Evaluation of carbon dioxide–nitrogen separation through fixed bed measurements and simulations

The increasing emissions of carbon dioxide have been pointed out as a major cause for global warming, as a consequence of the intensification of the greenhouse effect in our planet. Therefore, technologies of carbon capture and storage (CCS) have been developed with the purpose of reducing the concentration of CO₂ in gas emissions (flue gas). Thus, adsorption-based methods are a very promising cost-efficient technology, particularly in processes such as pressure swing adsorption (PSA). The knowledge of adsorption dynamics in fixed bed is of essential importance for the design of industrial scale units. The objective of the present work is to evaluate the suitability of activated carbons (AC) and metal organic-frameworks (MOF) samples for CO₂ capture by measuring multicomponent breakthrough curves. CO₂–N₂ systems have been studied for this purpose and a model based on the linear driving force (LDF) approximation for the mass transfer was developed to simulate breakthrough curves under the same experimental conditions. The selectivity of the samples for the adsorption of CO₂ over N₂ was also evaluated and compared. Results suggest that the AC C141 has a great potential for the separation of CO₂ from N₂ at 348 K, since it presents a comparable selectivity (6.2) to the MOF sample Cu-BTC (8.0), and it is much more stable to contaminants present in flue gas scenarios, particularly water vapor. This may be explained by its narrow microporosity as compared to the other activated carbon samples. Despite the high microprosity, sample AC C141 also showed the fastest intraparticle kinetics (D _c /r _c ²  ≈ 6.0 × 10⁻² s⁻¹), which suits it for fast adsorption/desorption cycles as in PSA plants.