The application of {(DMF) 10Yb 2[TM(CN) 4] 3} ∞ (TM = Ni, Pd) supported on silica to promote gas phase phenol hydrogenation

• Published in: Journal of molecular catalysis. A, Chemical Vol. 212; no. 1; pp. 291 - 300
• Main Authors: Shore, Sheldon G, Ding, Errun, Park, Colin, Keane, Mark A
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 02.04.2004
• Subjects: Cyclohexanol; Cyclohexanone; Phenol hydrogenation; Selective hydrogenation; Silica supported Pd/Yb and Ni/Yb; Selective hydrogenation; Phenol hydrogenation; Cyclohexanone; Cyclohexanol; Silica supported Pd/Yb and Ni/Yb
• ISSN: 1381-1169; 1873-314X
• DOI: 10.1016/j.molcata.2003.11.004

Gas phase phenol hydrogenation activities/selectivities associated with Pd/SiO 2 prepared by Pd(NO 3) 2 and Pd(C 2H 3O 2) 2 impregnation are compared with those delivered by Pd–Yb/SiO 2 prepared from a {(DMF) 10Yb 2[Pd(CN) 4] 3} ∞ precursor. Pd takes the form of nanoscale particles (see TEM image) while Yb is present as a thin film. The incorporation of Yb appreciably enhanced hydrogenation activity due to hydrogen transfer via surface Yb hydride. The catalytic gas phase phenol hydrogenation activities/selectivities associated with Pd/SiO 2 prepared by Pd(NO 3) 2 and Pd(C 2H 3O 2) 2 impregnation have been compared with those delivered by Pd–Yb/SiO 2 prepared from a {(DMF) 10Yb 2[Pd(CN) 4] 3} ∞ precursor. The Pd metal loading spanned the range 1–10% (w/w) and the reaction was conducted over the temperature interval 398–448 K. Phenol hydrogenation yielded both cyclohexanone as a partially hydrogenated reactive intermediate and cyclohexanol as the fully hydrogenated product. The activated catalysts have been characterized by HRTEM/EDX, XPS and XRD. The reaction exhibits a slight dependence on Pd particle size with a lower specific hydrogenation activity associated with larger Pd particles. The incorporation of Yb resulted in an appreciable enhancement of phenol conversion. Yb/SiO 2, however, did not exhibit any hydrogenation activity and the promotional effect of Yb in Pd–Yb/SiO 2 is tentatively attributed to hydrogen transfer via surface Yb hydride. The effect of contact time and reaction temperature on activity/selectivity has been considered and is discussed in terms of phenol/catalyst interaction(s). The promotional effect of Yb also extends to phenol hydrogenation over supported Ni (5%, w/w Ni) where Ni–Yb/SiO 2 delivered higher conversions and higher overall cyclohexanone yields when compared with Ni/SiO 2.