from the exhaust gas of major industries and power plants. In the concrete-based industry, the rich solvent would replace the water component used during the concrete or mortar making process. Using CO2-loaded solvent facilitates CO2 utilization in the concrete-based industries. This would help to accelerate the curing process leading to the complete curing of the concrete.

By this approach, CO2 will be captured using a smaller absorber vessel, the regeneration (desorption) section of the capture process will be eliminated as well as its ancillaries and energy requirements, and CO2 will be utilized and permanently stored in the concrete, mortar and grout.

Effect of Intermolecular Interaction of Amine on Specific Heat Capacity and Heat Vaporization

The knowledge of intermolecular forces and their strength between molecules of amines is a very important piece of information that one can use to determine the behavior of amines used for capture of carbon dioxide from industrial exhaust gases. In today’s what’s cooking post, we discuss on how the intermolecular forces that hold molecules of the amine together affect its specific heat capacity (Cp) and heat of vaporization (ΔHvap) which in turn, can affect the heat consumption of the amine process.

Intermolecular forces stem from the attraction of opposite charges that exist between molecules of a compound. Strength of these forces are highly dependent on the atomic and molecular arrangement of the compound’s molecule. Two major factors that have a direct impact on the strength of the forces are;

1. The molecule’s size of electron cloud and
2. The extent to which it can distort to form opposite charges on the molecule.

In general, an increase in the electron cloud size which commonly can be estimated by the number of electrons of that compound, increases the force strength. The same trend is also applied to the ability to distort the molecular electrons, which if increased, the strength of the intermolecular attraction will also increase. Our graphical abstract shows a side-by side comparison of 2 amines whose intermolecular forces are weak and strong, respectively. The amine molecules with weaker intermolecular interactions (e.g. smaller electron cloud and smaller electron cloud distortion) experience less attractive forces between them. As a result, the molecules are only held together loosely.

Such a situation provides the molecules with more freedom of movement which further facilitates the amine in the process of gaining kinetic energy upon the absorption of heat and allows the amine temperature to rise easily. This phenomenon is reflected in the amine’s lower Cp, an intrinsic property of amine that shows the amount of energy needed to raise the temperature of one gram of the amine by one degree of temperature. The heat of vaporisation, ΔHvap typically dependent on the connectivity strength of molecules also increases with an increase of the intermolecular force strength.

In comparison to an amine with stronger intermolecular forces (e.g. larger electron cloud and larger electron cloud distortion), the molecules are more attracted and more tightly bound to one another. The gaining of kinetic energy induced by the same amount of heat supply to the former amine to raise the amine temperature will therefore occur to a lesser extent in this case. So, a smaller rise in temperature is observed with a reflection of higher Cp and ΔHvap values.

The heat duty of an amine comprises sensible heat (required for temperature rise), latent heat (required for a phase change from liquid to vapor), and desorption heat. At least the first 2 heat components of amine heat duty will be affected by the strength of the intermolecular forces of the amine molecules. The stronger interactions in an amine will require more sensible and latent heats in the desorption process as compared to the weaker interaction in an amine. If heats of desorption of the 2 amines are approximately close, the stronger interaction amine will likely have a higher heat duty than the weaker amine.

Having a fundamental knowledge of an amine at the atomic level, for example, understanding the concept of intermolecular forces that exist between amine molecules, can definitely help one to pre-screen amines with the least energy requirement before further testing them to finally select the best amine.