Phosphorus-loaded alumina supported nickel catalysts for CO₂ hydrogenation: Ni₂P/Ni₅P₁₂ drives activity

Highlights

• A series of 5 wt% NiO-xP-Al₂O₃ with different phosphorus loading contents (x = 0, 5, 15 and 20 wt%) were prepared by a modified sol-gel method.

• All the catalysts reach the highest conversion at 600 °C with 61.54 %, 62.89 %, 63.88 % and 66.13 % respectively for 5 wt% NiO-Al₂O₃, 5 wt% NiO-5P-Al₂O₃, 5 wt% NiO-15P-Al₂O₃ and 5 wt% NiO-20P-Al₂O₃ catalysts.

• Ni/NiO/Ni₂P/Ni₅P₁₂/AlPO₄ interfacial species were detected on the surface as active species on the used catalysts by X-ray photoelectron spectroscopy.

• The formation ratio of the metal-phosphide is relatively low ∼3−5 %, and this atomic concentration is decreasing with the rising of the phosphate content. However, the nickel enrichment in the surface layer presumable in Ni₂P/Ni₅P₁₂ form is very likely according to the P 2p spectra and the authors assume that could be responsible for the enhanced catalytic activity.

Abstract

A series of 5 wt% NiO-xP-Al₂O₃ with different phosphorus loading contents (x = 0, 5, 15 and 20 wt%) were prepared by a modified sol-gel method. A significant promotional effect of phosphorus on NiO-Al₂O₃ in CO₂ hydrogenation is observed. All the catalysts reach the highest conversion at 600 °C with 61.54 %, 62.89 %, 63.88 % and 66.13 % respectively for 5 wt% NiO-Al₂O₃, 5 wt% NiO-5P-Al₂O₃, 5 wt% NiO-15P-Al₂O₃ and 5 wt% NiO-20P-Al₂O₃ catalysts. Ni/NiO/Ni₂P/Ni₅P₁₂/AlPO₄ interfacial species were detected on the surface as active species on the used catalysts by X-ray photoelectron spectroscopy. The formation ratio of the metal-phosphide is relatively low ∼3−5 %, and this atomic concentration is decreasing with the rising of the phosphate content. However, the nickel enrichment in the surface layer presumable in Ni₂P/Ni₅P₁₂ form is very likely according to the P 2p spectra and the authors assume that could be responsible for the enhanced catalytic activity.