Platinum catalysts nanoparticles

Andreaus B, Maillard F, Kocylo J, Savinova ER, Eikerling M. 2006. Kinetic modeling of CO monolayer oxidation on carbon-supported platinum catalyst nanoparticles. J Phys Chem B 110 21028-21040. 

Waszczuk P, Solla-Gull6n J, Kim HS, Tong YY, Montiel V, Aldaz A, Wieckowski A. 2001a. Methanol electrooxidation on platinum/ruthenium nanoparticle catalysts. J Catal 203 1-6. 

Bergamaski K, Pinheiro ALN, Teixeira-Neto E, Nart EC. 2006. Nanoparticle size effects on methanol electrochemical oxidation on carbon supported platinum catalysts. J Phys Chem B 110 19271-19279. 

Platinum-based nanoparticles (e.g., Pt [1-15], Pt-Re [10,15], and Pt-W [5,6,15]) supported on granular activated carbon (KOH-activation, BET specific surface area 3100 m2/g, pore volume 1.78 cm3/g, average particle size 13 pm, average pore size 2.0 nm, Kansai Netsukagaku Co. Ltd. [32]) were mainly used as the dehydrogenation catalysts in the present study. 

Time courses of dehydrogenation activities with carbon-supported platinum catalyst under superheated liquid-film conditions in laboratory-scale continuous operation. Catalyst platinum nanoparticles supported on granular activated carbon (Pt/C, 5 wt-metal%), 1.1 g. Feed rate of tetralin 0.5 mL/min (superheated liquid-film conditions). Reaction conditions boiling and refluxing by heating at 240°C and cooling at 25°C. (Reproduced from Hodoshima, Sv Shono, A., Satoh, Kv and Saito, Yv Chem. Eng. Trans8,183-188, 2005. With permission.)... 

Toshima et al. obtained colloidal dispersions of platinum by hydrogen- and photo-reduction of chloroplatinic acid in an aqueous solution in the presence of various types of surfactants such as dodecyltrimethylammonium (DTAC) and sodium dodecylsulfate (SDS) [60]. The nanoparticles produced by hydrogen reduction are bigger and more widely distributed in size than those resulting from the photo-irradiation method. Hydrogenation of vinylacetate was chosen as a catalytic reaction to test the activity of these surfactant-stabilized colloids. The reaction was performed in water under atmospheric pressure of hydrogen at 30 °C. The photo-reduced colloidal platinum catalysts proved to be best in terms of activity, a fact explained by their higher surface area as a consequence of their smaller size. 

In order to evaluate the catalytic characteristics of colloidal platinum, a comparison of the efficiency of Pt nanoparticles in the quasi-homogeneous reaction shown in Equation 3.7, with that of supported colloids of the same charge and of a conventional heterogeneous platinum catalyst was performed. The quasi-homogeneous colloidal system surpassed the conventional catalyst in turnover frequency by a factor of 3 [157], Enantioselectivity of the reaction (Equation 3.7) in the presence of polyvinyl-pyrrolidone as stabilizer has been studied by Bradley et al. [158,159], who observed that the presence of HC1 in as-prepared cinchona alkaloids modified Pt sols had a marked effect on the rate and reproducibility [158], Removal of HC1 by dialysis improved the performance of the catalysts in both rate and reproducibility. These purified colloidal catalysts can serve as reliable... 

Figure 4.7 Experimental observations of the TOF variations for supported platinum catalysts Pt/Al203 as a function of the size of cata-lytically active metal nanoparticles during the stationary occurrence of the methane deep oxidation at 430 C [1].

Qi, Z. and Pickup, P.G., Novel supported catalysts platinum and platinum oxide nanoparticles dispersed on polypyrrole/polystyrenesulfonate particles, Chem. Com-mun., 15, 1998. 

The heart of a fuel cell is the membrane electrode assembly (MEA). In the simplest form, the electrode component of the MEA would consist of a thin film containing a highly dispersed nanoparticle platinum catalyst. This catalyst layer is in good contact with the ionomeric membrane, which serves as the reactant gas separator and electrolyte in this cell. The membrane is about 25-100 p,m thick. The MEA then consists of an ionomeric membrane with thin catalyst layers bonded on each side. Porous and electrically conducting carbon paper/cloth current collectors act as gas distributors (Figure 27.1). Since ohmic losses occur within the ionomeric membrane, it is important to maximize the proton conductivity of the membrane, without sacrificing the mechanical and chemical stability. 

Vajda S, Ballentine GE, Mucherie S, Marshall CL, Elam JW, Pellin MJ, Lee B, Lo CT, Seifert S, Winans RE, Calo JM (2007) Highly selective oxidation reactions Oxidative dehydrogenation of propane (ODHP) by size-selected platinum catalysts and oxidation of alkenes on size-selected silver and gold clusters and nanoparticles. Am Chem Soc Div Petrol Chem 52... 

The reaction sequence was then extended to three steps, again with catalyst recovery, with conversion of 112 into 115 by adding the base catalyst supported on magnetic nanoparticles and the polymeric acid catalyst into the vessel along with the platinum catalyst enclosed in a membrane. The overall yield of the final product 115 was 78%. 

As discussed before the amount of platinum catalyst used in electrocatalysts of a PEM fuel cell is supported on carbon in the form of nanoparticles, in order to... 

It was found that for enantioselective hydrogenation over modified platinum catalysts the most suitable SC-solvents are ethane and propane as indicated in Table 5.15. Application of SC-CO2 in hydrogenation on chiral modified Pt-catalysts proved to be less suitable because CO2 is partly hydrogenated into CO, which poisons the catalyst But polymer-supported colloidal Pd nanoparticles as catalysts in supercritical CO2 (SCCO2) revealed top s as high as 4 x 10 h" at 15 bar hydrogen, and 50°C (Niessen et al. 

Xin et al. [10] evaluated the synthesis of catalyst nanoparticles using microemulsions like cyclohexane. In this work no pure metal were observed, only alloys of the catalyst exhibited as seen from X-ray diffraction (XRD). The composition and particle was controlled using microemulsions [11,12]. The alloy formation of platinum, which has a FCC structure, included shifting of the diffraction peak to a higher angle (20), indicating a decrease in lattice parameter. 

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