Gold nanoparticles: Support effects for the WGS reaction

Gold nanoparticles supported on reducible (TiO2 and CeO2) and non-reducible oxides (Al2O3 and SiO2) with comparable gold particle size (2.5–3.5 nm) were studied as catalysts in the WGS reaction. Deposition–precipitation with urea (DP Urea) was used to prepare gold nanoparticles supported on TiO2, CeO2 and Al2O3. Cationic adsorption was used as preparation method in the case of SiO2. Metal loading was fixed to 4 and 8 wt.%. The WGS reaction was studied in the temperature range from 50 to 400 °C in a flow reactor at atmospheric pressure. Before reaction the samples were calcined at 200, 300 or 400 °C to study the effect of calcination temperature in the catalyst activity. The Au/CeO2 catalyst showed an enhanced reduction at low-temperatures as evidenced by the H/Au ratio. The lowest reduction temperature was observed for gold in the Au/TiO2 catalyst. When supported on TiO2 and CeO2, the activity of gold nanoparticles was much higher than the one observed when supported on Al2O3 and SiO2 being the Au/SiO2 catalyst practically inactive. For samples calcined at 300 °C and reaction temperatures below 225 °C the activity varied as follows: TiO2 > CeO2 ≫ Al2O3. CO adsorption in the presence of H2O was followed by DRIFT. Bands coming from C–H stretching associated to formate species were clearly observed on CeO2. Intensity of these bands decreased when Au is present on the supports. Au0-CO adsorption band was evidenced when Au is supported on TiO2, CeO2 and Al2O3. Fast conversion of formate species in Au/TiO2 and Au/CeO2 takes place and this explains the higher activity displayed by these catalysts.

Graphical abstractGold nanoparticles supported on reducible and non-reducible oxides with comparable gold particle size were studied in the WGS reaction. The activity of Au on reducible oxides was much higher than the one observed on non-reducible oxides. The optimum calcination temperature was 300 °C. For samples calcined at 300 °C and reaction temperatures below 225 °C the activity varied as follows: TiO2 > CeO2 ≫ Al2O3 ≫ SiO2.Figure optionsDownload full-size imageDownload as PowerPoint slide