Microfibrous-structured silver catalyst for low-temperature gas-phase selective oxidation of benzyl alcohol

A highly active and selective silver on nickel fiber catalyst was successfully prepared for selective oxidation of benzyl alcohol. The Ag/Ni catalyst was obtained by loading Ag (10 wt%) on paper-like microfibrous structure (consisting of 5 vol% of 8-mu m Ni-fiber) by impregnation method. The wettability of Ni-fiber support was vastly improved by a simple water pre-wetting and overnight drying treatment process. This yielded a catalyst (Ag/Ni-fiber-M) with more Ag cations and selectively active oxygen species than the catalyst (Ag/Ni-fiber) using the untreated support. The Ag/Ni-fiber-M showed much higher low-temperature activity/selectivity than the Ag/Ni-fiber, which could be attributed to the differences in their silver morphology and particle size. The best conversion and benzaldehyde selectivity observed were both 97% for Ag/Ni-fiber-M at 300 degrees C, and 91 and 84% for Ag/Ni-fiber at 380 degrees C, respectively. Benzyl alcohol selective oxidation would proceed concurrently through both direct O-2 activation route and NiOx-participating oxygen spillover route. Formation of NixC phase occurred and hampered the latter reaction route thereby leading to partial deactivation. However, spent catalyst could restore activity through an oxidation treatment at 400 degrees C. (C) 2010 Elsevier B.V. All rights reserved.