Regioselective hydroformylation of propene catalysed by rhodium-zeolite.

Zhang, Xiangjie; Yan, Tao; Hou, Huaming; Yin, Junqing; Wan, Hongliu; Sun, Xiaodong; Zhang, Qing; Sun, Fanfei et al. · Nature · 2024

basic_science · Level V

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Abstract

Hydroformylation is an industrial process for the production of aldehydes from alkenes<sup>1,2</sup>. Regioselective hydroformylation of propene to high-value n-butanal is particularly important, owing to a wide range of bulk applications of n-butanal in the manufacture of various necessities in human daily life<sup>3</sup>. Supported rhodium (Rh) hydroformylation catalysts, which often excel in catalyst recyclability, ease of separation and adaptability for continuous-flow processes, have been greatly exploited<sup>4</sup>. Nonetheless, they usually consist of rotationally flexible and sterically unconstrained Rh hydride dicarbonyl centres, only affording limited regioselectivity to n-butanal<sup>5-8</sup>. Here we show that proper encapsulation of Rh species comprising Rh(I)-gem-dicarbonyl centres within a MEL zeolite framework allows the breaking of the above model. The optimized catalyst exhibits more than 99% regioselectivity to n-butanal and more than 99% selectivity to aldehydes at a product formation turnover frequency (TOF) of 6,500 h<sup>-1</sup>, surpassing the performance of all heterogeneous and most homogeneous catalysts developed so far. Our comprehensive studies show that the zeolite framework can act as a scaffold to steer the reaction pathway of the intermediates confined in the space between the zeolite framework and Rh centres towards the exclusive formation of n-butanal.