This review attempts to give a survey on the last most representative developments and progress dealing with ionic liquids from their fundamental properties to their applications in catalytic ...processes. It also highlights their emerging use for biomass treatment and transformation.
This review gives a survey on the latest most representative developments and progress concerning ionic liquids, from their fundamental properties to their applications in catalytic processes. It also highlights their emerging use for biomass treatment and transformation.
Brought to life more than half a century ago and successfully applied for high-value petrochemical intermediates production, nickel-catalyzed olefin oligomerization is still a very dynamic topic, ...with many fundamental questions to address and industrial challenges to overcome. The unique and versatile reactivity of nickel enables the oligomerization of ethylene, propylene, and butenes into a wide range of oligomers that are highly sought-after in numerous fields to be controlled. Interestingly, both homogeneous and heterogeneous nickel catalysts have been scrutinized and employed to do this. This rare specificity encouraged us to interlink them in this review so as to open up opportunities for further catalyst development and innovation. An in-depth understanding of the reaction mechanisms in play is essential to being able to fine-tune the selectivity and achieve efficiency in the rational design of novel catalytic systems. This review thus provides a complete overview of the subject, compiling the main fundamental/industrial milestones and remaining challenges facing homogeneous/heterogeneous approaches as well as emerging catalytic concepts, with a focus on the last 10 years.
In this article are summarized the different mechanistic pathways for the oligomerization of monoolefins by homogeneous catalysts, particularly for ethylene and alpha olefins. The major topics are: ...the production of non regioselective and also regioselective olefin dimers, the production of linear alpha olefins by ethylene oligomerization as well as the selective dimerization of ethylene and its selective trimerization. Several industrial developments initiated by IFP are presented to illustrate this topic.
Cet article résume les différents schémas réactionnels pour l'oligomérisation des mono-oléfines par catalyse homogène, en particulier pour l'oligomérisation de l'éthylène et des alpha-oléfines. Les principaux sujets abordés sont la production régiosélective ou non de dimères, la production d'alpha-oléfines linéaires par oligomérisation de l'éthylène ainsi que la dimérisation sélective de l'éthylène et sa trimérisation sélective. Plusieurs procédés industriels développés par l'IFP sont présentés pour illustrer ce sujet.
The acidity scale of different Brønsted acids in ionic liquids such as BMIMNTf2, BMIMBF4, and BMMIMBF4 has been investigated by determination of Hammett functions, using a spectrophotometric ...indicator method. This scale should permit one to correlate the acidity strength of ionic liquid systems with their ability to achieve acid-catalyzed reactions.
Ionic liquids are attracting a great deal of attention as possible replacement for conventional molecular solvents for catalytic and organic reactions. They complete the use of environmentally ...friendly water, supercritical fluids or perfluorinated solvents. Features that make ionic liquids attractive include their lack of vapor pressure and the great versatility of their chemical and physical properties. By a judicious combination of cations and anions, it is possible to adjust the solvent properties to the requirement of the reactions, thus creating an almost indefinitely set of “designer solvents”. Besides the possibility of recycling the catalytic system, one main potential interest in using ionic liquids results in the unique interactions of these media with the active species and in the possibility to modify the reaction activity and selectivity. Their successful use as solvents has been demonstrated for a wide range of organic reactions including acid catalyzed reactions and transition metal catalyzed transformations.
The structural properties of new organochloroaluminate ionic liquids based on mixtures of (Ethyl)nAlCl$_{(3-n)}$ (n = 1 to 3) with 1-methyl-3-butyl-imidazolium chloride (BMIC) have been studied by ...Raman spectroscopy. With this technique, the mono and polynuclear anions present in these melts have been identified and quantified. The mixed salts formed with AlCl3 and EtAlCl2 or EtAlCl2 and Et2AlCl together with BMIC are also considered. All behave as regular chloroaluminates; in particular, their acid-base properties depend on their compositions. Thanks to this study, it has been possible to anticipate and to optimize the composition of an ionic liquid based on EtAlCl2, with the aim of performing industrially the Ni-catalyzed olefin oligomerization in chloroaluminates. The influence of the solvent composition on the overall mechanism of the catalysis is now basically understood. The resulting ionic liquids play the dual role of solvents and nickel activator (or co-catalyst).
Les propriétés structurales de nouveaux liquides ioniques organochloroaluminates, constitués à partir de mélanges de (Ethyl)nAlCl$_{(3-n)}$ (n = 1 à 3) avec du chlorure de 1-methyl-3-butyl-imidazolium (BMIC) ont été étudiées par spectrométrie Raman. À partir de cette technique, tous les anions mono et polynucléaires ont été identifiés et quantifiés. Les mélanges mixtes formés à partir d'AlCl3 et EtAlCl2 ou EtAlCl2 et Et2AlCl, chaque couple étant à son tour mélangé avec du BMIC, ont aussi été considérés. Tous ces mélanges se comportent comme les chloroaluminates habituels : en particulier, leurs propriétés acide-base sont directement dépendantes de leurs compositions. Grâce à cette étude, il a été possible d'anticiper et d'optimiser la composition d'un liquide ionique basé sur de l'EtAlCl2, dans le but de l'utiliser pour l'oligomérisation industrielle des oléfines catalysées par les complexes du nickel, en milieux chloroaluminates. Les aspects fondamentaux de l'influence de la composition de ce solvant sur le mécanisme général de la réaction d'oligomérisation sont actuellement compris. Les liquides ioniques jouent un double rôle : ils sont à la fois solvants et activateurs du nickel (ou co-catalyseur).
Diimine nickel complexes activated with aluminoxane in chloroaluminate ionic liquids are highly active catalysts either for the biphasic ethylene oligomerization or for polymerization depending on ...the bulkiness of the diimine ligand. The activation of Ni(0) with a BrOnsted acid in different non-chloroaluminate ionic liquids is also reported. The nature of the ionic liquid and the presence or not of a nitrogen ligand affect significantly the catalytic performances. The olefinic products are weakly soluble in ionic liquids and can be separated from the catalytic ionic phase by simple decantation. The nickel catalysts are immobilized and stabilized in the ionic liquids and can be recycled.
The Brønsted acidity level was evaluated for ionic liquids to which a strong acid has been added. As a first approach, the evaluation method was based on the determination of the Hammett acidity ...functions H0, using UV-Visible spectroscopy. The acidity of protons is mainly determined by their solvation state and consequently, the properties of protons depend on both the nature of the solvent and the nature and concentration of the acid. An apparent acidity scale was defined following this principle. It was found that, for the investigated ionic liquids, the cation does not play a dominant role on the acidity level (BMIm ~ BHIm ~ HNEt3 ), whereas changing the nature of the anion of the ionic liquid may lead to very different acidities ( SbF6 > PF6 > BF4 > NTf2 > OTf). This “acidity scale” was tentatively compared with an “activity scale” obtained for the dimerization of isobutene into isooctenes. The tendencies concerning the cation effect were confirmed (BMIm ~ BuMePyrr ~ HNEt3 ). The anion effect in only partially validated with a different behaviour for NTf2 type ionic liquids ( NTf2 ~ SbF6 > PF6 ~ BF4 > OTf). By an adequate choice of the ionic liquid, selectivity for isobutene dimers can reach 88 wt% (at 70% isobutene conversion) with possible recycling of the catalytic system without loss of activity and selectivity.
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 H0 par la spectroscopie UV-Visible. L'acidité du proton est principalement déterminée par son état de solvatation et sa concentration. Les propriétés des protons dépendent par conséquent à la fois de la nature du solvant et de la nature de l'acide ajouté, ainsi que de sa concentration dans le milieu ionique. Une échelle d'acidité apparente a ainsi été définie. Il ressort, pour la série de liquides ioniques étudiée, que le cation ne joue pas de rôle majeur sur le niveau d'acidité (BMIm ~ BHIm ~ HNEt3 ), contrairement à la nature de l'anion du liquide ionique qui conduit à des variations importantes du niveau d'acidité : SbF6 > PF6 > BF4 > NTf2 > OTf. Cette échelle d'acidité a été comparée à une échelle d'activité pour la réaction de dimérisation de l'isobutène en isooctènes. Les tendances concernant l'effet du cation sont confirmées par les niveaux de conversion observés en catalyse (BMIm ~ BuMePyrr ~ HNEt3 ). On notera cependant un certain décalage en ce qui concerne l'effet de l'anion avec un positionnement différent des liquides ioniques basés sur les anions NTf2 : NTf2 ~ SbF6 > PF6 ~ BF4 > OTf. Finalement, sur un plan appliqué, un choix adéquat du liquide ionique et de l'acide ajouté permet d'atteindre, à température ambiante, une sélectivité en isooctènes de 88% (à 70% de conversion de l'isobutène) avec un recyclage possible du système catalytique sans perte notable d'activité ni de sélectivité.
Unsaturated vegetable oils are an attractive renewable feedstock, and the selective cleavage of unsaturated fatty esters is an important transformation in this respect. The efficient and selective ...cross‐metathesis of methyl oleate with ethylene was achieved under mild conditions with ruthenium‐alkylidene catalysts in toluene and room‐temperature ionic liquids (RTILs) to give two important chemical intermediates, 1‐decene and methyl 9‐decenoate, without double‐bond migration. As recovery of the catalyst is an important target with respect to industrial applications, catalyst recycling studies were also carried out in RTILs with the first‐generation Hoveyda catalyst.
Oil rush: The selective cleavage of unsaturated fatty esters from vegetable oils, a renewable feedstock, is an important transformation. The ethenolysis of methyl oleate was performed efficiently in room‐temperature ionic liquids with the first‐generation Hoveyda ruthenium catalyst to afford 1‐decene and methyl 9‐decenoate, useful intermediates for the production of lubricants and polyesters. Moreover, the catalyst could be recycled.
Rhodium nanoparticles stabilized by 2,2′-, 3,3′-, 4,4′-bipyridine ligands were prepared in various ionic liquids according to a chemical reduction approach. Zerovalent nanospecies in the size range ...of 2.0−2.5 nm were characterized. The nature of the bipyridine and its influence on the coordination environment of rhodium nanoparticles were investigated in various nonaqueous ionic liquids according to the cation and anion. The hydrogenation of various aromatic compounds by these colloidal suspensions was carried out at 80 °C and under 40 bar of H2. A first structural explanation based on bipyridine coordination modes is proposed to justify the observed different activities.
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