Platinum, additive

In these experiments, synthetic zeolites of the faujasite-type without binding substance were used. Calcium and nickel-calcium samples in ionic form were obtained by ion exchange under conditions ensuring stability of the crystal structure (5). Platinum addition was carried out by ion exchange with Pt(NH3)6Cl4 (6). 

The platinum additive studied was Platinum Plus 3100, supplied by Clean Diesel Technologies, Inc. The copper additive was OS9640K a gift from Lubrizol. The cerium additive was DPX9 from Rhodia, and the iron additive was ferrocene from Aldrich. 

Tlie effect of platinum on the trap and in the fuel, in absence of any other additive, is significant. The minimum temperature is approximately 75 K lower as a result of the platinum. If the platinum additive is used in combination with an untreated EX80 filter the balance point decreases from an initial 750 K to 675 K after several days, provided that the temperature in the filter has been occasionally high, for example during regenerations. If the temperature in the filter was kept low, the filter was less active. 

Similar effects were observed when a platinum additive was used in combination with a base metal additive. Platinum collected on the filter enhances the activity of the system after a high-temperature treatment. 

All combinations of platinum with other additives lead lo a decreased balance point temperature. The largest effect of platinum in the fuel and on the filter is observed when it is used in combination with a cerium additive. The minimum temperature is lowered with a total of 160 K. Copper and iron are more active as an individual additive, whereas the minimum temperature is higher when these additives are used, instead of cerium, in combination with the platinum additive and filter. The lowest additive concentration studied with this equipment was platinum/cerium 0.5/5 ppni/ppm. Field tests showed that the platinum concentration can be reduced to 0.25 ppm. A typical back pressure of the system at balance temperature is around 80 mbar. 

Platinum in the soot does not influence the oxidation of soot. It is very effective when present as large (l(X) nm and larger) particles on the filter. The platinum additive may be necessary to maintain substantial activity on the filter. 

Platinum present in the soot does not influence the oxidation rate of soot, either in presence or absence of NO. The influence of the platinum additive on the engine-out emissions cannot be neglected and platinum may contribute to the soot oxidation on other places than on the filter, such as the exhaust manifold and in the exhaust pipes. 

In engine experiments, the effect of platinum addition to either copper or iron additives is limited to a decrease in balance point of approximately 50 K (estimated), whereas this decrease is more than 100 K when platinum is used in combination with cerium. In total, the addition of platinum and cerium to the fuel results to a balance point that is 155 K lower than with untreated fuel. 

In this paper we present results about activity, selectivity and the amount and nature of coke which is produced during n-hexane isomerization over PtAVZ prepared using two different platinum precursors and subjected to different calcination temperatures after platinum addition. We also discuss about the importance of operational conditions and platinum loading on the catalyst in the amount and nature of the coke. 

Table 1 presents the n-hexane conversion, selectivity to isomers and coke deposited after reaction for catalysts prepared by using two different platinum precursors tetraammine platinum nitrate and hexachloroplatinic acid. Both materials were calcined at different temperatures after platinum addition. For both platinum precursors, run under standard operational conditions, the optimum calcination temperature for catalytic activity was 500 °C. The amount of coke is small and the TPO profiles of the coked samples (not shown) are similar for all catalysts. Coke is completely burnt off at temperatures below that at which the catalyst was calcined after the metal addition. This is an important feature, because regeneration procedures would not affect the metal function. 

J. A. Haynes, Y. Zhang, W. Y. Lee, B. A. Pint, I. G. Wright, and K. M., Cooley, Effects of platinum additions and sulfur impurities on the microstructure and scale adhesion behavior of single-phase CVD aluminide bond coatings. In Elevated Temperature Coatings, eds. J. M. Hampikian and N. B. Dahotre, Warrendale, PA, TMS, 1999, p. 51. 

Copland, E. (2005) Thermodynamic Effect of Platinum Additions to -NiAl An Initial Investigation, NASA/CR-2005-21330. Cleveland, OH NASA. 

The chemistry of silicones is summarized by following the steps necessary to produce a two-part, platinum-cured silicone containing vinyl-stopped polydimethylsiloxane, Si-H-on-chain siloxane, platinum catalyst and catalyst inhibitor. The process begins with silicon dioxide and follows the steps of conversion to sand to elemental silicon. Silicon is reacted with MeCl to make methylchlorosilanes in the methylchlorosilane reaction (MCS). The products from the MCS reaction are separated by distillation and then hydrolyzed and condensed to make the various siloxane polymers. Polymers with methyl, vinyl or Si-H functionality are made as required for the platinum addition-cured silicone product. 

It was pointed out in section 4 of chapter IV that the definition of a rate-determining step for the total process of methanol oxidation is meaningful only if there is only one oxidation product. The results in Table 5 and 6 demonstrate clearly that there is more than one oxidation product on platinized platinum. Additional experimental evidence is required before the different rate-determining steps of the net reactions of the path involving CH2O and HCOOH as intermediate products can be elucidated. It is not certain how much the efficiency for CO2 production on smooth platinum differs from that on platinized platinum under equivalent conditions. However, the similarity of the shape of i — U curves measured by cyclic voltammetry on smooth or platinized platinum in the same solution and at the same sweep rate, indicates that the situation is not too different. An experimental determination of the efficiency of CO2 production on smooth platinum under steady-state conditions could be made by analyzing the CO2 content of the stirring gas by mass spectrometry. 

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