A mechanistic study of methanol decomposition over Cu/SiO{sub 2}, ZrO{sub 2}/SiO{sub 2}, and Cu/ZrO{sub 2}/SiO{sub 2}
- Lawrence Berkeley National Lab., CA (United States). Chemical Sciences Div.
The interaction of methanol with Cu/SiO{sub 2}, ZrO{sub 2}/SiO{sub 2}, and Cu/ZrO{sub 2}/SiO{sub 2} has been investigated by in situ infrared spectroscopy and temperature programmed desorption and reaction with the aim of understanding the nature of the species and the mechanism involved in methanol decomposition. In the case of Cu/SiO{sub 2}, methanol exposure results in the formation of methoxide species on Cu and SiO{sub 2} at 323 K. In the absence of methanol in the gas phase, methoxide species on Cu are dehydrogenated to give formaldehyde starting at {approximately}340 K and are oxidized to formate species at {approximately} 373 K, which then decomposed to CO{sub 2} and H{sub 2} at {approximately}390 K. When methanol is present in the gas phase, methyl formate, CO, and H{sub 2}. resulting from the decomposition of methyl formate, are formed in addition to the above reactions. When ZrO{sub 2}/SiO{sub 2} or Cu/ZrO{sub 2}/SiO{sub 2} is exposed to methanol, the majority of the surface species observed are associated with zirconia. Methanol adsorption on either ZrO{sub 2}/SiO{sub 2} or Cu/ZrO{sub 2}/SiO{sub 2} leads to methoxide formation on zirconia and SiO{sub 2} at 323 K. In the presence of Cu, methoxide species on zirconia are dehydrogenated to give formaldehyde starting at {approximately}325 K, which is oxidized to formate species on zirconia at {approximately}373 K, which decompose to CO, CO{sub 2}, and H{sub 2} at {approximately}400 K. Methyl formate and dimethyl ether are also observed to form above 460 K. In the absence of Cu, methoxide species on zirconia decompose only very slowly at 523 K. Metallic Cu is proposed to provide sites on which hydrogen atoms formed during the dehydrogenation of species located on zirconia can recombine efficiently and desorb as H{sub 2}. Thus, methanol decomposition over Cu/ZrO{sub 2}/SiO{sub 2} is envisioned to occur primarily on ZrO{sub 2}, with the primary function of Cu being the removal of hydrogen.
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 362059
- Journal Information:
- Journal of Catalysis, Vol. 184, Issue 2; Other Information: PBD: 10 Jun 1999
- Country of Publication:
- United States
- Language:
- English
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