Hydrolytic disproportionation of carbon (HDC) was proposed
as an essential reaction in connection with coal mine methane
formation in catastrophic events [1,2]. The calculated Gibbs free
energy change of HDC or direct reduction of hydrogen from its
oxide by coal in the form of carbon is 29.20 kJ/mol of methane
or 14.60kJ/mol of carbon. It was shown that reaction of methane
formation from carbon and water is a slightly endothermic process,
but the products entropy increases, and the reaction is productfavored.
Reaction entropy positive and this reaction could be an
“entropy driven”. There was proposed a possibility that the size
and tetrahedral structure of methane molecules, similar to the
stereochemistry of the holes of water clathrates, gives additional
features of favorable stereochemistry during the formation of
intermediate stereo-structures of hydrotated coal rings, acetic acid
like dimers and polymers and their subsequent transformation and
decomposition during HDC with the production of methane and
carbon dioxide as the final substances.
During catastrophic events reaction energy could be
compensated by the exothermic reaction of partial oxidation of
methane. Evaluation of the critical conditions of HDC shows that
under the normal pressure Gibbs free energy becomes equal to
zero under the temperatures of about 142°C. This temperature
might be considered as a critical for methane and carbon dioxide
irreversible formation under the normal pressure.
Usually temperatures near 140°C are characteristic for the
depths near 4 km [3], but various mining and geological peculiarities
could drastically change the situation. Methane formation might
be stimulated artificially, and it is done in the technologies of
underground coal gasification (UCG) and hydraulic fracking (HF).
The most successful industrial exploitation of coalbed methane
occurs primarily in coals of the Fruitland Formation [4,5]. About
2,550 wells were operating in the San Juan Basin in 2001. All
wells are vertical wells that range from about 500 to 4,000 feet in
depth and were drilled using water or water-based muds. Almost
every well has been fracture-stimulated, using either conventional
hydraulic fracturing in perforated casing or cavitation cycling in
open holes. Each fracture stimulation treatment may inject, on
average, approximately 55,000 to 300,000 gallons of stimulation
and fracturing fluid per treatment. Total gas production was 925
Bcf in 2000 [1]. Modern technologies of natural gas producing
including HF and UCG processes have a great impact to the Earth
ecology and HDC reaction might be crucial for our understanding
of the possibilities to regulate them.