Showing papers by "Masatake Haruta published in 1993"
TL;DR: In this paper, the hydrogenation of CO 2 on supported gold catalysts was investigated at temperatures between 150 and 400° C and a pressure of 8 atm, with the highest yield and selectivity towards methanol obtained on Au/ZnO at 250°C.
Abstract: Gold highly dispersed on a variety of metal oxides were prepared by coprecipitation and deposition-precipitation methods. The hydrogenation of CO 2 on supported gold catalysts was investigated at temperatures between 150 and 400° C and a pressure of 8 atm. The methanoi yields reached a maximum at temperatures between 200 and 300 ° C, depending on the support oxides. The highest yield and selectivity towards methanol was obtained on Au/ZnO at 250°C. At 200°C Au/Fe 2 O 3 was the most active for methanol synthesis, exhibiting activity almost comparable to that of the conventional Cu/ZnO catalyst with the same metal content. Gold supported on TiO 2 was so active in reducing CO 2 to CO that the conversion was close to equilibrium. Over Au/ZnO as well as over Cu/ZnO, CO 2 could be hydrogenated to methanol at lower temperatures than CO.
144 citations
TL;DR: Titania-supported gold catalysts calcined under vacuum have been studied using a combination of TEM and activity measurements for CO oxidation as mentioned in this paper, indicating that not only the size of gold particles but also the oxidized state of the support surface is important.
Abstract: Titania-supported gold catalysts calcined under vacuum have been studied using a combination of TEM and activity measurements for CO oxidation. A time dependent study by TEM suggested the presence of highly dispersed gold, a high percentage of which lies below the 1 nm resolution limit. A comparison between Au/TiO2 samples calcined in vacuum and air has shown large differences in catalytic behaviour, indicating that not only the size of gold particles but also the oxidized state of the support surface is important.
46 citations
TL;DR: In this article, the absorption spectra of 12 CO and 12 CO - 13 CO mixture were examined at different equilibrium pressures at room temperature, and two kinds of chemically active sites, strongly coupled and interacting were evidenced.
44 citations
31 citations
26 citations
TL;DR: In this paper, a mechanism is proposed in which CO adsorbed on gold migrates toward the support oxide and there reacts with O2− to form bidentate carbonate species.
Abstract: Among gold catalysts supported on Co3O4, α-Fe2O3, and TiO2, turnover frequencies for CO oxidation based on surface gold atoms were almost independent of the catalytic activity of support oxides but significantly dependent on the diameter of gold particles. The rate of CO oxidation is independent or only slightly dependent on the concentration of CO and O2. A mechanism is proposed in which CO adsorbed on gold migrates toward the support oxide and there reacts with adsorbed O2− to form bidentate carbonate species.
16 citations
TL;DR: The catalytic properties of supported gold are tunable through the appropriate selection of metal oxide as a support as discussed by the authors, which can be achieved by depositing gold as very small particles with diameters below 4nm.
Abstract: The catalytic nature of supported gold is, in principle, tunable through the appropriate selection of metal oxide as a support The catalytic activities can be markedly increased by depositing gold as very small particles with diameters below 4nm It is proposed for the low temperature oxidation of CO that the synergistic effect is due to the gold-metal oxide interfacial perimeter, which can provide adsorption sites for oxygen at room temperature
16 citations
TL;DR: In this article, a model that describes CO oxidation through reversible adsorption at the Au particle was presented, and the significant synergy observed can be ascribed to the enhancement of oxygen adoration at the interfacial perimeter.
Abstract: Gold supported on TiO 2 with different particle sizes (3—20nm) and loadings of Au can be reproducibly prepared by deposition-precipitation, through changing the pH of an aqueous solution of HAuCl 4 . With solutions where the pH is higher than 6, gold can be deposited on TiO 2 with high dispersion and exhibits a marked enhancement in catalytic activity for CO oxidation even below room temperature. The significant synergy observed can be ascribed to the enhancement of oxygen adsorption at the interfacial perimeter. A model is presented that describes CO oxidation through reversible adsorption at the Au particle.
15 citations
TL;DR: Au L3 XAFS study was made of ultra-fine gold particles supported on beryllium hydroxide (Au/Be(OH)2) and magnesium hydroxides(Au /Mg(O)2), and it was proposed that catalytic activity for CO oxidation arises from the presence of Au-Au coordination in Au/Be (OH) 2 and Au/Mg (O) 2 as mentioned in this paper.
Abstract: Au L3 XAFS study was made of ultra-fine gold particles supported on beryllium hydroxide (Au/Be(OH)2) and magnesium hydroxide(Au/Mg(OH)2). It is proposed that catalytic activity for CO oxidation arises from the presence of Au-Au coordination in Au/Be(OH)2 and Au/Mg(OH)2 although in the latter Au-Au and Au-O coordination coexist in the most active catalysts.
6 citations
31 Dec 1993
TL;DR: In this paper, it was found that the catalytic nature of supported gold depends on the kind of metal oxide supports and the interfacial perimeter between gold particles and metal oxide support and the size of gold particles.
Abstract: Small gold particles deposited on metal oxides exhibit extraordinarly high catalytic activities. For example, Au/{alpha}-Fe{sub 2}O{sub 3} can catalyze the oxidation of CO at a temperature as low as {minus}70{degrees}C. The reaction is not retarded by accelerated by moisture contained in reaction gases. These unique properties of supported gold catalysts show a potential of their applications in a variety of environmental problems. It has been found that the catalytic nature of supported gold depends on the kind of metal oxide supports. Some examples of the suitable supports are: NiFe{sub 2}O{sub 4} for NO{sub x} reduction by CO and the oxidation-decomposition of trimethylamine; Co{sub 3}O{sub 4} for the complete oxidation of CH{sub 4} and C{sub 3}H{sub 8}; ZnO and TiO{sub 2} for CO{sub 2} hydrogenation. It appears that the interfacial perimeter between gold particles and metal oxide support and the size of gold particles play the most important role in determining the catalytic nature and the activity.
2 citations