Ethane combustion

The development of an ethane combustion mechanism provides a historical context for understanding some overall trends of alkyl radical combustion. An understanding of the likely pathways for this small system is useful in modeling chemistry of larger systems, as can be observed from an examination of some other reactive radical intermediates. 

The effect of the cation in the A-poshion can be more clearly seen in Fig. 5, in which the areal rates of ethane transformation as a function of x are conq)ared. The activity of the unsubstituted sanqrles was very similar, being sU tly higher for the La catalyst. By contrast, the ethane combustion rate was higher on the substituted Ndi-xKxMnOa perovskites as con ared with the homologous Lai-xKxMnOs samples with the same substitution level. This reveals that the nature of the rare-earth cation also has a significant effect in the catalytic performance, especially in the presence ofpotassiiun. 

Ethane represents one of the less investigated light hydrocarbons for total oxidation, at least comparatively to methane. Substituted Lai eSr tFe03 perovskites [36] and substituted halo- Lai eSr tFe03 5Xo. (X = F, Cl) perovskites [37] were reported to convert ethane at temperatures higher than 400 °C with a maximum in selectivity in CO2 of 60%. For both perovskites, ethene was the only by-product. Also, the substitution of La by K in Lai eK eMn03 perovskites decreased the activity for ethane combustion and allowed the formation of ethylene [38,39]. These studies also point out that the bulkier cation in the A position perovskite structure plays a role in determining the catalytic performance. 

Tetrachloroethylene can be prepared direcdy from tetrachloroethane by a high temperature chlorination or, more simply, by passing acetylene and chlorine over a catalyst at 250—400°C or by controlled combustion of the mixture without a catalyst at 600—950°C (32). Oxychl orin a tion of ethylene and ethane has displaced most of this use of acetylene. 

Oxidation of Hydrocarbons. Ethanol is one of a variety of oxygen-containing compounds produced by the oxidation of hydrocarbons. Ethanol is reported to be obtained in a yield of 51% by the slow combustion of ethane (158,159). When propane is oxidi2ed at 350°C under a pressure of 17.2 MPa (170 atm) (160,161), 8% of the oxygen is converted to ethanol. Lower conversions to ethanol are obtained by oxidi2ing butane. Other oxidation systems used to produce ethanol and acetaldehyde (162—164) and methods for separating the products have been described in the patent Hterature. 

Fired reactors contain tubes or coils in which an endothermic reaction within a stream of reac tants occurs. Examples include steam/ hydrocarbon reformers, catalvst-filled tubes in a combustion chamber pyrolyzers, coils in which alkanes (from ethane to gas oil) are cracked to olefins in both types of reac tor the temperature is maintained up to 1172 K (1650°F). 

Show a free radical reaction which results in ethane in the effluent of a combustion process burning pure methane with pure oxygen. 

One cubic foot (0.03 cu.m) of methane requires 10 cubic feet (0.28 cu.m) of air (2cu.ft (0.06 cu.m) of oxygen and 8cu.ft (0.23 cu.m) of nitrogen) for combustion. The products are carbon dioxide, nitrogen, and water. The combustion product of one cubic foot of methane yields a total of nine cubic feet of carbon dioxide gas. Also, the gas burned contains some ethane, propane, and other hydrocarbons. The yield of inert combustion gas from burning a cubic foot of methane will be 9.33 cubic feet (0.26 cu.m)... 

Consider the combustion of ethane (C H ) in pure oxygen. If 100 lb of ethane are available and 10% excess oxygen is supplied to ensure complete combustion, calculate (1) the amount of oxygen supplied, and (2) compositions of the reactants and products on mass and molal bases. 

A natural gas having the volumetric composition of 90% methane, 8% ethane, and 2% nitrogen at 1 atm and 25°C is used as fuel in a power plant. To ensure complete combustion 75% excess air is also supplied at 1 atm and 25°C. Calculate (i) the lower and higher heating values of the fuel at 25°C and (ii) the theoretical maximum temperature in the boiler assuming adiabatic operation and gaseous state for all the products. 

On complete combustion at constant pressure, a 1.00-L sample of a gaseous mixture at 0°C and 1.00 atm (STP) evolves 75.65 kj of heat If foe gas is a mixture of ethane (C2H6) and propane (C3Hg), what is foe mole fraction of ethane in foe mixture ... 

In ethane, C2H6, all of the bonds are normal single bonds. Experiment shows that ethane is a fairly unreactive substance. It reacts only when treated with quite reactive species (such as free chlorine atoms), or when it is raised to excited energy states by heat (as in combustion). Ethylene, on the other hand, reacts readily... 

Using the information given in Table 7-II, determine the reaction heat per mole of QHdg) for the complete combustion of ethane. 

Heal content, 110. 116 change (luring a reaction, 110 of a substance, 109 Heat of combustion of diamond, 122 graphite, 122 hydrazine, 47 hydrogen, 40 methane, 123 Heat of formation, 113 Heat of reaction, 135 between elements, table, 112 oxidation of HC1, 160 oxidation of sulfur dioxide, 161 predicting, 112 Heat of reaction to form ammonia, 112 Br atoms, 290 carbon dioxide, 112 carbon monoxide, 112 Cl atoms, 290 CO + Hi, 110 ethane, 112 F atoms, 290 H atoms, 274 hydrogen chloride, 160 hydrogen iodide, 112 iron(Ill) oxide, 162 Li atoms, 290 Li + Br, 290 Li + F, 290 Na + Cl, 290 NHs products, 114 Na atoms, 290 NO, 112 NOj, 112... 

Heats of combustion are very accurately known for hydrocarbons. For methane the value at 25°C is 212.8 kcal mol (890.4 kJ mol ), which leads to a heat of atomization of 398.0 kcal mol (1665 kJ mol ) or a value of for the C—H bond at 25°C of 99.5 kcal mol (416 kJ mol ). This method is fine for molecules like methane in which all the bonds are equivalent, but for more complicated molecules assumptions must be made. Thus for ethane, the heat of atomization at 25°C is 676.1 kcal mol or 2829 kJ mol (Fig. 1.11), and we must decide how much of this energy is due to the C—C bond and how much to the six C—H bonds. Any assumption must be artificial, since there is no way of actually obtaining this information, and indeed the question has no real meaning. If we make the... 

C06-0100. Use average bond energies (Table 6-2) to compare the combustion energies of ethane, ethylene, and acetylene. Calculate which of these hydrocarbons releases the most energy per gram. 

Individually, the radical-initiation reactions 6.1-6.3 are too slow and thermodynamically disfavored, dne to their significant endothermicities, to effect combustion on their own. For example, consider the initiation reactions of 6.1-6.3 with ethane (CH3-CH3) as the fnel ... 

To ensure complete combustion, 20 per cent excess air is supplied to a furnace burning natural gas. The gas composition (by volume) is methane 95 per cent, ethane 5 per cent. Calculate the mols of air required per mol of fuel. 

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