FTIR and Raman Spectroscopy Characterization of Coking Coals with Diverse Coalification

Abstract

The relationship between several structural parameters and vitrinite reflectance (ranged from 0.72 to 2.14) of coal samples was analyzed with infrared and Raman spectrum, consequently important information of functional groups and molecular structures of samples were obtained. It is indicated in the results that the value of FC increases with the increasing of R₀, while the value of f_a increases with the increasing of R₀ in three independent ranges but decreases sharply at the junctions between regions. Besides, the overall trend of DOC is increasing, while the value of A(CH₂)/A(CH₃) decreases before the point of R₀ = 2.0 and then increases after this value. The value of “C” decreases and the rate of decreasing is gradually decreased. All above variations are attributed to the defunctionalization of oxygen-containing functional groups during coalification. Meanwhile, the difference between peak position of D and G increases with the increasing of R₀ while the value of A_D1/A_G decreases, which is due to the decline in heterocycle compounds and disorder carbon and the increasing size of microcrystallite structure namely the effect of graphitization.