Preparation And Adsorption Properties Of Three-dimensional Porous Graphene Oxide Based CO₂ Adsorbent

In this paper,two adsorbents,namely,nitrogen-doped 3D graphene oxide based CO₂ adsorbent and polyethyleneimine cross-linked graphene oxide 3D porous CO₂adsorbent,were constructed for capturing CO₂ in the flue gas of coal-fired power plants using graphene oxide as the building block.The adsorbents were also characterized by scanning electron microscopy（SEM）,specific surface analysis（BET）,X-ray diffraction analysis（XRD）,elemental analysis,X-ray photoelectron spectroscopy（XPS）,thermal stability analysis（TGA）,and Fourier infrared spectroscopy（FTIR）to investigate the change patterns of pore structure as well as surface functionalization during the preparation of the two adsorbents,and the relationship between structure and CO₂adsorption performance was also revealed by the CO₂ adsorption experiments.Finally,by comparing the performance of the two adsorbents,polyethylenimine crosslinked graphene oxide 3D porous CO₂ adsorbent was selected as an excellent CO₂adsorbent for CO₂ capture in actual coal-fired flue gas.（1）Preparation and adsorption properties of nitrogen doped three-dimensional graphene oxide-based CO₂ adsorbentGraphene oxide was used as the building block,and N-doped reduction was used to prepare 3D porous structured carriers,and long chain amino functionalized CO₂adsorption materials were prepared by impregnation method.The prepared carriers possessed good 3D structure by SEM analysis,and the structure was not changed and preserved after impregnation with amino groups.The adsorption and desorption experiments showed that the maximum CO₂ adsorption capacity was 2.026mmol/g（343K,10 vol%）,the adsorption amount remained 97%of the original adsorption amount after 10 cycles of adsorption and desorption.（2）Preparation and adsorption performance of polyethyleneimine cross-linked graphene oxide 3D porous CO₂ adsorbentsThe CO₂ adsorbent was prepared by dispersing graphene oxide using ultrasound and then cross-linking the functional groups on the surface of graphene oxide with polyethyleneimine using chemical reactions in the form of covalent and non-covalent bonds,etc.,and then the cross-linked adsorbent was stabilized by vacuum freeze-drying method to stabilize the 3D porous structure.The specific surface area and pore size of the prepared CO₂ adsorbent decreased with increasing the amine ratio.The CO₂adsorption results showed that the CO₂ adsorption capacity of the prepared material was smaller with higher polyethyleneimine concentration.GP（1800）-1 had the maximum CO₂ adsorption capacity（2.18 mmol/g）at 343 K.The Avrami model was used to fit the adsorption kinetics,the CO₂ adsorption activation energy was 14.629 KJ.mol^-1.The equivalent heat of adsorption was 57.4 KJ.mol^-1,indicating chemisorption between the adsorbent and CO₂.After 10 cycles of adsorption and desorption,the adsorption amount was reduced by 5%.