Innovative Strategy for Truly Reversible Capture of Polluting Gases—Application to Carbon Dioxide

Abstract

This paper consists of a deep analysis and data comparison of the main strategies undertaken for achieving truly reversible capture of carbon dioxide involving optimized gas uptakes while affording weakest retention strength. So far, most strategies failed because the estimated amount of CO2 produced by equivalent energy was higher than that captured. A more viable and sustainable approach in the present context of a persistent fossil fuel-dependent economy should be based on a judicious compromise between effective CO2 capture with lowest energy for adsorbent regeneration. The most relevant example is that of so-called promising technologies based on amino adsorbents which unavoidably require thermal regeneration. In contrast, OH-functionalized adsorbents barely reach satisfactory CO2 uptakes but act as breathing surfaces affording easy gas release even under ambient conditions or in CO2-free atmospheres. Between these two opposite approaches, there should exist smart approaches to tailor CO2 retention strength even at the expense of the gas uptake. Among these, incorporation of zero-valent metal and/or OH-enriched amines or amine-enriched polyol species are probably the most promising. The main findings provided by the literature are herein deeply and systematically analysed for highlighting the main criteria that allow for designing ideal CO2 adsorbent properties.

Surface Basicity and Hydrophilic Character of Coal Ash-Derived Zeolite NaP1 Modified by Fatty Acids

“…Adequate surface basicity and hydrophobic character may be tailored for such purposes through suitable modifications, such as amine incorporation. Nonetheless, these modifications often lead to decreases in surface area and pore volume [ 11 , 12 , 13 ], more particularly when dealing with zeolite frameworks [ 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ].…”

“…The special interest devoted herein to NaP1 arises not only from its intrinsic adsorptive properties, which have barely been investigated so far [ 26 , 27 , 28 , 29 ], but also from the beneficial incorporation of organic species [ 30 , 31 ]. CO 2 chemically adsorbs on amines via the unavoidable formation of carbamate, which requires heating for the regeneration of amine-functionalized adsorbents [ 9 , 13 , 32 , 33 ]. Since the CO 2 :amine reaction is favored by high amine content [ 25 , 34 ], lower amine loadings should promote weak retention with an easier release of CO 2 [ 35 ].…”

“…Substituting amines with other chemical species is an original approach to mitigate surface basicity. Scarce attempts achieved thus far revealed that OH-enriched clay minerals allow the achievement of truly reversible CO 2 capture but at the expense of CO 2 retention capacity [ 13 , 36 , 37 , 38 , 39 , 40 , 41 ]. The incorporation of fatty acids (FAs) is another strategy, which can only be justified by their sources from animal fats (long chain) or from industrial wastes [ 42 , 43 , 44 , 45 ].…”