• Korean Chemical Engineering Research
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• v.49 no.6
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• pp.720-725
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• 2011

Gold catalysts supported on metal-oxides were prepared by co-precipitation using the various metal nitrates and chloroauric acid as precursors, and effect of water addition on the catalytic activity in CO oxidation was investigated. Among the various supported gold catalysts, Au/$Co_{3}O_{4}$ and Au/ZnO catalysts showed the excellent activity for CO oxidation. Water in the reactant gas had a negative effect on the oxidation activity over Au/$Co_{3}O_{4}$ catalysts and a positive effect on that over Au/ZnO, which means the activity depends strongly on the nature of support. It was also confirmed that no significant change in the particle size of gold was observed after reaction both in dry and wet conditions. This fact suggested that the deactivated catalyst due to a carbonate species could be regenerated by water addition in the reactant gas.

• Bulletin of the Korean Chemical Society
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• v.26 no.12
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• pp.1925-1926
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• 2005

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.264-264
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• 2012

As an environment-friendly alternative energy resource, ethanol may be used to obtain hydrogen, a clean energy source. Thus, studies on catalytic reactions involving ethanol have been studied to understand the underlying principles in the reaction mechanism using various oxide-supported catalysts. Among them, Au-based catalysts have shown a superior activity in producing hydrogen gas. In the present study, Au/$TiO_2$ catalysts were prepared by deposition-precipitation method to understand their catalytic activities toward ethanol and acetaldehyde with increasing gold loading, especially at the very low Au loading regime. A commercially available $TiO_2$ (Degussa P-25) was employed and the Au loading was varied to 0, 0.1, 0.5, and 1.0 wt% respectively. The catalysts showed characteristic x-ray diffraction (XRD) features at $2{\theta}=78.5^{\circ}$ that could be assigned to the presence of gold nanoparticles. Its reactivity measurements were performed under a constant flow of ethanol and acetaldehyde at a flow rate of ${\sim}0.6{\mu}mol/sec$ and the substrate temperature was slowly raised at a rate of 0.2 K/sec. We observed that the overall reactivity of the catalysts increased with increasing Au loading along with selectivity favoring dehydrogenation to product hydrogen gas. In addition, we disclosed various reaction channels involving competitive reaction paths such as dehydrogenation, dehydration, and condensation. In addition, subsequent reactions of acetaldehyde obtained from dehydrogenation of ethanol, were found to occur and produce butene, crotonaldehyde, furan, and benzene. Based on the results, we proposed overall reaction pathways of such reaction channels.

• Bulletin of the Korean Chemical Society
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• v.32 no.spc8
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• pp.2867-2868
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• 2011

• Bulletin of the Korean Chemical Society
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• v.31 no.6
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• pp.1465-1466
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• 2010

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.213-213
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• 2011

Gold catalysts supported on TiO2 have shown a unique catalytic behavior on CO oxidation, depending on surface effects. Particle size has an influence on the surface activity. To make monodisperse Au nanoparticles, organic capping ligands, such as alkylthiols, were used by a "greener" synthesis method [1,2] and Au nanoparticles were deposited on TiO2. However, organic capping ligands must be removed for high catalytic activities by the Au nanoparticles without changing the Au size [3]. We used UV ozone treatment to decompose thiol ligands. The samples have been characterized by X-ray photoelectron spectroscopy to examine the surface modification by UV ozone treatment. We show the size distribution of the gold nanoparticles by light scattering analysis and transmission electron microscopy. Au/TiO2 have been prepared using the wetness impregnation method. The catalytic performance of CO oxidation over Au supported on TiO2 under oxidizing reaction conditions (40 Torr CO and 100 Torr O2) were tested. The results show that the catalytic activity depends on particle size and the time of UV ozone exposure, which suggests the role of sulfur bonding in determining the catalytic activity of Au/TiO2 catalysts.

• Applied Chemistry for Engineering
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• v.10 no.7
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• pp.1003-1007
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• 1999

The activity and products distribution for the hydrogenation of butadiene and pentadiene over the gold and cobalt catalysts prepared by coprecipitation and impregnation method was investigated with using a flow reactor under atmospheric pressure. The reaction characteristics of the highly dispersed gold particles and its role were studied. The activity of the gold catalyst by coprecipitation was much higher than that by impregnation. The selectivity of butene on all gold particles was always 100% even in the absence of butadiene in the stream, but butadiene on cobalt supported catalyst was easily hydrogenated to butane. It was therefore considered that the active sites at circumferences of the gold particles possessed an unique property which took a proper affinity to hydrogen. In the hydrogenation of butadiene and pentadiene, the percentages of 1-butene and 2-pentene were 60%~70% and about 62%, respectively. The results could be simply explained by a statistical concepts of hydrogen addition.

• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.6
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• pp.739-749
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• 2009

Ever since gold was found, this element has fascinated human beings. It is stable in air, and is illuminating for several thousands years without changing its colors. Nanoparticles are the basic nanommaterials, and, particularly gold nanoparticles show unique properties which are not shown in bulk states. Scientists are trying to apply these new properties to catalysts, bioscience, optics, etc. Judging from the current research activities, one can envisage that gold nanoparticles can play a major role in opening a new era in diagnoses and treatment of diseases like cancers. However to apply the nanoparticles one must modify the surface of the nanoparticles in order to give the materials certain functionalities. It certainly is worth to review the current research status and challenges in the area of functional gold nanoparticles.

• Resources Recycling
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• v.27 no.6
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• pp.76-83
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• 2018

This article aims to summarize the scrap recycling status of gold, silver, platinum and palladium from foreign countries by courntires and industries in order to utilize the data for securing the raw materials of the domestic urbanmining industry. The amount of gold from scrap has shown a tendency to decrease in countries other than China, which is attributed to the large imports of scrap containing gold in China. The industry demand for gold is the highest in electronic products, but demand is decreasing. The amount of scrap recycling in silver has declined in other regions compared to those in Europe, indicating that the world's overall scrap recycling volume has declined. Production and demand from scrap of platinum and palladium are mostly for catalysts and have been steadily increasing until now. However, it is expected that the amount of waste catalysts in automobiles will decrease with the increase of electric vehicle use.

• Applied Chemistry for Engineering
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• v.5 no.2
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• pp.285-294
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• 1994

Some supported gold catalysts were prepared by impregnation and coprecipitation methods. Effect of gold addition and active sloe formation were studied by investigating particle sizes of gold, amounts of oxygen adsorbed, adsorption properties of CO and NO, and reduction and oxidation properties, etc.. The gold particles of the catalyst by impregnation were irregular and very large as 30~100 nm, but those by coprecipitation were uniform and ultra-fine as about 4 nm. On $Au/Al_2O_3$ catalyst, the addition of gold to inactive $Al_2O_3$ caused the decomposition of $N_2O$, and CO was not irreversibly adsorbed while $O_2$ was atomically and irreversibly adsorbed. The adsorption sites of oxygen were attributed to the active sites which were restricted to the circumference of hemispherical gold particle-support interface rather than all atoms on the surface of gold particle. Also, CO was reversibly and irreversibly adsorbed on $Al_2O_3$ at low temperature, and the addition of gold weakened both reversible and irreversible adsorptions. The affinity for CO on $Au/Co_3O_4$ catalyst decreased conspicuously compared to $Co_3O_4$. The effect of gold addition did not appear in reduction step but did remarkably in reoxidation step; the added gold promoted the reoxidation of the reduced cobalt atoms.