Sorption of trifluoromethane in zeolites and ionic liquid

• Adsorption of trifluoromethane on zeolites Na-Y, K,H-Y, and Rb,Na-Y.
• Absorption of trifluoromethane in ionic liquid, [emim][Tf2N].
• Heat of adsorption of trifluoromethane on zeolites from 29 to 35 kJ · mol−1.
• Type II adsorption on zeolites.
• Type V phase behavior in ionic liquid.

Sorption isotherms for trifluoromethane (R-23) on three zeolites, Na-Y, K,H-Y, and Rb,Na-Y and ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [emim][Tf2N] have been measured at ca. 298 and 323 K, using a gravimetric microbalance. The adsorption on the zeolites reaches about 3 mol · kg−1 at 0.025 MPa and 298 K while in the ionic liquid the absorption reaches 3 mol · kg−1 at about 2.5 MPa (100 times higher pressure). Three different adsorption models (Langmuir, multi-site Langmuir, and BET equations) have been used to analyze the zeolite sorption data, with a particular interest in the heat of adsorption (−ΔH). The heat of adsorption for zeolites Na-Y, K,H-Y, and Rb,Na-Y were about 35 ± 3 kJ · mol−1, 29 ± 3 kJ · mol−1, and 34 ± 5 kJ · mol−1, respectively. These values are within the range of typical physical adsorption. According to the IUPAC classification, the zeolites exhibit Type II adsorption and according to the Scott and van Konynenburg classification the ionic liquid is predicted to be Type V phase behavior. The adsorption process on the zeolites took more time than the absorption process in the ionic liquid to reach the thermodynamic equilibrium and both processes were reversible.