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Synthesis and Evaluation of Modified Zeolites for Separation of Acidic Gases

Najafi, Amir Mohammad | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 56148 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Khorasheh, Farhad; Soltanali, Saeed; Ghasabzadeh, Hamid
  7. Abstract:
  8. The adsorption equilibria of carbon dioxide, methane, and nitrogen on pelletized cation-exchanged faujasite zeolite (with alkali, alkaline earth, and transition metal ions) have been investigated by a volumetric apparatus. The standard instrumental analytical techniques, including X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) coupled with energy dispersive X-ray spectroscopy (EDX), and atomic absorption spectroscopy (AAS) were utilized to characterize binder-free modified zeolites. The EDX spectra and AAS results revealed that the ion-exchange was successfully achieved with expected tendencies. The results indicate that the type of cation present in the zeolite framework can notably affect the adsorption capacity. The obtained isotherms were determined by three isotherm model and Sips model was found to show the best agreement with the experimental isotherm data for all gases. The CO2 uptakes of KX, MgX and CaX were reached 4.13, 4.79, and 5.48 mmol/g, respectively. The effective binary and kinetic selectivity of CO2/CH4 and CO2/N2 were also calculated. Among all samples, KX showed the highest CO2/CH4 and CO2/N2 selectivity of 54.46 and 91.62, respectively. Pseudo-first-, pseudo-second-order, and Avrami kinetic models were fitted to the experimental kinetic data to analyze the adsorption kinetics. Finally, the macropore diffusion coefficient (D_p) and microporous diffusional time constant (D_c⁄(r_c^2 )) were estimated by correlating the micropore-macropore kinetic model with the experimental fractional uptake curves. Among the ion-exchanged zeolite samples, the K+ form exhibits suitable performance in terms of kinetic behavior and adsorption capacity
  9. Keywords:
  10. Carbon Dioxide Absorption ; Ion Exchange ; Kinetic Model ; Diffusion Coefficient ; Gases Separation ; Faujasite Zeolite

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