This study showed that a solid amine, composed of poly(ethylenimine) immobilized into a CARiACT G10 silica substrate, is a feasible sorbent for applications in a pressure swing adsorption (PSA) process for postcombustion CO2 capture. This deduction materialized from an extensive study of the behavior of this material over a wide range of industrially relevant conditions using thermogravimetric analysis. The temperature ranged from 40 to 100 °C, the CO2 partial pressure ranged from 1.2 to 100 vol % with the total pressure fixed at 1 atm, the relative humidity ranged from dry conditions to 2 vol %, and the number of consecutive adsorption and desorption cycles ranged from 4 to 76. The results revealed that this solid amine sorbent was very stable under the conditions investigated. Water vapor at a low relative humidity exhibited only a minor and reversible effect on both the thermodynamics and kinetics of the CO2 uptake and release. The isothermal CO2 working capacity ranged between 0.25 and 2.8 mol/kg, increased with increasing CO2 concentration, exhibited a maximum with increasing temperature, and produced a heat of adsorption/reaction of around 50.0 kJ/mol. It was also determined that the optimal operating temperature for a PSA process was around 80 °C for CO2 partial pressures >10 kPa and 60−70 °C for CO2 partial pressures <10 kPa.

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This paper reports the results of an international interlaboratory study led by the National Institute of Standards and Technology (NIST) on the measurement of high-pressure surface excess methane adsorption isotherms on NIST Reference Material RM 8850 (Zeolite Y), at 25 °C up to 7.5 MPa. Twenty laboratories participated in the study and contributed over one-hundred adsorption isotherms of methane on Zeolite Y. From these data, an empirical reference equation was determined, along with a 95% uncertainty interval (Uk=2). By requiring participants to replicate a high-pressure reference isotherm for carbon dioxide adsorption on NIST Reference Material RM 8852 (ZSM-5), this interlaboratory study also demonstrated the usefulness of reference isotherms in evaluating the performance of high-pressure adsorption experiments.

Polypyrrole nanostructures with diameters s 10 nm have been electropolymerized using step and pit defects on highly ordered pyrolytic graphite (HOPG) as templates for electropolymerization. Step defects were naturally occurring, and pits were formed via oxidation of freshly cleaved surfaces of an HOPG wafer by heating at -640°C. Underpotential deposition of approximately -80 mV caused polypyrrole to form only on the step and pit edges of HOPG at and not on the basal plane. The size of these nanostructures could be controlled by limiting the pyrrole polymerization time at anodic potentials. Recent modeling results allow the morphology of the deposition to be inferred, and we find the electrochemical data consistent with wire-shaped growth for up to 30 s at constant potential, after which the growth changes morphology. Scanning tunneling microscopy data confirm this result. Preliminary studies show that these polypyrrole nanostructures can be removed by sonication.

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