Gold catalysts, supported catalyst characterization

Vapor-phase epoxidation of propylene using H2 and O2 was carried out over gold catalysts supported on mesoporous ordered (MCM-41) and disordered titanosilicates prepared hydrothermally or by modified sol-gel method. Gold nanoparticles were homogeneously dispersed on the titanosilicate supports by deposition-precipitation (DP) method. The catalysts and support materials were characterized by XRD, UV-Vis, surface area measurements (N2 adsorption) and TEM. NaOH was found to be the best precipitant to prepare Au catalysts with optimum propylene oxide yields and H2 efficiency. The extent of catalysts washing during preparation was found to affect the activity of the catalyst. The activity and hydrogen efficiency was found to depend on the type of mesoporous support used. 

A mononuclear gold complex catalyst supported on MgO spectroscopic characterization during ethylene... 

S.Schimpf, M. Lucas, C. Mohr, U.Rodemerck, A. Bruckner, J.Radnik, H. Hofmeister, andR Claus, Supported gold nanoparticles in-depth catalyst characterization and application in hydrogenation and oxidation reactions, Catal. Today 72(1—2), 63—78 (2002). 

Guzman J, Gates BC (2004) A mononuclear gold complex catalyst supported on MgO Spectroscopic characterization during ethylene hydrogenation catalysis. J Catal 226 111... 

Obviously a controlled preparation of bimetallic catalysts is needed in order to imderstand its role upon activity, selectivity and deactivation resistance. On this way, the controlled formation of surface bimetallic particles has been reported in catalysts prepared by the redox method [1]. In the present work, in order to define the role of the redox method in the surface properties of the R-Au alumina supported catalysts, we report the preparation, characterization and catalytic properties of a set of bimetallic catalysts with different gold content. The catalysts were evaluated using methylcyclopentane (MCP) hydrogenolysis as the test reaction. 

The difference in color of the catalysts, even though the gold particle size and distribution was similar, can be explained by a different interaction between the gold particles and the supports. The most relevant results of the catalyst characterization are provided in Table 12.1. The results of the catalytic tests are summarized in Table 12.2. 

Musialska, K., Finocchio, E., Sobczak, ., era/. (2010). Characterization of alumina-and niobia-supported gold catalysts used for oxidation of glycerol, App/.Cora/. A. Gen., 384, pp. 70-77. 

Chemical Characterization of Cerium-Based Oxide-Supported Gold Catalysts... 

In recent years, the most significant progress has been made in the chemical characterization of cerium-based oxide-supported gold catalysts. There are a number of reasons that justify this observation. First, the main principles governing the chemical behaviour of the classic NM(Rh, Pd, Ptj/CeOg and ceria-related catalysts were reasonably well... 

In this section, recent progress in the chemical characterization of conventional cerium-containing oxide-supported gold powder catalysts will be briefly discussed. We will focus our attention on Hg and CO chemisorption studies. There are several reasons justifying this choice. As discussed in Bernal et Hg and CO are by far the most commonly used probe molecules in the characterization of noble metals supported on ceria and closely related mixed oxides. Also very importantly, ceria-based gold catalysts are known to be highly active materials for CO oxida-... 

A novel preparation method was developed for the preparation of iron and gold/iron supported eatalysts using metaUic carbonyl clusters as precursors of highly dispersed nanoparticles over Ti02 and Ce02. A series of catalysts with different metal loadings were prepared and tested in the complete oxidation of methanol and the preferential oxidation of CO in the presence of H2 (PROX) as model reactions. The characterization by BET, XRD, TEM, H2-TPR, ICP-AES and XPS spothghts the interaction between Au and Fe and their influence on the catalytic activity. 

Three series of Au nanoparticles on oxidic iron catalysts were prepared by coprecipitation, characterized by Au Mossbauer spectroscopy, and tested for their catalytic activity in the room-temperature oxidation of CO. Evidence was found that the most active catalyst comprises a combination of a noncrys-taUine and possibly hydrated gold oxyhydroxide, AUOOH XH2O, and poorly crystalhzed ferrihydrate, FeH0g-4H20 [421]. This work represents the first study to positively identify gold oxyhydroxide as an active phase for CO oxidation. Later, it was confirmed that the activity in CO2 production is related with the presence of-OH species on the support [422]. 

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