Pentane combustion

Undesirable combustible gases and vapors can be destroyed by heating to the autoignition temperature in the presence of sufficient oxygen to ensure complete oxidation to CO2 and H2O. Gas incinerators are appHed to streams that are high energy, eg, pentane, or are too dilute to support combustion by themselves. The gas composition is limited typicaUy to 25% or less of the lower explosive limit. Gases that are sufficiendy concentrated to support... 

Octane number is a measure of a fuel s abiUty to avoid knocking. The octane number of a gasoline is deterrnined in a special single-cylinder engine where various combustion conditions can be controlled. The test engine is adjusted to give trace knock from the fuel to be rated. Various mixtures of isooctane (2,2,4-trimethyl pentane) and normal heptane are then used to find the ratio of the two reference fuels that produce the same intensity of knock as that by the unknown fuel. 

The combustible gas indicator must be cahbrated using the appropriate cahbratinggas, such as methane or pentane. 

Flame combustion calorimetry in oxygen is used to measure the enthalpies of combustion of gases and volatile liquids at constant pressure [54,90]. Some highly volatile liquids (e.g., n-pentane [91]) have also been successfully studied by static-bomb combustion calorimetry. In general, however, the latter technique is much more difficult to apply to these substances than flame combustion calorimetry. In bomb combustion calorimetry, the sample is burned in the liquid state and must be enclosed in a container prior to combustion. Encapsulation may be difficult, because it is necessary to minimize the amount of vaporized compound inside the container as much as possible. In addition, volatile liquids tend to burn violently under a pressure of 3.04 MPa of oxygen, which leads to incomplete combustion. These problems are avoided in flame combustion calorimetry, where the sample is carried to the combustion zone as a vapor and burned under controlled conditions at atmospheric pressure. 

Chemical/Physical. Complete combustion in air yields carbon dioxide and water. Pentane will not hydrolyze because it does not contain a hydrolyzable functional group. 

Reid vapor pressure is measured at 100°F (37.8°C) and is used to help ensure that gasoline will vaporize adequately and ignite within the combustion chamber of an engine. Vapor pressure is provided by volatile gasoline components such as dissolved butane gas and the presence of pentanes, hexanes, heptanes, and benzene. 

The gaseous oxidation of n-alkanes can, in suitable circumstances, yield substantial amounts of O-heterocycles of the same carbon number as the initial hydrocarbon. A comparative study has been carried out of the formation of O-heterocyclic products during the combustion of n-butane, n-pentane, and n-hexane. The way in which the yields of such compounds vary with reaction conditions has been investigated. As a result of the optimization of the amounts of O-heterocycles it has been possible to obtain maximum yields of these compounds of up to 30% from n-pentane but only about 10% from n-butane and n-hexane. An attempt is made to account for the observed differences in the amounts and nature of the O-heterocyclic products formed from the three n-alkanes. 

In the present work, therefore, a comparative study of the production of O-heterocycles during the cool-flame combustion of three consecutive n-alkanes—viz., n-butane, n-pentane, and n-hexane—was carried out under a wide range of reaction conditions in a static system. The importance of carbon chain length, mixture composition, pressure, temperature, and time of reaction was assessed. In addition, the optimum conditions for the formation of O-heterocycles and the maximum yields of these products were determined. The results are discussed in the light of currently accepted oxidation mechanisms. 

Barusch and Payne (6), in 1951, were successful in stabilizing a cool flame in a straight tube, and used this device to investigate the relationship between the octane number of the fuel and its tendency to form cool flames. Using a similar device Ober-dorfer (30), working in the author s laboratory was able to study the cool flames of the isomeric hexanes. In this manner, n-hexane, 2-methyl pentane, 3-methylpentane, and 2,2-dimethylbutane were readily brought to cool-flame combustion. The fuel-air ratio... 

Formaldehyde, acetaldehyde, acetone, and carbon monoxide were common combustion products of the four hexanes. Propionaldehyde, n-butyraldehyde, acrylic aldehyde, crotonic aldehyde, and methyl ethyl ketone were all found as intermediates in the combustion of n-hcxane. Acetaldehyde and acetone were prominent and propionaldehyde and acrylic aldehyde were present among the intermediates from 2-methylpentane. Acetaldehyde and methyl ethyl ketone were peculiarly characteristic of 3-methyl-pentane and acetaldehyde, acetone, and pivalic aldehyde were characteristic of 2,2-dimethylbutane. In other words, the intermediate monocarbonyl combustion products... 

Demonstrate combustion of some alkanes. Use a Bunsen burner to show complete and incomplete combustion of methane. Burn a range of alkanes to show the variation in ease of ignition - pentane and hexane are highly flammable but liquid paraffin and paraffin wax need pre-heating and/or a wick. 

Two factors that influence the heats of combustion of alkanes are, in order of decreasing importance, (1) the number of carbon atoms and (2) the extent of chain branching. Pentane, isopentane, and neopentane are all C5H12 hexane is C6H14. Hexane has the largest heat of combustion. Branching leads to a lower heat of combustion neopentane is the most branched and has the lowest heat of combustion. 

Following an experiment the reactor was unloaded and the catalyst was extracted using toluene first and then pentane. The coke content of the thus extracted catalyst was determined using Combustion Mass spectrometric Element analysis (CME). Since the total catalyst charge of the reactor was mixed at the end of an experiment, the coke data thus obtained are average data over the reactor. In other words, no coke profiles have been established by experiments. The amount of coke deposited is reported on the basis of the catalyst mass (fresh oxidic catalyst basis, the total amount of feed processed (percent weight on feed, %wof),... 

Measurements have also been made of the speed of the uniform movement in mixtures of air with each one of the hydrocarbons of the paraffin series up to and including pentane. The determinations were carried out with horizontal glass tubes, 2-5 cm. in diameter,1 and the results are shown diagrammatically in fig. 26. With the exception of methane, the maximum speeds are approximately the same, namely, about 82 cm. per second. The value for methane is rather lower than this, being 67 cm. per second. Owing to the few data available for the thermal constants of the paraffin hydrocarbons, it is not easy to explain this difference. In each instance, the mixture having the maximum speed of flame contains more combustible gas than is required for complete combustion. 

Copy the following skeleton equation for the combustion of pentane, C5H12, into your notebook and balance it. 

We know that the ethane-pentane mixture is 5 moles. If we say that the number of moles of C2Hg is x, the number of moles of CgHj2 will be (5-x) moles. Equations for the combustion of ethane and pentane are ... 

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