Analyzing High-Pressure CO2 Capture on Porous Carbons

The High-Pressure Volumetric Analyzer (HPVA) can be used to determine the adsorption and desorption isotherms of metal-organic frameworks (MOFs), carbons, and other materials using a variety of gases at pressures of up to 200 bar.

High-Pressure Volumetric Analyzer

One use of the HPVA which is particularly pertinent in the modern age is measuring carbon dioxide capture by carbon materials, which can be used to help design greener manufacturing processes.

Carbon materials can be used to form stack scrubbers that capture the carbon dioxide produced by the combustion of fossil fuels in power plants or produced by chemical processes in refineries.

In addition, the HPVA’s high-pressure capability means it can be used to simulate the underground, high-pressure conditions of possible carbon sequestration locations.

Carbon Dioxide Determination Using HPVA

The HPVA was used to determine the amount of CO₂ that could be adsorbed onto two different porous carbon materials, Ultra Microporous Carbon (UMC) and Carbosieve S-III, at pressures of up to 40 bar.

The carbon sample was held in a sample tube that was installed onto the HPVA’s degas port and then evacuated under vacuum and heated to a temperature of 350 °C. The sample was held at this temperature for 20 hours to ensure that all residual adsorbed gas and water was removed.

Following 20 hours, the sample was allowed to cool down to room temperature and moved to the HPVA’s analysis port. The sample stem has an isolation valve which prevents any water vapor or atmospheric gas from contaminating the sample following degassing.

Once in the sample port, the carbon materials were analyzed at three different temperatures (30 °C, 50 °C, and 70 °C) that were held constant within ± 0.1 °C using a re-circulating temperature control bath and an integrated RTD. Each isotherm took around 24 hours to collect. Figure 1 and Figure 2 show the isotherms once they had been collected.

Figure 1. The carbon dioxide excess adsorption/desorption isotherms of carbon S-III. For differentiation purposes, the desorption curve is a lighter shade than the adsorption curve

Figure 2. The carbon dioxide excess adsorption/desorption isotherms of Ultra Microporous Carbon (UMC). For differentiation purposes, the desorption curve is a lighter shade than the adsorption curve

The compressibility factor (z) of carbon dioxide, as a function of pressure and temperature, is used as part of the volumetric calculations to account for the non-ideal behavior of carbon dioxide. The National Institute of Standards and Technology (NIST) Reference Fluid Thermodynamic and Transport Properties Database (REFPROP), Version 8.0, 2007, was used to determine the value of the compressibility factor at each pressure and temperature point.

This information has been sourced, reviewed and adapted from materials provided by Micromeritics Instrument Corporation.

For more information on this source, please visit Micromeritics Instrument Corporation.