Combustion activities conditions

It is worth noting that, in order to match the combined requirements of high combustion activity and durability under harsh operating conditions, catalysts with a high Pd loading (about 10% w/w) must be adopted [16, 98]... 

Kharatyan, S. L., and Nersisyan, H. H., Combustion synthesis of silicon carbide under oxidative activation conditions. Int. J. SHS, 3,17 (1994). 

From all of the results reviewed in this section, it is clear that particle size may have an important effect on activity, but measurement of particle size alone cannot be used to predict the combustion activity. It is apparent that the structure and composition of the surface plays a decisive role in activity, and it greatly depends on the thermal history of the sample. As a result, catalysts with similar particle size may exhibit very different activities. Therefore, plots like Figures 1 and 2 are only valid when the samples have been pretreated under similar conditions. 

In conclusion, although the most active catalyst would be one that contains both PdO and Pd sites, this situation can only be achieved close to the PdO decomposition temperature, in a metastable condition, which is limited by kinetics (nucleation rate). At both extremes the combustion activity is low. Without PdO species present, metallic Pd is not active. Similarly, completely oxidized PdO would not be active unless it contained oxygen vacancies. 

It was demonstrated in this study that Cu ions highly dispersed in matrices that are not active in propene combustion, such as ZrOj and Ga203, are active catalysts for propene reduction of NO to N2 in the lean condition. For the CU-Z1O2 catalysts, it was found that increasing the Cu content resulted in catalysts that were more active in both propene combustion and NO reduction. But the increase in propene combustion activity was faster than NO reduction, thus the resulting efficiency in NO removal decreased. EPR spectra and TPR profiles showed that catalysts with higher Cu contents contained larger fraction of Cu ion in clusters. 

The temperature rise in the inlet stage is limited by taking advantage of the unique properties of palladium combustion catalysts. Under combustion conditions, palladium can be either in the form of the oxide or the metal. Palladium oxide is a highly active combustion catalyst, whereas palladium metal is much less active. Palladium oxide is formed under oxidizing conditions... 

PTFE decomposes to TFE with first-order kinetics and a 347.4-kJ/mol activation energy under vacuum pyrolysis conditions It is extremely flame resistant and does not bum in air Its limiting oxygen mdex (LOR, the muumum oxygen content of an atmosphere under ambient conditions that sustams combustion, is 96%, which means that it requires almost pure oxygen for combustion... 

Combustion of wood or paper treated with pentachlorophenol resulted in no increase and more probably a decrease in octachlorodi-benzo-p-dioxin concentrations while octachlorodibenzo-p-dioxin increased slightly in paper treated with sodium pentachlorophenate. The pho-tolytic degradation of sodium pentachlorophenate at pH 8 is very rapid. Under these controlled conditions formation of no more than 0.03% octachlorodibenzo-p-dioxin was observed. The 2,3,7,8 isomer, one of the most active chloracnegens is seemingly stable towards air oxidation but... 

In this paper, we prepared LaMnOa perovskite-type oxides using the malic acid method and investigated their physical properties. It has been also investigated the effect of partial substitution of metal iorrs into La and Mn sites and the reaction conditions on the activity for the combustion of soot particulates. 

Fig.l Surface area and catalytic activity for methane combustion of AMnAlii-Oi9methane conversion level is 10%. Reaction condition CH4,1 vol% air, 99 vol% space velocity, 48 OOOh ... 

With respect to CO oxidation an activity order similar to that described above for CH4 combustion has been obtained. A specific activity enhancement is observed for Lai Co 1-973 that has provided a 10% conversion of CO already at 393 K, 60 K below the temperature required by LalMnl-973. This behavior is in line with literature reports on CO oxidation over lanthanum metallates with perovskite structures [17] indicating LaCoOs as the most active system. As in the case of CH4 combustion, calcination at 1373 K of LalMnl has resulted in a significant decrease of the catalytic activity. Indeed the activity of LalMnl-1373 is similar to those of Mn-substituted hexaaluminates calcined at 1573 K. Dififerently from the results of CH4 combustion tests no stability problems have been evidenced under reaction conditions for LalMnl-1373 possibly due to the low temperature range of CO oxidation experiments. Similar apparent activation energies have been calculated for all the investigated systems, ranging from 13 to 15 Kcal/mole, i.e almost 10 Kcal/mole lower than those calculated for CH4 oxidation. 

---