Combustion propane

As an example that uses structural formulas and Equation, consider the energy change that takes place during the combustion reaction of propane (C3 Hg). Recall from Chapter 3 that combustion is a reaction with molecular oxygen. The products of propane combustion are carbon dioxide and water ... 

On the contrary, for propane combustion on Pd/AljOj modified by ceria addition, Shyu and co-workers observed that ceria allows to maintain Pd in a more stable oxidised state less prompt to react with propane [78], Catalytic oxidation which occurred from 200°C to 350°C is now delayed to higher temperature by 50°C to 100°C from 250°C to 450°C. More dramatically is the decrease of the conversion at 350°C from 100% to 20% as the partial pressure of oxygen increases beyond the stoichiometric ratio up to 8 times. They concluded from their studies that ceria and palladium are in close interaction, may be in a Pd-O-O-Ce-0 model via a O2 species. 

Two methods are commonly used to choose reference states for enthalpy calculations and to calculate specific enthalpies and AW. We outline the two approaches below, using a propane combustion process to illustrate them. For simplicity, the material balance calculations for the illustrative process have been performed and the results incorporated into the flowchart. 

The results show that the principal reaction in propane oxidation by air on these samples is reaction (1) and the other reactions occur only partially. The best selectivity is obtained on the catalyst prepared by 6-step imregnation in the least concentrated NP -solution. From these results, it can be concluded that on this sample, in a rather small extent, all mentioned reactions occur propane combustion (2), propane cracking (3) and water-gas shift (4). On this catalyst sample reactions (2) and (4) were more favoured than reaction (3), which occurs at temperatures below 900°C only. 

Pd/Si02 Pd/A1203 Pd/SBA-15 Inconel (NiCrFe) Methane/propane combustion Yuranov et al. [64]... 

Aqueous solutions of calcium acetate and diammonium hydrogenphosphate were used together with nitric acid and ethanol to provide additional energy to the flame required for chemical reaction. The precursor solution was injected via an atomisation device into the propane combustion pilot flame. The atomised reactive solution produced a second flame, called main flame, owing to the combustion of the ethanol-containing solution. The energy of the main flame provides the energy required for the chemical reaction, that is dissociation of... 

FIGURE 5.23, an enthalpy diagram for Equation 5.29, shows our propane combustion reaction broken down to the three reactions. Several aspects of this calculation depend on the guidelines we discussed in Section 5.4. 

Figure 10.10a shows propane conversion contours obtained from 2D CFD calculations for catalytic propane combustion in a non-adiabatic microchannel for the conditions mentioned in the caption [23]. Unlike the homogeneous combustion case, the preheating and combustion zones in catalytic microburners overlap since catalytic reactions can occur on the hot catalyst surface close to the reactor entrance. Figure 10.10b shows a discontinuity in the Nu profile, similar to the homogeneous combustion problem. In this case, it happens at the boundary between the preheat-ing/combustion zone and the post-combustion zone. At this point, the bulk gas temperature (cup-mixing average) and wall temperatures cross over and the direction... 

Kotsionopoulos N, Bebelis S (2007) In situ electrochemical modification of catalytic activity for propane combustion of Pt/P"-Al203 catalyst-electrodes. Top Catal 44 379-389... 

Kiwi-Minsker et al. prepared platinum and palladium catalysts from commercial aluminoborosilicate glass fibres [354]. The glass fibres were partially modified with titania, zirconia and alumina to increase their thermostability. The noble metal content of the fibres was very low, between 0.1 and 0.3 wt.%. The platinum samples were more active than the palladium catalysts and titania and zirconia modification of the glass increased its activity for propane combustion. Light-off occurred at 200 °C, 50% conversion was achieved at 280 °C but full conversion was not achieved even by 450 °C, owing to the inhibition effects discussed above for a sample containing... 

Yazawa, Y, Yoshida, H., Komai, S.-l. and Hattori, T. (2002) The additive effect on propane combustion over platinum catalysts. Control of oxidation-resistance... 

Yoshida, H., Yazawa, Y. and Hattori, T. (2003) Effects of support and additive on oxidation state and activity of Pt catalyst in propane combustion. Catal. Today, 87, 19-28. 

Yazawa, Y, Takagi, N., Yoshida, H., Komai, S.-l., Satsuma, A., Tanaka, T, Yoshida, S. and Hattori, T. (2002) The support effect on propane combustion over platinum catalyst control of the oxidation resistance of platinum by the add strength of support materials. Appl. Catal. A, 233, 103-112. 

Yazawa, Y, Yoshida, H., Takagi, N., et al. (1999). Acid Strength of Support Materials as a Factor Controlling Oxidation State of Palladium Catalyst for Propane Combustion, J. Catal., 187, pp. 15-23. 

Alifanti, M., Kirchnerova, J., Delmon B., et al. (2004) Methane and Propane Combustion over Lanthanum Transition-metal Perovskites Role of Oxygen Mobility, Appl. Catal. A Gen., 262, pp. 167-176. 

Returning to the previous example of propane combustion, a single-step reaction would require colhsions between six non-random molecules, which is highly unlikely and would result in a very low reaction rate in reality. 

In Chap. 7, the investigation on combustion stabihty is extended to propane-fueled catalytic microreactors, using the catalytic and gas-phase chemical reaction schemes of propane combustion on platinum proposed and validated in Chap. 4. The steady hetero-Zhomogeneous combustion of lean propaneZair and methaneZair mixtures in a platinum-coated, catalytic plane channel-flow microreactor were investigated at pressures of 1 and 5 bar, channel heights of 1.0 and 0.3 mm, and wall thermal conductivities of 2 and 16 WZmK. Stability limits were assessed as a function of fuel type, inlet velocity, and imposed external heat losses. Parametric studies were performed with a full-eUiptic, two-dimensional numerical model employing detailed gas-phase (homogeneous) reaction schemes for both fuels. 

Another benefit of developing a detailed surface reaction scheme for propane combustion on platinum would be the associated possibility of establishing a basis on which surface mechanisms for higher hydrocarbons could be developed, much like the H2/CO surface reaction descriptions were a subset for CH4 heterogeneous combustion and as CH4 can be for CgHg. 

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