Characterization of Micro- and Mesoporous Materials
Using Accelerated Dynamics Adsorption
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Abstract
Porosimetry
is a fundamental characterization technique used in
development of new porous materials for catalysis, membrane separation,
and adsorptive gas storage. Conventional methods like nitrogen and
argon adsorption at cryogenic temperatures suffer from slow adsorption
dynamics especially for microporous materials. In addition, CO<sub>2</sub>, the other common probe, is only useful for micropore characterization
unless being compressed to exceedingly high pressures to cover all
required adsorption pressures. Here, we investigated the effect of
adsorption temperature, pressure, and type of probe molecule on the
adsorption dynamics. Methyl chloride (MeCl) was used as the probe
molecule, and measurements were conducted near room temperature under
nonisothermal condition and subatmospheric pressure. A pressure control
algorithm was proposed to accelerate adsorption dynamics by manipulating
the chemical potential of the gas. Collected adsorption data are transformed
into pore size distribution profiles using the Horvath–Kavazoe
(HK), Saito–Foley (SF), and modified Kelvin methods revised
for MeCl. Our study shows that the proposed algorithm significantly
speeds up the rate of data collection without compromising the accuracy
of the measurements. On average, the adsorption rates on carbonaceous
and aluminosilicate samples were accelerated by at least a factor
of 4–5