Comparison of commercial and new adsorbent materials for precombustion CO₂ capture by pressure swing adsorption

The IGCC technology (Integrated Gasification Combined Cycle) with pre-combustion CO₂ capture is a promising approach for near-zero CO₂ emission power plants to be realized in the near future. A key challenge within this technology is the separation of the CO₂/H₂ gas mixture resulting from the water gas shift reaction that follows the gasification of coal. For the CO₂ stream a purity of about 95% is required; additionally a CO₂ capture rate of 90% is desired, which implies that both streams, H₂ and CO₂, are required at rather high purity (∼95%). In contrast to post- combustion capture from power plants, where a large gas stream at low pressure and low CO₂ content has to be treated, in pre-combustion capture a gas mixture at up to 40 bar has to be separated; therefore an adsorption based process, such as pressure swing adsorption (PSA), constitutes a promising method for CO₂ removal from H₂.

In this work, new materials, namely USO-2-Ni MOF, UiO-67/MCM-41 Hybrid and MCM-41, are characterized in terms of equilibrium adsorption isotherms. Excess adsorption isotherms of CO₂ and H₂ on these materials are measured at different temperatures (25 °C 140 °C) and in a wide pressure range (up to 150 bar). The experimental data are then described with a suitable isotherm model, in our case Langmuir, Sips and Quadratic. In addition, the cyclic working capacity of CO₂ on each material is computed as a further assessment of the suitability of these materials for pre-combustion capture.