Synthesis and ion exchange of zeolites produced from kaolin for separation of oxygen from atmospheric air

Abstract

Lithium‐based zeolites are the most commonly used materials in PSA (pressure swing adsorption) oxygen concentration from atmospheric air. Synthesizing these adsorbents using mineral raw materials adapts to worldwide environmental requests, as only high‐purity chemical reactants such as aluminates and silicates are usually used. The present work aims to synthesize and characterize zeolites using kaolin as raw material by studying the influence of the metakaolinization temperature and SiO2/Al2O3 and H2O/Na2O molar ratios by experimental design. Ion exchange was used to incorporate lithium into synthesized zeolites. Kaolin was treated thermically and characterized, and zeolites were synthesized by a hydrothermal reaction. After synthesis, ionic exchange of Na+ ions by Li+ was performed. The results indicated the presence of three main phases, zeolites A, X, and P. Using ANOVA, it was found that the factors that contributed significantly to the formation of zeolite X were the H2O/Na2O and SiO2/Al2O3 molar ratios. For zeolite A, the major influence was by the metakaolinization temperature and for zeolite P none of the factors was influential. Zeolites that incorporated higher amounts of lithium showed higher N2 adsorption potential, indicating that even without pure phases formed, it was possible to obtain similar adsorption efficiency to commercial zeolite.

Adsorption of CO2 Using “Sugar Cube”-Shaped Zeolite A Type Derived from Thermally Treated Kaolin and NaOH

“…From the DTG curve, it is clearly observed that the conversion of kaolin into metakaolin starts from 500 °C. From the DTA curve, it is observed that the endothermic region corresponds to the water loss and the exothermic region corresponds to material stability and phase change of the materials. ,, The obtained results of thermal studies are found to be in good agreement with the XRD results, and it clearly indicates that the zeolite synthesized at higher temperatures above 800 °C has more of an impurity phase when compared with zeolite synthesized at lower temperatures.…”

Green and low-cost synthesis of zeolites from kaolin: a promising technology or a delusion?

“…132,[156][157][158] We can assume that if there are Al IV atoms in the raw material, less energy is expended to convert the residual Al V and Al VI into Al IV during hydrothermal synthesis, and it accelerates the formation of zeolite. The silicon atoms are tetrahedral at all the above steps, and there is only one peak on the 29 Si MAS NMR spectra. 159 Fig.…”

“…Feltrin et al have synthesised zeolite X in a mixture with zeolites P and A using metakaolin obtained at 800 and 900 °C for 2 h. 29 Other things being equal, the metakaolin obtained at 900 °C always gave less zeolite A with Si/Al = 1 and more zeolites X and P with Si/Al > 1. It can be attributed to the decrease of active Al 2 O 3 (or Al IV ) and the increase of active SiO 2 in metakaolin obtained at 900 °C compared to metakaolin obtained at 800 °C.…”

“…196 The assembly of a framework by joining such particles in solution is not considered for many reasons. Mainly because, despite the large number of oligomeric silicate anions detected by 29 Si NMR, no individual chemical structures that could be CBU, SBU or RBU have been seen in solution. 197 These particles exist in the gel phase.…”