Catalyst acidity is among the crucial parameters affecting the direction and degree of acid-catalyzed reactions. The Hammett acidity functions (H0) of binary mixtures of triflic acid (TfOH) and ionic liquids (ILs), namely, [BMim][HSO4], [BMim][TfO], and [BMim][TFA], were measured by the 13C NMR method using mesityl oxide as a probe. The results show that the H0 values of the mixtures can be effectively controlled by tailoring the structure of the IL or tuning the amount of IL added to the system. The −H0 values of the binary mixtures decrease with increasing amount of IL. Mixtures of [BMim][HSO4]/TfOH and [BMim][TfO]/TfOH show minimal changes in acidity (−H0 > 13.00) when the IL mole fraction is less than 0.05, a sharp decline in acidity (−H0 = 13.00 → 8.00) at an IL mole fraction of 0.05 to 0.20, and a relatively stable acidity (−H0 = 8.00 → 5.40) at an IL mole fraction of 0.20 to 0.50. These mixtures share nearly the same H0 value when the IL mole fraction is less than 0.20. The addition of [BMim][TFA] can alter the Hammett acidities of the binary systems more easily than [BMim][HSO4] or [BMim][TfO] at the same concentration. Models to predict the H0 values of the three IL/TfOH binary systems as a function of acid concentration are also proposed.

A dual acidic ionic liquid 3-sulfobutyl-1-(3-propyltriethoxysilane)imidazolium hydrogen sulfate was synthesized and immobilized on MCM-22 via covalent bonding, which was characterized by FT-IR, TGA, SEM, BET, XPS, and XRD. The modulating of adsorption capacity by novel immobilized ionic liquid was demonstrated by ethane and ethylene. The results indicate that after immobilization, the main structure of the MCM-22 remains unchanged and the acid amount increased. This material displays relatively superior adsorption ability in tuning the ratio of paraffin/olefin (the adsorbed ratio of ethane/ethylene increased over 30%). The immobilized ionic liquid is believed to tune the adsorption capacity resulting in these enhanced results. In addition, this concept could also be applicable to Friedel–Crafts alkylation, catalytic cracking reaction, adsorption separation, or other competitive adsorption reactions.

The solubility of isobutane in three ionic liquids 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIm][PF6]), 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm][BF4]), and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([BMIm][Tf2N]) at temperatures ranging from 288.2 K to 313.2 K and pressures up to near atmospheric pressure were determined by a saturation technique. The solubility values were correlated using the Peng–Robinson equation of state with van der Waals 2-parameter mixing rules. In general, the model and the experimental data were in good agreement. Henry’s constants were calculated on the basis of the solubility data at different temperatures and fitted to the Benson–Krause (BK) equation well. The results showed that the solubilities of isobutane in these three ionic liquids increased with increasing pressure and decreased with increasing temperature and were in the sequence: [BMIm][Tf2N] > [BMIm][PF6] > [BMIm][BF4]. The solubility parameters (δ) of these three ILs were calculated and were used to qualitatively explain the difference of the solubility of isobutane in different ILs. Partial molar thermodynamic functions of solvation such as standard Gibbs free energy, enthalpy, and entropy were calculated from the solubility results.

Adsorption properties of an adsorbent or a catalyst towards adsorbates are crucial in the process of adsorption separation or catalytic reaction. Surface morphology and structure of adsorbents have a significant impact on the adsorption properties. In this study, a novel acidic ionic liquid, 1-butyl-3-(triethoxysilylpropyl)imidazolium hydrogen sulfate (i.e., [BTPIm][HSO4]), was synthesized and subsequently grafted onto the MCM-36 zeolite for the regulation of its adsorption properties towards isobutane and 1-butene. The resultant [BTPIm][HSO4]-immobilized MCM-36 (i.e., MCM-36-IL) was characterized by FT-IR, XPS, XRD, SEM, TG/DTG and N2 adsorption–desorption measurement. It was found that the specific surface area, micropore volume and mesopore volume of the MCM-36 support underwent a reduction upon the immobilization of ionic liquid, while the surface density of acid increased from 0.0014 to 0.0035 mmol·m− 2. The adsorption capacity of isobutane and 1-butene on the MCM-36-IL was determined by a static volumetric method. Results demonstrated that the interaction between isobutane and MCM-36-IL was enhanced and the interaction between 1-butene and MCM-36-IL was reduced. As a result, a tunable adsorption ratio of isobutane/1-butene on MCM-36 was achieved. With the increase in surface density of acid and the tunable adsorption ratio of isobutane and 1-butene on the functionalized MCM-36, the acidic ionic liquid-immobilized zeolites are beneficial to obtain an improved reaction yield and a prolonged catalyst life in the reactions catalyzed by solid acid.