Advances in Amine-Functionalized Adsorbents for Selective CO2 Capture

• Autores: Ali Kasiri
• Directores de la Tesis: Eloy Santiago Sanz Pérez (dir. tes.), Amaya Arencibia Villagrá (codir. tes.)
• Lectura: En la Universidad Rey Juan Carlos ( España ) en 2026
• Idioma: inglés
• Tribunal Calificador de la Tesis: María Erans Moreno (presid.), Pedro Leo LLorente (secret.), Cristina Gutiérrez Muñoz (voc.)
• Programa de doctorado: Programa de Doctorado en Tecnologías Industriales: Química, Ambiental, Energética, Electrónica, Mecánica y de los Materiales por la Universidad Rey Juan Carlos
• Enlaces
  • Tesis en acceso abierto en: www.urjc.es
• Resumen

  • This PhD thesis was conducted at the Department of Chemical, Energy, and Mechanical Technology, Rey Juan Carlos University, under the supervision of Dr. Amaya Arencibia Villagrá and Dr. Eloy Sanz Pérez.The work was supported by an URJC Predoctoral Researcher (Programa Propio 2020) contract and aligned with the research line “Development of materials for CO2 capture,” based at the Móstoles campus, which investigates the development of novel monolithic adsorbents for CO2 capture. With climate change driven by the continuous rise in anthropogenic emissions, carbon capture and sequestration (CCS) technologies are becoming essential for mitigating CO2 emissions from large industrial sources. The goal of this work is to design, synthesize, functionalize, and characterize new materials with enhanced CO2 adsorption properties.

    Within CCS, solid sorbents provide a practical route to capture CO2 with efficient regeneration and straightforward operation, provided that materials can deliver high working capacity at low partial pressures (post-combustion), fast kinetics, durability to cycling, and scalable processes. This dissertation advances two complementary materials platforms, i.e. polymer-rich powders and silica-based monoliths, and four functionalization strategies (polymer cross-linking, covalent grafting, solvent-based impregnation, and double functionalization) to increase usable amine sites while preserving pore connectivity and rapid diffusion.

    The thesis pursued five objectives: (i) to synthesize both polymer-rich powders (e.g., cross-linked EDA-based and PEI-based sorbents) and mesostructured silica monoliths templated with SBA-15, Pluronic P-123, and F-127, including a pore-expansion route; (ii) to introduce amine functionality via polymer cross-linking, covalent grafting (3-aminopropyl-trimethoxysilane (AP), and N1-(3-trimethoxysilylpropyl)-diethylenetriamine (DT)), impregnation (Polyethylenimine (PEI), Tetraethylenepentamine (TEPA)), and double-functionalization; (iii) to carry out structural and chemical characterization (XRD, N2 physisorption, elemental analysis); (iv) to quantify CO2 uptake at 45 °C using thermogravimetric and volumetric analyses; and (v) to evaluate performance under relevant gas compositions (CO2/N2), cycling stability, and regenerability over repeated adsorption- desorption cycles.

    First, polymer-rich powders were prepared: cross-linked ethylenediamine-glutaraldehyde (EDA-based sorbents) materials and PEI modified with methyl acrylate (PEI-based sorbents). Second, silica-based aerogel powders (P100, MT1100) and structured monoliths prepared from SBA-15 and Pluronic P-123/F-127, with a pore-expanded P-123 option were studied. Across these groups, four preparation routes were used to control the amount and accessibility of amine sites: polymer cross-linking or chemical modification (EDA-based sorbents, PEI-based sorbents), covalent grafting (AP, DT), impregnation (PEI, TEPA), and double functionalization (grafting followed by impregnation).

    The functionalized monoliths were characterized by a coordinated variety of techniques to link structure, chemistry, and performance. Low-angle X-ray diffraction (XRD) verified mesostructural ordering and phase purity after synthesis, pore expansion, and subsequent modification. Nitrogen physisorption provided surface area, total pore volume, and pore-size distributions, allowing direct comparison between non-expanded and pore-expanded P-123 as well as SBA-15 and F-127 monoliths. Thermogravimetric analysis (TGA) quantified CO2 uptake at 45 °C under controlled feeds, including repeated adsorption-desorption cycles. Elemental analysis (CHN) was used to determine nitrogen content, which enabled calculation of amine efficiency (mol CO2/mol N). Volumetric analyses completed the picture with isotherms from 0 bar to 6 bar at 45 °C.

    CO2 adsorption performance was evaluated under post-combustion capture conditions, emphasizing low partial pressures (0.15 bar CO2) and practical regeneration. For powders, cross-linked and chemically modified polymers established the role of amine chemistry at modest surface areas. For monoliths, grafting (AP, DT), polymer impregnation (PEI, TEPA), and the two-step double-functionalization route (grafting followed by impregnation) were compared across conventional and pore-expanded supports. Metrics reported include uptake (mg CO2/g), amine efficiency (mol CO2/mol N), approach to equilibrium at 45 °C, multi-cycle stability, and performance at 1-6 bar to reflect pressurized operation. Particular attention was paid to maintaining a portion of pore volume for gas access, achieving uniform polymer distribution (via reflux impregnation), and leveraging pore expansion when higher nitrogen contents were targeted.