Platinum based metal catalysts supports

In practical terms this has constrained the development of only three basic control strategies (refs 9,10) in the context of stringent legislation. These are all based upon application of supported platinum group metal catalysts. The strategies are ... 

The activities of fresh, supported platinum and base metal oxidation catalysts are evaluated in vehicle tests. Two catalysts of each type were tested by the 1975 FTP in four 600-4300 cm3 catalytic converters installed on a vehicle equipped with exhaust manifold air injection. As converter size decreased, base metal conversions of HC and CO decreased monotonically. In contrast, the platinum catalysts maintained very high 1975 FTP CO conversions (> 90% ) at all converter sizes HC conversions remained constant 70% ) at volumes down to 1300 cm3. Performance of the base metal catalysts with the 4300-cm3 converter nearly equalled that of the platinum catalysts. However, platinum catalysts have a reserve activity with very high conversions attained at the smallest converter volumes, which makes them more tolerant of thermal and contaminant degradation. 

Supported platinum and base metal catalysts were evaluated in vehicle tests with converter volumes of 600-4300 cm3. The initial oxidation activity of the catalysts was determined as the vehicle was operated over the 1975 FTP. The ability of the base metal catalysts to control exhaust HC and CO emissions was strongly dependent on the catalyst volume. HC and CO conversion decreased quite rapidly as the converter size was decreased. 

The development of these catalysts occurred in an atmosphere of tight secrecy, and little has been published on those efforts. All three were of the particulate type one contained noble metal(s) while the other two were noble-metal promoted base-metal catalysts (16). The UOP noble metal catalyst was provided several years later to GM and to Ford for evaluation with unleaded fuel and for other studies, and it can be deduced that it was supported on low-density (about 0.32 g/mL apparent bulk density) 1/8 inch spheres (17) and may have contained about 0.47 troy ounces of platinum per cubic foot (ca. 0.16 weight percent), with the platinum concentrated in a subsurface shell some distance below the exterior surfaces of the spheres for improved poison resistance (18) The Cyanamid catalyst was later studied by Ford (16, 19) it apparently was an extrudate (1/8" diameter x 1/8" long) of about 0.67 g/mL ABD, with about 125 ppm (weight) of palladium and 5 weight % each of CuO and 2 5 Si02 95% AI2O3 support of about... 

Anilines have been reduced successfully over a variety of supported and unsupported metals, including palladium, platinum, rhodium, ruthenium, iridium, (54), cobalt, and nickel. Base metals require high temperatures and pressures (7d), whereas noble metals can be used under much milder conditions. Currently, preferred catalysts in both laboratory or industrial practice are rhodium at lower pressures and ruthenium at higher pressures, for both display high activity and relatively little tendency toward either coupling or hydrogenolysis,... 

While the discovery of the catalytic properties of zeolites was driven by the desire to improve industrial prcKessing, the development of emission control catalysts was necessitated by governmental fiat. The first requirement was for 90+% removal of CO and of hydrocarbons, a goal which could not be met by oxidation with base metal oxides. To achieve the required spedfications during automobile operations, it was necessary to develop supported platinum catalysts. Originally the support was alumina in pellet form. Later platinum on cordierite was used in honeycomb form, containing 200-400 square channels per square inch. 

Platinum and Palladium Based Catalysts. Researchers at ANL have also developed an ATR catalyst formulation comprised of a transition metal element supported on an oxide ion-conducting substrate, such as ceria. 

In the early 1960 s Engelhard developed and commercialized the Selectoxo catalyst and process for H2 plants. The heart of this technology is a highly selective catalyst, which oxidizes up to 10,000 ppm CO without significantly oxidizing the 70% H2 (dry) in the feed stream. CO levels were reduced to less than 5 ppm under steady state conditions (50°C, 10,000 h 1 space velocity and 200-400 psig). The Selectoxo catalyst contains 0.5% platinum (Pt) supported on y -alumina, /8 inch tablets promoted with a base metal oxide. 

The electro-catalytic oxidation of hydrogen, and reduction of oxygen, at carbon supported platinum based catalysts remain essential surface processes on which the hydrogen PEM fuel cell relies. The particle size (surface structure) and promoting component (as adsorbate or alloy phases) influence the activity and tolerance of the catalyst. The surface chemical behavior of platinum for hydrogen, oxygen, and CO adsorption is considered, in particular with respect to the influence of metal adsorbate and alloy components on close packed and stepped (defect) platinum surfaces. Dynamical measurements (employing supersonic molecular beams) of the... 

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