Stepwise fragmentation of coal by H 2O 2—trifluoroacetic acid oxidation

Abstract

An attempt has been made to elucidate the mechanism of oxidative degradation of coal by H 2O 2 in TFA medium. The ‘oxy-coals’ isolated at different stages of degradation have been characterized, and it has been observed that irrespective of the degree of degradation and dissolution, they are similar in respect of elemental analysis and structural parameters ( f a , f har , O COOH, H C , C CH 3 , ring number). This is in sharp contrast to the oxidation of coal by other common oxidizing agents, and is at variance with the earlier claim of Deno that H 2O 2-TFA treatment selectively oxidizes the aromatic part of coal leaving the nonaromatic structures as organic acids in solution. The observations presented herein and those of Deno are possibly complimentary, and an explanation of the overall reaction leading to stepwise degradation and dissolution is attempted. The implications of the findings with regard to the nature of the coal ‘polymer’ and its depolymerization/fragmentation mechanism are also discussed.