ブルー水素製造における炭素回収促進のための中空糸基板上カーボンキセロゲル吸着材

Unofficial AI-generated summary based on the public title and abstract. Not an official translation.

🔬研究者:カーボンキセロゲルの多成分吸着平衡を熱力学的整合性で扱う手法は、CCUS吸着材研究の比較可能性向上に有用。

🏢実務担当者:ブルー水素プロジェクトの回収率・純度目標設定や吸着材選定の技術的根拠として参照できる。

🏛政策担当者:ブルー水素の低炭素認定やCCS支援策の設計において、回収率・純度の技術的達成可能性を判断する材料になる。

Carbon dioxide emissions from hydrogen production with natural gas ('grey' hydrogen) accounted for up to 1.9% of global emissions in 2024, contributing to climate change that is straining the world's ecosystem. To tackle climate change, several pledges (including the Net Zero emissions by 2050 target and the UAE consensus) were put in place to limit the average global temperature increase by 1.5°C compared to pre-industrial revolution conditions. Despite this, the average global temperature increase was 1.55°C in 2024. Therefore, hydrogen production with fossil fuels, such as natural gas, must be retrofitted with carbon capture technologies. This 'blue' hydrogen production requires CO2 emissions to be captured during processing, ideally aiming for 90% capture and 95% purity. For grey hydrogen production, three capture points have been identified: i) the reformer flue gas; ii) water gas shift reactor syngas; and iii) the hydrogen purification tail gas. Adsorption (gas-solid) separations using supports are attractive for small-scale grey hydrogen production as rapid pressure swing adsorption (PSA) cycling allows for compact carbon capture with fast cycle durations. Adsorption-based carbon capture requires careful adsorbent selection. Carbon xerogels are highly tuneable synthetic carbon-based adsorbents which are promising candidates for carbon capture. However, research on optimising carbon xerogels for CO₂ capture remains extremely limited as thermodynamic consistency has never been adopted and multicomponent adsorption equilibrium data is sparse. This PhD thesis was aimed at developing carbon xerogel adsorbents in order to assess their feasibility in typical carbon capture conditions using thermodynamic consistency for dry multicomponent adsorption conditions. Chapter 1 establishes the background context for climate change, CO₂ emission trends, hydrogen production and the carbon capture technologies available. Chapter 2 formally states the overarching aims and objectives for the specific research covered in Chapters 3, 4, 5 and 6. Chapter 3 investigates the literature surrounding zeolite, metal-organic framework (MOF) and carbon-based adsorbent development with a particular focus on carbon xerogels. Further, Chapter 2 aims to provide a foundational understanding of the adsorption concepts used within this research. Chapter 4 explored the development and characterisation of carbon xerogels. In this chapter, two series of carbon xerogels were developed by varying their thermal treatment conditions (CX and ACX series), and the structural evolution was documented from evidence-based characterisation. This research provided insights into the optimisation of CO₂ adsorption on carbon xerogels based on thermal treatment. The carbon xerogel with the most aggressive thermal treatment (ACX-800) saw a high-pressure limit saturation capacity of 8.67 mol kg-1. However, this also resulted in the lowest adsorption affinity at 273.15 K (0.76 bar-1 and 15.96 bar-1) and heat of adsorption (-33.4 kJ mol-1 and -24.2 kJ mol-1). Alongside the carbon xerogel structure exhibiting pore constrictions at narrow ultramicropore entrances, this research highlighted the balance between improving carbon xerogel saturation capacity and maintaining sufficient adsorption affinity and adsorbate-adsorbent interaction strength. Chapter 5 investigated the multicomponent prediction of the carbon xerogels of the CX and ACX series for the flue gas, syngas and tail gas capture points identified from grey hydrogen production. In this chapter, both the CX and ACX series multicomponent equilibria was predicted for a binary mixture of the flue gas capture point of CO₂ and N₂ where, at 30°C, ACX-800 experienced the highest CO₂ uptake of 0.98 mol kg-1 despite the lowest adsorbed phase mole fraction of 0.826. ACX-800 was then used in a four-component mixture for the syngas and tail gas capture points where, at 30°C, both the CO₂ adsorbed amount (2.99 mol kg-1 and 2.05 mol kg-1 respectively) and adsorbed phase mole fraction (0.948 and 0.929 respectively) improved compared to the flue gas. These findings showed the potential that carbon xerogels have for carbon capture in grey hydrogen processing. Finally, Chapter 6 looked to validate the multicomponent predictions by experimentally measuring the four-component adsorption equilibria on ACX-800 for the three capture points using dynamic breakthrough curve testing with simulations, while maintaining thermodynamic consistency. The experimentally determined and predicted adsorbed amounts agreed well, as did the experimental and simulated breakthrough curve profiles. By analysing the kinetic linear driving force constants (kLDF ), it was found that the constants were 0.08 s-1 and 10 s-1 for the ultramicropore and supermicropore sites respectively, providing further evidence for pore constrictions at the entrances to ultramicropore regions. Further, ACX-800 was successfully impregnated into a ceramic, sandwich-structure hollow fibre module comprised of 24 individual hollow fibres, evidenced by the CO₂ adsorbed amount for the flue gas capture point matching closely between the packed bed of ACX-800 pellets (1.28 ± 0.07 mol kg-1) and the hollow fibre module (1.34 ± 0.01 mol kg-1). Overall, this research establishes the relationship between carbon xerogel development and thermal treatment conditions. Furthermore, the adsorption isotherms of the carbon xerogels developed were modelled with thermodynamic consistency, which was maintained when simulating the experimentally measured dynamic breakthrough curve profiles. As a result, this research serves as the foundation for establishing a fair comparison between carbon xerogels for carbon capture in grey hydrogen production.

• openalex https://doi.org/10.7488/era/7908first seen 2026-10-23 05:17:28 · last seen 2026-11-06 04:52:44