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  • 1
    Electronic Resource
    Electronic Resource
    Methanol synthesis by the hydrogenation of CO2 over Zn-deposited Cu(111) and Cu(110) surfaces (1995)
    Springer
    Catalysis letters 35 (1995), S. 297-302 
    Details
    ISSN: 1572-879X
    Keywords: methanol synthesis ; Cu(111) ; Cu(110) ; Zn deposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The hydrogenation of CO2 over Zn-deposited Cu(111) and Cu(110) surfaces was performed at 523 K and 18 atm using a high pressure flow reactor combined with XPS apparatus. It was shown that the ZnO x species formed on Cu(111) during reaction directly promoted the methanol synthesis. However, no such promotional effect of the Zn was observed for methanol formation on Cu(110). Thus, Zn on Cu(111) acts as a promoter, while Zn on Cu(110) acts as a poison. The activation energy and the turnover frequency are in fairly good agreement with those obtained for Cu/ZnO powder catalysts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00807186
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Methanol synthesis over a Zn-deposited copper model catalyst (1995)
    Springer
    Catalysis letters 31 (1995), S. 325-331 
    Details
    ISSN: 1572-879X
    Keywords: methanol synthesis ; copper catalyst ; role of ZnO ; XPS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Methanol synthesis by the hydrogenation of CO2 over Zn-deposited polycrystalline Cu was studied using surface science techniques. The Zn sub-monolayer was oxidized by the reaction mixture during the reaction at 523 K, leading to the formation of ZnO species. The kinetic results definitely showed that the ZnO species on the Cu surface promoted the catalytic activity of methanol formation, where the activity of Cu increased by a factor of 6 at the Zn coverage of 0.17. A volcano-shaped curve was obtained for the correlation between the Zn coverage and the catalytic activity, which was very similar to the correlation curve between the oxygen coverage and the specific activity for methanol formation previously obtained for the Cu powder catalysts. The role of ZnO in Cu/ZnO based catalysts was ascribed to the stabilization of Cu+ species by the ZnO moieties on the Cu surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00808596
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Evidence for the migration of ZnOx in a Cu/ZnO methanol synthesis catalyst (1994)
    Springer
    Catalysis letters 27 (1994), S. 67-78 
    Details
    ISSN: 1572-879X
    Keywords: methanol synthesis ; Cu/ZnO catalyst ; Cu-Zn alloy ; effect of reduction temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The behavior and role of ZnO in Cu/ZnO catalysts for the hydrogenations of CO and CO2 were studied using XRD, TEM coupled with EDX, TPD and FT-IR. As the reduction temperature increased, the specific activity for the hydrogenation of CO2 increased, whereas the activity for the hydrogenation of CO decreased. The EDX and XRD results definitely showed that ZnO x (x = 0–1) moieties migrate onto the Cu surface and dissolve into the Cu particle forming a Cu-Zn alloy when the Cu/ZnO catalysts were reduced at high temperatures above 600 K. The content of Zn dissolved in the Cu particles increased with reduction temperature and reached ∼ 18% at a reduction temperature of 723 K. The CO-TPD and FT-IR results suggested the presence of Cu+ sites formed in the vicinity of ZnO x on the Cu surface, where the Cu+ species were regarded as an active catalytic component for methanol synthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00806979
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    The synergy between Cu and ZnO in methanol synthesis catalysts (1996)
    Springer
    Catalysis letters 38 (1996), S. 157-163 
    Details
    ISSN: 1572-879X
    Keywords: methanol synthesis ; Cu/ZnO catalyst ; effect of reduction temperature ; oxygen coverage ; physical mixture ; Cu-Zn alloy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The hydrogenation of CO2 over physically-mixed Cu/SiO2 and ZnO/SiO2 was carried out to clarify the synergetic effect between Cu and ZnO in Cu/ZnO methanol synthesis catalysts. The activity of the physical mixtures significantly increased with increasing reduction temperature in the range of 573–723 K. TEM-EDX results definitely showed that ZnOx moieties migrated from ZnO/SiO2 particles onto the surface of Cu particles when the physical mixtures were reduced at high temperatures above 573 K. Upon the migration of the ZnOx species, the oxygen coverage on the surface of Cu, measured after the hydrogenation of CO2, increased with the reduction temperature. The results clearly showed that the synergetic effect of ZnO in the physical mixtures can be ascribed to the creation of active sites such as Cu+ which the ZnOx moieties stabilize on the Cu surface. Further, XRD results showed that the migrated ZnOx species partly dissolved into the Cu particles to form a Cu—Zn alloy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00806562
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    The role of metal oxides in promoting a copper catalyst for methanol synthesis (1994)
    Springer
    Catalysis letters 25 (1994), S. 271-276 
    Details
    ISSN: 1572-879X
    Keywords: methanol synthesis ; copper catalyst ; oxygen coverage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The coverage of oxygen formed on the surface of catalysts during methanol synthesis from CO2 has been measured for copper-based catalysts including various metal oxides using a method called reactive frontal chromatography (RFC). An excellent correlation between the specific activity for methanol synthesis and the oxygen coverage (θ) was obtained, where the activity increased linearly with oxygen coverage atθ〈0.16 and then decreased atθ〉0.18. The results strongly indicate that the support effect or addition of metal oxides revealed in methanol synthesis over copper catalysts is ascribed to the ratio of Cu+ to Cu0 on the surface of copper particles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00816307
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Creation of the active site for methanol synthesis on a Cu/SiO2 catalyst (1997)
    Springer
    Catalysis letters 49 (1997), S. 175-179 
    Details
    ISSN: 1572-879X
    Keywords: methanol synthesis ; Cu/ZnO catalyst ; hydrogenation of CO2 ; role of Zn ; in situ FT-IR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effect of ZnO/SiO2 in a physical mixture of Cu/SiO2 and ZnO/SiO2 on methanol synthesis from CO2 and H2 was studied to clarify the role of ZnO in Cu/ZnO-based catalysts. An active Cu/SiO2 was prepared by the following procedure: the Cu/SiO2 and ZnO/SiO2 catalysts with a different SiO2 particle size were mixed and reduced with H2 at 523-723 K, and the Cu/SiO2 was then separated from the mixture using a sieve. The methanol synthesis activity of the Cu/SiO2 catalyst increased with the reduction temperature and was in fairly good agreement with that previously obtained for the physical mixture of Cu/SiO2 and ZnO/SiO2. These results indicated that the active site for methanol synthesis was created on the Cu/SiO2 upon reduction of the physical mixture with H2. It was also found that ZnO itself had no promotional effect on the methanol synthesis activity except for the role of ZnO to create the active site. The active site created on the Cu/SiO2 catalyst was found not to promote the formation of formate from CO2 and H2 on the Cu surface based on in situ FT-IR measurements. A special formate species unstable at 523 K with an OCO asymmetric peak at ~1585 cm-1 was considered to be adsorbed on the active site.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019069708459
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  • 7
    Electronic Resource
    Electronic Resource
    The effect of ZnO in methanol synthesis catalysts on Cu dispersion and the specific activity (1998)
    Springer
    Catalysis letters 56 (1998), S. 119-124 
    Details
    ISSN: 1572-879X
    Keywords: methanol synthesis ; Cu/ZnO catalyst ; hydrogenation of CO2 ; role of Zn
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effect of ZnO in Cu/ZnO catalysts prepared by the coprecipitation method has been studied using measurements of the surface area of Cu, the specific activity for the methanol synthesis by hydrogenation of CO2, and XRD. Although the Cu surface area increases with increasing ZnO content (0–50 wt%) as is generally known, the specific activity of the Cu/ZnO catalysts with various weight ratios of Cu:ZnO is greater than that of a ZnO-free Cu catalyst. These facts clearly indicate that the role of ZnO in Cu/ZnO catalysts can be ascribed to both increases in the Cu dispersion and the specific activity. The XRD results indicate the formation of a Cu–Zn alloy in the Cu particles of the Cu/ZnO catalysts, leading to the increase in specific activity. It is thus considered that the Cu–Zn surface alloy or a Cu–Zn site is the active site for methanol synthesis in addition to metallic copper atoms that catalyze several hydrogenation steps during the methanol synthesis. Furthermore, the advantage of the coprecipitation method through a precursor of aurichalcite is ascribed to both improvements in the Cu surface area and the specific activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019000927366
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    Paper (German National Licenses)
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