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@PHDTHESIS{Selmert:1047563,
      author       = {Selmert, Victor},
      title        = {{I}nvestigation of {P}olyacrylonitrile-based {C}arbon
                      {N}anofibers as {A}dsorbents for the {S}eparation of
                      {C}arbon {D}ioxide using {D}ynamic {G}as {A}dsorption},
      school       = {RWTH Aachen University},
      type         = {Dissertation},
      publisher    = {RWTH Aachen University},
      reportid     = {FZJ-2025-04389},
      pages        = {215},
      year         = {2025},
      note         = {Dissertation, RWTH Aachen University, 2025},
      abstract     = {Electrospun polyacrylonitrile-based carbon nanofibers
                      (CNFs) exhibit a molecular sieving effect. The pore size can
                      be controlled by the choice of the carbonization
                      temperature, making such nanofibers a promising material for
                      gas separation. In this work, these nanofibers are
                      investigated for the application in the field of gas
                      separation using dynamic gas adsorption and are tested
                      against common reference materials. These experiments allow
                      to analyze the adsorption behavior of a packed column of the
                      fibers in terms of selectivity, stability, as well as
                      adsorption and desorption kinetics under conditions similar
                      to the application in an adsorption swing process. First,
                      the procedure of the dynamic gas adsorption method is
                      optimized for small, laboratory-scale amounts of sample. It
                      is shown that an exact determination of the contribution of
                      the void volume is paramount for accurate results.
                      Furthermore, the measurement of desorption curves following
                      the breakthrough curves increases the accuracy in the case
                      of competitively adsorbing gases. In order to optimize the
                      volumetric packing density and the pressure drop along the
                      column, the pelletization of the fibers is also
                      investigated. It is shown that performing the pelletization
                      before carbonization of the fibers is advantageous, since
                      the low mechanical stability of the non-carbonized fibers
                      yields a greater compression of the fibrous material.
                      Accordingly, a higher bulk density and, thus, a higher
                      volumetric adsorption capacity is achieved. Subsequently,
                      the separation capabilities of the pelletized fibers are
                      evaluated on technically relevant separation problems such
                      as CO2 separation from N2-rich mixtures like flue gases or
                      CO2 and N2 separation from biogas-like or natural gas-like
                      mixtures. The CO2/N2 separation on the fibers shows an
                      exceptionally high selectivity, especially for a
                      carbon-based material, and exceeds the values for most
                      reference materials. The high selectivity of the CNFs is
                      attributed to the high adsorption potential of CO2
                      associated with the narrow ultramicropores as well as the
                      high heteroatom content present in CNFs carbonized at low
                      temperature. In contrast, the separation of CO2 and N2 from
                      CH4-richgas mixtures is kinetically driven and based on the
                      size difference of CH4 to N2 and CO2 and on the narrow pores
                      of the fibers. At higher carbonization temperature and thus,
                      a narrower pore system, CH4 is excluded from the pores,
                      leading to a strong kinetic limitation, while CO2 as well as
                      N2 are adsorbed sufficiently fast. While the separation
                      performance is attributed to the surface chemistry for the
                      CO2/N2 mixture, the separation performance for CO2 and N2
                      from CH4 is based on the molecularsieve effect. Water
                      adsorption experiments show that the CNFs adsorb water with
                      high affinity and to a high adsorption capacity, which has
                      significant influence on the CO2 adsorption. In cyclic
                      adsorption/desorption experiments with moistened CO2, there
                      is an accumulation of water on the CNFs, which reduces the
                      CO2 capacity significantly. Therefore, drying of the gas
                      mixture is necessary in order to apply the fibers for CO2
                      separation. However, the high water affinity also proves
                      that the CNFs could be applied in the field gas drying as
                      well. Overall, the electrospun polyacrylonitrile-based CNFs
                      achieve a selective separation in the tested applications
                      and offer the possibility to adjust selectivity as well as
                      kinetics via the carbonization temperature to the needs of a
                      given separation problem. Therefore, the material proves to
                      be promising for the separation of CO2 from dry gas mixtures
                      or for the drying of gases.},
      keywords     = {Hochschulschrift (Other) / carbon nanofibers ; gas
                      separation ; adsorption ; carbon capture ; carbon molecular
                      sieve ; breakthrough curve (Other)},
      cin          = {IET-1},
      cid          = {I:(DE-Juel1)IET-1-20110218},
      pnm          = {1232 - Power-based Fuels and Chemicals (POF4-123) / DFG
                      project G:(GEPRIS)390919832 - EXC 2186: Das Fuel Science
                      Center – Adaptive Umwandlungssysteme für erneuerbare
                      Energie- und Kohlenstoffquellen (390919832) / HITEC -
                      Helmholtz Interdisciplinary Doctoral Training in Energy and
                      Climate Research (HITEC) (HITEC-20170406)},
      pid          = {G:(DE-HGF)POF4-1232 / G:(GEPRIS)390919832 /
                      G:(DE-Juel1)HITEC-20170406},
      typ          = {PUB:(DE-HGF)11},
      doi          = {10.18154/RWTH-2025-05853},
      url          = {https://juser.fz-juelich.de/record/1047563},
}