Deciphering the Differential Influence of Organic Additives on Coal Fluidity Development: A First-Principles Investigation

Formation of high-quality coke is essentially controlled by the development of the extended stability of the coal fluid phase during industrial carbonization processes. Stabilization of coal free radicals through hydrogenation leads to this development of coal fluidity. The donatable hydrogens are usually supplied by the donor hydrogen species formed through the thermal decomposition of a coal macromolecular network. In view of the limited reserve of the donor hydrogen species within a coal system, organic additives with characteristic hydrogen-donating ability are conventionally added to the system to maintain the desirable coal fluidity. However, the choice of compounds requires a clear understanding of their chemistry and associated reaction features. In this context, factors controlling hydrogen-donating properties of some organic donor hydrogen compounds are investigated herein within the framework of density functional theory. A mechanistic interpretation of the reaction of the compounds with the coal radical is offered. In addition to structural modification, the influence of the functional group, namely, the phenolic hydroxyl group, on the hydrogen-donating efficiency of the systems is validated through our calculations. The key role of molecular orbitals in facilitating the release of hydrogens from them is also elucidated. Thus, the work features an advanced understanding of a fundamental industrial process combining a detailed electronic description of the systems. The efficiency of a new compound to act as a superior hydrogen donor candidate is identified. The insights obtained are believed to help derive a rational understanding of the systems and structure–property relationships, which, in turn, can inspire future studies to engineer desired compounds with improved properties. The relevance of our findings to practical carbonization processes is also illustrated in the present work.