LAUSR

Abstract Nanosol precursor was obtained via hydrothermal pre-crystallization time periods of 6, 60 and 102 h at 423 K. Different amounts of nanosol precursor with different crystallization time periods were added to the hydrothermal synthesis system as structural promoter (SP) to synthesize clinoptilolite. The various characterizations such as XRD, SEM, BET, FT-IR, TG-DSC, ICP, UV-Raman, and element analysis were employed to investigate the structural and textural characteristics and potential applications of synthetic clinoptilolites in CH4/N2 separation. Their activation energies of induction (En) and growth (Eg) periods during crystallization intervals were calculated according to Arrhenius equation, where the former being much larger than the latter proved that nucleation is the key in the synthesis of clinoptilolite. The En value gradually decreased with increasing amount of the SP and its pre-crystallization time interval, which further revealed that the addition of SP with the shortened crystallization time is beneficial in the formation of crystal nuclei. However, the amount of SP significantly altered the particle size, extent of impurities (phillipsite), and thermal stability of the clinoptilolite. The results demonstrated that pure clinoptilolite could be successfully synthesized in a short time period at low temperature. Particularly, the ion exchange performance and CH4/N2 separation capacity of clinoptilolite synthesized with the additive SP (3 wt %) in the pre-crystallization interval of 60 h were found almost in similarity with the clinoptilolite prepared without SP, showing a promising adsorbent for kinetic separation of CH4/N2.