Reduction of CuO-containing catalysts, CuO: I: TPR and TGA

Boyce, A. L.; Graville, S. R.; Sermon, Paul A.; Vong, M. S. W.

doi:10.1007/bf02068376

Cited by 26 publications

(14 citation statements)

References 10 publications

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“…Higher values of activation energies of approximately 60–80 kJ mol −1 have also been reported previously for pure CuO as well as for supported systems 34. 40, 41…”

Section: Resultssupporting

confidence: 80%

Synthesis and Characterisation of a Highly Active Cu/ZnO:Al Catalyst

et al. 2014

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We report the application of an optimised synthesis protocol of a Cu/ZnO:Al catalyst. The different stages of synthesis are all well-characterised by using various methods with regard to the (micro-)structural, textural, solid-state kinetic, defect and surface properties. The low amount of the Al promoter (3 %) influences but does not generally change the phase evolution known for binary Cu/ZnO catalysts. Its main function seems to be the introduction of defect sites in ZnO by doping. These sites as well as the large Cu surface area are responsible for the large N₂O chemisorption capacity. Under reducing conditions, the Al promoter, just as Zn, is found enriched at the surface suggesting an active role in the strong metal–support interaction between Cu and ZnO:Al. The different stages of the synthesis are comprehensively analysed and found to be highly reproducible in the 100 g scale. The resulting catalyst is characterised by a uniform elemental distribution, small Cu particles (8 nm), a porous texture (pore size of approximately 25 nm), high specific surface area (approximately 120 m² g^-1), a high amount of defects in the Cu phase and synergetic Cu–ZnO interaction. A high and stable performance was found in methanol synthesis. We wish to establish this complex but well-studied material as a benchmark system for Cu-based catalysts

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“…Higher values of activation energies of approximately 60–80 kJ mol −1 have also been reported previously for pure CuO as well as for supported systems 34. 40, 41…”

Section: Resultssupporting

confidence: 80%

Synthesis and Characterisation of a Highly Active Cu/ZnO:Al Catalyst

et al. 2014

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“…3.3 × 10 -2 mg min -1 . Previous TPR studies of unsupported CuO have reported a wide variety of peak temperatures including 187, 320, and 333 °C 24 when using a katharometer to monitor H 2 uptake under linear heating conditions. Comparison of peak temperatures is difficult because of different experimental and pretreatment conditions employed by the various workers .…”

Section: Resultsmentioning

confidence: 99%

New Approach to the Investigation of Mechanisms and Apparent Activation Energies for the Reduction of Metal Oxides Using Constant Reaction Rate Temperature-Programmed Reduction

1998

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A new system has been developed for the study of both bulk and surface metal oxides by temperature programmed reduction (TPR) under both conventional linear heating and constant rate thermal analysis (CRTA) conditions. It is shown that constant rate temperature-programmed reduction (CR-TPR) is capable of producing higher resolution of overlapping events, provides more insight into reduction mechanisms, and allows easier quantification of reduction processes than conventional TPR. The CR-TPR curves for both bulk and supported copper oxides confirmed that reduction followed a nucleation or autocatalytic mechanism. Bulk nickel oxide was found to reduce via a similar mechanism. Advantages of the CR-TPR “rate-jump” technique to determine reaction energetics are illustrated by investigation of the apparent activation energy (E a) of CuO reduction, and the results are compared with those obtained under linear heating conditions. Both approaches yield reasonable values of E a under the appropriate experimental conditions employed. However, the CR-TPR “rate-jump” technique allows variations in E a to be measured as a function of the extent of reduction, revealing changes in the reaction mechanism or kinetics. Our results suggest it is possible to estimate the apparent activation energy of both the nucleation and growth stages involved in reduction. The validity of the “rate-jump” technique employed is confirmed using the thermal decomposition of CaCO3, a widely investigated process. The TPR system uses a hygrometer cell to monitor the production of H2O as the sample is reduced. The sample temperature is controlled by a computer in such a way that the production of H2O, i.e., the rate of reduction, can be maintained at a constant preselected value for CR-TPR experiments. Important instrumental features include a fast response furnace, direct temperature measurement, a sensitive specific detector, and control and data analysis software developed specifically for this work.

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“…In turn, ceria affects the reducibility of metal oxides supported on it [22,26,29,30,33,37]. Fierro et al [35], Boyce et al [36] and Barrault et al [34] investigated the TPR profiles of CuO and NiO particles on different supports, such as CeO 2 , Al 2 O 3 and SiO 2 . Bulk CuO is reduced at 200-300 • C, while NiO is reduced at 300-400 • C.…”

Section: Catalyst Reactivity and Characterizationmentioning

confidence: 99%

Low-temperature water-gas shift reaction over Cu- and Ni-loaded cerium oxide catalysts

Flytzani‐Stephanopoulos

2000

Applied Catalysis B: Environmental

778

411

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In this paper we report on the activity of Cu-and Ni-containing cerium oxide catalysts for low-temperature water-gas shift (WGS). Bulk catalysts were prepared in nanocrystalline form by the urea co-precipitation-gelation method. Lanthanum dopant (10 at.%) was used as a structural stabilizer of ceria, while the content of Cu or Ni was in the range of 5-15 at.% (2-8 wt.%). At low metal loadings, Cu or Ni were present in the form of highly dispersed oxide clusters, while at high loadings, clusters as well as particles of CuO or NiO (>10 nm in size) were present on ceria. Both Cu and Ni increased the reducibility of ceria, as evidenced by H 2 -TPR experiments. The WGS reaction activity of Ce(La)O x was increased significantly by addition of a small amount (2 wt.%) of Cu or Ni. The catalysts were not activated prior to testing. Steady-state WGS kinetics were measured over the temperature range of 175-300 and 250-300 • C, respectively, for Cu-and Ni-Ce(La)O x . The activation energy of the reaction over Ce(La)O x was 58.5 kJ/mol, while it was 38.2 and 30.4 kJ/mol, respectively, over the 5 at.% Ni-Ce(La)O x and 5 at.% Cu-Ce(La)O x catalysts in CO-rich conditions. A co-operative redox reaction mechanism, involving oxidation of CO adsorbed on the metal cluster by oxygen supplied to the metal interface by ceria, followed by H 2 O capping the oxygen vacancy on ceria, was used to fit the kinetics. Parametric studies were mainly performed with the 5 at.% Cu-(La)O x catalyst. Notably, this material requires no activation and retains high WGS activity and stability at temperatures up to 600 • C.

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Reduction of CuO-containing catalysts, CuO: I: TPR and TGA

Cited by 26 publications

References 10 publications

Synthesis and Characterisation of a Highly Active Cu/ZnO:Al Catalyst

Synthesis and Characterisation of a Highly Active Cu/ZnO:Al Catalyst

New Approach to the Investigation of Mechanisms and Apparent Activation Energies for the Reduction of Metal Oxides Using Constant Reaction Rate Temperature-Programmed Reduction

Low-temperature water-gas shift reaction over Cu- and Ni-loaded cerium oxide catalysts

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