The mechanism of coke formation is discussed in relation to recent knowledge on the nature of reactive groups present in coal. The non-coking coals are characterized by a preponderant number of oxygenated groups such as OH, CO and COOH. The coking coals, on the other hand, have a negligible proportion of reactive groups. Further the OH groups are chelated with CO group and exist mostly as quinhydrone in the non-coking coals and as semi-quinone in the coking coals. It is postulated by the authors here that the mobility of the coal units in the non-coking coals at 300-500ºC is hampered due to condensation reactions involving the reactive groups, whereas in the case of coking coal there are no condensation reactions and the coal units are more free to exhibit fusion and plastic flow
