Rh-Catalyzed Hydroformylation of 1,3-Butadiene and Pent-4-enal to Adipaldehyde in CO2-Expanded Media

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Issue Date
2019-10-25Author
Tenorio, Maria-José
Chaudhari, Raghunath V.
Subramaniam, Bala
Publisher
American Chemical Society
Type
Article
Article Version
Scholarly/refereed, publisher version
Rights
Copyright © 2019 American Chemical Society
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The homogeneous hydroformylation of pent-4-enal, the preferred aldehyde intermediate from 1,3-butadiene hydroformylation, was systematically investigated with Rh catalyst complexes in neat and CO2-expanded toluene media at 40–80 °C, syngas partial pressures ranging from 5–50 bar, and different ligand/Rh ratios. At similar operating conditions, the TOFs are generally greater with Rh/DIOP relative to a Rh/TPP catalyst. On both catalyst complexes, the chemoselectivity toward the dialdehydes ranges from 75%–100%, with the maximum adipaldehyde selectivity reaching approximately 75% (n/i ∼ 3) at 60 °C, 10 bar syngas, and molar DIOP/Rh ratio of 2.5. By using CO2-expanded toluene, the regioselectivity toward the adipaldehyde (desired product), and therefore its yield, is significantly enhanced. Interestingly, even with the simple Rh/TPP catalyst complex, adipaldehyde selectivity of up to 85% (n/i ∼ 5.6) is achieved at 60 °C, 10 bar syngas, and 50 bar CO2. The beneficial effects of CO2-expanded media are attributed to the facile tunability of the H2/CO ratio in such a phase with a fixed syngas feed composition. This approach to accelerate pent-4-enal hydroformylation to form adipaldehyde could also help in overcoming equilibrium limitations typically associated with the catalytic isomerization of pent-3-enal (the dominant product from 1,3-butadiene hydroformylation) to pent-4-enal (the preferred isomer).
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Citation
Ind. Eng. Chem. Res. 2019, 58, 22526−22533
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