Silver-cluster formation on AgZr{sub 2}(PO{sub 4}){sub 3} and catalytic decomposition of butan-2-ol
- Faculte des Sciences, Rabat (Morocco); and others
A Nasicon-type AgZr{sub 2}(PO{sub 4}){sub 3} material was synthesized and its catalytic properties were characterized by butan-2-ol conversion in the presence and absence of oxygen. The catalytic activity was mainly oriented toward the production of methyl ethyl ketone and butenes. Activity was shown to depend on the reducibility of the Ag{sup +} ions and on the oxygen concentration in the reactants. Hydrogen, butan-2-ol, and butan-2-ol/O{sub 2} were able to reduce the Ag{sup +} cations located in the three-dimensional channels of the phosphate network. Silver clusters appeared on the surface and protons replaced the Ag{sup +} ions in the structure to form (HPO{sub 4}) acidic groups, without any modification in the framework of the phosphate. Evidence for this phenomenon was provided by (1) XRD peaks corresponding to (111) and (200) metallic silver diffractions, (2) UV-visible spectroscopy which showed conduction bands at 372 and 410 nm attributed to Ag{sup 0} crystallites and a shoulder in the 250-270 nm region due probably to (Ag{sub n}){sup {delta}+} charged clusters, (3) TEM analysis which revealed that the exposure of the phosphate to the electron beam produced a spontaneous appearance of silver particles, (4) IR spectroscopy which demonstrated the protonation of the sample by the appearance of three new hydroxyl bands in the 3000-3500 cm{sup -1} region, a result supported by {sup 1}HNMR spectroscopy, and (5) TPO experiments performed after the reduction of the sample which showed that silver clusters adsorb oxygen in at least two specific ways which are active in the oxidative dehydrogenation of the butan-2-ol. It was also shown that the formation of silver particles was reversible upon reoxidation at 773 K to give the starting material AgZr{sub 2}(PO{sub 4}){sub 3}. 26 refs., 10 figs., 1 tab.
- OSTI ID:
- 263782
- Journal Information:
- Journal of Catalysis, Vol. 159, Issue 1; Other Information: PBD: Mar 1996
- Country of Publication:
- United States
- Language:
- English
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