Promoting effect of titanium on Cu/γ-Al₂O₃ catalyst for CO₂ hydrogenation

Abstract

This study reveals the promoting effect of titanium on Cu/γ-Al₂O₃ catalyst for the hydrogenation of CO₂by X-ray diffraction (XRD), temperature-programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS) analysis. The relationship between the area of metallic copper and the activity of methanol synthesis has also been investigated. The

catalytic activity over Cu-Ti/γ-Al₂O₃ catalyst for CO₂ hydrogenation is higher than that of Cu/γ-Al₂O₃. The adding of titanium is beneficial in enhancing the dispersion of the supported copper oxide and make the reduction behavior of Cu-Ti/γ-Al₂O₃ catalyst different from the individual supported copper oxide catalysts. For the Cu-Ti/γ-Al₂O₃ catalyst there are two reducible copper oxide species; α and β peaks are attributed to the reduction of highly dispersed copper oxide species and bulk CuO species respectively. For the Cu-Ti/γ-Al₂O₃ catalyst, four reduction peaks are observed, Two TPR peaks with lower temperatures (namely α₁ and α₂) have been attributed to the hydrogen uptake of nested oxygen ions and temptable

oxygen ions, respectively, β₁ and β₂ peaks are attributed to the reduction of bulk CuO with different particle size of copper. XPS results reveal that there exists strong interaction between the copper oxide and titania which makes the binding energy of Cu(2P_3/2) shift to higher value.