Activated carbon monoliths for gas storage at room temperature

Abstract

Porous materials are interesting candidates for gas storage in different applications. The present study analyses at room temperature the high pressure storage of H 2 , CH 4 and CO 2 in a number of porous carbons (eight monoliths and two powdered activated carbons). The samples cover a wide range of porosities and densities (monoliths having high porosity with moderate density or moderate porosity with high density) with the aim to discuss the relative importance that the sample surface area has on the volumetric storage capacity, in relation to the importance of the density of the material. Our results show that the gravimetric storage capacities of the three studied gases are controlled by the textural properties of the adsorbent, whereas the volumetric storage capacities are mainly controlled by the adsorbent density. High volumetric excess adsorption capacity values (for example, H 2 : 10 g l À1 ; CH 4 : 110 g l À1 and CO 2 : 440 g l À1 ) correspond to monoliths having high densities, despite their moderately developed porosities. This paper also compares these results with those obtained similarly (same gases and same experimental conditions) using the highest known surface area material (MOF-210). In summary, our volumetric results, obtained with commercially available ATMI monoliths and their CO 2 activation, are, to the best of our knowledge, amongst the highest that have been reported; higher than the high surface area samples of the M3M monolith prepared from Maxsorb (S BET : 2610 m 2 g À1 ) or MOF-210 (S BET : 6240 m 2 g À1 ). Although a variety of MOFs have been reported to exceed our results, oftentimes these values are overestimated due to the fact that the volumetric capacity of MOFs was calculated using crystal density rather than experimentally measured density.

Adsorbent density impact on gas storage capacities

“…A maximum of 1 g cm −3 was chosen, because such value can be regarded as a realistic stateof-the-art maximum density for porous carbon materials. Thus, recently adsorption of H 2 , CH 4 , and CO 2 on monoliths with such high density has been reported [4]. Similar to the representation in Figure 3, the adsorption isotherms and the total storage capacities are shown on a volumetric basis (see Figure 4(a)), and on a gravimetric basis (Figure 4(b)).…”

“…Porous materials like activated or templated carbons [1][2][3][4], metal-organic frameworks (MOFs) [5,6], covalent organic frameworks (COFs) [7], etc. are interesting candidates for gas storage application [8][9][10].…”

Activated Carbon Fibre Monoliths for Hydrogen Storage

“…Thus, the packing density of the adsorbent affects directly the excess adsorption on a volumetric basis. Furthermore, and even more important from an application point of view, the adsorbent density is a key factor which controls the total quantity of hydrogen that can be stored in a given volume [4,15,20,25]. This is especially important for hydrogen storage at room temperature, where the contribution of the compressed hydrogen in the void space is considerable and has to be taken into account [4,25].…”

“…In our previous works, it was demonstrated that the density of the adsorbent is a critical parameter for hydrogen storage application by physisorption [4][5][6]15,17,22,23,25]. Thus, the packing density of the adsorbent affects directly the excess adsorption on a volumetric basis.…”

“…More recently, the storage interest has also reached carbon dioxide in relation to environmental applications (capture and transportation) [1][2][3][4][5][6]. Among these three gases, the storage of hydrogen is the most difficult task, due to its special physical and chemical characteristics [7,8].…”