Following Cu Microstructure Evolution in CuZnO/Al₂O₃(−Cs) Catalysts During Activation in H₂ using in situ XRD and XRD‐CT

Abstract

Understanding how the microstructure of the active Cu 0 component in the commercially applicable Cu/ZnO/ Al 2 O 3 (À Cs 2 O) low-temperature water-gas shift catalyst evolves under various H 2 partial pressures in the presence/absence of a Cs promoter during thermal activation has been investigated. Time-resolved XRD and spatially-resolved XRD-CT data were measured as a function of H 2 concentration along a packed bed reactor to elucidate the importance of the zincite support and the effect of the promoter on Cu sintering mechanisms, dislocation character and stacking fault probability. The rate of Cu reduction showed a dependency on [Cs], [H 2 ] and bed height; lower [Cs] and higher [H 2 ] led to a greater rate of metallic copper nanoparticle formation. A deeper analysis of the XRD line profiles allowed for determining a greater edge character to the dislocations and subsequent stacking fault probability was also observed to depend on higher [H 2 ], smaller Cu 0 (and ZnO) crystallite sizes, increased [ZnO] (30 wt.%, sCZA) and lower temperature. The intrinsic activity of Cu/ZnO/Al 2 O 3 methanol synthesis catalysts has been intimately linked to the anisotropic behaviour of copper, and thus the presence of lattice defects; to the best knowledge of the authors, this study is the first instance in which this type of analysis has been applied to LT-WGS catalysts.

Recent developments in X-ray diffraction/scattering computed tomography for materials science

“…A considerable number of in situ catalytic XRD-CT studies have been performed at beamlines ID11, ID15A and ID31 of the ESRF, many by the Beale group, on aspects of oxidative coupling of methane (OCM) [113][114][115][116][117], partial oxidation (POX) of methane [28,118], CO 2 methanation [119], the low-temperature water-gas shift [120] and gas separation catalysts [121]. The catalytic conundrum that is coking has also been studied [122].…”