C3H8 oxidation

Table 7. Selected reactions of a C3H8 oxidation mechanism...

TABLE C7 Selected Reactions of a C3H8 Oxidation Mechanism 1... 

In the case of the long term test in the presence of 14% of H2O in the feed, the catalyst lost its activity completely after 25 h on stream, but when H2O was eliminated from the feed, the catalyst slowly recovered about 30% of its initial activity for NO reduction. The loss of activity measured against a standard dry feed was 66% for NO reduction and 80% for C3H8 oxidation. This catalyst was referred as 2.3-Cu-ZSM-5AV. We have found that by decreasing the amount of H2O in the feed non-zero pseudo-steady state conversion could be reached. 

Nitadori et al. (1988) found that the catalytic activity for C3H8 oxidation over Rj xSrxCo03 increased several times upon Sr substitution for R, regardless of the kind of trivalent rare-earth ion. As for the extent of the substitution, a maximum was observed at... 

As indicated previously, propane is frequently used to model the behaviour of the hydrocarbon mixture of exliaust gas. With this hydrocarbon, the oxidation of CO occurs at about the same temperature (176°C, Fig. 7-a) as without hydrocarbon. Propane is oxidised at 268°C, and NO conversion curve shows two waves corresponding to CO and C3H8 oxidation. Using propene instead of propane would slightly increase CO light-off (190°C) and slightly decrease HC liglit-off(241°C). 

Sonentie S, Lizarraga L, Papaioannou El, Vayenas CG, Vemonx P (2010) Permanent electrochemical pnnnotirai of C3H8 oxidation over thin sputtered Pt films. Electrochem Commun 12 1133-1135... 

Song X, Williams WR, Schmidt LD, Aris R Ignition and extinction of homogeneous-heterogeneous combustion CH4 and C3H8 oxidation on Pt, Proc Combust Inst 23 1129-1137, 1990. 

Another, and simpler, manifestation of rule Gl coming from the classical promotion literature is shown in Fig. 6.13. The rate of the oxidative dehydrogenation of C3H8 to C3H6 is first order in propane and near zero order in 02.84 As expected from rule Gl the reaction exhibits electrophobic behaviour. 

Figure 10.1. Light-off curves for the reaction of the standard mixtures (.R = 0.98, 5000 ppm H20) over Rh/Al203. (a) Conversions of CO, NO, C3H6 and C3H8 (b) production of N20 and NH3 (reproduced with permission from Ref. [21]). Reactions involved over three-way catalysts are oxidation, (1) CO + 7202 C02 (2) C Hy + (x + y/4) 02 -> xC02 + y/2H20, and reduction,...

In the presence of propane (C3H8), the reaction mechanism is initiated by hydrogen abstraction from C3H8 by OH radicals, producing alkyl radicals, which then rapidly react with 02 to form peroxy radicals [88], The peroxy radicals react with NO and oxidize it to N02 ... 

Fig. 42. Catalyst screening for the oxidative dehydrogenation of propane to propene. T = 823 K molar ratios C3H8/02/N2/H20 = 5/25/25/45 GHSV = 1300 h-1 mcat = 1.4 - 8.0 g vcat = 5 ml [from Schuster et al. (259)].

Because hydrocarbon radicals of higher order than ethyl are unstable, the initial radical C H2 +1 usually splits off CH3 and forms the next lower-order olefinic compound, as shown. With hydrocarbons of higher order than C3H8, there is fission into an olefinic compound and a lower-order radical. Alternatively, the radical splits off CH3. The formaldehyde that forms in the oxidation of the fuel and of the radicals is rapidly attacked in flames by O, H, and OH, so that formaldehyde is usually found only as a trace in flames. 

Figure 1. Kinetics of the formation of different products during propane oxidation at 430°C. Propane concentration = 30%. Mixture 90 mm. C3H8 and 210 mm. 02...

Write the main elementary reactions in the low-temperature oxidation mechanism for propane (C3H8), based on the general outline for higher hydrocarbons. 

A chemical equation for the combustion of propane, C3H8, is shown below. Through this reaction is the carbon oxidized or reduced ... 

The relative rate of reaction of Of1/)) with N20 and C3H8 exceeds 0 2,352a so that under these conditions less than 20% of any Of1/)) will react with propane rather than with nitrous oxide. Our preliminary results110 indicate that the 02 quantum yield is less than 0.02%. 

Bruckner and Kondratenko (2006) used a similar approach to characterize VOx/Ti02 catalysts. In a separate TPR experiment carried out with a quartz reactor equipped with a UV-vis fiber optical probe, the relationship between the "absorbance" at 800 nm and the degree of reduction as determined from H2 consumption via mass spectrometry was established. The absorbance at 800 nm increased with increasing reduction of the vanadium, but not linearly. During the catalytic reaction experiment, the absorbance at 800 nm was then used to determine the average valence of vanadium. Because contributions of reduced titanium species in the analyzed spectral range could not be excluded, only a lower limit of the vanadium oxidation state could be determined, which was 4.86 at 523 K and C3H8/02 = 1 1. 

Mo-V-Te and Mo-V-Te-Nb mixed-metal oxide catalysts have been characterized by means of C3H8-TPR and NH3 adsorption calorimetry. All samples were strongly heterogeneous, with initial adsorption heats of = 100-80 kJ moT for the Mo-V-Te samples. Introducing an Nb component into the catalysts slightly decreased the initial adsorption heats to = 60 kJ moT but drastically increased the surface density of weak acid sites (<30kJ moT ) [83]. 

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