https://doi.org/10.3390/su14084750
“The intensive energy consumption of the solvent regeneration process is one of the crucial factors that influences the techno-economics of the existing CO2 absorption process. Various studies and reviews have been conducted on the employment of additives in solvent to enhance absorption performance. However, comprehensive reviews on enhancing the regeneration/desorption performance of a solvent are limited. After reviewing the potential of nanoparticles on solvent regeneration in an earlier section, the proposed future directions in this field of research can be concluded as demonstrated in Table 11.”
Table 11. Summary of metal oxides, zeolite and mesoporous silica nanoparticles according to the selection criteria.
| Potential Direction | |
|---|---|
| Metal Oxides |
|
| Zeolites |
|
| Mesoporous Silica |
|
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(1)
The existing studies on the regeneration performance of nanoparticles is still limited. The employment of different types of nanoparticles has been widely studied, though many of them do not focus on desorption performance. For instance, the employment of Fe3O4 and CNT nanoparticles has been reported to have a better absorption performance than SiO2 and Al2O3 at lower concentrations [145]. However, the desorption performance has yet to be investigated for these nanoparticles.
(2)
The stability of a nanoparticle is an important characteristic in the application of the CO2 separation process. Long term stability for nanoparticles is considered to be an issue for practical applications as different nanoparticles may require different stability methods. Identifying an easy and low-cost method to improve the stability should be considered. It has been reported that the addition of surfactants could further improve the stability, however their effects on the desorption rate should be further investigated. Modifying the surface, for instance, on Fe3O4, is one way to improve its stability [146]. However, its effect on the desorption performance of CO2 capture should be further discussed.
(3)
The enhancement factors that affect the regeneration performance of nanoparticles have been explained in terms of the size, concentration and type in the current review. More factors should be considered, such as the gas flow rate and the gas concentration. Apart from that, the physical and chemical properties of transformed nanoparticles should be properly discussed. The density, viscosity and other thermodynamic properties are important to further evaluate the overall performance of CO2 capture.
(4)
Since nanoparticles exhibit both catalytic and physical effects on the desorption performance, the relationship between the two mechanisms should be properly discussed. Metal oxide nanoparticles have been widely discussed as having both effects. However, this is not the case for zeolite and mesoporous silica.
(5)
Apart from that, the reduction in the heat duty of using nanoparticles has been discussed. Future research should quantitively evaluate the regeneration energy requirement and its feasibility for these nanoparticles to be implemented in large scale applications.
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