Ordered Mesoporous Co3O4−Al2O3 Binary Metal Oxides for CO Hydrogenation to Hydrocarbons: Synergy Effects of Phosphorus Modifier for an Enhanced Catalytic Activity and Stability

Abstract

The synergy effects of phosphorus modifier on highly ordered mesoporous binary metal oxides of Co3O4−Al2O3 (m‐CoAl), prepared by nanocasting method using a hard template of KIT‐6, were observed by an enhanced catalytic and structural stability of the m‐CoAl during CO hydrogenation to hydrocarbons. The enhanced structural stability of the ordered mesoporous structures on the phosphorous‐modified m‐CoAl at an optimal amount of phosphorous modifier below 0.3\u2005wt%P (P(3)/m‐CoAl) was attributed to the partial formation of thermally stable metal phosphates under a reductive Fischer‐Tropsch synthesis (FTS) reaction condition. The positive effects of the phosphorous modifier were originated from the partially formed SiO2‐like AlPO4 phases on the outer surfaces of the m‐CoAl, as well as from partially formed irreducible and thermally stable spinel‐type cobalt aluminates (CoAl2O4). The hydrophobic SiO2‐like tridymite AlPO4 surfaces on the ordered matrices of the P/m‐CoAl also effectively prevented the heavy wax (or coke precursors) depositions. The structural instability of the P/m‐CoAl was observed at a higher phosphorous content above 0.5wt%P by preferentially forming the largely segregated mixed metal oxides such as Co3O4−CoAl2O4−Co3(PO4)2 through the phase transformations of the surface excess AlPO4.