In
order to further understand the mechanism of coal self-heating
in the initial stage, the aldehyde group was analyzed by using the
quantum chemistry methods. The charge distribution, structural parameters,
and molecular orbital were analyzed to determine the active sites
existing in the structure of aldehyde group. Then, a chemical reaction
model including five elementary reaction sequences was established.
In elementary reaction E1, the hydrogen of the aldehyde group is captured
by hydroxyl to form the aldehyde radical, which provides the reactant
and accumulates heat for the subsequent reaction. In elementary reaction
E2, the aldehyde radical further reacts to form a carbon-free radical
(R
·
) and CO, which is the main source for CO generation
during coal spontaneous combustion. In elementary reaction E3, the
aldehyde radical is oxidized to a carboxyl radical, providing the
reactant for elementary reaction E4, which is directly related to
CO
2
generation during coal spontaneous combustion. The
thermodynamic parameters of the elementary reactions were further
analyzed and confirmed by quantum chemistry methods. The results are
helpful for further understanding the pathways of CO generation in
the initial stage of coal spontaneous combustion, which provides theoretical
support for prediction of coal spontaneous combustion.