A Highly Tunable Approach to Enhance CO2 Capture with Liquid Alkali/amines

CO2-responsive gels

CO₂-responsive materials undergo a change in chemical or physical properties in response to the introduction or removal of CO₂. The use of CO₂ as a stimulus is advantageous as it is abundant, benign, inexpensive, and it does not accumulate in a system. Many CO₂-responsive materials have already been explored including polymers, latexes, surfactants, and catalysts. As a sub-set of CO₂-responsive polymers, the study of CO₂-responsive gels (insoluble, cross-linked polymers) is a unique discipline due to the unique set of changes in the gels brought about by CO₂ such as swelling or a transformed morphology. In the past 15 years, CO₂-responsive gels and self-assembled gels have been investigated for a variety of emerging potential applications, reported in 90 peer-reviewed publications. The two most widely exploited properties include the control of flow (fluids) via CO₂-triggered aggregation and their capacity for reversible CO₂ absorption-desorption, leading to applications in Enhanced Oil Recovery (EOR) and CO₂ sequestration, respectively. In this paper, we review the preparation, properties, and applications of these CO₂-responsive gels, broadly classified by particle size as nanogels, microgels, aerogels, and macrogels. We have included a section on CO₂-induced self-assembled gels (including poly(ionic liquid) gels).

A Review on Carbon Dioxide Minimization in Biogas Upgradation Technology by Chemical Absorption Processes

With an ever-increasing population and unpredictable climate changes, meeting energy demands and maintaining a sustainable environment on Earth are two of the greatest challenges of the future. Biogas can be a very significant renewable source of energy that can be used worldwide. However, to make it usable, upgrading the gas by removing the unwanted components is a very crucial step. CO₂ being one of the major unwanted components and also being a major greenhouse gas must be removed efficiently. Different methods such as physical adsorption, cryogenic separation, membrane separation, and chemical absorption have been discussed in detail in this review because of their availability, economic value, and lower environmental footprint. Three chemical absorption methods, including alkanolamines, alkali solvents, and amino acid salt solutions, are discussed. Their primary works with simple chemicals along with the latest works with more complex chemicals and different mechanical processes, such as the DECAB process, are discussed and compared. These discussions provide valuable insights into how different processes vary and how one is more advantageous or disadvantageous than the others. However, the best method is yet to be found with further research. Overall, this review emphasizes the need for biogas upgrading, and it discusses different methods of carbon capture while doing that. Methods discussed here can be a basic foundation for future research in carbon capture and green chemistry. This review will enlighten the readers about scientific and technological challenges regarding carbon dioxide minimization in biogas technology.

Catalyst-free development of N-doped microporous carbons for selective CO2 separation

Owing to their catalyst-free development, high yield, notable CO₂ uptake performance, and excellent CO₂/CH₄ selectivity, the fabricated N-doped microporous carbons (NMCs) are highly suitable for selective CO₂ separation.

Silica-Supported Nitrogen-Enriched Porous Benzimidazole-Linked and Triazine-Based Polymers for the Adsorption of CO2

Two crystalline and five amorphous benzimidazole polymers (BINP) were synthesized and conjugated to porous silica via amine and aldehyde-based materials by a simple reflux procedure. The resulting polymers were subject to thermal analysis for monitoring and quantification of the adsorption and desorption of CO₂. All the polymers were capable of adsorbing CO₂ from a flowing stream of only 80 mL/min at 25 °C. The adsorbed CO₂ onto the polymers were effectively desorbed at room temperature, illustrating the potential application of such polymers for repeated adsorption/desorption of CO₂. The CO₂ adsorption capacities of these polymers were dependent upon their nitrogen content, specific surface area, and pore size. The available nitrogen atoms for binding to the carbon of CO₂ via tetrel bonds also plays an important role in the capture of this gas. Minimal and much lower CO₂ adsorption was also noted with two crystalline polymers, compared to the five amorphous counterparts. Intermolecular hydrogen bonding and π-π interaction effectively prevented the polymer N sites of the crystalline polymers from interacting with polarized CO₂ molecules.

Reducing Energy Penalty of CO2 Capture Using Fe Promoted SO42-/ZrO2/MCM-41 Catalyst

The high energy consumption of CO₂-loaded solvent regeneration is the biggest impediment for the real application of the amine-based CO₂ capture process. To lower the energy requirement, three Fe promoted SO₄^2-/ZrO₂ supported on MCM-41 (SZMF) catalysts with different iron oxide content (5%, 10%, and 15%) were synthesized and applied for the rich monoethanolamine solution regeneration process at 98 °C. Results reveal that the use of SZMF hugely enhanced the CO₂ desorption performances (i.e., desorption factor) by 260-388% and reduced the heat duty by about 28-40%, which is better than most of the reported catalysts for this purpose. The eminent catalytic activities of SZMF are related to their enhanced ratio of Brønsted to Lewis acid sites, weak acid sites, basic sites, and high dispersed Fe³⁺ species. Meanwhile, the addition of SZMF for CO₂ desorption shows a promotional effect on its CO₂ absorption performance, and SZMF presents an excellent cyclic stability. A possible mechanism is suggested for the SZMF catalyzed CO₂ desorption process. Results of this work may provide direction for future research and rational design of more efficient catalysts for this potential catalyst-aided CO₂ desorption technology.