Iridium pincer complexes are well-known catalysts for the dehydrogenation of alkanes to olefins. The advantage they offer, in contrast to their heterogeneous counterparts, resides in their ability to perform the dehydrogenation at moderate pressure and temperature with a higher selectivity of the sought-after terminal olefin. However, due to the miscibility of the catalyst with the product/substrate mixture, iridium pincer catalysts, and more generally homogeneous catalysts, are difficult to recycle and are, therefore, challenging to implement at industrial scale. In recent years, tremendous synthetic efforts have been dedicated to the heterogenization of homogeneous catalysts to make them compatible with continuous processes. While some supported catalysts have shown promising activity, the challenging ligand synthesis required for this approach makes it impractical for commodity chemicals' production.<br/>Here, we will present a novel strategy for performing the dehydrogenation of alkanes in a continuous process using iridium pincer catalysts. Our approach relies on the difference in volatility between the substrate and the catalyst to perform the continuous reaction/separation at steady-state over a several hour period. As a model experiment, we will show results obtained for the disproportionation of hexene into hexadiene and hexane. The continuous addition of substrate and removal of product enables the catalyst to perform the reaction for hours without significant loss of activity.<br/>Furthermore, the continuous-flow reactor allows for an easy and immediate analysis of the reaction kinetics, which will help study and design next generation catalysts for dehydrogenation.

Dehydrogenation of alkanes using pincer complexes in a continuous process

254th National Meeting (2017)

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