Synthesis, Pelleting, and Performance Evaluation of a Novel K-Promoted gamma-Alumina/MgAl-Layered Double Oxide Composite Adsorbent for Warm Gas H-2/CO2 Separation

Abstract

Development of stable solid adsorbent in pellet form is of importance for CO2/H-2 separation at elevated temperature (250-450 degrees 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 gamma-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.