Platinum-titanium dioxide catalysts

That products of intermediate oxidation level can be detected in the photocatalytic reactions of hydrocarbons and fossil fuels is also consistent with a surface bound radical intermediate . Photocatalytic isotope exchange between cyclopentane and deuterium on bifunctional platinum/titanium dioxide catalysts indicates the importance of weakly adsorbed pentane at oxide sites. The platinum serves to attract free electrons, decreasing the efficiency of electron-hole recombination, and to regenerate the surface oxide after exchange. Much better control of the exchange is afforded with photoelectrochemical than thermal catalysis > ) As before, hydrocarbon oxidations can also be conducted at the gas-solid interface... 

Aromatic hydrocarbons can be oxidatively cleaved either on a side chain or in the ring (Eq. 6) [60]. Even saturated hydrocarbons can be induced to become oxygenated or to participate in isotope exchange on irradiated platinum/ titanium dioxide catalysts [151, 155, 156]. Competitive trapping of the photogenerated conduction band electron by adsorbed protons is thought to be responsible for the reduced contribution of oxygen at lower pH. 

P. Pichat, J.-M. Herrmann, J. Disdier, H. Courbon, and M.-N. Mozzanega, Photocatalytic hydrogen production from aliphatic alcohols over a bifimetion-al platinum on titanium dioxide catalyst, Nouveau Journal de Chimie, vol. 5,... 

B. Kraeutler, A.J. Bard, Heterogeneous photocatalytic preparation of supported catalysts. Photodeposition of platinum on titanium dioxide powder and other substrates, /. Am. Chem. Soc. 100 (1978) 4317-4318. 

Cao et. al. also examined titanium dioxide photocatalysts doped with 0.5% platinum. These doped catalysts displayed complete activity recovery following thermal regeneration at 350°C. Presumably, the addition of platinum, which may act as a thermal oxidation catalyst, allows for the destruction of accumulated intermediates generated during the photocatalytic oxidation at lower temperatures than untreated titanium dioxide. 

It has recently been recognized that crystal structure and particle size can also influence photoelectrochemical activity. For example, titanium dioxide crystals exist in the anatase phase in samples which have been calcined at temperatures below 500 °C, as rutile at calcination temperatures above 600 °C, and as a mixture of the two phases at intermediate temperature ranges. When a range of such samples were examined for photocatalytic oxidation of 2-propanol and reduction of silver sulfate, anatase samples were found to be active for both systems, with increased efficiency observed with crystal growth. The activity for alcohol oxidation, but not silver ion reduction, was observed when the catalyst was partially covered with platinum black. On rutile, comparable activity was observed for Ag, but the activity towards alcohol oxidation was negligibly small . Photoinduced activity could also be correlated with particle size. 

The work presented in this paper is the first part of a project aiming at the development of tailor-made oxidation catalysts for diesel engines fuelled by alcohol fuels, ethanol or methanol. The investigation is focused on the influence of support material on the low temperature oxidation of ethanol and acetaldehyde. The study presents results from an experimental investigation with precious metal catalysts applied on monolithic cordierite substrates. Platinum or palladium were applied onto a support consisting of either aluminum oxide, cerium dioxide, silicon dioxide or titanium dioxide. 

Illustrated in Figure 3.13, under operation a high-pressure mercury lamp was used to irradiate the photo-sensitive titanium dioxide thin film in the reactor, loaded with platinum catalyst. Conversion of the feedstock at 87% was achieved in 52 seconds. 

Because of the possibility of racemization during the transesterification reaction (strong basic conditions) alternative methods are reported. These include transesterification in the presence of the KF/18-crown-6 ether 461 or the use of titanium tetraalkoxides. 471 The methods are efficient and represent a route to any required dialkyl ester using diphenyl esters as starting materials. Diphenyl groups can also be removed by hydrogenation in the presence of platinum dioxide (Adams catalyst) to provide the free phosphonic acid moiety directly)46 ... 

Use Hardener for platinum and palladinum in jewelry, electrical contact alloys, catalyst, medical instruments, corrosion-resistant alloys, electrodeposited coatings, nitrogen-fixing agent (experimental), solar cells (experimental) the oxide is used to coat titanium anodes in electrolytic production of chloride the dioxide serves as an oxidizer in photolysis of hydrogen sulfide. 

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