Encapsulation of gases in powder solid matrices and their applications: A review

Abstract

Gas encapsulation in solid matrices can be an important means to sequester harmful or greenhouse gases and to store useful gases for their subsequent release for a targeted application. In this review, recent developments, the characteristics and gas adsorption capacity of non-organic and organic solid powder matrices (e.g. activated carbons, carbon nanotubes, zeolites, metal-organic frameworks, and cyclodextrins); and potential applications of their complexes in various fields (energy, environment protection, nano-device production, medicine, and food and agriculture productions) are described.

Feasibility of CO2 adsorption by solid adsorbents: a review on low-temperature systems

“…From quantification of the CO 2 isosteric heat of adsorption, the nature of the CO 2 adsorption can be determined, where low heat of adsorption (8-41 kJ mol -1 ) revealed physisorption and higher value of heat of adsorption (62-418 kJ mol -1 ) indicated chemisorption. Furthermore, this parameter showed that the CO 2 interaction with the adsorbent material might be mainly an intermolecular force or hydrogen bond (Ho et al 2014;Zhao et al 2012).…”

“…Based on the nature of interactions, adsorption can be classified into two types: (1) physical adsorption and (2) chemical adsorption. In physical adsorption, the molecules are physisorbed because of physical forces (dipoledipole, electrostatic, apolar, hydrophobic associations or Van der Waals) where the bond energy is 8-41 kcal mol -1 , while in chemical adsorption, molecules chemisorbed (chemical bond; covalent, ionic or metallic) and the bond energy is about 60-418 kcal mol -1 (Ho et al 2014). The adsorbent sample used in physisorption can be regenerated by simple degassing method.…”

“…Chemisorption is useful where permanent binding and trapping of harmful gas is required, but after chemisorption, the regeneration of solid matrices is very challenging. For instance, lime, soda lime or limestone, which generates strong alkali hydroxyls [e.g., NaOH, KOH, Ca(OH) 2 , Mg(OH) 2 ] in the presence of moisture, interact chemically with acid gases (CO 2 , SO 2 , NO 2 ) (Ishibe et al 1995;Ho et al 2014 In the process of gas adsorption, the molecules of the gas temporarily depart from the gas phase when it comes to the vicinity of the solid surface and undergoes an interaction with it. Molecules in this new condensed state remain for a short period and then return to the gas phase.…”

“…For example in hydrogen adsorption on carbon nanotubes, lower temperature favors adsorption. On the other hand, gas adsorption on zeolite increased at relatively high temperature because of the pores enlargement and higher kinetic energy of the gas molecules, which allows molecules to diffuse more easily into the cavities of solid matrices (Goetz et al 2006;Ho et al 2014;Yoon and Heo 1992). Mainly in physisorption, high pressure is used to push gas molecules to have contact at binding sites on the surface and pores of solid matrices that enhance the adsorption capacity (Anson et al 2004).…”

“…Contrary to carbonaceous material-based adsorbents and MOFs, the CO 2 adsorption capacity of zeolites increases with the limited increase in the adsorption temperature. The reason of elevated CO 2 uptake is the opening and enlargement of pores in zeolites with moderately high adsorption temperature (Ho et al 2014;Yoon and Heo 1992). The study of zeolites revealed that there are 50 types of natural and 150 types of synthetic zeolites.…”