Unusual Bands in the Infrared Spectra of Some Oxidized Coals and Coal Chars

Abstract

Nearly fifty years have passed since Sutherland et al. [1] found that coal had a discrete infrared (IR) spectrum and pointed out that the group frequency approach would be useful in obtaining structural information from the absorptions in various regions of the IR spectrum. Great progress has been made since then (Gates cited over 200 papers in his review of the IR spectroscopy of coal over the period 1980–1986 [2]) in studying the 4000–2600 cm⁻¹ region (O-H and C-H stretchings) and also below 2000 cm⁻¹, a region rich in various stretching and deformation modes. The 2600–2000 cm⁻¹ inbetween region has been ignored (and frequently not even shown in many coal spectra) because it is “empty,” i.e., species likely to be found in coals have no fundamentals in that region and overtones and combinations are usually very weak. However, we have observed some new bands in the otherwise empty regions of the spectra of some oxidized coals and coal chars.

Key Words:

• coal
• Argonne Premium Coal Samples
• infrared spectra
• chars
• pyrolysis
• NO
• NO_X