세미나

Ceria is an essential component in the heterogeneous catalysis for non-reductive CO₂ conversion and rhenium-catalyzed deoxydehydration (DODH).

Ceria is an effective heterogeneous catalyst for the reactions such as alcohols+CO₂, amines+CO₂, and alcohols+amines+CO₂ which give corresponding organic carbonates [1], urea derivatives [2], and carbamates [3]. When the equilibrium limitation is severe [4], we have proposed the methods to break the limitation by the combination with the hydration of nitriles [5] and by H₂O removal with gas stripping method [6]. Recently, we utilized the CO₂-absorbed ethylenediamine (EDA-CA) as the reactant in the left figure, and its advantage is that pressurized CO₂ is not needed [7, 8].

DODH is the removal of vicinal OH groups to give carbon-carbon double bond, and it is more suitable to the synthesis of value-added chemicals from biomass because platform chemicals in the biomass refinery have OH groups [9]. It has been known that Re (VII) complexes catalyze DODH using PPh₃ and secondary alcohols as a reductant. Our target is to develop active heterogenous DODH catalysts using H₂ as a reductant. Our approach is the combination of high valent Re species fixed on oxides and noble metals with high H₂ activation ability for the development of heterogenous DODH catalysts enabling H₂ reductant. We reported that CeO₂ was much more effective support than other supporting materials such as carbon, SiO₂ and so on. A typical catalytic system is ReO_x-Pd/CeO₂ [9], where DODH and subsequent hydrogenation can proceed and the saturated products were obtained. In order to obtain DODH products, a co-catalyst with high activation ability of H₂ and low catalytic activity in the hydrogenation of C=C. We found that ReO_x-M/CeO₂ (M=Au, Ag) was effective as an effective heterogeneous DODH catalysts [10, 11], and the reaction mechanism is illustrated in the right figure.

References

[1] K. Tomishige, Y. Gu, M. Tamura, Y. Nakagawa, (2020), Mater. Today Sustain., 9, 100035.
[2] M. Yabushita, R. Fujii, Y. Nakagawa, K. Tomishige, (2024), ChemCatChem, 16, e202301342.
[3] Y. Gu, A. Miura, M. Tamura, Y. Nakagawa, K. Tomishige, (2019), ACS Sustain. Chem. Eng., 7, 16795.
[4] K. Tomishige, Y. Gu, Y. Nakagawa, M. Tamura, (2020) Frontiers in Energy Research, 8, 117
[5] K. Tomishige, M. Tamura, Y. Nakagawa, (2019), Chem. Rec. 19, 1354.
[6] Y. Gu, M. Tamura, Y. Nakagawa, K. Nakao, K. Suzuki, K. Tomishige, (2021), Green Chem., 23, 5786.
[7] R. Fujii, M. Yabushita, D. Asada, M. Tamura, Y. Nakagawa, A. Takahashi, A. Nakayama, K. Tomishige, (2023), ACS Catal., 13, 1562.
[8] R. Fujii, M. Yabushita, Y. Li, Y. Nakagawa, K. Tomishige, (2023), ACS Catal., 13, 11041.
[9] N. Ota, M. Tamura, Y. Nakagawa, K. Okumura, K. Tomishige, (2015), Angew. Chem. Int. Ed., 54, 1897.
[10] S. Tazawa, N. Ota, M. Tamura, Y. Nakagawa, K. Okumura, K. Tomishige, (2016), ACS Catal. 6, 6393.
[11] K. Yamaguchi, J. Cao, M. Betchaku, Y. Nakagawa, M. Tamura, A. Nakayama, M. Yabushita, K. Tomishige, (2022), ChemSusChem, 15, e202102663.