Synthesis, Pelleting, and Performance Evaluation of a Novel K‑Promoted γ‑Alumina/MgAl-Layered Double Oxide Composite Adsorbent for Warm Gas H₂/CO₂ Separation

Development of stable solid adsorbent in pellet form is of importance for CO₂/H₂ separation at elevated temperature (250–450 °C). This study provides a novel synthesis method by adding K₂CO₃ solution into alumina sol soaked MgAl-layered double hydroxide paste. The delay time of K₂CO₃ addition is studied to demonstrate that the formation of K-promoted γ-alumina is facilitated by an immediate addition. Extruded adsorbent of higher CO₂ capacity (0.65 mmol/g) and radial crushing strength (75.6 N per pellet) is obtained. The existing crystalline phase of obtained adsorbent is screened by X-ray diffraction. The adsorption capacity and adsorption kinetics of the developed adsorbent is characterized by a thermogravimetric analyzer in terms of calcination temperature of both dominant constituent materials, MG63 hydrotacite, and K-promoted pseudo boehmite. Crystal transit temperatures of the constituents are considered in selecting the optimal calcinations temperature. The adsorbent pellets, pretreated with the optimal parameters studied, are packed in a fixed-bed to test breakthrough curves of CO₂, consistent dynamic capacity compared to that of thermogravimetric testing data were obtained. Results of multicycle CO₂ adsorption and desorption, steam sweeping, pressure change, and wear tests prove the stability of the adsorbent both in CO₂ capacity and mechanical strength