Do N-doped activated carbons truly outperform N-free activated carbons for CO2 separation in humid conditions?


Morales-Ospino R. Taurbekov A. Castro-Gutiérrez J. Izquierdo M.T. Atamanov M. Mansurov Z. Celzard A. Fierro V.
5 March 2025Elsevier Ltd

Carbon
2025#234

This study aims to evaluate whether N-doping of activated carbons (ACs) can improve CO2 separation in a real-world post-combustion scenario. A high-surface-area, N-free AC was synthesized and subsequently N-doped by blending it with urea and subjecting it to heat treatment at 623 K in air. The potential of this N-doped AC for environmental gas separation was assessed, focusing on its CO2 capture performance in the presence of increasing relative humidity (RH) levels. High-pressure adsorption isotherms for CO2 and N2 were obtained and fitted, using the Dual-Site Langmuir model to calculate selectivity. The results indicate that the N-doping post-treatment with urea reduces the AC textural properties, particularly affecting larger micropores and mesopores. Despite this, N-doping enhances CO2 selectivity, and dynamic breakthrough simulations for CO2/N2 separation suggest that N-doped AC can perform better than undoped samples under dry conditions due to their increased tap density. However, N-doping also increases water affinity, which may be undesirable for applications involving undried flue gas streams. The pristine AC exhibited a nearly stable CO2 adsorption capacity up to 40 % relative humidity (RH), whereas the CO2 capacity of the N-doped AC progressively decreased from 10 % RH.

Activated carbons , Adsorption , CO2 separation , N-doping , Water vapor

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Université de Lorraine, CNRS - IJL, Épinal, 88000, France
Al-Farabi Kazakh National University, Almaty, Kazakhstan
Institute of combustion problems, Almaty, Kazakhstan
Instituto de Carboquimica (ICB-CSIC), Spain
Institut Universitaire de France - IUF, Paris, 75231, France

Université de Lorraine
Al-Farabi Kazakh National University
Institute of combustion problems
Instituto de Carboquimica (ICB-CSIC)
Institut Universitaire de France - IUF

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