A density functional theory study on the decomposition of aliphatic hydrocarbons and cycloalkanes during coal pyrolysis in hydrogen plasma

To get deep understanding of the reaction mechanism of coal pyrolysis in hydrogen plasma, the decomposition reaction pathways of aliphatic hydrocarbons and cycloalkanes, which are two main components in volatiles from coal, were investigated. Methane and cyclohexane were chosen as the model compounds. Density functional theory was employed, and many reaction pathways were involved. Calculations were carried out in Gaussian 09 at the B3LYP/6-31G（d,p） level of the theory. The results indicate that the main pyrolysis products of methane and cyclohexane in hydrogen plasma are both hydrogen and acetylene, and the participation of active hydrogen atoms makes dehydrogenation reactions more favorable. H2 mainly comes from dehydrogenation process, while many reaction pathways are responsible for acetylene formation. During coal pyrolysis in hydrogen plasma, three main components in volatiles like aliphatic hydrocarbons, cycloalkanes and aromatic hydrocarbons lead to the formation of hydrogen and acetylene, but their contributions to products distribution are different.