Desorption Process for Capturing CO2 from Air with Supported Amine Sorbent

Carbon Capture: Theoretical Guidelines for Activated Carbon-Based CO2 Adsorption Material Evaluation

Activated carbon (AC)-based materials have shown promising performance in carbon capture, offering low cost and sustainable sourcing from abundant natural resources. Despite ACs growing as a new class of materials, theoretical guidelines for evaluating their viability in carbon capture are a crucial research gap. We address this gap by developing a hierarchical guideline, based on fundamental gas-solid interaction strength, that underpins the success and scalability of AC-based materials. The most critical performance indicator is the CO2 adsorption energy, where an optimal range (-0.41 eV) ensures efficiency between adsorption and desorption. Additionally, we consider thermal stability and defect sensitivity to ensure consistent performance under varying conditions. Further, selectivity and capacity play significant roles due to external variables such as partial pressure of CO2 and other ambient air gases (N2, H2O, O2), bridging the gap between theory and reality. We provide actionable examples by narrowing our options to methylamine- and pyridine-grafted graphene.

Emerging trends in direct air capture of CO2: a review of technology options targeting net-zero emissions

The increasing concentration of carbon dioxide (CO2) in the atmosphere has compelled researchers and policymakers to seek urgent solutions to address the current global climate change challenges. In order to keep the global mean temperature at approximately 1.5 °C above the preindustrial era, the world needs increased deployment of negative emission technologies. Among all the negative emissions technologies reported, direct air capture (DAC) is positioned to deliver the needed CO2 removal in the atmosphere. DAC technology is independent of the emissions origin, and the capture machine can be located close to the storage or utilization sites or in a location where renewable energy is abundant or where the price of energy is low-cost. Notwithstanding these inherent qualities, DAC technology still has a few drawbacks that need to be addressed before the technology can be widely deployed. As a result, this review focuses on emerging trends in direct air capture (DAC) of CO2, the main drivers of DAC systems, and the required development for commercialization. The main findings point to undeniable facts that DAC's overall system energy requirement is high, and it is the main bottleneck in DAC commercialization.

Review on CO2 Capture Using Amine-Functionalized Materials

CO₂ capture from industry sectors or directly from the atmosphere is drawing much attention on a global scale because of the drastic changes in the climate and ecosystem which pose a potential threat to human health and life on Earth. In the past decades, CO₂ capture technology relied on classical liquid amine scrubbing. Due to its high energy consumption and corrosive property, CO₂ capture using solid materials has recently come under the spotlight. A variety of porous solid materials were reported such as zeolites and metal-organic frameworks. However, amine-functionalized porous materials outperform all others in terms of CO₂ adsorption capacity and regeneration efficiency. This review provides a brief overview of CO₂ capture by various amines and mechanistic aspects for newcomers entering into this field. This review also covers a state-of-the-art regeneration method, visible/UV light-triggered CO₂ desorption at room temperature. In the last section, the current issues and future perspectives are summarized.

Recent advances in direct air capture by adsorption

Significant progress has been made in direct air capture (DAC) in recent years. Evidence suggests that the large-scale deployment of DAC by adsorption would be technically feasible for gigatons of CO₂ capture annually. However, great efforts in adsorption-based DAC technologies are still required. This review provides an exhaustive description of materials development, adsorbent shaping, in situ characterization, adsorption mechanism simulation, process design, system integration, and techno-economic analysis of adsorption-based DAC over the past five years; and in terms of adsorbent development, affordable DAC adsorbents such as amine-containing porous materials with large CO₂ adsorption capacities, fast kinetics, high selectivity, and long-term stability under ultra-low CO₂ concentration and humid conditions. It is also critically important to develop efficient DAC adsorptive processes. Research and development in structured adsorbents that operate at low-temperature with excellent CO₂ adsorption capacities and kinetics, novel gas-solid contactors with low heat and mass transfer resistances, and energy-efficient regeneration methods using heat, vacuum, and steam purge is needed to commercialize adsorption-based DAC. The synergy between DAC and carbon capture technologies for point sources can help in mitigating climate change effects in the long-term. Further investigations into DAC applications in the aviation, agriculture, energy, and chemical industries are required as well. This work benefits researchers concerned about global energy and environmental issues, and delivers perspective views for further deployment of negative-emission technologies.

Modeling of Vacuum Temperature Swing Adsorption for Direct Air Capture Using Aspen Adsorption

The paper evaluates the performance of an adsorption-based technology for CO2 capture directly from the air at the industrial scale. The approach is based on detailed mass and energy balance dynamic modeling of the vacuum temperature swing adsorption (VTSA) process in Aspen Adsorption software. The first step of the approach aims to validate the modeling thanks to published experimental data for a lab-scale bed module in terms of mass transfer and energy performance on a packed bed using amine-functionalized material. A parametric study on the main operating conditions, i.e., air velocity, air relative moisture, air temperature, and CO2 capture rate, is undertaken to assess the global performance and energy consumption. A method of up-scaling the lab-scale bed module to industrial module is exposed and mass transfer and energy performances of the industrial module are provided. The scale up from lab scale to the industrial size is conservative in terms of thermal energy consumption while the electrical consumption is very sensitive to the bed design. Further study related to the engineering solutions available to reach high global gas velocity are required. This could be offered by monolith-shape adsorbents.

Effect of Extended Aging and Oxidation on Linear Poly(propylenimine)-Mesoporous Silica Composites for CO2 Capture from Simulated Air and Flue Gas Streams

Physical aging or degradation of amine-containing polymers and supported amine adsorbents is a critical issue that could limit the practical application of such materials for CO₂ capture. However, to date, there is a scarcity of studies that evaluate the long-term stability of amine-based sorbents without the exclusive use of accelerated aging tests. Here, we demonstrate that extended aging (∼2 years) of linear poly(propylenimine) (LPPI) confined in mesoporous silica (SBA-15) supports does not drastically impact the CO₂ adsorption performance under simulated flue gas (10% CO₂) and direct air capture (DAC, 400 ppm CO₂) conditions, although the behavior of the aged sorbents and polymers in the two CO₂ concentration regimes differs. The sorbents made with aged LPPI have modestly decreased CO₂ uptake performance (≲20% lower) compared to the fresh polymers, with overall good CO₂ cycling performance. The data indicate that only slow degradation occurs under the deployed ambient storage conditions. Even after extended aging, the LPPI-based sorbents preserved their ability to display stable temperature-swing cycling performance. In parallel, the impact of blending LPPI polymers of different number-average molecular weights, M_n, is evaluated, seeking to understand its impact on adsorbent performance. The results demonstrate that the blends of two M_n aged LPPI give similar CO₂ adsorption performance to adsorbents made from a single-M_n LPPI, suggesting that molecular weight will not negatively impact adsorbent performance in the studied M_n range. After an accelerated oxidation experiment, the aged LPPI sorbents retained a larger portion of the samples' original performance when cycling under simulated flue gas conditions than under DAC conditions. However, in each case, the oxidized sorbents could be cycled repeatedly with consistent uptake performance. Overall, these first of their kind extended aging tests suggest that LPPI-based amine adsorbents offer promise for long-term, stable use in carbon capture applications.