Control of the pore size distribution and its spatial homogeneity in particulate activated carbon

Abstract

There are circumstances where it is desirable to achieve a particular, optimal, pore size distribution (PSD) in a carbon, including in the molecular sieving, gas storage, CO 2 -capture and electrochemical energy storage.Activation protocols that cycle a carbon a number of times between a lowtemperature oxygen chemisorption process and a higher temperature pyrolysis process have been proposed as a means of yielding such desired PSDs. However, it is shown here that for PFA-based char particles of ~100 μ m in size, only the super-micropores are substantially developed under such an activation protocol, with the ultra-micropores being substantially un-touched. It is also shown that a typical CO 2 -activation process yields similar control over PSD development. As this process is nearly 15 times faster than the cyclic-O 2 protocol and yields larger pore volumes and areas for a given level of conversion, it is to be preferred unless spatial homogeneous porosity within the particles is also desired. If such homogeneity is desired, it is shown here that CO 2 activation should continue to be used but at a rate of around one-tenth the typical; this slow rate also has the advantage of producing pore volumes and areas substantially greater than those obtained using the other activation protocols.

Analysis of Adsorbate–Adsorbate and Adsorbate–Adsorbent Interactions to Decode Isosteric Heats of Gas Adsorption

“…A poly(furfuryl alcohol)‐based carbon was used in this study as the adsorbent. The synthesis and activation procedures are described in detail elsewhere . In summary, distilled furfuryl alcohol was mixed at room temperature with oxalic acid as a mass ratio of 100:3.…”

“…The resulting chars were ground and sieved (100 μm), and then activated using repeated cycles of oxygen chemisorption (250 °C, 8 h) followed by desorption under argon (800 °C, 2 h). The sample used in the current work received nine such cycles, equivalent to 45 % burn‐off, resulting in a BET equivalent surface area of 950 m 2 g −1 and a pore volume of 0.37 cm 3 g −1 …”

Raman spectroscopy study of the transformation of the carbonaceous skeleton of a polymer-based nanoporous carbon along the thermal annealing pathway

“…In order to reduce as much as possible experimental uncertainties, the base carbon studied here, termed C45SCO 2 hereafter [44], was derived from a furfuryl alcohol (FA) precursor using a carefully controlled process.…”

A multi-method study of the transformation of the carbonaceous skeleton of a polymer-based nanoporous carbon along the activation pathway

“…The full details of the synthesis process may be found elsewhere [54] Previous work by us [54,56] has demonstrated that both the porosity and chemistry, a summary of which may be found in Fig. 1 and Table 1, is homogeneous within the particles.…”