Investigation of methane adsorption on molecular sieve zeolite (from natural materials)

In this study, Kaolin, Bentonite, and Feldspar were used as a low-cost source of Si and Al to synthesize the molecular sieve ۱۳X. The synthesized Zeolites were characterized by XRD, FTIR, SEM, TGA, and BET analysis and used as a suitable adsorbent for CH۴ adsorption. The surface areas were ۵۹۱, ۵۰۵, ۴۷۲, and ۵۸۸ m۲/g for natural kaolin (۱۳X-K), bentonite (۱۳X-B), feldspar (۱۳X-F) and commercial molecular sieve ۱۳X (۱۳X–C), respectively. The ۱۳X-K had the highest thermal stability than ۱۳X-B and ۱۳X-F. The adsorption capacities (pressure >۲۰bar) of ۱۳X (kaolin), ۱۳X (bentonite), and ۱۳X(feldspar) were ۳.۶, ۲.۴, and ۱.۹۵ mmol/g, respectively. The adsorption data were fitted to some isotherms including Langmuir, Freundlich, Sips, BET, and Toth. It was found that the Sips model showed better fitting in comparison to other models. The thermodynamic of adsorption was also investigated; the positive value of ∆S_ads^۰ revealed the increased randomness at the solid-solution interface during the gas adsorption. The thermodynamic study also indicated that the adsorption process was exothermic and spontaneous. The adsorption capacities of synthesized ۱۳X samples were compared to other adsorbents; it was found that ۱۳X–K showed considerable performance and can be introduced as a suitable adsorbent for applications on a large scale.

Keywords:

Methane , ۱۳X , Adsorption , Isotherm , Thermodynamic