A modeling for effect of iron compounds on methane formation in the coal

► We model methane formation using graphite, iron compounds and sulfur acid. ► Iron compounds assist formation of dangled bonds in graphite and methane formation. ► The catalytic effect of two-valence iron is twice as high as that of the three-valence one. ► In the course of methane formation, the transformation of iron compounds occurs. Methane formation in the coal was modeled using the mixture of the pure graphite, two- or three-valence iron compounds (pyrite FeS2 and siderite FeCO3, respectively) and the 5% H2SO4 water solution. The identification of iron-containing phases was carried out by means of Mössbauer spectroscopy. Using electron paramagnetic resonance, it is shown that both iron compounds increase the concentration of electron spins in the graphite, i.e. the number of dangle bonds on the carbon atoms, however the effect of siderite is much higher. The studies of methane degassing by means of the ion mass spectrometry have shown that, as a methane formation catalyst, the two-valence siderite is more than twice as effective as the three-valence pyrite. While holding in the mixture with graphite and sulfur acid, the iron compounds undergo phase transformations.