The Importance of Precursors and Modification Groups of Aerogels in CO2 Capture

Investigation of palladium catalysts in mesoporous silica support for CO oxidation and CO2 adsorption

The oxidation of Carbon monoxide (CO) to Carbon dioxide (CO2) is one of the most extensively investigated reactions in the field of heterogeneous catalysis, and it occurs via molecular rearrangements induced by catalytic metal atoms with oxygen intermediates. CO oxidation and CO2 capture are instrumental processes in the reduction of green-house gas emissions, both of which are used in low-temperature CO oxidation in the catalytic converters of vehicles. CO oxidation and CO2 adsorption at different temperatures are evaluated for palladium-supported silica aerogel (Pd/SiO2). The synthesized catalyst was active and stable for low-temperature CO oxidation. The catalytic activity was enhanced after the first cycle due to the reconditioning of the catalyst's pores. It was found that the presence of oxide forms of palladium in the SiO2 microstructure, influences the performance of the catalysts due to oxygen vacancies that increases the frequency of active sites. CO2 gas adsorption onto Pd/SiO2 was investigated at a wide-ranging temperature from 16 to 120 °C and pressures ∼1 MPa as determined from the isotherms that were evaluated, where CO2 showed the highest equilibrium adsorption capacity at 16 °C. The Langmuir model was employed to study the equilibrium adsorption behavior. Finally, the effect of moisture on CO oxidation and CO2 adsorption was considered to account for usage in real-world applications. Overall, mesoporous Pd/SiO2 aerogel shows potential as a material capable of removing CO from the environment and capturing CO2 at low temperatures.

Manufacturing silica aerogel and cryogel through ambient pressure and freeze drying

Achieving a mesoporous structure in superinsulation materials is pivotal for guaranteeing a harmonious relationship between low thermal conductivity, high porosity, and low density. Herein, we report silica-based cryogel and aerogel materials by implementing freeze-drying and ambient-pressure-drying processes respectively. The obtained freeze-dried cryogels yield thermal conductivity of 23 mW m⁻¹ K⁻¹, with specific surface area of 369.4 m² g⁻¹, and porosity of 96.7%, whereas ambient-pressure-dried aerogels exhibit thermal conductivity of 23.6 mW m⁻¹ K⁻¹, specific surface area of 473.8 m² g⁻¹, and porosity of 97.4%. In addition, the fiber-reinforced nanocomposites obtained via freeze-drying feature a low thermal conductivity (28.0 mW m⁻¹ K⁻¹) and high mechanical properties (∼620 kPa maximum compressive stress and Young's modulus of 715 kPa), coupled with advanced flame-retardant capabilities, while the composite materials from the ambient pressure drying process have thermal conductivity of 28.8 mW m⁻¹ K⁻¹, ∼200 kPa maximum compressive stress and Young's modulus of 612 kPa respectively. The aforementioned results highlight the capabilities of both drying processes for the development of thermal insulation materials for energy-efficient applications.

Ambient pressure and freeze drying techniques enable silica aerogel and cryogel insulation composites.

Valorization of Starch to Biobased Materials: A Review

Many concerns are being expressed about the biodegradability, biocompatibility, and long-term viability of polymer-based substances. This prompted the quest for an alternative source of material that could be utilized for various purposes. Starch is widely used as a thickener, emulsifier, and binder in many food and non-food sectors, but research focuses on increasing its application beyond these areas. Due to its biodegradability, low cost, renewability, and abundance, starch is considered a "green path" raw material for generating porous substances such as aerogels, biofoams, and bioplastics, which have sparked an academic interest. Existing research has focused on strategies for developing biomaterials from organic polymers (e.g., cellulose), but there has been little research on its polysaccharide counterpart (starch). This review paper highlighted the structure of starch, the context of amylose and amylopectin, and the extraction and modification of starch with their processes and limitations. Moreover, this paper describes nanofillers, intelligent pH-sensitive films, biofoams, aerogels of various types, bioplastics, and their precursors, including drying and manufacturing. The perspectives reveal the great potential of starch-based biomaterials in food, pharmaceuticals, biomedicine, and non-food applications.

A Systematic Review of Amino Acid-Based Adsorbents for CO2 Capture

The rise of carbon dioxide (CO2) levels in the atmosphere emphasises the need for improving the current carbon capture and storage (CCS) technology. A conventional absorption method that utilises amine-based solvent is known to cause corrosion to process equipment. The solvent is easily degraded and has high energy requirement for regeneration. Amino acids are suitable candidates to replace traditional alkanolamines attributed to their identical amino functional group. In addition, amino acid salt is a green material due to its extremely low toxicity, low volatility, less corrosive, and high efficiency to capture CO2. Previous studies have shown promising results in CO2 capture using amino acids salts solutions and amino acid ionic liquids. Currently, amino acid solvents are also utilised to enhance the adsorption capacity of solid sorbents. This systematic review is the first to summarise the currently available amino acid-based adsorbents for CO2 capture using PRISMA method. Physical and chemical properties of the adsorbents that contribute to effective CO2 capture are thoroughly discussed. A total of four categories of amino acid-based adsorbents are evaluated for their CO2 adsorption capacities. The regeneration studies are briefly discussed and several limitations associated with amino acid-based adsorbents for CO2 capture are presented before the conclusion.

The AEROPILs Generation: Novel Poly(Ionic Liquid)-Based Aerogels for CO2 Capture

CO₂ levels in the atmosphere are increasing exponentially. The current climate change effects motivate an urgent need for new and sustainable materials to capture CO₂. Porous materials are particularly interesting for processes that take place near atmospheric pressure. However, materials design should not only consider the morphology, but also the chemical identity of the CO₂ sorbent to enhance the affinity towards CO₂. Poly(ionic liquid)s (PILs) can enhance CO₂ sorption capacity, but tailoring the porosity is still a challenge. Aerogel’s properties grant production strategies that ensure a porosity control. In this work, we joined both worlds, PILs and aerogels, to produce a sustainable CO₂ sorbent. PIL-chitosan aerogels (AEROPILs) in the form of beads were successfully obtained with high porosity (94.6–97.0%) and surface areas (270–744 m²/g). AEROPILs were applied for the first time as CO₂ sorbents. The combination of PILs with chitosan aerogels generally increased the CO₂ sorption capability of these materials, being the maximum CO₂ capture capacity obtained (0.70 mmol g⁻¹, at 25 °C and 1 bar) for the CHT:P[DADMA]Cl_30%AEROPIL.