Contents of O-containing functional groups in coals by ¹³C NMR analysis

The solid state high resolution ¹³C CP/MAS NMR technology was employed to analyze O-containing functional groups in 4 coals. The variation and contents of inactive O-containing functional groups in the coals were obtained in combination with chemical method. The results show that the ¹³C CP/MAS NMR method is effective to obtain the contents of some O-containing functional groups. The contents of carboxyl and carbonyl in the low rank coal are from 0.00 to 1.41 and from 0.45 to 1.91 mol/kg, respectively. Combined with chemical method, the content of ether bond is obtained, which is from 5.33 to 10.54 mol/kg. However, the value of inactive ether bond in the coals is only from 0.04 to 0.13 mol/kg, and the occurrence of the ether bond is predominantly inactive, few of them exists in high rank coal.