Methane energy content

The chemical energy content of fossil fuels generally parallels the H/C ratio as shown in Table 1. Methane has the highest heating value of the hydrocarbon series, corresponding to its high H/C ratio while coal has the lowest heating value. The normal physical state of fossil fuels also parallels the H/C ratio. Methane is a gas at ambient temperature and pressure conditions. Petroleum fractions are mobile liquids except for the heaviest fraction which can be solid at ambient temperature. Coal is a solid material. 

In renewable energy processes, the gaseous fuels include GH2, biodegradation-generated methane, and other gases. Calorimeters are analyzers that measure the heat value or energy content of gaseous fuels. There are two... 

The energy content of the various secondary ions (from, respectively, methane, isobutane, and ammonia) decrease in the order CH5+ > f-C4H9+ > NH4+. Thus,... 

High energy content, low vapor pressure (200 psi), and liquid state at ambient temperatures favors low-cost liquid pipeline transportation vs. high-pressure compressed gas—1000+ psig if methane conversion is done near the production site. 

We are not attempting to compare the absolute energy contents of, say, methyl and ethyl radicals we are simply saying that the difference in energy between methane and methyl radicals is greater than the difference between ethane and ethyl radicals. When we compare stabilities of free radicals, it must be understood that our standard for each radical is the alkane from which it is formed. As we shall see, this is precisely the kind of stability that we are interested in. 

This resonance causes stabilization, that is, lowers the energy content. However, resonance involving Kekule structures presumably stabilizes both molecule and radical to the same extent, and hence does not affect the difference in their energy contents. If there were no other factors involved, then we might reasonably expect the bond dissociation energy for a benzylic hydrogen to be about the same as that of a methane hydrogen (see Fig. 12.1). 

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