About the Acidity-Catalytic Activity Relationship in Ionic Liquids: Application to the Selective Isobutene Dimerization

Abstract

Résumé -Acidité et activité catalytique dans les liquides ioniques : application à la dimérisation sélective de l'isobutène -Le niveau d'acidité de Brønsted de différents acides a été évalué dans une série de liquides ioniques non chloroaluminates. Dans une première approche, nous avons utilisé la méthode basée sur la détermination de la fonction de Hammett H 0 par la spectroscopie UV-Visible.

Brønsted acids in ionic liquids: how acidity depends on the liquid structure

“…Finally, the AN scale is a quantitative measure of acidity applicable to both Lewis and Brønsted acids. AN values are determined by 31 P NMR spectroscopy, making use of small quantities of the weakly basic 31 P NMR probe molecule, triethylphosphine oxide (tepo), which is dissolved in the medium under investigation. Changes in the AN measurements were used to study Lewis acidity of chlorometallate ionic liquids, 29 and to investigate a wide range of 'typical' ionic liquids.…”

“…Changes in the AN measurements were used to study Lewis acidity of chlorometallate ionic liquids, 29 and to investigate a wide range of 'typical' ionic liquids. 30 Acidity, expressed on both Hammett 31 and Guttmann 5 scales, was demonstrated to be among key factors affecting catalytic performance of Brønsted acidic ionic liquids.…”

“…For each ionic liquid-acid mixture studied, three samples with different small quantities of tepo were prepared, to allow extrapolation of the 31 P NMR chemical shift value to infinite dilution, δ inf . 31 P NMR spectra were acquired at 121.452 MHz using a Bruker DRX 300 spectrometer. Phosphoric acid, 85% solution in water, was used as an external reference.…”

Structural Effects on the Physico‐Chemical and Catalytic Properties of Acidic Ionic Liquids: An Overview

“…Although the measured acidity level in a given solvent other than water might be lowered as a result of the association process, the order of the relative acidities should be maintained, at least when the solvent properties of the non-aqueous medium are not too different from those of water. [72] Unfortunately, determination of the acidity of a pure acidic IL by this method and with the acidic IL as solvent is impossible because the initial absorbance of the total unprotonated form of the indicator (blank value) cannot be obtained. The acidities of several protic ILs in molecular solvents (CH 2 Cl 2 , ethanol, acetonitrile) have therefore been determined.…”

Perspectives of Ionic Liquids Applications for Clean Oilfield Technologies

“…The "acidity scale" was tentatively compared with an "activity scale" obtained for the dimerization of isobutene into isooctenes. (Gilbert et al, 2009) EtAlCl 2 /AlCl 3…”