No abstract

No abstract

The acidity scale of different Brønsted acids in ionic liquids such as [BMIM][NTf2], [BMIM][BF4], and [BMMIM][BF4] 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.

Résumé -Oligomérisation des mono-oléfines par des catalyseurs homogènes -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. Abstract -Oligomerization of Monoolefins by Homogeneous Catalysts

Homogeneous olefin oligomerization plays a pivotai role in the field of petrochemistry. Through catalysts, technology and process developments, market requirements in terms of productivity, selectivity and sustainability have been addressed. Over more than 50 years, an intensive research has been devoted to the design of new Group 4 to Group 10 transition metal complexes and to the study of their reactivity towards olefins leading to severa! breakthroughs of prime importance for academy as for industry. Since the early sixties, IFPEN contributed to bring innovative industrial solutions to different targets from gasoline production to alpha-olefin on purpose processes with over 100 production units built worldwide . Based on nickel, titanium, zirconium or chromium, the catalytic systems for such processes and their next generation are subject to a continuous research where the adaptation of the ligand architecture to the nature of the metal and its mode of activation, play a crucial role to control the reaction selectivity and the catalyst lifetime. lnteresting relationships between the complex structure and their reactivity have been drawn and will be discussed on selected examples.

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.

No abstract

Theoretical chemistry Theoretical chemistry Z 0350 Ionic Liquids: Perspectives for Organic and Catalytic Reactions -[192 refs.]. -(OLIVIER-BOURBIGOU, H.; MAGNA, L.; J. Mol. Catal. A: Chem. 182-183 (2002) 419-437; Inst. Fr. Pet., F-92506 Rueil-Malmaison, Fr.; Eng.) -Lindner 04-275