Deactivation Mechanism of a Au/CeZrO₄ Catalyst During a Low-Temperature Water Gas Shift Reaction

Abstract

On-stream deactivation during a water gas shift (WGS) reaction over gold supported on a ceria-zirconia catalyst was examined. Although the fresh catalyst has very high low temperature (<200 °C) for WGS activity, a significant loss of CO conversion is found under steady-state operations over hours. This has been shown to be directly related to the concentration of water in the gas phase. The same catalyst also undergoes thermal deactivation above 250 °C, and using a combined experimental and theoretical approach, a common deactivation mechanism is proposed. In both cases, the gold nanoparticles, which are found under reaction conditions, are thought to detach from the oxide support either through hydrolysis, <250 °C, or thermally, >250 °C. This process reduces the metal-support interaction, which is considered to be critical in determining the high activity of the catalyst.

Ceria-zirconia supported gold catalysts

“…Thus, the authors [11] proposed that the deactivation occurs rather due to the reduction in the number of the Au interface sites, necessary to mediate the WGS reaction, than due to the decrease in Au cluster size. Similar conclusions come from the work of Goguet et al [12]. Basing on the combined experimental and theoretical approach, the authors claim that hydrolysis of the interface between the gold and the support reduces the metal -support interaction and causes the metal nanoparticle detachment from the surface.…”

“…Such unique properties of ceria-zirconia systems seem to make them ideally suited for an application as supports to gold catalysts. Surprisingly, only a few papers concerning Au/Ce x Zr 1-x O 2 catalysts [7,[9][10][11][12][13][14][15][16][17][18][19][20][21][22][23], tested mainly in the water-gas shift reaction [9][10][11][12][13][14][15][16] and low-temperature CO oxidation [10,[17][18][19][20][21][22][23] have been published so far. In this paper the most important achievements and conclusions coming from these contributions have been reviewed.…”

Screening wall effects of a thin fluidized bed by near-infrared imaging

“…The technique was extended to ceria-silica reduction, where radial profiles of water concentrations allowed the distinction between surface and bulk reduction regimes of ceria-silica packing. This design of present setup may correspond to the investigation of local catalyst deactivation by water vapour in gas-solid reactions for example in the oxidation of carbon monoxide [30], decomposition of ozone [31], low temperature water-gas-shift [32], and Fischer-Tropsch [33] but also to the control of drying of a carrier gas containing moisture in purification processes.…”

Comparative Study on Nano-Sized 1 wt% Pt/Ce0.8Zr0.2O2 and 1 wt% Pt/Ce0.2Zr0.8O2 Catalysts for a Single Stage Water Gas Shift Reaction

“…It will be useful to study the effect of the nano-sized cubic/tetragonal Ce (1 -x) Zr (x) O 2 supports on controlling the reducibility and oxygen mobility [20]. Moreover, Ce (1 -x) Zr (x) O 2 supports will help to reduce the formation of surface carbonate species, which deactivate the WGS catalyst [21].…”