Influence of preparation method on the catalytic performances of Re2O7/SiO2-Al2O3 catalysts in the metathesis of ethylene and 2-pentene

The metathesis of ethylene and 2-pentene for propylene production was investigated over Re2O7/SiO2-Al2O3 catalysts. The SiO2-Al2O3 (50 wt% Al2O3) were obtained by co-precipitation, physical mixing, and sol–gel coating. The presence of isolated layers/grains γ-Al2O3 either in bulk (physical mixing) or on the surface (sol–gel coating) resulted in isomerization-free metathesis. On the contrary, the Re2O7 catalysts supported on co-precipitated SiO2-Al2O3 or the direct synthesis showed both metathesis and double-bond shift isomerization activities and as a consequence, higher propylene yield was obtained via the secondary metathesis reaction. The catalytic properties were also correlated with the Al-atom rearrangements and the acidic characters/strengths.