Highly Dispersed Gold on Zirconia: Characterization and Activity in Low‐Temperature Water Gas Shift Tests

Abstract

Gold-loaded zirconia and sulfated zirconia catalysts were tested in the low-temperature water gas shift reaction. The samples were characterized by N2 adsorption analysis, temperature-programmed reduction, X-ray diffraction, pulse-flow CO chemisorption, FTIR spectroscopy, and high-resolution transmission electron microscopy. A reference catalyst, Au/TiO2, provided by the World Gold Council was investigated for comparison. CO chemisorption and FTIR data indicate the presence of only highly dispersed gold clusters on the sulfated sample and both small clusters and small particles on the non-sulfated sample. Both gold-zirconia catalysts are much more active than the Au/TiO2 reference sample over all the temperature range investigated. The sample prepared on sulfated zirconia exhibits higher stability than the catalyst on unmodified zirconia. The prominent role in the water gas shift reaction of gold clusters in close contact with the support was deduced.

Investigation on gold dispersion of Au/ZrO2 catalysts and activity in the low-temperature WGS reaction

“…It was found that the ZrO 2 /SO 4 = support after calcination contains a 2 wt% of sulfates. On the contrary, as previously reported [16,21], tests of sulfates carried out on the samples after deposition of gold, evidence that no sulfates are present in the final catalysts anymore. This is not unexpected, pointing out that the detachment of sulfate groups occurs during the deposition-precipitation, as a consequence of the basic conditions.…”

“…These species coming from the Na 2 CO 3 used for the depositionprecipitation can occupy active sites on gold particles, thus worsening their ability to chemisorb CO molecules and their activities. Further catalytic tests have been performed on these catalysts to evaluate the stability of the Au/ZrO 2 system in the water-gas shift reaction: CO conversion was measured at the beginning and after 21 h of time on stream at 453 K. As previously reported [16] samples prepared on sulfated zirconia are more stable than the corresponding catalysts on plain zirconia. For example the 1AuZSn catalyst preserves a conversion of 87% after 21 h of reaction at 453 K.…”

“…Gold catalysts supported on Fe 2 O 3 [10], TiO 2 [11], ZnO [12], CeO 2 [13] and ThO 2 [12] showed good catalytic activity in the water-gas shift reaction. Recently gold samples supported on mesoporous zirconia have also been studied [14][15][16]. The opportunity of use ZrO 2 as support is due to its intrinsic characteristics: chemical and surface features of zirconia, as surface acidity, redox properties, porosity and surface area, can be adjusted by choosing different precursors and synthesis conditions and by dopants addition.…”

Recent Progress in Chemical Characterization of Supported Gold Catalysts: CO Adsorption on Au/Ceria–Zirconia

“…31,54 However, a far less detailed description of the relationship existing between nanostructural properties of the Au surface atoms and their chemisorptive behavior could be deduced from them.…”

Au/ZrO2 catalysts for LT-WGSR: Active role of sulfates during gold deposition

“…Characteristics such as surface area, presence of surface hydroxyl groups, density of defects, modification of the surface acidity and of the predominant crystalline phase can influence its adsorption ability [1]. We have recently focused our attention on gold based catalysts supported on zirconia [6,7]. The choice of zirconia as support is due to its intrinsic chemical and physical characteristics that can be adjusted by choosing different precursors and synthesis conditions.…”