Alkanes combustion reactions

The saturated hydrocarbons are relatively inert except at high temperatures. For example, sodium metal is usually stored immersed in an alkane such as kerosene (8 to 14 carbon atoms) to protect it from reaction with water or oxygen. Combustion is almost the only important chemical reaction of the alkanes. That reaction, however, makes the hydrocarbons one of the most important energy sources of our modern technology. 

Alkanes burn in a plentiful supply (excess) of air or oxygen to form carbon dioxide and water. Because such combustion reactions are exothermic, alkanes are very useful as fuels. 

In this section, you will learn how to predict the reactions of different functional groups. You studied the most common reaction of alkanes, combustion, in your previous chemistry course. For this reason, the reactions of alkanes will not be considered here. The reactions of amines and ethers will be left for a later chemistry course. 

Alkanes undergo combustion reaction with oxygen at high temperatures to produce carbon dioxide and water. This is why alkanes are good fuels. Oxidation of saturated hydrocarbons is the basis for their use as energy sources for heat, e.g. natural gas, liquefied petroleum gas (LPG) and fuel oil, and for power, e.g. gasoline, diesel fuel and aviation fuel. 

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 ... 

More than 140 different alkenes have been identified in the atmosphere [27]. The sources of alkenes are similar to those for the alkanes with combustion of fossil fuel being a major source. The presence of unsaturated bonds makes these compounds much more reactive than the alkanes. The most persistent member of this class of compounds (ethene) has an atmospheric lifetime of the order of a day, while more typically the lifetimes for alkenes are measured in hours. As a result of their short lifetimes the atmospheric concentrations of alkenes are highly variable and decrease dramatically away from their source locations. The mechanisms of atmospheric oxidation of alkenes have recently been reviewed [55]. As with the alkanes the reaction of OH radicals is an important loss mechanism. This reaction proceeds mainly via addition to the unsaturated bond as illustrated for ethene in Fig. 4. In one atmosphere of air at 298 K the dominant atmospheric fate of the alkoxy radical HOCH2CH2O is decomposition via C - C bond scission, while reaction with O2 makes a 20% contribution [56]. The fate of alkoxy radicals resulting from addition of OH to alkenes is generally decomposition via C - C bond scission [8]. Thus, the OH radical initiated oxidation of propene gives acetaldehyde and HCHO, oxida-... 

Alkanes produce CO2 and H2O when they are burnt. In these reactions, a large amount of energy is released. For this reason, natural gas, which contains a mixture alkanes, is a useful fuel. The general formula for a combustion reaction is ... 

At a sufficiently high temperature alkanes do react vigorously and exothermically with oxygen, and these combustion reactions are the basis for their widespread use as fuels. For example, the reaction of butane with oxygen is... 

The chapter tries to give an up-to-date account of all the main mathematical tools which have been used for the construction, investigation and reduction of complex reaction mechanisms. However, there are reviews which discuss some of these methods in more detail. Frenklach [9] has reviewed several techniques, developed until 1989, for the reduction of combustion mechanisms. Application of reduced chemical mechanisms in turbulent combustion has been reviewed by Seshadri and Williams [10]. Warnatz [4] has reviewed the relation of combustion modelling to detailed reaction mechanisms. The recent review of Griffiths [11] concentrates mainly on global mechanisms for the description of low-temperature alkane combustion. The review of Turanyi [12] gives an almost full account until... 

The most extreme oxidation reactions of organic compounds occur when they hum in O2. Such combustion reactions (Section 6-8) are highly exothermic. When the combustion takes place in excess O2, the products are CO2 and H2O. Examples of alkane combustions are... 

Hydrocarbons (HCs) from C2 to CIO are commonly used to test activity. The efficiency of the HC in the SCR of NOx in competition with the combustion reaction with oxygen increases with increasing molecular weight. This is probably due to the parallel increase in the heat of adsorption and decrease in the C-H bond strength.132 Alkanes, alkenes and oxygenated HCs have been studied in this reaction and the activity in the NOx elimination frequently follows this order, with the lower light-off temperatures being displayed for the latter type of compounds. Independent of the nature of... 

Alkanes are colorless, water-insoluble compounds the simplest of which have rather low boiling points and are commonly used as fuels. In combustion reactions the products are CO2 and H2O along with some CO if the amount of oxygen is insufficient. The reaction of alkanes with halogens can be controlled, resulting in the substitution of a halogen for a hydrogen without disruption of the carbon skeleton. 

Alkanes are generally not considered to be very reactive substances. However, under suitable conditions they do react. For example, natural gas, gasoline, and fuel oil are alkanes that undergo highly exothermic combustion reactions ... 

The following examples show a combustion reaction for a simple alkane and a simple cycloalkane ... 

Alkanes can participate in combustion reactions. In complete combustion reactions they are oxidized to produce carbon dioxide, water, and heat energy. They can also undergo halogenation reactions to produce alkyl halides. 

What is a combustion reaction How have we made use of the combustion reactions of alkanes ... 

The combustion reaction described above is complete combustion. When there is insufficient oxygen or combustion conditions (temperature, good mixing of alkane and oxygen) are not optimized, incomplete combustion occurs with the formation of varying amounts of carbon monoxide (CO) instead of carbon dioxide. This is detrimental in two ways—the amount of heat generated per mole of alkane is less and carbon monoxide is highly toxic. 

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