OBSERVATION OF THE TYPE OF HYDROGEN-BONDS IN COAL BY FTIR

It is hard to distinguish the type of hydrogen bonds formed by hydroxy l groups by normal FTIR methods because of the interference of water i n samples. In this work, a method is proposed for the clear observatio n of the types of hydrogen bonds by FTIR. The method involves the evap oration of water in a vacuum chamber with CaF2 windows (vacuum level, 4 x 10(-3) kPa) followed by in situ scanning of the IR spectrum. Five types of hydrogen bonds were found in coal and its extracts. The hydro xyl groups in coal mainly exist as self-associated OH and OH-N hydroge n-bonded pairs. The thermal stability of these hydrogen bonds was inve stigated by means of in-situ pyrolysis FTIR. It follows the order of O H-ether O > self-associated OH x cyclic OH > OH-N > OH-pi.