Platinum catalytic combustion

PGM catalyst technology can also be appHed to the control of emissions from stationary internal combustion engines and gas turbines. Catalysts have been designed to treat carbon monoxide, unbumed hydrocarbons, and nitrogen oxides in the exhaust, which arise as a result of incomplete combustion. To reduce or prevent the formation of NO in the first place, catalytic combustion technology based on platinum or palladium has been developed, which is particularly suitable for appHcation in gas turbines. Environmental legislation enacted in many parts of the world has promoted, and is expected to continue to promote, the use of PGMs in these appHcations. 

The advantage is an oxidation temperature of 500°F compared to non-catalytic combustion of 1500°F. The active ingredients used were platinum, as well as the base metal oxides of cobalt, nickel, manganese, chromium, and iron. The support material included nickel-chromium ribbons, ceramics rods, beads, and pellets (13-17). 

The phenomenon under consideration was studied systematically in the beginning of the 19th century. In 1815, Davy performed experiments that dealt with catalytic combustion on platinum gauzes. The term catalysis , however, was introduced by Berzelius in 1836. He first defined a catalyst (Berzelius, 1836) as a compound, which increases the rate of a chemical reaction, but which is not consumed during the reaction. This definition was later amended by Ostwald (1853-1932) in 1895 to involve the possibility that small amounts of the catalyst are lost in the reaction or that the catalytic activity is slowly decreased A catalyst is a substance that increases the rate of approach to equilibrium of a chemical reaction without being substantially consumed in the reaction. It was more than a century after Berzelius first definition that Marcel Prettre s introduced the notion of yield The catalyst is a substance that increases the rate of a chemical transformation without modifying the yield, and that is found intact among the final products of the reaction. ... 

O. Deutschmann, L.I. Maier, U. Riedel, A.H. Stroemman, and RW. Dibble. Hydrogen Assisted Catalytic Combustion of Methane on Platinum. Catalysis Today, 59 141-150,2000. 

Tanaka et al. [73] developed another MEMS system for the catalytic combustion of butane. It is composed of a combustion chamber 8 mm wide, 14 mm long and 150 pm deep which was prepared by anisotropic wet etching of a silicon substrate. The substrate was then covered with Pyrex glass applying anodic bonding. Combustion was performed on a platinum/titania catalyst... 

The most common type of combustible gas detectors utilizes the catalytic combustion principle. A platinum wire filament (in a Wheatstone bridge cir-... 

Nitrogen(II) oxide in 80 to 90% yield is produced by the catalytic combustion of ammonia in oxygen in the presence of water vapor on a platinum-rhodium catalyst ... 

Lyubovsky, M., Smith, L.L., Castaldi, M., Karim, H., Nentwick, B., Etemad, S., LaPierre, R., and Pfefferle, W.C. Catalytic combustion over platinum group catalysts Fuel-lean versus fuel-rich operation. Catalysis Today, 2003, 83, 71. 

For other types of systems such as highly branched reaction networks for homogeneous gas-phase combustion and combined homogeneous and catalytic partial oxidation, mechanism reduction involves pruning branches and pathways of the reaction network that do not contribute significantly to the overall reaction. This pruning is done by using sensitivity analysis. See, e.g., Bui et al., "Hierarchical Reduced Models for Catalytic Combustion H Air Mixtures near Platinum Surfaces, Combustion Sci. Technol. 129(l-6) 243-275 (1997). 

This contribution describes some physical properties of reverse w/o microemulsions, physical-chemical properties of platinum catalysts prepared by classical impregnation from water solutions of HaPtCle and from reverse w/o microemulsions comprising chloroplatinic acid and their activity in combustion of volatile organic compounds (VOC). In our study we concentrated on TweenSO (polyoxlethylen(20)sorbitan monoleate), as the surfactant does not comprise any potentially harmful ions (like sodium in AOT or bromide in CTAB) that could affect the activity of platinum in catalytic combustion. 

To be more specific, we refer to some known systems obeying the nonlinear kinetic laws mentioned above one of them involves a wide variety of the reactions of catalytic combustion of carbon oxide and hydrocarbons described by models with substrate inhibition (see, for example, reference 25) another one is connected with ammonium oxidation on platinum characterized by a chain-branched multiplication of active centers. ... 

C. Bruno, P.M. Walsh, D. Santavicca, F.V. Bracco, High temperature catalytic combustion of CO-Q2-N2, Ar, He, C02-H20 mixtures over platinum, Int. J. Heat Mass Transfer 26 (1983) 1109. 

Although the process configuration varies widely there are three main steps common to each, they are oxidation of ammonia to nitric oxide (NO), oxidation of NO to nitrogen dioxide (N02), and then absorption of N02 in water to produce nitric acid (Figure 3.11). The first step of the catalytic combustion of ammonia takes place over a catalyst consisting of platinum/rhodium (90 10) or platinum/rhodium/palladium (90 5 5). The reaction is very rapid and goes almost to completion as shown in Reaction 3.11. The reaction is one of the most efficient catalytic processes in industrial chemistry, having an extremely... 

These discoveries stimulated other research workers to activity and in the following period from 1819 to 1836 considerable attention was devoted to catalytic combustion principally at low temperatures. In 1819 Dobereiner discovered the tranendous activity of spongy platinum and developed his lamp for producing fire.1 Dulong and Thenard found that other metals could be made to act in the same way as platinum and pal-... 

In conventional processes (Stamicarbon and Inventa), hydroxylamine sulfate is prepared by the Raschig technique. The first reaction is the catalytic combustion of ammonia in air at 850°C. in the presence of a platinum foam catalyst The heat generated by the reaction is recovered in a boiler which produces steam. Nitrogen oxides are formed by the following reaction mechanism ... 

A Kalantar Neyestanaki, L-E Lindfors, Catalytic Combustion over transition metal oxides and platinum metal oxides supported on knitted silica fibre, Combust. Sci. and Tech., 97 121-136, 1994. 

Reactions in the Gas Phase VOCs are major air pollutants, and catalytic combustion is one of the most important technologies for eliminating low concentrations of VOCs in effluent systems [64] Platinum metal is the most active catalyst for hydrocarbon combustion and is widely used supported on AI2O3 and other oxides. It is important for this combustion to take place at low temperatures. However, the water vapor produced during combustion under these conditions can be adsorbed on the oxide support due to its hydrophilicity, which can negatively affect the catalytic activity of the metal. This activity can also be affected by humidity in the feeding stream. Hydrophobicity of carbon materials could overcome this problem, and activated carbons have been proposed as supports in VOC combustion [65,66]. 

The objective with the present work was to study catalytic combustion and the poisoning effect of sulfur in the catalytic combustion of gasified industrial waste over palladium and platinum catalysts on different support materials. 

Maldonado-Hodar F J, Moreno-Castilla C, Perez-Cadenas A F (2004) Catalytic combustion of toluene on platinum-containing monolithic carbon aerogels. Applied Catalysis B-Environmental 54 217-224 Maldonado-Hodar F J, Perez-Cadenas A F, Moreno-Castilla C (2003) Morphology of heat-treated tungsten doped monolithic carbon aerogels. Carbon 41 1291-1299... 

However, in other cases internal diffusion limitation can be significant even with very thin washcoat thicknesses [127], when temperature is high (> 700°C). This refers, for example, to catalytic combustions, which are extremely fast. Hayes et al. [135] evaluated the extent of intraphase and interphase resistances to the catalytic conversion of low concentrations of carbon monoxide in air in a tube wall reactor (coated with a platinum-alumina deposit). Above 610 K there was strong evidence of both intraphase and interphase resistances to catalytic conversion. In Sections 8.3.2, 8.3.3, and 8.3.4, we provide a systematic analysis for prediction of the extension of external and internal diffusion limitations. 

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