Various morphologies of clinoptilolites synthesized in alcohol-solvent hydrothermal system and their selective adsorption of CH4 and N2

Abstract Clinoptilolite (CP) with various morphologies, such as spherical, flower, cylindrical, and disc-shape, were successfully synthesized in the presence of alcohol solvents with different carbon chain lengths. The structural and textural properties of the resultant CPs were characterized via XRD, SEM, TG-DSC profiles, TEM, NMR, FT-IR spectra, and N2 sorption isotherms. The effect of the additive amount of various alcohol solvents on the induction (nucleation) periods and growth stages of synthetic CPs were detailed investigated. Their activation energies of induction (En) and growth (Eg) periods during crystallization intervals were calculated according to the Arrhenius equation, where the former being larger than the latter, indicating that nucleation is the key step during the whole synthesis of CPs. Particularly, the En value gradually increased as the increasing chain-length of the used alcohol, but smaller than that without additive alcohols. These demonstrations implied that the presence of alcohol solvents is beneficial to promote the nucleation process of synthetic CP. Furthermore, their CH4 and N2 adsorption capacity and selectivity were preliminary explored, showing the highest selective factor of 5.58 at 0 °C for CH4/N2 separation using flower-like CP as an adsorbent. These results suggested a promising adsorbent for wide applications in gas separation.