Model studies of methanol synthesis on copper catalysts
- Univ. of Tsukuba, Ibaraki (Japan)
- Research Inst. of Innovative Technology for Earth, Kyoto (Japan)
- National Inst. for Resources and Environment, Ibaraki (Japan)
The synthesis of methanol by the hydrogenation of CO{sub 2} over Zn-deposited and Zn-free copper surfaces has been studied using an XPS apparatus combined with a high-pressure flow reactor (18 atm). It was shown that the Zn deposited on Cu(111) and poly-Cu acted as a promoter for methanol synthesis, while the Zn on Cu(110) and Cu(100) had no such a promotional effect. The turnover frequency (TOF) for Zn/Cu(111) linearly increased with Zn coverage below {Theta}Zn--0.19, and then decreased above {Theta}Zn=0.20. The optimum TOF obtained at {Theta}Zn--0-19 was thirteen-fold larger than TOF for the Zn-free Cu(111) surface. On the other hand, no promotional effect of Zn was observed for the reverse water-gas shift reaction on all the surfaces. The results indicate the formation of special sites for methanol synthesis on Zn/Cu(111). The Zn-deposited Cu(111) can be regarded as a model of Cu/ZnO catalysts because the TOF and the activation energy for methanol formation over the Zn-deposited Cu(111) were in fairly good agreement with those for the Cu/ZnO powder catalysts. The post-reaction surface analysis by XPS showed the formation of formate species (HCOOa). The formate coverage was proportional to the activity for methanol formation below {Theta}Zn=0.20, suggesting that the hydrogenation of the formate species is the rate-determining step of methanol formation. The formate species was stabilized by Zn species on Cu(111) in the absence of ZnO species. STM results on the Zn-deposited Cu(111) suggested the formation of a Cu-Zn surface alloy. The presence of special sites for methanol synthesis was also indicated in the results of powder catalysts.
- OSTI ID:
- 468044
- Report Number(s):
- CONF-960652-; TRN: 96:004817-0082
- Resource Relation:
- Conference: 11. international congress on catalysis (ICC-11), Baltimore, MD (United States), 30 Jun - 5 Jul 1996; Other Information: PBD: 1996; Related Information: Is Part Of 11th International congress on catalysis - 40th anniversary. Part A and B; Hightower, J.W.; Delgass, W.N.; Iglesia, E.; Bell, A.T. [eds.]; PB: 1482 p.
- Country of Publication:
- United States
- Language:
- English
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