Role of support nature (γ-Al2O3 and SiO2-Al2O3) on the performances of rhenium oxide catalysts in the metathesis of ethylene and 2-pentene

摘要

The metathesis of ethylene and 2-pentene was studied as an alternative route for propylene production over Re2O7/γ-Al2O3 and Re2O7/SiO2-Al2O3 catalysts.Both NH3 temperature-programmed desorption (NH3-TPD) and H2 temperature-programmed reduction (H2-TPR) results showed that Re2O7/SiO2-Al2O3 exhibited stronger acidity and weaker metal-support interaction than Re2O7/γ-Al2O3.At 35-60 ℃,isomerization free metathesis was observed only over Re2O7/γ-Al2O3,suggesting that the formation of metal-carbene metathesis active sites required only weak acidity.Our results suggest that on the Re2O7/SiO2-Al2O3,hydrido-rhenium species ([Re]-H) were formed in addition to the metathesis active sites,resulting in the isomerization of the initial 1-butene product into 2-butenes.A subsequent secondary metathesis reaction between these 2-butenes and the excess ethylene could explain the enhanced yields of propylene observed.The results demonstrate the potential for high yield of propylene from alternative feedstocks.