Novel Microfibrous Composite Bed Reactor Incorporated with Silver Catalyst for High Efficiency Gas-Phase Oxidation of Alcohols

Novel microfibrous-structured silver catalysts were developed and were demonstrated for high efficiency gas-phase oxidation of various alcohols to their corresponding carbonyl products. Sinter-locked three-dimensional microfibrous networks consisting of 5 vol% 8 µm (dia.) Ni fibers or 12 µm (dia.) SS-316L fibers and 95 vol% void volume were built up by the regular papermaking/sintering processes. Active Ag component was then deposited onto the surface of the sinter-locked fibers by incipient wetness impregnation method. At relatively low reaction temperatures (e.g., 380 ^oC), the present micro-structured reactor incorporated with silver catalysts provided quite higher activity/selectivity for the oxidation of mono-/aromatic-/di-alcohols compared to the electrolytic silver catalyst. The microfibrous Ag/Ni-fiber catalyst bed offered much better low-temperature activity than the Ag/SS-fiber catalyst, mostly due to the synergistic effect between Ag particles and Ni-fiber. Catalytically relevant physiochemical properties of the samples were explored by XRD, XPS, SEM, H₂-TPR, UV-visible diffuse reflectance spectroscopy, and O₂-chemisorption techniques. The interaction at Ag particles and Ni-fiber interface not only visibly increased the amount of active/selective sites of Ag⁺ ions and Ag^nδ+ clusters but also significantly promoted their activity as evidenced by the low-temperature reduction/re-oxidation feature in the H₂-TPR/O₂-TPO experiments. In addition, the microfibrous structure provided a unique combination of large void volume, entirely open structure, excellent heat/mass transfer and high permeability good thermal stability, and therefore led to a significant increase in the steady-state volumetric reaction rate, compared to the electrolytic silver.