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International audience; The acceleration of the development of ethylene oligomerization processes by homogeneous catalysis requires a complete characterization of the catalytic system. This work proposes to use segmented gas-liquid flow in microchannels to achieve high experimental throughput for catalyst testing. Gas-liquid flow was studied in order to validate the microreactor setup. Results showed that bubble and slug lengths vary linearly with the superficial velocities ratio following the Garstecki et al. model [21]. The impact of lateral feed in Taylor flow was explored to mimic the catalyst feed in an oligomerization test. The experiments showed that the volume of the liquid slugs increased proportionally to the additional flow rate, thereby suggesting that the majority of the liquid in the lateral feed is ultimately retained in the liquid slug. A study of mass transfer showed that the volumetric mass transfer coefficient is between 0.27 and 0.55 s−1. These values lead to a Hatta number < 0.5, thus confirming the possibility of conducting the ethylene oligomerization reaction in the chemical kinetic regime. Finally, an ethylene oligomerization test performed in the microreactor showed that the continuous microreactor system can be used for catalyst screening purpose.

International audience; 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.

International audience; The reactivity of a phenoxy-imine-ether system (FI)TiCl3/MAO was studied toward selective ethylene trimerization. This system was shown to either trimerize or polymerize ethylene depending on the reaction temperature. Its selectivity switches from a significant production of the trimerization product, 1-hexene (85 wt %, 520-450 kg1-hexene gTi-1 h-1) between 30 and 40 °C, to a moderate polyethylene formation (70-80 wt %, 60-70 kgpolyethylene gTi-1 h-1) at higher reaction temperature (T > 60 °C). Polymerization was investigated based on an original "polymer-to-catalyst" strategy aiming at identifying the active species responsible for this side reaction. Using DSC, SEC and high temperature 13 C NMR analyses, polyethylenes were found to exhibit high molar masses (> 10 5 g mol-1) and a low 1-hexene content (< 1 mol %) at any temperature. Kinetic studies support that trimerization and polymerization species are generated from the catalyst precursor at 40 °C but a parallel process may occur at higher temperature. The increase dispersity to 4.6 at 80 °C suggests a change from single to multisite catalysis. The poor comonomer incorporation ability of the active species is reminiscent of a molecular Ziegler Natta or a bulky postmetallocene catalyst.