The Catalytic Effect Of Oxygen-Containing Groups In Coal Char Surface On Methane Decompostion Reaction

A majority scholars believe that oxygen-containing groups in coal char surface can accelerate the decomposition of methane, but which has not been confirmed up to now. In this dissertation, the effect of typical oxygen-containing groups in coal char surface on methane was studied using theoretical and experimental methods.The research active position spot of coal tar surface is the foundation of studying the effect mechanism between coal tar and methane. The Mulliken atomic charges, the Fukui function, the distortion density and other microscopic parameters of the models with oxygen-containing group (lactone, acid anhydride, carboxyl group and phenol hydroxyl) in coal char surface were calculated using the quantum chemistry density functional theory method Dmol~3. It can be concluded that the charge of oxygen atom in coal char surface oxygen-containing species changed with the different chemical environment; the Mulliken charge and Fukui function of carbonyl oxygen in lactone and anhydride are larger than oxygen atoms in other chemical environment, which shows that the activity of carbonyl oxygen in lactone and anhydride is the largest, is the active point of chemical reaction. Meanwhile, the reaction mechanism of typical oxygen-containing models in coal chars surface and methane was studied using LST/QST method, the kinetic calculation results show that the carbonyl oxygen in lactone structure is the largest active point to catalyst and activate methane, the activation energy is 94.5kJ/mol, which is good agreement with the experimental result. So it can be concluded that carbonyl oxygen in lactone structure is the most possible active point if the oxygen-containing in coal char surface can catalyst and activate methane decomposition.Based on the calculated results, thermal analysis, Boehm titrate and the XPS experiment were carried out. It can be concluded that methane decomposes at about 750℃under the condition of existing coal char, which shows that coal char can accelerate methane decomposition comparing with methane decomposing at 1000℃under the condition of no catalysis. Meanwhile, coal chars before and after thermal analysis were analyzed by Boehm titrate and the XPS, Boehm titrate results show that content of oxygen-containing group in coal char surface after thermal analysis decreases a little than before analysis; when we analyze the XPS spectrum of coal char before and after thermal analyzing, the standard compounds with similar oxygen-containing groups in coal char surface were determined by XPS, and oxygen-containing groups in coal char surface were separated peaks based on the data of standard compounds, the results show that content of oxygen-containing group in coal char surface after thermal analysis decreases a little than before analysis, and O1s peak has residual, the reason need future analysis and verification.