Abstract:The liquid-liquid equilibrium for the ternary system formed by n-octane and aromatic (alkylbenzenes) and heteroaromatic compounds (nitrogen and sulfur containing heterocyles) and 1-alkyl-3-methylimidazolium ionic liquids (ILs) associated with various anions has been investigated. The selectivity on the extraction of a specific aromatic compound is influenced by anion volume, hydrogen bond strength between the anion and the imidazolium cation and the length of the 1-methyl-3-alkylimidazolium alkyl side chain. The interaction of alkylbenzenes and sulfur heterocyles with the IL is preferentially through CH-π hydrogen bonds and the quantity of these aromatics in the IL phase decreases with the increase of the steric hindrance imposed by the substituents on the aromatic nucleus. In the case of nitrogen heterocycles the interaction occurs preferentially through N(heteroaromatic)-H(imidazolium) hydrogen bonds and the extraction process is largely controlled by the nitrogen heterocycle pKa. Competitive extraction experiments suggest that benzene, pyridine and dibenzothiophene do not compete for the same hydrogen bond sites of the IL.

We propose a model to calculate the electronic structure of hydrotalcite-like compounds by using periodic boundary conditions and ab initio density functional theory (DFT). The proposed method to build up layered double hydroxides (LDHs) was tested for Zn 2/3 Al 1/3 (OH) 2 Cl 1/3 • 2 / 3 H 2 O, Zn 2/3 Al 1/3 (OH) 2 (CO 3 ) 1/6 • 4 / 6 H 2 O, and Mg 2/3 Al 1/3 (OH) 2 (CO 3 ) 1/6 • 4 / 6 H 2 O with 3R 1 polytype. In the model, the occupation of cationic sites in hydroxide layers is ordered and the interlayer anions and water molecules form a film between the layers. Direct comparison with experimental structural parameters shows good agreement. The a parameter is close to that in brucite for all three LDHs. The c parameter is smaller (about 1 Å) for the LDHs with CO 3 2as a consequence of its strong interaction with hydroxide layers. Those interactions were evidenced by the difference of density and vibrational analysis. The intercalated water molecules have small mobility and interact strongly with one another and with interlayer anions and hydroxide layers. These interactions cause the downshift in the calculated vibrational wavenumbers of water O-H stretching modes below 3420 cm -1 and are consistent with the reported infrared spectra of hydrotalcite-like compounds. The calculated formation enthalpies for LDHs with carbonate are in agreement with the previously reported trend. The biggest difference between theoretical and experimental values is 2 kcal/mol. The calculated formation Gibbs energies are negative. The zero point energy is important to evaluate ∆H, but the formation entropy does not affect the Gibbs free energy significantly.

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Going against tradition: Uniformly distributed Pd nanoparticles on imidazolium‐ionic‐liquid‐modified Al2O3 surfaces are prepared by a top down approach by using a new sputtering chamber. The hydrogenation of 1,3‐cyclohexadiene is used to probe the surface properties of these new Pd nanoparticles.