A dynamic column breakthrough apparatus for adsorption capacity measurements with quantitative uncertainties

Improved Apparatus for Dynamic Column Breakthrough Measurements Relevant to Direct Air Capture of CO2

Dynamic column breakthrough (DCB) measurements are valuable for characterizing the adsorption of gaseous species by solid sorbents and are typically used for high concentrations of adsorptives, often at elevated temperatures and pressures. However, adsorbents for the direct capture of carbon dioxide from natural air demand measurement capability at low partial pressures of CO2 at atmospherically relevant temperatures and pressures. We have developed a new apparatus focused on the measurement of DCB curves under typical tropospheric conditions. The new apparatus is described in detail and validated with breakthrough curve measurements. Adsorption capacities are reported at (233.1 to 323.1) K and (351 to 1078) hPa for low carbon dioxide concentrations on 13X zeolite samples on the order of a few hundred milligrams. Measurement uncertainties related to timing, flow, temperature, and concentrations are analyzed and the present results at 273 K, 298 K, and 323 K are compared with static measurements obtained with a manometric adsorption analyzer. In addition, experiments at a typical atmospheric CO2 concentration of 400 μL · L-1 have been performed.

System and Processes of Pre-combustion Carbon Dioxide Capture and Separation

In this chapter, the development of H2/CO2 separation technology, including a new CO2 chemical adsorbent, a pressure swing adsorption (PSA) reactor model, and the continuous operation of a pilot-scale test system for pre-combustion CO2 capture, are presented. Potassium-promoted Mg–Al layered double oxides (LDOs) are shown to be appropriate candidate adsorbents for elevated temperature (250–450 °C) PSA for pre-combustion H2/CO2 separation. The adsorption heat of CO2 on the surface of LDOs is only 2.5–60.4 kJ mol−1, which is beneficial for achieving isothermal desorption by a pressure swing. Further, methods for enhancing the CO2 capacity and the mechanical strength of adsorbent pellets are introduced. The single- and double-column fixed-bed experiments provided useful results for the development and validation of scalable modeling. The PSA model was built by coupling a non-equilibrium kinetic adsorption model and a column model. The effects of operating parameters on the H2 recovery ratio and CO2 capture ratio were studied. A 4-column pilot-scale elevated temperature PSA (ET-PSA) system was developed with a processing capacity of 4.0–6.6 Nm3 h−1 to determine the feasibility of such a system for industrial application. It achieved 1089 h of accumulated operation and 75 h of continuous operation, maintaining a CO2 removal ratio higher than 91.7%.

Effective Approach for Increasing the Heteroatom Doping Levels of Porous Carbons for Superior CO2 Capture and Separation Performance

Development of efficient sorbents for carbon dioxide (CO₂) capture from flue gas or its removal from natural gas and landfill gas is very important for environmental protection. A new series of heteroatom-doped porous carbon was synthesized directly from pyrazole/KOH by thermolysis. The resulting pyrazole-derived carbons (PYDCs) are highly doped with nitrogen (14.9-15.5 wt %) as a result of the high nitrogen-to-carbon ratio in pyrazole (43 wt %) and also have a high oxygen content (16.4-18.4 wt %). PYDCs have a high surface area (SA_BET = 1266-2013 m² g^-1), high CO₂ Q_st (33.2-37.1 kJ mol^-1), and a combination of mesoporous and microporous pores. PYDCs exhibit significantly high CO₂ uptakes that reach 2.15 and 6.06 mmol g^-1 at 0.15 and 1 bar, respectively, at 298 K. At 273 K, the CO₂ uptake improves to 3.7 and 8.59 mmol g^-1 at 0.15 and 1 bar, respectively. The reported porous carbons also show significantly high adsorption selectivity for CO₂/N₂ (128) and CO₂/CH₄ (13.4) according to ideal adsorbed solution theory calculations at 298 K. Gas breakthrough studies of CO₂/N₂ (10:90) at 298 K showed that PYDCs display excellent separation properties. The ability to tailor the physical properties of PYDCs as well as their chemical composition provides an effective strategy for designing efficient CO₂ sorbents.

Application of a high-throughput analyzer in evaluating solid adsorbents for post-combustion carbon capture via multicomponent adsorption of CO2, N2, and H2O

Despite the large number of metal-organic frameworks that have been studied in the context of post-combustion carbon capture, adsorption equilibria of gas mixtures including CO2, N2, and H2O, which are the three biggest components of the flue gas emanating from a coal- or natural gas-fired power plant, have never been reported. Here, we disclose the design and validation of a high-throughput multicomponent adsorption instrument that can measure equilibrium adsorption isotherms for mixtures of gases at conditions that are representative of an actual flue gas from a power plant. This instrument is used to study 15 different metal-organic frameworks, zeolites, mesoporous silicas, and activated carbons representative of the broad range of solid adsorbents that have received attention for CO2 capture. While the multicomponent results presented in this work provide many interesting fundamental insights, only adsorbents functionalized with alkylamines are shown to have any significant CO2 capacity in the presence of N2 and H2O at equilibrium partial pressures similar to those expected in a carbon capture process. Most significantly, the amine-appended metal organic framework mmen-Mg2(dobpdc) (mmen = N,N'-dimethylethylenediamine, dobpdc (4-) = 4,4'-dioxido-3,3'-biphenyldicarboxylate) exhibits a record CO2 capacity of 4.2 ± 0.2 mmol/g (16 wt %) at 0.1 bar and 40 °C in the presence of a high partial pressure of H2O.