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Fe III -containing ionic liquids (ILs), prepared from the reaction of anhydrous FeCl 3 and imidazolium chloride ([imidazolium]Cl), were used as effective extractants for the desulfurization of a model oil containing dibenzothiophene (DBT). The amount of DBT extracted increased with an increasing molar ratio of FeCl 3 / [imidazolium]Cl. The ability of the ILs to extract DBT seems to be attributed to the combined effects of Lewis acidity and fluidity of ILs.

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Imidazolium-based ionic liquids (ILs) bearing an alkylphosphite anion, were highly efficient for the selective removal of acetylenes in olefins. Comparison of solubility data at 313 K and at atmospheric pressure shows that the solubilities of acetylene and propyne in 1,3-dimethylimidazolium methylphosphite ([DMIM][MeHPO(3)]) are about 45 and 20 times higher than those of ethylene and propylene, respectively. Computational and (1)H NMR results clearly demonstrate that there are substantial interactions between the acidic hydrogen atom or atoms of acetylenes and the phosphite anion.

Room temperature ionic liquids (RTILs) are proposed as the alternative solvents for the acetylene separation in ethylene generated from the naphtha cracking process. The solubility behavior of acetylene in RTILs was examined using a linear solvation energy relationship based on Kamlet-Taft solvent parameters including the hydrogen-bond acidity or donor ability (α), the hydrogen-bond basicity or acceptor ability (β), and the polarity/polarizability (π*). It is found that the solubility of acetylene linearly correlates with β value and is almost independent of α or π*. The solubility of acetylene in RTILs increases with increasing hydrogen-bond acceptor (HBA) ability of the anion, but is little affected by the nature of the cation. Quantum mechanical calculations demonstrate that the acidic proton of acetylene specifically forms hydrogen bond with a basic oxygen atom on the anion of a RTIL. On the other hand, although C-H···π interaction is plausible, all optimized structures indicate that the acidic protons on the cation do not specifically associate with the π cloud of acetylene. Thermodynamic analysis agrees well with the proposed correlation: the higher the β value of a RTIL is, the more negative the enthalpy of acetylene absorption in the RTIL is.

Quantum-mechanical calculations based on density functional theory (DFT) have been carried out on the migratory insertion process [M(CO)2I3(CH3)]- → [M(CO)I3(COCH3)]- (M = Rh, Ir), which represents an important step in methanol carbonylation. The calculated free energies of activation (ΔG ⧧) are 27.7 kcal mol-1 (Ir) and 17.2 kcal mol-1 (Rh), in good agreement with the experimental estimates at 30.6 ± 1.0 kcal mol-1 (Ir) and 19.3 ± 0.5 kcal mol-1 (Rh). The higher barrier for M = Ir is attributed to a relativistic stabilization of the Ir−CH3 bond. It is indicated that enthalpic and entropic contributions to ΔG ⧧ can vary considerably, depending on reaction conditions, without changing ΔG ⧧ considerably. Especially, simulations based on ab initio molecular dynamics (AIMD) underlined that the reaction system might prefer to trade entropy for enthalpy in polar solutions by dissociating an I- ligand for M = Ir. A systematic study was also carried out on the general methyl migration reaction [Ir(CO)2I2L(CH3)] n - → [Ir(CO)I2L(COCH3)] n - (n = 0, 1), in which an iodide ligand trans to methyl is replaced by another ligand L (where L = CH3OH, CH3C(O)OH, CO, P(OCH3)3, SnI3 -) or an empty coordination site. The free energy of activation for the methyl migration in [Ir(CO)2I2L(CH3)] with L trans to methyl follows the order P(OCH3)3 > CO > SnI3 -, none > I- > CH3OH, CH3C(O)OH with respect to the ligand L. This order is to a first approximation determined by the ability of L to labilize the M−CH3 bond trans to it. The order is further shaped by the ability of the π-acceptors L = CO, P(OCH3)3 to stabilize the transition state, and, in the case of L = none, by the relocation of an iodide ligand to the site trans to the migrating methyl group. It is finally discussed how placing L cis to the migrating CH3 group might influence the migratory aptitude of methyl.

Imidazolium-based zinc-containing ionic liquids (ILs), [1-R-3-R′-imidazolium]alkylsulfate-ZnCl2 (R and R′ = H or alkyl), were highly effective for the denitrogenation of a model oil containing quinoline, indole, or acridine in n-heptane. Fast atom bombardment (FAB)−mass spectra and a computational study imply that the interaction of 1-ethyl-3-methylimidazolium ethylsulfate ([EMIm]EtSO4) with ZnCl2 produces Zn-containing ILs, presumably [EMIm]ZnCl2(EtSO4) and [EMIm]ZnCl(EtSO4)2 as the major ionic species. The interaction of EtSO4 − and ZnCl2(EtSO4)− with a heterocyclic N compound was theoretically investigated. The zinc-containing IL, [EMIm]ZnCl2(EtSO4), used for the extraction of quinoline was successfully regenerated by employing diethyl ether as a back extractant.

Ionic liquids with halide anions were prepared and the dependency of halide anions on the SO2 solubility of ILs was investigated. The study shows that the SO2 solubility of ionic liquids lies in the range 1.91 ~ 2.22 SO2/ILs mol ratio. SO2 solubility in ionic liquids with varying halide anions follows the order Br > Cl > I. Theoretical investigation was also conducted at the B3LYP level using the Gaussian 03 program. From the theoretical consideration of the interaction between SO2 and [EMIm]X (where X = Cl, Br, and I), it has been proposed that primary interaction of halide occurs with C2-H of the imidazolium and S of SO2. Experimental results further shows that the absorption and desorption process of SO2 in ILs was reversible by the three cycles of the absorption at 50 o C and desorption at 140 o C. The reversibility of SO2 absorption was confirmed by FT-IR studies.