Propane reaction with oxygen

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 ... 

In fact, the selective catalytic removal of NO in presence of excess oxygen remains a challenge. Most of the cunent studies involve C1-C4 hydrocarbons as reductants and zeolites as catalysts, among which Cu-exchanged MFI zeolites are considered as one of the most active [2]. The reductant shows a complex influence in this reaction it has been thus reported that a Cu/Zr02 catalysts are active with pro-pene but show low activity with propane as reductant [3]. For a practical use reduction by higher alkanes would be attractive, siiKe it would be easier to handle in a vehicle. 

Compute the enthalpy of formation of propane at 25 °C from its chemical reaction with oxygen and its ideal heat of combustion given in Table 2.3. 

The shift of curves, as shown in Fig. 3.9, is unsurprising since the larger fuel molecules and their intermediates tend to break down more readily to form radicals that initiate fast reactions. The shape of the propane curve suggests that branched chain mechanisms are possible for hydrocarbons. One can conclude that the character of the propane mechanism is different from that of the H2—02 reaction when one compares this explosion curve with the H2—02 pressure peninsula. The island in the propane-air curve drops and goes slightly to the left for higher-order paraffins for example, for hexane it occurs at 1 atm. For the reaction of propane with pure oxygen, the curve drops to about 0.5 atm. 

In addition, the infrared examination of the mechanism of propane and oxygen interaction with the sample (Fig. 6) indicates the different mechanism of interaction of the intermediate propylene as compared to other supported vanadium catalysts such as V-Ti02 (10). In particular, the formation of a 7t-bonded complex stabilized by a nearlying silanol with weak basic character due to the inductive effect of vicinal vanadium is shown. This indicates the relative inertness of the V sites in the silicalite towards 0-insertion or allylic H-abstraction on the adsorbed propylene. It is evident that the reduced reactivity of V sites in these reactions limits the consecutive reactions of intermediate propylene, thus enhancing the selectivity in the formation of this product. 

Somewhat analogous reactions would be expected for the reaction of ethylene with 02 ions but the observed reaction rate is lower than for propene, suggesting that the reaction pathway may be controlled by the C—H bond energies. For reactions of propane and 1-butene with 02, oxygenated compounds of the same carbon number as the reactants were produced. The initial step is thought to involve a hydrogen atom abstraction from a secondary carbon atom. 

The flow method has proved to be better suited to the separation of the products of the combustion in the sequence of their formation. Pease (32), working with propane and higher hydrocarbons at 1 atm. in the temperature range of 300° to 400° C., found peroxides in low concentration. Harris and Edgerton (18), using a 1 to 1 mixture of propane and oxygen at 1 atm. and in the range of 325° to 355° C., found the peroxides concentrated chiefly in the residue from the distillation of the condensed reaction products. 

Reactions with sulfur ylides proceed differently. The products are oxacyclo-propanes (oxiranes) —not alkenes. The addition step proceeds as with the phosphorus ylides, but the negatively charged oxygen of the dipolar adduct then displaces the sulfonium group as a neutral sulfide. This is an intramolecular Sn2 reaction similar to the formation of oxacyclopropanes from vicinal chloroalcohols (Section 15-11C) ... 

Propane, C3H8, is a colorless, odorless gas often used as a heating and cooking fuel in campers and rural homes. Write a balanced equation for the combustion reaction of propane with oxygen to yield carbon dioxide and water. 

The most common type of work encountered in chemical systems is the expansion work (also called pressure-volume, or PV work) done as the result of a volume change in the system. Take the reaction of propane (C3H8) with oxygen, for instance. The balanced equation says that 7 mol of product come from 6 mol of reactant ... 

How big a difference is there between AE, the heat flow at constant volume, and AEf, the heat flow at constant pressure Let s look again at the reaction of propane, C3H8, with oxygen as an example. When the reaction is carried out at constant volume, no PV work is possible and all the energy is released as heat AE = —2045 kj. When the same reaction is carried out at constant pressure, however, only 2043 kj of heat is released (AH = —2043 kj). The difference, 2 kj, occurs because at constant pressure, a small amount of expansion work is done against the atmosphere as 6 mol of gaseous reactants are converted into 7 mol of gaseous products. 

The value of the enthalpy change AH reported for a reaction is the amount of heat released or absorbed when reactants are converted to products at the same temperature and in the molar amounts represented by coefficients in the balanced equation. In the combustion reaction of propane discussed in the previous section, for instance, the reaction of 1 mol of propane gas with 5 mol of oxygen gas to give 3 mol of C02 gas and 4 mol of water vapor releases 2043 kj. The actual amount of heat released in a specific reaction, however, depends on the actual amounts of reactants. Thus, reaction of 0.5000 mol of propane with 2.500 mol of 02 releases 0.5000 X 2043 kj = 1022 kj. 

Note that the physical states of reactants and products must be specified as solid (s), liquid (0, gaseous (g), or aqueous (aq) when enthalpy changes are reported. The enthalpy change for the reaction of propane with oxygen is A H = -2043 kj if water is produced as a gas but AEf = -2219 kj if water is produced as a liquid. 

Measurements made under these conditions are indicated by addition of the superscript ° to the symbol of the quantity reported. Thus, an enthalpy change measured under standard conditions is called a standard enthalpy of reaction and is indicated by the symbol A H°. The reaction of propane with oxygen, for example, might be written... 

Figure 3.85 Reactor response to an impulse of the reactants propane and oxygen compared with the model response (right proposed reaction mechanism derived from model data) [136] (by courtesy of Elsevier Ltd.).

Alkanes contain only C-C and C-H bonds, both of which are relatively strong. For that reason, they have little tendency to undergo many kinds of reactions common to some other organic chemicals, such as acid-base reactions or low-temperature oxidation-reduction reactions. However, at elevated temperatures alkanes readily undergo oxidation — more specifically combustion — with molecular oxygen in air, as shown by the following reaction of propane ... 

Alkanes undergo a number of chemical reactions, two classes of which should be mentioned here. The first of these is oxidation with molecular oxygen in air, as shown for the following combustion reaction of propane ... 

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