Atomic scale characterization of oxidation path of active functional groups and formation of by-products in coal regulated by oxygen concentration: Experimental and molecular dynamics simulation

Investigating the influence of environmental factors e.g. O 2 concentration in actual coal mining, on the reaction path of CSC provides the important reference for prevention of coal fire and environmental protection during mining. Therefore, the effects of O 2 concentration on reaction heat and group changes during heating are investigated by TG-DSC and FTIR. The influence mechanism of O 2 concentration on the reaction path and products is investigated at atomic scale by ReaxFF MD. The results indicate that low-oxygen condition suppresses chemical adsorption during oxidation, enhances the self-reaction of groups, thereby facilitating the formation of –CHO and the depletion of –CH 2 /CH 3 , while inhibiting the generation of –OH and –COOH. ReaxFF MD results indicate that high-oxygen facilitates the initial-stage reactions and chemical adsorption of groups. This provides reaction conditions for formation of the by-products e.g. CO and CO 2 .The rapid accumulation of secondary groups results early formation of oxygen-containing intermediates, which promotes C–H and C–C bonds cleavage for alkyl generation. It promotes the condensation reaction of side chain and enhanced the formation of C-O and O–H bonds. In the initial stage, –OH has the highest oxygen sensitivity. In the entire process, the sensitivity of –OH and –COOH is higher than –CHO and –CH 2 /CH 3 .