Han Yujun,Shi Yinteng,Wang Dandan,Zhou Hantao,Chen Jixiang
Ni/ZrO 2 (Ni/Zr) and Ni/WO 3 -ZrO 2 (Ni/ x WZr, x denotes WO 3 /ZrO 2 mass ratios) were prepared by the impregnation-direct reduction method and tested for the aqueous phase hydrogenation of phenol to cyclohexanone in an autoclave reactor. It has been found that the Ni-W alloy forms in Ni/ x WZr, and a charge transfer occurs from Ni to W. The presence of W species promotes the Ni dispersion and increases the amounts of acid sites and spilt-over hydrogen species. This leads to higher hydrogenation and direct deoxygenation activity of Ni/ x WZr than that of Ni/Zr. In addition, the W 6+ and W 4+ species, acted as Lewis acidic sites, may stabilize cyclohexanone and the hydrogenation of cyclohexanone to cyclohexanol is inhibited. Under suitable condition, the phenol conversion and the cyclohexanone selectivity reach 93.1 and 90.6% on Ni/0.8WZr, respectively.
Hydrogen spillover is a well-known phenomenon in heterogeneous catalysis; it involves H 2 cleavage on an active metal followed by the migration of dissociated H species over an ‘inert’ support 1 , 2 , 3 , 4 , 5 . Although catalytic hydrogenation using the spilled H species, namely, spillover hydrogenation, has long been proposed, very limited knowledge has been obtained about what kind of support structure is required to achieve spillover hydrogenation 1 , 5 . By dispersing Pd atoms onto Cu nanomaterials with different exposed facets, Cu(111) and Cu(100), we demonstrate in this work that while the hydrogen spillover from Pd to Cu is facet independent, the spillover hydrogenation only occurs on Pd 1 /Cu(100), where the hydrogen atoms spilled from Pd are readily utilized for the semi-hydrogenation of alkynes. This work thus helps to create an effective method for fabricating cost-effective nanocatalysts with an extremely low Pd loading, at the level of 50 ppm, toward the semi-hydrogenation of a broad range of alkynes with extremely high activity and selectivity.
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