Heating catalytic

F. W. Kaiser and co-workers, Optim tion of an Electrically-Heated Catalytic Converter System—Calculations and Application, SAE 930384, Society of Automotive Engineers, Warrendale, Pa., 1993. 

Flammable atmospheres can be assessed using portable gas chromatographs or, for selected compounds, by colour indicator tubes. More commonly, use is made of explos-imeters fitted with Pellistors (e.g. platinum wire encased in beads of refractory material). The beads are arranged in a Wheatstone bridge circuit. The flammable gas is oxidized on the heated catalytic element, causing the electrical resistance to alter relative to the reference. Instruments are calibrated for specific compounds in terms of 0—100% of their lower flammable limit. Recalibration or application of correction factors is required for different gases. Points to consider are listed in Table 9.10. 

Tamman (29) observed in 1920 that for electrically heated catalytic wire multiple steady states occur for a certain value of electrical current. Similar experimental observations were done by Buben (31) and Davies (30) and recently by Rader (35), Barelko (36), and Cardoso and Luss (33). The Luss results involving oxidation of butane and carbon monoxide on a platinum wire will be discussed in detail. 

Kusakabe, K., Miyagawa, D., Gu, Y., Maeda, H., Morooka, S., Development of a self-heating catalytic microreactor, in Matlosz, M., Ehrfeld, W., Baselt, J. P. (Eds.), Microreaction Technology -IMRET 5 Proc. of the 5th International Conference on Microreaction Technology, Springer-Verlag, Berlin, 2001, 70-77. 

The operation of a catalytic sensor depends on the oxidation of the flammable gas on the detector which is an electrically heated catalytic filament. This detector is usually made of fine platinum wire that is coated with one of several alternative substances—palladium/platinum/thoria catalysts. These catalysts help to enhance the catalytic activity and prolong the life of the detector by enabling it to operate at lower temperatures. The detector filament is connected to an identical, but inactive, unit in a Wheatstone bridge, and is located adjacent to the active detector. The identical inactive unit allows for ambient temperature compensation. 

P Markatou, L D Pfefferle and M D Smooke, A computational study of methane-air combustion over heated catalytic and non-catalytic surfaces. Comb Flame 93 185 (1993)... 

In an effort to stop air pollution during the warm-up period, some catalytic converters heat up to 400°C within 5 seconds. The result is that almost as soon as the car is started, air pollutants in the exhaust are broken down. Heated catalytic converters are proving to be highly efficient. 

Electric power steering -b -b -b Electrically heated catalytic converter -b -b -b... 

An unusual new technique for the synthesis of alkyl iodides from chlorides or bromides involves passing the latter in the gas phase over a heated catalytic column of a solid support (silica gel), KI, and a PT catalyst (phosphonium salt) that can be free or immobilized on the silica matrix." The eluate vapours contain the product iodide. 

Hydrogen sulfide, n-butyl mercaptan, and chlorine gas all exerted permanent poisoning effects on the catalyst, as shown in Table III, Hydrogen sulfide reacted rapidly and quantitatively with the catalyst, liberating water vapor and large quantities of heat. Catalytic activity in this case was decreased by a factor of 24, rendering the catalyst completely useless. 

After treatment, the gas contains mg of dust per dry Nm of gas. It is ready for drying, heating, catalytic SO2 oxidation, and H2S04( ) making. 

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