The role of oxygen, nitrogen and argon in the low-temperature oxidation of a dried Alberta coal as studied by dynamic in situ 9 GHz CW-e.p.r.

Abstract The results are reported of a study of the changes in spin concentration and in the e.p.r. spectral parameters for the free-radical and the Mn 2 + HFS resonances observed in dried high-volatile bituminous Alberta coal samples due to low-temperature oxidation in dry air, nitrogen and argon gas flow in the interval 20–300 °C. The temperature-dependence of the free-radical resonance for air treatment differs significantly from that for nitrogen and argon treatment, but the Mn 2 + resonance is independent of the type of gas up to 190 °C. It is concluded that the low-temperature oxidation processes in coal depend critically on the presence of loosely bound water and oxygen.