Synthesis of nitrogen-rich hollow microspheres for CO2 adsorption
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The nitrogen-rich hollow microspheres (MFM) with different pore sizes have been synthesized by using melamine, m-phenylenediamine and paraformaldehyde as monomer, different particle sizes of SiO2 microsphere as template, and water as solvent. The specific surface area, pore volume and average pore size of the synthesized MFM were 183.67 m2/g, 0.91 cm3/g and 19.8 nm, respectively. After loading polyethyleneimine (PEI), its CO2 adsorption capacity could reach 2.68 mmol/g at 60 °C, with the corresponding utilization efficiency of amino as high as 40.66%. The kinetic simulation of pseudo-first-order, pseudo-second-order and Avrami kinetic model showed that the Avrami model could better describe the adsorption process of CO2, indicating both physical adsorption and chemical adsorption in the whole process. The diffusion mechanism was simulated by using the Boyd model, the intermolecular diffusion model and the intraparticle diffusion model, showing that the porous structure of MFM was beneficial to the diffusion of CO2 in the particles. After 5 cycles, 10 cycles, 15 cycles and even after 20 cycles of adsorption–desorption, the adsorption capacity of MFM-PEI at 30 °C was nearly the same as the capacity of the fresh one, indicating the regeneration stability of the adsorbent, with great advantages in practical production.
The authors gratefully acknowledge the financial support provided by the National Natural Science Foundation of China (Grant No. 51473187) and Science and Technology Project of Guangdong Province (2016A010103013).
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