Peculiarities of formation of ZnO and CuO-based solid solutions

Ketchik, S. V.; Minyukova, T. P.; Кузнецова, Л. И.; Plyasova, L. M.; Yurieva, T. M.; Боресков, Г. К.

doi:10.1007/bf02074059

“…It has been reported that reduction of CuO in a binary catalyst is retarded compared with pure CuO [62,73,157,162,164,168,169], whereas it is accelerated in ternary catalysts [169]. CO reduces CuO faster than H 2 , especially in the final stages of the reduction where it is believed that the presence of hydroxyl groups on the surface of the catalyst inhibits the reduction by H 2 [167,170].…”

Section: Other Catalystsmentioning

confidence: 99%

Methanol Synthesis

Hansen¹,

Nielsen²

2008

Handbook of Heterogeneous Catalysis

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The sections in this article are Introduction Thermodynamics Methanol Synthesis Catalysts Introduction Zn O / Cr 2 O 3 Catalyst Copper‐Based Catalysts Cu / Zn O + Element ( Al , Cr , … ) Promotion of Cu / Zn O / MOx Catalysts Cu / Zr O 2 Other Cu , Cu / Me , Cu / Me Ox Catalysts Pd ‐Based Catalysts Sulfide Catalysts Other Catalysts Activation of Cu / Zn Catalyst Activity as a Function of the Nature of Copper‐Based Catalysts Catalyst Deactivation Sintering Sulfur Poisoning Other Poisons By‐Product Formation Reaction Mechanism(s) and Active Sites Cu + in a Zn O Matrix as the Active Center The S chottky Junction Theory Partly Oxidized Copper Independent of Support as Active Sites Metallic Copper in Dynamic Interaction with the Support Cu –Zinc Surface Alloy Model Water Gas Shift Reaction Kinetics Reaction Rate Equations Diffusion Restrictions Kinetics in Slurry Phase Methanol Synthesis Methanol Synthesis Technology Synthesis Gas Preparation Natural Gas Reforming Adiabatic Pre‐Reforming Tubular, Fired Reforming Autothermal Reforming and Oxygen‐Fired Secondary Reforming Gasification of Heavy Oil, Coal or Biomass Coproduction in Ammonia Plants and Use of Off‐gases Economics of Synthesis Gas Preparation Reactor Systems and Synthesis Loop Layout Slurry Phase Reactor Types Methanol Purification Concepts Circumventing the Equilibrium Limitations Other Methanol Synthesis Routes and Technologies Methanol Synthesis by Methane Activation Conclusion

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“…There are no significant differences between the catalyst and ZnO reference spectrum at the Zn L 2,3 -edge. EEL spectra at the C K-edge were acquired from a sample dispersed on a plasmacleaned steel grid in order to search for the presence of residual CO 3 2À , which was reported by Ketchik et al (1982). No carbon signal was observed in any part of the as-prepared catalyst.…”

Section: Figure 10mentioning

confidence: 99%

“…There appears to be wide agreement that the oxide catalyst formed by calcining coprecipitated (Cu,Zn)hydroxycarbonates contains ZnO with Cu in solid solution, and that Cu migrates to the ZnO surface during the reduction process, forming dispersed structures with particularly high catalytic activity (Ketchik et al, 1982;Yurieva et al, 1993Yurieva et al, , 1995Stirling et al, 1993;Plyasova, 1996;Poels & Brands, 2000). Stirling et al (1993) found that a maximum of about 1 mol% CuO can dissolve in ZnO, but they calcined the studied catalysts at very high temperatures, 1053-1173 K, whereas Ketchik et al (1982) showed that ZnO in catalysts calcined at 623 K may contain up to 10 mol% CuO in solid solution. Klenov et al (1998) and Yurieva et al (2004) suggested, by a combination of HRTEM (high-resolution transmission electron microscopy) and X-ray diffraction measurements and simulations, that the Cu-doped ZnO contains a large number of defects along the (001) plane and that Cu atoms are primarily located close to these defects.…”

Section: Introductionmentioning

confidence: 95%

Activation of a Cu/ZnO catalyst for methanol synthesis

Andreasen¹,

Rasmussen

²

,

Helveg

³

et al. 2006

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SynopsisIn situ resonant X-ray diffraction, in situ resonant small angle X-ray scattering and in situ electron energy loss spectroscopy have been applied to the study of nano-scale and crystalline structure during activation of a Cu/ZnO catalyst for methanol synthesis. AbstractThe structural changes during activation by temperature programmed reduction of a Cu/ZnO catalyst for methanol synthesis has been studied by several in situ techniques.

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“…Several types of crystalline solid solutions formed during the preparation of Cu/ZnO catalysts have already been reported in the literature: Cu 2+ /ZnO, Cu 1+ /ZnO, and Zn 2+ /CuO. [32][33][34][35][36][37] Although temperatures as different as 350°C 37 and 1000°C [34][35][36] have been reported for the formation of the last solid solution, all authors agree upon a very low solubility limit of 3-5 mol % Zn 2+ in the tenorite structure.…”

Section: Overview Of the Structures Formed By Ball Millingmentioning

confidence: 99%

Highly Mixed Phases in Ball-milled Cu/ZnO Catalysts: An EXAFS and XANES Study

Grandjean

¹

,

Castricum

²

,

Heuvel

³

et al. 2006

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New highly mixed phases have been identified in Cu/ZnO systems by EXAFS and XANES at both the Cu and Zn K-edge. The phases were generated by ball-milling Cu 2 O/ZnO mixtures under three different atmospheres of synthetic air (SA), SA + CO 2 and CO 2 . The system milled in CO 2 shows disproportionation of Cu 2 O into Cu 0 , Cu 1+ (cuprite Cu 2 O-type phase) and Cu 2+ (tenorite CuO-type phase), while most of the Zn 2+ is transformed into a nanocrystalline/amorphous ZnO-type zincite that forms a superficial mixture of oxide and carbonate phases. When synthetic air is added to the CO 2 atmosphere, ball milling results in the oxidation of nearly half the Cu 1+ into Cu 2+ with no Cu metal formed. The copper phase in this material is almost entirely amorphous. In SA, a significant amount of Cu 2+ -and Zn 2+ -based phases appears to react to form a nanocrystalline/amorphous Cu 1-x Zn x O (x ≈ 0.3) solid solution. This distorted rock saltlike solid solution, in which Zn and Cu feature different octahedral environments, was never reported before. It is thought to be formed by incorporation of Zn 2+ in the Cu fcc sublattice of the cuprite Cu 2 O matrix and the concomitant oxidation of Cu 1+ into Cu 2+ . The formation of such a highly mixed Cu 1-x Zn x O phase indicates strong Cu/Zn interaction in the Cu/ZnO system, which also suggests the presence of highly mixed phases in conventionally prepared activated catalysts.

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Peculiarities of formation of ZnO and CuO-based solid solutions

Cited by 37 publications

References 1 publication

Methanol Synthesis

Methanol Synthesis

Activation of a Cu/ZnO catalyst for methanol synthesis

Highly Mixed Phases in Ball-milled Cu/ZnO Catalysts: An EXAFS and XANES Study

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