Pyrochlore/Al₂O₃ composites supported Pd for the selective synthesis of cyclopentanones from biobased furfurals

Designing a bifunctional catalyst with both highly selective C[dbnd]O hydrogenation ability and Lewis acid-catalyzed ring-rearrangement ability is highly important for the synthesis of the cyclopentanone motifs from furfural derivatives. Herein, a class of pyrochlore/Al₂O₃ composites (2.68 wt%Y₂(Sn_0.65Al_0.35)₂O_7-δ/Al₂O_3, 7.74 wt%Y₂(Sn_0.65Al_0.35)₂O_7-δ/Al₂O₃) with a onefold Lewis acidity and rich oxygen defects were synthesized via a dissolution-precipitation method. After the impregnation by Pd nanoparticles, the oxygen defect of pyrochlore/Al₂O₃ shows a bifunctional effect: they can adsorb C[dbnd]O, promoting the selective C[dbnd]O hydrogenation step and can enhance the accessibility of coordinatively unsaturated metal ions, providing Lewis acidic sites for the ring-rearrangement step. The composite-based catalysts show noticeably higher hydrogenation and hydrolysis rates than their corresponding single metal oxide-based catalysts (Pd/Al₂O₃, Pd/Y₂Sn₂O₇). Finally, 7.74 wt%Y₂(Sn_0.65Al_0.35)₂O_7-δ/Al₂O₃ shows a cyclopentanone yield of 98.1 % and a 3-hydroxymethyl cyclopentanone yield of 90.6 %. ATR-IR results verify the catalytic mechanism and emphasize the importance of oxygen defects.